Strategies for Back-Barrier Bay Total Water Level Estimation

Storm surge combined with tidal fluctuations and wave setup inundates low-elevation areas surrounding semi-enclosed bays, landward of barrier islands, resulting in hazards to coastal communities and ecosystems during extreme events. The USGS, in collaboration with NOAA, has developed a total water level (TWL) forecast that incorporates storm surge, tides, and wave setup and runup along the open-coast of the United States. As part of the extension to semi-enclosed bay waters, a set of strategies to adapt the TWL components to bays is developed. We combine observations, where available, with analytical and numerical models to determine the spatial characteristics of bay water level response to offshore forcing. The methodology takes advantage of the ADCIRC tidal database to expand the estimation to inland bay systems. The contribution of local wind setup is incorporated through an approach that considers wind speed, fetch, and relative bay-wind orientation. The contribution of waves to bay water level will be included by combining modeled climatological relationships between wind intensity and direction, and offshore swell and bay wave characteristics. The offshore, local and wave effects are combined to provide in-bay TWL distributions along the east coast of the United States. Spatially resolved total water level forecasts mitigate current flooding hazards and inform management decisions regarding future flooding hazards in inland coastal communities.