thumb|Storm surge of the North Sea on February 9, 2014, as seen on the South Beach (Südstrand) in Wilhelmshaven, Germany.

A storm surge is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as tropical cyclones. Alternatively, it may be known as a storm flood, tidal surge, or storm tide. It is measured as the rise in water level above the normal tidal level, and does not include waves.

The main meteorological factor contributing to a storm surge is high-speed wind pushing water towards the coast over a long fetch. Other factors affecting storm surge severity include the shallowness and orientation of the water body in the storm path, the timing of tides, and the atmospheric pressure drop due to the storm.

As extreme weather becomes more intense and the sea level rises due to climate change, storm surges are expected to cause more risk to coastal populations. Communities and governments can adapt by building hard infrastructure, like flood barriers, soft infrastructure, like coastal dunes or mangroves, improving coastal construction practices and building social strategies such as early warning, education and evacuation plans.

For example, in Palm Beach on the southeast coast of Florida, the water depth reaches offshore, and out. This is relatively steep and deep; storm surge is not as great but the waves are larger compared to the west coast of Florida.

thumb|right|230px|[[Hurricane Ike storm surge damage in Gilchrist, Texas in 2008.]]

Extratropical storms

Similar to tropical cyclones, extratropical cyclones cause an offshore rise of water. However, unlike most tropical cyclone storm surges, extratropical cyclones can cause higher water levels across a large area for longer periods of time, depending on the system.

In North America, extratropical storm surges may occur on the Pacific and Alaska coasts, and north of 31°N on the Atlantic Coast. Coasts with sea ice may experience an "ice tsunami" causing significant damage inland. Extratropical storm surges may be possible further south for the Gulf coast mostly during the wintertime, when extratropical cyclones affect the coast, such as in the 1993 Storm of the Century.

November 9–13, 2009, marked a significant extratropical storm surge event on the United States east coast when the remnants of Hurricane Ida developed into a nor'easter off the southeast U.S. coast. During the event, winds from the east were present along the northern periphery of the low-pressure center for a number of days, forcing water into locations such as Chesapeake Bay. Water levels rose significantly and remained as high as above normal in numerous locations throughout the Chesapeake for a number of days as water was continually built-up inside the estuary from the onshore winds and freshwater rains flowing into the bay. In many locations, water levels were shy of records by only .

Measuring surge

Surge can be measured directly at coastal tidal stations as the difference between the forecast tide and the observed rise of water. Storm surge both destroys built infrastructure, like roads, and undermines foundations and building structures.

Additionally, storm surge can cause or transform human-utilized land through other processes, hurting soil fertility, increasing saltwater intrusion, hurting wildlife habitat, and spreading chemical or other contaminants from human storage.

A prophylactic method introduced after the North Sea flood of 1953 is the construction of dams and storm-surge barriers (flood 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; the Thames Barrier protecting London; and the Saint Petersburg Dam in Russia.

Another modern development (in use in the Netherlands) is the creation of housing communities at the edges of wetlands with floating structures, restrained in position by vertical pylons. or increasing natural protections like mangroves or dunes.

For mainland areas, storm surge is more of a threat when the storm strikes land from seaward, rather than approaching from landward. This phenomenon is known as a reverse storm surge, or a negative storm surge.

Historic storm surges

thumb|Elements of a storm tide at high tide

The deadliest storm surge on record was the 1970 Bhola cyclone, which killed up to 500,000 people in the area of the Bay of Bengal. The low-lying coast of the Bay of Bengal is particularly vulnerable to surges caused by tropical cyclones. and resulted in economic losses estimated at $14 billion (USD).

The 1900 Galveston hurricane, a Category 4 hurricane that struck Galveston, Texas, drove a devastating surge ashore; between 6,000 and 12,000 people died, making it the deadliest natural disaster ever to strike the United States. In the United States, one of the greatest recorded storm surges was generated by Hurricane Katrina on August 29, 2005, which produced a maximum storm surge of more than in southern Mississippi, with a storm surge height of in Pass Christian.

See also

  • Coastal flooding
  • Ishiguro Storm Surge Computer
  • Meteotsunami
  • Rogue wave
  • Tsunami-proof building

Notes

References

  • European Space Agency storm Surge Project home pages
  • from NIRAPAD disaster response organisation.
  • NOAA NWS National Hurricane Center storm surge page
  • DeltaWorks.Org North Sea Flood of 1953, includes images, video, and animations.
  • UK storm surge model outputs and real-time tide gauge information from the National Tidal and Sea Level Facility