Floodplain Reconnection Optimization with 2D HEC-RAS

Floodplain reconnection projects are nature-based solutions that have great potential to restore channel stability, attenuate stormwater, improve flood resilience, and improve water quality. Floodplain reconnection practices can include berm lowering or removal, floodplain benching, strategic placement of culverts and bridges, and planting forested buffers. However, the suite of possible restoration options for a given study area must consider the multiple uses and functions of river corridors, along with the potential impacts and benefits to adjacent infrastructure. Stakeholders are in need of decision-support frameworks to help identify a combination of restoration projects that will best meet these multiple and sometimes competing objectives and minimize flooding impacts under an overall constraint of limited financial resources. We have created a multi-objective optimization tool that can be wrapped around a two-dimensional hydraulic model (HEC-RAS) to provide a suite of optimal floodplain reconnection options. We illustrate the application of this optimization wrapper to assess impacts of restoration alternatives on flood velocity, depth and duration for a Vermont river. The optimization wrapper is transferable to other sites with existing HEC-RAS models, and can be an important tool for designing and prioritizing the optimal suite of restoration practices along a river