The Rational Method formula for estimating peak runoff is Q = CiA, where i represents:
Choose the correct answer
Hydraulic gradient of the stream
Rainfall intensity for the time of concentration (Tc) of the catchment
Infiltration rate
Irrigation water requirement
Correct Answer
B. Rainfall intensity for the time of concentration (Tc) of the catchment
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Rational Method: Q (m³/s or ft³/s) = C·i·A where C = runoff coefficient (0 to 1, depends on land use), i = rainfall intensity (mm/h or in/h) for the time of concentration (Tc), A = catchment area (ha or acres). Used for small urban catchments (< 50 ha). i is intensity for the critical storm duration = Tc.
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