HomeMy WebLinkAboutSDP 16-12; HARDING VETERANS HOUSING; DRAINAGE REPORT; 2020-07-14DRAINAGE REPORT
FOR
HARDING VETERANS HOUSING
(SDP 16-12, GR 2020-0007, Drawing No. 5234A)
July 14, 2020
REco RD COPY
-11-141
-- -1-Initial
ffNo. 46548?
Exp. 6/30/21
*1.. Wayne W. Chang, S, PE 46548
chaml*mmm
Civil Engineering. Hydrology. Hydraulics Sedimentation
P.O. Box 9496
Rancho Santa Fe, CA 92067
(858) 692-0760
RECFIVED
JUL 2 0 2020
LAND DEVELOPMENT
ENGNEER1NG
TABLE OF CONTENTS
Introduction .
Hydrologic and Hydraulic Analyses..................................................................................................2
Conclusion.........................................................................................................................................3
APPENDICES
A. 100-Year Rational Method Analyses and Supporting Data
INTRODUCTION
The Harding Veterans Housing project is located at 3606, 3618, and 3630 Harding Street in the
city of Carlsbad (see the Vicinity Map). The project proposes 26 veterans' housing units on a
0.543 acre site. The project will contain a three-story building with a ground level parking
structure, hardscape, and landscaping. The site is currently developed with three single-family
residences, which will be demolished prior to development. A site development plan (SDP) was
approved during entitlements. The project is currently in the final engineering phase and the
grading plans are being prepared by Kettler Leweck Engineering.
CITY OF OCEANSIDE ____
5) -
HIGHWAY 78
DR.
[J:Ti:fi:i & II
ALOMAR00
PACIFIC
OCEAN
Vicinity Map
This report contains the final engineering hydrologic and hydraulic analyses. The analyses
include pre- (existing condition) and post-project (proposed condition) 100-year hydrologic
analyses as well as hydraulic analyses of the proposed private storm drain system.
HYDROLOGIC AND HYDRAULIC ANALYSES
Hydrologic analyses were performed to determine the 100-year flow rates under pre- and post-
project conditions. The County of San Diego's 2003 Hydrology Manual rational method
procedure was used for the 100-year hydrologic analyses since the overall drainage areas are less
than an acre. The rational method input parameters are summarized below and the supporting
data is included in Appendix A:
Precipitation: The 100-year, 6- and 24-hour precipitation values are 2.60 and 4.50 inches,
respectively.
Drainage areas: The drainage basins were delineated from the base topography prepared for
the project and grading plans by Kettler Leweck Engineering as well as roof drainage
information provided by the architect. The existing and proposed condition overall drainage
basins were set equal to allow a comparison of results.
Hydrologic soil groups: The hydrologic soil groups were determined from the Natural
Resources Conservation Service's (NRCS) Web Soil Survey. The soil group in the study
area is entirely type B.
Runoff coefficients: The runoff coefficients were based on the existing and proposed
condition impervious percentages outlined in the County Hydrology Manual. Under existing
conditions, the overall on-site drainage area is 33 percent impervious, so the low density
residential (4.3 DU/A or 30 percent) category was assumed, which will yield conservative
(lower) results. Under proposed conditions, the overall on-site drainage area is .60 percent
impervious, so the high density residential (24.0 DU/A or 65 percent) category was
assumed, which will yield conservative (higher) results.
Flow lengths and elevations: The flow lengths and elevations were obtained from the base
topography and engineering plans.
Table I summarizes the 100-year rational method results. The table indicates that the project will
cause a 1.6 cfs increase in the 100-year flow rate. The actual increase will be less if the effects of
the seven proposed biofiltration basins is considered. Therefore, the project will have minimal
impacts on storm runoff.
Condition C I, in/hr A, ac Qioo, cfs
Existing (Node 14) 0.45 4.63 0.65 1.4
Proposed (Node 44) 0.67 6.85 0.65 3.0
Table 1. Rational Method Analyses
The on-site storm drain system is private. Normal depth hydraulic analyses for sizing of the
private storm drain pipes are provided by the "pipeflow" routines in the proposed condition
CivilDesign Rational Method output. This is the typical procedure for private storm drain pipes.
The private storm drains are being designed based on the normal depth results.
CONCLUSION
Hydrologic and hydraulic analyses have been performed for final engineering of the Harding
Veterans Housing project. The analyses were based on grading plans by Kettler Leweck
Engineering as well as the architects input on roof drainage. The site is small at just over 0.5
acres, so the resulting flow increase will be small and further mitigated by the seven biofiltration
basins.
3
APPENDIX A
100-YEAR RATIONAL METHOD ANALYSES
AND SUPPORTING DATA
En In County of San Diego
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San Diego County Hydrology Manual Section: 3
Date: June 2003 Page: 6 of 26
Table 3-1
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use Runoff Coefficient "C"
Soil Type
NRCS Elements County Elements % 1MPER. A Th C D
Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 0.35
Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 0.36 0.41
Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 0.42 0.46
Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49
Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 0.48 0.52
Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57
Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 0.57 0.60
Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 0.60 0.63
High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71
High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79
Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0.78 0.79
Commercial/Industrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82
Commercial/Industrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84 0.84 0.85
Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85
Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 0.87 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
Hydrologic Soil Group—San Diego County Area, California
33°9'23N
: \
339'23N
IN Xll
O\
GIll
FJ
T '
t
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33916 N A & \ \ \ 33916 N
468370 4684453 4b652(J
Map Scale: 1:1,3 printed onA landscape (11x8.5")sheet
Meters N 0 20 40 80 120 A Feet ,\\ o 50 10) 200 300
Map projection : Web Mercator Corner coordinates: WGS84 Edge tics: IJThI Zone uN WGS94
USDA Natural Resources Web Soil Survey 5/4/2016
am Conservation Service National Cooperative Soil Survey Page 1 of 4
Hydrologic Soil Group—San Diego County Area, California
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit - San Diego County Area, California (CA638)
Map unit symbol Map unit name Rating Acres In AOl Percent of AOl
( Marina loamy coarse
sand, 2 to percent
slopes
() 7.6 100.0%
Totals for Area of Interest 7.6 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and 0) and
three dual classes (AID, BID, and CID). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay layer
at or near the surface, and soils that are shallow over nearly impervious material.
These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (AID, BID, or do), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
USDA Natural Resources Web Soil Survey 5/4/2016
Conservation Service National Cooperative Soil Survey Page 3 of 4
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: 03/15/20 ------------------------------------------------------------------------
Harding Veterans Housing
Final Engineering
Existing Conditions
100-Tear Storm Event
********* Hydrology Study Control Information **********
Program License Serial Number 4028
------------------------------------------------------------------------
Rational hydrology study storm event year is 100.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 2.600
24 hour precipitation(inches) = 4.500
P6/P24 = 57.8%
San Diego hydrology manual 'C' values used
Process from Point/Station 10.000 to Point/Station 12.000
INITIAL AREA EVALUATION
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
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 = 0.450
Initial subarea total flow distance = 30.000(Ft.)
Highest elevation = 80.200(Ft.)
Lowest elevation = 64.000(Ft.)
Elevation difference = 16.200(Ft.) Slope = 54.000 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 54.00 %, in a development type of
4.3 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 3.10 minutes
TC = (1.8*(1.1_C)*distance(Ft.)A.5)/(% slope A(1/3)]
TC = [1.8*(1.1_0.4500)*( 100.000".5)/( 54.000"(1/3)]= 3.10
Calculated TC of 3.095 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.450
Subarea runoff = 0.062(CFS)
Total initial stream area = 0.020 (Ac.)
++++++++++•4-+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 12.000 to Point/Station 14.000
IMPROVED CHANNEL TRAVEL TIME
Upstream point elevation = 64.000(Ft.)
Downstream point elevation = 61.700(Ft.)
Channel length thru subarea = 238.000(Ft.)
Channel base width = 2.000(Ft.)
Slope or 'Z' of left channel bank = 50.000
Slope or 'Z' of right channel bank = 50.000
Estimated mean flow rate at midpoint of channel =
Manning's 'N' = 0.040
Maximum depth of channel = 1.000(Ft.)
Flow(q) thru subarea = 0.756(cFS)
Depth of flow = 0.134(Ft.), Average velocity =
Channel flow top width = 15.359(Ft.)
Flow Velocity = 0.65(Ft/s)
Travel time = 6.08 mm.
Time of concentration = 9.18 mm.
Critical depth = 0.090(Ft.)
Adding area flow to channel
Rainfall intensity (I) = 4.630(In/Hr) for a
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
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 = 0.450
0.756(CFS)
0.652 (Ft/s)
100.0 year storm
Rainfall intensity = 4.630(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.450 CA = 0.293
Subarea runoff = 1.293(CFS) for 0.630(Ac.)
Total runoff = 1.354(CFS) Total area = 0.650(Ac.)
Depth of flow = 0.170(Ft.), Average velocity = 0.756(Ft/s)
Critical depth = 0.117 (Ft.)
End of computations, total study area = 0.650 (Ac.)
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: 07/14/20 ------------------------------------------------------------------------
Harding Veterans Housing
Final Engineering
Proposed Conditions
100-Year Storm Event
********* Hydrology Study Control Information **********
Program License Serial Number 4028
------------------------------------------------------------------------
Rational hydrology study storm event year is 100.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 2.600
24 hour precipitation(inches) = 4.500
P6/P24 = 57.8%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 10.000 to Point/Station 12.000
INITIAL AREA EVALUATION
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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 = 0.670
Initial subarea total flow distance = 37.000(Ft.)
Highest elevation = 80.300(Ft.)
Lowest elevation = 64.000(Ft.)
Elevation difference = 16.300(Ft.) Slope = 44.054 %
Top of Initial Area Slope adjusted by User to 51.613 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 51.61 %, in a development type of
24.0 DU/A or Less
3
In Accordance With Figure 3-3
Initial Area Time of Concentration = 2.08 minutes
TC = [1.8*(1.1_C)*distance(Ft.).5)/(% slopeA(1/3))
TC= [1.8*(1.1_0.6700)*( 100.000".5)/( 51.613'(1/3)1= 2.08
Calculated TC of 2.079 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.670
Subarea runoff = 0.046(CFS)
Total initial stream area = 0.010(Ac.)
Process from Point/Station 12.000 to Point/Station 14.000
IMPROVED CHANNEL TRAVEL TIME
Upstream point elevation = 64.000(Ft.)
Downstream point elevation = 62.000(Ft.)
Channel length thru subarea = 56.000(Ft.)
Channel base width = 1.000(Ft.)
Slope or 'Z' of left channel bank = 50.000
Slope or 'Z' of right channel bank = 50.000
Estimated mean flow rate at midpoint of channel = 0.252(CFS)
Manning's 'N' = 0.040
Maximum depth of channel = 1.000(Ft.)
Flow(q) thru subarea = 0.252(CFS)
Depth of flow = 0.070(Ft.), Average velocity = 0.810(Ft/s)
Channel flow top width = 7.960(Ft.)
Flow Velocity = 0.81(Ft/s)
Travel time = 1.15 mm.
Time of concentration = 3.23 mm.
Critical depth = 0.060(Ft.)
Adding area flow to channel
Calculated TC of 3.232 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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 = 0.670
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.067
Subarea runoff = 0.413(CFS) for 0.090(Ac.)
Total runoff = 0.459(CFS) Total area = 0.100(Ac.)
Depth of flow = 0.089(Ft.), Average velocity = 0.941(Ft/s)
Critical depth = 0.079(Ft.)
4
Process from Point/Station 14.000 to Point/Station 16.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 56.940(Ft.)
Downstream point/station elevation = 56.280(Ft.)
Pipe length = 76.90(Ft.) Slope = 0.0086 Manning's N 0.013
No. of pipes = 1 Required pipe flow = 0.459(CFS)
Nearest computed pipe diameter = 6.00(m.)
Calculated individual pipe flow = 0.459(CFS)
Normal flow depth in pipe = 4.38(In.)
Flow top width inside pipe = 5.32(In.)
Critical Depth = 4.14(In.)
Pipe flow velocity = 2.99(Ft/s)
Travel time through pipe = 0.43 mm.
Time of concentration (TC) = 3.66 mm.
Process from Point/Station 16.000 to Point/Station 16.000
SUBAREA FLOW ADDITION
Calculated TC of 3.660 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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 = 0.670
Time of concentration = 3.66 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.141
Subarea runoff = 0.505(CFS) for 0.110(Ac.)
Total runoff = 0.964(CFS) Total area = 0.210(Ac.)
Process from Point/Station 16.000 to Point/Station 18.000
"'' PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 56.280(Ft.)
Downstream point/station elevation = 56.000(Ft.)
Pipe length = 27.39(Ft.) Slope = 0.0102 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 0.964(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 0.964(CFS)
5
Normal flow depth in pipe = 4.90(In.)
Flow top width inside pipe = 8.96(In.)
Critical Depth = 5.40(In.)
Pipe flow velocity = 3.92(Ft/s)
Travel time through pipe = 0.12 mm.
Time of concentration (TC) = 3.78 mm.
Process from Point/Station 18.000 to Point/Station 18.000
SUBAREA FLOW ADDITION
Calculated TC of 3.777 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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 = 0.670
Time of concentration = 3.78 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.154
Subarea runoff = 0.092(CFS) for 0.020(Ac.)
Total runoff = 1.056(CFS) Total area = 0.230(Ac.)
+++++++++++++.+.++++++++++++..+.+++++.+.+++.++.+.+++++++++++++++++++++
Process from Point/Station 18.000 to Point/Station 20.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 56.000(Ft.)
Downstream point/station elevation = 55.000(Ft.)
Pipe length = 92.03(Ft.) Slope = 0.0109 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.056(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.056(CFS)
Normal flow depth in pipe = 5.09(In.)
Flow top width inside pipe = 8.92(In.)
Critical Depth = 5.66(In.)
Pipe flow velocity = 4.10(Ft/s)
Travel time through pipe = 0.37 mm.
Time of concentration (TC) = 4.15 mm.
Process from Point/Station 20.000 to Point/Station 20.000
SUBAREA FLOW ADDITION
Calculated TC of 4.151 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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, Al = 0.650
Sub-Area C Value = 0.670
Time of concentration = 4.15 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.181
Subarea runoff = 0.184(CFS) for 0.040(Ac.)
Total runoff = 1.239(CFS) Total area = 0.270(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 22.000 to Point/Station 20.000
SUBAREA FLOW ADDITION
Calculated TC of 4.151 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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, Al = 0.650
Sub-Area C Value = 0.670
Time of concentration = 4.15 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.208
Subarea runoff = 0.184(CFS) for 0.040 (Ac.)
Total runoff = 1.423(CFS) Total area = 0.310(Ac.)
Process from Point/Station 20.000 to Point/Station 24.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 55.000(Ft.)
Downstream point/station elevation = 54.700(Ft.)
Pipe length = 29.63(Ft.) Slope = 0.0101 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.423(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.423(CFS)
Normal flow depth in pipe = 6.40(In.)
Flow top width inside pipe = 8.16(In.)
Critical Depth = 6.60(In.)
Pipe flow velocity = 4.23(Ft/s)
Travel time through pipe = 0.12 mm.
Time of concentration (TC) = 4.27 mm.
+++++++++++++++++++++++++++++++++++++.++++++++++++++++++++++++++++++++
Process from Point/Station 20.000 to Point/Station 24.000
CONFLUENCE OF MINOR STREAMS
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 0.310(Ac.)
Runoff from this stream = 1.423(CFS)
Time of concentration = 4.27 mm.
Rainfall intensity = 6.850(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 30.000 to Point/Station 32.000
INITIAL AREA EVALUATION
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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 = 0.670
Initial subarea total flow distance = 30.000(Ft.)
Highest elevation = 78.200(Ft.)
Lowest elevation = 64.000(Ft.)
Elevation difference = 14.200(Ft.) Slope = 47.333 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 47.33 %, in a development type of
24.0 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 2.14 minutes
TC = [1.8* (1.1-C) *distance(Ft. ) ".5) /(% slope" (1/3)]
TC= [1.8-(1.1-0.6700)-( 100.000-.5)/( 47.333"(1/3)1= 2.14
Calculated TC of 2.140 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.670
Subarea runoff = 0.046(CFS)
Total initial stream area = 0.010(Ac.)
8
+++++++++++++++++++++++++++++++++++++++++++++++-f++++++++++++++++++++++
Process from Point/Station 32.000 to Point/Station 34.000
r IMPROVED CHANNEL TRAVEL TIME
Upstream point elevation = 64.000(Ft.)
Downstream point elevation = 62.660(Ft.)
Channel length thru subarea = 40.000(Ft.)
Channel base width = 1.000(Ft.)
Slope or 'Z' of left channel bank = 50.000
Slope or 'Z' of right channel bank = 50.000
Estimated mean flow rate at midpoint of channel = 0.482(CFS)
Manning's 'N' = 0.040
Maximum depth of channel = 1.000(Ft.)
Flow(q) thru subarea = 0.482(CFS)
Depth of flow = 0.092(Ft.), Average velocity = 0.931(Ft/s)
Channel flow top width = 10.226(Ft.)
Flow Velocity = 0.93(Ft/s)
Travel time = 0.72 mm.
Time of concentration = 2.86 mm.
Critical depth = 0.080(Ft.)
Adding area flow to channel
Calculated TC of 2.856 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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 = 0.670
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.134
Subarea runoff = 0.872(CFS) for 0.190(Ac.)
Total runoff = 0.918(CFS) Total area = 0.200(Ac.)
Depth of flow = 0.120(Ft.), Average velocity = 1.094(Ft/s)
Critical depth = 0.106(Ft.)
Process from Point/Station 34.000 to Point/Station 36.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 56.840(Ft.)
Downstream point/station elevation = 55.700(Ft.)
Pipe length = 111.56(Ft.) Slope = 0.0102 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 0.918(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 0.918(CFS)
Normal flow depth in pipe = 4.76(In.)
9
Flow top width inside pipe = 8.99(In.)
Critical Depth = 5.27(In.)
Pipe flow velocity = 3.87(Ft/s)
Travel time through pipe = 0.48 mm.
Time of concentration (TC) = 3.34 mm.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 36.000 to Point/Station 36.000
SUBAREA FLOW ADDITION
Calculated TC of 3.336 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
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 = 0.670
Time of concentration = 3.34 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.188
Subarea runoff = 0.367(CFS) for 0.080(Ac.)
Total runoff = 1.285(CFS) Total area = 0.280 (Ac.)
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-4-++++++++
Process from Point/Station 36.000 to Point/Station 38.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 55.700(Ft.)
Downstream point/station elevation = 55.440(Ft.)
Pipe length = 27.89(Ft.) Slope = 0.0093 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.285(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.285(CFS)
Normal flow depth in pipe = 6.12(In.)
Flow top width inside pipe = 8.40(In.)
Critical Depth = 6.26(In.)
Pipe flow velocity = 4.02(Ft/s)
Travel time through pipe = 0.12 mm.
Time of concentration (TC) = 3.45 mm.
Process from Point/Station 40.000 to Point/Station 38.000
SUBAREA FLOW ADDITION
10
Calculated TC of 3.452 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil arOUD D = 0.000
[HIGH DENSITY RESIDENTIAL
(24.0 DU/A or Less
Impervious value, Ai = 0.650
Sub-Area C Value = 0.670
Time of concentration = 3.45 mm.
Rainfall in = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.214
Subarea runoff = 0.184(CFS) for 0.040(Ac.)
Total runoff = 1.469(CFS) Total area = 0.320(Ac.)
Process from Point/Station 38.000 to Point/Station 24.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 55.440(Ft.)
Downstream point/station elevation = 54.700(Ft.)
Pipe length = 73.65(Ft.) Slope = 0.0100 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.469(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.469(CFS)
Normal flow depth in pipe = 6.59(In.)
Flow top width inside pipe = 7.97 (In.)
Critical Depth = 6.70(In.)
Pipe flow velocity = 4.24(Ft/s)
Travel time through pipe = 0.29 mm.
Time of concentration (TC) = 3.74 mm.
Process from Point/Station 38.000 to Point/Station 24.000
CONFLUENCE OF MINOR STREAMS ****
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 0.320(Ac.)
Runoff from this stream = 1.469(CFS)
Time of concentration = 3.74 mm.
Rainfall intensity = 6.850(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (mm) (In/Hr)
I
1 1.423 4.27 6.850
2 1.469 3.74 6.850
Qmax(1) =
1.000 * 1.000 * 1.423) +
1.000 * 1.000 * 1.469) + = 2.892
Qmax(2) =
1.000 * 0.877 * 1.423) +
1.000 * 1.000 * 1.469) + = 2.716
Total of 2 streams to confluence:
Flow rates before confluence point:
1.423 1.469
Maximum flow rates at confluence using above data:
2.892 2.716
Area of streams before confluence:
0.310 0.320
Results of confluence:
Total flow rate = 2.892(CFS)
Time of concentration = 4.268 mm.
Effective stream area after confluence = 0.630 (Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.+++++
Process from Point/Station 24.000 to Point/Station 42.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 54.700(Ft.)
Downstream point/station elevation = 54.600(Ft.)
Pipe length = 2.57(Ft.) Slope = 0.0389 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.892(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 2.892(CFS)
Normal flow depth in pipe = 6.59(In.)
Flow top width inside pipe = 7.97(In.)
Critical depth could not be calculated.
Pipe flow velocity = 8.34 (Ft/s)
Travel time through pipe = 0.01 mm.
Time of concentration (TC).= 4.27 mm.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++.++++.+++++++++
Process from Point/Station 42.000 to Point/Station 42.000
SUBAREA FLOW ADDITION
Calculated TC of 4.273 minutes is less than 5 minutes,
resetting TC to 5.0 minutes for rainfall intensity calculations
Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
[HIGH DENSITY RESIDENTIAL
12
(24.0 DU/A or Less
Impervious value, Ai = 0.650
Sub-Area C Value = 0.670
Time of concentration = 4.27 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.670 CA = 0.436
Subarea runoff = 0.092(CFS) for 0. 020 (Ac
Total runoff = 2.983(CFS) Total area = 0.650(Ac.)
++++++++++++.++.++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 42.000 to Point/Station 44.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 54.600(Ft.)
Downstream point/station elevation = 50.780(Ft.)
Pipe length = 22.25(Ft.) Slope = 0.1717 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.983(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 2.983(CFS)
Normal flow depth in pipe = 4.15(In.)
Flow top width inside pipe = 8.97(In.)
Critical depth could not be calculated.
Pipe flow velocity = 14.98(Ft/s)
Travel time through pipe = 0.02 min.
Time of concentration (TC) = 4.30 mm.
End of computations, total study area = 0.650 (Ac.)
13