HomeMy WebLinkAboutSDP 2019-0014; CARLSBAD OAKS NORTH LOT 2; PRIORITY PROJECT HYDROLOGY STUDY; 2020-06-01PRIORITY PROJECT
HYDROLOGY STUDY
FOR:
CARLSBAD OAKS NOR THLOT 2
CARLSBAD, CA
PREPARED FOR:
Carlsbad Oaks North Ventures LP
CIO Techbilt Companies
3575 Kenyon Street - Suite 200
San Diego, CA 92100
RECEIVED
JUN 03 2020
LAND DEVELOPMENT
ENGINEERING
PREPARED BY:
EXCEL ENGINEERING
440 State Place
Escondido, CA 92029
Tel. (760) 745-8118
Project No. 19-0 79
DATE PREPARED:
June 1, 2020
Hydrology Study
TABLE OF CONTENTS
1.0 Project Description
1.1 Project Purpose
1.2 Project Proposed facilities
2.0 Vicinity Map
3.0 Site Map
4.0 Description of Watershed
4.1 Existing Conditions Topography
4.2 Existing Conditions + Project Conditions Topography
4.3 Hydrologic Unit Contribution
5.0 Methodology
5.1 Hydrology Software
5.2 Routing Software
5.3 Hydraulics Software
6.0 Calculations
6.1 Determine the Watershed that affects the project
6.2 Calculate Runoff Coefficient
6.3 Calculate Storm Flows using the Rational Method
7.0 Mitigation Measures
7.1 Mitigation of Increased Runoff
7.2 Check Capacity of Existing Downstream Storm Drain Facilities
8.0 Summary
9.0 References
10.0 Declaration of Responsible Charge
11.0 Attachments
Attachment A - Site Map
Attachment B - Figures & Tables from the SD Hydrology Manual 2003
Attachment C - Watershed Information
Watershed Map
Soils Index Map
Rainfall Isopluvial Maps
Attachment D - Previously Approved Improvement Plans
Attachment E - Post Developed Q Calculations
Attachment F - Post Developed Hydrology Map
Hydrology Study
1.0 PROJECT DESCRIPTION
1.1 Project Purpose
The purpose of this project is to receive approval from the City of Carlsbad on a
Site Development Plan (Minor) to construct a parking lot in Lot 2 as well as the
associated infrastructure and improvements on existing 7.52 acre parcel.
1.2 Project Proposed Facifities
The project is proposing to build a parking lot with a total of 191,239 square feet
of AC pavement. As part of this project, associated improvements will include the
343 parking spaces and 10% of the site will be landscaped throughout the parking
areas, slopes and, frontages. All necessary utilities (storm, sewer, water, dry, etc.)
will be installed as part of the project and tie into existing stubs provided for the
site by City of Carlsbad DWG No. 415-9.
Normal uses of such a development will generate storm water runoff with the
potential to carry pollutants to off-site tributaries. Biofiltration basins are planned
to be incorporated throughout the site to treat and detain runoff from impervious
and landscaped areas.
Carlsbad Oaks North Ventures LP C/O TechBilt Companies is the recorded
owner of the project sites.
Hydrology Study
northeast corner of the site (installed as part of the Carlsbad Oaks mass grading
operations).
Once collected in this desiltation basin, the runoff flows through an existing storm
drainage pipe to an existing storm drain structure that outlets into a storm
drainage detention basin formed by the intersection of Faraday Avenue and El
Fuerte Street (as referenced and designed in the Rancho Carlsbad Channel &
Basin Project Hydrology Study, by Rick Engineering - circa 1985). Once
released from the detention basin (installed and sized to detain the future Carlsbad
Oaks Business Park 100-year flows as well as runoff from the construction of
Faraday Avenue) the flows are discharged into Agua Hedionda Creek baèk to the
north of Faraday Avenue and ultimately Agua Hedionda Lagoon and the Pacific
Ocean. This represents the Carlsbad Hydrologic Unit, Aqua Hedionda HA, Los
Monos HSA (904.31).
4.2 Existing Conditions + Project Conditions Topography
The Carlsbad Oaks Lots 2 Industrial project layout proposes to install a large
parking field across the site. The main drive aisle accessing the site from El
Fuerte Street at the southeastern end of the site. The parking lot drains north east
towards the biofiltration systems. Once within the water quality treatment
systems, the stormwater infiltrates through the treatment medium into underdrains
that route the flows to the private onsite storm drainage system. This system uses
new piping to direct the flows to the existing storm drain structure installed as part
of the Carlsbad Oaks Business Park project and ties into the existing storm
drainage system within El Fuerte Street heading north toward its outfall location.
As calculated below, and summarized further in Section 8, Lot 2 discharges peak
100-year flows at less than those shown on DWG No. 415-9E. On Sheet 8 of that
drawing set, the Lot 2 project pipe flowrate is shown as 29.65 CFS being
conveyed into the main storm drain. The existing infrastructure was sized
assuming the Carlsbad Oaks Business Park pads (CT 97-13) were to be developed
at a high C-factor to account for the development of the lots into industrial use.
The original mass grading relied on the Rancho Carlsbad Channel & Basin
Project Hydrology Study to detain the flows once they were discharged across
Faraday Avenue. Drainage patterns and basin areas have been detailed and are
further shown in the Attachments on the Post-Development Hydrology Basin
Map. The proposed condition flowrate is 29.30 CFS, less than the allowable
29.65 CFS.
4.3 Hydrologic Unit Contribution
The project site is within the Carlsbad Hydrologic Unit, Agua Hedionda HA, Los
Monos HSA (904.31). After drainage leaves the site, it flows northeast into Agua
Hedionda Creek. After undergoing detention at the control facility located at the
intersection of Faraday Aventie and El Fuerte Street the flow then continues along
4
Hydrology Study
Agua Hedionda Creek towards Agua Hedionda Lagoon and the Pacific Ocean
south of Tamarack.
5.0 METHODOLOGY
This study complies with the 2003 San Diego Hydrology Manual. The rational
method as presented in Section 3 of that manual and workbook examples were
followed.
5.1 Hydrology Software
The "Rational Hydrology Method, San Diego County (2003 Manual)" module of
the CIVILCADD/CIVIL DESIGN Engineering software version 7.9 is used in
this study. This software was also used to developed hydrographs from the
rational method results. This procedure also complies with the 2003 San Diego
Hydrology Manual as presented in Section 6.
5.2 Routing Software
No routing calculations were performed for this site at this time. Should further
routing be required upon further development of the site and possible site plan
changes causing discharge rates to increase above the predeveloped rates, the
existing hydromodification/water quality treatment ponds can be used as flow
control facilities. In order to show this is the case, Hydraflow Hydrographs 2004
by Intelisolve would then be used in this step. The hydrograph developed from the
rational method is then manually entered into this software and routed into each
detention pond.
5.3 Hydraulics Software
The hydraulics calculations were performed on the Hydaflow Express Extension
v.10.4 ht1i://www.autodesk.com/civi13d-stormwater.
For the pipe flows on Lot 2 no increase in flows being released from the private
storm drainage system at the single discharge point at the southwest corner of the
site are expected versus the mass-graded (pre-developed) conditions that the
infrastructure was designed for. Therefore, all downstream effects from
stormwater velocities have already been accounted for by the reports and the
plans approved for construction of the original Carlsbad Oaks Business Park
infrastructure.
6.0 CALCULATIONS
One hydrologic calculation will be done at this stage. Due to the 100-year peak
flowrates already being determined for existing conditions as part of DWG No.
415-9, the only calculation to be done as part of this report is the 100-year
flowrates expected from the postdeveloped conditions. These numbers will be
used to size the proposed storm drain pipes and to doublecheck if the existing
storm drain outlet facilities are adequate. Since this project met all conditions
within the parameters of the software used, no further hydraulic calculations were
Hydrology Study
6.1 Determine the Watershed that affects the project
Please see the "Watershed Map" in Attachment C
6.2 Calculate Runoff Coefficient
Based on NRCS maps show that this project site is in type "D" soil. The previous
hydrology calculations done as part of the Carlsbad Oaks infrastructure and mass
grading operation also showed type "D" soils. Therefore, we are going to use all
coefficients for that type of soil. As stated in section 3.1.2 of the San Diego
Hydrology Manual on the second paragraph, "impervious percentage (%
Impervious) as given in Table 3-1 for any area, shall govern the selected value for
D."
For all areas to remain pervious post-construction a "c" factor of c=0.35 is used.
The remainder of the site's "c" factors will be based on the percentage of
imperviousness within that subarea. The Land use chosen from table 3-1 of the
San Diego Hydrology Manual (see attachment B) with a corresponding
impervious area to that land use to be used in the hydrology software.
6.3 Calculate Storm Flows using the Rational Method
The 100-year post developed storm flows were calculated for this project to be
29.30 CFS. These are less than those shown on the approved drawings that
originally developed the pads.
Please see "Post Developed Q Calculations" in Attachment E for the developed
conditions.
7.0 MITIGATION MEASURES
A Storm Water Quality Management Plan (SWQMP) has been prepared for this
project to discuss treatment and flow control of the lower flows (2-year and 10-
year). This Hydrology study analyzes the higher 100-year flows.
7.1 Mitigate Increase Runoff
As discussed above, the postdeveloped runoff rate is 29.30 CFS for Lot 2 at the
outfall in El Fuerte Street. The flowrate shown on DWG No. 415-9 downstream
of this project's collection point is 29.65 CFS for Lot 2 (see Attachment D). The
proposed site development decreases the expected peak flows and therefore no
further mitigation is required.
7.2 Check Capacity of Existing Downstream Storm Drain Facilities
Since peak flows are reduced, no further capacity analysis of downstream storm
drain facilities is necessary.
Hydrology Study
8.0 SUMMARY
This project will not negatively impact the existing downstream storm drain facilities.
The resulting 100-year flowrates from the proposed development are less than those
calculated and accounted for as part of the Carlsbad Oaks Business Park project (CT 97-
13) where pads were graded out and infrastructure installed to account for the expected
development type that this site conforms to.
9.0 REFERENCES
County of San Digo, Department of Public Works, Flood Control Section, June 2003
San Diego County Hydrology Manual
Hydrology Study
10.0 DECLARATION OF RESPONSIBLE CHARGE
I hereby declare that I am the engineer of work for this project. That I have exercised
responsible charge over the design of the project as defined in section 6703 of the
business and professions codes, and that the design is consistent with current design.
I understand that the check of the project drawings and specifications by the City of
Carlsbad is confined to a review only and does not relieve me, as engineer of work, of my
responsibilities for project design.
ENGINEER OF WORK
Excel Engineering
440 State Place
Escondido, CA 92029
Tel - (760)745-8118
Fax - (760)745-1890
Project Number: 19-079
$FES
D.
No. 456 o)
6/1/2020
Robert Vt)entino, RCE 45629 Date
Registration Expire: December 31, 2020
Hydrology Study
ATTACHMENT B
FIGURES & TABLES FROM THE SD HYDROLOGY MANUAL 2003
Hydrology Study
ATTACHMENT C
WATERSHED INFORMATION
Soils Index Map
Point Rainfall Isophivial maps
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Hydrology Study
ATTACHMENT D
PREVIOUSLY APPROVED IMPROVEMENT PLANS
Hydrology Study
ATTACHMENT E
POST DEVELOPED Q CALCULATIONS
Steps Taken To Analyze This Condition
The Rational Method as outlined in section 3 of the June 2003 San Diego County
Hydrology Manual is followed here. The software that we are using is the "Rational
Hydrology Method, San Diego County (2003 Manual)" module of the
CIVILCADD/CIVIL DESIGN Engineering software version 7.9.
Please see the subsequent pages for the calculations. These calculations are for the Qi 00.
The results are outlined/summarized in Section 8.
San Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software, (c)1991-2014 Version 9.0
Rational method hydrology program based on
San Diego County Flood Control Division 2003 hydrology manual
Rational Hydrology Study Date: 05/29/20 ------------------------------------------------------------------------
19079 POST DEVELOPMENT 100 YEAR
CARLSBAD OAKS NORTH LOT 2
Hydrology Study Control Information
------------------------------------------------------------------------
Program License Serial Number 6332
------------------------------------------------------------------------
Rational hydrology study storm event year is 100.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 2.750
24 hour precipitation(inches) = 5.300
P6/P24 = 51.9%
San Diego hydrology manual 'C' values used
Process from Point/Station 101.000 to Point/Station 102.000
INITIAL AREA EVALUATION ****
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
[COMMERCIAL area type
(General Commercial
Impervious value, Ai = 0.850'
Sub-Area C Value = 0.820
Initial subarea total flow distance = 110.000(Ft.)
Highest elevation 270.250 (Ft.)
Lowest elevation = 267.220(Ft.)
Elevation difference = 3.030(Ft.) Slope = 2.755 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 85.00 (Ft)
for the top area slope value of 2.75 %, in a development type of
General Commercial
In Accordance With Figure 3-3
Initial Area Time of Concentration = 3.31 minutes
TC = [1.8*(1.1_C)*distance(Ft.).5)/(% slope(1/3))
TC= [1.8*(1.1_0.8200)*( 85.000.5)/( 2.755(1/3)1= 3.31
Calculated TC of 3.315 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 7.246(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.820
Subarea runoff - 0.772(CFS)
Total initial stream area = 0.130(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 102.000 to Point/Station 103.000
IRREGULAR CHANNEL FLOW TRAVEL TIME
Estimated mean flow rate at midpoint of channel - 9.197(CFS)
Depth of flow - 0.275(Ft.), Average velocity = 2.332(Ft/s)
Irregular Channel Data
Information entered for subchannel number 1
Point number 'X' coordinate 'Y' coordinate
CARLSBAD OAKS NORTH 1012
Page lof 10
1 0.00 1.13
2 13.00 0.27
3 40.00 0.13
4 42.50 0.00
5 45.00 0.13
6 184.00 1.80
Manning's 'N' friction factor = 0.013 -----------------------------------------------------------------
Sub-Channel flow = 9.197(CFS)
flow top width = 44.131 (Ft.)
velocity= 2.332(Ft/s)
area = 3.944(Sq.Ft)
Froude number - 1.375
Upstream point elevation - 267.220 (Ft.)
Downstream point elevation = 260.000(Ft.)
Flow length 693.000(.Ft.)
Travel time = 4.95 mm.
Time of concentration = 8.27 mm.
Depth of flow = 0.275(Ft.)
Average velocity = 2.332(Ft/s)
Total irregular channel flow = 9.197(CFS)
Irregular channel normal depth above invert elev. = 0.275 (Ft.)
Average velocity of channel(s) = 2.332(Ft/s)
Adding area flow to channel
Rainfall intensity (I) = 5.238(In/Hr) for a 100.0 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
(COMMERCIAL area type
(General Commercial
Impervious value, Ai = 0.850
Sub-Area c Value = 0.820
Rainfall intensity = 5.238(In/Hr) for a 100.0 year Storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.820 CA = 3.353
Subarea runoff = 16.792(CFS) for 3.959(Ac.)
Total runoff - 17.564(CFS) Total area = 4.089(Ac.)
Depth of flow = 0.320(Ft.), Average velocity - 2.907(Ft/s)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 103.000 to Point/Station 103.000
** SUBAREA FLOW ADDITION ****
Rainfall intensity (I) - 5.238(In/Hr) for a 100.0 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
(COMMERCIAL area type
(General Commercial
Impervious value, Ai = 0.850
Sub-Area C Value 0.820
Time of concentration 8.27 mm.
Rainfall intensity = 5.238(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q-KCIA) is C = 0.820 CA = 4.063
Subarea runoff 3.720(CFS) for 0.866(Ac.)
Total runoff = 21.284(CFS) Total area = 4.955(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 103.000 to Point/Station 103.000
**** CONFLUENCE OF MAIN STREAMS ****
The following data inside Main Stream is listed:
In Main Stream number: 1
Stream flow area = 4.955(Ac.)
Runoff from this stream = 21 .284 (CFS)
CARLSBAD OAKS NORTH LOT 2
Page 2 of 10
Time of concentration = 8.27 mm.
Rainfall intensity = 5.238(In/Hr)
Program is now starting with Main Stream No. 2
Process from Point/Station 201.000 to Point/Station 202.000
INITIAL AREA EVALUATION ****
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
[COMMERCIAL area type
(General Commercial
Impervious value, Ai = 0.850
Sub-Area C Value = 0.820
Initial subarea total flow distance = 77.000(Ft.)
Highest elevation = 266.220(Ft.)
Lowest elevation = 265.170(Ft.)
Elevation difference - 1.050(Ft.) Slope - 1.364 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 60.00 (Ft)
for the top area slope value of 1.36 %, in a development type of
General Commercial
In Accordance With Figure 3-3
Initial Area Time of Concentration = 3.52 minutes
TC = (1.8*(1.1_C)*distance(Ft.).5)/(% s1ope(1/3)]
TC - (1.8*(1.1_0.8200)*( 60.000.5)/( 1.364(1/3)1= 3.52
Calculated TC of 3.520 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 7.246(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.820
Subarea runoff = 0.784(CFS)
Total initial stream area = 0.132(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 202.000 to Point/Station 203.000
IRREGULAR CHANNEL FLOW TRAVEL TIME ****
Estimated mean flow rate at midpoint of channel = 2.454(CFS)
Depth of flow = 0.166(Ft.), Average velocity - 1.745(Ft/s)
Irregular Channel Data ***********
-----------------------------------------------------------------
Information entered for subchannel number 1
Point number 'X' coordinate '1' coordinate
1 0.00 0.84
2 123.50 0.07
3 125.00 0.00
4 126.50 0.07
5 193.00 0.83
Manning's 'N' friction factor - 0.013 -----------------------------------------------------------------
Sub-Channel flow 2.454(CFS)
flow top width - 25.583(Ft.)
velocity= 1.745(Ft/s)
area = 1.406(Sq.Ft)
Froude number = 1.312
Upstream point elevation = 265.170(Ft.)
Downstream point elevation = 263.340 (Ft.)
Flow length 164.000(Ft.)
Travel time = 1.57 mm.
Time of concentration - 5.09 mm.
Depth of flow = 0.166(Ft.)
Average velocity - 1.745(Ft/s)
Total irregular channel flow = 2.454(CFS)
Irregular channel normal depth above invert elev. = 0.166(Ft.)
Average velocity of channel(s) = 1.745(Ft/s)
Adding area flow to channel
CARLSBAD OAKS NORTH LOT 2
Page 3 of 10
Rainfall intensity (I) = 7.166(In/Hr) for a 100.0 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
(COMMERCIAL area type
(General Commercial
Impervious value, Ai = 0.850
Sub-Area C Value = 0.820
Rainfall intensity = 7.166(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q-KCIA) is C = 0.820 CA = 0.569
Subarea runoff 3.294(CFS) for 0.562(Ac.)
Total runoff = 4.078(CFS) Total area = 0.694(Ac.)
Depth of flow = 0.189(Ft.), Average velocity = 1.970(Ft/s)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 203.000 to Point/Station 204.000
IRREGULAR CHANNEL FLOW TRAVEL TIME
Depth of flow = 0.254(Ft.), Average velocity = 10.574(Ft/s)
!Warning: Water is above left or right bank elevations
******* Irregular Channel Data -----------------------------------------------------------------
Information entered for subchannel number 1
Point number 'X' coordinate 'Y' coordinate
1 0.00 0.00
2 1.50 0.13
3 3.00 0.25
Manning's 'N' friction factor = 0.013 -----------------------------------------------------------------
Sub-Channel flow 4.078(CFS)
flow top width = 3.000 (Ft.)
velocity- 10.574(Ft/s)
area - 0.386(Sq.Ft)
Froude number = 5.197
Upstream point elevation = 263.340 (Ft.)
Downstream point elevation = 261.750(Ft.)
Flow length 12.000(Ft.)
Travel time - 0.02 mm.
Time of concentration = 5.11 mm.
Depth of flow = 0.254(Ft.)
Average velocity = 10.574(Ft/s)
Total irregular channel flow 4.078(CFS)
Irregular channel normal depth above invert elev. = 0.254(Ft.)
Average velocity of channel(s) = 10.574(Ft/s)
!Warning: Water is above left or right bank elevations
Process from Point/Station 204.000 to Point/Station 204.000 ** SUBAREA FLOW ADDITION ****
Rainfall intensity (I) - . 7.149(In/Hr) for a 100.0 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
[COMMERCIAL area type
(General Commercial
Impervious value, Ai - 0.850
Sub-Area C Value = 0.820
Time of concentration - 5.11 mm.
Rainfall intensity - 7.149(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q-RCIA) is C = 0.820 CA = 0.655
Subarea runoff = 0.606(CFS) for 0.105(Ac.)
Total runoff = 4.684(CFS) Total area - 0.799(Ac.)
CARLSBAD OAKS NORTH LOT 2
Page 4 of 10
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 204.000 to Point/Station 204.000
CONFLUENCE OF MINOR STREAMS
Along Main Stream number: 2 in normal stream number 1
Stream flow area = 0.799(Ac.)
Runoff from this stream 4.684(CFS)
Time of concentration - 5.11 mm.
Rainfall intensity = 7.149(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 301.000 to Point/Station 302.000 **** INITIAL AREA EVALUATION ****
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
(COMMERCIAL area type
(General Commercial
Impervious value, Ai = 0.850
Sub-Area C Value = 0.820
Initial subarea total flow distance = 56.000(Ft.)
Highest elevation = 264.590(Ft.)
Lowest elevation = 262.500(Ft.)
Elevation difference 2.090(Ft.) Slope = 3.732 %
Top of Initial Area Slope adjusted by User to 4.328 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 90.00 (Ft)
for the top area slope value of 4.33 %, in a development type of
General Commercial
In Accordance With Figure 3-3
Initial Area Time of Concentration = 2.93 minutes
TC = [1.8*(1.1_C)*distance(Ft.)*.5)/(% slope(1/3)J
TC = (1.8*(1.1_0.8200)*( 90.000.5)/( 4.328(1/3)1- 2.93
Calculated TC of 2.934 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) - 7.246(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q-KCIA) is C 0.820
Subarea runoff = 0.267(CFS)
Total initial stream area = 0.045 (Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 302.000 to Point/Station 204.000
PIPEFLOW TRAVEL TIME (User specified size)
Upstream point/station elevation = 261.860(Ft.)
Downstream point/station elevation = 261.750(Ft.)
Pipe length = 23.00(Ft.) Slope = 0.0048 Manning's N - 0.013
No. of pipes = 1 Required pipe flow = 0.267(CFS)
Given pipe size = 4.00(In.)
NOTE: Normal flow is pressure flow in user selected pipe size.
The approximate hydraulic grade line above the pipe invert is
0.562(Ft.) at the headworks or inlet of the pipe(s)
Pipe friction loss = 0.454(Ft.)
Minor friction loss = 0.219(Ft.) K-factor - 1.50
Pipe flow velocity = 3.06(Ft/s)
Travel time through pipe = 0.13 min.
Time of concentration (TC) = 3.06 mm.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 204.000 to Point/Station 204.000
CONFLUENCE OF MINOR STREAMS ****
Along Main Stream number: 2 in normal stream number 2
Stream flow area = 0.045(Ac.)
Runoff from this stream = 0.267(CFS)
CARLSBAD OAKS NORTH LOT 2
Page 5 of 10
Time of concentration = 3.06 mm.
Rainfall intensity = 7.246(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (FS) (mm) (In/Hr)
1 4.684 5.11 7.149
2 0.267 3.06 7.246
Qmax(l) =
1.000 * 1.000 * 4.684) +
0.987 * 1.000 * 0.267) + = 4.948
Qmax(2) =
1.000 * 0.599 * 4.684) +
1.000 * 1.000 * 0.267) + = 3.074
Total of 2 streams to confluence:
Flow rates before confluence point:
4.684 0.267
Maximum flow rates at confluence using above data:
4.948 3.074
Area of streams before confluence:
0.799 0.045
Results of confluence:
Total flow rate = 4.948(CFS)
Time of concentration = 5.105 mm.
Effective stream area after confluence = 0.844 (Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 204.000 to Point/Station 205.000
PIPEFLOW TRAVEL TIME (User specified size) ****
Upstream point/station elevation 258.000(Ft.)
Downstream point/station elevation = 257.890(Ft.)
Pipe length = 23.00(Ft.) Slope = 0.0048 Manning's N = 0.013
No. of pipes 1 Required pipe flow = 4.948(CFS)
Given pipe size = 18.00 (In.)
Calculated individual pipe flow 4.948(CFS)
Normal flow depth in pipe = 10.90(In.)
Flow top width inside pipe = 17.59(m.)
Critical Depth = 10.27(In.)
Pipe flow velocity = 4.42(Ft/s)
Travel time through pipe = 0.09 mm.
Time of concentration (TC) = 5.19 mm.
Process from Point/Station 205.000 to Point/Station 205.000
**** CONFLUENCE OF MINOR STREAMS ****
Along Main Stream number: 2 in normal stream number 1
Stream flow area = 0.844 (Ac.)
Runoff from this stream = 4.948(CFS)
Time of concentration = 5.19 mm.
Rainfall intensity = 7.072(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 401.000 to Point/Station 402.000
INITIAL AREA EVALUATION
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
(UNDISTURBED NATURAL TERRAIN
(Permanent Open Space
Impervious value, Ai = 0.000
Sub-Area C Value 0.350
CARLSBAD OAKS NORTH LOT 2
Page 6 of 10
Initial subarea total flow distance = 106.000(Ft.)
Highest elevation - 300.780(Ft.)
Lowest elevation = 268.190(Ft.)
Elevation difference = 32.590(Ft.) Slope = 30.745 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 30.75 %, in a development type of
Permanent Open Space
In Accordance With Figure 3-3
Initial Area Time of Concentration 4.31 minutes
TC (1.8*(1.1_C)*distance(Ft.).5)/(% slope(1/3)]
TC = (1.8*(1.1_0.3500)*( 100.000.5)/( 30.745(1/3)]= 4.31
Calculated TC of 4.309 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 7.246(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (QKCIA) is C = 0.350
Subarea runoff = 0.203(CFS)
Total initial stream area = 0.080 (Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 402.000 to Point/Station 403.000
IRREGULAR CHANNEL FLOW TRAVEL TIME ****
Estimated mean flow rate at midpoint of channel = 1.663(CFS)
Depth of flow = 0.863(Ft.), Average velocity 2.979(Ft/s)
******* Irregular Channel Data ***********
-----------------------------------------------------------------
Information entered for subchannel number 1
Point number 'X' coordinate 'Y' coordinate
1 0.00 32.50
2 67.00 2.00
3 68.00 0.00
4 69.00 1.00
Manning's 'N' friction factor = 0.015 -----------------------------------------------------------------
Sub-Channel flow = 1.663(CFS)
flow top width 1.294 (Ft.)
velocity= 2.979(Ft/s)
area = 0.558(Sq.Ft)
Froude number - 0.799
Upstream point elevation - 268.190(Ft.)
Downstream point elevation = 263.000 (Ft.)
Flow length = 931.000(Ft.)
Travel time = 5.21 mm.
Time of concentration = 9.52 mm.
Depth of flow - 0.863(Ft.)
Average velocity = 2.979(Ft/s)
Total irregular channel flow = 1.663(CFS)
Irregular channel normal depth above invert elev. = 0.863(Ft.)
Average velocity of channel(s) - 2.979(Ft/s)
Adding area flow to channel
Rainfall intensity (I) = 4.783(In/Hr) for a 100.0 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
[UNDISTURBED NATURAL TERRAIN
(Permanent Open Space
Impervious value, Ai = 0.000
Sub-Area C Value = 0.350
Rainfall intensity = 4.783(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.350 CA - 0.639
Subarea runoff = 2.856(CFS) for 1.747(Ac.)
Total runoff = 3.059(CFS) Total area = 1.827(Ac.)
Depth of flow - 1.076(Ft.), Average velocity = 3.536(Ft/s)
CARLSBAD OAKS NORTH LOT 2
Page 7 of 10
Process from Point/Station 403.000 to Point/Station 205.000 PIPEFLOW TRAVEL TIME (User specified size) ****
Upstream point/station elevation = 260.400(Ft.)
Downstream point/station elevation = 260.040(Ft.)
Pipe length = 72.00(Ft.) Slope - 0.0050 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 3.059(CFS)
Given pipe size 18.00 (In.)
Calculated individual pipe flow - 3.059(CFS)
Normal flow depth in pipe = 8.05(In.)
Flow top width inside pipe = 17.90(In.)
Critical Depth = 7.97 (In.)
Pipe flow velocity = 4.00(Ft/s)
Travel time through pipe - 0.30 mm.
Time of concentration (TC) = 9.82 mm.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 205.000 to Point/Station 205.000 **** CONFLUENCE OF MINOR STREAMS
Along Main Stream number: 2 in normal stream number 2
Stream flow area = 1.827(Ac.)
Runoff from this stream = 3.059(CFS)
Time of concentration - 9.82 mm.
Rainfall intensity = 4.689(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (mm) (In/Hr)
1 4.948 5.19 7.072
2 3.059 9.82 4.689
Qmax(1) =
1.000 1.000 * 4.948) +
1.000 * 0.529 * 3.059) + = 6.565
Qmax(2) -
0.663 * 1.000 * 4.948) +
1.000 * 1.000 * 3.059) + = 6.339
Total of 2 streams to confluence:
Flow rates before confluence point:
4.948 3.059
Maximum flow rates at confluence using above data:
6.565 6.339
Area of streams before confluence:
0.844 1.827
Results of confluence:
Total flow rate = 6.565(CFS)
Time of concentration = 5.192 mm.
Effective stream area after confluence - 2.671 (Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 205.000 to Point/Station 206.000
PIPEFLOW TRAVEL TIME (User specified size) ****
Upstream point/station elevation = 257.790(Ft.)
Downstream point/station elevation = 255.870 (Ft.)
Pipe length = 384.00(Ft.) Slope = 0.0050 Manning's N = 0.013
No. of pipes 1 Required pipe flow = 6.565(CFS)
Given pipe size = 18.00 (In.)
Calculated individual pipe flow = 6.565(CFS)
Normal flowdepth in pipe - 13.15(In.)
Flow top width inside pipe - 15.97(In.)
Critical Depth = 11.88 (In.)
Pipe flow velocity = 4.75(Ft/s)
Travel time through pipe = 1.35 mm.
Time of concentration (TC) 6.54 mm.
CARLSBAD OAKS NORTH 1012
Page 8 of 10
Process from Point/Station 206.000 to Point/Station 103.000 PIPEFLOW TRAVEL TIME (User specified size) ****
Upstream point/station elevation - 253.500(Ft.)
Downstream point/station elevation = 253.150(Ft.)
Pipe length = 71.00(Ft.) Slope = 0.0049 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 6.565(CFS)
Given pipe size = 18.00(m.)
Calculated individual pipe flow - 6.565(CFS)
Normal flow depth in pipe = 13.22(m.)
Flow top width inside pipe = 15.90(In.)
Critical Depth = 11.88(In.)
Pipe flow velocity = 4.72(Ft/s)
Travel time through pipe = 0.25 mm.
Time of concentration (TC) = 6.79 mm.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 103.000 to Point/Station 103.000
** CONFLUENCE OF MAIN STREAMS ****
The following data inside Main Stream is listed:
In Main Stream number: 2
Stream flow area = 2.671(Ac.)
Runoff from this stream = 6.565(CFS)
Time of concentration = 6.79 mm.
Rainfall intensity = 5.947(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (mm) (In/Hr)
1 21.284 8.27 5.238
2 6.565 6.79 5.947
Qmax(1)
1.000 * 1.000 * 21.284) +
0.881 * 1.000 * 6.565) + 27.067
Qmax(2) =
1.000 * 0.821 * 21.284) +
1.000 * 1.000 * 6.565) + 24.049
Total of 2 main streams to confluence:
Flow rates before confluence point:
21.284 6.565
Maximum flow rates at confluence using above data:
27.067 24.049
Area of streams before confluence:
4.955 2.671
Results of confluence:
Total flow rate = 27.067(CFS)
Time of concentration = 8.268 mm.
Effective stream area after confluence = 7.626(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 103.000 to Point/Station 104.000 PIPEFLOW TRAVEL TIME (User specified size) ****
Upstream point/station elevation = 242.530(Ft.)
Downstream point/station elevation = 239.000(Ft.)
Pipe length = 39.00(Ft.) Slope = 0.0905 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 27.067(CFS)
Given pipe size = 30.00 (In.)
Calculated individual pipe flow = 27.067(CFS)
Normal flow depth in pipe = 9.54(In.)
Flow top width inside pipe = 27.95(In.)
CARLSBAD OAKS NORTH LOT 2
Page 9 of 10
Critical Depth = 21.28(m.)
Pipe flow velocity = 20.15(Ft/s)
Travel time through pipe = 0.03 mm.
Time of concentration (TC) = 8.30 mm.
Process from Point/Station 104.000 to Point/Station 104.000 **** SUBAREA FLOW ADDITION ****
Rainfall intensity (I) = 5.225(In/Hr) for a 100.0 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
[LOW DENSITY RESIDENTIAL
(1.0 DO/A or Less
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Time of concentration 8.30 mm.
Rainfall intensity = 5.225(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.690 CA = 5.594
Subarea runoff = 2.162(CFS) for 0.486(Ac.)
Total runoff = 29.229(CFS) Total area = 8.112(Ac.)
End of computations, total study area = 8.112 (Ac.)
CARLSBAD OAKS NORTH 1012
Page 10 of 10
Hydrology Study
ATTACHMENT F•
POST DEVELOPED HYDROLOGY MAP
-
1
LEGEND
WATERCOURSE
WATERSHED BOUNDARY N SUB—AREA BOUNDARY -------- --
NODE NUMBER
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CARLSBAD OAKS LOT 2
POST DEVELOPMENT