Results of a storm surge - Orange Beach, Alabama. Image by USGS
What is a Storm Surge?
A storm surge occurs when powerful storm winds push water up onto the shoreline. This most frequently occurs when a hurricane makes landfall. Hurricanes are especially effective at producing a storm surge for these reasons:
1) Hurricanes have very poweful sustained winds that can reach over 100 miles per hour. These sustaned winds can push a lot of water towards the coastline. This water piles up, producing an elevated water level that is called a "storm surge".
2) Hurricanes are low pressure storms and that low pressure causes a rise in sea level beneath the storm.
3) Hurricanes dump a lot of rain. That rain and its associated runoff can add to water levels in coastal areas.
4) If a hurricane makes landfall while the tide is rising both the tide and the wind working together can make an especially high storm surge. This is sometimes referred to as a "storm tide".
5) The strong winds of the storm can generate large waves on top of the combined high tide and storm surge elevations.
Results of a storm surge - Orange Beach, Alabama. Image by USGS
How Dangerous are Storm Surges?
Storm surges are the most dangerous aspect of a hurricane. This is because they are capable of causing total inundation of entire coastal areas. A powerful hurricane can produce a storm surge of 15 feet or more. Since much of the the United States' densely populated Atlantic and Gulf Coast coastlines are less than 10 feet above sea level, the danger from storm surge is tremendous.
Storm Surges Can Wipe Out Entire Neighborhoods
The photos at right are from a storm surge produced by Hurricane Katrina's strike on Orange Beach, Alabama in 2005. Note the red arrows marking equivalent positions in the before and after images and the extensive damage in both images.
Predicting the Storm Surge Impact Area
Storm surge risk maps can be prepared by mapping low-elevation areas along the shoreline. Areas of highest storm surge inundation risk are low elevation areas along the coast and inland water routes. Lower risk areas are at higher elevations and/or farther inland.
