Evaluating the efficacy of enhanced wildlife bridge infrastructure in Durham, North Carolina

Ron Sutherland, Wildlands Network
Emily Blanchard, Wildlands Network
Topic Area
Terrestrial Wildlife and Ecosystem Interactions with Transportation

The Triangle region of North Carolina (Raleigh, Durham, and Chapel Hill) is one of the fastest growing urban areas in the southern United States. Within the Triangle, US 15-501 is a prominent, high-traffic highway connecting the cities of Durham and Chapel Hill. This stretch of highway crosses over New Hope Creek, one of the only remaining major natural habitat corridors in the region that connects larger protected areas to the north and south. As human population growth in the region continues to increase, corresponding increases in vehicular traffic have necessitated upgrades to bridge infrastructure, while at the same time posing substantial threats to wildlife connectivity. In 2007, thanks to a successful effort by local citizen activists, NCDOT engineers modified their pending plans to widen the 15-501 New Hope Creek bridge to include significant bridge heightening and lengthening in order to facilitate wildlife passage underneath. A pre-study was performed to evaluate wildlife passage under the original bridge prior to construction, but no follow-up was conducted. Since 2017, Wildlands Network has engaged in a post-study using a substantial array of camera traps to evaluate the efficacy of the modified 15-501 bridge infrastructure in facilitating wildlife traffic along the corridor beneath the underpass. We also have monitored a much smaller bridge on a different highway (NC 54) over the same New Hope Creek corridor, in the hopes of providing a control system for the larger modified bridge. Our initial results have found that the 15-501 bridge enables substantial usage by wildlife, especially larger animals such as deer and coyotes, thereby reducing risks to motorists and promoting connectivity along the creek corridor. The smaller NC 54 bridge does allow a surprising amount of wildlife passage underneath, but to a lesser extent than the larger structure further upstream. We hope to be able to use the 15-501 story as a successful model to promote other wildlife-infrastructure projects across North Carolina and beyond.

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