Culvert Effects on Stream and Stream-Side Salamander Habitats

Abstract

Road and stream intersections require a crossing that allows safe passage of water and vehicles. Culverts are normally used when roads cross small streams. Recently, passage of aquatic organisms through culverts has received increased attention. We used a geographic information system (GIS) analysis to determine the degree of salamander habitat fragmentation in Tucker and Randolph counties in West Virginia, USA. We visited state roads with culverts and categorized salamander barriers as complete, partial, or nonbarrier, based on outlet hang, culvert slope, and substrate. Complete barriers occurred at 55.0% of the sites visited and partial barriers at 34.2%. We found that 20.6% of the total stream length in the Dry Fork watershed and 18.4% in the Shavers Fork watershed were isolated by at least a partial barrier. Outlet hang height and the presence (or absence) of streambed substrate were the main determinants of stream salamander passage. Outlet hang was positively correlated with stream gradient and culvert slope. Culverts containing streambed substrate occurred on lower gradient streams, had lower culvert slope, and had a greater width compared to culverts lacking substrate. Solutions to facilitate movement of salamanders and other aquatic organisms are needed to maintain stream connectivity and provide mitigation opportunities.