Storm surge pushing ocean water ashore during a hurricane
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Courtesy of US Navy and National Weather Service

Storm Surge

One of the most dangerous parts of a hurricane isnít the rain or the wind. Itís the flooding caused by storm surge.

As a hurricane or other tropical storm moves towards a coast, it can cause sea level to rise as much as 20 or 30 feet higher than normal. The sea level rise only lasts a short time, usually just a few hours, but it can cause a huge amount of damage. The rising water may totally submerge low-lying areas and towns along the coast. Huge ocean waves cause damage too, demolishing docks, houses, roads, and eroding beaches.

Most storm surge is caused when a stormís winds push ocean water towards the land. When the water is pushed into the shallow parts of the ocean, it piles up, flooding the coast. Some storm surge is caused by the low pressure of the storm too. When storm surge happens at high tide, there is even more flooding.

How much storm surge will a hurricane produce? Scientists use a computer model called SLOSH (Sea, Lake, and Overland Surges from Hurricanes) to try to predict how storm surge will affect a coast. Important factors that determine storm surge include the speed of winds in the storm, the distance that those winds travel over the ocean water, how the hurricane approaches the coast (whether it is a direct impact or at an angle) the shape of the coast and the shallow ocean bottom.

Last modified March 12, 2009 by Lisa Gardiner.

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