CIVE 4179 Homework #4 Due Monday, March 5, 2012 Please state and briefly discuss or justify any necessary assumptions. Problem 1. Using the USLE, estimate the annual erosion from a 100 ha. forested watershed assuming the following: R=112 tonnes/ha/year the forest is in fair condition with 40% cover; average slope is 3% the soils are clay loam in hydrologic group C. Problem 2. Estimate the runoff in cm and in m 3 , average depth of infiltration in cm, and erosion in kg from a single 6-cm rainfall event occurring in 1.5 hours on the catchment described above in Problem 1. There was no rainfall on the catchment in the week preceding the 6-cm rain. Investigate how the single-event erosion changes depending on the assumed shape of the rainfall hyetograph (hydrograph) by comparing the erosion from the constant-intensity storm above to a storm of 6 cm/hour for the first half hour, 4 cm/hour for the next half hour, and 2.0 cm/hour for the last half hour. Briefly discuss your findings.
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