Effectiveness of best management practices for sediment reduction at operational forest stream crossings

Temporary skid trail stream crossings have repeatedly been identified as having considerable potential to introduce sediment to streams. Forestry Best Management Practices (BMPs) have proven to be effective for controlling erosion and subsequent sedimentation, yet few studies have quantified sedimentation associated with various levels of BMPs for skidder stream crossings. Three skid trail stream crossing BMP treatments were installed and replicated three times to quantify BMP efficacy for reducing sedimentation. BMP treatments were: (1) slash, (2) mulch and grass seed, and (3) mulch, grass seed, and silt fence. Water samples were collected daily both upstream and downstream from operational skidder stream crossings for one year following timber harvesting and BMP treatment installation. Samples were evaluated for total suspended solids (TSSs). Results indicate that both slash and mulch treatments effectively reduced TSS following harvesting. Slash could be the preferred method of stream crossing closure, due to lower cost, especially if application is incorporated into logging operations. However, if slash was being utilized for biomass and was not available, seed and mulch is a viable option for stream crossing closure. The mulch, seed, and silt fence treatment was the most expensive treatment and led to increased TSS, probably due to silt fence installation disturbances near the streams. Thus, silt fences should not be installed directly adjacent to streambanks, if other alternatives exist.

► Logging slash, straw mulch, and straw mulch with silt fence reduced sediment inputs from skidder stream crossings.
► The straw mulch with silt fence treatment was less effective, probably due to disturbances caused by installation.
► Within the maximum rainfall category, all treatments reduced TSS values, but the slash treatment was most effective.
► Skid trail slope, area, distance between water control structures, and bare soil controlled BMP effectiveness.
► Slash was the most cost-effective treatment for closing temporary skidder stream crossings.