Climate robust culvert design: Probabilistic estimates of fish passage impediments for Washington State


Mauger, G.S., S.Y. Lee, J.S. Won, K. Byun, and A.F. Hamlet, 2018. Climate robust culvert design: Probabilistic estimates of fish passage impediments. Final report for the Skagit Climate Science Consortium. Climate Impacts Group, University of Washington, Seattle.


This report describes a new tool that is designed to support climate-robust culvert design. In addition, the report describes an evaluation of the meteorological and streamflow datasets that are the basis for the tool, with the goal of supporting the use and interpretation of the results.  The tool calculates the probability that the proposed culvert size would fail to meet the state’s design criteria over its design lifetime. By emphasizing relative changes in streamflow (% change) our approach minimizes the influence of model biases. The approach is also an improvement over past studies in that it provides a specific estimate of the probability of failure during the design lifespan, integrating the range of model projections into a single number summarizing the implications for a particular culvert size and location. The tool is flexible and designed to accommodate a range of different design lifetimes and proposed culvert sizes.