Optimizing River Floodplain Restoration Design to Mitigate Climate Change-Induced/Reductions in Summer River Low Flows
Project ID: R25AP00347
Federal Agency: U.S. Bureau of Reclamation
Partner Institution: University of Idaho
Fiscal Year: 2025
Initial Funding: $225,658
Total Funding: $225,658
Principal Investigator: Tonina, Daniele
Agreement Technical Representative: Davin, Jody
Abstract:
Background and Objectives
Climate change will reduce winter snowpack in the Pacific Northwest (PNW), shifting runoff earlier in the year and leading to reduced summer low flows, with detriment to river ecosystems and summer water supply. River floodplain restoration practices, such as Stage 0 restoration, valley restoration, and wet meadow restoration, are implemented in the Columbia River Basin (CRB) with the purpose of restoring juvenile salmonid habitat. Such practices can also affect summer low flows by increasing surface and groundwater storage but also increasing riparian evapotranspiration. There is interest for floodplain habitat restoration to mitigate decreases in summer low flows from climate change to benefit fish migration and juvenile rearing habitat, yet the effects of design parameters on restoration impacts to summer low flows remain unclear (Hunt et al. 2018, Nash et al. 2018, Hunt et al. 2020, Nash et al. 2020). Thus, current knowledge is insufficient to design floodplain restoration projects to maximize mitigation of climate change impacts to summer low flows. Addressing these knowledge gaps will allow informed decision-making regarding floodplain restoration benefits that accrue from habitat restoration. Critical needs include understanding how to 1) design individual restoration projects to maximize benefits to summer low flows at a local scale, and 2) plan locations of restoration projects that maximize potential flow benefits at larger river network scales. University of Idaho propose to address #1 in the current Case Study (Phase 1), which sets the stage to address f2 in a future study (Phase 2).
Simulation results will be used to determine values of restoration project design parameters that are necessary to mitigate climate-reduced summer low flows at particular sites. A series of such plots for different design parameters and site characteristics will be compiled into a set of design curves and corresponding design equations. These design curves and equations can then be used to determine site design parameters necessary to mitigate for hydrologic impacts of climate change early in the design process.