HomeMy WebLinkAboutCDP 01-35; PATEL RESIDENCE; HYDROLOGY STUDY; 2002-10-25-I
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HYDROLOGY STUDY
FOR
1280 Hoover Street
INTHE
CITY OF CARLSBAD
COUNTY OF SAN DIEGO, CALIFORNIA
October 25, 2002
Armstrong & Brooks Consulting Engineers
1530 Consumer Circle, Unit B
Corona, CA 92880
PZZB'2~
William D. Brooks
R.C.E. 53114 --~------_____ _
EXPIRES f (/:J3/~$
I JN 101.273
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TABLE Ot= CONTENTS
Introduction and Narrative................................................................ I -1
Hydrologic Data............................................................................. II -1
100-Year On-site Hydrology Calculations (Unit Hydrograph for detention... Ill -1
basin sizing )
Predevelopment
Postdevelopment
10-Year Rational Method Hydrology Study.............................. Appendix "A"
Drainage Exhibit.................................................................. Appendix "B"
Armstrong & Brooks Consulting Engineers
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INTRODUCTION AND NARRATIVE
Armstrong & Brooks Consulting Engineers
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A. lNTRODucr10N.
The purpose of this hydrology study is to determine the final 100-year onsite
stormwater runoff quantities for the residential property located at 1280 Hoover
Street in the City of Carlsbad. The proposed ohsite drainage patterns and storm
drain system will convey the runoff in a safe and non-destructive manner into the
existing 3-foot wide PCC drainage V-gutter and then downstream to an existing
8-inch CMP storm drain pipe. Downstream of the 8-inch storm drain pipe, there
are a series of concrete ·lined open triangular shaped channels which discharge
into a public catch basin at Adams St. There is an apparent 18-inch RCP storm
drain under Adams Street southerly to another catch basin on the south side of
the street. An apparent 18-inch RCP storm drain is connected to this catch basin
at a 45-degree angle and discharges into an open triangular shaped channel,
which flows southerly to the Ocean. The approximate schematic drainage
system downstream of the subject property is located in Appendix "B" of this
report.
8. EXISTING SITE.
The project occupies approximately 0.51 acres and is located southwesterly of
the intersection of Highland Avenue & Hoover Street in the City of Carlsbad.
The site address is 1280 Hoover Street (APN 206-150-2100).
The existing undeveloped site elevations range from about 142' at the
northeastern comer of the site to 117' at the southwest corner of the
development.
C. Proposed ''ON-SITE" Development.
The site will be developed with a residential building. Site drainage will be
accomplished through a series of on-site l;>Urface swales, storm drain pipes and
drainage basins. Drainage easements exist on the downstream property to
accept the discharge from the site as shown on note "A" of Parcel Map No.
16658. The existing drainag·e patterns from off-site properties will be maintained
. in the current condition. Flows form Parcel 1 (PM 16041) will continue to flow
unobstructed to the existing PCC V-gutter. Off-site flows from the north (Lot 2
Bella Vista Block B) will be intercepted on-site .in earthen swales and directed
westerly and southerly to the existing PCC V-gutter.
We propose to mitigate the development's flows through the use of a grassy
infiltration and retention basin consistent with the California Regional Water
Quality Boards Best Management Practic~s. The basin was sized to retain the
difference between the predevelopment and post development runoff from a 100-
year six-hour storm. The calculations were performed by the San Diego County
Unit Hydrograph Method and are included herewith for reference. The program
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only allows project areas with a minimum size area of 1-acre. We simply
reduced the area required on a prorated basis of 0.51 (project area divided by 1
acre)
The predevelopment total rnn-off was calculated at 4,530 cubic feet and a total
peak discharge of 1 .18 c.f.s. for a project consisting of 1-'acre. The post
development total runoff was calculated at 5,266 cubic feet at a peak discharge
1.37 c .. f.s. (or 0.61 c.f.s. for our site area). Therefore the theoretical required
retention basin is (5,266-4,530) =736 cubic feet for a one -acre project. For our
0.51 acre project site we calculated a run-off volume of 736 * (times) 0.51 = 375
cubic feet. We have provided over 900 cubic feet on the proposed grading plans.
As requested by the City of Carlsbad, we ?lso analyzed the site using the
Rational Method for San Diego County. We based our calculations on the 10-
year storm event with 6 and 24-hour precipitation duration periods. A 10-year
peak discharge was calculated at 0.87 C.f.s. for the approximately 0.5 acres
tributary to. the detention basin. Our time of concentration was calculated at 9 .12
minutes. All related data for the Rational Method is listed in Appendix "A" of this
report together with the hydrology map. This design "Q" is compares well with
the unit hydrograph calculations, which are required to obtain a storm runoff
volume.
D. CALCULATIONS.
Software designed by "CivilDESIGN of San Bernardino was used to solve the
drainage models of the site. The output i~ printed in the standard San Diego
County format. The following criteria were used to perform the hydrology
calculations:
1. Rainfall
The design rainfall isopluvials were inputted into the program as 3.0-inches
for a 24-hour duration (10-year) and 1.8-iliches for (10-year), 6-hour duration.
2. Infiltration
Soil type "D" was used throu'ghout the site based on a review of the
hydrologic soils group map for Carlsbad.
3. Runoff and Routing
The Soil Conservation Serve SGS number was calculated based on the soil
types, antecedent moisture conditions and percent imperviousness.
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F. DESIGN CRITERIA
The following City of Carlsbad and County of San Diego design criteria was
used:
1. All buildings shall be protected from flooding during the 100-year frequency
storm .
2. The 50-year, 6 hour storm must be contained within curbs in public streets.
3. The 100-year storm must be contained within the public right-of-way.
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HYDROLOGIC DATA
. .
Armstrong & Brooks Consulting Engineers
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----------------~} ----courrrv OF SAN D I~GO
-DEPARTMENT OF SANITATION &
FLOOD CONTROL
45 1
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33°
' ._, ... ~
45' I I l __ /! . :l,n, ,m.1.11 I 7'l
Prrpn+,d by
U.S. DEPARTMENJr OF COMMERCE
NATIONAL OCEANIC AND AT~OSPIIERIC ADMINISTRATION
SPECIAi. STUDIES BRANCH, OFFICE OF llf DROLOGY, NATIONAL WEATHER SERVICE
----, ---1 ~-t--~-t I 30• "i -I
1 J 81 45 1 30 1 )5 I 117° l~5 I 30 1 15 I I 16°
Revised 1/85 APPENDIX XI-E
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100-YEAR "On-Site" HYDROLOGIC CALCULATIONS
Armstrong & Brooks Consulting Engineers
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UNIT HYDROGRAPH ANALYSIS
Copyright (c) CIVIJJCADD/CIVILDESIGN, 1990 -1999, Version 6. 0
Study date 10/25/02 File: 101273a.out
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Armstrong Deveioprnent & Brooks Consulting Engineers -S/N
Hydrology Study for new development
1280 Hoover Street, City of Carlsbad, California
Predevelopement 100 yr.-9 hr design storm
Armstrong & Brooks Consulting Engineers
785
+++++++++++++++++++++++++++++++~++++++++++++++++++++++++++++++++++
Storm Event Year= 100
Antecedent Moisture Condition= 3
English (in-lb) Input Units Used
English Rainfall Data (Inches) Input Values Used
Area averaged rainfall isohyetal data:
Sub-Area (Ac.) Rainf1;ll (In)
0.51 2.75
0.49 2.75
Rainfall Distribution pattern used in study:
Type B for SCS (small darn) or San Diego 6 hour storms
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
********* Area-Averaged SCS C!urve Number and Fm *********
Area Area SCS CN SCS CN Fm Soil
(Ac.) fract (AMC2:) (AMC3) (In/Hr) Group
0.51 0.510 65.0 83.0 0.000 D
0.49 0.490 65.0 83.0 0.000 D
Area-averaged catchment scs Curve Number AMC(3) = 83.000
Area-averaged Fm value using vaiues listed= 0.0O0(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Using U.S. Army Corps of Ensineers formula for lag time
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lag= 24 n ( L(Mi) Lc(Mi) /Slope(Ft/Mi) ) ,,._ 0.38
Watercourse length = 300. oo (Ft.)
Length from concentration point to centroid=
Elevation difference along watercourse=
Mannings friction factor al9ng watercourse
2 4 0 . 0 0 ( Ft . )
25.00(Ft.)
Watershed area = 1. 00 (Ac.)
Catchment Lag time = o. 020 hours
Unit interval= 5.000 minutes
(n) = 0.025
Unit interval percentage of lag time= 424.9511
Hydrograph baseflow = 0.00(GFS)
Minimum watershed loss rate(Fm) = 0.00l(In/Hr)
Average adjusted SCS Curve Number= 83.000
Rainfall depth area reduction factors:
Using a total area of 1. 0 0 ('Ac. ) (Ref: SCS Sup A, Sec. 4)
Pacific Coastal Climate ratio used
Areal factor ratio (rainfall reduction) = 1.000
Rainfall entered for study= 2.750(In)
Adjusted rainfall = 2. 750 (In)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
The following unit hydrograph was developed using an S-Graph
interpolated by time percenta~e of lag time vs. percentage of peak
flow.
is
The s~Graphs for Valley, Foothill, and Mountain were developed by the
U.S. Army Corps of Engineers for use in the respective type of
basins located in Southern Calif'ornia. (Hydrology San Gabrial River
U.S. Engineer Office, Dec 1944, revised Jul 1946) The Desert S-Graph
from Report ... on ... Tahquitz Creek, California, same U.S. offfice,
Corps of Engineers, June 1963. The Valley Developed S-Graph is used
by Orange and San Bernardino counties in California to represent the
characteristics of valley areas with a large amount of development.
~ecause of the wide variety in topography in Southern California,
these
synthetic unit hydrographs were included for use as options in any
geographic location.
The SCS(Soil Conservation Service Dimensionless S-Graph, SCS
handbook,
of 1972, applies to a broad cross section of geographic locations and
.hydrologic regions.
The User Defined hydrograph converts the user Q/Qp
vs. T/Tp values into an S-Graph based on lag= Tp/0.9. Then, for the
lag time used, the S-Graph in interpolated in time% of lag.
The following S-Graph or S-Graph combination is used in this study:
FOOTHILLS-Graph
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UNIT HYDROGRAPH
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
Time Ratio
(t/Lag)
4.25
8.50
Time
(hrs)
(K =
0.083
0 .J,.67
Discharge
Ratios
(Q/Qp)
12 .10 (CFS))
1.000
0.447
Q
(CFS)
8.360
3.740
Mass Curve
Ratios
(Qa/Q)
0.691
1. 000
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
For each time interval of the 6 or 24 hour storm, the total rainfall
up to that storm time is calculated. Then the Soil Conservation
Service
SCS (~eport 1972, 1975) area averaged Curve Number (CN) is used to
determine the amount of direct runoff in (In) using the following
equations:
(P -Ia) "2
Q
P -Ia+ S
Where:
Q = direct runoff, P = depth of precipitation, Ia= Initial
Abstraction
the
Min
and Sis the watershed storage in inches. Sand Ia are given by the
following equations:
1000
s -----------. -10· and Ia= 0.2 S
CN
Note: If Metric (SI) Units are used, rainfall data is converted by
the program internally into inches for these calculations.
Note: In the following printout, the revised runoff column is only
used when the minimum soil loss rate, fm, exceeds the normal
loss rate of delta P(dP) -delta Q{dQ) then the dP-dQ column
equals fm = 0.00l(In) (for time interval= 0.000(In)) and
revised runoff is shown in the last column.
Time Total Total SCS Rainfall Runoff
Period Rainfall Runoff Amount Amount
(hours) (In) (In) (In) (In)
Infiltr-Revised
at ion Runoff
(In) Loss
Rate
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I p Q dP dQ dP-dQ
------------------------------------------------------------------
I 0.08 0. 0160 0.0000 0.0160 0.0000 0.0160 --------
0.17 0. 0321 0.0006 0. 0160 0.0000 0.0160 --------
0.25 0.0481 0.0000 ·0.0160 0.0000 0.0160 --------
I 0.33 0. 0642 0.0000 0. 0160 0.0000 0.0160 --------
0.42 0. 0802 0.0000 0. 0160 0.0000 0.0160 --------
0.50 0. 0963 0.0000 0.0160 0.0000 0.0160 --------
0.58 0 .1178 0.0000 0 •. 0215 0.0000 0.0215 --------
I 0.67 0 .1393 0.0000 0 ."0215 0.0000 0.0215 --------
0.75 0. 1609 0.0000 0.0215 0.0000 0.0215 --------
6.83 o·.1s24 Q.0000 0.0215 0.0000 0.0215 --------
I 0.92 0.2040 0.0000 0.0215 0.0000 0.0215 --------
1.00 0.2255 0.0000 0. 0215 0.0000 0.0215 --------
1.08 0.2521 0.0000 0.0266 0.0000 0.0266 --------
1.17 0.2787 0.0000 0.0266 0.0000 0.0266 --------
I 1.25 0. 3053 b.0000 0. 0266 0.0000 0.0266 --------
1.33 0.3318 0.0000 0.0266 0.0000 0.0266 --------
1.42 0.3584 0.0000 0. 0266 0.0000 0.0266 --------
I 1.50 0.3850 0.0000 0.0266 0.0000 0.0266 --------
1.58 0.4263 0.0001 0.0413 0.0001 0. 0411 --------
1.67 0.4675 0.0016 0.0412 o. 0·015 0.0398 --------
1. 75 0. 5088 0.0046 0.0413 0 .. 0030 0.0383 --------
I 1.83 0.5500 o .. o o~o 0. 0413 0.0044 0.0368 --------
1.92 0. 5913 Q.0148 0. 0413 0.0058 0.0355 --------
2.00 0. 6325 0.0219 0. 0413 0.0071 0.0342 --------
I 2.08 0.8021 .0.0631· 0.1696 0. 04.12 0.1283 --------
2.17 0. 9717 0.1210 0.1696 0.0579 0.1117 --------
2.25 J.. 1413 0.1926 0.1696 0.0715 0.0980 --------
2.33 1. 3108 0.2754 0.1696 0.0828 0.0868 --------
I 2.42 1. 4804 0.3676 0.1696 0.0922 0.0773 --------
2.50 1. 6500 0.4678 0.1696 0.1002 0.0694 --------
2.58 1. 6958 0. 4961-0,0458 0.0283 0.0175 --------
I 2.67 1. 7417 0.5249 0.0458 0.0288 0. 0171 --------
2.75 1. 7875 0.5541 0.0458 0. 0292 0.0166 --------
2.83 1.8333 0.5838' 0.0458 0.0297 0.0162 --------
2.92 1. 8792 0.6139 0. 0·459 0.0301 0.0157 --------
I 3.00 1 .. 9250 0.6444 0.0458 0.0305 0.0153 --------
3.08 1.9621 0.6694 0.0371 0.0250 0.0121 --------
3.17 1. 9993 0.6946 0.0371 0.0252 0. 0119 --------
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3 .. 25 2. 0364 0.7201 0.0371 0.0255 0.0116 --------
3.33 2.0735 0.7458 0.0371 0.0257 0.0114 --------
3.42 2 .1106 0. 7717 0.0371 0.0259 0. 0112 --------
3.50 2 .1478 0.7979 0.0371 0.0262 0.0110 --------
I 3 .,58 2. 1725 o .. 8.154 0.0248 o. OP6 0.0072 --------
3.67 2 .1972 0.8331 0.0247 0.0176 0. 0071 --------
3.75 2. 222.0 0.8508 0. 0248 0.0177 0.0070 --------
3.83 2. 24.68 0.8687 0.0248 0.0178 0.0069 --------
I 3.92 2. 2715 0.8866 0.0248 0.0179 0.0068 --------
4.00 2. 2962 0.9046 0.0247 0.0180 0.0067 --------
4.08 2. 3169 0. 9196 O.Q206 0.0151 0.0056 --------
I 4.17 2. 3375 0.9348 0.0206 0.0151 0.0055 --------
4.25 2.3581 0.9499 0.0206 0.0152 0.0054 --------
4;. 33 2.3788 0.9652 0.0206 0.0152 0.0054 --------
4.42 2. 3994 0.9805 0.0206 0. 0153 0.0053 --------
I 4.50 2. 42 00 0.9958 0.0206 0.0153 0.0053 --------
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4.58 2 .. 43.97 1.0105 0.0197 0.0147 0.0050 --------
4.67 2.4594 1.0253 0.0197 0.0148 0.0049 --------
4.75 2 .4791 1. 0401 0.0197 0.0148 0.0049 --------
4.83 2.4988 1.0549 0.0197 0.0149 0.0049 --------
4.92 · 2 .5185 l.0699 0.0197 0.0149 0.0048 --------
5.00 2.5383 1.0848 0.0197 0.0149 0.0048 --------
5.08 2.5552 1. 0977 0.0170 0.0129 0.0041 --------
5.17 2. 5722 1.1106 0.0170 0.0129 0.0040 --------
5.25 2.5891 1.1236 b.0170 0.0130 0.0040 --------
5.33 2.6061 1.1366 0.0170 0.0130 0.0040 --------
5.42 2.6230 1,1496 0. 0170 0.0130 0.0039 --------
5.50 2. 64-00 1.;l:627 0.0170 0.0131 0.0039 --------
5.58 2.6583 1.1768 0.0183 0.0141 0.0042 --------
5.67 2.6767 1.1910 0.0183 0.0142 0.0041 --------
5.75 2.6950 1.2052 0.0183 O.Q142 0.0041 --------
5.83 2. 7133 1.2195 0.0183 0.0143 0.0041 --------
5.92 2. 7317 1. 2338 0.01,83 0.0143 0.0040 --------
6.00 2.7500 1. 2481 0. 0183 0.0143 0.0040 --------
-------------------. -. ------------. -·--------------------------------
Total soil rain loss=
Tqtal effective runoff
1. 50 (In)
1.25(In)
--------------------~ -----------------------------------------
Pea:k flow rate this hydrograph =
Total runoff volume this hydrograph =
1.18 (CFS)
4530.6(Ft3)
++++++++++~+++++++++++++++++++++++++++++++++++++++++++++++++++++++
6 -H O U R S T O R M
R u n o t f H y d r o g r a p h
------------.-----------------------------------------------------
Hrdrograph in 5 Minute intervals ((CFS))
Tirne(h+rn) Volume Ac.Ft
10.0
Q (CFS) 0 2.5 5.0 7.5
O+ 5 0.0000 0.00 Q
0+10 0.0000 0.00 Q
0+15 0.0000 0.00 Q
0+20 0.0000 0.00 Q
0+25 0.0000 0.00 Q
0+30 0.0000 0.00 Q
0+35 0.0000 0.00 Q
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0+40 0.0000 0.0.0 Q
I 0+45 0.0000 0.00 Q
0+50 0.0000 0.00 Q
I 0+55 0.0000 0.00 Q
I 1+ 0 0.0000 0.00 Q
1+ 5 0. 0000 0.00 Q
I 1+10 0.0000 0.00 Q
1+15 o. ooo·o 0.00 Q
I 1+20 0.0000 0.00 Q
1+25 0.0000 0.00 Q
I 1+30 0.0000 0.00 Q
1+35 0.0000 0.00 Q
I 1+40 0.0001 0.01 Q
I 1+45 0.0003 0.03 Q
1+50 0.0006 0.05 Q
I 1+55 0. 0011 0.06 Q
2+ 0 0.0016 0.08 Q
I 2+ 5 0.0042 0.37 IQ
I -2+10 0.0086 0.64 1· QV
I I
2+15 0.0142 0.81 QV I
I 2+20 0. 0208 0.96 Q VI
2+25 0. 02.83 1.08 Q V
I 2+30 0. 03 64 1.18 Q V
2+35 0.0406 0.61 Q V
I 2+40 0.0430 0.35 IQ V
2+45 0.0454 0.35 IQ V I
I 2+50 0.0479 0.36 IQ. VI
I 2+55 0.0504 0.36 IQ VI
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I 3+ 0 0.0529 0.37 IQ V
I 3+ 5 0.0551 0.32 IQ IV
3+10 0.0572 0.30 IQ IV
I 3+15 0.0594 0.31 IQ jv
3+20 0.0Ei;J.5 0.31 l·Q I V
I 3+25 0.0636 0.31 IQ V
3+30 0.0658 0,.32 IQ V
I 3+35 0.0675 0.24 Q V
I 3+40 0.0690 0.21 Q V
3+45 0.0704 0.21 Q V I
I' 3+50 0.0719 0.22 Q V I
3+55 0.0734 0.22 Q VI
I 4+ 0 0.0749 0.22 Q VI
4+ 5 0. 0762 0.19 Q VI
I 4+10 0.0775 0.18 Q vj
4+15 0.0788 0.18 Q V
I 4+20 0.0800 0.18 Q V
I 4+25 0.0813 0.18 Q IV
4+30 0.0826 Q.19 Q IV
I 4+35 0.0838 Q.18 Q IV
4+40 0.0851 0.18 Q IV
I 4+45 0.0863 0.18 Q I V
4+50 0.0875 0.18 Q V ' -I I
4+55 0.0888 0.18 Q V
I 5+ 0 0.0900 0.18 Q V
5+ 5 0. 0911 6.lp Q V
I 5+10 0.0922 0.16 Q V
5+15 0.0933 0.16 Q V
I 5+20 0.0944 0.16 Q V
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5+25 0.0955 0.16 Q V
I 5+30 0.0966 0.16 Q V
5+35 0. 0977 0.17 Q I V
5+40 0.0989 0.17 Q V
5+45 0.1001 0.17 Q V
5+50 0.1013 0.17 Q V
5+55 0.1024 0.17 Q
VI
6+ a 0 .1036' 0.17 Q 1.
VI
6+ 5 0.1040 0.05 Q
V ---------.-------------------------------·----------------------------
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+++
++
UNIT HYDRO GRAPH ANALYSIS
Copyright (c) CIVILCADD/CIVILDESIGN, 19~0 -1999, Version 6.0
Study date 10/25/02 File: 101273.out
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Armstrong Development & Brooks Consulting Engineers -S/N
Unit Hydrograph calculation for new development
1280 Hoover Street, Carlsbad, California
785
Ultimate Developed flows to grassy retention/infiltration basin
100 yr. -6 hr. design storm
+++++++++++++++++++++++++++++++++++++++++.+++++++++++++++++++++++++
Storm Event Year= 100
Antecedent Moisture Condition=~
English (in-lb) Input Units Used
English Rainfall Data (Inches) Input Values Used
Area averaged rainfall isohyetal data:
Sub-Area (Ac . ) Rainfa,11 (In)
0.51 2.75
0.49 2.75
Rainfall Distribution pattern used in study:
Type B for SCS (small dam) or San Diego 6 hour storms
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
*********
Area
(Ac.)
0.31
0.20
0.00
0.49
Area-Averaged SCS Curve Number and Fm*********
Area
fract
0.306
0.204
0.000
0.490
scs CN
(AMC2)
65 .0
98.0
65.Q
65.0
SCS CN
(AMC3)
83.0
98.0
83.0
83.0
Fm
(In/Hr)
0.000
0.000
0.000
Soil
Group
D
D
D
Area-averaged catchment scs Curve Number AMC(3) = 86.060
Area-averaged Fm value using values listed= O.OOO(In/Hr)
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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Using U.S. Army Corps of Engineers formula for lag time
lag= 24 n ( L(Mi) Lc(Mi) /Slope(Ft/Mi) ) A 0.38
Watercourse length = 385. 00·(Ft .. )
2 7 0 . 0 0 ( Ft . )
17. 00 (Ft.)
Length from concentration point to centroid=
Elevation difference along watercourse=
Mannings friction factor along watercourse (n) = o. 015
Watershe9: area = 1. 00 (Ac.)
Catchment Lag time = 0. 015 hours
Unit interval= 5.000 minutes
Unit interval percentage of lag time= 545.9752
Hydrograph baseflow = 6.00(CFS)
.Minimum watershed loss rate (Fm) = O. 040 (In/Hr)
Average adjusted SCS Curve Number= 86.060
Rainfall depth area reduction factors:
Using a total area of 1.00(Ac.) (Ref: SCS Sup A, Sec.4)
Pacif:i.c Coastal Climate ratio used
Areal factor ratio (rainfall reduction) = 1.000
Rainfall entered for study= 2.750(In)
Adjusted rainfali = 2. 75.0 (In)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
The following unit hydrograph was developed usihg an S-Graph
interpolated by time percentage of lag time vs. percentage of peak
flow.
is
The S-Graphs for Valley, Foothill, and Mountain were developed by the
U . .S. Army Corps of Engineers for use in the respective type of
basins located in Southern California. (Hydrology San Gabrial River
U.S. Engineer Office, Dec 1944, revised Jul 1946) The Desert S-Graph
from Report ... on ... Tahquitz Creek, California, same U.S. offfice,
Corps of Engineers, June 1963. The Valley Developed S-Graph is used
by Orange and San Bernardino counties in California to represent the
characteristics of valley a;rea·s with a large amount of development.
Because of the wide variety in topography in Southern California,
these
synthetic unit hydrographs were included for use as options in any
geographic location.
The SCS(Soil Conservation Service Dimensionless S-Graph, scs
handbook,
of 1972, applies to a broad cross section of geographic locations and
hydrologic regions.
The User Defined hydrograph converts the user Q/Qp
vs. T/Tp values into an S-Graph based on lag= Tp/0.9. Then, for the
lag time used, the S-Graph in interpolated in time% of lag.
The following S-Graph or S-Graph combination is used in this study:
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FOOTHILL s-Graph
UNIT HYDROGRAPH
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
Time Ratio
(t/Lag)
5.46
10.92
Time
(hrs)
(K =
0,083
0.167
Discharge
Ratios
(Q/Qp)
12 .10 (CFS))
1.000
0.321
Q
(CFS)
9.157
2.943
Mass Curve
Ratios
(Qa/Q)
0.757
1. 000
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
For each time interval of the 6 or 24 hour storm, the total rainfall
up to that storm time is calculated. Then the Soil Conservation
Service
SCS (report 1972, 1975) area averaged Curve Number (CN) is used to
determine the amount of direct runoff in (In) using the following
equations:
Q
Where:
(P -Ia) .,..2
P -Ia+ S
Q = direct runoff, P = depth of precipitation, Ia= Initial
Abstraction
and Sis the watershed storage in inches.
following equations:
1000
s -------------10 and
CN
Sand Ia are given by the
Ia -0. 2 S
Note: If Metric (SI) Units are used, rainfall data is converted by
the program internally tnto inches for these calculations.
.Note: In the following printout, the revised runoff column is only
used when the minimum soil loss rate, fm, exceeds the normal
loss rate of delta P(dP) -delta Q(dQ) then the dP-dQ column
equals fm = 0.040(In) (for time interval= 0.003(In)) and
the
revised runoff is shown in t-he last column.
Time
Period
Total Total SCS Rainfall Runoff
Rainfall Runoff Amount Amount
Infiltr-Revised
at ion Runoff
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I M:l.n
(hours) (Ih) (In) (In) (In) (In) Loss
I Rate
p Q di? dQ dP-dQ
-----------~------------------------------------------------------
I 0,08 0.0160 0.0000 0.0160 0.0000 0.0160 --------
0.17 0.0321 0.0000 0.0160 0.0000 0.0160 --------
0.25 0.0481 0.0000 0.0160 0.0000 0.0160 --------
I 0.33 0. 0.642 0.0000 0.0160 0.0000 0.0160 --------
0.42 0.0802 0.0000 0. 0160 0.0000 0.0160 --------
0.50 0.0963 0.0000 0.0160 0.0000 0.0160 --------
0.58 0 .1178 0.0000 0. 0215 0.0000 0.0215 --------
I 0.67 0 .1393 0.0000 0. 0215 0.0000 0.0215 --------
0.75 0.1609 0.0000 0. 0215 0.0000 0.0215 --------
0.83 0.1824 0.0000 0. 0215 0.0000 0.0215 --------
I 0.92 0.2040 0.0000 0.0215 0.0000 0.0215 --------
1.00 0.2255 0.0000 0. 0215 0.0000 0.0215 --------
1.08 0.2521 0·.· 0000 0.0266 0.0000 0.0266 --------
1.17 0.2787 0.0000 0. 0266 0.0000 0.0266 --------
I 1.25 0.3053 0.0000 0.0266 0.0000 0.0266 --------
1.33 0.3318 0.0000 0. 02.66 0.0000 0.0265 --------
1.42 0.3584 0.0007 0.0266-0.0007 0.0259 --------
1.50 0.3850 0.0022 0.0266 0.0015 0.0251 --------
I 1. 58 0.4263 0.0061 0.0413 0.0039 0.0374 --------
1. 67 0 .46.75 O.Q117 0. 0412 0.0056 0.0356 --------
1.75 0.5088 0.0189 0. 0413 0.0072 0.0340 --------
I 1.83 0.5500 0.0277 0. 0413 0.0088 0.0325 --------
1.92 0.5913 0.0379 0.0413 0.0102 0. 0311 --------
2.00 0. 6325 0.0494 0. 0413 0.0115 0.0297 --------
2.08 0.8021 0.1090 0.1696 0.0596 0 .1100 --------
I 2.17 0. 9717 0.1850 0 .1696 0.0760 0.0935 --------
2.25 1.1413 0 .2741 0.1696 0.0891 0.0805 --------
2.33 1. 3108 0.3736 0.1696 0.0995 0.0700 --------
I 2.42 1. 4804 0.4817 0.1696 0.1081 0.0615 --------
2.50 1. 6500 0.5969 0 .1696 0.1152 0.0544 --------
2.58 1. 6958 0.6291 0.0458 0.032.2 0.0136 --------
2.67 1. 7417 0.6617 0. 0458 0.0326 0.0132 --------
I 2.75 1. 7875 0.6947 0.0458 0.0330 0.0128 --------
2.83 1. 8333 0. 7281 0. 04.58 0.0334 0.0125 --------
2.92 1.8792 0.7618 0.0458 0.0337 0.0121 --------
I ·3,00 1. 92.50 0.7~59 0. 04~8 0.0341 0.0118 --------
. 3. 08 1.9621 0 .8237 0.0371 0,0278 0.0093 --------
3.17 1. 9993 0.8518 0. 0371 0.0281 0.0091 --------
3.25 2. 0364 0.8800 0. 0371 0.0283 0.0089 --------
I 3.33 2.0735 0.9085 0.0371 0.0284 0.0087 --------
3.42 2 .1106 0.9371 0.0371 0.0286 0.0085 --------
3.50 2 .1.478 0 .96.59 0. 0371 0.0288 0.0083 --------
I 3.58 2. 1725 0.9852 0. 0248 0.0193 0.0054 --------
3.67 2.1972 1.0046 0.0247 0.0194 0.0054 --------
3.75 2.2220 1.0241 0.0248 0.0195 0.0053 --------
3.83 2.2468 1.0436 0: 0248 0. 0.195 0.0052 --------
I 3.92 2. 2715 1. 0632 0. 0248 0.0196 0.0051 --------
4.00 2.2962 1. 0829 0.0247 0.0197 0.0051 --------
4.08 2. 3.169 1. 0994 0. 0206 0.0165 0.0042 --------
I 4.17 2.3~75 1.1159 0. 0206 0.0165 0.0041 --------
4.25 2.3581 1.1324 0. 0206 0.0165 0.0041 --------
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++
4.33 2.3788 1.1490 . 0.0206 0.0166 0.0040 --------
4.42 2.3994 1.1657 0.0206 0.Q166 0.0040 --------
4.50 2.4200 1.1823 0.0206 0.0167 0.0039 --------
4.58 2.4397 1.1983 0.0197 0.0160 0.0037 --------
4.67 2.4594 1. 2143 0.0197 0.0160 0.0037 --------
4.75 2.4791 1.2304 0.0197 0.0161 0.0036 --------
4.83 2.4988 1.2465 0.0197 0.0161 0.0036 --------
4.92 2.5185 i'.2626 0.0197 0.0161 0.0036 --------
5.00 2.5383 1. 2788 0.0197 0.0162 0.0035 --------
5.08 2.5552 ;I..2928 0.0170 --------0.0033 0.0136
5.17 2.5722 1.3067 0.0170 --------0.0033 0.0136
5.25 2.5891 1. 3207 0.0170 --------0.0033 0.0136
5.33 2.6061 1. 3347 0.0170 --------0.0033 0.0136
5.42 2.6230 1. 3488 0.0170 --------0.0033 0.0136
5.50 2.6400 1. 3629 0.0170 --------0.0033 0.0136
5.58 2.6583 1.3781 o. 01a3· --------0.0033 0.0150
5.67 2.6767 1. 3934 0.0183 --------0.0033 0.0150
5.75 2.6950 1.4087 0. 01B3 --------0.0033 0.0150
5.83 2. 7133 1.4240 0.0183 --------0.0033 0.0150
5.92 2.7317 1.4394 0.0183 --------0.0033 0.0150
6.00 2.7500 1 .. 4547 0.0183 --------0.0033 0.0150
---------------------------. ---------------------------------------
------·-------------------------------------------------------------
Total soil rain lof;ls =
Total effective runoff=
1. 30 (In)
1. 45 (In)
Peak flow rate this hydrograph =
Total runoff volume this hydrograph =
1. 37 (CFS)
5266.3(Ft3)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
6 -H O U R S T O R M
Runoff Hydrograph
-----------------------------------------------------------------
Hydrograph in 5 Minute intervals ((CFS))
---------------------------. -
Time(h+m) Volume Ac.Ft
10.0
Q (CFS) b 2.5 5.0 7.5
-------------------------------------------------------------------
0+ 5 0.0000 0.00 Q
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0+10 0.0600 0.00 Q
0+15 0.0000 0.00 Q
0+20 9.0000 0.00 Q
0+25 0.0000 0.00 Q
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I 0+30 0.0000 0.00 Q
I 0+35 0.0000 o.oo Q
0+40 0.0000 0.00 Q
I
,-
0+45 0.0000 0.00 Q
0+50 0.0000 0.00 Q
I 0+55 0.0000 0.00 Q
1+ 0 0.0000 0.00 Q
I 1+ 5 0.0000 0.00 Q
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I 1+10 0.0000 0.00 Q
1+15 0.0000 0.00 Q
I 1+20 0.0000 0.00 Q
1+25 0.0000 0.01 Q
I 1+30 o.M02 0.02 Q.
1+35 0.0004 0.04 Q
I 1+40 0.0009· 0.06 Q
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I 1+45 0.0014 0.08 Q
1+50 0.0021 0.10 Q
I 1+55 0.0029 0.12 Q
2+ 0 0.0039 0.14 QV
I 2+ 5 0.0079 0.58 Q
2+10 0.0139 0.87 QV
I 2+15 0.0210 1.04 Q V
'-2+20 0. 0291 1.17 Q VI
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2+25 0.0380 1.28 Q I V
I 2+30 0.0474 1.37 Q· V
2+35 0 .. 0518 0.63 Q V I
I 2'+40 0.0545 0.39 10 VI
2+45 0.0572 0.40 lo VI
I 2+50 0.0600 0.40 10 VI
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2+55 0. 0628 0.41 jQ V
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3+ 0 0.0656 0.41 jQ jv
3+ 5 0.0681 0.3"6 jQ jv
I 3+10 0. 0704 0.34 jQ V
I 3+15 0. 0728 0.34 jQ V
3+20 0.0751 0.34 jQ V
I 3+25 0.0775 0.35 jQ -v
3+30 0. 0799 0.35 jQ V
I 3+35 0.0817 0.26 jQ V
3+40 0. 0833 o.:p Q I V
I 3+45 0.0849 0.24 Q V I
I 3+50 Q.0866 0.24 Q V I
3+55 0.08$2 0.24 Q VI
I 4+ 0, 0,0898 0 .,24 Q vi
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4+ 5 0. 0913 0.21 Q V
I 4+10 0.0927 6.20 Q V .,
4+i5 0. 0940 0.20 Q IV
·1 I
4+20 0. 0954 0.20 Q I jv
4+25 0.0968 0.20 Q V
I 4+30 0. 0982 0.20 Q ,, jv
I 4+35 0.0995 0.20 Q -I I V
4+40 0 .1009 0.19 Q V
I 4+45 0.1022 0.19 Q V
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4+50 0; 10'35 0.19 Q V
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4+55 0.1049 0.20 Q V
5+ 0 0 .1062 0·.20 Q V
I I 5+ 5 0.1074 0.17 Q V
I 5+10 0 .1086 0.17 Q V
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5+15 0.1097 0.17 Q V
5+20 0 .1108 0.17 Q V
5+"25 0 .1120 0.17 Q V
5+30 0 .1131 0 .. 17 Q V
5+35 0.1143 0,18 Q V
5+40 0 .1156 0.18 Q V
5+45 0 .1168 0.18 Q V
5+50 0 .1181 0.18 Q
VI
!?+55 0 .1193 0.18 Q
VI
6+ 0 0.1206 0.18 Q
VI
6+ 5 0.1209 0.04 Q
VI -----------------------------------------------------------------------
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APPENDIX "A"
Armstrong & Brooks Consulting Engineers
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6.2
++++
San· Diego County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software, (c)1991-2000 Version
Rational method hydrology program based on
San Diego County Flood Control Division 1985 hydrology manual
Rational Hydrology Study Date: 10/25/02 -. -----, --------------------_,_ --' ----------------------------------
10 --YEAR 11 0N-SITE" HYDROLOGY STUDY
HOOVER STREET
********* Hydrology Study Control Information**********
Armstrong Development & Brooks Consulting Engineers -S/N 785
------------------------------------------------------------------
Rational hydrology study storm event year is
English (in-lb) input data Units used
English (in) rainfall data used
Map data precipitation entered:
6 hour, precipitation(inches) = 1.800
24 hour precipitation(inches) = 3.000
Adjusted 6 hour precipitation (inches) = 1.800
P6/P24 = 60.0%
San Diego hydrology manual 'C' values used
Runoff coefficients by ratiqnal method
10.0
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process ~rom Point/Station
10.000
5.000 to Point/Station
**** 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 = L 000
[SINGLE FAMILY area type ]
Initial subarea flow distance = 221. 000 (Ft.)
Highest elevation= 135.500(Ft.)
Lowest elevatio~ = 125.SOO(~t.)
Elevation difference= 9.700(Ft.)
Time of concentration calculated by the urban
areas overland flow method (App X-C) = 8.99 min.
TC= [1.8*(1.1-C)*distance(Ft.)"".5)./(% slope""(l/3)]
TC= [1.8*(1,1-0.5500)*( 221.000"".5)/( 4.389""(1/3)]= 8.99
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Rainfall intensity (I) = 3. 249 (In/Hr) for a 10.0 year
storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.550
Subarea runoff= 0.447(CFS)
Total initiai stream area= 0.250(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++
Process from Point/Station
15.000
io.ooo to Point/Station
**** PIPEFLOW TRAVEL TIME (User specified size) ****
Upstream poiht/station elevation= 125.B00(Ft.)
Downstream point/station elevation= 120.200(Ft.)
Pipe length = 58. 20 (Ft.) Manning's N = o. 013
No. of pipes= 1 Required pipe flow = 0.447(CFS)
Given pipe size = 4. 00 (In.)
Calculated individual pip~ flow = 0.447(CFS)
Normal flow depth in pipe= 2.60(In.)
Flow top w.idth inside pipe = 3. 82 (In.}
Critical depth could not be calculated.
Pipe flow velocity = 7. 44 (Ft/ s)
Travel time through pipe= 0.13 min.
Time of concentration (TC) = 9.12 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++
15.000
Process from Point/Station 20.b00 to Point/Station
**** SUBAREA FLOW ADDITION****
Decimal fraction soil group
Decimal fraction soil group
Decimal fraction soil group
Decimal fraction soil group
[SINGLE FAMILY area type
A
B
C
D
=
=
=
=
0.000
0.000
0.000
1.000
Time of concentration= 9.12 min.
Rainfall intensity= 3.219(In/Hr) for a 10.0 year storm
Runoff coefficient used for sub-area, Rational method,Q=KCIA, C =
0.550
Subarea runoff=
Total runoff=
0.425(CFS) for 0.240(Ac.)
0.872(CFS) Total area=
End of computations, total study area=
0 .49 (Ac.)
0. 490 (Ac.)
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APPENDIX "B"
Armstrong & Brooks Consulting Engineers
----
5' -$-
") ~
(::tl;)
SAN DIEGO COUNTY ASSESSOR'S MAP BK 206 PG 15
-----------·----
206-15
f
I· ii-ii ... j ...j,..l~l.if oJ. f .;J .I I I I I I , -==;'= ,o~' I t
~
9 6)<lS1 S-1
Pr{/\,~\6 &lS~i,,,,G.>--if
E\i.\S'i· Corl(,. (.,,11'1;;:;'t)
(Jf''!;,M j/1,-IA.l·J<;\)1,,,~( ':,\~t,.f-GO
J ~ t,,,1\fa~ !: \ 1 bGSf
THIS IMP WAS ?11;PAREO fat ASSES&.Em PUlroSES OIU. IO l0.8llTY IS ASSI.I.EO Fat THE ACCUlACY OF TH: DITA SH:N.'H ASSESOOA'S Po\RCELS IMY IOI <lM'I.Y WITH LOCAL SUIO<VISOII 00 !lJILOOG OlllMNCES
CATc.\-,\
~ nr NO ACCESS
"--,.~
~
-$-MAP 2152-BELLAVISTA
ROS 12:918
<
f'V::S· \B-1)lU-f St)
W4