Civil Engineering MCQAE Level Civil Engineering
In the SCS Curve Number (CN) method for estimating runoff depth Q from rainfall P (in mm), the formula is:
Irrigation EngineeringSoil Conservation RunoffMEDIUM
Choose the correct answer
A
Q = (P - Ia)^2 / (P - Ia + S)
B
Q = P x CN / 100
C
Q = C x I x A
D
Q = P - 0.2S (only initial abstraction)
Correct Answer
A. Q = (P - Ia)^2 / (P - Ia + S)
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SCS-CN: Q = (P - 0.2S)^2 / (P + 0.8S) for P > 0.2S, else Q = 0. S = (25400/CN - 254) mm (potential maximum retention). Ia = 0.2S (initial abstraction). CN depends on soil type, land use, and AMC (Antecedent Moisture Condition).
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