Factors influencing roadside erosion and in-stream geomorphic stability at road-stream crossings for selected watersheds, North Shore, Minnesota, USA.

摘要

Currently, 10 major watersheds in Minnesota's North Shore exceed state water quality standards for turbidity (10 NTU) a surrogate for total suspended solids. In this region, recent anthropogenic disturbances can be attributed to roadway construction and maintenance. The presence of roadways can pose a serious threat to ecosystem functions, altering local and landscape hydrology, fragmenting riparian areas, and delivering chemical pollutants and suspended sediments to nearby waterways via surface runoff and seepage.;This study examined the current extent of hydrologic connectivity between roads and streams, by investigating roadside erosion for select sub-watersheds within the North Shore watershed of Minnesota, USA. Surveys were conducted at 54 road-stream crossings along 12.2 km of roadways in the summer of 2010. A Road-stream connectivity analysis found roads increase the drainage density of North Shore watersheds by approx. 1.45--9.47%. Measureable erosion was observed at 64.8% of survey sites (gully, or rill) totaling 93.26 m 3, with an average loss per site of 1.73 m3, or 7.64 m3/km. Traffic intensity, road construction, parent material, stream order, soil k factor, hillslope gradient best predicted erosion for this dataset using logistic regression at local and watershed wide scales.;The effect road-stream crossings as a localized stress on stream stability was also examined at seven sites, using Rosgen level I classification and Pfankuch stability metrics. This qualitative analysis of stream stability upstream and downstream of road-stream crossing structures indicated study road-stream crossings are causing localized instability. Assessments indicated stream segments are negatively impacted both upstream and downstream of crossing structures.