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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 6cm 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 6cm rain.
Investigate how the singleevent erosion changes depending on the assumed shape of the rainfall hyetograph
(hydrograph) by comparing the erosion from the constantintensity 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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 Spring '12
 williamelliot

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