HomeMy WebLinkAboutCT 97-24; May Subdivision; May Subdivision; 1998-11-05DRAINAGE CALCS
MAY SUBDIVISION
PREPAREDmr/ / /
mJames A. Laret, R.C E 2937
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DATE:
Novembers, 1998
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RUNOFF COEFFICIENTS (RATIONAL METHOD)
LAND USE Coefficient. C
Soil Group (1)
A B_ C D
Undeveloped .30 .35 .40 .45
Residential:
Rural .50 .33 .40 .45
Single Family .40 .45 L50J .55
Multi-Units .45 .50 .60 .'C
Mobile Homes (2) .45 .50 .55 .65
Commercial (2) .70 .75 .80 .35
80% Impervious
Industrial (2) .80 .85 .90 .95
90% Imoervious
NOTES:
(1) Obtain soil group from maps on file with the Department of Sanitation
and Flood Control.
(2) Where actual.conditions deviate significantly from the tabulated
imperviousness values of 80% or 90%, the values given for coefficient
C, may be revised by multiplying 80% or 90% by the ratio of actual
imperviousness to the tabulated imperviousness. However, in no case
shall the final coefficient be less than 0.50. For example: Consider
commercial property on D soil group.
Actual imperviousness = 50%
Tabulated imperviousness = 80%
Revised C=J°X0.85=0.5380
APPENDIX !X
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SAN DIEGO COUNTY
DEPARTMENT OF SPECIAL DISTRICT SERVICES
DESIGN MANUAL
NOMOGRAPH FOR DETERMINATfON
OF TIME OF CONCENTRATION (Tc)
FOR NATURAL WATERSHEDS
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DISCHARGE (C.FS.)
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EXAMPLE:
Given: C= 10 S = 2.5%
Chart gives; Depth = 0.4, Velocity = 4.4 f.p.s.
SAN DIEGO COUNTY
DEPARTMENT OF SPECIAL DISTRICT SERVICES
DESIGN MANUAL/,/ «..,->
GUTTER AND ROADWAY
DISCHARGE-VELOCITY CHART
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CAPACITY OF.'GRATE INLET IN SUMP
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DEPTH OF • FLOW ".y-FEET .
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9-11