Characteristics, predicted erosion, and costs for different levels of forestry best management practices at skidder and truck stream crossings in the Mountains, Piedmont, and Coastal Plains of Virginia, USA

摘要

Operational stream crossings on forest roads and skid trails are potential sediment delivery areas from timber harvests that can negatively affect water quality if best management practices (BMPs) are not sufficiently implemented. Virginia has three major physiographic regions (Mountains, Piedmont, Coastal Plain), and the diverse topographies require some specificity of BMP guidelines for water quality protection. Furthermore, truck roads and skid trails utilize different drainage and erosion controlBMPs to maintain sufficient working conditions and access to timber. As a result, differing BMP approaches and implementation levels for roads and trails inherently have different associated costs. We evaluated BMP implementation levels on 154 stream crossing approaches (3 regions x 2 road types x a minimum of 25 stream crossings). We categorized the crossings as BMP- (failed to meet recommended BMPs), BMP-standard (met recommended guidelines), or BMP+ (exceeded recommended guidelines). We estimated hypothetical costs for elevating BMP- stream crossings to BMP-standard and BMP+ and costs of elevating BMP-standard to BMP+. Average BMP implementation audit scores for stream crossings were 88 on skid trails and 82 on truck roads. To upgrade from a BMP-to BMP-standard, the cost-benefit ratio ($/Mg of sediment prevented) averaged $248.58/Mg for skid trails and $670.33/Mg for truck roads. Enhancement from BMP-standard to BMP+ level is less economically efficient and BMP implementation efficacy at streamcrossings appears to plateau at the BMP-standard level.