Type of Surface | Runoff Coefficient "C" |
Type of Surface | Runoff Coefficient "C" |
Asphalt | 0.85 |
Concrete | 0.90 |
Roof | 0.90 |
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) | 0.15 |
Rolling (2-7% Slope) | 0.20 |
Steep (greater than 7%) | 0.30 |
(1) From HERPICC Stormwater Drainage Manual - Revised July 1994.