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Hurricane Storm Surge Levels

The winds of hurricanes produce storm surges. The depth of water and geographic features of the coast where the surge occurs affect its level. Some conditions decrease the level, while others cause it to rise. Interpreting these factors to produce an accurate prediction of surge heights is important because of their destructive power.

Hurricane Related Storm Surges
- Although hurricane damage is more often associated with wind than with flooding, storm surges actually result in the most hurricane-related fatalities. Residents of shallow coastal areas are in the most danger, because these areas are where hurricanes gather maximum strength. Domes of water are lifted onto land by the strong winds located around the hurricane eye, causing instantaneous flooding.
Measurement of Levels
- The North American Vertical Datum of 1929 and 1988 measures the heights of local tides around North America. These measurements have been translated into tidal height predictions all along the coastal United States. These predictions are referred to as the astronomical tide. Using this benchmark, a storm surge level is produced from the difference between the astronomical and actual tide levels. If a storm tide occurs, its height is added to the actual tide level. A storm tide is formed when a hurricane moves over a rising tide. The wind from the hurricane enlarges the waves on top of the high tide, increasing the level of the surge.
Surge Level Prediction
- Storm surge levels are predicted for particular areas using the Slosh Model. The National Hurricane Center operates the computerized model. The model considers winds, air pressure, forward speed, size and track. Each prediction is tailored to the specific location in which the hypothetical hurricane would occur. However, the model can also be applied to predicted hurricanes if the model receives data 12 times over three days.
Increase and Decrease in Levels
- Shallow continental shelves result in larger storm surges. If the storm surge contains battering waves, which frequently collide with objects, the potential damage to people and property can be increased. Confined harbors amplify damage because of the concentration of boats, structures and people. If the storm surge occurs in coastal freshwater bodies, saltwater intrusion can occur, potentially turning the body into a salt marsh. Flora die and fauna move elsewhere.
  
  The strength of storm surges can be decreased as well. Inland forests reduce wave height and the velocity of the surge. Among the trees that provide this type of protection are mangroves, the branches of which are thickly tangled. Offshore barrier islands decrease the power of storm surges with the shallow water around their shores. Shallow water reduces velocity because storm surge velocity increases with depth.

Nature