2D XBeach model input files – Unalakleet, Alaska

Model grids (x.grd, y.grid), elevations (bed.dep, in meters above NAVD88) and other XBeach-specific setup files (params, disch_loc_file, disch_timeseries_file, jonswap, waterlevel_ini, ne_layer, bedfricfile, and stormtide) were developed for surfbeat (XB-SB) and non-hydrostatic (XB-NH)simulations. See Deltares manual (2025) for a description of model files and differences between the surfbeat and non-hydrostatic modes. The XB-SB and XB-NH models can be run independent of each other or sequentially to leverage the strengths of both XBeach modes for a comprehensive simulation of wave dynamics, particularly in the context of swash zone (active beach area) processes and wave runup. The SB mode is computationally efficient and well-suited for capturing long-wave (infragravity) variations and their interactions with the shoreline, including morphodynamic change (erosion and sedimentation). The NH mode provides a detailed, wave-resolved simulation that includes individual wave overtopping. Models are set up in the cartesian coordinate system (Universal Transverse Mercator (UTM) zone 4 N) and elevations are referenced to the North American Vertical Datum of 1988 (NAVD88). Bed level data files of both the XB-SB and XB-NH models were populated using nearest grid-point mean TBDEM elevations, except in regions of breakwaters, constructed berms, and elevated roads, which were manually digitized to ensure that maximum elevations were accurately represented. Bed friction was populated using established Manning n values related to land-use map data (OCM 2025; Brunner 2024) but capped at a friction value of 0.028. Model setup was calibrated and validated against observation-based flood extents and surveyed high-water marks (NCDC 2019; Horen and others 2022, USGS, 2024).