Connected Rivers and Roads: Considering Climate Change in Stream Connectivity Design

Road-stream crossings are essential components of transportation infrastructure networks. Yet undersized road-stream crossings are known to degrade riparian ecosystems by impeding fish and wildlife passage, sediment transport, streamflow, and other floodplain processes. There is also increasing recognition that undersized crossings are more failure-prone and undermine the resilience of human communities, especially in regions where climate change is expected to increase the magnitude and/or frequency of extreme precipitation and streamflow events. Thus ecosystem restoration practitioners, community planners, and transportation engineers have a shared interest in climate-informed road-stream crossing design and a stake in the active discussion in the research community about what methods are most appropriate for designing infrastructure for a changing climate. Traditional approaches for estimating design flows assume that the past is a good guide to the future. This is more formally known as a “stationarity” assumption, and presently there are no well-accepted non-stationary design flow estimation techniques. In this presentation I will briefly review observed and predicted hydroclimatic changes in the Northeast U.S. that have implications for road-stream crossing design and discuss a number of recently proposed stationary and non-stationary methods for estimating design flows in a changing climate. The perils of using dated precipitation or streamflow records for project design in the Northeast will be emphasized.