SIMULATION OF OVERLAND FLOW ON SHORT FIELD PLOTS

Overland flow is a major component in any runoff event where the cultural practices significantly affect the watershed runoff hydrograph. A model based on the kinematic flow theory is proposed that satisfactorily predicts overland flow on very rough, short slopes. The model includes retention storage, provisions for a variable point‐infiltration rate and a variable coefficient of friction, the ‘drying up’ of the upstream end of the slope during recession, and a variable area infiltration rate that is a function of the water surface area during recession. Field hydrographs from fallow erosion‐study plots were analyzed for retention storage and estimated values of the Darcy‐Weisbach coefficient of friction. These results were used in the model to simulate hydrographs that were compared with field hydrographs to test the concepts used in the model. The model with a constant Darcy‐Weisbach coefficient of friction or Manning's n adequately describes overland flow on short erodible slopes. (Key words: Hydrology; overland flow) Copyright 1968 by the American Geophysical Union.