Estimates of soil erosion and best management practice effectiveness at forestry stream crossings in North Carolina

Abstract

Approach ways of forest road and skid trail stream crossings can be direct pathways for sediment delivery to stream channels if not properly managed. Forestry best management practices (BMPs) can reduce erosion and sedimentation, but their effectiveness can vary by application. This study characterizes implemented stream crossing types and methods of access, and quantifies the effectiveness of BMPs implemented at 220 stream crossings in four ecoregions of North Carolina. We estimated soil erosion rate and quantity using the Universal Soil Loss Equation (USLE)-Forest methodology. Estimates of BMP effectiveness were explored by comparing on-site modeled estimates with modified modeled estimates that would be more discerning of no-BMP scenarios. Statewide, portable bridges and overland skid trails were the most frequently observed stream crossing type and access method, respectively. BMPs at stream crossings were properly implemented at a rate of 90.1%. Although increased BMP implementation scores were significantly associated with decreasing erosion estimates, the relationship was weakly correlated (<i>p</i> &amp; 0.0001, <i>R</i>² = 0.08). There were no differences in modeled erosion rates by ecoregion (<i>p</i> = 0.2671). Statewide, overland skid trail crossings had lower modeled erosion rates than bladed skid trails (<i>p</i> = 0.0432) and haul roads (<i>p</i> = 0.0002). Erosion rates modeled at stream crossings when the tract had active operations were significantly higher compared to stream crossings on inactive/closed tracts (<i>p</i> &amp; 0.0001). Most stream crossings observed (54%) had modeled erosion quantities less than 0.1 Mg crossing^–1 y^–1. Results show that most forestry-related stream crossings examined in this study across North Carolina adequately applied BMPs and reduced erosion potential.