Evaluating Best Management Practices for Ephemeral Stream Protection following Forest Harvest in the Cumberland Plateau

Most states in the United States have established streamside management zone (SMZ) recommendations for minimizing the impacts of forest operations on water quality and aquatic habitat. However, guidelines generally focus more on impacts to perennial streams than on ephemeral streams. An experiment was conducted to evaluate SMZ effectiveness on ephemeral streams in southeastern Kentucky. Ephemeral SMZ treatments included (1) harvest with no equipment limitation, no forest overstory retention, and use of unimproved stream crossings (noSMZ); (2) harvest with no equipment limitation, retention of channel bank trees, and use of improved stream crossings (SMZ1); (3) harvest with equipment restrictions within 7.6 m of the channel, retention of channel bank trees, and use of improved stream crossings (SMZ2); and (4) no harvest (control). Each treatment was replicated a minimum of three times (n of 3 to 6; 18 sites total) at the subwatershed level (0.75 to 8.92 ha). The improved stream crossing types studied included wooden portable skidder bridges, steel pipe/culverts, and PVC pipe bundles. Water samples were taken during storm flows and were analyzed for total suspended solids (TSS), turbidity, settleable solids, and sediment transport rate. Both the SMZ1 and SMZ2 treatments significantly reduced TSS and turbidity over the noSMZ treatment. Water in the SMZ1 treatment exhibited higher TSS and turbidity than the control, whereas the SMZ2 treatment was no different than the control for TSS but higher for turbidity. Use of any improved crossing in ephemeral streams significantly lowered TSS and turbidity compared to unimproved fords. Bridges yielded similar TSS and sediment transport levels as those exhibited by the control but turbidity was slightly higher.