Abstract: A numerical model of the Lower Columbia River, validated to water surface elevations, has been generated using the Adaptive Hydraulics (AdH) code. The model boundary conditions include an ocean tidal boundary and five inflows: the Lewis, Cowlitz, Willamette, and Sandy Rivers, and the Columbia River at Bonneville Lock and Dam. The model, which spans approximately 146 river miles, accurately reproduces water surface elevations measured in the field at several locations along the model domain. An examination of the AdH model’s Friction Library was also conducted. The Friction Library was used in this application to estimate the effects of pile dikes. Rather than model individual piles in the model mesh, the piles were modeled using the Friction Library’s submerged vegetation material type. Through testing of this application, it was determined that the Friction Library approach, which enhances model run time and efficiency, can accurately reproduce the global effects of pile dike fields. Additionally, the validated model was used to analyze three sea level rise (SLR) scenarios, which correspond to predicted SLR at Astoria, OR, at 50, 75, and 100 years from the present (0.5 meter [m], 1.0 m, and 1.5 m, respectively).