Hallmark‐Barham Specific Plan EIR
Technical Appendices
Appendix J.1
Drainage Report
Preliminary Drainage Report
943 Barham Drive
TM 20- /SDP 20-
City of San Marcos, CA
County of San Diego
PREPARED FOR:
Hall Land Company
740 Lomas Santa Fe Drive, Suite 204
Solana Beach, CA 92075
(858) 481-3310
PREPARED BY:
BB&D~
PLANNING E NGINEE R ING SURVEYING
SB&O, INC.
3990 RUFFIN ROAD, SUITE 120
SAN DIEGO, CA 92123
(858) 560-1141
SB&O JOB NO. 75050.25
Corporate Office: 3990 Ruffin Road, Suite 120 ■ Sa D" o, CA. 92123 ■ Phone (858) 560-1141 ■ Fax (858) 560-8157 41689 Enterprise Circle North, Suite 126 ■ Temecula , CA. 92590 ■ Phone (951) 695-8900 ■ (951) 695-8901 D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page i
TABLE OF CONTENTS
Vicinity Map ........................................................................................................................1
1. Scope of Report................................................................................................................... 2
2. Hydrology ........................................................................................................................... 2
3. Existing Site ........................................................................................................................ 3
4. Project Hydrology ............................................................................................................... 4
5. Detention ............................................................................................................................ 4
6. Rational Method Hydrograph Methodology ....................................................................... 5
7. Detention Models ................................................................................................................ 5
8. Post Development Hydrology ............................................................................................. 6
9. Conclusion ......................................................................................................................... 6
DRAINAGE MAP
Existing Drainage Exhibit Map Pocket #1
Proposed Drainage Exhibit Map Pocket #2
EXHIBITS
A. Existing Rational Method Calculations (CivilD)
B. Post Development Rational Method Calculations (CivilD) C. Rational Method Hydrographs
D. Detention Basin – Storage Indication Table
E. Detention Basin Routing
APPENDIX
County Hydrology Manual (2003) References
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 1
VICINITY MAP
NOT TO SCALE
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 2
1. Scope of Report
The project is subject to storm water treatment and HMP mitigation requirements. By definition, HMP compliance minimizes the potential for altering flow regimes and creating excessive erosion in receiving waters. This is accomplished by limiting increases in flow rates and durations based upon the pre-development range of geomorphically significant flows. Sizing of treatment Best Management Practices (BMPs), and analyses of hydromodification impacts are provided in the Storm Water Quality Management Plan (SWQMP) prepared by SB&O Inc.
The purpose of this report is to document the project changes in the flood level peak flow rates.
Due to the potential near term storm drain capacity constraints, the report will include detention routing to verify that the 100-year post development runoff does exceed the existing peak flow rates. Therefore, capacity analyses of the downstream facilities are not warranted.
Detailed pipe calculations and inlet sizing will be provided during the final design report.
2. Hydrology
2.1 Design Criteria
Rational Method calculations were prepared in accordance with the County of San Diego of Hydrology Manual (June 2003 Edition) to calculate the peak flow rates for the 100-year storm events. (See Appendix for Reference Materials, Charts & Tables)
2.2 Soils
Onsite surface soils are generally classified as granular. Based on the project Preliminary Geotechnical report, the hydrologic soil classification is Type “D” (See Appendix for Hydrologic Soil Group Map).
2.3 Runoff Coefficient (C-Factors)
Runoff coefficients in the rational method were assigned based upon the impervious ratio of the tributary area, and assigned based upon soil type as follows;
Runoff Coefficients - Type “B” Soil
Condition % Impervious Runoff Coefficient
Existing site /upstream hillside 10 0. 41
Proposed Site – HDR 80 0.79
Barham R/W 90 0. 85
2.4 Rainfall
Rainfall intensities were calculated using the rainfall data from the County 6-Hour and 24-Hour Isopluvial Maps as follows:
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 3
Storm
Event
6-Hour
Rainfall
(in)
24-Hour
Rainfall
(in)
Ratio
P6/P24
Adjusted
P6
(in)
100 -Year 3.3 5.7 58 % 3.3
50-Year 2.8 5.3 53 % 2.8
25 -Year 2.6 4.6 57% 2.6
10 -Year 2.2 3.7 59% 2.2
5-Year 1.9 3.3 58% 1.9
2-Year 1.52 2.4 63% 1.52
See Appendix for Isopluvial Maps and Figure 3-1 to determine the adjusted 6-hour rainfall.
2.5 Time of Concentration
Rainfall intensities were calculated using times of concentration in accordance with the procedures noted in the June 2003 Hydrology manual. This includes the limitations on maximum overland flow length and initial times of concentration as noted in Table 3-2. The initial times of concentration are restricted based upon the Land Use / Density (% Impervious) and slope.
3. Existing Site
The property is located in the eastern portion of San Marcos, south of SR-78, between Nordahl Road & Twin Oaks Valley Road. The existing site is approximately 10 acres in size, with frontage along the south side of Barham Road, between La Morcee Road & Woodland Parkway.
The existing site is vacant and includes a hillside along the southern limits. Drainage is “natural” and generally overland toward the Barham Road front age. Drainage patterns are generally southeast to northwest and includes run-on from the hillside above the site. The majority of site runoff is directed overland to the Barham gutter. A small depression is near the northwest corner of the site. A storm drain riser is located near t he northeast corner of the site and is connected to the public storm drain in Barham Road (MS-4).
See Existing Drainage Exhibit Map Pocket #1.
Existing Hydrology
Location Basin Area
(ac)
CivilD
Node
“C” Tc
(min)
Q100
(cfs)
Existing Site & Hillside A-1 13.931 0.41 11.08 29.73 Barham Frontage & Cut
Slope
A-2,3 0.923 0.85 8.47 4.856
Existing Total 14.854 11.08 33.81
The existing hydrology calculations (CivilD) are available for review in Exhibit “A”.
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 4
4. Project Hydrology
The Barham Drive project is a high-density multi-family residential development with private streets, driveways and alleys. Several multi-story buildings with individual parking garages and surface parking will be constructed. A recreation area and building are also included. The majority of the developed runoff will be conveyed by the site private storm drain system to the northwest corner of the site for treatment and flow control (HMP & Detention). The proposed basin which will discharge to the existing storm drain system in Barham Road.
See the Proposed Drainage Exhibit in Map Pocket #2.
Due to the hillside nature of the development, runoff from the steep driveway entries and frontage slopes will discharge to the Barham gutter. These flow will be intercepted by a proposed inlet on Barham Road near the northwest corner of the site.
The uphill section of the project will include manufactured cut slopes at the existing hillside.
Runoff from the existing and proposed slopes will be intercepted in the bypass drainage ditches and storm drain, then directed to the westerly limits and then conveyed to a proposed inlet near the northwest corner of the property, which is connected to the existing Barham storm drain (MS-4).
Post development site runoff is summarized below;
Post Development Hydrology
Location Basin Area
(ac)
CivilD
Node
“C” Tc
(min)
Q100
(cfs)
Developed site P1 -P5,C 7.51 13 -17 0. 79 8.0 38.07 Barham A, B 1.92 1-10 0.76 8.47 9.06
Slopes/Bypass E-1 to E -5 5.43 18 0. 41 9.39 13.32 Post Development 14.86 60.45
The proposed hydrology calculations (CivilD) are available for review in Exhibit “B”.
5. Detention
The project is required to provide water quality treatment and flow control for post development runoff. The project proposes a surface biofiltration basin with enhanced below grade storage to provide treatment and flow control. The surface basin has additional storage depth and an overflow structure with both a weir opening and grated top to provide attenuation of larger storm events. A concrete lined ramp provides an emergency overflow path to the driveway and then Barham Drive. In order to ensure that post development flows do not exceed existing peak flows, detention routing analyses were prepared to determine peak outflows, and to provide adjusted discharge estimate for comparison to the existing condition.
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 5
6. Rational Method Hydrograph Methodology
The County of San Diego Hydrology Manual includes a procedure to develop a time-based runoff series. The methodology assumes a simple triangular runoff hydrograph, and is based the 6-hour rainfall total, and the Rational Method input variables. The methodology provides runoff values at time intervals equal to multiples of the time of concentration. Details related to the procedure to develop the hydrograph are provided in Chapter 6 of the County of San Diego Hydrology Manual (See Appendix for details).
Rational method hydrographs for the 6-hour storms were prepared for the area tributary to the detention basin. Hydrographs were not prepared for the Barham /frontage slopes or the hillside / bypass drain system, or the existing development conditions.
See Exhibit “C” for the 6-hour Rational Method Hydrograph calculations & time series.
7. Detention Models
The detention models are based upon the basin and flow control openings determined by the SWMM analysis. Discharge values were estimated using standard weir and orifice flow equations. A Storage-Indication-Outflow table was prepared using the following data;
Main Basin Storage 54,724 cf. (1.26 ac-ft) @ 4.95’ surface depth Elevation Description Dimension/ Size Comment
647.15 Bottom of Crushed Rock 6,764 sf 40% V oid Ratio 647.15 Low Flow Orifice 2” dia .
648.15 Bottom of Soil Layer 6,764 sf 30% V oid Ratio 650.15 Floor of Surface Basin 6,764 sf
650.65 surface depth @ 6” 7,330 sf Treatment Surface Area 653.90 3” overflow opening 11,027 sf 3. 75’ surface depth 654. 60 Grated overflow 5’ x5’ 11,931 sf 4.45’ surface depth 655.10 Surface Overflow 12,594 sf 4. 95’ surface depth 656.10 Top of Earth Berm 14,575 sf 5. 95’ surface depth
The Storage Indication Outflow table are located in Exhibit “D”.
The 6-hour rational method hydrographs were routed to determine the attenuated peak outflow and maximum storage depth. A review of the results indicates a peak outflow to the storm drain is 5.61 cfs, with a maximum depth of 7.75 feet (4.75’ surface depth). The maximum 100-year water surface elevation is estimated at 654.9, which is 0.2’ below the overflow ramp.
The detention routing analysis is located in Exhibit “E”.
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 6
8. Post Development Hydrology
In order to assess the potential hydrology impacts of the development, an adjusted comparison is summarized as follows;
Post Development Hydrology – Adjusted Discharge
Location Basin Area
(ac)
CivilD
Node
“C” Tc
(min)
Q100
(cfs)
Developed site Detention 7.51 8.0 5.61
Barham A, B 1.92 1-10 0.76 8.47 9.06
Slopes/Bypass E-1 to E -5 5.43 18 0.41 9.39 13.32
Post Development 14.86 27.99
Existing Total 14.85 11.08 33.81
Change -5.82
The comparison illustrates that the detention basin will attenuate post development flows to at or below the existing conditions.
The existing storm drain to the site is shown on City of San Marcos plan IP 4729 Sheet 39B as
Interim 18” RCP Storm Drain @ 0.39% with an Interim Capacity = 10.2 cfs, which will be connected to the future Storm Drain 48” RCP @ 0.66% Q100 = 117.4 cfs
The estimated post project 100-year peak discharge to the interim storm drain is 18.93 cfs (detention outflow + bypass), compared to the exiting peak flow of 29.73 cfs.
9. Conclusion
The project proposes a single combination basin to provide treatment, flow control and attenuation of storm flows from the development envelope. The calculations and detention analysis confirm that the post project peak flows will not exceed the existing condition.
Due to the hillside nature of the development, runoff from the steep driveway entries and frontage slopes will discharge to the Barham gutter, and will avoid the detention basin. These flows will continue westerly to the existing curb inlet on Barham Road near the church driveway.
The uphill section of the project will include manufactured cut slopes. Runoff from the existing and proposed slopes will be intercepted in the bypass drainage ditches and storm drain, directed to the westerly limits and conveyed to a proposed inlet near the northwest corner of the property, which is connected to the existing Barham Drive storm drain (MS-4).
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 7
EXHIBIT A
EXISTING CONDITIONS
RATIONAL METHOD (CIVILD)
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: 06/04/20
------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6334
------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 3.300
24 hour precipitation(inches) = 5.700
P6/P24 = 57.9%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.000 to Point/Station 2.000 **** 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
[LOW DENSITY RESIDENTIAL ]
(1.0 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Initial subarea total flow distance = 1615.000(Ft.)
Highest elevation = 874.000(Ft.)
Lowest elevation = 649.400(Ft.)
Elevation difference = 224.600(Ft.) Slope = 13.907 %
Top of Initial Area Slope adjusted by User to 14.025 %
Bottom of Initial Area Slope adjusted by User to 14.025 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 14.03 %, in a development type of
1.0 DU/A or Less
In Accordance With Table 3-2
Initial Area Time of Concentration = 6.40 minutes
(for slope value of 10.00 %)
The initial area total distance of 1615.00 (Ft.) entered leaves a remaining distance of 1515.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 4.68 minutes for a distance of 1515.00 (Ft.) and a slope of 14.03 %
with an elevation difference of 212.48(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 4.677 Minutes
Tt=[(11.9*0.2869^3)/(212.48)]^.385= 4.68
Total initial area Ti = 6.40 minutes from Table 3-2 plus
4.68 minutes from the Figure 3-4 formula = 11.08 minutes 1 Rainfall intensity (I) = 5.205(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.410 Subarea runoff = 29.731(CFS)
Total initial stream area = 13.931(Ac.)
End of computations, total study area = 13.931 (Ac.) 2 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: 05/05/20
------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6334
------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 3.300
24 hour precipitation(inches) = 5.700
P6/P24 = 57.9%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 3.000 to Point/Station 4.000 **** 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
[INDUSTRIAL area type ]
(Limited Industrial )
Impervious value, Ai = 0.900
Sub-Area C Value = 0.850
Initial subarea total flow distance = 100.000(Ft.)
Highest elevation = 666.000(Ft.)
Lowest elevation = 663.800(Ft.)
Elevation difference = 2.200(Ft.) Slope = 2.200 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 70.00 (Ft)
for the top area slope value of 2.20 %, in a development type of Limited Industrial
In Accordance With Table 3-2
Initial Area Time of Concentration = 3.10 minutes
(for slope value of 2.00 %)
The initial area total distance of 100.00 (Ft.) entered leaves a remaining distance of 30.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 0.47 minutes for a distance of 30.00 (Ft.) and a slope of 2.20 %
with an elevation difference of 0.66(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 0.466 Minutes
Tt=[(11.9*0.0057^3)/( 0.66)]^.385= 0.47
Total initial area Ti = 3.10 minutes from Table 3-2 plus
0.47 minutes from the Figure 3-4 formula = 3.57 minutes Calculated TC of 3.566 minutes is less than 5 minutes, resetting TC to 5.0 minutes for rainfall intensity calculations 1 Rainfall intensity (I) = 8.695(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.850 Subarea runoff = 1.153(CFS)
Total initial stream area = 0.156(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 4.000 to Point/Station 5.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** ______________________________________________________________________ Top of street segment elevation = 663.800(Ft.)
End of street segment elevation = 648.900(Ft.)
Length of street segment = 850.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 32.000(Ft.)
Distance from crown to crossfall grade break = 30.500(Ft.) Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0150
Manning's N from grade break to crown = 0.0150
Estimated mean flow rate at midpoint of street = 3.043(CFS) Depth of flow = 0.293(Ft.), Average velocity = 2.886(Ft/s) Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 9.915(Ft.)
Flow velocity = 2.89(Ft/s)
Travel time = 4.91 min. TC = 8.47 min.
Adding area flow to street
Rainfall intensity (I) = 6.187(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
[INDUSTRIAL area type ]
(Limited Industrial )
Impervious value, Ai = 0.900
Sub-Area C Value = 0.850
Rainfall intensity = 6.187(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.850 CA = 0.785
Subarea runoff = 3.701(CFS) for 0.767(Ac.)
Total runoff = 4.854(CFS) Total area = 0. 923(Ac.) Street flow at end of street = 4.854(CFS)
Half street flow at end of street = 4.854(CFS)
Depth of flow = 0.334(Ft.), Average velocity = 3.229(Ft/s) Flow width (from curb towards crown)= 11.967(Ft.)
End of computations, total study area = 0.923 (Ac.) 2 D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 8
EXHIBIT B
PROPOSED SITE
BYPASS STORM DRAIN
RATIONAL METHOD (CIVILD)
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: 06/16/20
------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6334
------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 3.300
24 hour precipitation(inches) = 5.700
P6/P24 = 57.9%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 13.000 to Point/Station 14.000 **** 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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Initial subarea total flow distance = 80.000(Ft.)
Highest elevation = 692.000(Ft.)
Lowest elevation = 691.200(Ft.)
Elevation difference = 0.800(Ft.) Slope = 1.000 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 65.00 (Ft)
for the top area slope value of 1.00 %, in a development type of
43.0 DU/A or Less
In Accordance With Table 3-2
Initial Area Time of Concentration = 4.70 minutes
(for slope value of 1.00 %)
The initial area total distance of 80.00 (Ft.) entered leaves a remaining distance of 15.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 0.37 minutes for a distance of 15.00 (Ft.) and a slope of 1.00 %
with an elevation difference of 0.15(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 0.370 Minutes
Tt=[(11.9*0.0028^3)/( 0.15)]^.385= 0.37
Total initial area Ti = 4.70 minutes from Table 3-2 plus
0.37 minutes from the Figure 3-4 formula = 5.07 minutes Rainfall intensity (I) = 8.617(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.790 1 Subarea runoff = 0.470(CFS)
Total initial stream area = 0.069(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 14.000 to Point/Station 15.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** ______________________________________________________________________ Top of street segment elevation = 691.200(Ft.)
End of street segment elevation = 688.000(Ft.)
Length of street segment = 300.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 13.000(Ft.)
Distance from crown to crossfall grade break = 11.500(Ft.) Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [2] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 1.500(Ft.)
Gutter hike from flowline = 1.500(In.)
Manning's N in gutter = 0.0150
Manning's N from gutter to grade break = 0.0150
Manning's N from grade break to crown = 0.0150
Estimated mean flow rate at midpoint of street = 6.917(CFS) Depth of flow = 0.326(Ft.), Average velocity = 2.464(Ft/s) Streetflow hydraulics at midpoint of street travel:
Halfstreet flow width = 11.543(Ft.)
Flow velocity = 2.46(Ft/s)
Travel time = 2.03 min. TC = 7.10 min.
Adding area flow to street
Rainfall intensity (I) = 6.935(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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Rainfall intensity = 6.935(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 1.946
Subarea runoff = 13.025(CFS) for 2.394(Ac.)
Total runoff = 13.494(CFS) Total area = 2. 463(Ac.) Street flow at end of street = 13.494(CFS)
Half street flow at end of street = 6.747(CFS)
Depth of flow = 0.389(Ft.), Average velocity = 3.068(Ft/s) Note: depth of flow exceeds top of street crown.
Flow width (from curb towards crown)= 13.000(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 15.000 to Point/Station 16.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 678.000(Ft.)
Downstream point/station elevation = 670.500(Ft.)
Pipe length = 155.00(Ft.) Slope = 0.0484 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 13.494(CFS)
Given pipe size = 12.00(In.)
NOTE: Normal flow is pressure flow in user selected pipe size. 2 The approximate hydraulic grade line above the pipe invert is
21.604(Ft.) at the headworks or inlet of the pipe(s)
Pipe friction loss = 22.228(Ft.)
Minor friction loss = 6.876(Ft.)K-factor = 1.50
Pipe flow velocity = 17.18(Ft/s)
Travel time through pipe = 0.15 min.
Time of concentration (TC) = 7.25 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 16.000 to Point/Station 17.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 6.842(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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 7.25 min.
Rainfall intensity = 6.842(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 2.457
Subarea runoff = 3.316(CFS) for 0.647(Ac.)
Total runoff = 16.810(CFS) Total area = 3. 110(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 16.000 to Point/Station 17.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 6.842(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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 7.25 min.
Rainfall intensity = 6.842(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 2.890
Subarea runoff = 2.962(CFS) for 0.548(Ac.)
Total runoff = 19.772(CFS) Total area = 3. 658(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 16.000 to Point/Station 17.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 6.842(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
[HIGH DENSITY RESIDENTIAL ]
(43.0 DU/A or Less )
3 Impervious value, Ai = 0.800
Sub-Area C Value = 0.790
Time of concentration = 7.25 min.
Rainfall intensity = 6.842(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.790 CA = 5.569
Subarea runoff = 18.329(CFS) for 3.391(Ac.)
Total runoff = 38.102(CFS) Total area = 7. 049(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 16.000 to Point/Station 17.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 670.500(Ft.)
Downstream point/station elevation = 649.600(Ft.)
Pipe length = 465.00(Ft.) Slope = 0.0449 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 38.102(CFS)
Given pipe size = 24.00(In.)
Calculated individual pipe flow = 38.102(CFS)
Normal flow depth in pipe = 16.15(In.)
Flow top width inside pipe = 22.52(In.)
Critical depth could not be calculated.
Pipe flow velocity = 16.94(Ft/s)
Travel time through pipe = 0.46 min.
Time of concentration (TC) = 7.71 min.
End of computations, total study area = 7.049 (Ac.) 4 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: 06/04/20
------------------------------------------------------------------------ ********* Hydrology Study Control Information ********** ------------------------------------------------------------------------ Program License Serial Number 6334
------------------------------------------------------------------------ Rational hydrology study storm event year is 100.0
English (in-lb) input data Units used
Map data precipitation entered:
6 hour, precipitation(inches) = 3.300
24 hour precipitation(inches) = 5.700
P6/P24 = 57.9%
San Diego hydrology manual 'C' values used
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.000 to Point/Station 2.000 **** 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
[LOW DENSITY RESIDENTIAL ]
(1.0 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Initial subarea total flow distance = 625.000(Ft.)
Highest elevation = 874.000(Ft.)
Lowest elevation = 689.800(Ft.)
Elevation difference = 184.200(Ft.) Slope = 29.472 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 29.47 %, in a development type of
1.0 DU/A or Less
In Accordance With Table 3-2
Initial Area Time of Concentration = 6.40 minutes
(for slope value of 10.00 %)
The initial area total distance of 625.00 (Ft.) entered leaves a remaining distance of 525.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 1.55 minutes for a distance of 525.00 (Ft.) and a slope of 29.47 %
with an elevation difference of 154.73(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 1.554 Minutes
Tt=[(11.9*0.0994^3)/(154.73)]^.385= 1.55
Total initial area Ti = 6.40 minutes from Table 3-2 plus
1.55 minutes from the Figure 3-4 formula = 7.95 minutes Rainfall intensity (I) = 6.445(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.410 1 Subarea runoff = 6.627(CFS)
Total initial stream area = 2.508(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.000 to Point/Station 4.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 685.800(Ft.)
Downstream point/station elevation = 685.200(Ft.)
Pipe length = 111.00(Ft.) Slope = 0.0054 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 6.627(CFS)
Given pipe size = 12.00(In.)
NOTE: Normal flow is pressure flow in user selected pipe size.
The approximate hydraulic grade line above the pipe invert is
4.898(Ft.) at the headworks or inlet of the pipe(s)
Pipe friction loss = 3.839(Ft.)
Minor friction loss = 1.658(Ft.)K-factor = 1.50
Pipe flow velocity = 8.44(Ft/s)
Travel time through pipe = 0.22 min.
Time of concentration (TC) = 8.17 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.000 to Point/Station 4.000 **** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________ The following data inside Main Stream is listed:
In Main Stream number: 1
Stream flow area = 2.508(Ac.)
Runoff from this stream = 6.627(CFS)
Time of concentration = 8.17 min.
Rainfall intensity = 6.333(In/Hr)
Program is now starting with Main Stream No. 2
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 3.000 to Point/Station 4.000 **** 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
[LOW DENSITY RESIDENTIAL ]
(1.0 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Initial subarea total flow distance = 510.000(Ft.)
Highest elevation = 856.000(Ft.)
Lowest elevation = 685.200(Ft.)
Elevation difference = 170.800(Ft.) Slope = 33.490 %
INITIAL AREA TIME OF CONCENTRATION CALCULATIONS:
The maximum overland flow distance is 100.00 (Ft)
for the top area slope value of 33.49 %, in a development type of
1.0 DU/A or Less
In Accordance With Table 3-2
Initial Area Time of Concentration = 6.40 minutes
(for slope value of 10.00 %)
The initial area total distance of 510.00 (Ft.) entered leaves a remaining distance of 410.00 (Ft.)
Using Figure 3-4, the travel time for this distance is 1.22 minutes 2 for a distance of 410.00 (Ft.) and a slope of 33.49 % with an elevation difference of 137.31(Ft.) from the end of the top area Tt = [11.9*length(Mi)^3)/(elevation change(Ft.))]^.385 *60(min/hr) = 1.223 Minutes
Tt=[(11.9*0.0777^3)/(137.31)]^.385= 1.22
Total initial area Ti = 6.40 minutes from Table 3-2 plus
1.22 minutes from the Figure 3-4 formula = 7.62 minutes Rainfall intensity (I) = 6.624(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.410 Subarea runoff = 4.546(CFS)
Total initial stream area = 1.674(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 3.000 to Point/Station 4.000 **** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________ The following data inside Main Stream is listed:
In Main Stream number: 2
Stream flow area = 1.674(Ac.)
Runoff from this stream = 4.546(CFS)
Time of concentration = 7.62 min.
Rainfall intensity = 6.624(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)
1 6.627 8.17 6.333
2 4.546 7.62 6.624
Qmax(1) =
1.000 * 1.000 * 6.627) +
0.956 * 1.000 * 4.546) + = 10.974
Qmax(2) =
1.000 * 0.933 * 6.627) +
1.000 * 1.000 * 4.546) + = 10.727
Total of 2 main streams to confluence:
Flow rates before confluence point:
6.627 4.546
Maximum flow rates at confluence using above data:
10.974 10.727
Area of streams before confluence:
2.508 1.674
Results of confluence:
Total flow rate = 10.974(CFS)
Time of concentration = 8.173 min.
Effective stream area after confluence = 4.182(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 4.000 to Point/Station 5.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 685.200(Ft.)
Downstream point/station elevation = 684.500(Ft.)
Pipe length = 127.00(Ft.) Slope = 0.0055 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 10.974(CFS)
Given pipe size = 12.00(In.)
3 NOTE: Normal flow is pressure flow in user selected pipe size.
The approximate hydraulic grade line above the pipe invert is
15.891(Ft.) at the headworks or inlet of the pipe(s)
Pipe friction loss = 12.044(Ft.)
Minor friction loss = 4.547(Ft.)K-factor = 1.50
Pipe flow velocity = 13.97(Ft/s)
Travel time through pipe = 0.15 min.
Time of concentration (TC) = 8.32 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.000 to Point/Station 6.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 6.258(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 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Time of concentration = 8.32 min.
Rainfall intensity = 6.258(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.410 CA = 1.813
Subarea runoff = 0.370(CFS) for 0.239(Ac.)
Total runoff = 11.344(CFS) Total area = 4. 421(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.000 to Point/Station 6.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 684.500(Ft.)
Downstream point/station elevation = 683.700(Ft.)
Pipe length = 147.00(Ft.) Slope = 0.0054 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 11.344(CFS)
Given pipe size = 12.00(In.)
NOTE: Normal flow is pressure flow in user selected pipe size.
The approximate hydraulic grade line above the pipe invert is
18.956(Ft.) at the headworks or inlet of the pipe(s)
Pipe friction loss = 14.897(Ft.)
Minor friction loss = 4.859(Ft.)K-factor = 1.50
Pipe flow velocity = 14.44(Ft/s)
Travel time through pipe = 0.17 min.
Time of concentration (TC) = 8.49 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 6.000 to Point/Station 7.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 6.177(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 DU/A or Less )
Impervious value, Ai = 0.100
4 Sub-Area C Value = 0.410
Time of concentration = 8.49 min.
Rainfall intensity = 6.177(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.410 CA = 2.003
Subarea runoff = 1.029(CFS) for 0.464(Ac.)
Total runoff = 12.372(CFS) Total area = 4. 885(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 7.000 to Point/Station 6.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 683.700(Ft.)
Downstream point/station elevation = 682.600(Ft.)
Pipe length = 108.00(Ft.) Slope = 0.0102 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 12.372(CFS)
Given pipe size = 18.00(In.)
NOTE: Normal flow is pressure flow in user selected pipe size.
The approximate hydraulic grade line above the pipe invert is
1.540(Ft.) at the headworks or inlet of the pipe(s)
Pipe friction loss = 1.498(Ft.)
Minor friction loss = 1.142(Ft.)K-factor = 1.50
Pipe flow velocity = 7.00(Ft/s)
Travel time through pipe = 0.26 min.
Time of concentration (TC) = 8.75 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 7.000 to Point/Station 8.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 6.060(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 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Time of concentration = 8.75 min.
Rainfall intensity = 6.060(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.410 CA = 2.109
Subarea runoff = 0.408(CFS) for 0.259(Ac.)
Total runoff = 12.780(CFS) Total area = 5. 144(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 7.000 to Point/Station 8.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 682.600(Ft.)
Downstream point/station elevation = 674.000(Ft.)
Pipe length = 154.00(Ft.) Slope = 0.0558 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 12.780(CFS)
Given pipe size = 18.00(In.)
Calculated individual pipe flow = 12.780(CFS)
Normal flow depth in pipe = 9.15(In.)
Flow top width inside pipe = 18.00(In.)
Critical Depth = 16.13(In.)
5 Pipe flow velocity = 14.15(Ft/s)
Travel time through pipe = 0.18 min.
Time of concentration (TC) = 8.93 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 8.000 to Point/Station 9.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 5.980(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 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Time of concentration = 8.93 min.
Rainfall intensity = 5.980(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.410 CA = 2.168
Subarea runoff = 0.183(CFS) for 0.143(Ac.)
Total runoff = 12.963(CFS) Total area = 5. 287(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 8.000 to Point/Station 9.000 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ Rainfall intensity (I) = 5.980(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 DU/A or Less )
Impervious value, Ai = 0.100
Sub-Area C Value = 0.410
Time of concentration = 8.93 min.
Rainfall intensity = 5.980(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area
(Q=KCIA) is C = 0.410 CA = 2.227
Subarea runoff = 0.356(CFS) for 0.145(Ac.)
Total runoff = 13.318(CFS) Total area = 5. 432(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 8.000 to Point/Station 9.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 674.000(Ft.)
Downstream point/station elevation = 659.000(Ft.)
Pipe length = 155.00(Ft.) Slope = 0.0968 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 13.318(CFS)
Given pipe size = 24.00(In.)
Calculated individual pipe flow = 13.318(CFS)
Normal flow depth in pipe = 7.07(In.)
Flow top width inside pipe = 21.88(In.)
Critical Depth = 15.77(In.)
Pipe flow velocity = 17.22(Ft/s)
Travel time through pipe = 0.15 min.
6 Time of concentration (TC) = 9.08 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 9.000 to Point/Station 10.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 659.000(Ft.)
Downstream point/station elevation = 647.500(Ft.)
Pipe length = 171.00(Ft.) Slope = 0.0673 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 13.318(CFS)
Given pipe size = 24.00(In.)
Calculated individual pipe flow = 13.318(CFS)
Normal flow depth in pipe = 7.78(In.)
Flow top width inside pipe = 22.46(In.)
Critical Depth = 15.77(In.)
Pipe flow velocity = 15.11(Ft/s)
Travel time through pipe = 0.19 min.
Time of concentration (TC) = 9.27 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 9.000 to Point/Station 19.000 **** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________ Upstream point/station elevation = 647.500(Ft.)
Downstream point/station elevation = 646.500(Ft.)
Pipe length = 60.00(Ft.) Slope = 0.0167 Manning's N = 0.013 No. of pipes = 1 Required pipe flow = 13.318(CFS)
Given pipe size = 18.00(In.)
Calculated individual pipe flow = 13.318(CFS)
Normal flow depth in pipe = 14.48(In.)
Flow top width inside pipe = 14.27(In.)
Critical Depth = 16.33(In.)
Pipe flow velocity = 8.75(Ft/s)
Travel time through pipe = 0.11 min.
Time of concentration (TC) = 9.39 min.
End of computations, total study area = 5.432 (Ac.) 7 D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 9
EXHIBIT C
RATIONAL METHOD HYDROGRAPHS
Barham Drive Preliminary Design 5-Jun-20
P-1 to P-5,C Post Development Condition 8 Minute Hydrograph Entry Basin
Rational Method Unit Hydrograph 6 hr Storm
County of San Diego Hydrology Manual - Chapter 6 7.44 P6 Tc ^-0.645 Year
Area 7.458 ac Storm 2 P6 1.52 in P24 2.40 in 63% C 0.790 100 3.3 in 5.7 in 58%
Tc= 8.00
Tc= 8 minutes I2= 2.96 in/hr Q2= 17.43
Q2 = 17.43 cfs I100= 6.42 in/hr Q100= 37.83
Q100= 37.83 cfs 32,509 (201)
N= 45 Number of Precipitation Blocks Vol 32,308 1.20 0.62% Barham Drive 360 5-Jun-20
Qn = 60 C A Pn/Tc P-1 to P-5,C
Pt(n) = 0.124 P6 (n Tc)^0.355 Rational Method Hydrograph Transformation Pn = Pt(n) - Pt(n-1)
N Pt(n) Pn Q(n) Q(n) N Time Time Qn N Time Time Qn
(min) (hrs) (cfs) (min) (hrs) (cfs)
1 0.39 0.39 17.425 17.425
2 0.50 0.11 4.861 4.861 1 248 4.13 17.425 4 256 4.27 2.767 3 0.58 0.08 3.450 3.450 2 240 4.00 4.861 7 264 4.40 1.852 4 0.65 0.06 2.767 2.767 3 232 3.87 3.450 10 272 4.53 1.449 5 0.70 0.05 2.350 2.350 5 224 3.73 2.350 13 280 4.67 1.213 6 0.74 0.05 2.063 2.063 6 216 3.60 2.063 16 288 4.80 1.056 7 0.79 0.04 1.852 1.852 8 208 3.47 1.688 19 296 4.93 0.942 8 0.83 0.04 1.688 1.688 9 200 3.33 1.557 22 304 5.07 0.855 9 0.86 0.04 1.557 1.557 11 192 3.20 1.358 25 312 5.20 0.786 10 0.89 0.03 1.449 1.449 12 184 3.07 1.281 28 320 5.33 0.730 11 0.92 0.03 1.358 1.358 14 176 2.93 1.155 31 328 5.47 0.682 12 0.95 0.03 1.281 1.281 15 168 2.80 1.103 34 336 5.60 0.642 13 0.98 0.03 1.213 1.213 17 160 2.67 1.014 37 344 5.73 0.608 14 1.01 0.03 1.155 1.155 18 152 2.53 0.977 40 352 5.87 0.578 15 1.03 0.02 1.103 1.103 20 144 2.40 0.911 43 360 6.00 0.551 16 1.06 0.02 1.056 1.056 21 136 2.27 0.882 46 368 6.13 0.000 17 1.08 0.02 1.014 1.014 23 128 2.13 0.830
18 1.10 0.02 0.977 0.977 24 120 2.00 0.807
19 1.12 0.02 0.942 0.942 26 112 1.87 0.766
20 1.14 0.02 0.911 0.911 27 104 1.73 0.747
21 1.16 0.02 0.882 0.882 29 96 1.60 0.713
22 1.18 0.02 0.855 0.855 30 88 1.47 0.697
23 1.20 0.02 0.830 0.830 32 80 1.33 0.668
24 1.22 0.02 0.807 0.807 33 72 1.20 0.655
25 1.24 0.02 0.786 0.786 35 64 1.07 0.630
26 1.25 0.02 0.766 0.766 36 56 0.93 0.619
27 1.27 0.02 0.747 0.747 38 48 0.80 0.597
28 1.29 0.02 0.730 0.730 39 40 0.67 0.587
29 1.30 0.02 0.713 0.713 41 32 0.53 0.568
30 1.32 0.02 0.697 0.697 42 24 0.40 0.559
31 1.33 0.02 0.682 0.682 44 16 0.27 0.543
32 1.35 0.02 0.668 0.668 45 8 0.13 0.535
33 1.36 0.01 0.655 0.655
34 1.38 0.01 0.642 0.642
35 1.39 0.01 0.630 0.630
36 1.41 0.01 0.619 0.619
37 1.42 0.01 0.608 0.608
38 1.43 0.01 0.597 0.597
39 1.45 0.01 0.587 0.587
40 1.46 0.01 0.578 0.578
41 1.47 0.01 0.568 0.568
42 1.49 0.01 0.559 0.559
43 1.50 0.01 0.551 0.551
44 1.51 0.01 0.543 0.543
45 1.52 0.01 0.535 0.535
46 1.54 0.01 0.527 0.000
Barham Drive Preliminary Design 5-Jun-20
P-1 to P-5,C
Post Development Hydrographs - 6 Hour Rational Method
Ratio X/2 1.250 1.447 1.711 1.842 2.171 P6 Adj 1.52 1.9 2.2 2.6 2.8 3.3
Pre-Deve 7.317 9.146 10.590 12.516 13.479 15.886 Peak 17.425 21.781 25.220 29.806 32.099 37.831 2 Year Return /Yr
2 5 10 25 50 100
N Time Time Qn Vol Time Q(n) Q(n) Q(n) Q(n) Q(n) Q(n)
(min) (hrs) (cfs) (cf) (hrs)
0 0.00 0.000 0 0.00 0.000 0.000 0.000 0.000 0.000 0.000 45 8 0.13 0.535 128 0.13 0.535 0.669 0.774 0.915 0.985 1.161 44 16 0.27 0.543 259 0.27 0.543 0.678 0.786 0.928 1.000 1.178 42 24 0.40 0.559 265 0.40 0.559 0.699 0.810 0.957 1.031 1.215 41 32 0.53 0.568 271 0.53 0.568 0.710 0.823 0.972 1.047 1.234 39 40 0.67 0.587 277 0.67 0.587 0.734 0.850 1.004 1.082 1.275 38 48 0.80 0.597 284 0.80 0.597 0.747 0.864 1.022 1.100 1.297 36 56 0.93 0.619 292 0.93 0.619 0.773 0.896 1.058 1.140 1.343 35 64 1.07 0.630 300 1.07 0.630 0.788 0.912 1.078 1.161 1.368 33 72 1.20 0.655 308 1.20 0.655 0.819 0.948 1.120 1.207 1.422 32 80 1.33 0.668 318 1.33 0.668 0.835 0.967 1.143 1.231 1.451 30 88 1.47 0.697 328 1.47 0.697 0.872 1.009 1.193 1.284 1.514 29 96 1.60 0.713 338 1.60 0.713 0.891 1.032 1.219 1.313 1.548 27 104 1.73 0.747 350 1.73 0.747 0.934 1.081 1.278 1.376 1.622 26 112 1.87 0.766 363 1.87 0.766 0.957 1.109 1.310 1.411 1.663 24 120 2.00 0.807 378 2.00 0.807 1.009 1.169 1.381 1.487 1.753 23 128 2.13 0.830 393 2.13 0.830 1.038 1.202 1.420 1.530 1.803 21 136 2.27 0.882 411 2.27 0.882 1.102 1.276 1.508 1.624 1.914 20 144 2.40 0.911 430 2.40 0.911 1.138 1.318 1.558 1.678 1.977 18 152 2.53 0.977 453 2.53 0.977 1.221 1.413 1.670 1.799 2.120 17 160 2.67 1.014 478 2.67 1.014 1.268 1.468 1.735 1.869 2.202 15 168 2.80 1.103 508 2.80 1.103 1.378 1.596 1.886 2.031 2.394 14 176 2.93 1.155 542 2.93 1.155 1.443 1.671 1.975 2.127 2.507 12 184 3.07 1.281 584 3.07 1.281 1.601 1.853 2.190 2.359 2.780 11 192 3.20 1.358 633 3.20 1.358 1.698 1.966 2.323 2.502 2.948 9 200 3.33 1.557 700 3.33 1.557 1.946 2.253 2.663 2.868 3.380 8 208 3.47 1.688 779 3.47 1.688 2.110 2.443 2.887 3.109 3.664 6 216 3.60 2.063 900 3.60 2.063 2.579 2.986 3.529 3.800 4.479 5 224 3.73 2.350 1,059 3.73 2.350 2.937 3.401 4.019 4.329 5.102 3 232 3.87 3.450 1,392 3.87 3.450 4.313 4.994 5.902 6.356 7.491 2 240 4.00 4.861 1,995 4.00 4.861 6.077 7.036 8.315 8.955 10.554 1 248 4.13 17.425 5,349 4.13 17.425 21.781 25.220 29.806 32.099 37.831 4 256 4.27 2.767 4,846 4.27 2.767 3.459 4.005 4.734 5.098 6.008 7 264 4.40 1.852 1,109 4.40 1.852 2.314 2.680 3.167 3.411 4.020 10 272 4.53 1.449 792 4.53 1.449 1.811 2.097 2.478 2.669 3.145 13 280 4.67 1.213 639 4.67 1.213 1.517 1.756 2.076 2.235 2.634 16 288 4.80 1.056 545 4.80 1.056 1.320 1.529 1.807 1.946 2.293 19 296 4.93 0.942 480 4.93 0.942 1.178 1.364 1.612 1.736 2.046 22 304 5.07 0.855 431 5.07 0.855 1.069 1.238 1.463 1.575 1.856 25 312 5.20 0.786 394 5.20 0.786 0.982 1.138 1.344 1.448 1.706 28 320 5.33 0.730 364 5.33 0.730 0.912 1.056 1.248 1.344 1.584 31 328 5.47 0.682 339 5.47 0.682 0.853 0.988 1.167 1.257 1.482 34 336 5.60 0.642 318 5.60 0.642 0.803 0.930 1.099 1.183 1.395 37 344 5.73 0.608 300 5.73 0.608 0.760 0.880 1.040 1.120 1.319 40 352 5.87 0.578 284 5.87 0.578 0.722 0.836 0.988 1.064 1.254 43 360 6.00 0.551 271 6.00 0.551 0.689 0.797 0.942 1.015 1.196 46 368 6.13 0.000 132 6.13 0.000 0.000 0.000 0.000 0.000 0.000 0 5
10 15
20 25
30 35
40 0.0 1.0 2.0 3.0 4.0 5.0 6.0
Q (cfs)
Time (hrs)
Barham
Q
2 & Q100
6 Hr Hydrograph - Rational Method
I
I
I
I
I
I
1 1 ►
I i ►
I • ►
I • ►
.... ~/
--- --~
~ r--....
-
~ ~.
~ ◄
I ►
◄►
I ◄►
I ◄►
11 ◄►
11◄►
I ~ ►
I ~ ►
I • ►
I t ►
1 1 ►
I
I
I
I
I
I
I
I
I
I
I
I
I
I
■
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 10
EXHIBIT D
DETENTION BASIN
STORAGE INDICATION TABLE
Barham Drive Target 3.5' 0.430 0.194
Target @4' 4.296 0.208
P-1 to P-5,C Top 656.10 66,612 cf Depth 0.00 6.75 7.95 7.45 Storage @ Overflow 654.60 47,406 cf 1.09 Height 2.000 3 60 Basin Storage Volumes 140.52% dT= 8 dT= 15 Width 2.000 3 120 60 Elev 647.15 653.90 655.10 654.60
DEPTH ELEVATION AREA Void Volume STORAGE 2S/dT 2S/dT + O 2S/dT 2S/dT + O OUTFLOW #1 #2 #3 Overflow (FT) (SF) Ratio (CF) (CF) (CFS) (CFS) (CFS) (CFS) (CFS) (CFS) (CFS) (CFS) (CFS)
0.00 647.15 6,764 0.40 0 0 0.00 0.00 0.00 0.00 0.00 0.00
0.10 647.25 6,764 0.40 270.6 271 1.13 1.14 0.60 0.61 0.01 0.01
0.20 647.35 6,764 0.40 270.6 541 2.25 2.29 1.20 1.24 0.04 0.04
0.30 647.45 6,764 0.40 270.6 812 3.38 3.43 1.80 1.85 0.05 0.05
0.40 647.55 6,764 0.40 270.6 1,082 4.51 4.57 2.40 2.46 0.06 0.06
0.50 647.65 6,764 0.40 270.6 1,353 5.64 5.70 3.01 3.07 0.07 0.07
0.60 647.75 6,764 0.40 270.6 1,623 6.76 6.84 3.61 3.68 0.08 0.08
0.70 647.85 6,764 0.40 270.6 1,894 7.89 7.97 4.21 4.29 0.08 0.08
0.80 647.95 6,764 0.40 270.6 2,164 9.02 9.11 4.81 4.90 0.09 0.09
0.90 648.05 6,764 0.40 270.6 2,435 10.15 10.24 5.41 5.51 0.09 0.09
1.00 648.15 6,764 0.30 236.7 2,672 11.13 11.23 5.94 6.04 0.10 0.10
1.10 648.25 6,764 0.30 202.9 2,875 11.98 12.08 6.39 6.49 0.11 0.11
1.20 648.35 6,764 0.30 202.9 3,078 12.82 12.93 6.84 6.95 0.11 0.11
1.30 648.45 6,764 0.30 202.9 3,281 13.67 13.78 7.29 7.41 0.12 0.12
1.40 648.55 6,764 0.30 202.9 3,483 14.51 14.63 7.74 7.86 0.12 0.12
1.50 648.65 6,764 0.30 202.9 3,686 15.36 15.48 8.19 8.32 0.12 0.12
1.60 648.75 6,764 0.30 202.9 3,889 16.21 16.33 8.64 8.77 0.13 0.13
1.70 648.85 6,764 0.30 202.9 4,092 17.05 17.18 9.09 9.23 0.13 0.13
1.80 648.95 6,764 0.30 202.9 4,295 17.90 18.03 9.54 9.68 0.14 0.14
1.90 649.05 6,764 0.30 202.9 4,498 18.74 18.88 10.00 10.14 0.14 0.14
2.00 649.15 6,764 0.30 202.9 4,701 19.59 19.73 10.45 10.59 0.15 0.15
2.10 649.25 6,764 0.30 202.9 4,904 20.43 20.58 10.90 11.05 0.15 0.15
2.20 649.35 6,764 0.30 202.9 5,107 21.28 21.43 11.35 11.50 0.15 0.15
2.30 649.45 6,764 0.30 202.9 5,310 22.12 22.28 11.80 11.96 0.16 0.16
2.40 649.55 6,764 0.30 202.9 5,513 22.97 23.13 12.25 12.41 0.16 0.16
2.50 649.65 6,764 0.30 202.9 5,716 23.81 23.98 12.70 12.86 0.16 0.16
2.60 649.75 6,764 0.30 202.9 5,919 24.66 24.83 13.15 13.32 0.17 0.17
2.70 649.85 6,764 0.30 202.9 6,121 25.51 25.68 13.60 13.77 0.17 0.17
2.80 649.95 6,764 0.30 202.9 6,324 26.35 26.52 14.05 14.23 0.17 0.17
2.90 650.05 6,764 0.30 202.9 6,527 27.20 27.37 14.51 14.68 0.18 0.18
3.00 650.15 6,764 1.00 676.4 7,204 30.02 30.19 16.01 16.19 0.18 0.18
3.10 650.25 6,877 1.00 682.1 7,886 32.86 33.04 17.52 17.71 0.18 0.18
3.20 650.35 6,990 1.00 693.4 8,579 35.75 35.93 19.06 19.25 0.19 0.19
3.30 650.45 7,104 1.00 704.7 9,284 38.68 38.87 20.63 20.82 0.19 0.19
3.40 650.55 7,217 1.00 716.0 10,000 41.67 41.86 22.22 22.41 0.19 0.19
3.50 650.65 7,330 1.00 727.3 10,727 44.70 44.89 23.84 24.03 0.19 0.19
3.60 650.75 7,444 1.00 738.7 11,466 47.77 47.97 25.48 25.68 0.20 0.20
3.70 650.85 7,558 1.00 750.1 12,216 50.90 51.10 27.15 27.35 0.20 0.20
3.80 650.95 7,671 1.00 761.4 12,977 54.07 54.27 28.84 29.04 0.20 0.20
3.90 651.05 7,785 1.00 772.8 13,750 57.29 57.50 30.56 30.76 0.21 0.21
4.00 651.15 7,899 1.00 784.2 14,534 60.56 60.77 32.30 32.51 0.21 0.21
4.10 651.25 8,013 1.00 795.6 15,330 63.87 64.09 34.07 34.28 0.21 0.21
4.20 651.35 8,126 1.00 806.9 16,137 67.24 67.45 35.86 36.07 0.21 0.21
4.30 651.45 8,240 1.00 818.3 16,955 70.65 70.86 37.68 37.89 0.22 0.22
4.40 651.55 8,354 1.00 829.7 17,785 74.10 74.32 39.52 39.74 0.22 0.22
4.50 651.65 8,468 1.00 841.1 18,626 77.61 77.83 41.39 41.61 0.22 0.22
4.60 651.75 8,581 1.00 852.4 19,478 81.16 81.38 43.29 43.51 0.22 0.22
4.70 651.85 8,695 1.00 863.8 20,342 84.76 84.98 45.20 45.43 0.23 0.23
4.80 651.95 8,809 1.00 875.2 21,217 88.41 88.63 47.15 47.38 0.23 0.23
4.90 652.05 8,923 1.00 886.6 22,104 92.10 92.33 49.12 49.35 0.23 0.23
5.00 652.15 9,036 1.00 897.9 23,002 95.84 96.07 51.12 51.35 0.23 0.23
5.10 652.25 9,150 1.00 909.3 23,911 99.63 99.87 53.14 53.37 0.24 0.24
5.20 652.35 9,264 1.00 920.7 24,832 103.47 103.70 55.18 55.42 0.24 0.24
5.30 652.45 9,378 1.00 932.1 25,764 107.35 107.59 57.25 57.49 0.24 0.24
5.40 652.55 9,491 1.00 943.4 26,707 111.28 111.52 59.35 59.59 0.24 0.24
5.50 652.65 9,605 1.00 954.8 27,662 115.26 115.50 61.47 61.72 0.24 0.24
5.60 652.75 9,719 1.00 966.2 28,628 119.29 119.53 63.62 63.87 0.25 0.25
5.70 652.85 9,833 1.00 977.6 29,606 123.36 123.61 65.79 66.04 0.25 0.25
5.80 652.95 9,946 1.00 988.9 30,595 127.48 127.73 67.99 68.24 0.25 0.25
5.90 653.05 10,060 1.00 1,000.3 31,595 131.65 131.90 70.21 70.46 0.25 0.25
6.00 653.15 10,174 1.00 1,011.7 32,607 135.86 136.12 72.46 72.72 0.26 0.26
6.10 653.25 10,288 1.00 1,023.1 33,630 140.13 140.38 74.73 74.99 0.26 0.26
6.20 653.35 10,401 1.00 1,034.4 34,664 144.44 144.70 77.03 77.29 0.26 0.26
6.30 653.45 10,515 1.00 1,045.8 35,710 148.79 149.05 79.36 79.62 0.26 0.26
6.40 653.55 10,629 1.00 1,057.2 36,768 153.20 153.46 81.71 81.97 0.26 0.26
6.50 653.65 10,743 1.00 1,068.6 37,836 157.65 157.92 84.08 84.35 0.27 0.27
6.60 653.75 10,856 1.00 1,079.9 38,916 162.15 162.42 86.48 86.75 0.27 0.27
6.70 653.85 10,970 1.00 1,091.3 40,007 166.70 166.97 88.91 89.18 0.27 0.27
6.75 653.90 11,027 1.00 549.9 40,557 168.99 169.26 90.13 90.40 0.27 0.27 0.00
6.85 654.00 11,156 1.00 1,109.2 41,666 173.61 173.90 92.59 92.88 0.29 0.27 0.02
6.95 654.10 11,285 1.00 1,122.1 42,789 178.29 178.62 95.09 95.42 0.33 0.28 0.05
7.05 654.20 11,414 1.00 1,135.0 43,923 183.01 183.39 97.61 97.98 0.38 0.28 0.10
7.15 654.30 11,544 1.00 1,147.9 45,071 187.80 188.20 100.16 100.56 0.40 0.28 0.12
7.25 654.40 11,673 1.00 1,160.8 46,232 192.63 193.06 102.74 103.16 0.43 0.28 0.14
7.35 654.50 11,802 1.00 1,173.7 47,406 197.52 197.97 105.35 105.79 0.45 0.28 0.16
7.45 654.60 11,931 1.00 1,186.6 48,593 202.47 202.93 107.98 108.45 0.46 0.28 0.18 0.00
7.55 654.70 12,064 1.00 1,199.7 49,792 207.47 208.93 110.65 112.11 1.46 0.29 0.19 0.98
7.65 654.80 12,196 1.00 1,213.0 51,005 212.52 215.79 113.35 116.61 3.27 0.29 0.21 2.77
7.75 654.90 12,329 1.00 1,226.3 52,232 217.63 223.24 116.07 121.68 5.61 0.29 0.22 5.09
7.85 655.00 12,461 1.00 1,239.5 53,471 222.80 231.16 118.82 127.19 8.37 0.29 0.23 7.84
7.95 655.10 12,594 1.00 1,252.8 54,724 228.02 239.52 121.61 133.11 11.50 0.29 0.24 0.00 10.96
8.05 655.20 12,731 1.00 1,266.2 55,990 233.29 249.23 124.42 140.36 15.94 0.30 0.26 0.98 14.41
8.15 655.30 12,868 1.00 1,279.9 57,270 238.62 260.12 127.27 148.76 21.49 0.30 0.27 2.77 18.16
8.25 655.40 13,004 1.00 1,293.6 58,564 244.01 271.87 130.14 157.99 27.85 0.30 0.28 5.09 22.18
8.35 655.50 13,141 1.00 1,307.3 59,871 249.46 284.36 133.05 167.95 34.90 0.30 0.29 7.84 26.47
8.45 655.60 13,278 1.00 1,321.0 61,192 254.97 297.53 135.98 178.54 42.56 0.30 0.30 10.96 31.00
8.55 655.70 13,415 1.00 1,334.6 62,526 260.53 311.31 138.95 189.73 50.78 0.31 0.31 14.41 35.76
8.65 655.80 13,552 1.00 1,348.3 63,875 266.14 325.67 141.94 201.47 59.53 0.31 0.31 18.16 40.75
8.75 655.90 13,688 1.00 1,362.0 65,237 271.82 340.58 144.97 213.73 68.76 0.31 0.32 22.18 45.95
8.85 656.00 13,825 1.00 1,375.7 66,612 277.55 356.01 148.03 226.49 78.46 0.31 0.33 26.47 51.35
8.95 656.10 13,962 1.00 1,389.4 68,002 283.34 371.94 151.12 239.72 88.60 0.31 0.34 31.00 56.95
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 11
EXHIBIT E
DETENTION ROUTING
Barham Drive JN 75050.25
Tributary Areas Prelim Design 5-Jun-20
P-1 to P-5,C 7.458
Includes Basin - 6-Hour Rational Method Hydrograph Total 7.458 ac Total
Tc= 8 Elev Storage Storage Depth
(cf) (ac-ft) (ft)
Bottom of Storage 647.15 0
Floor of Basin
650.15 7,204 0.17 3.00
Surface Area @ 6" Depth 7,330 650.65 10,727 0.25 3.50
Surface Opening 3 653.90 40,557 0.93 6.75
Overflow Grate 654.60 48,593 1.12 7.45
I/O Weir
655.10 54,724 1.26 7.95
Top Of Berm 656.10 68,002 1.56 8.95
Storm Qexist Qin Qout WSEL Depth
Frequency (cfs) (cfs) (cfs) (ft) (ft)
10% Q2
2 YEAR 7.32 17.43 0.25 652.75 5.60
5 YEAR 9.15 21.78 0.26 653.45 6.30
10 YEAR 10.59 25.22 0.29 654.00 6.85
25 YEAR 12.52 29.81 0.46 654.60 7.45
50 YEAR 13.48 32.10 1.46 654.70 7.55
100 YEAR 15.89 37.83 5.61 654.90 7.75
Target
Outlet Control Structure Use 4' x 4' structure (Inside Dimension) Low Flow Surface Weir
Opening #1 #2 #3 Overflow - Grate
Elevation 647.2 653.9 655.10 654.6
Width (in) 2 3 0.0 4 feet
Height (in) 2 3 120.0 4 feet
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Detention Lots 1_2 6/16/2020 0 1 2 3 4 5 6 7 8
0 1
0,000
20,000
30,000
40,000
50,000
60,000
0 10
20 30
40 50
60 0 1 2 3 4 5 6 7 8
Flow Rate (cfs)
Time (hrs)
BARHAM DETENTION BASIN ~ 100-YEAR
Q100 in (cfs) Q100 out (cfs) Storage (cf)
' . 1
. I . • . I . • . . I • . . . .
I
i .
i:
~
• I • I • - 4
' . • I . . • I . . . • I • . . . . . . .
!
.
I
.
I
. .
i .
. .
~,-
. .
i
. .
•
.
!
. .
J
. . ~ . I\ 1 • . . . . . . . . • •
-~ .
i
i ' •
' . . . . . ' . . . --1
····· .. '
C - - - -
• lo • .1,,
. - - ... .. .. I,,,, x ...
-- - l ~ J
i- -
' .. . . '
- - -~ -.. ..
i--.. •
.. ~ ..
i
f"'
. ·~ . ""·
ii
·~. . i
. •,
\ i1
. . i1
. . . \ i1
. 11
. ' . II
' ~
. -ii . -.
. '
ii .
r. i1 .
~ . i1
··~ i . . i . I . i • I . i . . I i
~ • . I I . I ! . . I . I ; . • . I ! . . I . . I !
1 . I I . • . I! . .
I ! .
I
•~ I
. ! ,.,
;i
37.83 5.61 Q Out
100 YEAR EVENT ~ 6 Hour STORM 654.90 Max WSEL
8 Min 53.87 hrs Drain Time
Interval T Q IN 2S/dT+O 2S/dT-O O Basin
(HRS) (CFS) (CFS) (CFS) WSEL
1 0.13 1.161 0.00 0.00 0.00 647.15
2 0.27 1.178 2.34 2.27 0.04 647.35
3 0.40 1.215 4.66 4.54 0.06 647.55
4 0.53 1.234 6.99 6.84 0.08 647.75
5 0.67 1.275 9.35 9.17 0.09 647.95
6 0.80 1.297 11.74 11.54 0.10 648.15
7 0.93 1.343 14.18 13.95 0.12 648.45
8 1.07 1.368 16.66 16.40 0.13 648.75
9 1.20 1.422 19.19 18.91 0.14 649.05
10 1.33 1.451 21.78 21.48 0.15 649.35
11 1.47 1.514 24.44 24.12 0.16 649.65
12 1.60 1.548 27.18 26.83 0.17 649.95
13 1.73 1.622 30.00 29.65 0.18 650.05
14 1.87 1.663 32.93 32.58 0.18 650.15
15 2.00 1.753 35.99 35.62 0.19 650.35
16 2.13 1.803 39.18 38.80 0.19 650.45
17 2.27 1.914 42.52 42.14 0.19 650.55
18 2.40 1.977 46.03 45.64 0.19 650.65
19 2.53 2.120 49.74 49.34 0.20 650.75
20 2.67 2.202 53.66 53.27 0.20 650.85
21 2.80 2.394 57.86 57.45 0.21 651.05
22 2.93 2.507 62.35 61.94 0.21 651.15
23 3.07 2.780 67.22 66.80 0.21 651.25
24 3.20 2.948 72.53 72.10 0.22 651.45
25 3.33 3.380 78.43 77.99 0.22 651.65
26 3.47 3.664 85.03 84.58 0.23 651.85
27 3.60 4.479 92.72 92.26 0.23 652.05
28 3.73 5.102 101.84 101.37 0.24 652.25
29 3.87 7.491 113.96 113.48 0.24 652.55
30 4.00 10.554 131.52 131.02 0.25 652.95
31 4.13 37.831 179.41 178.75 0.33 654.10
32 4.27 6.008 222.59 216.05 3.27 654.80
33 4.40 4.020 226.07 214.86 5.61 654.90
34 4.53 3.145 222.03 215.49 3.27 654.80
35 4.67 2.634 221.27 214.73 3.27 654.80
36 4.80 2.293 219.66 213.12 3.27 654.80
37 4.93 2.046 217.46 210.92 3.27 654.80
38 5.07 1.856 214.82 211.90 1.46 654.70
39 5.20 1.706 215.46 212.54 1.46 654.70
40 5.33 1.584 215.83 209.29 3.27 654.80
41 5.47 1.482 212.35 209.43 1.46 654.70
42 5.60 1.395 212.31 209.39 1.46 654.70
43 5.73 1.319 212.10 209.18 1.46 654.70
44 5.87 1.254 211.75 208.83 1.46 654.70
45 6.00 1.196 211.28 208.35 1.46 654.70
46 6.13 0.000 209.55 206.63 1.46 654.70
Barham Drive 6/16/2020
47 6.27 0.000 206.63 205.70 0.46 654.60
48 6.40 0.000 205.70 204.77 0.46 654.60
49 6.53 0.000 204.77 203.84 0.46 654.60
50 6.67 0.000 203.84 202.92 0.46 654.60
51 6.80 0.000 202.92 202.02 0.45 654.50
52 6.93 0.000 202.02 201.13 0.45 654.50
53 7.07 0.000 201.13 200.24 0.45 654.50
54 7.20 0.000 200.24 199.35 0.45 654.50
55 7.33 0.000 199.35 198.46 0.45 654.50
56 7.47 0.000 198.46 197.57 0.45 654.50
57 7.60 0.000 197.57 196.71 0.43 654.40
58 7.73 0.000 196.71 195.86 0.43 654.40
59 7.87 0.000 195.86 195.01 0.43 654.40
60 8.00 0.000 195.01 194.16 0.43 654.40
61 8.13 0.000 194.16 193.31 0.43 654.40
62 8.27 0.000 193.31 192.46 0.43 654.40
63 8.40 0.000 192.46 191.65 0.40 654.30
64 8.53 0.000 191.65 190.84 0.40 654.30
65 8.67 0.000 190.84 190.04 0.40 654.30
66 8.80 0.000 190.04 189.23 0.40 654.30
67 8.93 0.000 189.23 188.43 0.40 654.30
68 9.07 0.000 188.43 187.62 0.40 654.30
69 9.20 0.000 187.62 186.87 0.38 654.20
70 9.33 0.000 186.87 186.12 0.38 654.20
71 9.47 0.000 186.12 185.36 0.38 654.20
72 9.60 0.000 185.36 184.61 0.38 654.20
73 9.73 0.000 184.61 183.86 0.38 654.20
74 9.87 0.000 183.86 183.11 0.38 654.20
75 10.00 0.000 183.11 182.45 0.33 654.10
76 10.13 0.000 182.45 181.79 0.33 654.10
77 10.27 0.000 181.79 181.13 0.33 654.10
78 10.40 0.000 181.13 180.47 0.33 654.10
79 10.53 0.000 180.47 179.81 0.33 654.10
80 10.67 0.000 179.81 179.15 0.33 654.10
81 10.80 0.000 179.15 178.49 0.33 654.10
82 10.93 0.000 178.49 177.91 0.29 654.00
83 11.07 0.000 177.91 177.32 0.29 654.00
84 11.20 0.000 177.32 176.74 0.29 654.00
85 11.33 0.000 176.74 176.16 0.29 654.00
86 11.47 0.000 176.16 175.57 0.29 654.00
87 11.60 0.000 175.57 174.99 0.29 654.00
88 11.73 0.000 174.99 174.40 0.29 654.00
89 11.87 0.000 174.40 173.82 0.29 654.00
90 12.00 0.000 173.82 173.27 0.27 653.90
91 12.13 0.000 173.27 172.73 0.27 653.90
92 12.27 0.000 172.73 172.19 0.27 653.90
93 12.40 0.000 172.19 171.65 0.27 653.90
94 12.53 0.000 171.65 171.11 0.27 653.90
95 12.67 0.000 171.11 170.56 0.27 653.90
96 12.80 0.000 170.56 170.02 0.27 653.90
97 12.93 0.000 170.02 169.48 0.27 653.90
98 13.07 0.000 169.48 168.94 0.27 653.90
Barham Drive 6/16/2020
D:\75051 Barham Drive\13 Reports\In-house Prelim Reports\Hydrology\Barham Prelim Drainage 2020 0615.docx Page 12
APPENDIX
COUNTY OF SAN DIEGO
HYDROLOGY MANUAL EXCERPTS
~ .. - ,. b
"' i:...
b
f'
~
b
" ~
"'
~
33°~0· ;:..',...--::: .. :=:.~ Ft= .It .. 33'30'
,;c/
····· .... ·::::~-- ~...... '·· ....
33°15 ,-_,,.,,,__ ----~ ·•. -~(}-< ~~--
· ...... ···:.7~ .. ··':.···
...... -<~~-
/_,··
...
-0
I))
C>
-· -
······ ·-"•-.
33 0
00, I -· ~, r - ~ I ·~ t : .' -~0 ~ · l C t b SOLANABEA~ g ~-\ ""'\ ••• /s'tco~~--:\:\ ~ ,) DEL r_ ·. · . _: _ _,._ ; .17 ·./ fi.'I' : ! ! \ _ ......... ,. / .. •·•, , - - / .,... j ;\:;\ .. \
. ,·7 \ __ \· ..
··.
..- ·- •• -r
..... \
~ .... ~-...
__ ••• q:.'1'1:f•"
3°00'
3 -0
CD
:::!.
Q1_
32°30' 32°30'
b ~ b ~ ~
~ ~ p ~
~ ~ ~ ~
~- County of San Diego
Hydrology Manual
Rainfall Isopluvials
100 Year Rainfall Event- 6 Hours
lsopluvial (inches)
DPW * GIS
~
S1tiGIS
(IMfflWOf~{'rNc,~
~~~ We Have San Dic~o (£1\-Cted!
N THISM>P ISPROVDEDWrrttOUTWARRANTYOF IWYKNO,ErrHEREXPRESS +
ORIMPlED , NCLIJONG, BUTNOTLMrTEOTO, THEf.tPI.IEDWAARANTES OF MERCHANTABLffY ANO FITNESS FOR A PARTCUI.AA PURPOSE. ~S-,OIS , AIR.lgl,tl~.
s
n. pn;,11u1;111-,cot1111nWonnlllDl!lnlmlheSAN!MOReglo!'9! E Horma!lan~whlctlcan:ilN/.-,uced.,._ ..
"""'""'P'"l!fflionDISANO,\a
Thllproduclmay-,lalln~whk:htw~r~fllllh
1)9tffl1Qiong,arnedbyThamu 11R>111!1n, Mapa,
3 0 3 Miles
f-
0 M
1-.. ~
1-.. ~ ,._
i:o
~ t
g
1D
~
County : .. :, , .. ty· .... ~ •. r Ir T ,· r r r r , 33'3 0' ~' ~- •:,~~ · "--' t t- t County of San Diego
Hydrology Manual
+-
. - :~j,/·
· .• 5 :(r·····
:·'
Riverside County . . ·- =---... ~-,;;.. .., -., ,· ... , i/1· •.. , . ' :~:~ ;~~L:~~ :; ::~~i·· <;~:; -~>:\ ::::.;\: ;>; : L? •~ . . \ \ '•~, C·..' ; . . .... 'tc.. ; 1 ........ , \ \ \ t·\\'• .. ..i i , .. . .. ~ j ~ I Ram/all Jsopluvzals 1 ~l:>i;·-.i./:;i <> >, \( ... . ·::::,-·(~.< -~r ....... ::: ... - --0
())
Cl
-· -.,,..
Cl
0 -c,
~
())
-:,
32'45' -------j---------- ~~
_(__.,//·~ J~
e
·~:~·--y.:::~~;:,;·• ... :.::\._
~ '!+ /' i 13'00'
/; ... ,"{·· .
'.. ;\::f ,, T
3 ::,
D .,
el
()
0 c:. ::,
,!) \?;i} ... ,
.z-
2'45'
··•,1
32' 30' 32'30'
b ..-- ft:, 0 [o -~ -- - ++- b LO M ~ 0 V M ~
t-- ... -- -- t-- t-- «> +--- to ~
100 Year Rainfall Event - 24 Hours
lsopluvial (inches)
DPW * GIS
~
SltiGIS
~r,/Adi:lotb!<I
~~.s-..a.- We Ha,•c ~ n Diego ( :/ll'crcd!
N TI,1$ MAP IS PROVIDED WmiOUT WAAR>NTY OF NfY KNO , EITHER EXPRESS 4 OR MPUEO. NCLUO~G , OUTNOTtMITEOTO , T1'1E t.ll'l.EOWAARANTES OF MERCHANTAII U TY AND FITNESS FOR A PARTICULAA PURPOSE. ~SanOIS . AI Rigra .........
s
Thilprod,.IClal'N)ll:Gnlllll"llnlonMdol'lhom111aSANO,,\ORegloni,I E WormlllonS)'l!lll!lwhld'I-DotNjlr'O(IUOld'Mltloullhll wrlllar,,:,1,mlH ionolS.V.C.,,,G ,
ThllproiM:tmll)l,:.o,ulnlrlomwllonwhid'lhubNr\,-proclucedwUh .,.,.......,.,granlldbyn.i.-8racharsMapa.
3 0 3 Miles
~
San Diego County Hydrology Manual
Date: June 2003
Table 3-1
Section:
Page:
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use
I
Runoff Coefficient "C"
Soil Tyee
NRCS Elements County Elements %IMPER. A B
Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 C
0.30 0.36
0.42 0.45
0.48 0.54
0.57 0.60
0.69 3
6 of26
D
~
0.41 0.46
0.49 0.52
0.57 0.60
0.63 0.71 D•t4-- ~o
High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 O.~ ~~ Commercial/lndustrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0.78 0.79 Commercial/lndustrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82 C01mnercial/lndustrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84 0.84 0.85 Commercial/lndustrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85 Commercial/lndustrial (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
.fl.
San Diego County Hydrology Manual
Date: June 2003
Section:
Page:
3 12 of26
Note that the Initial Tin;ie of Concentration should be reflective of the general land-use at the upstream end of a drainage basin. A single lot with an area of two or less acres does not have a significant effect where the drainage basin area is 20 to 600 acres.
Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in hydrology studies. Initial Ti values based on average C values for the Land Use Element are also included. These values can be used in planning and design applications as described below. Exceptions may be approved by the "Regulating Agency" when submitted with a detailed study.
Table 3-2
MAXIMUM OVERLAND FLOW LENGTH (LM)
& INITIAL TIME OF CONCENTRATION (Ti)
Element* DU/ .5% 1% 2% 3% 5% 10%
Acre LM Ti LM Ti LM Ti LM Ti LM Ti LM Ti
Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9 LDR 1 50 12.2 70 11.5 85 10.0 100 9.5 100 8.0 100 6.4
LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8
LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6
MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3
MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8
MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5
MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3
HDR 24 50 6.7 (65 ~6.1) 75 5.1 90 4.9 95 4.3 100 3.5
HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4 100 2.7
N.Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7
G.Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4
O.P./Com 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
General I. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9
*See Table 3-1 for more detailed description
3-12
San Diego County Hydrology Manual
Date: June 2003
SECTION 6
RATIONAL METHOD HYDROGRAPH PROCEDURE
6.1 INTRODUCTION
Section:
Page:
6 1 of 10
The procedures in this section are for the development of hydrographs from RM study results for study areas up to approximately 1 square mile in size. The RM, discussed in Section 3, is a mathematical formula used to determine the maximum runoff rate from a given rainfall. It has particular application in urban storm drainage, where it is used to estimate peak runoff rates from small urban and rural watersheds for the design of storm drains and small drainage structures. However, in some instances such as for design of detention basins, the peak runoff rate is insufficient information for the design, and a hydrograph is needed. Unlike the NRCS hydrologic method (discussed in Section 4), the RM itself does not create hydro graphs. The procedures for detention basin design based on RM study results were first developed as part of the East Otay Mesa Drainage Study.
Rick Engineering Company performed this study under the direction of County Flood Control. The procedures in this section may be used for the development of hydrographs from RM study results for study areas up to approximately 1 square mile in size.
6.2 HYDROGRAPH DEVELOPMENT
The concept of this hydro graph procedure is based on the RM formula:
Where:
Q=CIA
Q = peak discharge, in cubic feet per second (cfs)
C = runoff coefficient, proportion of the rainfall that runs off the surface (no units)
I average rainfall intensity for a duration equal to the Tc for the area, in inches per hour
A drainage area contributing to the design location, in acres The RM formula is discussed in more detail in Section 3. 6-1
San Diego County Hydrology Manual
Date: June 2003
Section:
Page:
6 2 of 10
An assumption of the RM is that discharge increases linearly over the Tc for the drainage area until reaching the peak discharge as defined by the RM formula, and then decreases linearly. A linear hydrograph can be developed for the peak flow occurring over the Tc as shown in Figure 6-1. However, for designs that are dependent on the total storm volume, it is not sufficient to consider a single hydrograph for peak flow occurring over the Tc at the beginning of a 6-hour storm event because the hydrograph does not account for the entire volume of runoff from the storm event. The volume under the hydro graph shown in Figure 6-1 is· equal to the rainfall intensity multiplied by the duration for which that intensity occurs (Tc), the drainage area (A) contributing to the design location, and the runoff coefficient (C) for the drainage area. For designs that are dependent on the total storm volume, a hydrograph must be generated to account for the entire volume of runoff from the 6-hour storm event. The hydro graph for the entire 6-hour storm event is generated by creating a rainfall distribution consisting of blocks of rain, creating an incremental hydrograph for each block of rain, and adding the hydrographs from each block of rain. This process creates a hydrograph that contains runoff from all the blocks of rain and accounts for the entire volume of runoff from the 6-hour storm event. The total volume under the resulting hydro graph is equal to the following equation:
Where: VOL= volume of runoff (acre-inches)
P6 = 6-hour rainfall (inches)
C = runoff coefficient
A= area of the watershed (acres)
6-2
(Eq. 6-1)
vi'
RUNOFF
Q)
.c:
(.)
g_
a.
I ( Tc
~
0 TIME (minutes)
FIGURE
Triangular Hydrograph
@]
San Diego County Hydrology Manual
Date: June 2003
6.2.1 Rainfall Distribution
Section:
Page:
6 4 of 10
Figure 6-2 shows a 6-hour rainfall distribution consisting of blocks of rain over increments of time equal to Tc, The number of blocks is determined by rounding Tc to the nearest whole number of minutes, dividing 360 minutes (6 hours) by Tc, and rounding again to the nearest whole number. The blocks are distributed using a (2/3, 1/3) distribution in which the peak rainfall block is placed at the 4-hour time within the 6-hour rainfall duration. The additional blocks are distributed in a sequence alternating two blocks to the left and one block to the right of the 4-hour time (see Figure 6-2). The total amount ofrainfall (PT(N)) for any given block (N) is determined as follows:
PT(N) = OT(N) T T(N)) / 60
Where: PT(N) = total amount of rainfall for any given block (N) h(N) = average rainfall intensity for a duration equal to T T(N) in inches per hour TT(N) = NTc in minutes (N is an integer representing the given block number of rainfall)
Intensity is calculated using the following equation ( described in detail in Section 3):
I= 7.44 p6 ffo.645
Where: I = average rainfall intensity for a duration equal to Din inches per hour P6 = adjusted 6-hour storm rainfall
D = duration in minutes
6-4
i .c:
0 C: :::.
(12Tc) (2Tc/60) - (ITcl (Tc/ 60)
(13Tc) (3Tc/60) - (l2Tcl (2Tc/60)
5 6
8 9
2 3
Time
Rainfall Distribution
(14Tc) (4Tc/60) - (13Tc) (3Tc/ 60)
4 7
"--4(hours)
FIGURE
San Diego County Hydrology Manual
Date: June 2003
Section:
Page:
6 6 of 10
Substituting the equation for I in the equation above for PT(N) and setting the duration (D) equal to T T(N) yields:
Substituting NTc for TT (where N equals the block number of rainfall) in the equation above yields:
(Eq. 6-2)
Equation 6-2 represents the total rainfall amount for a rainfall block with a time base equal to T T(N) (NTc), The actual time base of each rainfall block in the rainfall distribution is Tc, as shown in Figure 6-2. The actual rainfall amount (PN) for each block of rain is equal to PT at N (PT(N)) minus the previous PT at N-1 (PT(N-1)) at any given multiple of Tc (any NTc), For example, the rainfall for block 2 is equal to Pr(N) at T T(N) = 2Tc minus the PT(N) at T T(N) = 1 Tc, and the rainfall for block 3 equals PT(N) at T T(N) = 3Tc minus the PT(N) at T T(N) = 2Tc, or PN can be represented by the following equation:
(Eq. 6-3)
For the rainfall distribution, the rainfall at block N = 1, (1 Tc), is centered at 4 hours, the rainfall at block N = 2, (2Tc), is centered at 4 hours - 1 Tc, the rainfall at block N = 3, (3Tc), is centered at 4 hours - 2T0 , and the rainfall at at block N = 4, ( 4Tc), is centered at 4 hours+ 1 Tc, The sequence continues alternating two blocks to the left and one block to the right (see Figure 6-2).
6-6
San Diego County Hydrology Manual
Date: June 2003
6.2.2 Construction of Incremental Hydrographs
Section:
Page:
6 7 of 10
Figure 6-1 shows the relationship of a single block of rain to a single hydrograph.
Figure 6-3 shows the relationship of the rainfall distribution to the overall hydrograph for the storm event. The peak flow amount from each block of rain is determined by the RM formula, Q = CIA, where I equals IN (the actual rainfall intensity for the rainfall block).
IN is determined by dividing PN by the actual time base of the block, Tc, The following equation shows this relationship:
(Eq. 6-4)
Where: IN= average rainfall intensity for a duration equal to Tc in inches per hour PN = rainfall amount for the block in inches
Tc = time of concentration in minutes
By substituting equation 6-4 into the rational equation, the following relationship is obtained:
(Eq. 6-5)
Finally, the overall hydrograph for the storm event is determined by adding all the hydrographs from each block of rain. Since the peak flow amount for each incremental hydrograph corresponds to a zero flow amount from the previous and proceeding hydrographs, as shown in Figure 6-3, the inflow hydrograph can be plotted by connecting the peak flow amounts (see the dashed line in Figure 6-3). 6-7
i .c:
0 §,
0 0 5
Time (minutes)
VOLUME OF RUN
VOLUME UNDER
HYtO
NUMB
240 (4 hours)
t
i
240 (4 hours)
Time (minutes)
6-Hour Rational Method Hydrograph
360
(6 hours)
H
~
(6 hours)
FIGURE
~
San Diego County Hydrology Manual
Date: June 2003
6.3 GENERATING A HYDROGRAPH USING RATHYDRO
Section:
Page:
6 9 of 10
The rainfall distribution and related hydrographs can be developed usmg the RA THYDRO computer program provided to the County by Rick Engineering Company.
A copy of this program is available at no cost from the County. The output from this computer program may be used with HEC-1 or other software for routing purposes.
The design storm pattern used by the RATHYDRO program is based on the (2/3, 1/3) distribution described in Sections 4.1.1 and 6.2.1. The ordinates on the hydrograph are calculated based on the County of San Diego Intensity-Duration Design Chart (Figure 3- 1), which uses the intensity equation described in Sections 3.1.3 and 6.2.1 to relate the intensity (I) of the storm to Tc, I= 7.44 P6D"0·645• The computer program uses equations 6-2 and 6-3 described above and calculates IN directly. The intensity at any given multiple of Tc is calculated by the following equation:
Where: N = number of rainfall blocks
T T(N) = time of concentration at rainfall block N in minutes ( equal to NTc)
IN= actual rainfall intensity at rainfall block N in inches per hour (Eq. 6-6)
· lr(N) = rainfall intensity at time of concentration T T(N) in inches per hour Figure 6-2 shows the rainfall distribution used in the RM hydrograph, computed at ~ultiples of Tc, The rainfall at block N = 1, (1 Tc), is centered at 4 hours, the rainfall at 'block N = 2, (2Tc), is centered at 4 hours - 1 Tc, the rainfall at block N = 3, (3Tc), is centered at 4 hours - 2Tc, and the rainfall at at block N = 4, ( 4 Tc), is centered at 4 hours + 1 Tc, The sequence continues alternating two blocks to the left and one block to the right (see Figure 6-2).
As described in Section 6.2.2, the peak discharge (QN) of the hydrograph for any given rainfall block (N) is determined by the RM formula Q = CIA, where I = IN = the actual 6-9
San Diego County Hydrology Manual
Date: June 2003
Section:
Page:
6 10 of 10
rainfall intensity for the rainfall block. The RATHYDRO program substitutes equation 6-6 into the RM formula to determine QN yielding the following equation:
QN == [ (I T(N)) (T T(N)) - (I T(N-1 )) (T T(N-1 )) ] CA / Tc (Eq. 6-7) .
Where: QN == peak discharge for rainfall block Nin cubic feet per second (cfs) N == number of rainfall blocks
T T(N) == time of concentration at rainfall block N in minutes ( equal to NTc) h(N) == rainfall intensity at time of concentration T T(N) in inches per hour C == RM runoff coefficient
A== area of the watershed (acres)
To develop the hydro graph for the 6-hour design storm, a series of triangular hydro graphs with ordinates at multiples of the given Tc are created and added to create the hydro graph. This hydro graph has its peak at 4 hours plus½ of the Tc, The total volume under the hydro graph is equal to the following equation ( equation 6-1):
Where: VOL== volume of runoff (acre-inches)
P6 == 6-hour rainfall (inches)
C == runoff coefficient
A== area of the watershed (acres)
6-10
RATIONAL METHOD HYDROGRAPH PROGRAM
COPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
RUN DATE 8/23/2012
HYDROGRAPH FILE NAME Text1
TIME OF CONCENTRATION 7 MIN.
6 HOUR RAINFALL 0.95 INCHES
BASIN AREA 17.35 ACRES
RUNOFF COEFFICIENT 0.74
PEAK DISCHARGE 25.87 CFS
TIME (MIN)= 0
TIME (MIN)= 7
TIME (MIN)= 14
TIME (MIN)= _21
TIME (MIN)= 28
TIME (MIN)= 35
TIME (MIN)= 42
TIME (MIN)= 49
TIME (MIN)= 56
TIME (MIN)= 63
TIME (MIN)= 70
TIME (MIN) = 77
TIME (MIN)= 84
TIME (MIN)= 91
TIME (MIN)= 98
TIME (MIN)= 105
TIME (MIN)= 112
TIME (MIN)= 119
TIME (MIN)= 126
TIME (MIN)= 133
TIME (MIN)= 140
TIME (MIN)= 147
TIME (MIN)= 154
TIME (MIN)= 161
TIME (MIN)= 168
TIME (MIN)= 175
TIME (MIN) = 182
TIME (MIN) = 189
TIME (MIN) = 196
TIME (MIN) = 203
TIME (MIN)= 210
TIME (MIN)= 217
TIME (MIN)= 224
TIME (MIN)= 231
TIME (MIN)= 238
TIME (MIN)= 245
TIME (MIN) = 252
TIME (MIN) = 259
TIME (MIN)= 266
TIME (MIN)= 273
TIME (MIN)= 280
TIME (MIN)= 287
TIME (MIN)= 294
TIME (MIN)= 301
TIME (MIN) = 308
TIME (MIN)= 315
TIME (MIN)= 322
TIME (MIN)= 329
TIME (MIN)= 336
TIME (MIN)= 343
TIME (MIN) = 350
TIME (MIN) = 357
TIME (MIN) = 364
DISCHARGE (CFS) = 0
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS)= 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS)= 1.1
DISCHARGE (CFS) = U
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS) = 1.3
DISCHARGE (CFS) = 1.4
DISCHARGE (CFS) = 1.5
DISCHARGE (CFS) = 1.6
DISCHARGE (CFS) = 1.8
DISCHARGE (CFS) = 2
DISCHARGE (CFS) = 2.3
DISCHARGE (CFS)= 2.7
DISCHARGE (CFS) = 3.5
DISCHARGE (CFS) = 5.1
DISCHARGE (CFS) = 25.87
DISCHARGE (CFS) = 7.2
D1$CHARGE (CFS) = 4.1
DISCHARGE (CFS)= 3.1
DISCHARGE (CFS) = 2.5
DISCHARGE (CFS) = 2.2
DISCHARGE (CFS) = 1.9
DISCHARGE (CFS)= 1.7
DISCHARGE (CFS) = 1.6
DISCHARGE (CFS)= 1.4
DISCHARGE (CFS) = 1.4
DISCHARGE (CFS) = 1.3
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS)= 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS)= 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS) = 0
EXHIBIT
FOR:
JOB
NAME
/
I
I
/
s
?i '
'
'
' j
1 1
•
I
i
I
' ' ',
I j I I
/
' I
I
I
,
I I ,
' '
I
'
I I \' I
\
! I I i ( ) !' I
, (
I ,
< I
I I I ' )
I
I
I ) '
' II
I
I
I
I !
I
i
I
(
i /
(
)
I
(
/
I
I '
' I I
I
\
.
I
I
I \ I
I
) '
I
I
\
I
I
I
I
I I I
l
)
\ '
I I I I
\
, I
)
J
__.1~\
i i'i
(
I
I
!
~ ... f
I
sc~1,
~·
'
\
'
'
GRAPHIC
SCALE
---
-
--- -
PLANNING
ENG
INEER
ING
SURVEYING
3990
Ruff
in
R
aad
, Suite
120
c:i
San
Diego
, Ca
. 92123
~
858-560-11
41 :
40 O
40 80
120
8 58-560-81
57 Fax
,..,
L=----------------------------------------------------------------------;;;-;:;t "
JOB
NO
,
DATE
\
)/
I I \ \ j
(
( I
\ \ I
\
\
I I I '
'I
I
I '
,,
1111
11 1,,
'""
,,
,'1-l
1 : " '
,,,.
·•...
689.5
f
{IN)
)
684
.5
(OUT.
TYPE:
T"
C.B
5 11
.J
E-2
,
"'
'
'
';
I
,'
I
I'
,
,' I / /
,1 ,'
I
,
/
688
.8
f
lN
685.2
f
{OUT)
;-•
C.B
4 11
.0
r
I
'I I I
E-3
;/ I
,.
,;1,1'11111,111
/
/
'
PROPOSED
DRAINAGE
EXHIBIT
FOR,
BARHAM
DRIVE
'
'
'
'
I
I I
I '
!
'
c:6::::92:::;.
O:....:...:F.:::.C
. +--1
.Jc...._i
@ I
;,i
/~'1;
I '
I I ,
'
'
'
6885
r.c.
15 o.'ax '
I
I I I
I/
I
I
I
I I
@
w
'""
'
'
I ' '
I
, :·_·._ .... ,1-:
·/--
. I
.....
.
rj . . ..
.
. ..
.. :_::_;_ I
.
.
. .
'
...
..
.
. . .
. . .
! ... .. ."•. ' ..
I
.. ,.
.
. . .
. ..
. . .
-.
,'
I
'
1 I
\
\~
rn⇒
jj
( PROPOSED
STO
M
DRAIN
(PRIVATE)
2.3 ,
...,
\
o"i
'
'
I ' '
P-3 0.6471 P-4 0.5590
\ !
0. 10
.
·-o.8
'
I ) I I
I I I
I I I
I
I
i ' I I I I I/ I
LFG£ND D£SCRIPTION PROPERTY
LINE/PROJECT
BOUNDARY
PROPOSED
CURB
AND
GUTTF:R
EXISnNG
CONTOUR
SYMBOL
-----·---......._____6
30-----__/
646
.8
F.S.
20 I
I
I
J
PROPOSED
DMA
LIMITS
------
644
.0
f
s.o.c.o.
C
0. 466
3 I '.::
I I I I I
I I I : '
I I I
I
I l I
r
I ' I '
I ' I
L-
+
/f-l-i --t-~
EXIST.
STORM
\
f
DIRECnON
OF'
DRAINAGE
STORM
DRAIN
PIPE
SIZE
PER
Pl.AN
NODE
NUMBER
-===========60~1TgJ-~El.£Y."ff!'-
Q100
(C.F'.5.)
~
£
.
BASIN
IDENnFIER
---=========1=1£~5~1
BASIN
AREA
(AC.)
-
I. 960
0 .
I I
DRAIN
/MS-4)
(
\
j /
l'
\
/!
11,
01,,:
I
I
I
I /
1 I
I
l :
\
:-tH
-++!1-11-t-
--l-~W.-, W
-
cA
TCH
BASIN
I ''
1 )
1 AND
DITCH
1 , ,
1: ,
\
j
I
(
\
I
I
I
I
I
I
11 1
'
rn,--..__
l
POC-1
PROPOSED
, / i
I
>
r--...::6:::::'16:c:,:
,5;:...;,,.-+...:.
1:.-9
+I
\
II
CLEANOUT
I
I
7 s.o
.c.o/j
r
I
I
/iii
I !
I
~
I
I
I I
\ I
I
(
r--.:
6:..::48:::.5::,_:;,T.
C.:::,,
+--1,;_8
-11
I
I I
I I
(
647.o
c
1,
~
/
I'
.11.W.S.
'--1 ./1
~
I \
:
-1
I
!!
·
1 VI
,
/
'
W
-4
~
+--+Hn
~i---+fl~
,-
PROPOSED
BIOFILTRATION
I
I 11·
I
I
>--
+-
-tr.-
-;-
-
1'
1 I
'
I
I
I!
1 BASIN
I
I
I
,
1 1
r'
AND
Tw1A
1 1
I !
I
I I
11 /!
1 l\1''\1'·'
,I
Ii
/
/
-e.J!
\
A
2 \
\
-'--.!.
1;
41 0.0;16
I
, , )
i
l~
i.;(
111/
I
11 l
1 )
I
I
±t\t-+--1.1+-
-b
I 11
l j
I
I
I
I
I \
.i
I
•
I
'
11 I
11 --
I
I I
} i I I
'1
I
l
I
A-1
\
I
1-rt--+;.
-l--:
w!J!
I-W
a1117
I
. I '
I I i!
I ' I I
)
I I I I I I I l I I I I I I I
I
I I 11
I
)
l '<,;,
I
\
I
9',,
I
11 (I
I
i l i I~
I
i I
,r
I
I \
I I
'(' l'
I I
I
I
J
I I
I
I
I
1·
l I
1 l
J
l
i
I lj i
j
q, I I l I
I I i J I '}
'.
I
I I
I
I
I
. I
' I
I
I\
I : , I
I , I I
' •
I '
)
r l , \ '('
'
II
I I I'
~~~
'
ll
l--~---1
.1
I
j i
'
)
I
I
i ,
I
,-,: '-
0.7198
~
,
-
"
,I!
"'
'
Ii
!;
I
I!
I ;:
I:
1 I
Qi
I
!
I
.
I
'
:,
I
I
I
I:
! !
I
I I
I
I
I I I I I I
!
I l
I
I
J
If]
I/
I
j /
I' j ! ' . ' \ 1 " ) I " "
I
I
/!/I' I " : ! " " " " " " " 1/
I I
\
TW2
AND
TW2A
A-3 0.
1018
A-5 0.0.149
I (
I
I
I
l
I
I
I I
I
I
I '\
I
<
', ' I
I r r I , , '
, I ) I
I
I
I 11
' I
I I )
I I \
I
I
/ I
I
I ( I ' I
I ( ( I
) I
' I
I
I'
'
I I
) \ I )
I I ' I
I
I
I
I
I
I
I I
i I
I
j
I
I
I
I
f
( I
I
I '
)
J
I I
l
I I '
I I
I I I I
'I
I
' I
I
/ I
(
I
.,-
I
GRAPHIC
SCALE
---
-
--- -
PLANNING
ENG
INEER
ING
SURVEYING
3990
Ruff
in
R
aad,
Suite
120
Q
San
D
iego,
Ca
. 92123
~
858-560-11
41 :
'=':3io=:i-:0----------------------------------------------------------------------------------------------------------------------------•::o'.,_ _ __:o:.,_
__
•::o'.,_
_
_'.:8:'.'._0
__
_;1~20~B:;:
5~8-6~SO-~B2;
15;:;7:'.F::a:_x
____
....,,,,.,,.,,J
•
6-J0-20
c
75050.25