Rational Method Formula

Rational Method is covered in Chapter 14 (MSMA, 2000).


The Manual relates the peak discharge to the rainfall intensity and catchment area via the Rational Method:




Qy        is the y year ARI peak discharge (m3/s)

C         is the dimensionless runoff coefficient

     is the average intensity of the design rainstorm of duration equal to the time of concerntration tc and ARI of y year (mm/hr)

A          is the drainage area (ha)



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