Storm Surge

Hurricanes' Big Killer

Hurricanes are usually described in terms of their wind speeds, but flooding caused by the high water a storm brings, kills many more people than wind. Flooding, also is responsible for much of the damage, especially within a few hundred yards of the shoreline. Boats ripped from their moorings, utility poles, parts of destroyed buildings, and other debris crashing in the waves atop hurricane surge, often destroy buildings that stood up to the wind. Even without the weight of debris, water is a powerfully destructive force. A cubic foot of sea water weighs 64 pounds.

Water does more than batter, it scours away the sand of beaches and dunes and can also have an inpact on barrier islands. High water and pounding waves carry away the sand under sea walls, buildings, and roads. As the water begins rising sometimes hours in advance of the storm, it erodes the beach, the dunes and undercuts buildings behind the beach.

Storm surge isn’t a killer only along beaches facing the ocean; water is also pushed into bays and rivers. As the surge of water squeezes up a narrowing bay or river, it rises even higher.

What happens when the surge comes ashore..... The ultimate height of the “storm tide” is a combination of the astronomical tide and the storm surge. The surge normally does not arrive as a “wall of water,” but more like a quick rise in the tide to extremely high levels.

A 2-foot normal high tide plus a 10-foot storm surge will push the water 12 feet above mean sea level. A surge’s worst effect is to bring storm-whipped waves far inland; the battering of the waves causes far more damage than high water alone.

Hurricane protection levees have been built in many coastal communities, especially the New Orleans area, to protect life and property from storm surge. While these levees do a very good job in protecting communities during minimal hurricanes, sophisticated computer modeling of storm surge effects indicate most levees in southeast Louisiana would be overtopped from the storm surge generated by a direct strike by a major hurricane. The result would be widespread flooding.