Storm Surge

Graphic showing the different heights of storm surges.

Characteristics


Storm surge is an abnormal rise in water generated by a storm. This is over and above the predicted astronomical tide. Storm surge is sometimes confused with storm tide. Storm tide is defined as the water level rise due to the combination of storm surge and astronomical tide (thus it is an accumulative level).

Storm surge can cause significant flooding particularly when it occurs in relation to normal high tide.

Dangers


Along the coast, storm surge is often the greatest threat to life and property from a hurricane. In the past, large death tolls have resulted from the rise of the ocean associated with many of the major hurricanes that have made landfall.

Hurricane Katrina in 2005 is a prime example of the damage and devastation that can be caused by surge. At least 1500 persons lost their lives during Katrina and many of those deaths occurred directly, or indirectly, as a result of storm surge.

Storm Development


Storm surge is produced when water is pushed toward the shore by the forces of winds moving cyclonically around a storm. The impacts of low barometric pressures are minimal on surge when compared to the wind driven forces. The maximal storm surge for any given area is complex as it can be affected by:
  • Angle of approach
  • Central pressures
  • Forward speed
  • Radius of maximum winds
  • Shape and characteristics of coastline features
  • Slight changes in storm intensity
A shallow slope has the potential for a great more intense storm surge to develop than sharp steep slope. Storm surge will inundate coastal floodplains by dune over wash, tidal elevation rise in inland bays and backwater flooding through coastal river mouths.

Occurrence


The storm surge arrives ahead of the storm center's actual landfall and the more intense the storm is, the sooner the surge arrives. Water rise can be very rapid, posing a serious threat to those who have not yet evacuated flood‐prone areas.

The surge is always highest in the right‐front quadrant of the direction in which the storm is moving. As the storm approaches shore, the greatest storm surge will be to the north of the low‐pressure system or hurricane eye. Such a surge of high water topped by driven by hurricane force winds can be devastating to coastal regions, causing severe beach erosion and property damage along the immediate shoreline.

Storm Surge Safety

  1. Before
  2. During

Before a storm surge


Preparing for a storm surge


  • Check your house and land for any potential dangers related to flooding. Identify any vulnerability and repair it.
  • Sandbags are a valuable tool to prevent water from entering your home. This approach requires specific instructions from your local emergency officials.
  • Learn how to turn off the gas and electricity in your house. You may be instructed by local authorities to shut these off.
  • If you live in an area that is subject to flooding, do not store your important documents in the basement. Keep them at a higher level, protected from flood damage.
  • Ensure that your family has an emergency kit and plan.
  • Ensure your emergency kit is portable, in a back-pack or suitcase with wheels.
  • Your local Red Cross can teach you survival techniques in the water through their swimming and boating courses.

If a storm surge is forecast


  • Check supplies including medications, radio, flashlight and batteries.
  • You may have to evacuate. Keep your emergency kit close at hand.
  • Make sure the basement windows are closed.
  • Fuel your car. If evacuation becomes necessary, it will be hard to stop for gas.
  • If you have any questions or need to know more about evacuation procedures, contact your local emergency management organization, or police or fire department.

Additional Resources



Want to learn more about storm surge and storm surge safety? Visit these sites for additional information: