Aquatic barrier prioritization in new england under climate change scenarios using fish habitat quantity, thermal habitat quality, aquatic organism passage, and infrastructure sustainability

Abstract

Improperly designed road-stream crossings can fragment stream networks by restricting or preventing aquatic organism passage. These crossings may also be more vulnerable to high flow events, putting critical human infrastructure at risk. Climate change, which emphasizes the need for suitable thermal habitat, and is also predicted to increase the frequency and magnitude of extreme floods, underscores the importance of maintaining stream connectivity and resilient infrastructure. Given the large number of road-stream crossings and the expense of replacement, it is important to prioritize removals and account for the multiple benefits of these management actions. I developed an aquatic barrier prioritization scheme that combines potential habitat gain, stream thermal resilience, aquatic organism passage, and culvert risk of failure. To assess relative thermal resilience, I deployed paired air-water thermographs in several New England watersheds and analyzed thermal sensitivity (relationship of water to air temperature) and exposure (duration, frequency, and magnitude of warm stream temperature episodes) among streams. These were combined into a single metric of thermal resilience corresponding with the distance of that stream's sensitivity and exposure from the watershed median. To test the relationship between risk of failure, culvert dimensions, and stream connectivity, I developed a logistic regression to predict risk of failure using data from two watersheds that experienced extreme flooding from Hurricane Irene (2011). Finally, I applied the resultant prioritization scheme to 66 road-stream crossings in the Westfield River watershed (MA).