Best Management Practices Influence Sediment Delivery from Road Stream Crossings to Mountain and Piedmont Streams

Forest road attributes and best management practices (BMPs) influence sediment delivery at stream crossings. We quantified sediment delivered from 37 stream crossings on truck roads representing a spectrum of road quality and BMPs. Approaches were categorized into road/BMP quality ranks based on slope, template, distance to nearest water control structure, and level of surface armoring (BMP-low, BMP-standard, and BMP-high). Sediment traps installed at stream crossings were monitored bimonthly for one year. Mean sediment mass losses were low; 76 percent of approaches lost < 0.1 Mg yr1, and 94 percent of approaches lost < 1 Mg yr-1. Piedmont approaches provided greater (a < 0.10) median sediment masses (0.04 Mg yr-1) and rates (4.8 Mg ha-1 yr-1) than ridge and valley approaches (0.01 Mg yr-1, 0.5 Mg ha-1 yr-1). Median sediment masses differed among road quality rankings (P < 0.0011). Approaches of BMP-low, BMP-standard, and BMP-high produced median values of 0.45 Mg yr-1, 0.02 Mg yr-1, and 0.001 Mg yr-1. Two BMP-low steam crossing approaches produced sediment masses >1 Mg yr-1, and these sedimentation issues could have been mitigated by additional water control and additional cover of road templates. This research substantiates that appropriate BMP implementation at stream crossings can minimize stream sedimentation.