CoSMoS 3.2 Northern California sub-regional tier 2 FLOW-WAVE model input files

Model grids (.grd and .enc), elevations (.dep, m) and other Delf3D-specific setup files (.ddb, .url, .fil, .mdf., .mdw, .src, .dis, .bnd, .bct, .bcw, and meteo files) for tier 2 subregions (as described by O'Neill and others, 2018) are generated for Northern California. See Deltares Manuals (2018a and 2018b) for a description (and applicable units) of model files. Models are identified by a 2-letter designation (in runid files) and cover 4 areas of interest: 'de' covers Del Norte County, 'hu' covers Humboldt Bay, 'lc' covers Cape Mendocino, and 'me' covers most of Mendocino County north of Pt. Arena. 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 reanalysis wind/pressure fields over California (Kanamitsu and Kanamaru, 2007). For sub-regions covering areas with tide gages (de, hu, me), water level RMSE is 13 cm, 9 cm, and 9 cm, respectively; sub-regions without tide gages (lc) are compared to validated Tier 1 output and match output with RMSE of 7 cm. Similarly, sub-regions with buoy observations (hb and de) have wave height RMSE 13 cm and 55 cm (respectively). Of note, inspection of reanalysis wind fields (Kanamitsu and Kanamaru, 2007) indicate the January 2010 storm is not represented as accurately in this focing dataset in the northernmost sections of the region as other areas of this Northern California study. Sub-regions without buoy observations (lc and me) are compared to validated Tier 1 output and match output with RMSE of 38 cm and 28 cm (respectively). For an in-depth discussion of tier 2 model setup see O'Neill and others (2018).

Identified peak discharges for rivers of interest for storm scenarios simulated in regional Tier 1 model, using methods described by O'Neill and others (2018). For Northern California, associated precipitation data from the same Global Climate Model were used to determine relationships to discharge (in lieu of using maximum SLP gradients). Relationships were identified using log-linear curves, rather than linear trends, for rivers with high correlation of extreme storm runoff estimates to neighboring rivers and creeks (O'Neill and others, 2018). Peak discharges for 'parent' rivers (Audobon Creek, Walker Creek, Big River, Noyo River, Ten Mile River, Elk River, and Little River) were scaled to associated 'child' rivers by watershed area (O'Neill and others, 2018) and included in model setup files (.dis, m3/s).

Setup files adjusted for all storm scenarios simulated in regional Tier 1 model. Water level and wave data were extracted from each Tier 1 simulation to serve as boundary conditions for the sub-regional model. Storm events identified from future climate conditions (TWL proxies) that were simulated are: 3 May 2031 (no storm); 9 February 2020, 10 December 2071, and 19 October 2058 (1-year storm); 9 February 2074, 10 December 2052, and 15 December 2063 (20-year storm); and 8 December 2023, 27 November 2056, 5 March 2044, and 23 December 2083 (100-year storm). For each event, setup files (wind, sea-level pressure, water level, discharge and wave forcing files) are adjusted to use the extracted Tier 1 boundary conditions; discharge estimates were synced to the onset of storm conditions. 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. As done in Tier 1 and described in O'Neill and others (2018), 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) on scenario setup and Erikson and others (2018) for information on storm selection.