STREAM FRAGMENTATION AND INFRASTRUCTURE CONDITION IN THE GREAT PLAINS

Abstract

Rivers and streams within the Great Plains have undergone extensive levels of fragmentation by road culverts, which has led to habitat loss, degraded water quality, and a loss of aquatic biodiversity. There is a pressing need to retrofit the most problematic structures to ensure aquatic organism passage. At the same time, a vast majority of the road crossing infrastructure within the Great Plains is beyond its projected lifespan, and significant investments will be needed to ensure that this transportation infrastructure remains safe and functional. Historically, these two problems have been addressed separately. The aim of this study is to identify road culverts that are in need of restoration based on both ecological impact and its state as infrastructure. By identifying locations that are in need of repair for both of these parameters managers can pool their funds and restore more sites than previous operations. We surveyed over 700 road-stream crossings to determine if they were fragmenting aquatic habitat, and to determine the condition of the structure. We then developed an index of ecological impact and an index of infrastructure condition based on 20 physical variables measured at each crossing, and the spatial relationships among these structures in the river network. The survey revealed a large number of crossings that were both fragmenting the river network and in poor physical condition. These crossings are high-priority locations where culvert replacement would have both high ecosystem benefit and would eliminate a piece of transportation infrastructure with a high risk of failure. It is hoped that future river restoration practices can be collaborative efforts between conservation managers and those who are managing infrastructure.