HomeMy WebLinkAbout; Hydromodification Exemption Analysis Select Carlsbad Watersheds; Hydromodification Exemption Analysis Select Carlsbad Watersheds; 2013-06-10HYDROMODIFICATION EXEMPTION
ANALYSES
FOR
SELECT CARLSBAD WATERSHEDS
June 10, 2013
Wayne W. Chang, MS, PE 46548
Chang
Civil Engineering ◦ Hydrology ◦ Hydraulics ◦ Sedimentation
P.O. Box 9496
Rancho Santa Fe, CA 92067
(858) 692-0760
TABLE OF CONTENTS
Executive Summary ...........................................................................................................................i
Introduction ........................................................................................................................................1
Energy Dissipation .............................................................................................................................3
Lagoon Assessments ..........................................................................................................................5
Hydrologic and Hydraulic Analyses ..................................................................................................10
Conclusion .........................................................................................................................................13
Figures................................................................................................................................................15
APPENDICES
A. Buena Vista Creek HEC-RAS Analysis
B. 10-Year Rational Method Analyses
MAP POCKET
Study Area Exhibit
HMP Exemption Exhibit
CD Containing As-Built Plans
City of Carlsbad
Report accepted by:
June 10, 2013
Glen K. Van Peski, Engineering Manager Date
PE# 41204 Exp 3/31/15
i
EXECUTIVE SUMMARY
This Executive Summary provides an initial synopsis for readers that merely want information
on whether a project qualifies for a hydromodification exemption. The synopsis is followed by a
more detailed summary of the hydromodification criteria and report findings.
Synopsis
The City of Carlsbad’s current storm water standards requires Priority Development Projects to
incorporate treatment control best management practices with flow-control requirements to
address hydromodification. Projects may be relieved from this requirement if it meets defined
hydromodification exemption criteria. This report has studied select areas within the city
tributary to Agua Hedionda Lagoon, Batiquitos Lagoon, and Buena Vista Lagoon to determine if
the exemption criteria is met. The HMP Exemption Exhibit in the map pocket at the back of this
report identifies the exempt areas by hatching. If a project is within a hatched area, it qualifies to
be exempt from hydromodification requirements. Projects that qualify for hydromodification
exemption must still satisfy all other storm water standards (i.e.: treatment control best
management practices, low impact development, and source control measures, etc.).
Detailed Summary
The City of Carlsbad (City) adopted their latest updated Standard Urban Stormwater
Management Plan (SUSMP) on January 14, 2011. The SUSMP was in response to additional
requirements associated with a reissuance of the San Diego Regional Water Quality Control
Board’s municipal stormwater permit (Order No. 2007-01). One important requirement was the
adoption of the final Hydromodification Management Plan, dated March 25, 2011 (final HMP).
The final HMP was approved by the San Diego Copermittees and approved by the Regional
Water Quality Control Board by Resolution R9-2010-0066.
According to the SUSMP, development and redevelopment projects are subject to either
Standard Stormwater or the more rigorous Priority Development Project (PDP) requirements.
The City’s “Storm Water Standards Questionnaire E-34” (see Figure 11) is used to determine
whether a project must meet Standard Stormwater or PDP requirements. In general, PDP projects
include new subdivisions with 10 or more dwelling units, commercial/industrial development
greater than an acre, automotive repair shops, restaurants, hillside development, development
impacting Environmentally Sensitive Areas, parking lots, streets, roads, highways, retail gasoline
outlets, projects affecting the Coastal Development Zone, and projects that disturb more than 1
acres. The questionnaire provides specific thresholds under which these new development types
fall within PDP requirements as well as separate redevelopment criteria.
Projects subject to PDP requirements must include treatment control best management practices
(BMPs) and are required to incorporate hydromodification BMPs. Treatment control BMPs filter
and remove pollutants from stormwater and have existed for several years in various forms.
Hydromodification is essentially a new requirement whose purpose is to control post-
development storm water runoff rates, velocities, and durations in order to maintain or reduce
pre-development downstream erosion, sediment pollutant generation, and protect beneficial uses
and stream habitat (an interim hydromodification requirement was in place prior to the current
SUSMP, but was dissimilar to the current requirement in many aspects). Hydromodification
BMPs must accomplish these goals for flows ranging from a fraction of the 2-year event (10, 30,
ii
or 50 percent) to the 10-year event. The goals are generally met by deploying certain BMPs that
store and infiltrate storm runoff such as bioretention basins, vaults, cisterns, flow-through
planters, infiltration facilities, etc.
However, the final HMP outlines potential scenarios where, if certain projects qualify, could be
exempt from satisfying hydromodification requirements (HMP exemptions). It should be noted
that a project exempt from hydromodification is still subject to treatment control and the
Standard Stormwater requirements. To determine HMP status on projects subject to PDP
requirements, applicants are required to complete the HMP (Hydromodification Management
Plan) Applicability Determination (see Figure 12), which identifies the potential exemptions
from hydromodification requirements.
Depending on a project’s location within the city, some of the exemption criteria could require a
project proponent to undertake significant engineering analyses and evaluation of downstream
drainage facilities and conditions. Consequently, the City of Carlsbad’s Land Development
Engineering Division has commissioned this hydromodification exemption study. A focus was
made to look at the three lagoons within the city (Buena Vista, Agua Hedionda, and Batiquitos
Lagoon) and, using the final HMP guidelines, explore applicable HMP exemptions. This study
assesses the lagoons and seven (7) major drainage areas contributing to the lagoons to determine
whether they meet certain hydromodification exemption criteria. HMP exemptions will assist
small developments that may not have the resources to undertake downstream engineering
analyses, but would qualify for a hydromodification exemption. Medium and large developments
will also benefit from this study. The seven major drainage areas are tributary to one of the seven
following storm drain outlets into Buena Vista, Agua Hedionda, or Batiquitos Lagoon (see the
Study Area Exhibits and HMP Exemption Exhibit in the map pocket):
Buena Vista Lagoon
48” and 66” outlets on the east side of Carlsbad Boulevard into the south side of
the lagoon
48” outlet on the west side of Interstate 5 into the south side of the lagoon
66” outlet on the west side of Jefferson Street into the south side of the lagoon
Agua Hedionda Lagoon
18” outlet on the west end of Date Avenue into the north side of the lagoon
84” outlet on the east side of the railroad tracks into the north side of the lagoon
60” outlet near the south end of Marina Drive into the north side of the lagoon
Batiquitos Lagoon
84” outlet on the east side of Carlsbad Boulevard into the north side of the lagoon
Each of these major drainage areas is served by a network of public drainage facilities that outlet
into a lagoon. The majority of the public facilities are underground storm drain systems or paved
streets. Some facilities are also lined (concrete, gunite, etc.) drainage ditches or swales. As long
as a project discharges into a non-erodible drainage network that is continuous to a lagoon outlet,
it is potentially eligible for a hydromodification exemption. A development or redevelopment
project can have several discharge locations, so the exemption only applies to the portion of the
iii
project that meets this criteria. The Study Area Exhibits contain the non-erodible drainage
networks. It is evident from the exhibits that each major drainage area contains a continuously
non-erodible network that serves a majority of the drainage area.
For each of the seven drainage areas, this report covers HMP exemption criteria using Nodes 2,
6, 7, and 8 from the HMP Applicability Determination flow chart (see Figure 12), as appropriate.
This report analyzes each of these nodes for each of the seven drainage areas.
Based on the results of this study, using Node 7 of the HMP exemption criteria, Buena Vista
Lagoon can be characterized as a “stabilized conveyance system” that discharges to an exempt
system (i.e., the Pacific Ocean). Using rational method analyses and as-built research, the
existing storm drain network collecting run-off for all of the Buena Vista Lagoon drainage areas
(Major Drainage Basins 100, 200, and 300 as shown on the Study Area Exhibits) analyzed in this
report have been shown to be adequate to convey the Q10 runoff (Node 8 criteria). Each outlet
structure was observed to ensure they include adequate energy dissipation to address erosion
potential, i.e., the Node 2 criteria was met for each outlet. For details of how these each of these
criteria where satisfied, refer to the Technical Appendices of this study. The select areas draining
to the Buena Vista Lagoon, which are determined to be exempt from HMP are shown in the
HMP Exemption Exhibit.
Although Major Drainage Basin 200 meets several required criteria as discussed in the prior
paragraph, the 48” outlet carrying the flow from the major basin outlets some distance from the
waters edge of Buena Vista Lagoon. Based on a field review by the City Engineer, this
intervening ground is densly vegetated and or naturally armored. The City Engineer found no
evidence of erosion at or near the waters edge of the lagoon. Consequently, this area is identified
as exempt on the HMP Exemption Exhibit.
Using Node 6 of the HMP exemption criteria, Agua Hedionda Lagoon and Batiquitos Lagoon
were evaluated since they are tidally-influenced, having open stabilized connections to the
Pacific Ocean. Certain drainage areas that drain to these lagoons were selected (Major Drainage
Basin 400, 500, 600, and 700 as shown on the Study Area Exhibits). The existing storm drain
network for each drainage area was also evaluated against their ability to carry the Q10. The
storm drain system for each drainage areas has the capacity to carry the Q10. The outlet for each
storm drain system was also observed to ensure they include adequate energy dissipation to
address erosion potential, i.e., the Node 2 criteria was met for each outlet. For details of how
these each of these criteria where satisfied, refer to the Technical Appendices of this study. The
select areas draining to Agua Hedionda Lagoon and Batiquitos Lagoon which are determined to
be exempt from HMP are shown in the HMP Exemption Exhibit.
There are two isolated areas within Major Drainage Basin 600 that direct storm runoff over the
natural ground surface west of the railroad tracks. Since naturally-lined swales prevent a
hydromodification exemption, these areas are not identified as exempt on the HMP Exemption
Exhibit. It will be the responsibility for future development projects in the non-exempt areas
west of the tracks to assess the situation. It is possible that the development will have to include
hydromodification best management practices, or propose drainage improvements that eliminate
the naturally-lined swales in order to qualify for a hydromodification exemption.
1
INTRODUCTION
The City of Carlsbad (City) adopted their latest updated Standard Urban Stormwater
Management Plan (SUSMP) on January 14, 2011. The SUSMP was in response to additional
requirements associated with a reissuance of the San Diego Regional Water Quality Control
Board’s municipal stormwater permit (Order No. 2007-01). One important requirement was the
adoption of the final Hydromodification Management Plan, dated March 25, 2011 (final HMP).
The final HMP was approved by the San Diego Copermittees and approved by the Regional
Water Quality Control Board by Resolution R9-2010-0066.
According to the SUSMP, development and redevelopment projects are subject to either
Standard Stormwater or the more rigorous Priority Development Project (PDP) requirements.
The City’s “Storm Water Standards Questionnaire E-34” (included following the report figures)
is used to determine whether a project must meet Standard Stormwater or PDP requirements. In
general, PDP projects include new subdivisions with 10 or more dwelling units,
commercial/industrial development greater than an acre, automotive repair shops, restaurants,
hillside development, development impacting Environmentally Sensitive Areas, parking lots,
streets, roads, highways, retail gasoline outlets, projects affecting the Coastal Development Zone,
and projects that disturb more than 1 acres. The questionnaire provides specific thresholds under
which these new development types fall within PDP requirements as well as separate
redevelopment criteria.
Projects subject to PDP requirements must include treatment control best management practices
(BMPs) and are required to incorporate hydromodification BMPs. Treatment control BMPs filter
and remove pollutants from stormwater and have existed for several years in various forms.
Hydromodification is essentially a new requirement whose purpose is to control post-
development storm water runoff rates, velocities, and durations in order to maintain or reduce
pre-development downstream erosion, sediment pollutant generation, and protect beneficial uses
and stream habitat (an interim hydromodification requirement was in place prior to the current
SUSMP, but was dissimilar to the current requirement in many aspects). Hydromodification
BMPs must accomplish these goals for flows ranging from a fraction of the 2-year event (10, 30,
or 50 percent) to the 10-year event. The goals are generally met by incorporating site design
measures to balance the use of pervious and impervious areas, and by using BMPs that store and
infiltrate storm runoff such as bioretention basins, vaults, cisterns, flow-through planters,
infiltration facilities, etc.
However, the final HMP outlines potential scenarios where, if certain projects qualify, could be
exempt from satisfying hydromodification requirements (HMP exemptions). The SUSMP
provides for hydromodification exemptions under certain conditions. To determine HMP status
on projects subject to PDP requirements, applicants are required to complete the HMP
(Hydromodification Management Plan) Applicability Determination (see Figure 12), which
identifies the potential exemptions from hydromodification requirements.
Depending on a project’s location within the city, some of the exemption criteria could require a
project proponent to undertake significant engineering analyses and evaluation of downstream
drainage facilities and conditions. Consequently, the City of Carlsbad’s Land Development
Engineering Division has commissioned this hydromodification exemption study. A focus was
2
made to look at the three lagoons within the city (Buena Vista, Agua Hedionda, and Batiquitos
Lagoon) and, using the final HMP guidelines, explore applicable HMP exemptions. This study
assesses the lagoons and seven (7) major drainage areas contributing to the lagoons to determine
whether they meet certain hydromodification exemption criteria. HMP exemptions will assist
small developments that may not have the resources to undertake downstream engineering
analyses, but would qualify for a hydromodification exemption. Medium and large developments
will also benefit from this study. The seven major drainage areas are tributary to one of the seven
following storm drain outlets into Buena Vista, Agua Hedionda, or Batiquitos Lagoon (see the
Study Area Exhibits and HMP Exemption Exhibit in the map pocket):
Buena Vista Lagoon
48” and 66” outlets on the east side of Carlsbad Boulevard into the south side of
the lagoon
48” outlet on the west side of Interstate 5 into the south side of the lagoon
66” outlet on the west side of Jefferson Street into the south side of the lagoon
Agua Hedionda Lagoon
18” outlet on the west end of Date Avenue into the north side of the lagoon
84” outlet on the east side of the railroad tracks into the north side of the lagoon
60” outlet near the south end of Marina Drive into the north side of the lagoon
Batiquitos Lagoon
84” outlet on the east side of Carlsbad Boulevard into the north side of the lagoon
Each of these major drainage areas is served by a network of public drainage facilities that outlet
into a lagoon. The majority of the public facilities are underground storm drain systems or paved
streets. Some facilities are also lined (concrete, gunite, etc.) drainage ditches or swales. As long
as a project discharges into a non-erodible drainage network that is continuous to a lagoon outlet,
it is potentially eligible for a hydromodification exemption. A development or redevelopment
project can have several discharge locations, so the exemption only applies to the portion of the
project that meets this criteria. The Study Area Exhibits contain the non-erodible drainage
networks. It is evident from the exhibits that each major drainage area contains a continuously
non-erodible network that serves a majority of the drainage area.
For each of the seven drainage areas, this report covers Nodes 2, 6, 7, and 8 from the HMP
Applicability Determination flow chart (see Figure 12), as appropriate. The following sections
analyze each of these nodes for each of the seven drainage areas. Nodes 1, 3, and 4 apply to most
new development projects and are project-specific requirements, so they are not analyzed in this
report. It is likely that a redevelopment project could be exempt from hydromodification under
Nodes 3 and 4 if it is not increasing the pre-redevelopment impervious area. Node 5 only applies
to projects within the city that discharge directly to the Pacific Ocean and is not analyzed in this
report. Nodes 9 through 14 are project-specific requirements that are not analyzed in this report.
3
ENERGY DISSIPATION
Node 2 from the HMP Applicability Determination flow chart requires properly designed energy
dissipation for stormwater outfalls to an unlined area. Since the storm drain networks considered
in this report are continuously non-erodible to one of the three lagoons, the energy dissipation to
be studied are at the lagoon outlets. As-built drawings were reviewed and a site visit was
performed to determine the conditions at each outlet. The following describes the findings for
each outlet.
Buena Vista Lagoon 48” and 66” Outlets
These are adjacent reinforced concrete pipe outlets that discharge into the south edge of Buena
Vista Lagoon immediately east of the merge of State Street and Carlsbad Boulevard. During the
site visit, the lagoon water level was at the invert of the 48” outlet and just above the invert of the
66” outlet (see Figure 1 after this report text). Riprap energy dissipation was not observed below
the outlets nor was there evidence of erosion below the outlets (see Figure 2).
Drawing No. 215-9 shows that the invert elevation of the 66” reinforced concrete pipe outlet is at
6.0 feet NGVD 29 (the reference drawings are included on the compact disc in the map pocket).
The 48” outlet is shown on Drawing 153-9, but the plan does not identify the vertical datum.
Based on the site visit, the 48” outlet invert is approximately 6 inches higher than the 66” outlet
invert. Buena Vista Lagoon contains a weir structure near the Pacific Ocean that controls the
water surface in the lagoon. A field survey by Algert Engineering revealed that the top of the
weir structure is at 7.6 feet NAVD 88 or 5.5 feet NGVD 29. Therefore, the water level in the
lagoon will be within at least 6 to 12 inches of the outlets. During most periods, the water level
should be higher than 5.5 feet due to natural sand build-up above the weir crest caused by littoral
processes as well as backwater in the lagoon. Since ponded water is an effective energy
dissipater, the 48” and 66” outlets contain proper energy dissipation. This is further evidenced by
the absence of erosion below the outlets even though they have been in place since at least the
mid-1980’s.
Buena Vista Lagoon 48” Outlet
This 48” reinforced concrete pipe is a Caltrans facility whose outlet discharges towards, but not
directly into, the south edge of Buena Vista Lagoon immediately west of Interstate 5. The as-
built plans (Document No. 40002483) show that the outlet is at elevation 22.0 feet and was
designed with “rock slope protection.” During the site visit, riprap was observed below the 48”
outlet (see Figure 3). The typical riprap diameter was over 12 inches, which is consistent with the
sizing proposed on the design plans. Tall grasses obscured some of the riprap, but the grass
indicates that the energy dissipation is effective. If the riprap was not effective, then eroded earth
would be visible below the outlet rather than grass.
Buena Vista Lagoon 66” Outlet
This 66” reinforced concrete pipe discharges into the south edge of Buena Vista Lagoon
immediately west of Jefferson Street. The as-built plans (Drawing No. 182-10) show that the
outlet invert is at elevation 5.3 feet NGVD 29 and contains ¼-ton riprap. The outlet invert was
just below the lagoon water level (see Figure 4) during the site visit, which is consistent with the
weir-controlled lagoon water level. Riprap was not observed at the outlet during the site visit due
4
to the difficulty in accessing the outlet through the dense vegetation. However, the fact that the
water level will be at or above the outlet invert indicates that this outlet has appropriate energy
dissipation.
Agua Hedionda Lagoon 18” Outlet
This 18” corrugated metal pipe discharges onto a riprap-lined revetment protecting the northeast
bank of Agua Hedionda Lagoon immediately west of the intersection of Date Avenue with
Garfield Street (see Figure 5). Storm runoff flows a short distance down the revetment and into
the lagoon. As-built plans were not available for the outlet, but the average riprap diameter is
larger than the pipe diameter, so it is obvious that riprap at the outlet provides appropriate energy
dissipation from the outlet to the lagoon for the full range of flows in the pipe. In addition, the
tributary drainage area covers approximately 5.2 acres, so the pipe flows will be relatively small.
Agua Hedionda Lagoon 84” Outlet
This 84” reinforced concrete pipe discharges into the north edge of Agua Hedionda Lagoon just
east of the railroad tracks. The engineering plans (Drawing No. 360-5) were as-built in 2006, so
this is a relatively recent system. The plans show that the storm drain system and its grouted
riprap energy dissipater were designed for the 100-year storm flow in accordance with current
engineering criteria. A site visit confirmed that the grouted riprap energy dissipater exists and is
in substantial conformance with the plans (see Figure 6).
Agua Hedionda Lagoon 60” Outlet
This 60” reinforced concrete pipe discharges directly into the north edge of Agua Hedionda
Lagoon just west of Marina Drive. The as-built plans (Drawing No. 152-3) show that the outlet
invert elevation is -1.75 feet NGVD 29. This elevation is lower than mean sea level, so the
lagoon water level will serve as appropriate energy dissipation for the outflow. A site visit
confirmed that the invert is lower than the lagoon water level (see Figure 8).
Batiquitos Lagoon 84” Outlet
This 84” reinforced concrete pipe discharges into the north edge of Batiquitos Lagoon just east
of Carlsbad Boulevard and west of the railroad tracks. The as-built drawings (Drawing No. 337-
9) show that the storm drain system and its energy dissipater (1-ton riprap and concrete sill) were
designed for the 100-year storm flow in accordance with current engineering criteria. A site visit
confirmed that the energy dissipater exists in substantial conformance with the plans (see Figure
9).
Summary
The above information confirms that proper energy dissipation currently exists at each of the
storm drain outlet locations for the seven major drainage areas. The dissipation is provided by
either riprap or the water level in a lagoon. Therefore, each outlet satisfies Node 2 from the HMP
Applicability Determination flow chart.
5
LAGOON ASSESSMENTS
Discharge to Lagoon Area
Node 6 from the HMP Applicability Determination is based on whether a project discharges
directly to a lagoon area. All seven of the major drainage areas discharges to a lagoon. However,
the lagoon must be tidally-influenced to satisfy Node 6. A lagoon is tidally-influenced if it falls
below the mean higher-high water tidal level. Of the three lagoons, Agua Hedionda Lagoon and
Batiquitos Lagoon have permanent openings to the Pacific Ocean, so are tidally-influenced
during and below mean higher-high water. Buena Vista Lagoon is outlet controlled with a weir
above the mean higher-high water tidal level that prevents tidal influence within the lagoon.
Node 6 also requires an assessment of the freshwater/saltwater balance and the resultant effects
on lagoon-system biology. Merkel & Associates, Inc. has performed this assessment for the
outlets to the two tidally-influenced lagoons, as discussed below. Their assessment concludes
that the effects of exempting these outlets from hydromodification associated with lagoon
biology at the four tidally influenced sites are negligible or within acceptable limits. Much of the
evaluation performed by Merkel & Associates, Inc. is based on the firm’s extensive experience
working within all of the Carlsbad lagoons over the past two decades. This work has included
completion of 12 years of biological and physical monitoring within Batiquitos Lagoon from
1997 through 2009, conducting multiyear biological and water quality investigations within
Agua Hedionda Lagoon, as well as eight years of intensive field work from 2000 to 2008 in
Agua Hedionda Lagoon to eradicate the invasive alga Caulerpa taxifolia from the lagoon. In
addition, a site visit was made to each of the outlets in support of the present analysis.
The two fully tidal lagoons within the city of Carlsbad are not particularly susceptible to adverse
effects of changing freshwater/saltwater balances due to broad-scale characteristics of the
lagoons including relatively extensive subtidal basins, well-established channels, and
permanently opened lagoon mouths. For this reason, evaluations of the various drains under the
Node 6 requirement has focused on consideration of the site specific characteristics at the drains
that could potentially result in localized effects. These effects were assessed in the broader
context of lagoon biology and considering other areas within the lagoons with greater freshwater
inflow. Prolonged flows into the two lagoons from Agua Hedionda Creek, San Marcos Creek,
and Encinitas Creek often result in intermittent, seasonally depressed salinities. However,
beyond the localized points of discharge, these creek flows have not resulted in permanent shifts
in biology from the tidally dominated marine communities to freshwater or even brackish
communities. This resistance to community shifts at the mouths of the larger creeks discharging
to the lagoons has been used for contextual reference in assessing the potential risk of a localized
community shift due to potential changes in the freshwater/saltwater balance at each outlet under
consideration.
Agua Hedionda Lagoon 18” Outlet
This 18” corrugated metal pipe discharges onto the riprap-lined shoreline, immediately east of
the ocean inlet to the west (outer lagoon) basin. Storm runoff leaves the pipe above the mean
higher-high water level and therefore discharges onto bare rock, above the upper boundary for
marine species (Figure 5). Below the pipe, the intertidal riprap is occupied by typical marine
species, including barnacles (Chthamalus and Balanus spp.), lined shore crabs (Pachygrapsus
6
crassipes), and various species of algae, primarily Sargassum muticum, a non-native brown alga
common in the basin. The subtidal environment is fully marine (saltwater), with fish species such
as topsmelt (Atherinops affinis) and garibaldi (Hypsypops rubicundus) common around the
riprap at this location. Low nuisance flow from the outlet is minimal, and storm runoff
discharged from the pipe is low (estimated to be 5.9 cfs for a 10-year storm) and is dispersed by
the riprap and quickly mixed into the water column by the strong currents that pass along the
shoreline as part of the diurnal tidal exchange.
The watershed for this discharge is currently 5.19 acres, with a 10-year storm flow volume of
0.35 acre-feet. The watershed is currently built-out, therefore there is no future increase in storm
discharge to be evaluated and no change to the freshwater/saltwater balance will occur.
Agua Hedionda Lagoon 84” Outlet
This 84” pipe discharges into the northwest corner of the central basin (middle lagoon) of Agua
Hedionda Lagoon onto a grouted riprap energy dissipater apron. There is some opportunistic
exotic freshwater vegetation growing in accumulated debris and sediment on the grouted floor of
the dissipater (Cyperus alternifolius and Washingtonia robusta), supported by the perennial low
flow of freshwater from surrounding irrigation runoff (Figure 6). The discharge then flows from
the dissipater into either open water at higher tides or onto unvegetated mudflat at lower tides
(Figure 7). There is no salt marsh vegetation or eelgrass (Zostera marina) present at the
discharge point, although eelgrass occurs within deeper subtidal waters further out in the basin.
The mudflat below the discharge point is littered with rock debris supporting limited marine
growth. Some geosynthetic fabric has become exposed from beneath previously placed
revetment stone. This fabric similarly supports limited marine growth. The mudflat is expected
to supports a community of typical euryhaline infaunal invertebrates adapted to a range of
salinities due to the perennial low flows of freshwater from the outlet that cross the mudflat
under low tide conditions. Given the westerly location of the drain outlet and the well flushed
nature of the central basin of the lagoon, subtidal and water column species are expected to be
typical of fully marine environments.
This region of the lagoon is relatively near to the ocean inlet, is well-flushed by tidal waters, and
is not prone to salinity depression. The basin into which the drain discharges is fairly small at
approximately 19 acres and connects to the inner and outer lagoon basins via a large, fast
flowing main channel located along the southern edge of the basin. Beyond a relatively narrow
intertidal mudflat, the basin slopes steeply to the lagoon bottom. Because of the strong channel
flows, the middle lagoon basin develops a moderate gyre during tidal exchanges thus enhancing
flushing of this basin. Incoming low flows from this drain float as a freshwater lens on top of the
fully marine waters of the basin. More substantial storm flows are expected to generate localized
mixing and depressions in salinity due to the discharge velocities to the tidal waters. Given the
efficiency of tidal circulation in the area of the drain, the depression of salinity is expected to be
short in duration and followed by rapid return of salinity characteristics exhibited lagoon-wide.
Pulsed reductions in salinity are a normal condition in coastal lagoons and the marine life that
occurs in lagoon habitats are well adapted to tolerate much wider variations in salinity that those
resulting from this relatively small contributor to the system. Due to the substantial lagoon scale
and variety of habitats present in the lagoon, motile marine fish and invertebrate species have
7
opportunities to seek refuge from sub-optimal salinity conditions away from the most depressed
salinity environments near the drain. For infaunal organisms, pulsed salinity depression are
typically managed by a shutdown of activities (e.g., closing shells on mollusks, cessation of
water pumping for crustaceans and many annelid worms), or seeking shelter in the mud away
from depressed salinity flows.
The watershed for this discharge is mostly built out. Future build out is estimated to increase the
10-year storm flow volume by up to approximately 3 percent, from 26.14 to 26.95 acre-feet.
Increasing the 10-year storm flow volume by approximately 3 percent would have an
insignificant effect on the freshwater/saltwater balance of the basin, given the large volume of
tidal water that is efficiently exchanged in this area. The resultant effects on lagoon-system
biology would also be insignificant due to the absence of vegetation at the discharge, the
availability of alternative adjacent waters for motile marine species, and the adaptability of
lagoon species to much higher variations in salinity than those resulting from storm flow at this
drain under current or anticipated future conditions.
Agua Hedionda Lagoon 60” Outlet
This 60” reinforced concrete pipe discharges into the east basin of Agua Hedionda Lagoon at an
outlet invert elevation below mean sea level, as discussed above. Therefore storm flows
discharge primarily into the open water, or occasionally onto the concrete apron below the pipe
during extreme low tides (Figure 8). The shoreline surrounding the outlet is armored by small
rocks with very limited marine growth. There is no marsh vegetation or eelgrass immediately at
the outlet, although eelgrass occurs within the subtidal areas beyond the immediate discharge
point and outside of the existing sediment delta extending outward from the outlet. There appears
to be perennial low flow of freshwater from the outlet although it is difficult to discern the nature
and scale of the flows given the subtidal invert of the pipe.
This region of the lagoon is fully tidal, though it experiences infrequent periods of depressed
salinity as a result of its proximity to Agua Hedionda Creek at the head of the lagoon. Localized
depressions in salinity during storm flow from the 60” outlet are well within the salinity range
experienced by most of the east basin of the lagoon and are not as severe as the variability
observed at the mouth of Agua Hedionda Creek. The sessile marine life at the discharge point is
tolerant of variations in salinity due to the chronic low flow of freshwater from the outlet and
periods of depressed salinity from storm events. The motile marine life occurring in the area is
well adapted to rapid, pulsed variations in salinity, but can also make use of alternate regions of
the lagoon closer to the lagoon mouth or in deeper waters to avoid sub-optimal salinity
conditions, when required.
The watershed for this discharge is mostly built out. Future build out could potentially increase
the 10-year storm flow volume by up to approximately 3 percent, from 31.59 to 32.57 acre-feet.
Increasing the 10-year storm flow volume by approximately 3 percent would have an
insignificant effect on the freshwater/saltwater balance of the basin, given the mixing effect of
the tidal exchange and the much larger effect of nearby Agua Hedionda Creek during storm
flows. The resultant effects on lagoon-system biology would also be insignificant, due to the
absence of vegetation at the discharge, the availability of alternative adjacent waters for motile
8
marine species, and the adaptability of lagoon species to much higher variations in salinity than
those resulting from storm flow at this drain.
Batiquitos Lagoon 84” Outlet
This 84” reinforced concrete pipe discharges into the northwest corner of the west basin of
Batiquitos Lagoon, immediately inside the lagoon ocean inlet. After leaving the concrete and
riprap dissipater, stormwater flows into open tidal waters at high tides or onto unvegetated sand
flats at low tide (Figures 9 and 10). There is no marsh vegetation or eelgrass present in the
vicinity of the outlet. The drain perennially discharges low flow freshwater from the surrounding
developments through a small detention/water quality basin. Under some low tide and flow
conditions, the freshwater flow extends fully to the tidal waters of the lagoon while at other times
the flows dissipate into the sand prior to reaching the low tide waterline. As a result, the benthic
invertebrate community in the immediate vicinity of the low flow channel thalweg across the
sand flats are likely adapted to variations in the salinity of the surface flow at low tides. Because
of the shifting sand nature of the discharge environment, most infaunal organisms found here are
motile and have the capacity to retreat to more favorable areas if needed to avoid undesirable
salinity environments. Most organisms also have the capacity to behaviorally adapt to short-term
hyposalinity exposure during low tide periods at the immediate outlet point.
This region of the lagoon is fully tidal and very well mixed due to its proximity to the ocean inlet
and the high flow rates resulting from diurnal tidal exchanges. Storm runoff discharged from the
pipe is relatively low (estimated to be 15.84 acre-feet for a 10-year storm) and is quickly mixed
by the tidal exchange during either an ebb or flood tide condition.
The watershed for this discharge is mostly built out. Future build out is estimated to increase the
10-year storm flow volume by up to approximately 15 percent, from 15.84 to 18.21 acre-feet.
Increasing the 10-year storm flow discharge by approximately 15 percent would have an
insignificant effect on the freshwater/saltwater balance of the basin, given the large volume of
tidal water exchanged in this area and the lack of residence time for storm water flows. The
resultant effects on lagoon-system biology would also be insignificant, due to the absence of
vegetation at the discharge, the availability of alternative adjacent waters for motile marine
species, and the adaptability of lagoon species to much higher variations in salinity than those
resulting from storm flow at this drain.
Finally, the Node 6 criteria requires an energy dissipation system designed to mitigate 100-year
outlet velocities based on a free outfall condition. As mentioned previously, the 18” and 84”
outlets into Agua Hedionda Lagoon and the 84” outlet into Batiquitos Lagoon have sufficient
riprap energy dissipation for the 100-year free outflow. The 60” outlet into Agua Hedionda
Lagoon is below the lagoon water level so this also has sufficient natural energy dissipation.
Stabilized Conveyance to Exempt System
Buena Vista Lagoon is not tidally-influenced so its storm drain outlets do not qualify under Node
6. The weir structure near the lagoon mouth at the Pacific Ocean has a crest elevation of 7.6 feet
NAVD 88 according to a field survey by Algert Engineering. The mean higher-high water level
from the nearest tidal gage at Scripps Pier in La Jolla is 5.14 feet NAVD 88. Since the mean
9
higher-high water is lower than the weir crest, the weir prevents Buena Vista Lagoon from being
tidally-influenced.
Although Buena Vista Lagoon does not qualify for the HMP_ exemption under Node 6, the
lagoon can still qualify under Nodes 7 and 8. Node 7 covers stabilized conveyances to an exempt
system (i.e., to the Pacific Ocean). Node 7 requires that the stabilized conveyance be a
rehabilitated stream system. Buena Vista Lagoon is California’s first ecological reserve and is
owned by the California Department of Fish and Game. Since 1981, the Buena Vista Lagoon
Foundation has conserved and restored the lagoon’s marsh and wetlands and worked at
stabilizing its drainage basin. Therefore, Buena Vista Lagoon is considered to be a rehabilitated
system. Node 7 also requires the conveyance continue uninterrupted to the exempt system, i.e.,
the rehabilitated system cannot discharge to an unlined, non-engineered channel segment prior to
discharge to the exempt system. Buena Vista Lagoon meets this criteria since it connects directly
to the Pacific Ocean from each of the outlets.
Node 8 requires that the conveyance system has capacity to convey the 10-year ultimate
condition flow. Dokken Engineering prepared detailed hydraulic analyses of Buena Vista
Lagoon as part of their February 2008, Interstate 5 North Coast Floodplain Studies. The
hydraulic analyses were performed using the HEC-RAS model based on April 2004 NAVD 88
topographic mapping, as-built information for the existing bridges (NCTD railroad, Carlsbad
Boulevard, and Interstate 5), and FEMA’s 100-year flow rates. The FEMA 100-year flow rates
are greater than the 10-year ultimate condition flow, so the 100-year results will be more
conservative than the 10-year ultimate condition results. Dokken’s existing condition 100-year
HEC-RAS results are included in Appendix A. The results show that the 100-year floodplain is
generally within the lagoon, so the 10-year flow will be conveyed in the lagoon. The results also
indicate that most of the 100-year flow velocities are less than 6 feet per second, which is the
typical threshold for erosive velocities. The only locations with velocities greater than 6 feet per
second are at the Interstate 5 bridge and near the weir. However, these areas contain riprap to
resist the high velocities. Based on Dokken’s detailed hydraulic analysis, Buena Vista Lagoon
satisfies Node 8.
Summary
The four drainage areas tributary to Agua Hedionda Lagoon and Batiquitos Lagoon qualify for
Node 6 from the HMP Applicability Determination flow chart since these lagoons meet the
tidally-influenced criteria. The easterly and westerly drainage areas tributary to and outletting
directly into Buena Vista Lagoon qualify for Nodes 7 and 8 because Buena Vista Lagoon is a
stabilized conveyance to the Pacific Ocean with capacity for the ultimate condition 10-year flow
and not subject to erosion. The City Engineer has determined, based on field review, that the
middle drainage area tributary to Buena Vista Lagoon qualifies for an exemption because the
densly vegetated and/or naturally armored habitat between the storm system outfall and the
waters edge functions as an extension of the stabilized conveyance. The City Engineer found no
evidence of erosion at or near the point where the discharge intersects the waters edge of the
lagoon.
10
HYDROLOGIC AND HYDRAULIC ANALYSES
As mentioned in the Introduction, hydromodification applies to flows up to the 10-year event.
Consequently, the drainage network (storm drain pipes, streets, etc.) within each major drainage
area are required to convey the 10-year flow in order to qualify for an exemption. All of the
available as-built plans for the public storm drain systems in the seven major drainage areas were
obtained and reviewed. Several of the more recent as-built plans list 10- or 100-year flow rates in
the pipes and/or hydraulic grade lines on the storm drain profiles. These systems have been
identified on the Study Area Exhibits and further analyses were not required since the systems
have been designed to convey the 10-year or greater flow rates. Therefore, development within
these areas is exempt from HMP.
Hydrologic and hydraulic analyses have been performed for the remaining systems whose plans
do not contain the flow or hydraulic grade line data. The hydrologic analyses were performed to
determine the ultimate condition 10-year flow rates. The County of San Diego’s 2003 Hydrology
Manual rational method procedure was used for the 10-year hydrologic analyses. The rational
method input parameters are summarized below and the supporting data is included in Appendix
B:
Precipitation: The 10-year, 6- and 24-hour precipitation values are 1.7 and 3.1 inches,
respectively, for the drainage areas tributary to Buena Vista and Agua Hedionda Lagoon.
The 10-year, 6- and 24-hour precipitation values are 1.7 and 2.9 inches, respectively, for the
drainage areas tributary to Batiquitos Lagoon.
Drainage subbasin: The drainage subbasins were delineated from the City’s 2005 2-foot
contour interval topographic mapping, the City’s GIS storm drain network, available as-
built plans, and a site investigation. See the Study Area Exhibits in the map pocket for the
major and subbasin boundaries, rational method node numbers, and subbasin areas.
Hydrologic soil groups: The hydrologic soil groups were determined from the San Diego
County Soils Interpretation Study maps for Encinitas and Rancho Santa Fe. The soil group
in the study area is primarily A with some pockets of C and D.
Runoff coefficients: The runoff coefficients were assigned based on the underlying land
uses and soil groups. The land uses range from undisturbed areas to commercial/industrial
development. The land uses were determined from a 2009 aerial photograph from the City
and 2010 Google Earth aerials as well as a site investigation. For undeveloped areas that
could be subject to development, a developed condition was assumed. Therefore, the
hydrologic analyses essentially model a fully built-out condition. This approach is similar to
what would be done for a storm water master plan.
Flow lengths and elevations: The flow lengths and elevations were obtained from the
topographic mapping and engineering plans.
11
The 10-year rational method analyses were performed using CivilDesign’s San Diego County
Rational Hydrology Program and the results are included in Appendix B. Separate analyses were
performed for the major drainage areas and are labeled as follows:
Buena Vista Lagoon
Major Basin 100 is tributary to the 48” and 66” outlet on the east side of Carlsbad
Boulevard
Major Basin 200 is tributary to the 48” outlet on the west side of Interstate 5
Major Basin 300 is tributary to the 66” outlet on the west side of Jefferson Street
Agua Hedionda Lagoon
Major Basin 400 is tributary to the 60” outlet at the south end of Marina Drive
Major Basin 500 is tributary to the 18” outlet at the west end of Date Avenue
Analyses were not performed for the 84” outlet on the east side of the railroad
tracks because flow rates and hydraulic grade lines were provided on the majority
of the as-built plans.
Batiquitos Lagoon
Analyses were not performed for the 84” outlet on the east side of Carlsbad
Boulevard because flow rates and hydraulic grade lines were provided on the
majority of the as-built plans.
The CivilDesign rational method analyses include pipeflow routines for modeling flow in
circular pipes. The upstream and downstream invert elevations and pipe length are entered in the
model for each storm drain segment. The program then determines the required normal depth
pipe size based on the calculated 10-year flow rate, longitudinal slope, and roughness coefficient.
The pipeflow routines were used to assess the adequacy of the existing pipes. Invert elevations
were selected so that the longitudinal slope from the as-built plans was accurately modeled in the
analyses. The longitudinal slope of each storm drain segment was determined from a review of
all relevant as-built plans. Some storm drain segments contain varying or multiple slopes. In this
case, the flattest slope was used because it will result in the most conservative sizing. A few
segments were missing elevations on the as-built plans. For these segments, the average street
slope was used. The pipe size from the hydraulic analyses were then compared to the size from
the as-built plans to identify pipes with adequate capacity and those with deficiencies.
Since the rational method program determines the minimum required pipe size to convey the 10-
year flow in each specific segment, it is possible that program will show the required size
increasing or decreasing in adjacent segments of the overall storm drain system. For instance, if
the same flow rate is conveyed in two adjacent segments, but the downstream segment has a
steeper longitudinal slope, the results can show that the downstream pipe is smaller. Engineering
design criteria typically does not allow subsequent segments in a storm drain system to be
smaller. However, since the rational method results are merely used as a comparison with the
sizes from the as-built plans, any usual telescoping effects are no relevant.
The pipes have been categorized based on their capacity and identified on the Study Area
Exhibits per their category. The first category represents pipes in which the as-built plans contain
12
flow rate or hydraulic grade line information indicating that the pipes can convey the 10-year
runoff. As mentioned above, analyses were not specifically performed for these systems since
detailed information is contained on the as-built plans. The second category represents pipes in
which the rational method analyses show that the existing size can convey the 10-year flow rate.
The third category represents pipes in which the rational method analyses show that the existing
pipes need to be upsized by at most one pipe size (6 inches) to convey the 10-year flow. The
fourth category represents pipes in which the rational method analyses show that the existing
pipes need to be upsized by more than one pipe size to convey the 10-year flow.
The first and second categories represent no major deficiencies in capacity. The third category
indicates that the existing pipe is slightly undersized. However, if pressure flow and street
capacity are considered, these systems will be capable of conveying the 10-year flows since the
additional flow associated with an at most 6 inch increase in pipe size can be conveyed under
pressure or within the adjacent street. This was confirmed by comparing the 10-year flow rates
with a street flow capacity chart. For a given pipe segment, the street flow capacity chart
indicated that the associated street can convey the required flow. Therefore, the drainage systems
within the first three categories have capacity for the 10-year flow.
Existing pipes under the fourth category require additional review to determine whether the 10-
year flow can be conveyed. Additional review resulted in the following assessment of the storm
drain systems within the fourth category.
Major Basin 100
There are four storm drain segments in Major Basin 100 that fall within the fourth category. The
segments are between rational method nodes 105 to 109, 135 to 136, 137 to 138, and 138 to 141.
The following assesses the pipe and street capacity of each of these four segments.
The existing pipe from nodes 105 to 109 has an 18” diameter with a normal depth capacity of
approximately 10 cubic feet per second (cfs). However, the rational method results show that the
10-year flow rate is 37 cfs, and the pipe size needed to convey 37 cfs varies from 30” to 33”. The
corridor along the street between these nodes has capacity for the additional 27 cfs (37 – 10 = 27
cfs) needed beyond the pipe capacity. Therefore, the combined pipe and street in this area can
convey the 10-year flow.
A similar assessment is made for the other three segments. The existing pipe from nodes 135 to
136 is a 24” reinforced concrete pipe (RCP), while the analyses show that a 33” RCP is needed.
The existing pipe from nodes 137 to 138 is a 36” RCP while the analyses show that a 45” RCP is
needed. The existing pipe from nodes 138 to 141 is a 12” RCP while the analyses show that a
30” RCP is needed. For each of these deficient segments, the associated streets can handle the
additional capacity needs. In addition, the adjacent upstream and downstream pipe segments are
not deficient. Therefore, the overall drainage systems along these nodes can convey the 10-year
flow.
Major Basin 300
There are two storm drain segments in Major Basin 300 that fall within the fourth category. The
segments are between rational method nodes 309 to 316 and nodes 340 to 343. The existing
13
pipes from nodes 309 to 316 are 24” RCPs, while the required pipe varies from 36” to 39”. The
existing pipes from nodes 340 to 343 are 66” RCPs, while the required size varies from 78” to
81”. For both of these areas, the associated streets can handle the additional capacity needs, so
these areas can convey the 10-year flow.
Major Basin 400
There are two storm drain segments in Major Basin 400 that fall within the fourth category. The
segments are between rational method nodes 408 to 409 and 418 to 420. The existing pipe
between nodes 408 and 409 is an 18” RCP, while a 30” RCP is needed. This pipe crosses a sump
in the street. The excess stormwater will pond in the street until it drains through the 18” RCP.
Therefore, the 10-year flow will be detained in this area. In addition, there are no natural streams
in the vicinity that would be subject to HMP requirements.
The existing pipe between nodes 418 and 420 is a 60” RCP that outlets into Agua Hedionda
Lagoon, while the analyses show that a 72” RCP is required. However, a 60” bypass structure
near the upper end of this segment can divert a portion of the runoff to a second outlet that
discharges to a cove connecting to Agua Hedionda Lagoon.The as-built plans (Drawing No. 152-
3) show that the bypass is controlled by stop logs. If the bypass is open, then the pipe capacity
below the bypass will be sufficient for the 10-year flow. The City of Carlsbad’s Utilities
Operations staff has a “Weir Wall Removal Procedure,” so the stop logs will be removed during
high flow events to ensure 10-year flow capacity. Therefore, this area conveys the 10-year runoff
to Agua Hedionda Lagoon.
CONCLUSION
The City of Carlsbad’s final HMP outlines conditions under which a Priority Development
Project can be exempt from hydromodification requirements. The purpose of this study is to
explore HMP exemptions based on the Carlsbad SUSMP and final HMP adopted by the
Regional Water Quality Control Board in January and March 2011, respectively. In particular,
this study examines the criteria necessary for HMP exemptions for 1) tidally-influenced lagoons
and 2) stabilized conveyances to exempt systems.
These analyses have been performed for seven major drainage areas selected by the City of
Carlsbad and are summarized below based on the two primary criteria that were investigated.
Additional criteria must be met in addition to the primary criteria to achieve an exemption. The
additional criteria is also summarized below.
Tidally-Influenced Lagoons
Agua Hedionda Lagoon and Batiquitos Lagoon are tidally-influenced, so the direct outlets into
these lagoons satisfy an exemption criteria (criteria number 6 from Figure 12). Each of outlets
into these two lagoons has proper energy dissipation, so the outlets meet required exemption
criteria number 2. Finally, as-built plans along with hydrologic and hydraulic analyses show that
the main public drainage facilities can convey the 10-year flows to the outlets. In most cases, the
underground storm drain alone has capacity for the 10-year flow. In some cases, the combination
of underground and overland flow is needed to convey the flow. Where overland flow occurs,
14
the flow is primarily conveyed within improved public streets and will not occur over natural
unlined streams. This satisfies the criteria to ensure the 10-year flow does not enter natural areas
subject to erosion prior to reaching the ultimate drainage system outlet.
Stabilized Conveyances
Buena Vista Lagoon is not tidally-influenced, but the outlets into this lagoon meet an exemption
criteria (criteria number 7) because the lagoon is a stabilized conveyance with capacity for the
ultimate 10-year flow. Each of outlets into this lagoon has proper energy dissipation, so the
outlets meet required exemption criteria number 2. Furthermore, the hydrologic and hydraulic
analyses show that the 10-year flow is conveyed by the underground storm drain alone in most
areas, and the combination of the underground storm drain and improved public streets in the
remaining areas.
Future Projects
Based on the findings in this report, future projects within one of the studied drainage areas
qualify for an exemption if their storm runoff is directed to a public drainage facility included in
this report without being conveyed over a natural drainage course.
However, future projects in certain locations within the study area will be required to perform
additional analyses prior to receiving a hydromodification exemption. These exceptions are
outlined below.
The major drainage area tributary to the 84” outlet into Agua Hedionda Lagoon is bisected along
its westerly side by the existing railroad tracks. Storm runoff from two areas west of the tracks
will be directed to naturally-lined swales near the tracks. Since naturally-lined swales prevent a
hydromodification exemption, development west of the tracks may need to replace a natural
swale with a non-erodible conveyance. It will be the responsibility for a future development
project west of the tracks to assess this situation in detail and propose a solution, as needed. The
HMP Exemption Exhibit delineates the two non-exempt areas for reference. Hydrologic analyses
have not been performed for these two areas.
15
Figure 1. Outlet of 48” and 66” RCPs into Buena Vista Lagoon
Figure 2. Downstream of 48” and 66” RCPs showing no Erosion
16
Figure 3. Outlet of Caltrans’ 48”RCP Tributary to Buena Vista Lagoon
Figure 4. Outlet of 66” RCP into Buena Vista Lagoon West of Jefferson Street (left of reeds)
17
Figure 5. Outlet of 18” RCP into Agua Hedionda Lagoon
Figure 6. Outlet of 84” RCP into Agua Hedionda Lagoon
18
Figure 7. Open Water Adjacent to Energy Dissipater at 84” RCP into Agua Hedionda Lagoon
Figure 8. Outlet of 60” RCP into Agua Hedionda Lagoon
19
Figure 9. Outlet of 84” RCP into Batiquitos Lagoon
Figure 10. Sand Flat Below Outlet of 84” RCP into Batiquitos Lagoon
E-34 Page 1 of 3 REV 1/14/11
Development Services
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
INSTRUCTIONS:
To address post-development pollutants that may be generated from development projects, the City requires that new
development and significant redevelopment priority projects incorporate Permanent Storm Water Best Management
Practices (BMP’s) into the project design per the City’s Standard Urban Stormwater Management Plan (SUSMP). To
view the SUSMP, refer to the Engineering Standards (Volume 4, Chapter 2) at www.carlsbadca.gov/standards.
Initially this questionnaire must be completed by the applicant in advance of submitting for a development application
(subdivision, discretionary permits and/or construction permits). The results of the questionnaire determine the level of
storm water standards that must be applied to a proposed development or redevelopment project. Depending on the
outcome, your project will either be subject to ‘Standard Stormwater Requirements’ or be subject to additional criteria
called ‘Priority Development Project Requirements’. Many aspects of project site design are dependent upon the
storm water standards applied to a project.
Your responses to the questionnaire represent an initial assessment of the proposed project conditions and impacts.
City staff has responsibility for making the final assessment after submission of the development application. If staff
determines that the questionnaire was incorrectly filled out and is subject to more stringent storm water standards than
initially assessed by you, this will result in the return of the development application as incomplete. In this case, please
make the changes to the questionnaire and resubmit to the City.
If you are unsure about the meaning of a question or need help in determining how to respond to one or more of the
questions, please seek assistance from Land Development Engineering staff.
A separate completed and signed questionnaire must be submitted for each new development application submission.
Only one completed and signed questionnaire is required when multiple development applications for the same project
are submitted concurrently. In addition to this questionnaire, you must also complete, sign and submit a Project Threat
Assessment Form with construction permits for the project.
Please start by completing Section 1 and follow the instructions. When completed, sign the form at the end and submit
this with your application to the city.
SECTION 1 NEW DEVELOPMENT
Does your project meet one or more of the following criteria: YES NO
1. Housing subdivisions of 10 or more dwelling units. Examples: single family homes, multi-family homes,
condominium and apartments
2. Commercial – greater than 1-acre. Any development other than heavy industry or residential. Examples: hospitals;
laboratories and other medical facilities; educational institutions; recreational facilities; municipal facilities; commercial
nurseries; multi-apartment buildings; car wash facilities; mini-malls and other business complexes; shopping malls;
hotels; office buildings; public warehouses; automotive dealerships; airfields; and other light industrial facilities.
3. Heavy Industrial / Industry- greater than 1 acre. Examples: manufacturing plants, food processing plants, metal
working facilities, printing plants, and fleet storage areas (bus, truck, etc.).
4. Automotive repair shop. A facility categorized in any one of Standard Industrial Classification (SIC) codes 5013,
5014, 5541, 7532-7534, and 7536-7539
5. Restaurants. Any facility that sells prepared foods and drinks for consumption, including stationary lunch counters
and refreshment stands selling prepared foods and drinks for immediate consumption (SIC code 5812), where the
land area for development is greater than 5,000 square feet. Restaurants where land development is less than 5,000
square feet shall meet all SUSMP requirements except for structural treatment BMP and numeric sizing criteria
requirements and hydromodification requirements.
E-34 Page 2 of 3 REV 1/14/11
Development Services
Land Development Engineering
1635 Faraday Avenue
760-602-2750
www.carlsbadca.gov
STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
6. Hillside development. Any development that creates more than 5,000 square feet of impervious surface and is
located in an area with known erosive soil conditions, where the development will grade on any natural slope that is
twenty-five percent (25%) or greater.
7. Environmentally Sensitive Area (ESA)1. All development located within or directly adjacent2 to or discharging
directly3 to an ESA (where discharges from the development or redevelopment will enter receiving waters within the
ESA), which either creates 2,500 square feet or more of impervious surface on a proposed project site or increases
the area of imperviousness of a proposed project site 10% or more of its naturally occurring condition.
8. Parking lot. Area of 5,000 square feet or more, or with 15 or more parking spaces, and potentially exposed to urban
runoff
9. Streets, roads, highways, and freeways. Any paved surface that is 5,000 square feet or greater used for the
transportation of automobiles, trucks, motorcycles, and other vehicles
10. Retail Gasoline Outlets. Serving more than 100 vehicles per day and greater than 5,000 square feet
11. Coastal Development Zone. Any project located within 200 feet of the Pacific Ocean and (1) creates more than
2500 square feet of impervious surface or (2) increases impervious surface on property by more than 10%.
12. More than 1-acre of disturbance. Project results in the disturbance of 1-acre or more of land and is considered a
Pollutant-generating Development Project4.
1 Environmentally Sensitive Areas include but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special Biological Significance by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); water bodies
designated with the RARE beneficial use by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments);
areas designated as preserves or their equivalent under the Multi Species Conservation Program within the Cities and County of San Diego; and any o her equivalent
environmentally sensi ive areas which have been iden ified by the Copermittees.
2 “Directly adjacent” means situated within 200 feet of the Environmentally Sensitive Area.
3 “Discharging directly to” means outflow from a drainage conveyance system that is composed entirely of flows from the subject development or redevelopment site, and
not commingled with flow from adjacent lands.
4 Pollutant-generating Development Projects are those projects that generate pollutants at levels greater than background levels. In general, these include all projects
that contribute to an exceedance to an impaired water body or which create new impervious surfaces greater than 5000 square feet and/or introduce new landscaping
areas that require routine use of fertilizers and pesticides. In most cases linear pathway projects that are for infrequent vehicle use, such as emergency or maintenance
access, or for pedestrian or bicycle use, are not considered Pollutant-generating Development Projects if they are built with pervious surfaces or if they sheet flow to
surrounding pervious surfaces.
INSTRUCTIONS:
Section 1 Results:
If you answered YES to ANY of the questions above, your project is subject to Priority Development Project requirements. Skip Section 2 and
please proceed to Section 3. Check the “meets PRIORITY DEVELOPMENT PROJECT requirements” box in Section 3. Additional storm water
requirements will apply per the SUSMP. If you answered NO to ALL of the questions above, then please proceed to Section 2 and follow the instructions.
E-34 Page 3 of 3 REV 1/14/11
Development Services
Land Development Engineering
1635 Faraday Avenue
760-602-2750
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STORM WATER
STANDARDS
QUESTIONNAIRE
E-34
SECTION 2 SIGNIFICANT REDEVELOPMENT
INSTRUCTIONS: Complete the questions below regarding your project YES NO
1. Project results in the disturbance of 1-acre or more of land and is considered a Pollutant-generating Development
Project *?
INSTRUCTIONS: If you answered NO, please proceed to question 2.
If you answered YES, then you ARE a significant redevelopment and you ARE subject to PRIORITY DEVELOPMENT PROJECT
requirements. Please check the “meets PRIORITY DEVELOPMENT PROJECT requirements” box in Section 3 below.
2. Is the project redeveloping an existing priority project type? (Priority projects are defined in Section 1)
INSTRUCTIONS: If you answered YES, please proceed to question 3.
If you answered NO, then you ARE NOT a significant redevelopment and your project is subject to STANDARD STORMWATER
REQUIREMENTS. Please check the “does not meet PDP requirements” box in Section 3 below.
3. Is the work limited to trenching and resurfacing associated with utility work; resurfacing and reconfiguring surface
parking lots and existing roadways; new sidewalk; bike lane on existing road and/or routine maintenance of damaged
pavement such as pothole repair? Resurfacing/reconfiguring parking lots is where the work does not expose underlying soil
during construction.
INSTRUCTIONS: If you answered NO, then proceed to question 4.
If you answered YES, then you ARE NOT a significant redevelopment and your project is subject to STANDARD STORMWATER
REQUIREMENTS. Please check the “does not meet PDP requirements” box in Section 3 below.
4. Will your redevelopment project create, replace, or add at least 5,000 square feet of impervious surfaces on existing
developed property or will your project be located within 200 feet of the Pacific Ocean and (1) create 2500 square feet or
more of impervious surface or (2) increases impervious surface on the property by more than 10%? Replacement of
existing impervious surfaces includes any activity that is not part of routine maintenance where impervious material(s) are
removed, exposing underlying soil during construction.
INSTRUCTIONS: If you answered YES, you ARE a significant redevelopment, and you ARE subject to PRIORITY DEVELOPMENT
PROJECT requirements. Please check the “meets PRIORITY DEVELOPMENT PROJECT requirements” box in Section 3 below. Review
SUSMP to find out if SUSMP requirements apply to your project envelope or the entire project site.
If you answered NO, then you ARE NOT a significant redevelopment and your project is subject to STANDARD STORMWATER
REQUIREMENTS. Please check the “does not meet PDP requirements” box in Section 3 below.
*for definition see Footnote 4 on page 2
SECTION 3 QUESTIONNAIRE RESULTS
My project meets PRIORITY DEVELOPMENT PROJECT (PDP) requirements and must comply with additional stormwater criteria
per the SUSMP and I understand I must prepare a Storm Water Management Plan for submittal at time of application. I understand
flow control (hydromodification) requirements may apply to my project. Refer to SUSMP for details.
My project does not meet PDP requirements and must only comply with STANDARD STORMWATER REQUIREMENTS per the
SUSMP. As part of these requirements, I will incorporate low impact development strategies throughout my project. Applicant Information and Signature Box This Box for City Use Only
Address: Assessor’s Parcel Number(s):
Applicant Name: Applicant Title:
Applicant Signature:
Date:
City Concurrence: YES NO
By:
Date:
Project ID:
SECTION 2: IDENTIFY POLLUTANTS, BMP SIZING AND SELECTION
30 City of Carlsbad SUSMP – January 14, 2011
FIGURE 2-1. HMP Applicability Determination*
*refer to expanded HMP exemption criteria below for justifications required on each node
APPENDIX A
BUENA VISTA CREEK HEC-RAS ANALYSIS
LEGEND•
•
-
fi!IIA fLOOD,LAIN
PIIOPOII!D fLOODHAIN
-PRCTIYI! PLOW AIII!A
CliO .. 81!CTIOII IIIYall 8TATIOII
IIIOHT 0Yaii8ANK CIIOII IICTION
LifT OVI118AIIK CIIOII IICTION
IIAIII CNAIINIL CIIOia IICTIOII
IIIQHT OYIII8AIIK IIIACH LIIIOTH
LifT OVI!II8AIIK IIIACH LI!NOTH
IIAIII CNAIIIIIL IIIACN LI118TN
__ ,.._. .. ,..A-n-·-·--------
~~9.~~
,.n..-n•~ t,: '&,n::. 0 .... l , ........ .,,
a.UIIIA VIITA LA8001111·1
Cll018 IICTIOII
LOCATI0118>
LEGEND•
PI.A PLOODPLAIII
PIIOPOIID PLOOOPLAIII
( IIIIPPIICTIU I'LOW AIIIA
# CliO .. UCTIOII IIIVIII aTATIOII
llletiT OVIIIaAIIII CliO .... CTIOII
LIPT OYIIIIAIIK 011011 IIOTIOII
IIAIII CIIAIINIL CliO" IICTIOII
IIIIHT OYUIAIIII IIIACH LIIIIITH
LIPT OVIIIIAIIK IIIACH LIIIIITH
~ IIAIII CIIAIIIIIL IIIACH LIIIIITH
H
IIOTII• ·• l•lfloatee ereee eeotle• ... , I• exletl•t ••*I
•OO+GO ''•••• I• PillA z .. e Yl were lleee II ... •l•ntl•• .... ... .......... .. ..... DOKKEN tUIIIA VIITA LAIIOOII/1•1
CliO" .. CTIOII
II N • I N II II ll I N • LOCATIOIII E.\,768:" .::,u 11 .. 1 ,,. • .,, PIIIIUAIIY 1001
.......
Table 4. summary of Discharges
Flooding Source and Location
Agua Hedionda Creek
At Confluence with Buena Creek
2,200 Feet Upstream of Rancho Carlsbad
Drive
Upstream of Calavera creek
At El Camino Real
Beaver Hollow Creek
Approximately 1,200 Feet Downstream of
Beaver Hollow Road
Beeler Creek
At U.S. Geological Survey (USGS) Gage on
Downstream Side of Pomerado Road
Borrego Palm Canyon
At Apex of Alluvial Fan
Box Canyon
At Apex of Alluvial Fan
Broadway Creek
At Mouth
Buena Creek
At Mouth
At Buena Creek Road
Buena Vista creek
Upstream of Interstate Highway 5
At Sunset Drive
At Hacienda Drive
At Confluence with Tributary 1
At Confluence with Tributary 2
At confluence with Tributary 4
At Intersection of Vista Way and Arcadia
Avenue
1Data Not Available
Drainage Area
(Square Miles)
6.3
16.5
17.3
23.8
5.0
5 .5
23.3
5.9
3.8
6.3
1.5
20.8
15.9
9.8
7.7
5.1
4.0
0.2
1 0-Year
1,600
__ 1
__ l
__ 1
700
3,100
850
500
1,880 __ 1
2,000
1,700
1,500
1,490
1,030
860
40
Peak Discharges (cfs)
50-Year 100 Year 500 Year
4,800
__ 1
2,400
7,700
2,600
1,200
3,520 __ 1
5,600
5,100
4,900
3,390
2,280
1,850
100
7,000
7,810
8,080
9,850
4,000
3,600
10,650
3,850
1,600
4,100
1,980
8,500
8,000
7,300
4,290
2,840
2,300
130
15,500
__ 1
__ 1
__ 1
9,200
14,800
4,950
4,200
5,420
19,000
18,000
16,000
5,680
3,730
2, 910
170
HEC-RAS Plan· ExistingBV River· Existing Reach· Buena Vista Profile· Flow1
Reach RlverSta Profile OTotal MinCh El W.S. Elev CritW.S. E.G. Elev E.G. Slope VeiChnl Flow Area Top Width Froude#Chl
(cfs) (ft) (ft) (ft) (ft) (Mt) (ft/s) (sqft) (ft)
Buena Vista 7947 Flow1 8500.00 0.00 15.75 4.12 15.79 0.000038 1.72 5028.66 934.46 0.08
Buena Vista 7865 Flow1 8500.00 ·2.00 15.76 1.50 15.78 0.000016 1.19 7315.54 1205.40 0.05
Buena VIsta 7697 Flow1 8500.00 ·4.00 15.77 0.56 15.78 0.000006 0.79 12049.31 1208.66 0.03
Buena Vista 7483 Flowt 8500.00 1.00 15.76 3.73 15.78 0.000013 0.87 10529.84 1260,07 0.05
Buena VIsta 7282 Flowt 8500.00 1.00 15.76 15.77 0.000010 0.76 12255.38 1415.89 0.04
Buena V"ISta 7136 Flowt 8500.00 0.00 15.76 15.77 0.000007 0.64 14270.92 1554.97 0.03
Buena VIsta 6964 Flow1 8500.00 1.00 15.76 15.77 0.000006 0.59 14985.79 1585.09 0,03
Buena Vista 6803 Flow1 8500.00 0.00 15.76 15.77 0.000004 0.51 17030.76 1610.37 0.03
Buena VISta 6648 Flowt 8500.00 0.00 15.76 15.77 0.000004 0.52 17427.74 1686.39 0.03
Buena Vista 6511 Flow1 8500.00 1.00 15.76 15.77 0.000004 0.51 17746.60 1655.38 0.03
Buena Vista 6381 Flowt 8500.00 0.00 15.76 15.77 0.000003 0.48 19045.38 1608.53 0.02
Buena VIsta 6279 Flowt 8500.00 0.00 15.76 15.77 0.000002 0.42 21452.93 1595.29 0.02
Buena Vista 6168 Flow1 8500.00 0.00 15.76 15.77 0.000002 0.38 22629.76 1547.69 0.02
Buena VISta 6060 Flowt 8500.00 0.00 15.76 15.77 0.000002 0.38 22710.90 1562.11 0.02
Buena VIsta 5939 Flowt 8500.00 0.00 15.76 15.77 0.000002 0.38 22700.15 1561.86 0.02
Buena Vista 5816 Flow1 8500.00 0.00 15.76 15.77 0.000002 0.37 22956.98 1559.09 0.02
Buena VISta 5670 Flow1 8500.00 0.00 15.76 15.76 0.000002 0.38 22445.93 1519.46 0.02
Buena Vista 5522 Flow1 8500.00 0.00 15.76 15.76 0.000002 0.39 21750.33 1489.76 0.02
Buena Vista 5368 Flow1 8500.00 0.00 15.76 1.18 15.76 0.000002 0.41 20945.81 1460.43 0.02
Buena Vasta 5244 Flowt 8500.00 0.00 15.76 1.50 15.76 0.000002 0.48 17839.00 1314.36 0.02
Buena Vista 5089 Flowt 8500.00 0.00 15.76 1.64 15.76 0.000004 0.60 14413.73 1237.75 0.03 -Buena Vasta 4974 Flow1 8500.00 0.00 15.75 2.66 15.76 0.000012 1.04 8721.34 11 14.10 0.05
Buena Vasta 4887 Flow1 8500.00 1.00 15.18 9.13 15.71 0.000567 5.82 1460.17 924.71 0.31
Buena Vasta 4867 Flowt 8500.00 1.00 14.81 9.24 15.61 0.000823 7.18 1184.18 913.65 0.37
Buena VIsta 4700 Bridge
Buena Vista 4607 Flowt 8500.00 0.00 12.95 10.29 14.62 0.002103 10.80 909.32 560.83 0.57
Buena Vasta 4529 Flow1 8500.00 -7.00 13.89 2.28 13.97 0.000066 2.19 3975.31 769.07 0.11
Buena Vista 4400 Flow1 8500.00 ·1.00 13.92 1.75 13.95 0.000024 1.36 6320.95 867.72 0,07
Buena Vasta 4288 Flow1 8500.00 ·2.00 13.93 0.12 13.94 0.000007 0.76 11273.59 1261.72 0.03
Buena Vasta 4110 Flowt 8500.00 -2.00 13.93 13.94 0.000003 0.49 17376.66 1199.97 0.02
Buena Vista 3872 Flowt 8500.00 _ ___:?.00 13.93 13.94 f-0.000003 0.49 18241.63 1359.49 0.02 -----Buena Vista 3623 Fiow1 8500.00 -2.00 13.93 13.94 0.000002 0.42 20622.91 1442.30 0.02
Buena Vista 3420 Flowt 8500.00 ·2.00 13.93 13.94 0.000001 0.36 23988.75 1662.14 0.02
Buena Vista 3149 Flowt 8500.00 ·1.00 13.93 13.94 0.000001 0.33 25674.53 1769.06 0.02
Buena Vista 2862 Flowt 8500.00 ·2.00 13.93 13.94 0.000001 0.32 26544.76 1616.98 O.ot
Buena Vista 2630 Flow1 8500.00 -3.00 13.93 13.94 0.000001 0.32 26648.20 1762.09 O.ot
Buena Vasta 2447 Flowt 8500.00 -2.00 13.93 13.93 0.000002 0.40 22623.41 1745.88 0.02
Buena Vista 2292 Flow1 8500.00 -2.00 13.93 13.93 0.000002 0.42 21576.38 1668.46 0.02
Buena Vista 2123 Flow1 6500.00 ·1.00 13.93 0.22 13.93 0.000002 0.45 20302.66 1695.11 0.02
Buena VISta 2005 Flow1 8500.00 ·1.00 13.93 0.31 13.93 0.000002 0.46 19173.12 1892.59 0.02
Buena Vista 1659 Flow1 8500.00 -1.00 13.93 0.77 13.93 0.000003 0.53 16430.98 1815.90 0.02
Buena Vista 1780 Flowt 8500.00 ·1.00 13.93 0.85 13.93 0.000004 0.55 15549.74 1755.61 0.03
Buena Vista 1661 Flow1 8500.00 ·3.00 13.92 4.36 13.93 0.000012 0.88 10962.95 1737.24 0.05
Buena Vasta 1647 Flow1 8500.00 -3.00 13.82 11.60 13.92 0.000258 4.02 4273.20 1677.12 0.20
Buena Vista 1600 Brid~
Buena Vista 1580 Flow1 8500.00 ·3.00 13.74 11.45 13.86 0.000265 4.17 4020.62 1740.14 o2o
Buena Vista 1311 Flow1 8500.00 -4.00 13.79 0.67 13.80 0.000010 0.93 9126.33 1742.06 0.04
Buena Vista 1078 Flow1 8500.00 ·1.00 13.69 2.92 13.79 0.000076 2.55 3557.91 408.41 0.12
Buena Vasta 1050 Bridge
Buena V"osta 1039 Flowt 8500.00 ·1.00 13.69 2.86 13.78 0.000073 2.45 3601.48 363.33 0.12
Buena Vista 726 Flow1 8500.00 ·1.00 13.73 . 2.55 13.75 0.000011 0.87 10474.23 1667.25 0.04
Buena Vista 397 Flowt 8500.00 0.00 13.42 9.69 13.71 0.000566 5.41 2902.33 1528.37 0.30
Buena Vista 160 Flow1 8500.00 ·1.00 12.00 12.00 13.39 0.002352 10.76 1351.05 566.21 0.59
Buena Vista 0 Flowt 8500.00 2.00 11.19 8.16 11.23 0.000137 1.96 6152.88 1429.65 0.14
)
g
c:
.Q ~ Q) iii
20
1
·51 ,
I ]
Buena Vista Existing Model 3/4/2008
Existing Buena Vista
·10+---~----~----~--~----•• ----~----~--~----~----.---~----~--~----~----.---~----~--~----~---.
0 2000 4000 6000 8000
Main Channel Distance (ft)
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
g
c 0 ~ QJ iii
g
c
.Q ~ iii
0 200
Buena Vista Existing Model 3/4/2008
RS = 7947
400 600
Station (ft)
800 1000
Buena Vista Existing Model 3/4/2008
RS = 7697
.o35--+;------.o3 ----i)>jo(IE .035--,
1200
Legend ____ , __________
EG Flow1
WS Flow1
Grit Flow1
Ground
I neff • Bank Sta
-5+-~--.-~--.-~--.-~--.-~--.-~--.-~--.-~--,
0 200 400 600 800
Station (ft)
1000 1200 1400 1600
g
c 0 ~ QJ
iii
0
Buena Vista Existing Model 3/4/2008
RS = 7865
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 7483
.035-+----.o3 --------;+---.o35 _,
200 400 600 800
Station (ft)
1000 1200 1400 1600
Legend
EG Flow1
WS Flow1
Grit Flow1
Ground
I neff • Bank Sta
Legend
EG Flow1
WS Flow1
Grit Flow1
Ground
I neff • Bank Sta
g
c: 0 ~ > cu w 15l
10j
:J
0
50
g
c: 40
0 ~ > cu w
0
I
Buena Vista Existing Model 3/4/2008
AS= 7282
,_ _____ .03 .035 ___,
I I I I I I
Legend
-----------
EG Flow1
WS Flow1
Ground • Bank Sta
200 800 1000 1200 1400 1600 1800
Station (ft)
Buena Vista Existing Model 3/4/2008
AS= 6964
.035+------.03------~<-.035-~
500 1000
Station (ft)
1500 2000
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
2
g
c: 0 ~ > cu w
g
c: .Q ~ cu w
60 l ro'
50
~
40
30
20
Buena Vista Existing Model 3/4/2008
AS= 7136
~~------.03 .035__,
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
0 200 600 800 1000 1200 1400 1600 1800
Station (ft)
Buena Vista Existing Model 3/4/2008
AS= 6803
~ .035 +-------.03 ----------;~ .035-,
60
50
40
30
20
10
o+-~~~~~~~~~~1~~~~~~~~
0 500 1000
Station (ft)
1500 2000
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
g
c .Q iii > Q)
iD
20
0
0
Buena Vista Existing Model
AS= 6648
3/4/2008
()::!<;~>*-------.03-------*--.035 ----1
,....-,,-----.,--,
500 1000 1500
Station (ft)
Buena Vista Existing Model ·3/4/2008
AS= 6381
-*-----.03------¥ .035----1
500 1000 1500 2000
Station (ft)
2000
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
Legend
······-~-----~----EG Flow1
WS Flow1
Ground • BankSta
2500
3
g
c 0 ~ Q)
iD
g
c 0 ~ Q)
iD
Buena Vista Existing Model
AS=6511
3/4/2008
k.o35+'------.03----~1 ,___ .035--1
?OJ
40
30
0
0
500 1000 1500 2000
Station (ft)
Buena Vista Existing Model 3/4/2008
AS= 6279
E------.03----+--.035__,
500 1000 1500 2000
Station (ft)
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
2500
2500
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
g
c: 0 ~ > Q) iii
g
c: 0 ~ ai iii
0
0
Buena Vista Existing Model 3/4/2008
RS = 6168
-#lE---------.03------___..,+ .035 _, r---7---:--..,
Legend
500 1500
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 5939
500 1000
Station (ft)
1500
EG Flow1
WS Flow1
Ground • Bank Sta
2000
2000
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
4
g
c: 0 ~ Q)
iii
g
c: 0 -~
iii
0
Buena Vista Existing Model 3/4/2008
RS =6060
500 1000 1500
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 5816
035>i<E-------.o3----------;, . 1
0
3
5
2000
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
Legend
EG Flow1
WS Flow1
Ground • BankSta
o+-~--~~~~~~~~~~~~~~~T=~--~--~
0 500 1000
Station (ft)
1500 2000
c 0 ~ Q) jjj
g
c 0 ~ Q)
jjj
50
0
0
Buena Vista Existing Model 3/4/2008
RS = 5670
O::l"*E---------.03-------i~ ·I
0
3
5
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
200 400 600 1000 1200 1400 1600 1800
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 5368
r-------.03 ---------*1 .03~
Legend
·---------------
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
200 400 600 800 1 000 1200 1400 1600 1800
Station (ft)
5
g
c .Q ~ Q) m
g
c 0 ~ Q)
jjj
Buena Vista Existing Model 3/4/2008
RS = 5522
}o3S*-------.o3--------;f.o3~
60 ~
0 200 400 600 800 1000 1200 1400 1600
Station (ft)
Buena Vista Existing Model 3/4/2008
RS =5244
.03 1 .03~
' ' 0 200 400 600 800 1000 1200 1400
Station (ft)
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
1800
1600
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
g
c .Q (ij > Q) w
g
c 0 ~ Q) w
0
0
Buena Vista Existing Model 3/4/2008
AS= 5089
l<E-------.03------1 . 1
0
3
5
200 400 600 800
Station (ft)
Buena Vista Existing Model
AS= 4887
1000 1200
3/4/2008
.035 -----;)~l<r--.03 -~'E------.035 -----i1
200 400 600
Station (ft)
800 1000
Legend
-----------
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
1400
Legend
-------·-···-·-EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
1200
6
g
c 0 ~ Q) w
g
c 0 :; a; w
0 200
Buena Vista Existing Model 3/4/2008
AS = 4974
;-------.03--------c+ .035,
400 600 800
Station (ft)
Buena Vista Existing Model
AS = 4867
1000 1200
3/4/2008
f--.o35--+-.o3 -+;------.035----
501
30
20
101
0 1
0 200 400 600
Station (ft)
800 1000
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
1400
1200
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
g
c .Q cu > Q)
iiJ
Buena Vista Existing Model 3/4/2008
AS= 4700 BA 1-5 Existing Bridge
k--.035--+-.03 -+ .035------;1 so-1
40
30
20
··j
0
0 200
Station (ft)
Buena Vista Existing Model 3/4/2008
AS= 4607
Legend
·-·-·-·~~-
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
1200
1<---.o3s -----,+o~~-----.o3s ------)',
50 ~----~
40
0 200 400 600
Station (ft)
800 1000
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
7
g
c
.Q cu > Q) iiJ
g
c .Q ~ Q) iiJ
Buena Vista Existing Model 3/4/2008
AS= 4700 BA 1-5 Existing Bridge
----+.o:+ .o3s ------~
~L:-e-g-en-d.,--, soJ .035
Jl
30
\ :
20
J
j
10 I
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
0+-~~~~.-~~~ .. ~---.-.-.~~~~.-.-.-.-~
0
0
200 400 600 800
Station (ft)
Buena Vista Existing Model 3/4/2008
AS= 4529
~;--------.03-----+-.035-,
200 400 600
Station (ft)
800 1000
1000
1200
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
g
c 0 ~ Q)
[jj
g
c .Q ~ Q)
[jj
101
Buena Vista Existing Model 3/4/2008
AS= 4400
~-------.03 .035 -~
Legend
·----·-EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
-1 :1+--r -,---,--,--,....,.........--.---,----.---,.-r--r--r--r--r-r--,--,--~-.--,
0
0
200 400 600 800 1000
Station (It)
Buena Vista Existing Model 3/4/2008
AS= 4110
~------.03 .035~
200 400 600 800
Station (It)
1000 1200 1400
1200
1600
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
8
g
c 0 :;
> Q)
[jj
c .Q ~ Q)
[jj
Buena Vista Existing Model 3/4/2008
AS= 4288
70
------.03 +-.035--1 jk o~
60-
50
40
30
20
10
0
-1 0 0 200 400 600 800 1000 1200
Station (It)
Buena Vista Existing Model 3/4/2008
AS =3872
1400
1<--------.03 .035-~
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
1600
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
-10+-~-.-~--.-~--.-~--.-~--.-~--.-~--.-~~
0 200 400 600 800
Station (It)
1000 1200 1400 1600
g
c .Q (ii ~ jjJ
c .Q ~ Q)
jjJ
Buena Vista Existing Model 3/4/2008
RS =3623
~m~~--------.03 :.03~
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
-10~.--~~~----~-.--~-.~--.----.--~-.----.-~-.
0
0
200 400 600 800 1 000 1200 1400 1600 1800
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 3149
;------------.o3--------~~ . I
0
3
5
500 1000
Station (ft)
1500
Legend
·-····-·-·-··-· EG Flow1
WS Flow1
Ground • Bank Sta
2000
9
g
c 0 ~ jjJ
g
c .Q ~ Q)
jjJ
10
0
Buena Vista Existing Model 3/4/2008
AS= 3420
;-----------.03 1-.035 ·~
500 1000 1500
Station (ft)
Buena Vista Existing Model 3/4/2008
AS= 2862
-------.o3---------;+o3~
2000
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
-1 O+~ -,--.--,...-,---,--.--..-.--.--,-.---..---.--.-,---,r--r-r--.---r--r--.--.--....-,
0 500 1000 1500 2000 2500
Station (ft)
g
c: 0 ~ <ll w
g
c: .Q
~ <ll w
Buena Vista Existing Model 3/4/2008
AS= 2630
. ~------.03 -----~ ·I
50 0 0
0
0
3 3
5 5
500 1000 1500
Station (ft)
Buena Vista Existing Model 3/4/2008
AS= 2292
-------.03 .035 --~
500 1000
Station (ft)
1500
Legend
-----------
EG Flow1
WS Flow1
Ground • Bank Sta
2000
Legend
----------------
EG Flow1
WS Flow1
Ground • Bank Sta
2000
10
g
c: .Q
iii > <ll w
Buena Vista Existing Model 3/4/2008
AS= 2447
j . ~'---------.03 -----~l"-.035 ----1
50 ~
40
0
Station (ft)
Buena Vista Existing Model 3/4/2008
AS = 2123
-----.03 + .035 )I 50~ 6 ~
H
40
~
30J
j
rol
':]
·10
0 500 1000 1500 2000
Station (ft)
I
Legend
EG Flow1
WS Flow1
Ground • Bank Sta
2000
2500
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
c 0 ~ > Q) w
g
c .Q
~ Q) w
0
Buena Vista Existing Model 3/4/2008
RS = 2005
~E---------.03 .035--,
500 1000 1500 2000
Station (ft)
Buena Vista Existing Model ·3/4/2008
RS = 1780
-------.03 ------~..--.035_,
Legend
·---~~--
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
2500
Legend
·----------·-····
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff
I Ban~Sta
500 1000 1500 2000 2500
Station (ft)
11
g
c .Q ~ Q) w
g
c .Q iii > Q) w
Buena Vista Existing Model 3/4/2008
RS = 1859
'---------.03 .0351
-s~~~---~~-r~-~~~-r~-~~~-r~-~
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
0 500 1000 1500 2000
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 1681
:<-----.035 +--.03 .035--~)1
0 500 1000
Station {ft)
1500 2000
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
Buena Vista Existing Model 3/4/2008
RS = 1647
Legend
IE-------.035 , . .035 ----~
0
3 ----------
EG Flow1
WS Flow1
Grit Flow1
Ground
I neff • Bank Sta
I I I
0 500 1000 1500 2000
Station (ft)
Buena Vista Existing Model ·3/4/2008
RS = 1600 BR Carlsbad Blvd Bridge
k .035 )l·r .035
301 0 Legend 3 -------------~I EG Flow1
WS Flow1
20 Grit Flow1
g Ground
15 c: I neff 0 ~ • > Bank Sta C1) 10 w
:l
-5
0 500 1000 1500 2000 2500
Station (ft)
g
c: .Q
(ij > C1) w
g
c: 0 ~ > C1) w
12
Buena Vista Existing Model 3/4/2008
RS = 1600 BR Carlsbad Blvd Bridge
j<c---.035 {r .035-----',
0
3
0 500 1000
Station (ft)
Buena Vista Existing Model
RS = 1580
k .035 {r .035
30 0
3
25
20
15
10
5~ ~
01
-5
0 500 1000 1500
Station (ft)
1500
3/4/2008
J !
2000
Legend
EG Flow1
WS Flow1
Grit Flow1
Ground
I neff • Bank Sta
2000
Legend
----------
EG Flow1
WS Flow1
Grit Flow1
Ground
I neff • Bank Sta
2500
g
c: 0 ~ iii
g
c: .Q
iO > Q)
iii
0
Buena Vista Existing Model 3/4/2008
AS=1311
--*-----.03 .035 ____,
500 1000 1500
Station (ft)
Buena Vista Existing Model ·3/4/2008
AS = 1050 BA NCTD AA Bridge
25j~1< --.035 --~: ,....03 "'I<-----.035
~ 20i1~~~~~~~~~--~~~~~~~~--~
10
5
0
Legend
·--·-------
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
2000
Legend
----------------
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • BankSta
-5+1-.--.~-.-~-c-~-.~-.-~-.--~-.~--.-~-.
0 200 400 600 800 1 000 1200 1400 1600 1800
Station (ft)
g
c: 0 ~ > Q)
iii
g
c: 0 ~ > Q)
iii
13
Buena Vista Existing Model 3/4/2008
AS= 1078
25 1
-.035 ---;).;ci<,....03 : .035-----~,
20
15
10
5
0
I
-5l
0 200 400 600 800 1000 1200 1400 1600
Station (ft)
Buena Vista Existing Model 3/4/2008
AS = 1050 BR NCTD AA Bridge
I )I~ .03-+ 25f
.035 I .035
20
15
10
5
~
oJ j
-5
0 200 400 600 800 1000 1200 1400
Station (ft)
1800
,
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
Legend
-----------
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
1600
g
c: .Q ~ > Q)
[iJ
g
c:
0 ~ ~ [iJ
15
10
5
0
-5
0
0
Buena Vista Existing Model 3/4/2008
RS = 1039
;----.035 +-.03 l .035 -------;~
200 400 600 800 1000 1200
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 397
1400
Legend
------~-
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • BankSta
1600
.o5--f.osr--------.035--------»~ r---;--~·
Legend
200 400 600 800
Station (ft)
1000 1200 1400 1600
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
14
g
c: 0 ~
[iJ
c: 0 ~ [iJ
Buena Vista Existing Model 3/4/2008
RS = 726
35{---.o5 .o3 +-.035 -1
30j
25
20
I
0 500 1000 1500
Station (ft)
Buena Vista Existing Model 3/4/2008
RS = 180
k-.o5 -~. k
25l ~I .035
20 '
10
5
0
-5 ' 0 200 400 600 800 1000 1200
Station (ft)
2000
Legend
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • BankSta
Legend
····----------
EG Flow1
WS Flow1
Crit Flow1
Ground
I neff • Bank Sta
1400
c:
.Q -ro iii [ij
0 200
Buena Vista Existing Model 3/4/2008
RS=O
400 600 800
Station (ft)
1000 1200 1400
-
Legend
·-·-·-·~----
EG Flow1
WS Flow1
Crit Flow1
Ground • Bank Sta
1600
15
APPENDIX B
10-YEAR RATIONAL METHOD ANALYSES
10.0
9.0
8.0
7.0
~ 0 .c:: ]i
.c::
6.0
5.0
4.0
3.0
2.0
g 1.0
~0.9
·~o.8
~0 E .7
0.6
0.5
0.4
0.3
0.2
0.1
,..... ....... I' !'-.. ....... .......
1--....... ....... ..... ,, ....... r..... """' ~ ~ ""
......... .......
....... ....... ............ ~ ..... ~ ....
"" ....... "r..... ..... ~
..... ..... .. ""' ~
I' ....... ....... ....... ~ ~ ...
"" ....... .....
......... ~ "" ..... ....... ......
"" ............ ~ .......
" """ "" .......
....... ....... ~
....... . .....
"r--. ...
....... ~ ...........
""" .... ~
~
I
I
I
' 5 6 7 8 9 10 15
I
I
I
I
20 30 40 50
Minutes
Duration
EQUATION
I = 7.44 P6 D-0·645
I = Intensity (in/hr)
p6 = 6-Hour Precipitation (in)
D = Duration (min)
..............
....... ....... t'.. "I'
t'.. ~ I'~ .... ~
....... t'.. ~ I•~ .... t"-. ~I' "" .............. ~ ~'I'
~
~ "" .......
t'..~
~ ....
~
1•1'
..............
t'..,
2 3 4
Hours
I
5 6
Ol ± 0 c: .....
"0 a;
0
6.0 g
5.5 ~
5.0 g
4.5 5'
0
4.0 ~
3.5.!!!..
3.0
2.5
2.0
1.5
1.0
Intensity-Duration Design Chart -Template
Directions for Application:
(1 ) From precipitation maps determine 6 hr and 24 hr amounts
for the selected frequency. These maps are included in the
County Hydrology Manual (10, 50, and 100 yr maps included
in the Design and Procedure Manual).
(2) Adjust 6 hr precipitation (if necessary) so that it is within
the range of 45% to 65% of the 24 hr precipitation (not
applicaple to Desert).
(3) Plot 6 hr precipitation on the right side of the chart.
(4) Draw a line through the point parallel to the plotted lines.
(5) This line is the intensity-duration curve for the location
being analyzed.
Application Form:
(a) Selected frequency ___ year
p
(b) P6 = in. P24 = ___§_ = %(2) --' --·p24 --
(c) Adjusted P6<2l = __ in.
(d) tx = __ min.
(e) I = __ in./hr.
Note: This chart replaces the Intensity-Duration-Frequency
curves used since 1965.
P6 1 1.5t 2 2.5 3 3i51 4 4.5 5 5.5 6
Duration I I I I I I I I I I
5 2.63 3.95 5.27 6.59 7.90 9.22 10.54 11.86 13.17 14.49.;..15.81
7 2.12 3.18 .... ,. .,. ,..r ............ "·" ... ,
10 1.68 2.53 3.37 4.21 5.05 5.90 6.74 7.58 8.42 9.27 10.11
-15 1.30 1.95 2.59 3.243.89 4.54 5.19 5.84..n49 7.13 7.78
20 1.08 1.62 2.15 2.69 3.231 3. 77 4.31 4.85 5.39 ~93 6.46
25 0.93 1.40 1.87 2.33 2.80 3.27 3.73 4.20 4.67 5.13 5.60
30 0.83 1.24 1.66 2.07 2.49 2.90 3.32 3.73 4.15 4.56 4.98
40 0.69 1.03 1.38 1.72 2.07 2.41 2.76 3.10 3.45 3.79 4.13 -50 0.60 0.90 1.19 1.49 1.79 2.09 2.39 2.69 2.98 3.281.3.58 ·-60 0.53 0.80 1.06 1.33 1.59 1 86 2.12 2.39 2.65 2.92 3.18
90 0.41 0.61 0.82 1.02 1.23 1.43 1.63 1.84 2.04 2.25 2.45
120 0.34 10.51 0.68 0.85 '·" ... l.J6 1 .~+1.70 1.87 2.04
150 0.29 0.44 ~.59t?.73 ~0.8L1_.03 1.18 1.32 1.47 1.62 1.76
180 0.26~0.39 0.52 0.65 0.78 0.91 1.04 1.18 1.31 1.44~1.57
240 0.22 0.~ 0.43 0.54 0.65 0.76 0.87 0.98 1.08 1.19 1.30
300 0.19 0.28 0.38 0.47 0.56 0.66 0.75 0.85 0.94 1.03 1.13
360 0.17 0.25 0.33 0.42 0.50 0.58 0.67 0.75 0.84 0.92 1.00
FIGURE ~
10.0
9.0
8.0
7.0
~ 0 .c:: ]i
.c::
6.0
5.0
4.0
3.0
2.0
g 1.0
~0.9
·~o.8
~0 E .7
0.6
0.5
0.4
0.3
0.2
0.1
,..... ....... I' !'-.. ....... .......
1--....... ....... ..... ,, ....... r..... """' ~ ~ ""
......... .......
....... ....... ............ ~ ..... ~ ....
"" ....... "r..... ..... ~
..... ..... .. ""' ~
I' ....... ....... ....... ~ ~ ...
"" ....... .....
......... ~ "" ..... ....... ......
"" ............ ~ .......
" """ "" .......
....... ....... ~
....... . .....
"r--. ...
....... ~ ...........
""" .... ~
~
I
I
I
' 5 6 7 8 9 10 15
I
I
I
I
20 30 40 50
Minutes
Duration
EQUATION
I = 7.44 P6 D-0·645
I = Intensity (in/hr)
p6 = 6-Hour Precipitation (in)
D = Duration (min)
..............
....... ....... t'.. "I'
t'.. ~ I'~ .... ~
....... t'.. ~ I•~ .... t"-. ~I' "" .............. ~ ~'I'
~
~ "" .......
t'..~
~ ....
~
1•1'
..............
t'..,
2 3 4
Hours
I
5 6
Ol ± 0 c: .....
"0 a;
0
6.0 g
5.5 ~
5.0 g
4.5 5'
0
4.0 ~
3.5.!!!..
3.0
2.5
2.0
1.5
1.0
Intensity-Duration Design Chart -Template
Directions for Application:
(1 ) From precipitation maps determine 6 hr and 24 hr amounts
for the selected frequency. These maps are included in the
County Hydrology Manual (10, 50, and 100 yr maps included
in the Design and Procedure Manual).
(2) Adjust 6 hr precipitation (if necessary) so that it is within
the range of 45% to 65% of the 24 hr precipitation (not
applicaple to Desert).
(3) Plot 6 hr precipitation on the right side of the chart.
(4) Draw a line through the point parallel to the plotted lines.
(5) This line is the intensity-duration curve for the location
being analyzed.
Application Form:
(a) Selected frequency ___ year
p
(b) P6 = in. P24 = ___§_ = %(2) --' --·p24 --
(c) Adjusted P6<2l = __ in.
(d) tx = __ min.
(e) I = __ in./hr.
Note: This chart replaces the Intensity-Duration-Frequency
curves used since 1965.
P6 1 1.5t 2 2.5 3 3i51 4 4.5 5 5.5 6
Duration I I I I I I I I I I
5 2.63 3.95 5.27 6.59 7.90 9.22 10.54 11.86 13.17 14.49.;..15.81
7 2.12 3.18 .... ,. .,. ,..r ............ "·" ... ,
10 1.68 2.53 3.37 4.21 5.05 5.90 6.74 7.58 8.42 9.27 10.11
-15 1.30 1.95 2.59 3.243.89 4.54 5.19 5.84..n49 7.13 7.78
20 1.08 1.62 2.15 2.69 3.231 3. 77 4.31 4.85 5.39 ~93 6.46
25 0.93 1.40 1.87 2.33 2.80 3.27 3.73 4.20 4.67 5.13 5.60
30 0.83 1.24 1.66 2.07 2.49 2.90 3.32 3.73 4.15 4.56 4.98
40 0.69 1.03 1.38 1.72 2.07 2.41 2.76 3.10 3.45 3.79 4.13 -50 0.60 0.90 1.19 1.49 1.79 2.09 2.39 2.69 2.98 3.281.3.58 ·-60 0.53 0.80 1.06 1.33 1.59 1 86 2.12 2.39 2.65 2.92 3.18
90 0.41 0.61 0.82 1.02 1.23 1.43 1.63 1.84 2.04 2.25 2.45
120 0.34 10.51 0.68 0.85 '·" ... l.J6 1 .~+1.70 1.87 2.04
150 0.29 0.44 ~.59t?.73 ~0.8L1_.03 1.18 1.32 1.47 1.62 1.76
180 0.26~0.39 0.52 0.65 0.78 0.91 1.04 1.18 1.31 1.44~1.57
240 0.22 0.~ 0.43 0.54 0.65 0.76 0.87 0.98 1.08 1.19 1.30
300 0.19 0.28 0.38 0.47 0.56 0.66 0.75 0.85 0.94 1.03 1.13
360 0.17 0.25 0.33 0.42 0.50 0.58 0.67 0.75 0.84 0.92 1.00
FIGURE ~
I
I .L ~-
t-ss•-a
"i i l l "i
County of San Diego
Hydrology Manual
10 Year Rainfall Event-6 Houn
lsopluvial (inches)
ji ~ ~ .,.. .,..
1-+-+-32~-01
.;, f r;.. 9: 0! "i
I ~ :,!!
,++++++++++++++~++++++++++~~-~1!+4~~~~-H-rl ~~~++++~~~~~~rrT++TTT~~t~~++++++~~-•
"!"'"
I
ID 2j3t
~i z: I
CD I :r .. 't 1 I
County of San Diego
Hydrology Manual
10 Year Rainfall Event-24 Hours
lsopluvial (inches)
San Diego County Hydrology :tv1anual
Date • June 2003
Table 3-1
Section•
Page•
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use Runoff Coefficient "C"
Soil T e
NRCS Elements Coun Elements % Uv1PER. A B
Undisturbed Natural Terrain (Natural) Penn anent Open Space 0* 0.20 0.25
Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32
Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38
Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41
Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45
Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51
Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54
Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58
High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67
High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77
Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77
Commercial/Industrial (G. Com) General Commercial 85 0.80 0.80
Commercial/Industrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84
Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84
General Industrial 95 0.87 0.87
c
0.30
0.36
0.42
0.45
0.48
0.54
0.57
0.60
0.69
0.78
0.78
0.8 1
0.84
0.84
0.87
3
6 of 26
D
0.35
0.41
0.46
0.49
0 52
0.57
0.60
0.63
0.71
0.79
0.79
0.82
0.85
0.85
0.87
*The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff
coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area
is located in Cleveland National Forest).
DU/ A = dwelling units per acre
NRCS =National Resources Conservation Service
3-6
San Diego County Hydrology :Manual
Date: June 2003
Section:
Page:
3
12 of 26
Note that the Initial Time of Concentration should be reflective of the general land-use at the
upstream end of a drainage basin. A single lot with an area oftwo or less acres does not have
a significant effect where the drainage basin area is 20 to 600 acres.
Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in
hydrology studies. Initial Ti values based on average C values for the Land Use Element are
also included. These values can be used in planning and design applications as described
below. Exceptions may be approved by the "Regulating Agency" when submitted with a
detailed study.
Table 3-2
MAXIMUM OVERLAND FLOW LENGTH (LM)
& INITIAL TIME OF CONCENTRATION (Ti)
Element* DU/ .5% 1% 2% 3% 5% 10%
Acre LM Ti LM Ti LM Ti LM Ti LM Ti LM Ti
Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9
LDR 1 50 12.2 70 11.5 85 10.0 100 9.5 100 8.0 100 6.4
LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8
LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6
MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3
MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8
MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5
MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3
HDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5
HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4 100 2.7
N.Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7
G. Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4
O.P./Com 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
General I. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9
*See Table 3-1 for more detailed description
3-12
1-w w u. 0 z
w (.) z ~ (/)
0 w
(/)
0::: ::::> 0 (.)
0::: w i
EXAMPLE:
Given: Watercourse Distance (D) = 70 Feet
Slope (s) = 1.3%
Runoff Coefficient (C) = 0.41
Overland Flow Time (T) = 9.5 Minutes
SOURCE: Airport Drainage, Federal Aviation Administration, 1965
T = 1.8 (1.1 -C) VD
3\fS
20
(/) w 1-::::> z
~ z
w ~
i=
~ 0 ....J u.
0 z :5 0::: w > 0
FIGU R E
Rational Formula -Overland Time of Flow Nomograph 3-3
1
San Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2009 Version 7.8
Rational method hydrology program based on
San Diego County Flood Control Division 2003 hydrology manual
Rational Hydrology Study Date: 12/08/12
------------------------------------------------------------------------
City of Carlsbad
Hydromodification Exemption Study
Major Basin 100
10-Year Flow Rate
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Program License Serial Number 4028
------------------------------------------------------------------------
Rational hydrology study storm event year is 10.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 1.700
24 hour precipitation(inches) = 3.100
P6/P24 = 54.8%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 100.000 to Point/Station 101.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[LOW DENSITY RESIDENTIAL ]
(1.0 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.270
Initial subarea total flow distance = 244.000(Ft.)
Highest elevation = 182.000(Ft.)
Lowest elevation = 162.000(Ft.)
Elevation difference = 20.000(Ft.) Slope = 8.197 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 8.20 %, in a development type of
1.0 DU/A or Less
In Accordance With Figure 3-3
2
Initial Area Time of Concentration = 7.41 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.2700)*( 100.000^.5)/( 8.197^(1/3)]= 7.41
The initial area total distance of 244.00 (Ft.) entered leaves a
remaining distance of 144.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 0.94 minutes
for a distance of 144.00 (Ft.) and a slope of 8.20 %
with an elevation difference of 11.80(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 0.939 Minutes
Tt=[(11.9*0.0273^3)/( 11.80)]^.385= 0.94
Total initial area Ti = 7.41 minutes from Figure 3-3 formula plus
0.94 minutes from the Figure 3-4 formula = 8.35 minutes
Rainfall intensity (I) = 3.218(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.270
Subarea runoff = 0.747(CFS)
Total initial stream area = 0.860(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 101.000 to Point/Station 102.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 162.000(Ft.)
End of street segment elevation = 161.000(Ft.)
Length of street segment = 171.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 2.106(CFS)
Depth of flow = 0.322(Ft.), Average velocity = 1.544(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 11.370(Ft.)
Flow velocity = 1.54(Ft/s)
Travel time = 1.85 min. TC = 10.19 min.
Adding area flow to street
Rainfall intensity (I) = 2.829(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[LOW DENSITY RESIDENTIAL ]
3
(2.0 DU/A or Less )
Impervious value, Ai = 0.200
Sub-Area C Value = 0.340
Rainfall intensity = 2.829(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.324 CA = 1.259
Subarea runoff = 2.814(CFS) for 3.020(Ac.)
Total runoff = 3.562(CFS) Total area = 3.880(Ac.)
Street flow at end of street = 3.562(CFS)
Half street flow at end of street = 3.562(CFS)
Depth of flow = 0.375(Ft.), Average velocity = 1.749(Ft/s)
Flow width (from curb towards crown)= 14.019(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 102.000 to Point/Station 103.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 161.000(Ft.)
End of street segment elevation = 73.000(Ft.)
Length of street segment = 1802.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 15.814(CFS)
Depth of flow = 0.427(Ft.), Average velocity = 5.604(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 16.585(Ft.)
Flow velocity = 5.60(Ft/s)
Travel time = 5.36 min. TC = 15.55 min.
Adding area flow to street
Rainfall intensity (I) = 2.154(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.700
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.300
[COMMERCIAL area type ]
(Neighborhod Commercial )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.769
Rainfall intensity = 2.154(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
4
(Q=KCIA) is C = 0.679 CA = 13.055
Subarea runoff = 24.562(CFS) for 15.340(Ac.)
Total runoff = 28.124(CFS) Total area = 19.220(Ac.)
Street flow at end of street = 28.124(CFS)
Half street flow at end of street = 28.124(CFS)
Depth of flow = 0.500(Ft.), Average velocity = 6.818(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 0.01(Ft.)
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 103.000 to Point/Station 104.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 73.000(Ft.)
Downstream point/station elevation = 42.000(Ft.)
Pipe length = 2380.00(Ft.) Slope = 0.0130 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 28.124(CFS)
Nearest computed pipe diameter = 27.00(In.)
Calculated individual pipe flow = 28.124(CFS)
Normal flow depth in pipe = 18.19(In.)
Flow top width inside pipe = 25.32(In.)
Critical Depth = 22.13(In.)
Pipe flow velocity = 9.87(Ft/s)
Travel time through pipe = 4.02 min.
Time of concentration (TC) = 19.57 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 103.000 to Point/Station 104.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.857(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(Neighborhod Commercial )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.760
Time of concentration = 19.57 min.
Rainfall intensity = 1.857(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.717 CA = 25.907
Subarea runoff = 19.993(CFS) for 16.910(Ac.)
Total runoff = 48.117(CFS) Total area = 36.130(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
5
Process from Point/Station 104.000 to Point/Station 105.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 42.000(Ft.)
Downstream point/station elevation = 39.890(Ft.)
Pipe length = 450.00(Ft.) Slope = 0.0047 Manning's N = 0.013
No. of pipes = 2 Required pipe flow = 48.117(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 24.058(CFS)
Normal flow depth in pipe = 21.38(In.)
Flow top width inside pipe = 27.16(In.)
Critical Depth = 20.04(In.)
Pipe flow velocity = 6.43(Ft/s)
Travel time through pipe = 1.17 min.
Time of concentration (TC) = 20.74 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 104.000 to Point/Station 105.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 36.130(Ac.)
Runoff from this stream = 48.117(CFS)
Time of concentration = 20.74 min.
Rainfall intensity = 1.789(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 106.000 to Point/Station 107.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Initial subarea total flow distance = 249.000(Ft.)
Highest elevation = 86.500(Ft.)
Lowest elevation = 72.000(Ft.)
Elevation difference = 14.500(Ft.) Slope = 5.823 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 90.00 (Ft)
for the top area slope value of 5.82 %, in a development type of
General Commercial
In Accordance With Figure 3-3
Initial Area Time of Concentration = 2.85 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.8000)*( 90.000^.5)/( 5.823^(1/3)]= 2.85
6
The initial area total distance of 249.00 (Ft.) entered leaves a
remaining distance of 159.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 1.16 minutes
for a distance of 159.00 (Ft.) and a slope of 5.82 %
with an elevation difference of 9.26(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 1.156 Minutes
Tt=[(11.9*0.0301^3)/( 9.26)]^.385= 1.16
Total initial area Ti = 2.85 minutes from Figure 3-3 formula plus
1.16 minutes from the Figure 3-4 formula = 4.00 minutes
Calculated TC of 4.004 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 4.479(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.800
Subarea runoff = 4.945(CFS)
Total initial stream area = 1.380(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 107.000 to Point/Station 108.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 72.000(Ft.)
End of street segment elevation = 52.000(Ft.)
Length of street segment = 1260.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 18.830(CFS)
Depth of flow = 0.528(Ft.), Average velocity = 4.050(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 1.41(Ft.)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 18.000(Ft.)
Flow velocity = 4.05(Ft/s)
Travel time = 5.18 min. TC = 9.19 min.
Adding area flow to street
Rainfall intensity (I) = 3.025(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
7
Decimal fraction soil group D = 0.000
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.760
Rainfall intensity = 3.025(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.764 CA = 10.794
Subarea runoff = 27.707(CFS) for 12.750(Ac.)
Total runoff = 32.652(CFS) Total area = 14.130(Ac.)
Street flow at end of street = 32.652(CFS)
Half street flow at end of street = 32.652(CFS)
Depth of flow = 0.634(Ft.), Average velocity = 4.674(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 6.71(Ft.)
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 108.000 to Point/Station 109.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 52.000(Ft.)
Downstream point/station elevation = 48.000(Ft.)
Pipe length = 456.00(Ft.) Slope = 0.0088 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 32.652(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 32.652(CFS)
Normal flow depth in pipe = 21.23(In.)
Flow top width inside pipe = 27.29(In.)
Critical Depth = 23.34(In.)
Pipe flow velocity = 8.78(Ft/s)
Travel time through pipe = 0.87 min.
Time of concentration (TC) = 10.05 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 108.000 to Point/Station 109.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.854(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Time of concentration = 10.05 min.
Rainfall intensity = 2.854(In/Hr) for a 10.0 year storm
8
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.770 CA = 13.010
Subarea runoff = 4.484(CFS) for 2.770(Ac.)
Total runoff = 37.136(CFS) Total area = 16.900(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 109.000 to Point/Station 105.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 48.000(Ft.)
Downstream point/station elevation = 44.000(Ft.)
Pipe length = 490.00(Ft.) Slope = 0.0082 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 37.136(CFS)
Nearest computed pipe diameter = 33.00(In.)
Calculated individual pipe flow = 37.136(CFS)
Normal flow depth in pipe = 21.87(In.)
Flow top width inside pipe = 31.21(In.)
Critical Depth = 24.34(In.)
Pipe flow velocity = 8.89(Ft/s)
Travel time through pipe = 0.92 min.
Time of concentration (TC) = 10.97 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 109.000 to Point/Station 105.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 16.900(Ac.)
Runoff from this stream = 37.136(CFS)
Time of concentration = 10.97 min.
Rainfall intensity = 2.698(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 110.000 to Point/Station 111.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Initial subarea total flow distance = 740.000(Ft.)
Highest elevation = 58.200(Ft.)
Lowest elevation = 44.000(Ft.)
Elevation difference = 14.200(Ft.) Slope = 1.919 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
9
The maximum overland flow distance is 75.00 (Ft)
for the top area slope value of 1.92 %, in a development type of
General Commercial
In Accordance With Figure 3-3
Initial Area Time of Concentration = 3.76 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.8000)*( 75.000^.5)/( 1.919^(1/3)]= 3.76
The initial area total distance of 740.00 (Ft.) entered leaves a
remaining distance of 665.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 5.34 minutes
for a distance of 665.00 (Ft.) and a slope of 1.92 %
with an elevation difference of 12.76(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 5.336 Minutes
Tt=[(11.9*0.1259^3)/( 12.76)]^.385= 5.34
Total initial area Ti = 3.76 minutes from Figure 3-3 formula plus
5.34 minutes from the Figure 3-4 formula = 9.10 minutes
Rainfall intensity (I) = 3.044(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.800
Subarea runoff = 13.395(CFS)
Total initial stream area = 5.500(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 111.000 to Point/Station 112.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 44.000(Ft.)
Downstream point/station elevation = 42.100(Ft.)
Pipe length = 380.00(Ft.) Slope = 0.0050 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 13.395(CFS)
Nearest computed pipe diameter = 24.00(In.)
Calculated individual pipe flow = 13.395(CFS)
Normal flow depth in pipe = 16.80(In.)
Flow top width inside pipe = 21.99(In.)
Critical Depth = 15.81(In.)
Pipe flow velocity = 5.70(Ft/s)
Travel time through pipe = 1.11 min.
Time of concentration (TC) = 10.21 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 111.000 to Point/Station 112.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.826(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
10
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Time of concentration = 10.21 min.
Rainfall intensity = 2.826(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.800 CA = 8.704
Subarea runoff = 11.205(CFS) for 5.380(Ac.)
Total runoff = 24.600(CFS) Total area = 10.880(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 112.000 to Point/Station 105.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 44.000(Ft.)
Downstream point/station elevation = 42.550(Ft.)
Pipe length = 290.00(Ft.) Slope = 0.0050 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 24.600(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 24.600(CFS)
Normal flow depth in pipe = 21.21(In.)
Flow top width inside pipe = 27.31(In.)
Critical Depth = 20.27(In.)
Pipe flow velocity = 6.63(Ft/s)
Travel time through pipe = 0.73 min.
Time of concentration (TC) = 10.94 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 112.000 to Point/Station 105.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 3
Stream flow area = 10.880(Ac.)
Runoff from this stream = 24.600(CFS)
Time of concentration = 10.94 min.
Rainfall intensity = 2.703(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 48.117 20.74 1.789
2 37.136 10.97 2.698
3 24.600 10.94 2.703
Qmax(1) =
1.000 * 1.000 * 48.117) +
0.663 * 1.000 * 37.136) +
0.662 * 1.000 * 24.600) + = 89.027
Qmax(2) =
1.000 * 0.529 * 48.117) +
11
1.000 * 1.000 * 37.136) +
0.998 * 1.000 * 24.600) + = 87.141
Qmax(3) =
1.000 * 0.527 * 48.117) +
1.000 * 0.997 * 37.136) +
1.000 * 1.000 * 24.600) + = 86.997
Total of 3 streams to confluence:
Flow rates before confluence point:
48.117 37.136 24.600
Maximum flow rates at confluence using above data:
89.027 87.141 86.997
Area of streams before confluence:
36.130 16.900 10.880
Results of confluence:
Total flow rate = 89.027(CFS)
Time of concentration = 20.741 min.
Effective stream area after confluence = 63.910(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 105.000 to Point/Station 105.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.789(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Time of concentration = 20.74 min.
Rainfall intensity = 1.789(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.748 CA = 50.877
Subarea runoff = 2.004(CFS) for 4.070(Ac.)
Total runoff = 91.031(CFS) Total area = 67.980(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 105.000 to Point/Station 113.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 44.000(Ft.)
Downstream point/station elevation = 39.770(Ft.)
Pipe length = 900.00(Ft.) Slope = 0.0047 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 91.031(CFS)
Nearest computed pipe diameter = 48.00(In.)
Calculated individual pipe flow = 91.031(CFS)
Normal flow depth in pipe = 36.42(In.)
12
Flow top width inside pipe = 41.07(In.)
Critical Depth = 34.69(In.)
Pipe flow velocity = 8.90(Ft/s)
Travel time through pipe = 1.69 min.
Time of concentration (TC) = 22.43 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 105.000 to Point/Station 113.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.701(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Time of concentration = 22.43 min.
Rainfall intensity = 1.701(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.753 CA = 56.629
Subarea runoff = 5.310(CFS) for 7.190(Ac.)
Total runoff = 96.341(CFS) Total area = 75.170(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 113.000 to Point/Station 114.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 36.000(Ft.)
Downstream point/station elevation = 34.970(Ft.)
Pipe length = 220.00(Ft.) Slope = 0.0047 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 96.341(CFS)
Nearest computed pipe diameter = 48.00(In.)
Calculated individual pipe flow = 96.341(CFS)
Normal flow depth in pipe = 38.53(In.)
Flow top width inside pipe = 38.20(In.)
Critical Depth = 35.70(In.)
Pipe flow velocity = 8.92(Ft/s)
Travel time through pipe = 0.41 min.
Time of concentration (TC) = 22.84 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 113.000 to Point/Station 114.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 75.170(Ac.)
13
Runoff from this stream = 96.341(CFS)
Time of concentration = 22.84 min.
Rainfall intensity = 1.681(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 115.000 to Point/Station 116.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Initial subarea total flow distance = 760.000(Ft.)
Highest elevation = 52.000(Ft.)
Lowest elevation = 43.700(Ft.)
Elevation difference = 8.300(Ft.) Slope = 1.092 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 60.00 (Ft)
for the top area slope value of 1.09 %, in a development type of
General Commercial
In Accordance With Figure 3-3
Initial Area Time of Concentration = 4.06 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.8000)*( 60.000^.5)/( 1.092^(1/3)]= 4.06
The initial area total distance of 760.00 (Ft.) entered leaves a
remaining distance of 700.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 6.90 minutes
for a distance of 700.00 (Ft.) and a slope of 1.09 %
with an elevation difference of 7.64(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 6.896 Minutes
Tt=[(11.9*0.1326^3)/( 7.64)]^.385= 6.90
Total initial area Ti = 4.06 minutes from Figure 3-3 formula plus
6.90 minutes from the Figure 3-4 formula = 10.96 minutes
Rainfall intensity (I) = 2.700(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.800
Subarea runoff = 3.197(CFS)
Total initial stream area = 1.480(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 116.000 to Point/Station 117.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 43.700(Ft.)
End of street segment elevation = 38.000(Ft.)
Length of street segment = 663.000(Ft.)
14
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 8.366(CFS)
Depth of flow = 0.457(Ft.), Average velocity = 2.495(Ft/s)
Note: depth of flow exceeds top of street crown.
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 18.000(Ft.)
Flow velocity = 2.50(Ft/s)
Travel time = 4.43 min. TC = 15.39 min.
Adding area flow to street
Rainfall intensity (I) = 2.169(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Rainfall intensity = 2.169(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.800 CA = 6.208
Subarea runoff = 10.270(CFS) for 6.280(Ac.)
Total runoff = 13.467(CFS) Total area = 7.760(Ac.)
Street flow at end of street = 13.467(CFS)
Half street flow at end of street = 13.467(CFS)
Depth of flow = 0.523(Ft.), Average velocity = 2.959(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 1.16(Ft.)
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 117.000 to Point/Station 118.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 38.000(Ft.)
Downstream point/station elevation = 37.000(Ft.)
Pipe length = 200.00(Ft.) Slope = 0.0050 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 13.467(CFS)
15
Nearest computed pipe diameter = 24.00(In.)
Calculated individual pipe flow = 13.467(CFS)
Normal flow depth in pipe = 16.88(In.)
Flow top width inside pipe = 21.93(In.)
Critical Depth = 15.84(In.)
Pipe flow velocity = 5.71(Ft/s)
Travel time through pipe = 0.58 min.
Time of concentration (TC) = 15.97 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 117.000 to Point/Station 118.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.118(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Time of concentration = 15.97 min.
Rainfall intensity = 2.118(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.800 CA = 11.320
Subarea runoff = 10.506(CFS) for 6.390(Ac.)
Total runoff = 23.973(CFS) Total area = 14.150(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 118.000 to Point/Station 114.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 38.000(Ft.)
Downstream point/station elevation = 35.950(Ft.)
Pipe length = 410.00(Ft.) Slope = 0.0050 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 23.973(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 23.973(CFS)
Normal flow depth in pipe = 20.79(In.)
Flow top width inside pipe = 27.68(In.)
Critical Depth = 19.99(In.)
Pipe flow velocity = 6.60(Ft/s)
Travel time through pipe = 1.04 min.
Time of concentration (TC) = 17.01 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 118.000 to Point/Station 114.000
**** CONFLUENCE OF MINOR STREAMS ****
16
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 14.150(Ac.)
Runoff from this stream = 23.973(CFS)
Time of concentration = 17.01 min.
Rainfall intensity = 2.034(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 96.341 22.84 1.681
2 23.973 17.01 2.034
Qmax(1) =
1.000 * 1.000 * 96.341) +
0.827 * 1.000 * 23.973) + = 116.161
Qmax(2) =
1.000 * 0.745 * 96.341) +
1.000 * 1.000 * 23.973) + = 95.708
Total of 2 streams to confluence:
Flow rates before confluence point:
96.341 23.973
Maximum flow rates at confluence using above data:
116.161 95.708
Area of streams before confluence:
75.170 14.150
Results of confluence:
Total flow rate = 116.161(CFS)
Time of concentration = 22.839 min.
Effective stream area after confluence = 89.320(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 114.000 to Point/Station 119.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 38.000(Ft.)
Downstream point/station elevation = 35.520(Ft.)
Pipe length = 460.00(Ft.) Slope = 0.0054 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 116.161(CFS)
Nearest computed pipe diameter = 51.00(In.)
Calculated individual pipe flow = 116.161(CFS)
Normal flow depth in pipe = 39.19(In.)
Flow top width inside pipe = 43.03(In.)
Critical Depth = 38.61(In.)
Pipe flow velocity = 9.93(Ft/s)
Travel time through pipe = 0.77 min.
Time of concentration (TC) = 23.61 min.
17
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 114.000 to Point/Station 119.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.646(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
The area added to the existing stream causes a
a lower flow rate of Q = 114.515(CFS)
therefore the upstream flow rate of Q = 116.161(CFS) is being used
Time of concentration = 23.61 min.
Rainfall intensity = 1.646(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.762 CA = 69.581
Subarea runoff = 0.000(CFS) for 2.040(Ac.)
Total runoff = 116.161(CFS) Total area = 91.360(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 119.000 to Point/Station 120.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 36.000(Ft.)
Downstream point/station elevation = 33.460(Ft.)
Pipe length = 470.00(Ft.) Slope = 0.0054 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 116.161(CFS)
Nearest computed pipe diameter = 51.00(In.)
Calculated individual pipe flow = 116.161(CFS)
Normal flow depth in pipe = 39.14(In.)
Flow top width inside pipe = 43.09(In.)
Critical Depth = 38.61(In.)
Pipe flow velocity = 9.94(Ft/s)
Travel time through pipe = 0.79 min.
Time of concentration (TC) = 24.40 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 119.000 to Point/Station 120.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.611(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
18
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
The area added to the existing stream causes a
a lower flow rate of Q = 113.134(CFS)
therefore the upstream flow rate of Q = 116.161(CFS) is being used
Time of concentration = 24.40 min.
Rainfall intensity = 1.611(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.762 CA = 70.213
Subarea runoff = 0.000(CFS) for 0.790(Ac.)
Total runoff = 116.161(CFS) Total area = 92.150(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 120.000 to Point/Station 121.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 38.000(Ft.)
Downstream point/station elevation = 23.440(Ft.)
Pipe length = 350.00(Ft.) Slope = 0.0416 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 116.161(CFS)
Nearest computed pipe diameter = 36.00(In.)
Calculated individual pipe flow = 116.161(CFS)
Normal flow depth in pipe = 25.59(In.)
Flow top width inside pipe = 32.64(In.)
Critical depth could not be calculated.
Pipe flow velocity = 21.62(Ft/s)
Travel time through pipe = 0.27 min.
Time of concentration (TC) = 24.67 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 120.000 to Point/Station 121.000
**** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________
The following data inside Main Stream is listed:
In Main Stream number: 1
Stream flow area = 92.150(Ac.)
Runoff from this stream = 116.161(CFS)
Time of concentration = 24.67 min.
Rainfall intensity = 1.600(In/Hr)
Program is now starting with Main Stream No. 2
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 130.000 to Point/Station 131.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
19
Decimal fraction soil group D = 0.000
[LOW DENSITY RESIDENTIAL ]
(1.0 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.270
Initial subarea total flow distance = 290.000(Ft.)
Highest elevation = 183.000(Ft.)
Lowest elevation = 161.000(Ft.)
Elevation difference = 22.000(Ft.) Slope = 7.586 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 7.59 %, in a development type of
1.0 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 7.60 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.2700)*( 100.000^.5)/( 7.586^(1/3)]= 7.60
The initial area total distance of 290.00 (Ft.) entered leaves a
remaining distance of 190.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 1.20 minutes
for a distance of 190.00 (Ft.) and a slope of 7.59 %
with an elevation difference of 14.41(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 1.198 Minutes
Tt=[(11.9*0.0360^3)/( 14.41)]^.385= 1.20
Total initial area Ti = 7.60 minutes from Figure 3-3 formula plus
1.20 minutes from the Figure 3-4 formula = 8.80 minutes
Rainfall intensity (I) = 3.110(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.270
Subarea runoff = 0.983(CFS)
Total initial stream area = 1.170(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 131.000 to Point/Station 132.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 161.000(Ft.)
End of street segment elevation = 86.000(Ft.)
Length of street segment = 2618.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
20
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 6.350(CFS)
Depth of flow = 0.352(Ft.), Average velocity = 3.676(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 12.869(Ft.)
Flow velocity = 3.68(Ft/s)
Travel time = 11.87 min. TC = 20.67 min.
Adding area flow to street
Rainfall intensity (I) = 1.793(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.550
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.450
[LOW DENSITY RESIDENTIAL ]
(2.9 DU/A or Less )
Impervious value, Ai = 0.250
Sub-Area C Value = 0.429
Rainfall intensity = 1.793(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.418 CA = 6.501
Subarea runoff = 10.674(CFS) for 14.400(Ac.)
Total runoff = 11.657(CFS) Total area = 15.570(Ac.)
Street flow at end of street = 11.657(CFS)
Half street flow at end of street = 11.657(CFS)
Depth of flow = 0.422(Ft.), Average velocity = 4.253(Ft/s)
Flow width (from curb towards crown)= 16.340(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 132.000 to Point/Station 133.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 86.000(Ft.)
Downstream point/station elevation = 80.000(Ft.)
Pipe length = 370.00(Ft.) Slope = 0.0162 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 11.657(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 11.657(CFS)
Normal flow depth in pipe = 13.01(In.)
Flow top width inside pipe = 16.12(In.)
Critical Depth = 15.60(In.)
Pipe flow velocity = 8.53(Ft/s)
Travel time through pipe = 0.72 min.
Time of concentration (TC) = 21.39 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 134.000 to Point/Station 133.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.754(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.150
21
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.850
[COMMERCIAL area type ]
(Neighborhod Commercial )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.785
Time of concentration = 21.39 min.
Rainfall intensity = 1.754(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.498 CA = 9.918
Subarea runoff = 5.737(CFS) for 4.350(Ac.)
Total runoff = 17.394(CFS) Total area = 19.920(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 133.000 to Point/Station 135.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 80.000(Ft.)
Downstream point/station elevation = 65.210(Ft.)
Pipe length = 850.00(Ft.) Slope = 0.0174 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 17.394(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 17.394(CFS)
Normal flow depth in pipe = 14.63(In.)
Flow top width inside pipe = 19.31(In.)
Critical Depth = 18.29(In.)
Pipe flow velocity = 9.72(Ft/s)
Travel time through pipe = 1.46 min.
Time of concentration (TC) = 22.85 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 133.000 to Point/Station 135.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.681(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(14.5 DU/A or Less )
Impervious value, Ai = 0.500
Sub-Area C Value = 0.550
Time of concentration = 22.85 min.
Rainfall intensity = 1.681(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.521 CA = 18.773
Subarea runoff = 14.160(CFS) for 16.100(Ac.)
Total runoff = 31.553(CFS) Total area = 36.020(Ac.)
22
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 135.000 to Point/Station 136.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 61.000(Ft.)
Downstream point/station elevation = 58.640(Ft.)
Pipe length = 550.00(Ft.) Slope = 0.0043 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 31.553(CFS)
Nearest computed pipe diameter = 33.00(In.)
Calculated individual pipe flow = 31.553(CFS)
Normal flow depth in pipe = 24.73(In.)
Flow top width inside pipe = 28.61(In.)
Critical Depth = 22.40(In.)
Pipe flow velocity = 6.61(Ft/s)
Travel time through pipe = 1.39 min.
Time of concentration (TC) = 24.24 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 135.000 to Point/Station 136.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.618(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 24.24 min.
Rainfall intensity = 1.618(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.501 CA = 35.136
Subarea runoff = 25.301(CFS) for 34.090(Ac.)
Total runoff = 56.855(CFS) Total area = 70.110(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 136.000 to Point/Station 137.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 58.000(Ft.)
Downstream point/station elevation = 41.370(Ft.)
Pipe length = 660.00(Ft.) Slope = 0.0252 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 56.855(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 56.855(CFS)
Normal flow depth in pipe = 21.70(In.)
23
Flow top width inside pipe = 26.84(In.)
Critical Depth = 28.43(In.)
Pipe flow velocity = 14.95(Ft/s)
Travel time through pipe = 0.74 min.
Time of concentration (TC) = 24.97 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 136.000 to Point/Station 137.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.587(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(14.5 DU/A or Less )
Impervious value, Ai = 0.500
Sub-Area C Value = 0.550
Time of concentration = 24.97 min.
Rainfall intensity = 1.587(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.519 CA = 57.603
Subarea runoff = 34.575(CFS) for 40.850(Ac.)
Total runoff = 91.430(CFS) Total area = 110.960(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 137.000 to Point/Station 138.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 42.000(Ft.)
Downstream point/station elevation = 38.960(Ft.)
Pipe length = 400.00(Ft.) Slope = 0.0076 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 91.430(CFS)
Nearest computed pipe diameter = 45.00(In.)
Calculated individual pipe flow = 91.430(CFS)
Normal flow depth in pipe = 32.39(In.)
Flow top width inside pipe = 40.42(In.)
Critical Depth = 35.26(In.)
Pipe flow velocity = 10.75(Ft/s)
Travel time through pipe = 0.62 min.
Time of concentration (TC) = 25.59 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 137.000 to Point/Station 138.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 2 in normal stream number 1
Stream flow area = 110.960(Ac.)
24
Runoff from this stream = 91.430(CFS)
Time of concentration = 25.59 min.
Rainfall intensity = 1.562(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 139.000 to Point/Station 140.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Initial subarea total flow distance = 350.000(Ft.)
Highest elevation = 51.000(Ft.)
Lowest elevation = 49.000(Ft.)
Elevation difference = 2.000(Ft.) Slope = 0.571 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 50.00 (Ft)
for the top area slope value of 0.57 %, in a development type of
General Commercial
In Accordance With Figure 3-3
Initial Area Time of Concentration = 4.60 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.8000)*( 50.000^.5)/( 0.571^(1/3)]= 4.60
The initial area total distance of 350.00 (Ft.) entered leaves a
remaining distance of 300.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 4.61 minutes
for a distance of 300.00 (Ft.) and a slope of 0.57 %
with an elevation difference of 1.71(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 4.610 Minutes
Tt=[(11.9*0.0568^3)/( 1.71)]^.385= 4.61
Total initial area Ti = 4.60 minutes from Figure 3-3 formula plus
4.61 minutes from the Figure 3-4 formula = 9.21 minutes
Rainfall intensity (I) = 3.020(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.800
Subarea runoff = 2.996(CFS)
Total initial stream area = 1.240(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 140.000 to Point/Station 141.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 49.000(Ft.)
End of street segment elevation = 41.000(Ft.)
Length of street segment = 941.000(Ft.)
25
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 10.559(CFS)
Depth of flow = 0.486(Ft.), Average velocity = 2.728(Ft/s)
Note: depth of flow exceeds top of street crown.
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 18.000(Ft.)
Flow velocity = 2.73(Ft/s)
Travel time = 5.75 min. TC = 14.96 min.
Adding area flow to street
Rainfall intensity (I) = 2.209(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(General Commercial )
Impervious value, Ai = 0.850
Sub-Area C Value = 0.800
Rainfall intensity = 2.209(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.800 CA = 8.168
Subarea runoff = 15.047(CFS) for 8.970(Ac.)
Total runoff = 18.042(CFS) Total area = 10.210(Ac.)
Street flow at end of street = 18.042(CFS)
Half street flow at end of street = 18.042(CFS)
Depth of flow = 0.578(Ft.), Average velocity = 3.178(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 3.90(Ft.)
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 141.000 to Point/Station 138.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 41.000(Ft.)
Downstream point/station elevation = 39.670(Ft.)
Pipe length = 555.00(Ft.) Slope = 0.0024 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 18.042(CFS)
26
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 18.042(CFS)
Normal flow depth in pipe = 22.22(In.)
Flow top width inside pipe = 26.30(In.)
Critical Depth = 17.27(In.)
Pipe flow velocity = 4.63(Ft/s)
Travel time through pipe = 2.00 min.
Time of concentration (TC) = 16.96 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 141.000 to Point/Station 138.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 2 in normal stream number 2
Stream flow area = 10.210(Ac.)
Runoff from this stream = 18.042(CFS)
Time of concentration = 16.96 min.
Rainfall intensity = 2.037(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 91.430 25.59 1.562
2 18.042 16.96 2.037
Qmax(1) =
1.000 * 1.000 * 91.430) +
0.767 * 1.000 * 18.042) + = 105.266
Qmax(2) =
1.000 * 0.663 * 91.430) +
1.000 * 1.000 * 18.042) + = 78.625
Total of 2 streams to confluence:
Flow rates before confluence point:
91.430 18.042
Maximum flow rates at confluence using above data:
105.266 78.625
Area of streams before confluence:
110.960 10.210
Results of confluence:
Total flow rate = 105.266(CFS)
Time of concentration = 25.594 min.
Effective stream area after confluence = 121.170(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 138.000 to Point/Station 121.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 48.000(Ft.)
27
Downstream point/station elevation = 26.170(Ft.)
Pipe length = 740.00(Ft.) Slope = 0.0295 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 105.266(CFS)
Nearest computed pipe diameter = 36.00(In.)
Calculated individual pipe flow = 105.266(CFS)
Normal flow depth in pipe = 27.19(In.)
Flow top width inside pipe = 30.96(In.)
Critical depth could not be calculated.
Pipe flow velocity = 18.39(Ft/s)
Travel time through pipe = 0.67 min.
Time of concentration (TC) = 26.27 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 138.000 to Point/Station 121.000
**** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________
The following data inside Main Stream is listed:
In Main Stream number: 2
Stream flow area = 121.170(Ac.)
Runoff from this stream = 105.266(CFS)
Time of concentration = 26.27 min.
Rainfall intensity = 1.536(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 116.161 24.67 1.600
2 105.266 26.27 1.536
Qmax(1) =
1.000 * 1.000 * 116.161) +
1.000 * 0.939 * 105.266) + = 215.025
Qmax(2) =
0.960 * 1.000 * 116.161) +
1.000 * 1.000 * 105.266) + = 216.820
Total of 2 main streams to confluence:
Flow rates before confluence point:
116.161 105.266
Maximum flow rates at confluence using above data:
215.025 216.820
Area of streams before confluence:
92.150 121.170
Results of confluence:
Total flow rate = 216.820(CFS)
Time of concentration = 26.265 min.
Effective stream area after confluence = 213.320(Ac.)
28
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 121.000 to Point/Station 121.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.536(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.760
The area added to the existing stream causes a
a lower flow rate of Q = 212.041(CFS)
therefore the upstream flow rate of Q = 216.820(CFS) is being used
Time of concentration = 26.27 min.
Rainfall intensity = 1.536(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.639 CA = 138.006
Subarea runoff = 0.000(CFS) for 2.660(Ac.)
Total runoff = 216.820(CFS) Total area = 215.980(Ac.)
End of computations, total study area = 215.980 (Ac.)
1
San Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2009 Version 7.8
Rational method hydrology program based on
San Diego County Flood Control Division 2003 hydrology manual
Rational Hydrology Study Date: 12/08/12
------------------------------------------------------------------------
City of Carlsbad
Hydromodification Exemption Study
Major Basin 200
10-Year Flow Rate
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Program License Serial Number 4028
------------------------------------------------------------------------
Rational hydrology study storm event year is 10.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 1.700
24 hour precipitation(inches) = 3.100
P6/P24 = 54.8%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 200.000 to Point/Station 201.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(Office Professional )
Impervious value, Ai = 0.900
Sub-Area C Value = 0.830
Initial subarea total flow distance = 740.000(Ft.)
Highest elevation = 95.000(Ft.)
Lowest elevation = 88.000(Ft.)
Elevation difference = 7.000(Ft.) Slope = 0.946 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 60.00 (Ft)
for the top area slope value of 0.95 %, in a development type of
Office Professional
In Accordance With Figure 3-3
2
Initial Area Time of Concentration = 3.83 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.8300)*( 60.000^.5)/( 0.946^(1/3)]= 3.83
The initial area total distance of 740.00 (Ft.) entered leaves a
remaining distance of 680.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 7.13 minutes
for a distance of 680.00 (Ft.) and a slope of 0.95 %
with an elevation difference of 6.43(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 7.127 Minutes
Tt=[(11.9*0.1288^3)/( 6.43)]^.385= 7.13
Total initial area Ti = 3.83 minutes from Figure 3-3 formula plus
7.13 minutes from the Figure 3-4 formula = 10.96 minutes
Rainfall intensity (I) = 2.700(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.830
Subarea runoff = 7.529(CFS)
Total initial stream area = 3.360(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 201.000 to Point/Station 202.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 88.000(Ft.)
Downstream point elevation = 84.100(Ft.)
Channel length thru subarea = 692.000(Ft.)
Channel base width = 3.000(Ft.)
Slope or 'Z' of left channel bank = 4.000
Slope or 'Z' of right channel bank = 4.000
Estimated mean flow rate at midpoint of channel = 9.490(CFS)
Manning's 'N' = 0.040
Maximum depth of channel = 3.000(Ft.)
Flow(q) thru subarea = 9.490(CFS)
Depth of flow = 0.825(Ft.), Average velocity = 1.827(Ft/s)
Channel flow top width = 9.598(Ft.)
Flow Velocity = 1.83(Ft/s)
Travel time = 6.31 min.
Time of concentration = 17.28 min.
Critical depth = 0.531(Ft.)
Adding area flow to channel
Rainfall intensity (I) = 2.013(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(Office Professional )
Impervious value, Ai = 0.900
Sub-Area C Value = 0.830
Rainfall intensity = 2.013(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.830 CA = 5.652
3
Subarea runoff = 3.850(CFS) for 3.450(Ac.)
Total runoff = 11.379(CFS) Total area = 6.810(Ac.)
Depth of flow = 0.900(Ft.), Average velocity = 1.917(Ft/s)
Critical depth = 0.586(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 201.000 to Point/Station 202.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 6.810(Ac.)
Runoff from this stream = 11.379(CFS)
Time of concentration = 17.28 min.
Rainfall intensity = 2.013(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 203.000 to Point/Station 204.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 0.500
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.500
[MEDIUM DENSITY RESIDENTIAL ]
(4.3 DU/A or Less )
Impervious value, Ai = 0.300
Sub-Area C Value = 0.465
Initial subarea total flow distance = 950.000(Ft.)
Highest elevation = 167.000(Ft.)
Lowest elevation = 130.000(Ft.)
Elevation difference = 37.000(Ft.) Slope = 3.895 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 95.00 (Ft)
for the top area slope value of 3.90 %, in a development type of
4.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 7.08 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4650)*( 95.000^.5)/( 3.895^(1/3)]= 7.08
The initial area total distance of 950.00 (Ft.) entered leaves a
remaining distance of 855.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 4.93 minutes
for a distance of 855.00 (Ft.) and a slope of 3.90 %
with an elevation difference of 33.30(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 4.930 Minutes
Tt=[(11.9*0.1619^3)/( 33.30)]^.385= 4.93
Total initial area Ti = 7.08 minutes from Figure 3-3 formula plus
4.93 minutes from the Figure 3-4 formula = 12.01 minutes
Rainfall intensity (I) = 2.545(In/Hr) for a 10.0 year storm
4
Effective runoff coefficient used for area (Q=KCIA) is C = 0.465
Subarea runoff = 1.988(CFS)
Total initial stream area = 1.680(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 204.000 to Point/Station 205.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 130.000(Ft.)
End of street segment elevation = 86.000(Ft.)
Length of street segment = 875.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 4.708(CFS)
Depth of flow = 0.299(Ft.), Average velocity = 4.250(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 10.180(Ft.)
Flow velocity = 4.25(Ft/s)
Travel time = 3.43 min. TC = 15.44 min.
Adding area flow to street
Rainfall intensity (I) = 2.164(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.100
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.900
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.561
Rainfall intensity = 2.164(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.536 CA = 3.395
Subarea runoff = 5.360(CFS) for 4.660(Ac.)
Total runoff = 7.349(CFS) Total area = 6.340(Ac.)
Street flow at end of street = 7.349(CFS)
Half street flow at end of street = 7.349(CFS)
Depth of flow = 0.339(Ft.), Average velocity = 4.717(Ft/s)
Flow width (from curb towards crown)= 12.193(Ft.)
5
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 205.000 to Point/Station 205.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.164(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.150
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.850
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.556
Time of concentration = 15.44 min.
Rainfall intensity = 2.164(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.549 CA = 9.395
Subarea runoff = 12.983(CFS) for 10.780(Ac.)
Total runoff = 20.332(CFS) Total area = 17.120(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 205.000 to Point/Station 205.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.164(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(Office Professional )
Impervious value, Ai = 0.900
Sub-Area C Value = 0.830
Time of concentration = 15.44 min.
Rainfall intensity = 2.164(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.558 CA = 9.859
Subarea runoff = 1.006(CFS) for 0.560(Ac.)
Total runoff = 21.338(CFS) Total area = 17.680(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 205.000 to Point/Station 202.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 86.000(Ft.)
Downstream point/station elevation = 84.100(Ft.)
Pipe length = 170.00(Ft.) Slope = 0.0112 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 21.338(CFS)
Nearest computed pipe diameter = 24.00(In.)
Calculated individual pipe flow = 21.338(CFS)
6
Normal flow depth in pipe = 17.67(In.)
Flow top width inside pipe = 21.15(In.)
Critical Depth = 19.84(In.)
Pipe flow velocity = 8.61(Ft/s)
Travel time through pipe = 0.33 min.
Time of concentration (TC) = 15.77 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 205.000 to Point/Station 202.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 17.680(Ac.)
Runoff from this stream = 21.338(CFS)
Time of concentration = 15.77 min.
Rainfall intensity = 2.135(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 11.379 17.28 2.013
2 21.338 15.77 2.135
Qmax(1) =
1.000 * 1.000 * 11.379) +
0.943 * 1.000 * 21.338) + = 31.499
Qmax(2) =
1.000 * 0.913 * 11.379) +
1.000 * 1.000 * 21.338) + = 31.726
Total of 2 streams to confluence:
Flow rates before confluence point:
11.379 21.338
Maximum flow rates at confluence using above data:
31.499 31.726
Area of streams before confluence:
6.810 17.680
Results of confluence:
Total flow rate = 31.726(CFS)
Time of concentration = 15.771 min.
Effective stream area after confluence = 24.490(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 202.000 to Point/Station 206.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 84.100(Ft.)
Downstream point/station elevation = 82.900(Ft.)
Pipe length = 240.00(Ft.) Slope = 0.0050 Manning's N = 0.013
7
No. of pipes = 1 Required pipe flow = 31.726(CFS)
Nearest computed pipe diameter = 33.00(In.)
Calculated individual pipe flow = 31.726(CFS)
Normal flow depth in pipe = 23.34(In.)
Flow top width inside pipe = 30.03(In.)
Critical Depth = 22.48(In.)
Pipe flow velocity = 7.07(Ft/s)
Travel time through pipe = 0.57 min.
Time of concentration (TC) = 16.34 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 202.000 to Point/Station 206.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.087(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(Office Professional )
Impervious value, Ai = 0.900
Sub-Area C Value = 0.830
Time of concentration = 16.34 min.
Rainfall intensity = 2.087(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.640 CA = 16.167
Subarea runoff = 2.015(CFS) for 0.790(Ac.)
Total runoff = 33.741(CFS) Total area = 25.280(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 202.000 to Point/Station 206.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.087(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.200
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.800
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.552
Time of concentration = 16.34 min.
Rainfall intensity = 2.087(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.617 CA = 20.948
Subarea runoff = 9.976(CFS) for 8.660(Ac.)
Total runoff = 43.717(CFS) Total area = 33.940(Ac.)
8
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 206.000 to Point/Station 207.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 82.900(Ft.)
Downstream point/station elevation = 71.380(Ft.)
Pipe length = 758.00(Ft.) Slope = 0.0152 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 43.717(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 43.717(CFS)
Normal flow depth in pipe = 21.52(In.)
Flow top width inside pipe = 27.02(In.)
Critical Depth = 26.44(In.)
Pipe flow velocity = 11.59(Ft/s)
Travel time through pipe = 1.09 min.
Time of concentration (TC) = 17.43 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 206.000 to Point/Station 207.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.002(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[COMMERCIAL area type ]
(Office Professional )
Impervious value, Ai = 0.900
Sub-Area C Value = 0.830
Time of concentration = 17.43 min.
Rainfall intensity = 2.002(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.648 CA = 25.695
Subarea runoff = 7.720(CFS) for 5.720(Ac.)
Total runoff = 51.437(CFS) Total area = 39.660(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 207.000 to Point/Station 207.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.002(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.450
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.550
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
9
Sub-Area C Value = 0.529
Time of concentration = 17.43 min.
Rainfall intensity = 2.002(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.604 CA = 38.181
Subarea runoff = 24.994(CFS) for 23.580(Ac.)
Total runoff = 76.431(CFS) Total area = 63.240(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 207.000 to Point/Station 208.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 70.000(Ft.)
Downstream point/station elevation = 39.000(Ft.)
Pipe length = 1320.00(Ft.) Slope = 0.0235 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 76.431(CFS)
Nearest computed pipe diameter = 33.00(In.)
Calculated individual pipe flow = 76.431(CFS)
Normal flow depth in pipe = 25.50(In.)
Flow top width inside pipe = 27.66(In.)
Critical depth could not be calculated.
Pipe flow velocity = 15.52(Ft/s)
Travel time through pipe = 1.42 min.
Time of concentration (TC) = 18.85 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 207.000 to Point/Station 208.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.903(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(14.5 DU/A or Less )
Impervious value, Ai = 0.500
Sub-Area C Value = 0.550
Time of concentration = 18.85 min.
Rainfall intensity = 1.903(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.596 CA = 43.851
Subarea runoff = 7.033(CFS) for 10.310(Ac.)
Total runoff = 83.465(CFS) Total area = 73.550(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 208.000 to Point/Station 209.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
10
Upstream point/station elevation = 39.000(Ft.)
Downstream point/station elevation = 30.110(Ft.)
Pipe length = 440.00(Ft.) Slope = 0.0202 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 83.465(CFS)
Nearest computed pipe diameter = 36.00(In.)
Calculated individual pipe flow = 83.465(CFS)
Normal flow depth in pipe = 26.20(In.)
Flow top width inside pipe = 32.04(In.)
Critical Depth = 33.61(In.)
Pipe flow velocity = 15.13(Ft/s)
Travel time through pipe = 0.48 min.
Time of concentration (TC) = 19.33 min.
End of computations, total study area = 73.550 (Ac.)
1
San Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2009 Version 7.8
Rational method hydrology program based on
San Diego County Flood Control Division 2003 hydrology manual
Rational Hydrology Study Date: 12/08/12
------------------------------------------------------------------------
City of Carlsbad
Hydromodification Exemption Study
Major Basin 300
10-Year Flow Rate
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Program License Serial Number 4028
------------------------------------------------------------------------
Rational hydrology study storm event year is 10.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 1.700
24 hour precipitation(inches) = 3.100
P6/P24 = 54.8%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 300.000 to Point/Station 301.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Initial subarea total flow distance = 280.000(Ft.)
Highest elevation = 341.000(Ft.)
Lowest elevation = 329.000(Ft.)
Elevation difference = 12.000(Ft.) Slope = 4.286 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 4.29 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
2
Initial Area Time of Concentration = 6.87 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4800)*( 100.000^.5)/( 4.286^(1/3)]= 6.87
The initial area total distance of 280.00 (Ft.) entered leaves a
remaining distance of 180.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 1.43 minutes
for a distance of 180.00 (Ft.) and a slope of 4.29 %
with an elevation difference of 7.71(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 1.432 Minutes
Tt=[(11.9*0.0341^3)/( 7.71)]^.385= 1.43
Total initial area Ti = 6.87 minutes from Figure 3-3 formula plus
1.43 minutes from the Figure 3-4 formula = 8.30 minutes
Rainfall intensity (I) = 3.230(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.480
Subarea runoff = 2.139(CFS)
Total initial stream area = 1.380(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 301.000 to Point/Station 302.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 329.000(Ft.)
Downstream point/station elevation = 327.200(Ft.)
Pipe length = 360.00(Ft.) Slope = 0.0050 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.139(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 2.139(CFS)
Normal flow depth in pipe = 8.50(In.)
Flow top width inside pipe = 10.91(In.)
Critical Depth = 7.50(In.)
Pipe flow velocity = 3.60(Ft/s)
Travel time through pipe = 1.67 min.
Time of concentration (TC) = 9.97 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 302.000 to Point/Station 303.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 306.000(Ft.)
End of street segment elevation = 230.000(Ft.)
Length of street segment = 987.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
3
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 10.444(CFS)
Depth of flow = 0.353(Ft.), Average velocity = 6.031(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 12.885(Ft.)
Flow velocity = 6.03(Ft/s)
Travel time = 2.73 min. TC = 12.70 min.
Adding area flow to street
Rainfall intensity (I) = 2.456(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Rainfall intensity = 2.456(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 7.613
Subarea runoff = 16.555(CFS) for 14.480(Ac.)
Total runoff = 18.694(CFS) Total area = 15.860(Ac.)
Street flow at end of street = 18.694(CFS)
Half street flow at end of street = 18.694(CFS)
Depth of flow = 0.419(Ft.), Average velocity = 6.935(Ft/s)
Flow width (from curb towards crown)= 16.200(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 303.000 to Point/Station 304.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 230.000(Ft.)
Downstream point/station elevation = 219.970(Ft.)
Pipe length = 660.00(Ft.) Slope = 0.0152 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 18.694(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 18.694(CFS)
Normal flow depth in pipe = 16.45(In.)
Flow top width inside pipe = 17.30(In.)
Critical Depth = 18.79(In.)
Pipe flow velocity = 9.25(Ft/s)
Travel time through pipe = 1.19 min.
Time of concentration (TC) = 13.89 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 303.000 to Point/Station 304.000
4
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 15.860(Ac.)
Runoff from this stream = 18.694(CFS)
Time of concentration = 13.89 min.
Rainfall intensity = 2.318(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 305.000 to Point/Station 306.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 1.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.540
Initial subarea total flow distance = 130.000(Ft.)
Highest elevation = 344.000(Ft.)
Lowest elevation = 335.000(Ft.)
Elevation difference = 9.000(Ft.) Slope = 6.923 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 6.92 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 5.29 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.5400)*( 100.000^.5)/( 6.923^(1/3)]= 5.29
The initial area total distance of 130.00 (Ft.) entered leaves a
remaining distance of 30.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 0.30 minutes
for a distance of 30.00 (Ft.) and a slope of 6.92 %
with an elevation difference of 2.08(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 0.300 Minutes
Tt=[(11.9*0.0057^3)/( 2.08)]^.385= 0.30
Total initial area Ti = 5.29 minutes from Figure 3-3 formula plus
0.30 minutes from the Figure 3-4 formula = 5.59 minutes
Rainfall intensity (I) = 4.169(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.540
Subarea runoff = 1.216(CFS)
Total initial stream area = 0.540(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 306.000 to Point/Station 307.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
5
______________________________________________________________________
Top of street segment elevation = 335.000(Ft.)
End of street segment elevation = 280.000(Ft.)
Length of street segment = 1260.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 8.573(CFS)
Depth of flow = 0.362(Ft.), Average velocity = 4.635(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 13.335(Ft.)
Flow velocity = 4.64(Ft/s)
Travel time = 4.53 min. TC = 10.12 min.
Adding area flow to street
Rainfall intensity (I) = 2.843(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.250
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.750
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.525
Rainfall intensity = 2.843(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.526 CA = 5.573
Subarea runoff = 14.627(CFS) for 10.060(Ac.)
Total runoff = 15.842(CFS) Total area = 10.600(Ac.)
Street flow at end of street = 15.842(CFS)
Half street flow at end of street = 15.842(CFS)
Depth of flow = 0.434(Ft.), Average velocity = 5.373(Ft/s)
Flow width (from curb towards crown)= 16.962(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 307.000 to Point/Station 308.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 280.000(Ft.)
Downstream point/station elevation = 275.260(Ft.)
Pipe length = 375.00(Ft.) Slope = 0.0126 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 15.842(CFS)
6
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 15.842(CFS)
Normal flow depth in pipe = 15.42(In.)
Flow top width inside pipe = 18.55(In.)
Critical Depth = 17.64(In.)
Pipe flow velocity = 8.37(Ft/s)
Travel time through pipe = 0.75 min.
Time of concentration (TC) = 10.87 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 307.000 to Point/Station 308.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.715(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 10.87 min.
Rainfall intensity = 2.715(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.518 CA = 6.653
Subarea runoff = 2.221(CFS) for 2.250(Ac.)
Total runoff = 18.063(CFS) Total area = 12.850(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 308.000 to Point/Station 304.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 253.000(Ft.)
Downstream point/station elevation = 219.110(Ft.)
Pipe length = 480.00(Ft.) Slope = 0.0706 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 18.063(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 18.063(CFS)
Normal flow depth in pipe = 10.55(In.)
Flow top width inside pipe = 17.73(In.)
Critical depth could not be calculated.
Pipe flow velocity = 16.80(Ft/s)
Travel time through pipe = 0.48 min.
Time of concentration (TC) = 11.34 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 308.000 to Point/Station 304.000
**** CONFLUENCE OF MINOR STREAMS ****
7
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 12.850(Ac.)
Runoff from this stream = 18.063(CFS)
Time of concentration = 11.34 min.
Rainfall intensity = 2.641(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 18.694 13.89 2.318
2 18.063 11.34 2.641
Qmax(1) =
1.000 * 1.000 * 18.694) +
0.878 * 1.000 * 18.063) + = 34.547
Qmax(2) =
1.000 * 0.817 * 18.694) +
1.000 * 1.000 * 18.063) + = 33.332
Total of 2 streams to confluence:
Flow rates before confluence point:
18.694 18.063
Maximum flow rates at confluence using above data:
34.547 33.332
Area of streams before confluence:
15.860 12.850
Results of confluence:
Total flow rate = 34.547(CFS)
Time of concentration = 13.886 min.
Effective stream area after confluence = 28.710(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 304.000 to Point/Station 309.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 220.000(Ft.)
Downstream point/station elevation = 214.080(Ft.)
Pipe length = 296.00(Ft.) Slope = 0.0200 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 34.547(CFS)
Nearest computed pipe diameter = 27.00(In.)
Calculated individual pipe flow = 34.547(CFS)
Normal flow depth in pipe = 18.09(In.)
Flow top width inside pipe = 25.39(In.)
Critical Depth = 24.03(In.)
Pipe flow velocity = 12.21(Ft/s)
Travel time through pipe = 0.40 min.
Time of concentration (TC) = 14.29 min.
8
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 304.000 to Point/Station 309.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 28.710(Ac.)
Runoff from this stream = 34.547(CFS)
Time of concentration = 14.29 min.
Rainfall intensity = 2.275(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 310.000 to Point/Station 311.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Initial subarea total flow distance = 382.000(Ft.)
Highest elevation = 296.000(Ft.)
Lowest elevation = 264.000(Ft.)
Elevation difference = 32.000(Ft.) Slope = 8.377 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 8.38 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 5.50 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4800)*( 100.000^.5)/( 8.377^(1/3)]= 5.50
The initial area total distance of 382.00 (Ft.) entered leaves a
remaining distance of 282.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 1.56 minutes
for a distance of 282.00 (Ft.) and a slope of 8.38 %
with an elevation difference of 23.62(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 1.563 Minutes
Tt=[(11.9*0.0534^3)/( 23.62)]^.385= 1.56
Total initial area Ti = 5.50 minutes from Figure 3-3 formula plus
1.56 minutes from the Figure 3-4 formula = 7.06 minutes
Rainfall intensity (I) = 3.586(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.480
Subarea runoff = 2.754(CFS)
Total initial stream area = 1.600(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
9
Process from Point/Station 311.000 to Point/Station 312.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 264.000(Ft.)
Downstream point elevation = 255.500(Ft.)
Channel length thru subarea = 132.000(Ft.)
Channel base width = 0.500(Ft.)
Slope or 'Z' of left channel bank = 2.000
Slope or 'Z' of right channel bank = 2.000
Manning's 'N' = 0.015
Maximum depth of channel = 1.000(Ft.)
Flow(q) thru subarea = 2.754(CFS)
Depth of flow = 0.306(Ft.), Average velocity = 8.081(Ft/s)
Channel flow top width = 1.725(Ft.)
Flow Velocity = 8.08(Ft/s)
Travel time = 0.27 min.
Time of concentration = 7.33 min.
Critical depth = 0.539(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 312.000 to Point/Station 313.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 255.500(Ft.)
End of street segment elevation = 218.000(Ft.)
Length of street segment = 724.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 8.242(CFS)
Depth of flow = 0.349(Ft.), Average velocity = 4.902(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 12.690(Ft.)
Flow velocity = 4.90(Ft/s)
Travel time = 2.46 min. TC = 9.79 min.
Adding area flow to street
Rainfall intensity (I) = 2.903(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
10
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Rainfall intensity = 2.903(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 4.709
Subarea runoff = 10.918(CFS) for 8.210(Ac.)
Total runoff = 13.672(CFS) Total area = 9.810(Ac.)
Street flow at end of street = 13.672(CFS)
Half street flow at end of street = 13.672(CFS)
Depth of flow = 0.405(Ft.), Average velocity = 5.533(Ft/s)
Flow width (from curb towards crown)= 15.492(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 313.000 to Point/Station 309.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 218.000(Ft.)
Downstream point/station elevation = 212.960(Ft.)
Pipe length = 970.00(Ft.) Slope = 0.0052 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 13.672(CFS)
Nearest computed pipe diameter = 24.00(In.)
Calculated individual pipe flow = 13.672(CFS)
Normal flow depth in pipe = 16.83(In.)
Flow top width inside pipe = 21.97(In.)
Critical Depth = 15.98(In.)
Pipe flow velocity = 5.81(Ft/s)
Travel time through pipe = 2.78 min.
Time of concentration (TC) = 12.57 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 313.000 to Point/Station 309.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 9.810(Ac.)
Runoff from this stream = 13.672(CFS)
Time of concentration = 12.57 min.
Rainfall intensity = 2.471(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 34.547 14.29 2.275
2 13.672 12.57 2.471
Qmax(1) =
1.000 * 1.000 * 34.547) +
11
0.921 * 1.000 * 13.672) + = 47.135
Qmax(2) =
1.000 * 0.880 * 34.547) +
1.000 * 1.000 * 13.672) + = 44.067
Total of 2 streams to confluence:
Flow rates before confluence point:
34.547 13.672
Maximum flow rates at confluence using above data:
47.135 44.067
Area of streams before confluence:
28.710 9.810
Results of confluence:
Total flow rate = 47.135(CFS)
Time of concentration = 14.290 min.
Effective stream area after confluence = 38.520(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 309.000 to Point/Station 309.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.275(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 14.29 min.
Rainfall intensity = 2.275(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.490 CA = 24.802
Subarea runoff = 9.296(CFS) for 12.140(Ac.)
Total runoff = 56.431(CFS) Total area = 50.660(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 309.000 to Point/Station 314.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 210.000(Ft.)
Downstream point/station elevation = 202.530(Ft.)
Pipe length = 725.00(Ft.) Slope = 0.0103 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 56.431(CFS)
Nearest computed pipe diameter = 36.00(In.)
Calculated individual pipe flow = 56.431(CFS)
Normal flow depth in pipe = 25.13(In.)
Flow top width inside pipe = 33.06(In.)
Critical Depth = 29.22(In.)
12
Pipe flow velocity = 10.72(Ft/s)
Travel time through pipe = 1.13 min.
Time of concentration (TC) = 15.42 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 309.000 to Point/Station 314.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.167(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.670
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.330
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.500
Time of concentration = 15.42 min.
Rainfall intensity = 2.167(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.494 CA = 46.588
Subarea runoff = 44.503(CFS) for 43.590(Ac.)
Total runoff = 100.934(CFS) Total area = 94.250(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 314.000 to Point/Station 315.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 206.000(Ft.)
Downstream point/station elevation = 200.500(Ft.)
Pipe length = 235.00(Ft.) Slope = 0.0234 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 100.934(CFS)
Nearest computed pipe diameter = 36.00(In.)
Calculated individual pipe flow = 100.934(CFS)
Normal flow depth in pipe = 29.16(In.)
Flow top width inside pipe = 28.25(In.)
Critical depth could not be calculated.
Pipe flow velocity = 16.46(Ft/s)
Travel time through pipe = 0.24 min.
Time of concentration (TC) = 15.65 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 314.000 to Point/Station 315.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.145(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
13
Decimal fraction soil group D = 0.000
[LOW DENSITY RESIDENTIAL ]
(2.9 DU/A or Less )
Impervious value, Ai = 0.250
Sub-Area C Value = 0.380
Time of concentration = 15.65 min.
Rainfall intensity = 2.145(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.489 CA = 48.401
Subarea runoff = 2.896(CFS) for 4.770(Ac.)
Total runoff = 103.830(CFS) Total area = 99.020(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 315.000 to Point/Station 316.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 197.000(Ft.)
Downstream point/station elevation = 176.530(Ft.)
Pipe length = 890.00(Ft.) Slope = 0.0230 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 103.830(CFS)
Nearest computed pipe diameter = 39.00(In.)
Calculated individual pipe flow = 103.830(CFS)
Normal flow depth in pipe = 27.09(In.)
Flow top width inside pipe = 35.92(In.)
Critical Depth = 36.53(In.)
Pipe flow velocity = 16.87(Ft/s)
Travel time through pipe = 0.88 min.
Time of concentration (TC) = 16.53 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 315.000 to Point/Station 316.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.071(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 16.53 min.
Rainfall intensity = 2.071(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.488 CA = 55.937
Subarea runoff = 12.012(CFS) for 15.700(Ac.)
Total runoff = 115.842(CFS) Total area = 114.720(Ac.)
14
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 316.000 to Point/Station 317.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 158.000(Ft.)
Downstream point/station elevation = 154.720(Ft.)
Pipe length = 205.00(Ft.) Slope = 0.0160 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 115.842(CFS)
Nearest computed pipe diameter = 42.00(In.)
Calculated individual pipe flow = 115.842(CFS)
Normal flow depth in pipe = 31.45(In.)
Flow top width inside pipe = 36.43(In.)
Critical Depth = 38.62(In.)
Pipe flow velocity = 14.99(Ft/s)
Travel time through pipe = 0.23 min.
Time of concentration (TC) = 16.76 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 316.000 to Point/Station 317.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.053(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 16.76 min.
Rainfall intensity = 2.053(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.487 CA = 56.950
Subarea runoff = 1.061(CFS) for 2.110(Ac.)
Total runoff = 116.902(CFS) Total area = 116.830(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 317.000 to Point/Station 318.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 154.000(Ft.)
Downstream point/station elevation = 148.210(Ft.)
Pipe length = 362.00(Ft.) Slope = 0.0160 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 116.902(CFS)
Nearest computed pipe diameter = 42.00(In.)
Calculated individual pipe flow = 116.902(CFS)
Normal flow depth in pipe = 31.69(In.)
Flow top width inside pipe = 36.15(In.)
Critical Depth = 38.72(In.)
15
Pipe flow velocity = 15.00(Ft/s)
Travel time through pipe = 0.40 min.
Time of concentration (TC) = 17.16 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 317.000 to Point/Station 318.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 116.830(Ac.)
Runoff from this stream = 116.902(CFS)
Time of concentration = 17.16 min.
Rainfall intensity = 2.022(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 320.000 to Point/Station 321.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Initial subarea total flow distance = 155.000(Ft.)
Highest elevation = 186.000(Ft.)
Lowest elevation = 183.000(Ft.)
Elevation difference = 3.000(Ft.) Slope = 1.935 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 80.00 (Ft)
for the top area slope value of 1.94 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 8.01 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4800)*( 80.000^.5)/( 1.935^(1/3)]= 8.01
The initial area total distance of 155.00 (Ft.) entered leaves a
remaining distance of 75.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 0.99 minutes
for a distance of 75.00 (Ft.) and a slope of 1.94 %
with an elevation difference of 1.45(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 0.991 Minutes
Tt=[(11.9*0.0142^3)/( 1.45)]^.385= 0.99
Total initial area Ti = 8.01 minutes from Figure 3-3 formula plus
0.99 minutes from the Figure 3-4 formula = 9.00 minutes
Rainfall intensity (I) = 3.065(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.480
16
Subarea runoff = 0.368(CFS)
Total initial stream area = 0.250(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 321.000 to Point/Station 322.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 183.000(Ft.)
End of street segment elevation = 165.000(Ft.)
Length of street segment = 855.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 4.894(CFS)
Depth of flow = 0.342(Ft.), Average velocity = 3.073(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 12.335(Ft.)
Flow velocity = 3.07(Ft/s)
Travel time = 4.64 min. TC = 13.64 min.
Adding area flow to street
Rainfall intensity (I) = 2.345(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Rainfall intensity = 2.345(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 3.994
Subarea runoff = 8.996(CFS) for 8.070(Ac.)
Total runoff = 9.364(CFS) Total area = 8.320(Ac.)
Street flow at end of street = 9.364(CFS)
Half street flow at end of street = 9.364(CFS)
Depth of flow = 0.414(Ft.), Average velocity = 3.589(Ft/s)
Flow width (from curb towards crown)= 15.931(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
17
Process from Point/Station 322.000 to Point/Station 323.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 165.000(Ft.)
Downstream point/station elevation = 158.300(Ft.)
Pipe length = 410.00(Ft.) Slope = 0.0163 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 9.364(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 9.364(CFS)
Normal flow depth in pipe = 11.06(In.)
Flow top width inside pipe = 17.52(In.)
Critical Depth = 14.19(In.)
Pipe flow velocity = 8.21(Ft/s)
Travel time through pipe = 0.83 min.
Time of concentration (TC) = 14.47 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 323.000 to Point/Station 324.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 158.300(Ft.)
End of street segment elevation = 156.000(Ft.)
Length of street segment = 506.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 15.683(CFS)
Depth of flow = 0.612(Ft.), Average velocity = 2.431(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 5.60(Ft.)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 18.000(Ft.)
Flow velocity = 2.43(Ft/s)
Travel time = 3.47 min. TC = 17.94 min.
Adding area flow to street
Rainfall intensity (I) = 1.965(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.600
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.400
18
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.516
Rainfall intensity = 1.965(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.503 CA = 11.171
Subarea runoff = 12.585(CFS) for 13.910(Ac.)
Total runoff = 21.949(CFS) Total area = 22.230(Ac.)
Street flow at end of street = 21.949(CFS)
Half street flow at end of street = 21.949(CFS)
Depth of flow = 0.683(Ft.), Average velocity = 2.656(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 9.17(Ft.)
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 324.000 to Point/Station 325.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 156.000(Ft.)
Downstream point/station elevation = 154.710(Ft.)
Pipe length = 430.00(Ft.) Slope = 0.0030 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 21.949(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 21.949(CFS)
Normal flow depth in pipe = 24.00(In.)
Flow top width inside pipe = 24.00(In.)
Critical Depth = 19.10(In.)
Pipe flow velocity = 5.22(Ft/s)
Travel time through pipe = 1.37 min.
Time of concentration (TC) = 19.31 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 324.000 to Point/Station 325.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.873(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.600
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.400
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.516
Time of concentration = 19.31 min.
Rainfall intensity = 1.873(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
19
(Q=KCIA) is C = 0.507 CA = 16.476
Subarea runoff = 8.918(CFS) for 10.280(Ac.)
Total runoff = 30.867(CFS) Total area = 32.510(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 325.000 to Point/Station 326.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 158.000(Ft.)
Downstream point/station elevation = 156.110(Ft.)
Pipe length = 315.00(Ft.) Slope = 0.0060 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 30.867(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 30.867(CFS)
Normal flow depth in pipe = 23.86(In.)
Flow top width inside pipe = 24.21(In.)
Critical Depth = 22.71(In.)
Pipe flow velocity = 7.38(Ft/s)
Travel time through pipe = 0.71 min.
Time of concentration (TC) = 20.03 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 325.000 to Point/Station 326.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.830(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.400
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.600
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.534
Time of concentration = 20.03 min.
Rainfall intensity = 1.830(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.511 CA = 20.064
Subarea runoff = 5.856(CFS) for 6.720(Ac.)
Total runoff = 36.722(CFS) Total area = 39.230(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 326.000 to Point/Station 327.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 156.000(Ft.)
Downstream point/station elevation = 154.860(Ft.)
Pipe length = 190.00(Ft.) Slope = 0.0060 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 36.722(CFS)
20
Nearest computed pipe diameter = 33.00(In.)
Calculated individual pipe flow = 36.722(CFS)
Normal flow depth in pipe = 24.38(In.)
Flow top width inside pipe = 29.00(In.)
Critical Depth = 24.21(In.)
Pipe flow velocity = 7.80(Ft/s)
Travel time through pipe = 0.41 min.
Time of concentration (TC) = 20.43 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 327.000 to Point/Station 327.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.807(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.400
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.400
Decimal fraction soil group D = 0.200
[LOW DENSITY RESIDENTIAL ]
(2.0 DU/A or Less )
Impervious value, Ai = 0.200
Sub-Area C Value = 0.396
Time of concentration = 20.43 min.
Rainfall intensity = 1.807(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.487 CA = 24.175
Subarea runoff = 6.954(CFS) for 10.380(Ac.)
Total runoff = 43.676(CFS) Total area = 49.610(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 327.000 to Point/Station 327.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.807(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.600
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.200
Decimal fraction soil group D = 0.200
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.510
Time of concentration = 20.43 min.
Rainfall intensity = 1.807(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.490 CA = 27.627
Subarea runoff = 6.238(CFS) for 6.770(Ac.)
Total runoff = 49.914(CFS) Total area = 56.380(Ac.)
21
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 327.000 to Point/Station 328.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 159.000(Ft.)
Downstream point/station elevation = 156.500(Ft.)
Pipe length = 250.00(Ft.) Slope = 0.0100 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 49.914(CFS)
Nearest computed pipe diameter = 33.00(In.)
Calculated individual pipe flow = 49.914(CFS)
Normal flow depth in pipe = 25.50(In.)
Flow top width inside pipe = 27.66(In.)
Critical Depth = 27.92(In.)
Pipe flow velocity = 10.13(Ft/s)
Travel time through pipe = 0.41 min.
Time of concentration (TC) = 20.84 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 327.000 to Point/Station 328.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.784(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.150
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.850
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(4.3 DU/A or Less )
Impervious value, Ai = 0.300
Sub-Area C Value = 0.469
Time of concentration = 20.84 min.
Rainfall intensity = 1.784(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.485 CA = 36.083
Subarea runoff = 14.444(CFS) for 18.010(Ac.)
Total runoff = 64.358(CFS) Total area = 74.390(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 328.000 to Point/Station 318.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 163.000(Ft.)
Downstream point/station elevation = 153.200(Ft.)
Pipe length = 980.00(Ft.) Slope = 0.0100 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 64.358(CFS)
Nearest computed pipe diameter = 36.00(In.)
Calculated individual pipe flow = 64.358(CFS)
Normal flow depth in pipe = 28.41(In.)
Flow top width inside pipe = 29.37(In.)
Critical Depth = 30.91(In.)
22
Pipe flow velocity = 10.75(Ft/s)
Travel time through pipe = 1.52 min.
Time of concentration (TC) = 22.36 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 328.000 to Point/Station 318.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 74.390(Ac.)
Runoff from this stream = 64.358(CFS)
Time of concentration = 22.36 min.
Rainfall intensity = 1.704(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 329.000 to Point/Station 330.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Initial subarea total flow distance = 974.000(Ft.)
Highest elevation = 230.000(Ft.)
Lowest elevation = 210.000(Ft.)
Elevation difference = 20.000(Ft.) Slope = 2.053 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 80.00 (Ft)
for the top area slope value of 2.05 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 7.85 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4800)*( 80.000^.5)/( 2.053^(1/3)]= 7.85
The initial area total distance of 974.00 (Ft.) entered leaves a
remaining distance of 894.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 6.53 minutes
for a distance of 894.00 (Ft.) and a slope of 2.05 %
with an elevation difference of 18.35(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 6.529 Minutes
Tt=[(11.9*0.1693^3)/( 18.35)]^.385= 6.53
Total initial area Ti = 7.85 minutes from Figure 3-3 formula plus
6.53 minutes from the Figure 3-4 formula = 14.38 minutes
Rainfall intensity (I) = 2.266(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.480
23
Subarea runoff = 2.066(CFS)
Total initial stream area = 1.900(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 330.000 to Point/Station 331.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 210.000(Ft.)
End of street segment elevation = 174.000(Ft.)
Length of street segment = 625.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 7.831(CFS)
Depth of flow = 0.338(Ft.), Average velocity = 5.043(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 12.172(Ft.)
Flow velocity = 5.04(Ft/s)
Travel time = 2.07 min. TC = 16.45 min.
Adding area flow to street
Rainfall intensity (I) = 2.078(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Rainfall intensity = 2.078(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 6.504
Subarea runoff = 11.448(CFS) for 11.650(Ac.)
Total runoff = 13.515(CFS) Total area = 13.550(Ac.)
Street flow at end of street = 13.515(CFS)
Half street flow at end of street = 13.515(CFS)
Depth of flow = 0.397(Ft.), Average velocity = 5.744(Ft/s)
Flow width (from curb towards crown)= 15.104(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
24
Process from Point/Station 331.000 to Point/Station 332.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 174.000(Ft.)
Downstream point/station elevation = 158.000(Ft.)
Pipe length = 400.00(Ft.) Slope = 0.0400 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 13.515(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 13.515(CFS)
Normal flow depth in pipe = 10.50(In.)
Flow top width inside pipe = 17.75(In.)
Critical Depth = 16.41(In.)
Pipe flow velocity = 12.63(Ft/s)
Travel time through pipe = 0.53 min.
Time of concentration (TC) = 16.98 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 332.000 to Point/Station 332.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.036(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 16.98 min.
Rainfall intensity = 2.036(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 17.088
Subarea runoff = 21.276(CFS) for 22.050(Ac.)
Total runoff = 34.790(CFS) Total area = 35.600(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 332.000 to Point/Station 318.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 164.000(Ft.)
Downstream point/station elevation = 147.830(Ft.)
Pipe length = 86.00(Ft.) Slope = 0.1880 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 34.790(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 34.790(CFS)
Normal flow depth in pipe = 11.78(In.)
Flow top width inside pipe = 17.12(In.)
Critical depth could not be calculated.
Pipe flow velocity = 28.39(Ft/s)
25
Travel time through pipe = 0.05 min.
Time of concentration (TC) = 17.03 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 332.000 to Point/Station 318.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 3
Stream flow area = 35.600(Ac.)
Runoff from this stream = 34.790(CFS)
Time of concentration = 17.03 min.
Rainfall intensity = 2.032(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 116.902 17.16 2.022
2 64.358 22.36 1.704
3 34.790 17.03 2.032
Qmax(1) =
1.000 * 1.000 * 116.902) +
1.000 * 0.768 * 64.358) +
0.995 * 1.000 * 34.790) + = 200.912
Qmax(2) =
0.843 * 1.000 * 116.902) +
1.000 * 1.000 * 64.358) +
0.839 * 1.000 * 34.790) + = 192.104
Qmax(3) =
1.000 * 0.992 * 116.902) +
1.000 * 0.761 * 64.358) +
1.000 * 1.000 * 34.790) + = 199.763
Total of 3 streams to confluence:
Flow rates before confluence point:
116.902 64.358 34.790
Maximum flow rates at confluence using above data:
200.912 192.104 199.763
Area of streams before confluence:
116.830 74.390 35.600
Results of confluence:
Total flow rate = 200.912(CFS)
Time of concentration = 17.164 min.
Effective stream area after confluence = 226.820(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 318.000 to Point/Station 333.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
26
Upstream point/station elevation = 162.000(Ft.)
Downstream point/station elevation = 149.490(Ft.)
Pipe length = 340.00(Ft.) Slope = 0.0368 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 200.912(CFS)
Nearest computed pipe diameter = 45.00(In.)
Calculated individual pipe flow = 200.912(CFS)
Normal flow depth in pipe = 32.34(In.)
Flow top width inside pipe = 40.46(In.)
Critical depth could not be calculated.
Pipe flow velocity = 23.64(Ft/s)
Travel time through pipe = 0.24 min.
Time of concentration (TC) = 17.40 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 318.000 to Point/Station 333.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.004(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[HIGH DENSITY RESIDENTIAL ]
(24.0 DU/A or Less )
Impervious value, Ai = 0.650
Sub-Area C Value = 0.660
Time of concentration = 17.40 min.
Rainfall intensity = 2.004(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.489 CA = 113.381
Subarea runoff = 26.256(CFS) for 4.940(Ac.)
Total runoff = 227.168(CFS) Total area = 231.760(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 333.000 to Point/Station 334.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 139.000(Ft.)
Downstream point/station elevation = 131.270(Ft.)
Pipe length = 210.00(Ft.) Slope = 0.0368 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 227.168(CFS)
Nearest computed pipe diameter = 45.00(In.)
Calculated individual pipe flow = 227.168(CFS)
Normal flow depth in pipe = 36.09(In.)
Flow top width inside pipe = 35.86(In.)
Critical depth could not be calculated.
Pipe flow velocity = 23.94(Ft/s)
Travel time through pipe = 0.15 min.
Time of concentration (TC) = 17.55 min.
27
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 333.000 to Point/Station 334.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.993(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(14.5 DU/A or Less )
Impervious value, Ai = 0.500
Sub-Area C Value = 0.550
Time of concentration = 17.55 min.
Rainfall intensity = 1.993(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.492 CA = 119.871
Subarea runoff = 11.711(CFS) for 11.800(Ac.)
Total runoff = 238.879(CFS) Total area = 243.560(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 334.000 to Point/Station 335.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 126.000(Ft.)
Downstream point/station elevation = 108.250(Ft.)
Pipe length = 355.00(Ft.) Slope = 0.0500 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 238.879(CFS)
Nearest computed pipe diameter = 45.00(In.)
Calculated individual pipe flow = 238.879(CFS)
Normal flow depth in pipe = 32.86(In.)
Flow top width inside pipe = 39.95(In.)
Critical depth could not be calculated.
Pipe flow velocity = 27.64(Ft/s)
Travel time through pipe = 0.21 min.
Time of concentration (TC) = 17.76 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 334.000 to Point/Station 335.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.977(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
28
Sub-Area C Value = 0.480
Time of concentration = 17.76 min.
Rainfall intensity = 1.977(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.491 CA = 129.605
Subarea runoff = 17.387(CFS) for 20.280(Ac.)
Total runoff = 256.266(CFS) Total area = 263.840(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 335.000 to Point/Station 336.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 108.000(Ft.)
Downstream point/station elevation = 91.750(Ft.)
Pipe length = 325.00(Ft.) Slope = 0.0500 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 256.266(CFS)
Nearest computed pipe diameter = 45.00(In.)
Calculated individual pipe flow = 256.266(CFS)
Normal flow depth in pipe = 34.92(In.)
Flow top width inside pipe = 37.52(In.)
Critical depth could not be calculated.
Pipe flow velocity = 27.86(Ft/s)
Travel time through pipe = 0.19 min.
Time of concentration (TC) = 17.96 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 335.000 to Point/Station 336.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.963(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.760
Time of concentration = 17.96 min.
Rainfall intensity = 1.963(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.495 CA = 132.258
Subarea runoff = 3.415(CFS) for 3.490(Ac.)
Total runoff = 259.681(CFS) Total area = 267.330(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 335.000 to Point/Station 336.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
29
Rainfall intensity (I) = 1.963(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 17.96 min.
Rainfall intensity = 1.963(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.494 CA = 135.191
Subarea runoff = 5.758(CFS) for 6.110(Ac.)
Total runoff = 265.439(CFS) Total area = 273.440(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 336.000 to Point/Station 337.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 91.000(Ft.)
Downstream point/station elevation = 84.190(Ft.)
Pipe length = 300.00(Ft.) Slope = 0.0227 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 265.439(CFS)
Nearest computed pipe diameter = 54.00(In.)
Calculated individual pipe flow = 265.439(CFS)
Normal flow depth in pipe = 39.89(In.)
Flow top width inside pipe = 47.45(In.)
Critical depth could not be calculated.
Pipe flow velocity = 21.07(Ft/s)
Travel time through pipe = 0.24 min.
Time of concentration (TC) = 18.20 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 336.000 to Point/Station 337.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.947(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(14.5 DU/A or Less )
Impervious value, Ai = 0.500
Sub-Area C Value = 0.550
Time of concentration = 18.20 min.
Rainfall intensity = 1.947(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.495 CA = 136.346
30
Subarea runoff = 0.011(CFS) for 2.100(Ac.)
Total runoff = 265.450(CFS) Total area = 275.540(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 337.000 to Point/Station 338.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 83.000(Ft.)
Downstream point/station elevation = 77.070(Ft.)
Pipe length = 190.00(Ft.) Slope = 0.0312 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 265.450(CFS)
Nearest computed pipe diameter = 51.00(In.)
Calculated individual pipe flow = 265.450(CFS)
Normal flow depth in pipe = 37.50(In.)
Flow top width inside pipe = 45.00(In.)
Critical depth could not be calculated.
Pipe flow velocity = 23.76(Ft/s)
Travel time through pipe = 0.13 min.
Time of concentration (TC) = 18.33 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 337.000 to Point/Station 338.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.938(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[LOW DENSITY RESIDENTIAL ]
(2.9 DU/A or Less )
Impervious value, Ai = 0.250
Sub-Area C Value = 0.380
Time of concentration = 18.33 min.
Rainfall intensity = 1.938(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.491 CA = 139.690
Subarea runoff = 5.233(CFS) for 8.800(Ac.)
Total runoff = 270.683(CFS) Total area = 284.340(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 338.000 to Point/Station 339.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 78.000(Ft.)
Downstream point/station elevation = 66.120(Ft.)
Pipe length = 260.00(Ft.) Slope = 0.0457 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 270.683(CFS)
Nearest computed pipe diameter = 48.00(In.)
31
Calculated individual pipe flow = 270.683(CFS)
Normal flow depth in pipe = 34.97(In.)
Flow top width inside pipe = 42.69(In.)
Critical depth could not be calculated.
Pipe flow velocity = 27.57(Ft/s)
Travel time through pipe = 0.16 min.
Time of concentration (TC) = 18.49 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 338.000 to Point/Station 339.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.927(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[LOW DENSITY RESIDENTIAL ]
(2.0 DU/A or Less )
Impervious value, Ai = 0.200
Sub-Area C Value = 0.340
Time of concentration = 18.49 min.
Rainfall intensity = 1.927(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.486 CA = 143.345
Subarea runoff = 5.557(CFS) for 10.750(Ac.)
Total runoff = 276.240(CFS) Total area = 295.090(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 339.000 to Point/Station 340.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 64.000(Ft.)
Downstream point/station elevation = 22.000(Ft.)
Pipe length = 1110.00(Ft.) Slope = 0.0378 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 276.240(CFS)
Nearest computed pipe diameter = 48.00(In.)
Calculated individual pipe flow = 276.240(CFS)
Normal flow depth in pipe = 38.86(In.)
Flow top width inside pipe = 37.69(In.)
Critical depth could not be calculated.
Pipe flow velocity = 25.35(Ft/s)
Travel time through pipe = 0.73 min.
Time of concentration (TC) = 19.22 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 340.000 to Point/Station 341.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
32
Upstream point/station elevation = 22.000(Ft.)
Downstream point/station elevation = 21.090(Ft.)
Pipe length = 325.00(Ft.) Slope = 0.0028 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 276.240(CFS)
Nearest computed pipe diameter = 78.00(In.)
Calculated individual pipe flow = 276.240(CFS)
Normal flow depth in pipe = 63.56(In.)
Flow top width inside pipe = 60.59(In.)
Critical Depth = 53.56(In.)
Pipe flow velocity = 9.53(Ft/s)
Travel time through pipe = 0.57 min.
Time of concentration (TC) = 19.78 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 340.000 to Point/Station 341.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.845(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.950
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.050
Decimal fraction soil group D = 0.000
[LOW DENSITY RESIDENTIAL ]
(1.0 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.275
Time of concentration = 19.78 min.
Rainfall intensity = 1.845(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.452 CA = 158.703
Subarea runoff = 16.498(CFS) for 55.950(Ac.)
Total runoff = 292.738(CFS) Total area = 351.040(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 341.000 to Point/Station 342.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 22.000(Ft.)
Downstream point/station elevation = 18.920(Ft.)
Pipe length = 1100.00(Ft.) Slope = 0.0028 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 292.738(CFS)
Nearest computed pipe diameter = 81.00(In.)
Calculated individual pipe flow = 292.738(CFS)
Normal flow depth in pipe = 63.28(In.)
Flow top width inside pipe = 66.97(In.)
Critical Depth = 54.55(In.)
Pipe flow velocity = 9.76(Ft/s)
Travel time through pipe = 1.88 min.
Time of concentration (TC) = 21.66 min.
33
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 341.000 to Point/Station 342.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.740(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[INDUSTRIAL area type ]
(General Industrial )
Impervious value, Ai = 0.950
Sub-Area C Value = 0.870
The area added to the existing stream causes a
a lower flow rate of Q = 277.948(CFS)
therefore the upstream flow rate of Q = 292.738(CFS) is being used
Time of concentration = 21.66 min.
Rainfall intensity = 1.740(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.454 CA = 159.764
Subarea runoff = 0.000(CFS) for 1.220(Ac.)
Total runoff = 292.738(CFS) Total area = 352.260(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 342.000 to Point/Station 343.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 20.000(Ft.)
Downstream point/station elevation = 19.220(Ft.)
Pipe length = 280.00(Ft.) Slope = 0.0028 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 292.738(CFS)
Nearest computed pipe diameter = 81.00(In.)
Calculated individual pipe flow = 292.738(CFS)
Normal flow depth in pipe = 63.47(In.)
Flow top width inside pipe = 66.71(In.)
Critical Depth = 54.55(In.)
Pipe flow velocity = 9.74(Ft/s)
Travel time through pipe = 0.48 min.
Time of concentration (TC) = 22.14 min.
End of computations, total study area = 352.260 (Ac.)
1
San Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2009 Version 7.8
Rational method hydrology program based on
San Diego County Flood Control Division 2003 hydrology manual
Rational Hydrology Study Date: 12/08/12
------------------------------------------------------------------------
City of Carlsbad
Hydromodification Exemption Study
Major Basin 400
10-Year Flow Rate
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Program License Serial Number 4028
------------------------------------------------------------------------
Rational hydrology study storm event year is 10.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 1.700
24 hour precipitation(inches) = 3.100
P6/P24 = 54.8%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 400.000 to Point/Station 401.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Initial subarea total flow distance = 646.000(Ft.)
Highest elevation = 331.000(Ft.)
Lowest elevation = 309.000(Ft.)
Elevation difference = 22.000(Ft.) Slope = 3.406 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 95.00 (Ft)
for the top area slope value of 3.41 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
2
Initial Area Time of Concentration = 7.23 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4800)*( 95.000^.5)/( 3.406^(1/3)]= 7.23
The initial area total distance of 646.00 (Ft.) entered leaves a
remaining distance of 551.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 3.70 minutes
for a distance of 551.00 (Ft.) and a slope of 3.41 %
with an elevation difference of 18.77(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 3.701 Minutes
Tt=[(11.9*0.1044^3)/( 18.77)]^.385= 3.70
Total initial area Ti = 7.23 minutes from Figure 3-3 formula plus
3.70 minutes from the Figure 3-4 formula = 10.93 minutes
Rainfall intensity (I) = 2.705(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.480
Subarea runoff = 3.284(CFS)
Total initial stream area = 2.530(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 401.000 to Point/Station 402.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 309.000(Ft.)
End of street segment elevation = 230.000(Ft.)
Length of street segment = 1121.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 16.691(CFS)
Depth of flow = 0.410(Ft.), Average velocity = 6.525(Ft/s)
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 15.770(Ft.)
Flow velocity = 6.52(Ft/s)
Travel time = 2.86 min. TC = 13.79 min.
Adding area flow to street
Rainfall intensity (I) = 2.328(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
3
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Rainfall intensity = 2.328(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 12.893
Subarea runoff = 26.725(CFS) for 24.330(Ac.)
Total runoff = 30.010(CFS) Total area = 26.860(Ac.)
Street flow at end of street = 30.010(CFS)
Half street flow at end of street = 30.010(CFS)
Depth of flow = 0.484(Ft.), Average velocity = 7.815(Ft/s)
Note: depth of flow exceeds top of street crown.
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 402.000 to Point/Station 403.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 230.000(Ft.)
Downstream point/station elevation = 210.280(Ft.)
Pipe length = 290.00(Ft.) Slope = 0.0680 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 30.010(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 30.010(CFS)
Normal flow depth in pipe = 13.27(In.)
Flow top width inside pipe = 20.26(In.)
Critical depth could not be calculated.
Pipe flow velocity = 18.73(Ft/s)
Travel time through pipe = 0.26 min.
Time of concentration (TC) = 14.05 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 402.000 to Point/Station 403.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.300(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.800
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.200
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.492
Time of concentration = 14.05 min.
Rainfall intensity = 2.300(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.481 CA = 13.473
Subarea runoff = 0.979(CFS) for 1.180(Ac.)
Total runoff = 30.988(CFS) Total area = 28.040(Ac.)
4
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 403.000 to Point/Station 404.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 210.000(Ft.)
Downstream point/station elevation = 181.500(Ft.)
Pipe length = 475.00(Ft.) Slope = 0.0600 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 30.988(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 30.988(CFS)
Normal flow depth in pipe = 14.18(In.)
Flow top width inside pipe = 19.67(In.)
Critical depth could not be calculated.
Pipe flow velocity = 17.92(Ft/s)
Travel time through pipe = 0.44 min.
Time of concentration (TC) = 14.49 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 403.000 to Point/Station 404.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.254(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.500
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.500
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.510
Time of concentration = 14.49 min.
Rainfall intensity = 2.254(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.485 CA = 15.988
Subarea runoff = 5.056(CFS) for 4.930(Ac.)
Total runoff = 36.044(CFS) Total area = 32.970(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 404.000 to Point/Station 405.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 176.000(Ft.)
Downstream point/station elevation = 164.700(Ft.)
Pipe length = 565.00(Ft.) Slope = 0.0200 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 36.044(CFS)
Nearest computed pipe diameter = 27.00(In.)
Calculated individual pipe flow = 36.044(CFS)
Normal flow depth in pipe = 18.66(In.)
5
Flow top width inside pipe = 24.95(In.)
Critical Depth = 24.36(In.)
Pipe flow velocity = 12.30(Ft/s)
Travel time through pipe = 0.77 min.
Time of concentration (TC) = 15.26 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 404.000 to Point/Station 405.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 32.970(Ac.)
Runoff from this stream = 36.044(CFS)
Time of concentration = 15.26 min.
Rainfall intensity = 2.181(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 406.000 to Point/Station 407.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Initial subarea total flow distance = 428.000(Ft.)
Highest elevation = 247.000(Ft.)
Lowest elevation = 219.000(Ft.)
Elevation difference = 28.000(Ft.) Slope = 6.542 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 6.54 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 5.97 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4800)*( 100.000^.5)/( 6.542^(1/3)]= 5.97
The initial area total distance of 428.00 (Ft.) entered leaves a
remaining distance of 328.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 1.93 minutes
for a distance of 328.00 (Ft.) and a slope of 6.54 %
with an elevation difference of 21.46(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 1.931 Minutes
Tt=[(11.9*0.0621^3)/( 21.46)]^.385= 1.93
Total initial area Ti = 5.97 minutes from Figure 3-3 formula plus
1.93 minutes from the Figure 3-4 formula = 7.90 minutes
6
Rainfall intensity (I) = 3.335(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.480
Subarea runoff = 2.914(CFS)
Total initial stream area = 1.820(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 407.000 to Point/Station 408.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 219.000(Ft.)
End of street segment elevation = 188.000(Ft.)
Length of street segment = 731.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 18.552(CFS)
Depth of flow = 0.457(Ft.), Average velocity = 5.538(Ft/s)
Note: depth of flow exceeds top of street crown.
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 18.000(Ft.)
Flow velocity = 5.54(Ft/s)
Travel time = 2.20 min. TC = 10.10 min.
Adding area flow to street
Rainfall intensity (I) = 2.846(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Rainfall intensity = 2.846(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 11.990
Subarea runoff = 31.216(CFS) for 23.160(Ac.)
Total runoff = 34.130(CFS) Total area = 24.980(Ac.)
Street flow at end of street = 34.130(CFS)
Half street flow at end of street = 34.130(CFS)
Depth of flow = 0.547(Ft.), Average velocity = 6.799(Ft/s)
Warning: depth of flow exceeds top of curb
7
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 2.34(Ft.)
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 408.000 to Point/Station 409.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 188.000(Ft.)
Downstream point/station elevation = 187.440(Ft.)
Pipe length = 56.00(Ft.) Slope = 0.0100 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 34.130(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 34.130(CFS)
Normal flow depth in pipe = 20.91(In.)
Flow top width inside pipe = 27.58(In.)
Critical Depth = 23.84(In.)
Pipe flow velocity = 9.35(Ft/s)
Travel time through pipe = 0.10 min.
Time of concentration (TC) = 10.20 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 408.000 to Point/Station 409.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.828(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.950
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.050
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.483
Time of concentration = 10.20 min.
Rainfall intensity = 2.828(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 13.681
Subarea runoff = 4.565(CFS) for 3.500(Ac.)
Total runoff = 38.695(CFS) Total area = 28.480(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 409.000 to Point/Station 410.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 188.000(Ft.)
Downstream point/station elevation = 175.800(Ft.)
Pipe length = 610.00(Ft.) Slope = 0.0200 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 38.695(CFS)
8
Nearest computed pipe diameter = 27.00(In.)
Calculated individual pipe flow = 38.695(CFS)
Normal flow depth in pipe = 19.73(In.)
Flow top width inside pipe = 23.95(In.)
Critical Depth = 24.87(In.)
Pipe flow velocity = 12.44(Ft/s)
Travel time through pipe = 0.82 min.
Time of concentration (TC) = 11.02 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 409.000 to Point/Station 410.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.691(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.400
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.600
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.516
Time of concentration = 11.02 min.
Rainfall intensity = 2.691(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.484 CA = 15.461
Subarea runoff = 2.913(CFS) for 3.450(Ac.)
Total runoff = 41.608(CFS) Total area = 31.930(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 410.000 to Point/Station 405.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 162.000(Ft.)
Downstream point/station elevation = 145.200(Ft.)
Pipe length = 420.00(Ft.) Slope = 0.0400 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 41.608(CFS)
Nearest computed pipe diameter = 24.00(In.)
Calculated individual pipe flow = 41.608(CFS)
Normal flow depth in pipe = 18.14(In.)
Flow top width inside pipe = 20.62(In.)
Critical depth could not be calculated.
Pipe flow velocity = 16.34(Ft/s)
Travel time through pipe = 0.43 min.
Time of concentration (TC) = 11.44 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 410.000 to Point/Station 405.000
**** CONFLUENCE OF MINOR STREAMS ****
9
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 31.930(Ac.)
Runoff from this stream = 41.608(CFS)
Time of concentration = 11.44 min.
Rainfall intensity = 2.626(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 36.044 15.26 2.181
2 41.608 11.44 2.626
Qmax(1) =
1.000 * 1.000 * 36.044) +
0.831 * 1.000 * 41.608) + = 70.603
Qmax(2) =
1.000 * 0.750 * 36.044) +
1.000 * 1.000 * 41.608) + = 68.638
Total of 2 streams to confluence:
Flow rates before confluence point:
36.044 41.608
Maximum flow rates at confluence using above data:
70.603 68.638
Area of streams before confluence:
32.970 31.930
Results of confluence:
Total flow rate = 70.603(CFS)
Time of concentration = 15.260 min.
Effective stream area after confluence = 64.900(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 405.000 to Point/Station 405.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.181(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.050
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.950
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.537
Time of concentration = 15.26 min.
Rainfall intensity = 2.181(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.491 CA = 36.593
Subarea runoff = 9.202(CFS) for 9.580(Ac.)
10
Total runoff = 79.805(CFS) Total area = 74.480(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 405.000 to Point/Station 411.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 146.000(Ft.)
Downstream point/station elevation = 136.320(Ft.)
Pipe length = 242.00(Ft.) Slope = 0.0400 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 79.805(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 79.805(CFS)
Normal flow depth in pipe = 23.91(In.)
Flow top width inside pipe = 24.14(In.)
Critical depth could not be calculated.
Pipe flow velocity = 19.04(Ft/s)
Travel time through pipe = 0.21 min.
Time of concentration (TC) = 15.47 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 405.000 to Point/Station 411.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.162(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 1.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.540
Time of concentration = 15.47 min.
Rainfall intensity = 2.162(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.493 CA = 38.440
Subarea runoff = 3.286(CFS) for 3.420(Ac.)
Total runoff = 83.091(CFS) Total area = 77.900(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 411.000 to Point/Station 412.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 136.000(Ft.)
Downstream point/station elevation = 117.830(Ft.)
Pipe length = 395.00(Ft.) Slope = 0.0460 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 83.091(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 83.091(CFS)
11
Normal flow depth in pipe = 23.20(In.)
Flow top width inside pipe = 25.12(In.)
Critical depth could not be calculated.
Pipe flow velocity = 20.38(Ft/s)
Travel time through pipe = 0.32 min.
Time of concentration (TC) = 15.79 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 411.000 to Point/Station 412.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.133(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.670
Decimal fraction soil group D = 0.330
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.550
Time of concentration = 15.79 min.
Rainfall intensity = 2.133(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.496 CA = 40.667
Subarea runoff = 3.650(CFS) for 4.050(Ac.)
Total runoff = 86.741(CFS) Total area = 81.950(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 412.000 to Point/Station 413.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 116.000(Ft.)
Downstream point/station elevation = 107.990(Ft.)
Pipe length = 176.00(Ft.) Slope = 0.0455 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 86.741(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 86.741(CFS)
Normal flow depth in pipe = 24.38(In.)
Flow top width inside pipe = 23.42(In.)
Critical depth could not be calculated.
Pipe flow velocity = 20.32(Ft/s)
Travel time through pipe = 0.14 min.
Time of concentration (TC) = 15.94 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 412.000 to Point/Station 413.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.120(In/Hr) for a 10.0 year storm
12
Decimal fraction soil group A = 0.330
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.330
Decimal fraction soil group D = 0.340
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.530
Time of concentration = 15.94 min.
Rainfall intensity = 2.120(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.501 CA = 48.506
Subarea runoff = 16.116(CFS) for 14.780(Ac.)
Total runoff = 102.857(CFS) Total area = 96.730(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 413.000 to Point/Station 414.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 108.000(Ft.)
Downstream point/station elevation = 87.490(Ft.)
Pipe length = 260.00(Ft.) Slope = 0.0789 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 102.857(CFS)
Nearest computed pipe diameter = 30.00(In.)
Calculated individual pipe flow = 102.857(CFS)
Normal flow depth in pipe = 22.10(In.)
Flow top width inside pipe = 26.42(In.)
Critical depth could not be calculated.
Pipe flow velocity = 26.53(Ft/s)
Travel time through pipe = 0.16 min.
Time of concentration (TC) = 16.10 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 413.000 to Point/Station 414.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.107(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.500
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.250
Decimal fraction soil group D = 0.250
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.517
Time of concentration = 16.10 min.
Rainfall intensity = 2.107(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.503 CA = 55.565
Subarea runoff = 14.196(CFS) for 13.640(Ac.)
13
Total runoff = 117.052(CFS) Total area = 110.370(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 414.000 to Point/Station 415.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 86.000(Ft.)
Downstream point/station elevation = 85.000(Ft.)
Pipe length = 100.00(Ft.) Slope = 0.0100 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 117.052(CFS)
Nearest computed pipe diameter = 45.00(In.)
Calculated individual pipe flow = 117.052(CFS)
Normal flow depth in pipe = 35.63(In.)
Flow top width inside pipe = 36.55(In.)
Critical Depth = 39.23(In.)
Pipe flow velocity = 12.47(Ft/s)
Travel time through pipe = 0.13 min.
Time of concentration (TC) = 16.24 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 414.000 to Point/Station 415.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 110.370(Ac.)
Runoff from this stream = 117.052(CFS)
Time of concentration = 16.24 min.
Rainfall intensity = 2.095(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 415.000 to Point/Station 415.000
**** USER DEFINED FLOW INFORMATION AT A POINT ****
______________________________________________________________________
User specified 'C' value of 0.480 given for subarea
Rainfall intensity (I) = 1.277(In/Hr) for a 10.0 year storm
User specified values are as follows:
TC = 35.00 min. Rain intensity = 1.28(In/Hr)
Total area = 260.320(Ac.) Total runoff = 171.000(CFS)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 415.000 to Point/Station 415.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 260.320(Ac.)
Runoff from this stream = 171.000(CFS)
Time of concentration = 35.00 min.
Rainfall intensity = 1.277(In/Hr)
14
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 117.052 16.24 2.095
2 171.000 35.00 1.277
Qmax(1) =
1.000 * 1.000 * 117.052) +
1.000 * 0.464 * 171.000) + = 196.377
Qmax(2) =
0.609 * 1.000 * 117.052) +
1.000 * 1.000 * 171.000) + = 242.321
Total of 2 streams to confluence:
Flow rates before confluence point:
117.052 171.000
Maximum flow rates at confluence using above data:
196.377 242.321
Area of streams before confluence:
110.370 260.320
Results of confluence:
Total flow rate = 242.321(CFS)
Time of concentration = 35.000 min.
Effective stream area after confluence = 370.690(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 415.000 to Point/Station 416.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 67.000(Ft.)
Downstream point/station elevation = 28.750(Ft.)
Pipe length = 778.00(Ft.) Slope = 0.0492 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 242.321(CFS)
Nearest computed pipe diameter = 45.00(In.)
Calculated individual pipe flow = 242.321(CFS)
Normal flow depth in pipe = 33.47(In.)
Flow top width inside pipe = 39.29(In.)
Critical depth could not be calculated.
Pipe flow velocity = 27.49(Ft/s)
Travel time through pipe = 0.47 min.
Time of concentration (TC) = 35.47 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 415.000 to Point/Station 416.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 370.690(Ac.)
15
Runoff from this stream = 242.321(CFS)
Time of concentration = 35.47 min.
Rainfall intensity = 1.266(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 417.000 to Point/Station 417.000
**** USER DEFINED FLOW INFORMATION AT A POINT ****
______________________________________________________________________
User specified 'C' value of 0.500 given for subarea
Rainfall intensity (I) = 2.205(In/Hr) for a 10.0 year storm
User specified values are as follows:
TC = 15.00 min. Rain intensity = 2.21(In/Hr)
Total area = 23.750(Ac.) Total runoff = 26.100(CFS)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 417.000 to Point/Station 417.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.205(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.570
Time of concentration = 15.00 min.
Rainfall intensity = 2.205(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.515 CA = 15.608
Subarea runoff = 8.319(CFS) for 6.550(Ac.)
Total runoff = 34.419(CFS) Total area = 30.300(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 417.000 to Point/Station 416.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 120.000(Ft.)
Downstream point/station elevation = 68.200(Ft.)
Pipe length = 740.00(Ft.) Slope = 0.0700 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 34.419(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 34.419(CFS)
Normal flow depth in pipe = 14.48(In.)
Flow top width inside pipe = 19.43(In.)
Critical depth could not be calculated.
Pipe flow velocity = 19.45(Ft/s)
Travel time through pipe = 0.63 min.
16
Time of concentration (TC) = 15.63 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 417.000 to Point/Station 416.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 30.300(Ac.)
Runoff from this stream = 34.419(CFS)
Time of concentration = 15.63 min.
Rainfall intensity = 2.147(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 242.321 35.47 1.266
2 34.419 15.63 2.147
Qmax(1) =
1.000 * 1.000 * 242.321) +
0.590 * 1.000 * 34.419) + = 262.612
Qmax(2) =
1.000 * 0.441 * 242.321) +
1.000 * 1.000 * 34.419) + = 141.221
Total of 2 streams to confluence:
Flow rates before confluence point:
242.321 34.419
Maximum flow rates at confluence using above data:
262.612 141.221
Area of streams before confluence:
370.690 30.300
Results of confluence:
Total flow rate = 262.612(CFS)
Time of concentration = 35.472 min.
Effective stream area after confluence = 400.990(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 416.000 to Point/Station 418.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 28.750(Ft.)
Downstream point/station elevation = 18.690(Ft.)
Pipe length = 214.00(Ft.) Slope = 0.0470 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 262.612(CFS)
Nearest computed pipe diameter = 48.00(In.)
Calculated individual pipe flow = 262.612(CFS)
Normal flow depth in pipe = 33.80(In.)
Flow top width inside pipe = 43.82(In.)
17
Critical depth could not be calculated.
Pipe flow velocity = 27.79(Ft/s)
Travel time through pipe = 0.13 min.
Time of concentration (TC) = 35.60 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 416.000 to Point/Station 418.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 1.263(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.080
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.020
Decimal fraction soil group D = 0.900
[LOW DENSITY RESIDENTIAL ]
(1.0 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.398
The area added to the existing stream causes a
a lower flow rate of Q = 258.450(CFS)
therefore the upstream flow rate of Q = 262.612(CFS) is being used
Time of concentration = 35.60 min.
Rainfall intensity = 1.263(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.484 CA = 204.664
Subarea runoff = 0.000(CFS) for 21.460(Ac.)
Total runoff = 262.612(CFS) Total area = 422.450(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 418.000 to Point/Station 419.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 28.000(Ft.)
Downstream point/station elevation = 21.600(Ft.)
Pipe length = 1600.00(Ft.) Slope = 0.0040 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 262.612(CFS)
Nearest computed pipe diameter = 72.00(In.)
Calculated individual pipe flow = 262.612(CFS)
Normal flow depth in pipe = 57.75(In.)
Flow top width inside pipe = 57.37(In.)
Critical Depth = 53.27(In.)
Pipe flow velocity = 10.80(Ft/s)
Travel time through pipe = 2.47 min.
Time of concentration (TC) = 38.07 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 418.000 to Point/Station 419.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
18
Rainfall intensity (I) = 1.209(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
[MEDIUM DENSITY RESIDENTIAL ]
(10.9 DU/A or Less )
Impervious value, Ai = 0.450
Sub-Area C Value = 0.600
The area added to the existing stream causes a
a lower flow rate of Q = 248.060(CFS)
therefore the upstream flow rate of Q = 262.612(CFS) is being used
Time of concentration = 38.07 min.
Rainfall intensity = 1.209(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.485 CA = 205.120
Subarea runoff = 0.000(CFS) for 0.760(Ac.)
Total runoff = 262.612(CFS) Total area = 423.210(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 419.000 to Point/Station 420.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 10.000(Ft.)
Downstream point/station elevation = 9.020(Ft.)
Pipe length = 245.00(Ft.) Slope = 0.0040 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 262.612(CFS)
Nearest computed pipe diameter = 72.00(In.)
Calculated individual pipe flow = 262.612(CFS)
Normal flow depth in pipe = 57.75(In.)
Flow top width inside pipe = 57.37(In.)
Critical Depth = 53.27(In.)
Pipe flow velocity = 10.80(Ft/s)
Travel time through pipe = 0.38 min.
Time of concentration (TC) = 38.45 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 419.000 to Point/Station 420.000
**** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________
The following data inside Main Stream is listed:
In Main Stream number: 1
Stream flow area = 423.210(Ac.)
Runoff from this stream = 262.612(CFS)
Time of concentration = 38.45 min.
Rainfall intensity = 1.202(In/Hr)
Program is now starting with Main Stream No. 2
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
19
Process from Point/Station 430.000 to Point/Station 431.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 0.200
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.150
Decimal fraction soil group D = 0.650
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.547
Initial subarea total flow distance = 665.000(Ft.)
Highest elevation = 134.500(Ft.)
Lowest elevation = 51.000(Ft.)
Elevation difference = 83.500(Ft.) Slope = 12.556 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 12.56 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 4.28 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.5475)*( 100.000^.5)/( 12.556^(1/3)]= 4.28
The initial area total distance of 665.00 (Ft.) entered leaves a
remaining distance of 565.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 2.28 minutes
for a distance of 565.00 (Ft.) and a slope of 12.56 %
with an elevation difference of 70.94(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 2.284 Minutes
Tt=[(11.9*0.1070^3)/( 70.94)]^.385= 2.28
Total initial area Ti = 4.28 minutes from Figure 3-3 formula plus
2.28 minutes from the Figure 3-4 formula = 6.56 minutes
Rainfall intensity (I) = 3.759(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.547
Subarea runoff = 6.647(CFS)
Total initial stream area = 3.230(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 431.000 to Point/Station 432.000
**** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________
Top of street segment elevation = 51.000(Ft.)
End of street segment elevation = 14.000(Ft.)
Length of street segment = 830.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 8.000(Ft.)
Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
20
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0180
Manning's N from grade break to crown = 0.0180
Estimated mean flow rate at midpoint of street = 25.415(CFS)
Depth of flow = 0.493(Ft.), Average velocity = 6.373(Ft/s)
Note: depth of flow exceeds top of street crown.
Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 18.000(Ft.)
Flow velocity = 6.37(Ft/s)
Travel time = 2.17 min. TC = 8.73 min.
Adding area flow to street
Rainfall intensity (I) = 3.126(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.300
Decimal fraction soil group D = 0.700
[MEDIUM DENSITY RESIDENTIAL ]
(4.3 DU/A or Less )
Impervious value, Ai = 0.300
Sub-Area C Value = 0.508
Rainfall intensity = 3.126(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.513 CA = 14.113
Subarea runoff = 37.468(CFS) for 24.300(Ac.)
Total runoff = 44.114(CFS) Total area = 27.530(Ac.)
Street flow at end of street = 44.114(CFS)
Half street flow at end of street = 44.114(CFS)
Depth of flow = 0.591(Ft.), Average velocity = 7.403(Ft/s)
Warning: depth of flow exceeds top of curb
Note: depth of flow exceeds top of street crown.
Distance that curb overflow reaches into property = 4.53(Ft.)
Flow width (from curb towards crown)= 18.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 432.000 to Point/Station 433.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 14.000(Ft.)
Downstream point/station elevation = 12.950(Ft.)
Pipe length = 150.00(Ft.) Slope = 0.0070 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 44.114(CFS)
Nearest computed pipe diameter = 33.00(In.)
Calculated individual pipe flow = 44.114(CFS)
Normal flow depth in pipe = 26.95(In.)
Flow top width inside pipe = 25.53(In.)
Critical Depth = 26.43(In.)
Pipe flow velocity = 8.49(Ft/s)
21
Travel time through pipe = 0.29 min.
Time of concentration (TC) = 9.03 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 432.000 to Point/Station 433.000
**** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________
The following data inside Main Stream is listed:
In Main Stream number: 2
Stream flow area = 27.530(Ac.)
Runoff from this stream = 44.114(CFS)
Time of concentration = 9.03 min.
Rainfall intensity = 3.060(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 262.612 38.45 1.202
2 44.114 9.03 3.060
Qmax(1) =
1.000 * 1.000 * 262.612) +
0.393 * 1.000 * 44.114) + = 279.937
Qmax(2) =
1.000 * 0.235 * 262.612) +
1.000 * 1.000 * 44.114) + = 105.775
Total of 2 main streams to confluence:
Flow rates before confluence point:
262.612 44.114
Maximum flow rates at confluence using above data:
279.937 105.775
Area of streams before confluence:
423.210 27.530
Results of confluence:
Total flow rate = 279.937(CFS)
Time of concentration = 38.448 min.
Effective stream area after confluence = 450.740(Ac.)
End of computations, total study area = 450.740 (Ac.)
1
San Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2009 Version 7.8
Rational method hydrology program based on
San Diego County Flood Control Division 2003 hydrology manual
Rational Hydrology Study Date: 12/08/12
------------------------------------------------------------------------
City of Carlsbad
Hydromodification Exemption Study
Major Basin 500
10-Year Flow Rate
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Program License Serial Number 4028
------------------------------------------------------------------------
Rational hydrology study storm event year is 10.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 1.700
24 hour precipitation(inches) = 3.100
P6/P24 = 54.8%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 500.000 to Point/Station 501.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Initial subarea total flow distance = 250.000(Ft.)
Highest elevation = 50.000(Ft.)
Lowest elevation = 48.000(Ft.)
Elevation difference = 2.000(Ft.) Slope = 0.800 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 65.00 (Ft)
for the top area slope value of 0.80 %, in a development type of
7.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 9.69 minutes
TC = [1.8*(1.1-C)*distance(Ft.)^.5)/(% slope^(1/3)]
TC = [1.8*(1.1-0.4800)*( 65.000^.5)/( 0.800^(1/3)]= 9.69
2
The initial area total distance of 250.00 (Ft.) entered leaves a
remaining distance of 185.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 2.79 minutes
for a distance of 185.00 (Ft.) and a slope of 0.80 %
with an elevation difference of 1.48(Ft.) from the end of the top area
Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr)
= 2.790 Minutes
Tt=[(11.9*0.0350^3)/( 1.48)]^.385= 2.79
Total initial area Ti = 9.69 minutes from Figure 3-3 formula plus
2.79 minutes from the Figure 3-4 formula = 12.48 minutes
Rainfall intensity (I) = 2.483(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.480
Subarea runoff = 1.156(CFS)
Total initial stream area = 0.970(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 501.000 to Point/Station 502.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 48.000(Ft.)
Downstream point/station elevation = 47.100(Ft.)
Pipe length = 180.00(Ft.) Slope = 0.0050 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.156(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.156(CFS)
Normal flow depth in pipe = 7.29(In.)
Flow top width inside pipe = 7.06(In.)
Critical Depth = 5.93(In.)
Pipe flow velocity = 3.02(Ft/s)
Travel time through pipe = 0.99 min.
Time of concentration (TC) = 13.48 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 501.000 to Point/Station 502.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
Rainfall intensity (I) = 2.363(In/Hr) for a 10.0 year storm
Decimal fraction soil group A = 1.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[MEDIUM DENSITY RESIDENTIAL ]
(7.3 DU/A or Less )
Impervious value, Ai = 0.400
Sub-Area C Value = 0.480
Time of concentration = 13.48 min.
Rainfall intensity = 2.363(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.480 CA = 2.491
Subarea runoff = 4.731(CFS) for 4.220(Ac.)
Total runoff = 5.887(CFS) Total area = 5.190(Ac.)
3
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 502.000 to Point/Station 503.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 47.000(Ft.)
Downstream point/station elevation = 30.000(Ft.)
Pipe length = 60.00(Ft.) Slope = 0.2833 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 5.887(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 5.887(CFS)
Normal flow depth in pipe = 5.38(In.)
Flow top width inside pipe = 8.83(In.)
Critical depth could not be calculated.
Pipe flow velocity = 21.35(Ft/s)
Travel time through pipe = 0.05 min.
Time of concentration (TC) = 13.52 min.
End of computations, total study area = 5.190 (Ac.)
GRAPHIC SCALE
1000 0 500 1000
~--liiiiiiiiii ~1~1
1 INCH = 500 FEET
LEGEND:
- -MAJOR DRAINAGE BASIN BOUNDARY
I •• •• NATURAL FLOW PATH
~ HYDROMODIFICATION EXEMPT AREA
HMP EXEMPTION EXHIBIT