Presenter/s: Luke Tillmann
Symposium Session: 2023 - 05 Restoration as Risk Reduction: Climate Resilience
Topics covered: climate change, flood, floodplain, groundwater, hydraulics, and modeling
In riverine ecosystems throughout the Western United States, the convergence of water scarcity, competing land use priorities, climate change, and aging flood infrastructure requires urgent solutions to simultaneously sustain ecosystem functions, address flood risk, and secure water for agricultural use. Floodplain rehabilitation opportunities can be identified, prioritized, and designed to increase naturally occurring groundwater recharge leading to many benefits including aquifer replenishment, climate resilience, flood-risk reduction, and ecosystem enhancement.
Ecological Floodplain Inundation Potential (EcoFIP) is a methodology and toolbox that facilitates multiple levels of identification, screening, and evaluation of multi-objective floodplain rehabilitation projects. EcoFIP leverages topographic data, hydrology, hydraulic modeling, soil characteristics, and groundwater data to estimate changes in ecosystem benefits resulting from physical alterations to river corridors (e.g., floodplain lowering, levee setbacks, revegetation) and changes in flow conditions (e.g., climate change, reservoir reoperation). EcoFIP can estimate these benefits at macro (river reach) and micro (site-level) scales, enabling evaluation of the ecological characteristics of any boundary of interest for various historical or potential flow regimes. These gains can be reported in metrics such as acre-days of inundated floodplain area, acre-days of suitable floodplain habitat (for salmonids or other species), and groundwater recharge volumes summarized over a range of water years. Using a computationally efficient architecture, EcoFIP solves the problem of needing to run time-intensive hydraulic simulations to quantify ecohydrological outcomes of different long-term hydrogeomorphic scenarios.
A case study applies EcoFIP to assess a 50-mile reach of the Upper San Joaquin River between Friant Dam and Chowchilla Bifurcation Structure, in support of the California Department of Water Resources’ Central Valley Flood Protection Plan and Conservation Strategy. The analysis is evaluating current and future flow regimes with the goal of identifying potential multi-objective floodplain rehabilitation sites, that provide high-quality salmonid habitat, and maximize groundwater recharge from floodplain inundation.