CoSMoS 3.2 Northern California sub-regional tier 3 2D XBeach model input files

Model grids (.grd and .enc), elevations (.dep, m) and other XBeach-specific setup files (params, .dep, .grd, disch_loc_file, disch_timeseries_file, jonswap, loclist, waterlevelini) for tier 3 subregions (as described by O'Neill and others, 2024) are generated for Northern California. See Deltares manual (2024) for a description (and applicable units) of model files. Model domains are identified by sequential numbers, starting with ‘grid22’ at the southern end of Humboldt County and increasing northwards, to cover Humboldt County and portions of adjacent counties. Models are set up in the cartesian coordinate system (UTM 10) and elevations are referenced to NAVD88. Model grid/setup validated for storm system in January 2010 using boundary conditions from tier 2 simulations for the same period; water level RMSE is 14 cm at North Spit tide gage; domains without tide gages are compared to validated tier 2 output and adjacent overlapping domains. For an in-depth discussion of XBeach model setup see O'Neill and others (2018, 2024).

Model grids grid bathymetry adjusted for various SLR scenarios, based on corresponding projected cliff retreat and shoreline changes. Adjusted elevations are referenced to NAVD88. For an in-depth discussion of coastal elevation adjustment, see Erikson and others (2017) and O'Neill and others (2018 and 2024).

Setup files adjusted for all storm scenarios simulated in sub-regional tier 2 models. Water level and wave data were extracted from each tier 2 simulation to serve as boundary conditions for the XBeach model domains; additionally, the same discharge timeseries used in tier 2 simulations are used in XBeach simulations. XBeach models are set up and run for the same storm events used in tier 2 models, identified from future climate conditions (tier 2). For each event, setup files (water level, discharge and wave forcing files) are adjusted to use the extracted tier 2 boundary output as conditions; discharge estimates were synced to the onset of storm conditions, as in tier 2. For each storm event, simulations are run with a range of SLR: 0 m, 0.5 m, 1.0 m, 1.5 m, 2.0 m, 3.0 m, and 5.0 m. Model output was checked for quality and consistency. As done in tier 2 and described in O'Neill and others (2018, 2024), all simuliations are run over a representive spring tide in November 2010. All storm event conditions are synced to this representative tide cycle. See O'Neill and others (2018, 2024) on scenario setup and Erikson and others (2018) for information on storm selection.