Estimate the runoff from 140 mm of rainfall on a 350-ha watershed. The land use is open with a grass cover before urbanization. The soil is 45% group B and 55% group C. The curve numbers for open land with grass cover are 69 for Group B and 79 for Group C. After urbanization, the surface runoff is reduced by 100 mm. How much additional runoff is caused by urbanization?

Compute the runoff from a 5-in. rainfall from a watershed which has four soil groups overall and the land cover is fair grass cover. Also, estimate the effect of urbanization if the land cover changed into four urban categories as shown below: Land Use Land use Soil Group Before Urbanization After urbanization Grass Residential 40% C Grass Grass 25% D Grass Commercial 20% Grass Industrial 15% D CN CN Before Urbanization After Urbanization 79 83 83 80 79 94 33 83 93