Submitted to: Soil Erosion Conservation and Rehabilitation
Publication Type: Book / Chapter
Publication Acceptance Date: January 4, 1996
Publication Date: N/A
Interpretive Summary: Runoff is the primary driving variable in the water-induced erosion process. Although the impact of rain drops detaches soil particles, it is flowing water which transports the detached particles to areas on concentrated flow. Accurate estimation of the effects of an agricultural management system on the volume and rate of runoff is essential in the evaluation and planning associated with soil and water conservation. The two primary methods to compute runoff are the SCS Curve Number method which is based on total storm rainfall and an initial abstraction and a rainfall excess method which generally uses a infiltration equation with a rainfall excess routing equation.
Technical Abstract: Several methods of estimating runoff volume and peak discharge from agricultural fields are presented. The first method is the SCS Curve Number method used to compute direct storm runoff and an SCS graphical method based on time of concentration and storm type to compute peak discharge rates. The second method is based on a rainfall excess approach which uses an infiltration equation with time intensity rainfall input to generate rainfall excess. The rainfall excess is then routed using some form of the shallow water equations. Examples of the method are presented using the Green and Ampt equation for infiltration and the kinematic wave model for a single plane for routing. Approximations of the infiltration/runoff process based on the rainfall excess approach and developed for the Water Erosion Prediction Project are also presented. Finally, implementation of these methods within simulation models is discussed.