332 - A Case Study for the SR544 Bridge Crossing of the Nooksack River in Whatcom County, WA USA - Using 2D Modeling to Inform Designs that Balance Resilience, Forward Compatibility, Hydrotechnical Risks with Climate Changing Flows in Infrastructure Engineering

This paper looks at a case study using 2-dimensional (2D) modeling to characterize complex flow conditions at and around critical infrastructure improvements in the Nooksack River mainstem channel and corresponding floodplain, at the State Route (SR) 544 bridge crossing near Everson, WA in Whatcom County USA. The 2D modeling was used to assess existing and forward-looking mitigation scenarios related to flood damage to the bridge; and balances hydrologic, hydraulic, fluvial geomorphic and sediment transport processes to find a resilient and forward-compatible solution that meets the needs of the infrastructure operational requirements while also addressing floodplain scale management needs and long-term geomorphic function. The site is located in a unique fluvial geomorphic riverine landscape, perched vertically on the leftbank (orientation looking downstream) of a historical active channel migration zone overlapping a broad and complex floodplain. Whereby, a significant component of distributed flood flows can impact not only local communities in the United States, but can also traverse the landscape to cross the international border and impact communities in neighboring Canada. 2D modeling informed hydrotechnical assessments and detailed engineering design of options that incorported resilient alternatives allowing the infrastructure owner to manage risks and coordainte with stakeholders now and in the future, addressed forward-looking expected changes in hydrologic conditons, restored and enhanced floodplain connectivity using geomorphic supported design concepts, combined with enhanced sediment transport to address long-term mitigation of sediment aggregation trends while maintaining and enhancing functional geomorphic conditions, and addressing regional reach-scale floodplain planning goals.