Determining the sediment trapping capacity of grass filter strips

Sedimentation resulting from soil erosion degrades the surface water environment. This study determines the sediment trapping capacity (STC) of grass filter strips and how slope gradient and vegetation cover affect it. STC is defined as the maximum sediment trapped within vegetative filter strips (VFS) under given conditions. An exponential model was derived to mirror the relationship between instantaneous sediment trapping efficiency and runoff duration, with findings that STC is closely related to the initial efficiency and attenuation coefficients. The model effectively describes the sediment trapping process, and demonstrates that STC decreases with increasing slope and increases with vegetation cover. Grass strips have a small sediment trapping thickness measured in mm or cm, and grass stems and leaves have little influence on STC, which indicates that reasonable forage cutting may have little influence on sediment removal. STC is an intrinsic characteristic of VFS, and it can be recommended to assess the VFS performance in trapping sediment in severe soil erosion areas. A sediment trapping modulus at the watershed scale based on STC, can offer help to effectively evaluate soil and water conservation engineering and transformation of cropland into forest and grassland in China. (C) 2011 Elsevier B.V. All rights reserved.