Vegetated filter strips(VFSs)have been recognized as an effective and environmentally-friendly beneficial management practice for preventing sediments from cropland to enter surface water.However,the relationship between filter strip width and reduction rate is difficult to be determined because of concentrated runoff in watershed scale.The Vegetated Filter Dimensioning Model(VFDM)is a mathematical tool coupled with distributed hydrological model that was successfully developed to determine the optimal dimensions and/or efficiency of vegetated.The number of rills in a relatively homogeneous hydrological unit(RHHU,i.e.hillslope),the basic computational unit of VFDM,is a key parameter for routing concentrated flow and sediments and therefore,the design of the vegetative filter.