Flood Forecasting for Back-Barrier Estuaries: Critical Sensitivity to Local Wind Stress

Millions of Americans and hundreds of billions of dollars in property are situated on back-barrier estuaries (BBEs), and these locations are highly susceptible to flooding due to low-lying property and sea level rise. Wind stress on BBEs can have an important supporting role in this flood risk, due to the high efficacy of winds blowing over shallow water for causing storm surge. A variety of wind drag coefficient parameterizations are available for coastal ocean and estuary modeling, but these were all developed using data from relatively deepwater, usually open-ocean sites. An improved understanding and accurate representation of wind forcing effects on these systems is a critical starting point for moving flood forecasting systems forward. Barnegat Bay is a shallow (mean H=1.6 m), narrow (70 km long, ~4 km wide), highly developed BBE system where average damages from coastal flood hazards over the coming 50 years are expected to be over $450 million per year. Here, we first apply observations to assess the importance of different forcing factors including rain, tide, wind, and coastal daily-to-monthly sea level variability. Second, we apply idealized modeling of different bay sizes and inlet locations to demonstrate the sensitivity of storm-driven flooding to wind stress and its uncertainty. Results are compared with a prior study’s analytical modeling approach, demonstrating their consistency and extensibility to any BBE. These results motivate a detailed campaign of measurements and modeling to improve our understanding of wind stress on BBEs.