U.S. Geological Survey simulations of hydrodynamics and morphodynamics at Core Banks, NC, during Hurricane Dorian (2019)

The Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST v3.8; Warner and others, 2019; Warner and others, 2010) modeling system was used to simulate ocean circulation, water levels, and waves that occurred during Hurricane Dorian (2019) along the US East coast. Simulations were then further downscaled to focus on the resulting inundation, dune overtopping, and barrier island breaching during the storm along North Core Banks, NC. Simulations were performed with coupled and concurrent ocean and wave models simulated on a series of refined, cascading grids. The largest scale grids covered the entire US east coast (5km resolution), and subsequent grids downscaled to the Carolinas region (700m resolution), then to Pamlico Sound (250m resolution). Results on these grids were analyzed to investigate bay-scale dynamics of oceanic conditions. Results were further used to drive a coastal scale grid that stretched approximately 1.5 km in the alongshore and 4km in the cross-shore directions to cover a region of several breaches along North Core Banks.  This nearshore grid had cross-shore resolution that varied from 10 m to 2m across the barrier island and was 1.5m in the alongshore direction. Several simulations on this smallest scale grid were performed to investigate sediment grain size (coarse and fine) and effects of vegetation included or excluded yes vegetation and no vegetation) on the breaching processes.

Surface atmospheric forcings were obtained from the NOAA Rapid Refresh v4 (Dowell and others; https://rapidrefresh.noaa.gov/) atmospheric analysis and included surface winds, pressure, relative humidity, and air temperature at ~13 km spatial resolution. For the smallest grid, four simulations were performed: coarse sediment and yes vegetation (CSYV), coarse sediment no vegetation (CSNV), fine sediment and yes vegetation (FSYV), and fine sediment no vegetation (FSNV). The sediment on the seafloor was initialized with a uniform 10m thick distribution. The coarse sediment had an erosion rate of 0.050 kg/m2/s; mean grain size of 0.40 mm, settling velocity of 47 mm/s, and a 0.22 N/m2 critical threshold of erosion.  The fine sediment had an erosion rate of 0.025 kg/m2/s; mean grain size of 0.25 mm, settling velocity of 27 mm/s, and a 0.19 N/m2 critical threshold of erosion.

Simulations were performed on the larger grids for a time period from September 2, 2019 to September 7, 2019. The finer grid was simulated for the peak of the storm only, for the full day of September 06, 2019. Therefore, the first simulation is from September 2, 2019 to September 7, 2019 for Pamlico Sound using ROMS and SWAN. The second, third, fourth, and fifth simulations are on September 2, 2019 on the finest grid for the combinations of different sediment and vegetation:

1) U.S. Geological Survey simulations of hydrodynamics and morphodynamics at Core Banks, NC, during Hurricane Dorian (2019): Pamlico Sound.
2) U.S. Geological Survey simulations of hydrodynamics and morphodynamics at Core Banks, NC, during Hurricane Dorian (2019), North Core Banks, NC: Coarse Sediment No Vegetation (CSNV).
3) U.S. Geological Survey simulations of hydrodynamics and morphodynamics at Core Banks, NC, during Hurricane Dorian (2019), North Core Banks, NC: Coarse Sediment Yes Vegetation (CSYV).
4) U.S. Geological Survey simulations of hydrodynamics and morphodynamics at Core Banks, NC, during Hurricane Dorian (2019), North Core Banks, NC: Fine Sediment No Vegetation (FSNV).
5) U.S. Geological Survey simulations of hydrodynamics and morphodynamics at Core Banks, NC, during Hurricane Dorian (2019), North Core Banks, NC: Fine Sediment Yes Vegetation (FSYV).

Reference cited:

Dowell, D. C., Alexander, C.R., James, E.P., Weygandt, S.S., Benjamin, S.G., Manikin, G.S., Blake, B.T., Brown, J.M., Olson, J.B., Hu, M., Smirnova, T.G., Ladwig, T., Kenyon, J.S., Ahmadov, R., Turner, D.D., Duda, J.D., and Alcott, T.I., 2022, The High-Resolution Rapid Refresh (HRRR): An Hourly Updating Convection-Allowing Forecast Model. Part I: Motivation and System Description: Wea. Forecasting, 37, 1371–1395, https://doi.org/10.1175/WAF-D-21-0151.1.
 
Warner, J.C., Armstrong, Brandy, He, Ruoying, and Zambon, J.B., 2010, Development of a coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system: Ocean Modelling, v. 35, issue 3, p. 230-244.

Warner, J.C., Ganju, N.K., Sherwood, C.R., Kalra, T.S., Aretxabaleta, A., He, R., Zambon, J., and Kumar, N., 2019, Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System: U.S. Geological Survey Software Release, 23 April 2019, https://doi.org/10.5066/P9NQUAOW.