HomeMy WebLinkAboutPA2022-0314_20221221_Hydrology Report 11-21-2022TABLE OF CONTENTS
1.0 ) HYDROLOGY CALCULATIONS
1.1 TOTAL AREA
1.2 AREA OF WORK
1.3 SOIL TYPE
1.4 TIME OF CONCENTRATION
1.5 RAINFALL INTENSITY
1.6 RUNOFF COEFFICIENT
1.7 PEAK DISCHARGE CALCULATIONS ‐ EXISTING & PROPOSED CONDITIONS
2.0) HYDRAULIC CALCULATIONS
2.1 MANNING’S EQUATION FOR HYDRAULICS
2.2 CALCULATIONS FOR FLOW CAPACITY
3.0) ATTACHMENTS/REFERENCES
VICINITY MAP
ORANGE COUNTY – HYDROLOGY MANUAL – FIGURE D‐1
ORANGE COUNTY – HYDROLOGY MANUAL – FIGURE B‐3
ORANGE COUNTY – HYDROLOGIC SOIL GROUPS – FIGURE XVI‐2a
RUNOFF COEFFICIENT TABLE – (C VALUES) ‐ NRCS
USDA WEB SOIL SURVEY (SOIL TYPE)
MANNING’S “n” VALUES TABLE – CHOW 1959
RUNOFF COEFFICIENT EXCERPT TAKEN FROM OC HYDROLOGY MANUAL
4.0) HYDROLOGY MAPS
HYDROLOGY MAP EXISTING CONDITIONS
HYDROLOGY MAP PROPOSED CONDITIONS
1.) HYDROLOGY CALCULATIONS
1.1 TOTAL AREA:
Lot Area = 5,596 SF or 0.13 AC
Hydrological Area = 4,877 SF or 0.11 AC
1.2 AREA OF WORK:
Existing Conditions:
Drainage Management Area #1
Total SQ. FT. = 4,877 SF
Total Acres = 0.11 AC
Proposed Conditions:
Drainage Management Area #1
Total SQ. FT. = 2,385 SF
Total Acres = 0.055 AC
1.3 SOIL TYPE
Hydraulic Soil Type D
Taken from NRCS Hydrology national engineering Handbook
Chapter 7 – Hydrologic Soil Groups.
See Attachments
Soil Group D: Soils in this group have high runoff potential when thoroughly wet. Water
movement through the soil is restricted or very restricted. Group D soils typically have
greater than 40 percent clay, less than 50 percent sand, and have clayey textures. In
some areas, they also have high shrink‐swell potential. All soils with a depth to a water
impermeable layer less than 50 centimeters [20 inches] and all soils with a water table
within 60 centimeters [24 inches] of the surface are in this group, although some may
have a dual classification, as described in the next section, if they can be adequately
drained.
TIME OF CONCENTRATION (Tc)
Existing Conditions:
DMA‐1:
Length (L) of initial area = 86.6 FT
Inlet Elevation = 12.20 FT
Outlet Elevation = 11.60 FT
Difference in Elevation for Initial Area = 0.60 FT
Hydrologic Area = 4,877 SF/0.11 AC
Pervious Areas = 4,877 SF/0.11 AC
Percentage of pervious Cover (Pi) = 100%
Time of Concentration (Tc) (min.) = 7.00 MIN.
Tc calculated from the Orange county Hydrology Manual Figure D‐1 (see attachments)
Proposed Conditions:
DMA‐1:
Length (L) of initial area = 64.2 FT
Inlet Elevation = 12.55 FT
Outlet Elevation = 11.60FT
Difference in Elevation for Initial Area = 0.95 FT
Hydrologic Area = 4,877 SF/0.11 AC
Impervious Areas = 2,385 SF/0.055 AC
Percentage of Impervious Cover (Pi) = 48.9%
Time of Concentration (Tc) (min.) = 6.40 MIN.
Tc calculated from the Orange county Hydrology Manual Figure D‐1 (see attachments)
RAINFALL INTENSITY
I (t) = (a)(tb)
I = Intensity (in/hr)
a25 = 11.995, a100 = 15.560
b25 = ‐0.566, b100 = ‐0.573
t1 = Tc
EXISTING CONDITIONS:
DMA#1
Return Period 25 Years (24hr)
Iሺtሻ ൌatୠ Iሺtሻ ൌ ሺ11.995ሻሺ7.00ሻ
ି.ହ
Iሺtଵሻ ൌ3.99 Intensity (in/hr)
Return Period 100 Years (24hr)
Iሺtሻ ൌatୠ Iሺtሻ ൌ ሺ15.560ሻሺ7.00ሻ
ି.ହଷ
𝐼ሺ𝑡ଵሻ ൌ5.10 Intensity (in/hr)
PROPOSED CONDITIONS:
DMA#1
Return Period 25 Years (24hr)
Iሺtሻ ൌatୠ Iሺtሻ ൌ ሺ11.995ሻሺ6.40ሻ
ି.ହ
Iሺtଵሻ ൌ4.19 Intensity (in/hr)
Return Period 100 Years (24hr)
Iሺtሻ ൌatୠ Iሺtሻ ൌ ሺ15.560ሻሺ6.40ሻ
ି.ହଷ
𝐼ሺ𝑡ଵሻ ൌ5.37 Intensity (in/hr)
Values and equations taken from the Orange County Hydrology Manual
(Figure B‐3) see attached.
1.4 RUNOFF COEFFICIENT
(ORANGE COUNTY HYDROLOGY MANUAL)
Cൌቐ0.90ቆA୍ ሺIെFሻA
I ቇ,𝑓𝑜𝑟 𝐼 𝑔𝑟𝑒𝑎𝑡𝑒𝑟 𝑡ℎ𝑎𝑛 𝐹;
0.90𝐴ூ,𝑓𝑜𝑟 𝐼 𝑙𝑒𝑠𝑠 𝑡ℎ𝑎𝑛 𝑜𝑟 𝑒𝑞𝑢𝑎𝑙 𝑡𝑜 𝐹
C = runoff coefficient
I = rainfall intensity (inches/hour)
Fp = infiltration rate for pervious areas (inches/hour)
AI = ratio of impervious area to total area (decimal fraction)
Ap = ratio of pervious area to total area (decimal fraction)
Existing Conditions:
I = 5.10 in/hr
FP = 0.20 in/hr
AI = 0
AP = 1.00
𝐶ൌ0.90ቀ0ሺହ.ଵି.ଶሻଵ.
.ଵଽ ቁ
C = 0.71
Proposed Conditions:
DMA‐1
I = 5.37 in/hr
FP = 0.20 in/hr
AI = 0.489
AP = 0.511
𝐶ൌ0.90ቀ0.489
ሺହ.ଷି.ଶሻ.ହଵଵ
.ଵଽ ቁ
C = 0.82
1.5 PEAK DISCHARGE CALCULATIONS
Q=C(I)(A)
Q = Flow (cfs)
C = Run‐Off Coefficient
I = Intensity Rating (in/hr)
A = Area (Acres)
Existing Hydrologic Variables
DMA #1
C = 0.71
I25 = 3.99 in/hr
I100 = 5.10 in/hr
A = 0.11 acres
*C values may change by use of tables.
Existing Conditions:
Q25 = 0.31 CFS or 139.14 GPM
Q100 = 0.40 CFS 179.53 GPM
Proposed Hydrologic Variables
DMA #1
C = 0.82
I25 = 4.19 in/hr
I100 = 5.37 in/hr
A = 0.055 acres
Proposed Conditions:
DMA #1
Q25 = 0.19 CFS or 85.28 GPM
Q100 = 0.24 CFS or 107.72 GPM
2.1 MANNING’S EQUATION FOR HYDRAULICS
Qൌ1.49
n ሺAሻሺR୦
ଶଷሻሺSୣ
ଵଶሻ
Q ൌ flow rate ሾcfsሿ
A ൌ cross-sectional area of flow ሾft2ሿ
Rh ൌ hydraulic radius ሺcross-sectional area divided by wetted perimeterሻ ሾftሿ
Se ൌ slope of drainage pipe
n ൌ surface roughness ሺbased on drainage pipe material and conditionሻ –
Appendix x,y
y ൌ vertical height of liquid inside drainage pipe ሾftሿ
D ൌ diameter of drainage pipe ሾftሿ
ϴ ൌ angle from center of drainage pipe to edges where water is fiowing ሾradiansሿ
ft ൌ U.S. foot
DMA ൌ drainage management area
PVC ൌ polyvinyl chloride drainage pipe
RCP ൌ reinforced concrete pipe
CFS ൌ cubic feet per second
2.2 CALCULATIONS FOR FLOW CAPACITY
PIPE DEPTH CALCULATOR
n= 0.009 Slope = 0.01
D= 0.5 6" PVC
Y(ft) Y/D D=0.25 θ (rads) Wet Area(A) Hyd. Rad. (Rh) Q (cfs)
0.10 0.200 0.927 0.028 0.060 0.071
0.15 0.300 1.159 0.050 0.085 0.159
0.20 0.400 1.369 0.073 0.107 0.274
0.25 0.500 1.571 0.098 0.125 0.406
0.30 0.600 1.772 0.123 0.139 0.546
0.35 0.700 1.982 0.147 0.148 0.680
0.40 0.800 2.214 0.168 0.152 0.794
0.45 0.900 2.498 0.186 0.149 0.866
0.50 1.000 3.142 0.196 0.125 0.813
DMA-1, 100-year Design Storm Event runoff will be 0.24 CFS.
6” PVC pipe @1% slope can handle 0.866 CFS.
Therefore, DMA-1 satisfy to use 6” PVC pipe @1% slope.
Qൌ1.49
n ሺAሻሺR୦
ଶଷሻሺSୣ
ଵଶሻ
944 Via Lido Nord, Newport Beach, California, 92663.
Latitude: 33°36'33.53"N Longitude: 117°54'34.60"W
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SUBJECT TO FURTHER REVISION
Source: Soils: Natural Resources Conservation Service (NRCS)Soil Survey - soil_ca678, Orange County & Western RiversideDate of publication: 2006-02-08
!I
03.67.21.8
Miles
05102.5
Kilometers
LEGEND
City Boundaries
Hydrologic Soil Groups
A Soils
B Soils
C Soils
D Soils
http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm
Generated by a Trial Version of NetCentric Technologies’ CommonLook® Acrobat® Plug-in. www.net-centric.com
TABLE 1 Values of Runoff Coefficient C
URBAN AREAS:
Type of drainage area Runoff coefficient C
Lawns:
Sandy soil, flat 2%
Sandy soil, average, 2 - 7%
Sandy soil, steep, 7%
Heavy soil, flat, 2%
Heavy soil, average, 2 - 7%
Heavy soil, steep, 7%
0.05 - 0.10
0.10 - 0.15
0.15 - 0.20
0.13-0.17
0.18 - 0.22
0.25 - 0.35
Business:
Downtown areas Neighborhood areas
0.70 - 0.95
0.50.0.70
Residential:
Single-family areas
Multi units, detached Multi units,
attached Suburban
Apartment dwelling areas
0.30 - 0.50
0.40 - 0.60
0.60 - 0.75
0.25 - 0.40
0.50 - 0.70
Industrial:
Light areas
Heavy areas
0.50 - 0.80
0.60 - 0.90
Parks, cemeteries 0.10 - 0.25
Playgrounds 0.20 - 0.35
Railroad yard areas 0.20 - 0.40
Unimproved areas 0.10 - 0.30
Streets:
Asphaltic
Concrete
Brick
0.70 - 0.95
0.80 - 0.95
0.70 - 0.85
Drives and walks
Roofs 0.75 - 0.85
0.75 - 0.95
AGRICULTURAL AREAS:
Topography
and
Vegetation
Runoff Coefficient C Soil Texture
Soil Texture
Open Sandy Loam Clay and Silt Loam Tight Clay
Woodland
Flat 0 - 5% Slope
Rolling 5 - 10% Slope
Hilly 10 - 30% Slope
0.10
0.25
0.30
0.30
0.35
0.50
0.40
0.50
0.60
Pasture
Flat
Rolling
Hilly
0.10
0.16
0.22
0.30
0.36
0.42
0.40
0.55
0.60
Cultivated
Flat
Rolling
Hilly
0.30
0.40
0.52
0.50
0.60
0.72
0.60
0.70
0.82
Orange County and Part of Riverside County,
California
115—Beaches
Map Unit Setting
National map unit symbol: hclq
Elevation: 0 to 10 feet
Mean annual precipitation: 42 to 48 inches
Mean annual air temperature: 52 to 57 degrees F
Frost-free period: 190 to 210 days
Farmland classification: Not prime farmland
Map Unit Composition
Beaches: 100 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Beaches
Setting
Landform: Beaches
Typical profile
H1 - 0 to 6 inches: sand
H2 - 6 to 60 inches: coarse sand, sand, fine sand
H2 - 6 to 60 inches:
H2 - 6 to 60 inches:
Properties and qualities
Slope: 0 to 5 percent
Natural drainage class: Poorly drained
Capacity of the most limiting layer to transmit water (Ksat): High to
very high (5.95 to 19.98 in/hr)
Depth to water table: About 0 to 72 inches
Frequency of flooding: Frequent
Salinity, maximum in profile: Slightly saline to strongly saline (4.0 to
16.0 mmhos/cm)
Available water storage in profile: Moderate (about 6.7 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 8w
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Orange County and Part of Riverside County, California
Survey Area Data: Version 12, Sep 12, 2018
Map Unit Description: Beaches---Orange County and Part of Riverside County, California 944 Via Lido Nord, Newport Beach
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/6/2019
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