Sediment-trapping Effectiveness of Stiff-grass Hedges

Flume studies showed that narrow hedges of tall, stiff grasses across locations of concentrated overland flow have great potential for retarding runoff and reducing sediment losses. Hedges of switchgrass and vetiver caused backwater depths of up to 400 mm and trapped more than 90% of sediment coarser than 125 mm. Lesser percentages were trapped as sediment size decreased, with only about 20% of the material finer than 32 mm caught. Sediment trapping resulted mostly from upslope ponding by the hedges rather by filtering action, so the physical characteristics of the different grasses were important primarily to the extent that they retarded flow.