Kostenloser Runoff Coefficient Rechner
Berechnen Sie peak stormwater runoff unter Verwendung von the Rational Method Q = CiA/360. Geben Sie C, intensity, and catchment area.
Peak Runoff Rate
0.833 m^3/s
Peak Runoff Rate vs Runoff Coefficient (C)
Formel
## Rational Method for Stormwater Runoff The Rational Method is the most widely used formula for estimating peak runoff from small catchments. ### Formula **Q = C i A / 360** where Q is peak flow in m^3/s, C is the runoff coefficient (0 to 1), i is rainfall intensity in mm/h, and A is catchment area in hectares. The factor 360 converts units. This method assumes the entire catchment contributes to runoff when storm duration equals the time of concentration.
Lösungsbeispiel
5 hectare urban catchment, C=0.6, 100 mm/h intensity.
- 01Q = 0.6 x 100 x 5 / 360 = 300/360 = 0.833 m^3/s
- 02Q = 833 L/s
Häufig Gestellte Fragen
What are typical runoff coefficients?
Roofs and pavement: 0.85-0.95. Urban residential: 0.40-0.70. Suburban: 0.25-0.40. Parks and lawns: 0.10-0.25. Forest/undeveloped: 0.05-0.20. Higher density development means higher C values.
When is the Rational Method appropriate?
The Rational Method is suitable for catchments up to about 80 hectares (200 acres). For larger areas, use hydrograph methods (SCS/NRCS Curve Number or unit hydrograph) that account for timing and storage effects.
How do I find a composite C for a mixed catchment?
Calculate the weighted average: C_composite = sum(Ci x Ai) / A_total, where Ci and Ai are the coefficient and area of each land use type.
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