Compute the 25-year runoff for the Olympia watershed shown above. Three types of flow conditions exist from the highest point in the watershed to the outlet. The upper portion is 10.0 hectares of forest cover with an average slope of 0.15 m/m. The middle portion is 2.5 hectares of single family residential with a slope of 0.06 m/m and primarily lawns. The lower portion is a 2.0 hectares park with 450 mm storm sewers with a general slope of 0.01 m/m.
