Abstract
Vegetative filters (VF) are a best management practive installed in many areas to control sediment movement to water bodies. It is commonly assumed that runoff proceeds perpendicularly across a VF as sheet flow. However, there is little research information on natural pathways of water movement and performance of field-scale VF. The objectives of this study were: (1) to quantify the performance of a VF where the flow path is not controlled by artifical borders and flow path lengths are field-scale, and (2) to develop methods to detect and quantify overland flow convergence and divergence in a VF. Our hypothesis is that flow converges and diverges in field-scale VF and that flow pathways that define flow convergence and divergence areas can be predicted using high-resolution topography (i.e., maps). Overland flow and sediment mass flow were monitored in two 13 x 15 m subareas of a 13 x 225 m grass buffer located in Polk County in east-central Nebrasks. Monitoring included a high-resolution survey to 3 cm resolution, dye tracer studies to identify flow pathways, and measurment of maximum flow depths at 51 points in each subarea. Despite relatively planar topography (a result of grading for surface irrigation), there were converging and diverging areas of overland flow in the buffer subareas. Convergence ratios ranged from - 1.55 to 0.34. Predicted flow pathways using the high-resolution topography (i.e., map) closely followed actual flow paths. Overland flow was not uniformly distributed, and flow depths were not uniform across the subareas. Despite converging and diverging flow, the field-scale VF trapped approximately 80% of the incorming sediment.
Keywords
Flow convergence,
grass filters,
overland flow,
sediment trapping,
vegetative filters
Citation
Helmers, M. J.; Eisenhauer, D. E.; Dosskey, Mike G.; Franti, T. G.; Brothers, J. M.; McCullough, M. C. 2005. Flow pathways and sediment trapping in a field-scale vegetative filter. American Society of Agricultural Engineers, Volume 48(3): 955-968
