Question

In curve number method if \(Q\) is actual runoff, \(P\) is rainfall, \(I_a\) is initial abstraction and \(S\) is storage capacity, then the relationship is shown by:

• A. \( Q = \dfrac{(P-0.8S)^2}{P+0.2S} \)
• B. \( Q = \dfrac{(P-0.2S)^2}{P+0.8S} \)
• C. \( Q = \dfrac{(P+0.2S)^2}{P-0.8S} \)
• D. \( Q = \dfrac{(P+0.8S)^2}{P-0.2S} \)

Hint:

In SCS Curve Number Method, always remember: \[ I_a = 0.2S \] and the standard runoff equation: \[ \boxed{ Q = \frac{(P-0.2S)^2}{P+0.8S} } \] Memory Trick: \[ \text{“0.2 below and 0.8 below denominator”} \] which helps remember the coefficients correctly.

Answer 1

The Correct Option is B