WMS:OC Rational Equation

Flows for the Orange County rational method are calculated from the following equation:

$Q=0.90(I-F_{m})A$

where:

• $Q$ – peak flow $(ft^{3}/s\ or\ m^{3}/s)$
• $I$ – rainfall intensity (in/hr, mm/hr)
• $F_{m}$ – maximum loss rate, where F_m = a_p * F_p
• $A$ – catchment area (acres)

This equation is very similar to the traditional Rational Method equation. The term I - F_m is often referred to as the effective precipitation.

Related Topics

• Losses