The flooding maps depict the projected change in the 10- and 100-year flood inundation depth and area for the Lower Snohomish floodplain. Maps were developed by combining an unsteady-flow hydraulic model for the lower Snohomish River with projections of changing storm surge, SLR, and riverine flooding. These provided boundary conditions for the hydraulic model, which was used to estimate the combined effects of sea level rise and changing peak flows on flood inundation. Ten Global Climate Model (GCM) projections with the highest fidelity to Pacific Northwest climate from the Coupled Model Inter-comparison Project phase 3 (CMIP3; Meehl et al., 2005) were downscaled using the Hybrid Delta (HD) approach to arrive at projected temperature and precipitation changes for the 2040s (2030-2059) and the 2080s (2070-2099) under the A1B greenhouse gas scenario. Lower- and upper-end ranges of projections are provided.

Source: Mauger, Guillaume and Se-Teun Lee (2014). Climate Change, Sea Level Rise, and Flooding in the Lower Snohomish River Basin.