STORM SURGE

Storm surge in lower lying coastal areas is often the most extreme threat to life and property from a hurricane. If the passage of the hurricane coincides with high tides a storm surge can reach 20 foot above normal water level. If the coast is low the surge acts like a flooding river damaging structures and trees and drowning people, livestock, and wildlife.

The main factor affecting the height of the surge is the air pressure in the middle of the hurricane. The very low air pressure in the eye of the hurricane forms a raised mound of water. This comes ashore with the hurricanes eye, and is biggest in the eye and close by it.

The height of the surge also depends on the shape of the coastline, and the sea bed. A shallow sea bed increases the surge.

Adding to the destructive power of surge, battering waves may increase damage to buildings directly along the coast. The surge also lets waves move further inland.

Currents created by tides combine with the waves to can severely erode beaches and undermine the foundations of buildings. 

http://www.nhc.noaa.gov/surge/