TABLE 1: URBAN RUNOFF COEFFICIENTS *

Type of Surface	Runoff Coefficient C
Asphalt	0.82
Concrete	0.85
Roof	0.85
Lawns (Sandy)
Flat (0-2% slope)	0.07
Rolling (2-7% slope)	0.12
Steep (greater than 7%)	0.17
Lawns (Clay)
Flat (0-2% slope)	0.16
Rolling (2-7% slope)	0.21
Steep (greater than 7%)	0.30

 

   The coefficients of this tabulation are applicable to storms of 5- to 10-year frequencies. Coefficients for less frequent, higher-intensity storms shall be modified as follows:

 

Return Period (years)	Multiply C by:
25	1.1
50	1.2
100	1.25

 

(Ord. 1995-10 Tab. 1, passed 10-13-1995)

* From Ordinance 81-16, Tippecanoe County, Indiana, A General Ordinance Establishing Storm Drainage and Sediment Control, November 1981.