Environmental science · Grades 9–12
Runoff in a simplified catchment · formula reference
Use a uniform rainfall event and a stated constant runoff fraction. Real catchments require more detailed models.
Formula
Use a uniform rainfall event and a stated constant runoff fraction. Real catchments require more detailed models.
V = rain depth × area × runoff fraction
Worked example
Uniform rainfall of 89 mm falls on 12 hectares. In a simplified model, 0.6 of the rain becomes runoff. Find runoff volume in m³. Round the final result to 4 decimal places if needed. Answer in m³.
Convert mm to m and hectares to m²: (89/1000)(12×10000)(0.6).
6408 m³
Prerequisites and checking
Algebra and the topic definitions. Keep units and rounding consistent. State the model conditions before applying the formula.
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