Modeling hydrology and sediment transport in vegetative filter strips

The performance of vegetative filter strips is governed by complex mechanis ms. Models can help simulate the field conditions and predict the buffer ef fectiveness. A single event model for simulating the hydrology and sediment filtration in buffer strips is developed and field tested. Input parameter s, sensitivity analysis, calibration and field testing of the model are pre sented, The model was developed by linking three submodels to describe the principal mechanisms found in natural buffers: a Petrov-Galerkin finite ele ment kinematic wave overland flow submodel, a modified Green-Ampt infiltrat ion submodel and the University of Kentucky sediment filtration model for g rass areas. The new formulation effectively handles complex sets of inputs similar to those found in natural events. Major outputs of the model are wa ter outflow and sediment trapping on the strip. The strength of the model i s a good description of the hydrology within the filter area, which is esse ntial for achieving good sediment outflow predictions or trapping efficienc y. The sensitivity analysis indicates that the most sensitive parameters fo r the hydrology component are initial soil water content and vertical satur ated hydraulic conductivity, and sediment characteristics (particle size, f all velocity and sediment density) and grass spacing for the sediment compo nent. A set of 27 natural runoff events (rainfall amounts from 0.003 to 0.0 3 m) from a North Carolina Piedmont site was used to test the hydrology com ponent, and a subset of nine events for the sediment component. Good predic tions are obtained with the model if shallow uniform sheet flow (no channel ization) occurs within the filter. (C) 1999 Elsevier Science B.V, All right s reserved.