NUMERICAL APPROACH TO THE OVERLAND-FLOW PROCESS IN VEGETATIVE FILTER STRIPS

Agricultural and other disturbed lands contribute to non-point source pollution of water bodies (streams and lakes). Vegetative filter strip s (VFS) are often recommended to reduce off-site impacts. Design guide lines to optimize the performance of VFS are not readily available. A process-based model is presented to simulate the hydrology of a Vegeta tive Filter Strip for a given event. The model consists of a quadratic finite element overland flow submodel, based on the kinematic wave ap proximation, coupled with an infiltration submodel based on a modifica tion of the Green-Ampt equation for unsteady rainfall. The model is us ed to study the effect of soil type, slope, surface roughness, buffer length, storm pattern and field inflow on the VFS performance. Filter performance, i. e., reduction of the runoff volume, velocity and peak, is higher for denser grass cover, smaller slopes and soils with highe r infiltration capacity. Time to peak(s) depended mainly on the roughn ess-slope combination.