Sediment trapping within streamside management zones on two clearcut sites in the Georgia piedmont
Ward, Jason M
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A study was conducted to evaluate the effectiveness of streamside management zones (SMZs) for reducing sediment transport from concentrated flow swales draining two clearcut timber harvesting sites in the Georgia Piedmont. Both clearcuts had undergone mechanical and chemical site preparation as well as planting. Silt fences were used to trap sediment transport from zero-order ephemeral swales at the edge of SMZs. Five control swales and nine treatment swales were studied, but one control swale was removed from the analysis. A double mass curve approach was used to graphically compare sediment accumulation rates at the edge of SMZs to accumulation rates within the SMZs at a distance consistent with current recommendations for SMZ width in Georgia. SMZ efficiencies ranged from 27% to 99%. No statistical model was found to explain SMZ efficiencies based on SMZ and contributing area characteristics. The Revised Universal Soil Loss Equation (RUSLE) was used to predict sheet and rill erosion for specific rain events on the study sites and a delivery ratio of 0.25 was calculated. SMZs had a quantifiable ameliorating effect on sediment transport from concentrated flow swales on our clearcut study sites.