A localized rise in sea level produced by on-shore winds and reduced atmospheric pressure caused by large storms. Much of the flood damage produced by hurricanes, typhoons, and other major storms is the result of storm surge. Along the coasts of India and China these surges have resulted in death tolls of hundreds of thousands. One of the most devastating surges in recent history occurred in the North Sea during the winter of 1953, causing the sea level to rise more than 3 m/10 ft along the coast of The Netherlands.
Storm surge is caused primarily by high winds pushing on the ocean's surface. It is this combined effect of low pressure and persistent wind over a shallow water body which is the most common cause of storm surge flooding problems.Storm surges are particularly damaging when they occur at the time of a high tide, combining the effects of the surge and the tide. This increases the difficulty of predicting the magnitude of a storm surge since it requires weather forecasts to be accurate to within a few hours.
The most extreme storm surge events occur as a result of extreme weather systems, such as tropical cyclones, but storm surges can also be produced by less powerful storms.
The highest storm surge ever recorded was produced by the 1899 Cyclone Mahina, which caused a 13 meters (43 feet) storm surge at Bathurst Bay, Australia. In the United States, the greatest recorded storm surge was generated by 2005's Hurricane Katrina, which produced a storm surge 9 meters (30 feet) high in the town of Bay St. Louis, Mississippi, and in the surrounding coastal counties. The worst storm surge, in terms of loss of life, was the 1970 Bhola cyclone and in general the Bay of Bengal is particularly prone to tidal surges.
Hurricane storm surge; potential for disaster
Nine out of ten people who die in hurricanes are killed by storm surges. The Galveston Hurricane of 1900, a category 4 hurricane that struck Galveston, Texas on 8 September, drove a devastating surge ashore; The second deadliest natural disaster in the U.S. was the storm surge from Lake Okeechobee in the 1928 Okeechobee Hurricane which swept across the Florida Peninsula during the night of September 16. Only two years earlier, a storm surge from the Great Miami Hurricane of September 1926 broke through the small earthen dike rimming the lake's western shore, killing 150 people at Moore Haven (Will, 1978).
In the Bay of Bengal area, the "storm surge capital of the world", 142 moderate to severe storm surge events are on record from 1582 to 1991.
Mechanics of the storm surge
At least five processes can be involved in altering tide levels during storms.
Surge and wave heights on shore are affected by the configuration and bathymetry of the ocean bottom. A narrow shelf, or one that drops steeply from the shoreline and subsequently produces deep water in close proximity to the shoreline tends to produce a lower surge, but a higher and more powerful wave. These areas are subject to higher storm surges, but smaller waves.
This difference is because in deeper water, a surge can be dispersed down and away from the hurricane. However, upon entering a shallow, gently sloping shelf, the surge can not be dispersed away, but is driven ashore by the wind stresses of the hurricane.
Topography of the land surface is another important element in storm surge extent. Areas where the land lies less than a few meters above sea level are at particular risk from storm surge inundation.
Storm surge barriers
A prophylactic method introduced after the North Sea Flood of 1953 is the construction of dams and storm surge barriers. They are open and allow free passage but close when the land is under threat of a storm surge. Major storm surge barriers are the Oosterscheldekering and Maeslantkering in the Netherlands which are part of the Delta Works project.
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