Sources/Usage: Public Domain. View Media Details

The Total Water Level and Coastal Change Forecast (TWL&CC Forecast) provides coastal communities with 6-day notice of potential elevated water levels and coastal change (i.e., dune erosion, overwash, or inundation) on sandy beaches that threatens safety, infrastructure, or resources. This work assesses the skill of forecasts during a period of elevated water levels along the coast of North Carolina caused by Hurricane Isaias in August 2020, using a combination of observations and model hindcasts. Water levels and waves were observed throughout the storm at three locations near Wrightsville Beach, NC; a wave buoy offshore, a tide gage at a local pier, and a pressure sensor deployed at the pier. A wave resolving hydrodynamic model was forced with hourly wave energy to hindcast wave-induced water levels at the shoreline. The analyses demonstrated that water level observations at the pier were a useful proxy for total water levels at the shoreline (sum of tide, surge and wave runup) that are predicted by the TWL&CC Forecast. Wave-driven water levels accounted for 52 percent of the forecast TWL during the three peak hours of Isaias. The skill demonstrated (TWL bias = -0.54 meters) indicates that the forecasting system can provide fast and reliable predictions of TWL across hundreds of miles of coastline at sub-mile resolution, days to hours in advance of when storms threaten coastal regions.