Stormwater Rational Method

Q = C * i * A peak runoff in cfs and gpm with bundled C values.

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Formula and source

Q = C × i × A. C from bundled runoff coefficients per surface; i from user-supplied design rainfall intensity; A in acres yields Q in cfs (1 cfs ≈ 449 gpm).

Rational method by name (public hydrology). C-values from public engineering practice.

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