Storm Surges

A storm surge is just what it sounds like: water that is pushed towards the shore by the force of the winds swirling around a cyclone (hurricane, storm). Storm surge can climb above 18 feet in height in a matter of minutes, travel far inland and flood vast areas of low-lying land.

Facts About Storm Surge

  • Storm surge is water that is pushed towards the shore by the force of the winds swirling around the centre of the storm. This, combined with the low pressure in the eye, creates a suction-like effect causing the level of the water to rise like a dome. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level 15 feet or more. In addition, wind driven waves are superimposed on the storm tide. This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tide;
  • The level of surge in a particular area is also determined by the slope of the sea floor. A gentle slope off the coast will allow a greater surge to flood coastal communities. Coastal areas where the sea floor drops off suddenly or the slope is very steep do not normally experience much storm surge flooding, although large breaking waves can still present major problems. Storm tides, waves, and currents in confined harbours severely damage ships, marinas, and pleasure boats;
  • Storm surge is associated with the eye of the cyclone, so if the eye makes landfall, that area will be exposed to storm surge;
  • The Saffir/Simpson Scale which classifies hurricanes and their strength also provides an indication of the mean sea level rise of storm surge. For a Category I hurricane the height is four to five feet; Category 2: six to eight feet; Category 3: nine to 12 feet; Category 4: 13 to 18 feet; and Category 5 is over 18 feet;
  • Because there is uncertainty about how intense the cyclone will be when it makes landfall, emergency managers plan for a storm surge one category higher than what is forecast;
  • Wave and current action associated with the surge also causes extensive damage. Water weighs approximately 1,700 pounds per cubic yard; extended pounding by frequent waves can demolish any structure not specifically designed to withstand such forces;
  • The currents created by the hurricane storm tide combine with the action of the waves to severely erode beaches and coastal highways. Many buildings withstand hurricane force winds until their foundations, undermined by erosion, are weakened and fail;
  • In coastal areas, wetlands, and rivers, intrusions of salt water endanger the public health and send animals, such as snakes, to flee from flooded areas and take refuge in urban areas. There can also be salt water intrusion in fresh water wells; when this happens pumping of water may be suspended;
  • In 1961 Hurricane Hattie made landfall in Belize City killing 264 people. The storm surge traveled five miles inland. Since then a new town has been built named Hattieville just outside of where the storm surged stopped. Today, Belize City, understanding the nature of storm surge, routinely evacuates the coastal area on the approach of a hurricane.

How Do You Know Whether Your Property is at Risk?

If your property is close to the coast and you have a “nice” bathing beach with a gently sloping shore and swimming water that is not deep or does not drop off suddenly, then chances are you could be affected by storm surge. Consult your development planning office to enquire whether they have a storm surge hazard map for your area. Talk to old timers to find out how far the sea normally travels in times of storms or hurricanes.

What To Do About It

Take action to reduce your risk and loss. This is called mitigation. Don’t leave it to fate, mitigate!

  • Before constructing your property near the coast, consult with the development planning office on the vulnerability and risk of this area to storm surge and the frequency of the event;
  • If your area is susceptible, consult with an engineer about what type of construction would be needed to withstand the worse case scenario;
  • The choice is then with you – either take a risk with the event or spend additional money upfront in construction to withstand the high waves;
  • If it is available, buy storm surge insurance;
  • If you are in a storm surge zone, then evacuate well ahead of the approach of a storm or hurricane.

For more information please contact:

Office of Disaster Management
Jimmit
Commonwealth of Dominica
Tel: (767) 448 7777
Fax: (767) 448 2883
E-mail: odm@dominica.gov.dm