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 retar ding runoff and reducing sediment losses. Hedges of switchgrass and ve tiver caused backwater depths of up to 400 mm and trapped more than 90 % of sediment coarser than 125 mu m. Lesser percentages were trapped a s sediment size decreased, with only about 20% of the material finer t han 32 mu m caught. Sediment trapping resulted mostly from upslope pen ding by the hedges rather by filtering action, so the physical charact eristics of the different grasses were important primarily to the exte nt that they retarded flow.