Session A8- Climate change and the design of stream crossings in New England

Several New England states promote designing roadway stream crossings to accommodate fish and other wildlife passage. Recent guidance typically bases such crossing design on stream morphology, providing for spanning the bankfull width plus some bank clearance. Climate change may affect stream morphology, as well as frequency and magnitude of flood events. Current measurements of bankfull geometry may not predict long-term conditions. The presentation explores how climate change in New England and attendant changes in stream morphology and flows may affect design of bridges and culverts for wildlife passage. Changes in intensity and frequency of precipitation events include not only extreme storms, but also the more frequent, smaller events that shape the region’s streams. These hydrologic changes can also alter stream morphology. Coupled with other stressors associated with climate change, such changes affect existing habitat conditions and viability for species that depend on riparian corridors. It becomes increasingly important for this wildlife to be able to move along the stream corridor to find conditions suitable for long-term survival. Recent initiatives to develop stream crossing design standards and regulations focus on design techniques to minimize barriers at road crossings. The design of bridges and culverts, even without considering wildlife passage, must address hydrologic events and stream morphology. Changes in flows and stream geometry associated with climate change pose challenges in designing structures with adequate hydraulic capacity and scour protection to protect the structure itself, without adverse effects to the stream system. Providing for sustainable wildlife accommodation increases this challenge. The presentation will discuss how stream crossing design must consider climate change, exploring implications of hydrologic and morphologic conditions that are difficult at best to predict, and challenging engineers and natural resource professionals to work together to identify practicable design approaches for safe, serviceable stream crossings that provide for habitat resiliency