HomeMy WebLinkAboutSDP 16-13; OAK VETERANS HOUSING; DRAINAGE REPORT FOR OAK VETERANS HOUSING; 2020-06-05DRAINAGE REPORT
II'
OAK VETERANS HOUSING
(SDP 16-13, GR 2020-0008, Drawing No. 523-5A)
June 5, 2020
ESSi
No. 46548
Exp. 6/30/21
chamokmImn
Civil Engineeiing • Hydrology Hydraulics Sedimentation
P.O. Box 9496
Rancho Santa Fe, CA 92067
(858) 692-0760
TABLE OF CONTENTS
Introduction .1
Hydrologic and Hydraulic Analyses..................................................................................................2
Conclusion.........................................................................................................................................3
APPENDICES
A. 100-Year Rational Method Analyses and Supporting Data
INTRODUCTION
The Oak Veterans Housing project is located at 965 and 967 Oak Avenue in the city of Carlsbad
(see the Vicinity Map). The project proposes 24 veterans' housing units on a 0.434 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 two 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 0CANS1D
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 on-site 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
on-site drainage basins were set equal to allow a comparison of results.
There is an off-site area to the east that is tributary to the project. Separate drainage facilities
system will be constructed to convey runoff from the off-site area to Oak Avenue to prevent
commingling with the on-site runoff. The off-site area is 0.26 acres as shown on the
attached Proposed Condition Rational Method Work Map. Runoff from the off-site area will
be captured by a proposed trench drain along the site's easterly property line. The trench
drain will convey the runoff to a curb outlet onto Oak Avenue.
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 23 percent impervious, so the low density
residential (2.9 DU/A or 25 percent) category was assumed. Under proposed conditions, the
overall on-site drainage area is 75 percent impervious, so the high density residential (43.0
DU/A or 80 percent) category was assumed. Both land use categories have slightly higher
percent impervious than actual conditions, but the proposed has a greater delta, so the
comparison of results will be slightly conservative.
For the off-site drainage area, the low density residential (2.9 DU/A or 25 percent) category
was assumed based on the current conditions.
Flow lengths and elevations: The flow lengths and elevations were obtained from the base
topography and engineering plans.
Table 1 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 six 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 12) 0.41 3.80 0.44 0.7
Proposed (Node 36) 0.77 6.66 0.44 2.3
Off-site (Proposed Node 44) 0.41 5.59 0.27 0.6
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 Oak
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 less than 0.5
acres, so the resulting flow increase will be small and further mitigated by the six biofiltration
basins.
APPENDIX A
100-YEAR RATIONAL METHOD ANALYSES
AND SUPPORTING DATA
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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 I Runoff Coefficient "C"
Soil Type
NRCS Elements County Elements I % IMPER. A nB
C D
Undisturbed Natural Terrain (Natural)
Low Density Residential (LDR)
Low Density Residential (LDR)
Low Density Residential (LDR)
Medium Density Residential (MDR)
Medium Density Residential (MDR)
Medium Density Residential (MDR)
Medium Density Residential (MDR)
High Density Residential (HDR)
High Density Residential (HDR)
Commercial/Industrial (N. Corn)
Commercial/Industrial (G. Corn)
Commercial/Industrial (O.P. Corn)
Commercial/Industrial (Limited I.)
Commercial/Industrial (General I.)
Permanent Open Space
Residential, 1.0 DU/A or less
Residential, 2.0 DU/A or less
Residential, 2.9 DU/A or less
Residential, 4.3 DU/A or less
Residential, 7.3 DU/A or less
Residential, 10.9 DU/A or less
Residential, 14.5 DU/A or less
Residential, 24.0 DU/A or less
Residential, 43.0 DU/A or less
Neighborhood Commercial
General Commercial
Office Professional/Commercial
Limited Industrial
General Industrial
0* 0.20 0.25 0.30
10 0.27 0.32 0.36
20 0.34 0.38 0.42
25 0.38 0.41 0.45
30 0.41 0.45 0.48
40 0.48 0.51 0.54
45 0.52 0.54 0.57
50 0.55 0.58 0.60
65 0.66 0.67 0.69
80 0.76 0.77 0.78
80 0.76 0.77 0.78
85 0.80 0.80 0.81
90 0.83 0.84 0.84
90 0.83 0.84 0.84
95 0.87 0.87 0.87
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
3. Hydrologic Soil Group—San Diego County Area, California C
339'44N - - 33 9'44N
4
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OAR
Yl
9
33 9'37'N 33937N
C
5/4/2016
Page 1 0f4
C
Map Scale: 1:1,720 if printed on A landscape (11" x 8.5") sheet.
Meters N 0 25 50 100 150
Feet ,\\0 50 100 200 300
Map pmjection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone UN WG584
USDA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
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
11.1 100.0%
Totals for Area of Interest 11.1 100.0%
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 D) and
three dual classes (AID, BID, and do). 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 CO), 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 0 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
21111111111 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 ------------------------------------------------------------------------
Oak 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
[LOW DENSITY RESIDENTIAL
(2.9 DU/A or Less
Impervious value, Ai = 0.250
Sub-Area C Value = 0.410
Initial subarea total flow distance = 269.000(Ft.)
Highest elevation = 71.100(Ft.)
Lowest elevation = 68.000(Ft.)
Elevation difference = 3.100(Ft.) Slope = 1.152 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 70.00 (Ft)
for the top area slope value of 1.15 %, in a development type of
2.9 DU/A or Less
In Accordance With Figure 3-3
ii
Initial Area Time of Concentration = 9.91 minutes
TC = [1.8*(1.1_C)*distance(Ft.).5)/(% slopeA(1/3)]
TC= [1.8*(1.1_0.4100)*( 70.000".5)/( 1.152"(1/3)1= 9.91
The initial area total distance of 269.00 (Ft.) entered leaves a
remaining distance of 199.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 2.56 minutes
for a distance of 199.00 (Ft.) and a slope of 1.15 %
with an elevation difference of 2.29(Ft.) from the end of the top area
Tt = [11. 9*length(Mi)A3)/(elevation change(Ft. ))]A.385 *60(min/hr)
= 2.565 Minutes
Tt=[(11.9*0.0377'3)/( 2.29)]A.385= 2.56
Total initial area Ti = 9.91 minutes from Figure 3-3 formula plus
2.56 minutes from the Figure 3-4 formula = 12.48 minutes
Rainfall intensity (I) = 3.798(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.410
Subarea runoff = 0.685(CFS)
Total initial stream area = 0.440(Ac.)
End of computations, total study area = 0.440 (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: 06/05/20 ------------------------------------------------------------------------
Oak 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
(43.0 DU/A or Less
Impervious value, Al = 0.800
Sub-Area C Value = 0.770
Initial subarea total flow distance = 86.000(Ft.)
Highest elevation = 71.100(Ft.)
Lowest elevation = 67.300(Ft.)
Elevation difference = 3.800(Ft.) Slope = 4.419 %
Top of Initial Area Slope adjusted by User to 4.767 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 95.00 (Ft)
for the top area slope value of 4.77 %, in a development type of
43.0 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 3.44 minutes
TC = [1.8* (1. 1_C)*distance(Ft. ) ".5) / (% slope" (1/3)]
TC= [1.8*(1.1_0.7700)*( 95.000".5)/( 4.767"(1/3)]= 3.44
Calculated TC of 3.440 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 = 0.770
Subarea runoff = 0.422(CFS)
Total initial stream area = 0.080(Ac.)
Process from Point/Station 12.000 to Point/Station 14.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 63.620(Ft.)
Downstream point/station elevation = 62.810(Ft.)
Pipe length = 86.10(Ft.) Slope = 0.0094 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 0.422(CFS)
Nearest computed pipe diameter = 6.00(In.)
Calculated individual pipe flow = 0.422(CFS)
Normal flow depth in pipe = 3.97(In.)
Flow top width inside pipe = 5.68 (In.)
Critical Depth = 3.97(In.)
Pipe flow velocity = 3.06(Ft/s)
Travel time through pipe = 0.47 mm.
Time of concentration (TC) = 3.91 mm.
++++++++++++++.+.++++++++++++++++++++++++++.++++++++++++++++++++++++++
Process from Point/Station 14.000 to Point/Station 14.000
SUBAREA FLOW ADDITION
Calculated TC of 3.909 minutes is less
resetting TC to 5.0 minutes for rainfall
Rainfall intensity (I) = 6.850(In/Hr)
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
(43.0 DU/A or Less
Impervious value, Ai = 0.800
Sub-Area C Value = 0.770
Time of concentration = 3.91 mm.
Rainfall intensity = 6.850(In/Hr)
Effective runoff coefficient used for
(Q=KCIA) is C = 0.770 CA = 0.146
Subarea runoff = 0.580(CFS) for
Total runoff = 1.002(CFS) Total
than 5 minutes,
intensity calculations
for a 100.0 year storm
for a 100.0 year storm
total area
0.110 (Ac.)
area = 0.190(Ac.)
Process from Point/Station 14.000 to Point/Station 16.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 62.810(Ft.)
Downstream point/station elevation = 61.750(Ft.)
Pipe length = 109.13(Ft.) Slope = 0.0097 Manningts N = 0.013
No. of pipes = 1 Required pipe flow = 1.002(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.002(CFS)
Normal flow depth in pipe = 5.10(In.)
Flow top width inside pipe = 8.92(In.)
Critical Depth = 5.51(In.)
Pipe flow velocity = 3.88(Ft/s)
Travel time through pipe = 0.47 mm.
Time of concentration (TC) = 4.38 mm.
+++++++++-f++++++++++++++++++++++++++++-f--4-++++++++++++++++++++++++++++++
Process from Point/Station 18.000 to Point/Station 16.000
SUBAREA FLOW ADDITION
Calculated TC of 4.377 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
(43.0 DU/A or Less
Impervious value, Ai = 0.800
Sub-Area C Value = 0.770
Time of concentration = 4.38 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.770 CA = 0.185
Subarea runoff = 0.264(CFS) for 0.050 (Ac.)
Total runoff = 1.266(CFS) Total area = 0.240(Ac.)
+++++++++++-f++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 16.000 to Point/Station 16.000
SUBAREA FLOW ADDITION
Calculated TC of 4.377 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
3
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 = 0.770
Time of concentration = 4.38 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.770 CA = 0.231
Subarea runoff = 0.316(CFS) for 0.060(Ac.)
Total runoff = 1.582(CFS) Total area = 0.300(Ac.)
Process from Point/Station 16.000 to Point/Station 20.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 61.740(Ft.)
Downstream point/station elevation = 61.450(Ft.)
Pipe length = 29.62(Ft.) Slope = 0.0098 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.582(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.582(CFS)
Normal flow depth in pipe = 7.13(In.)
Flow top width inside pipe = 7.31(In.)
Critical Depth = 6.95(In.)
Pipe flow velocity = 4.22(Ft/s)
Travel time through pipe = 0.12 mm.
Time of concentration (TC) = 4.49 mm.
+++++++++++++++++-1-+++++++++++++++++++++++++++++++++++++++++++-4-++++++++
Process from Point/Station 16.000 to Point/Station 20.000
CONFLUENCE OF MINOR STREAMS ****
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 0.300(Ac.)
Runoff from this stream = 1.582(CFS)
Time of concentration = 4.49 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
(43.0 DU/A or Less
4
Impervious value, Ai = 0.800
Sub-Area C Value = 0.770
Initial subarea total flow distance = 42.000(Ft.)
Highest elevation = 71.100(Ft.)
Lowest elevation = 70.600(Ft.)
Elevation difference = 0.500(Ft.) Slope = 1.190 %
Top of Initial Area Slope adjusted by User to 1.905 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 75.00 (Ft)
for the top area slope value of 1.91 %, in a development type of
43.0 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 4.15 minutes
TC = [1.8* (1. 1_C)*distance(Ft. ) A .5) / (% slopeA (1/3)]
TC= [1.8*(1.1_0.7700)*( 75.000".5)/( 1.905A(1/3)]= 4.15
Calculated TC of 4.150 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 = 0.770
Subarea runoff = 0.211(CFS)
Total initial stream area = 0.040(Ac.)
Process from Point/Station 32.000 to Point/Station 34.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 65.700(Ft.)
Downstream point/station elevation = 64.700(Ft.)
Pipe length = 93.67(Ft.) Slope = 0.0107 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 0.211(CFS)
Nearest computed pipe diameter = 6.00(In.)
Calculated individual pipe flow = 0.211(CFS)
Normal flow depth in pipe = 2.50(In.)
Flow top width inside pipe = 5.92 (In.)
Critical Depth = 2.76(In.)
Pipe flow velocity = 2.72(Ft/s)
Travel time through pipe = 0.57 mm.
Time of concentration (TC) = 4.72 mm.
Process from Point/Station 34.000 to Point/Station 34.000
SUBAREA FLOW ADDITION
Calculated TC of 4.724 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
(43.0 DU/A or Less
Impervious value, Ai = 0.800
Sub-Area C Value = 0.770
Time of concentration = 4.72 mm.
Rainfall intensity = 6.850(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.770 CA = 0.108
Subarea runoff = 0.527(CFS) for 0.100(Ac.)
Total runoff = 0.738(CFS) Total area = 0.140(Ac.)
Process from Point/Station 34.000 to Point/Station 20.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 64.700(Ft.)
Downstream point/station elevation = 64.080(Ft.)
Pipe length = 63.95(Ft.) Slope = 0.0097 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 0.738(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 0.738(CFS)
Normal flow depth in pipe = 4.25(In.)
Flow top width inside pipe = 8.99(In.)
Critical Depth = 4.70(In.)
Pipe flow velocity = 3.60(Ft/s)
Travel time through pipe = 0.30 mm.
Time of concentration (TC) = 5.02 mm.
+++++++++++++++++++++++++++++++++++++++++++++++++.++++++++++++++++++++
Process from Point/Station 34.000 to Point/Station 20.000
CONFLUENCE OF MINOR STREAMS ****
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 0.140(Ac.)
Runoff from this stream = 0.738(CFS)
Time of concentration = 5.02 mm.
Rainfall intensity = 6.832(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (mm) (In/Hr)
1 1.582 4.49 6.850
2 0.738 5.02 6.832
Qmax(1) =
1.000 * 1.000 * 1.582) +
1.000 * 0.895 * 0.738) + = 2.243
Qmax(2) =
0.997 * 1.000 * 1.582) +
6
1.000 * 1.000 * 0.738) + = 2.317
Total of 2 streams to confluence:
Flow rates before confluence point:
1.582 0.738
Maximum flow rates at confluence using above data:
2.243 2.317
Area of streams before confluence:
0.300 0.140
Results of confluence:
Total flow rate = 2.317(CFS)
Time of concentration = 5.021 mm.
Effective stream area after confluence = 0.440(Ac.)
Process from Point/Station 20.000 to Point/Station 36.000
PIPEFLOW TRAVEL TIME (Program estimated size) ****
Upstream point/station elevation = 64.080(Ft.)
Downstream point/station elevation = 60.640(Ft.)
Pipe length = 20.27(Ft.) Slope = 0.1697 Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.317(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 2.317(CFS)
Normal flow depth in pipe = 3.62(In.)
Flow top width inside pipe = 8.82(In.)
Critical Depth = 8.13(In.)
Pipe flow velocity = 13.95(Ft/s)
Travel time through pipe = 0.02 mm.
Time of concentration (TC) = 5.04 mm.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 40.000 to Point/Station 42.000
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
[LOW DENSITY RESIDENTIAL
(2.9 DU/A or Less
Impervious value, Ai = 0.250
Sub-Area C Value = 0.410
Initial subarea total flow distance = 25.000(Ft.)
Highest elevation = 89.000(Ft.)
Lowest elevation = 73.000(Ft.)
Elevation difference = 16.000(Ft.) Slope = 64.000 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 64.00 %, in a development type of
7
2.9 DU/A or Less
In Accordance With Figure 3-3
Initial Area Time of Concentration = 3.11 minutes
TC = [1.8*(1.1_C)*distance(Ft.).5)/(% slope '(1/3)]
TC = [1.8*(1.1_0.4100)*( 100.000A.5)/( 64.000'(1/3)]= 3.11
Calculated TC of 3.105 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 = 0.410
Subarea runoff = 0.028(CFS)
Total initial stream area = 0.010(Ac.)
Process from Point/Station 42.000 to Point/Station 44.000
' IMPROVED CHANNEL TRAVEL TIME
Upstream point elevation = 73.000(Ft.)
Downstream point elevation = 71.000(Ft.)
Channel length thru subarea = 176.000(Ft.)
Channel base width = 3.000(Ft.)
Slope or 'Z' of left channel bank = 10.000
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 0.360(CFS)
Manning's 'N' = 0.040
Maximum depth of channel = 1.000(Ft.)
Flow(q) thru subarea = 0.360(CFS)
Depth of flow = 0.112(Ft.), Average velocity = 0.782(Ft/s)
Channel flow top width = 5.235(Ft.)
Flow Velocity = 0.78(Ft/s)
Travel time = 3.75 mm.
Time of concentration = 6.86 min.
Critical depth = 0.070(Ft.)
Adding area flow to channel
Rainfall intensity (I) = 5.588(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
[LOW DENSITY RESIDENTIAL I
(2.9 DU/A or Less
Impervious value, Ai = 0.250
Sub-Area C Value = 0.410
Rainfall intensity = 5.588(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.410 CA = 0.111
Subarea runoff = 0.590(CFS) for 0.260(Ac.)
Total runoff = 0.619(CFS) Total area = 0.270(Ac.)
Depth of flow = 0.150(Ft.), Average velocity = 0.920(Ft/s)
Critical depth = 0.098 (Ft.)
End of computations, total study area= 0.710 (Ac.)
8