Estuary restoration is a critical piece to the recovery threatened Chinook salmon. In the Skagit River, Wa, where salmon are a cornerstone of tribal culture and economy, it is estimated that an additional 2,700 acres of estuary habitat is needed for a sustainable Chinook population. The delta also supports a strong agricultural economy and community that faces risks from floods and aging infrastructure. Climate change is further anticipated to impact habitat, agriculture, and flooding. As with many places, the Skagit Delta land base is limited resulting in conflicts; key stakeholders formed a partnership under the Farms, Fish and Floods Initiative (3FI) to craft a long term vision for salmon recovery, reduced flood risk, and agriculture viability.
Contributing to 3FI, the Skagit Delta Hydrodynamic Model Project is a landscape-scale assessment to identify a suite of restoration actions that achieve long-term viability of Chinook salmon and flood risk reduction in a manner that protects and enhances agriculture and drainage. Representatives from each interest developed objectives against which restoration concepts could be measured to identify those with the greatest potential to provide multiple benefits. The objectives require hydrodynamic modeling, estimates of habitat structure and smolt production, GIS calculations, and use of local knowledge.
Results/Conclusions
This presentation will provide an overview of the fish, flood and farm objectives and explain how the different types of models and GIS analyses were used to predict ability of a restoration concept to contribute to each objective. For example, a 3-dimentional hydrodynamic model was used to calculate changes in wetted area; duration of inundation; reductions in water surface elevations during flood events; and changes in salinity. Allometery models were used to predict the amount of channel area that may form and informed predictions of the number of Chinook smolts a restored habitat could support annually. These quantitative results were then incorporated into an alternative analysis framework that allowed for a transparent accounting of the benefits and impacts of individual or suites of restoration concepts as well as uncertainty around specific predictions due to model limitations. By working with representatives from the different interest groups throughout this process and getting specific input on the results of the models as well as the format of the alternative analysis, we were able to ensure that the predictions of ecological and societal benefits and impacts were meaningful and that the resulting suite of recommended projects were supported across the interests.