Storm Surge and Surface Waves in a Shallow Lagoonal Estuary during the Crossing of a Hurricane

Tropical cyclones deliver intense winds that can generate some of the most severe surface wave and storm surge conditions in the coastal ocean. Hurricane Irene (2011) crossed a large, shallow lagoonal estuarine system in North Carolina, causing flooding and erosion of the adjacent low-lying coastal plain and barrier islands. This event provided an opportunity to improve understanding of the estuarine response to strong and rotating wind forcing. Observations from acoustic sensors in subestuaries and water-level elevation measurements from a network of pressure sensors across the system are presented. Data are examined with two modeling techniques: (1) a simple numerical approach using a momentum balance between the wind stress, flow acceleration, pressure gradient, and bottom friction that gives insight into temporal variability in water levels through the passage of the storm; and (2) an advanced hydrodynamic model based on the full shallow water fluid momentum equations, coupled to a spectral surface wave model that accounts for the spatially varying bathymetry and wind field. The results indicate that both wind-generated surface waves and the wind-driven storm surge are important contributors to the total water surface elevations that induce flooding along estuarine shorelines under strong hurricane forcing.