St. Petersburg Coastal and Marine Science Center
Hurricanes and other extreme storms generate storm surge and large waves that erode the beach and dune system and reshape the coastal landscape. The impact of a storm on a barrier island is dependent not only on the physical processes at work during a storm but also on the elevation and shape of the beach during landfall. Sand dunes paralleling the shore act as the coast's first line of defense. Stretches of coast with very low dunes are potentially more susceptible during storms to extreme coastal change than those with higher dunes.
Vulnerability to coastal change during storms can be assessed using a model that compares the elevation of storm-induced water levels to local beach morphology. The model determines the probabilities of three types of coastal change:
The hydrodynamic forcing of the storm is represented as the extreme total water level (η98), which includes tide, storm surge and the 2% exceedance value of wave runup, and the storm-induced mean water level (η50) is defined as the sum of tide, storm surge and wave setup. To obtain forecasts of the likelihood of coastal change, the modeled water levels are required. These modeled water levels take on two forms (1) scenarios representing generic storm conditions and (2) near-real-time estimates using current weather and wave conditions. These values are then compared to measurements of the position and elevation of the dune crest (zc) and dune toe (zt) extracted from gridded lidar data.