HomeMy WebLinkAboutMS 01-15; THOMPSON SUBDIVISION; HYDROLOGY AND HYDRAULIC CALCULATIONS FOR THOMPSON SUBDIVISION GRADING PLAN; 2003-06-04HYDROLOGY AND HYDRAULIC
CALCULATIONS
FOR
THOPvIPS ON SUBDIVISION
GRADING PLAN
MS 01-15
CDP01-43
HDPO2-12
PREPARED BY:
Aquaterra Engineering Inc.
1843 Campesino Place
Oceanside, CA 92054
(760) 49-2802
p 'w'-jqyv NO. C57860
istin lip'ska Borer, PE Exp
C 57860 Exp. 6/30/06 CNI
OF C
JUNE 49 2003
INTRODUCTION
The City of Carlsbad has requested a Hydrology Analysis be completed to estiblish the 100 year ,
owfir.the newly established lot and residënce.
Drainage Reference Material
The following criteria and design manuals will be used for this drainage analysis:
- San Diego County Hydrology Manual, August 2001
- San Diego County Hydrology Manual, 1997
Drainage Design Criteria
Design Storm:... 100 year---
H ydrology Calculations (100 year storm)
The Coefficient of Runoff for residential areas is determined by the density or dwelling units per
acre. The density of the developed condition of this property is 2.82 du/ac. Therefore from Table
3-1 of the Hydrology Manual, the Land Use Designator for the Existing Condition is Low,
Residential, 2.9 DU/A or less, for Soil Type C,
C=.45
Total Site Area: A=15400143560 = 0.35 ac.
To Determine, I or the Intensity, we use (from FIG 3-1 & 3-5, attached)
Q10 = C x 1100 x A
Where Q100 = 100 year runoff (cfs)
C = 0.45eYF1*c7
I = 3.7in1hr.
A =.35 ac.
Q1 =.45X3.7X.35 49 :
-7. .
)Ci$T/& & 54 Co '0
£/Q
Table 3-1
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use Runoff Coefficient "C"
Soil Type
NRCS Elements County Elements % IMPER. A B C D
Undisturbed Natural Terrain
LOW
Low
Low
Medium Density Residential
Medium Density Residential
Medium Density Residential
Medium Density Residential
I ugh Density Residential
High Density Residential
Commercial/Industrial
Commercial/Industrial
Commercial/Industrial
Commercial/Industrial
Permanent Open Space
Residential, 1.0 DU/A or less
Residential, 2.0 IMJ/A or less
Residential, 2.9 DU/A or less
Residential, 4.3 DU/A or less
Residential, 7.3 DU/A or less
Residential, 10.9 DU/A or less
Residential, 14.5 DU/A or less
Residential, 24.0 DU/A or less
Residential, 43.0 DUIA or less
Neighborhood Commercial
General Commercial
Office Professional/Commercial
Limited Industrial
0$ 0.20 0.25 0.30 0.35
10 0.27 0.32 036 0.41
20 0.34 0.38 0.42 0.46
25 0.38 0.41 6.45 0.49
30 0.41 0.45 0.48 0.52
40 0.48 0.51 0.54 0.57
45 0.52 0.54 0.57 0.60
50 0.55 0.58 0.60 0.63
65 0.66 0.67 0.69 0.71
80 0.76 0.77 0.78 0.79
80 0.76 0.77 0.78 0.79
85 0.80 0.80 0.81 0.82
90 0.83 0.84 0.84 0?85
90 0.83 0.84 0.84 0.85
Tlic values associated with 0% Impervious may be used for direct calculation of the runoff coefficient as described In Section 3.1.2 (representing (he pervious
runoff coefficient, ('p, for the soil typc), or for areas that will remain undisturbed in perpetuity. iuMificafloji must be given that (lie 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
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