Rational method runoff coefficients are tabulated below. Note that Stormwater Studio allows you to compute composite coefficients with up to three pairs of drainage area and coefficients for each Inlet.
Description of Area | Coefficient | Typical Design |
---|---|---|
BUSINESS | ||
Downtown | 0.70 – 0.95 | |
Neighborhood | 0.50 – 0.70 | |
RESIDENTIAL | ||
Single family | 0.35 – 0.45 | |
Multi-units detached | 0.40 – 0.75 | |
Suburban | 0.25 – 0.40 | |
Apartments | 0.50 – 0.70 | |
INDUSTRIAL | ||
Light | 0.50 – 0.80 | |
Heavy | 0.60 – 0.90 | |
Parks, Cemeteries | 0.10 – 0.25 | |
Playgrounds | 0.20 – 0.35 | |
Railroad yards | 0.20 – 0.40 | |
Lawns, sandy soil | 0.05 – 0.20 | |
Lawns, heavy soil | 0.18 – 0.35 | 0.30 |
Unimproved | 0.10 – 0.30 | 0.30 |
Asphalt | 0.70 – 0.95 | 0.90 |
Concrete | 0.80 – 0.95 | 0.90 |
Roofs | 0.75 – 0.95 | 0.90 |