Characteristics of Storm Surges
Figure 1. Storm surge along gently sloping (top) and steeply sloping shoreline (bottom). A larger surge occurs on the gently sloping shore; the steeply sloping shore has higher waves on top of the surge. The source of this material is the COMET© Website at http://meted.ucar.edu/ of the University Corporation for Atmospheric Research (UCAR), sponsored in part through cooperative agreement(s) with the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce (DOC). ®1997-2009 University Corporation for Atmospheric Research. All Rights Reserved.
- The highest surges usually occur to the right of the storm track (traveling with the storm) at approximately the radius of maximum wind.
- Fast moving storms cause high surges along open coast and lower surges in sheltered bays and estuaries.
- Slow moving storms usually result in greater flooding inside bays and estuaries, with smaller values along the open coast.
- Larger storms affect longer stretches of the coastline. A larger storm is defined as a storm having a greater radius of maximum wind.
- Storms with larger eyes create larger surges, up to an eye diameter of about 30 miles.
- The direction of storm approach often impacts the extent of flooding.
- Depending on location, storms from one direction may cause inundation, while a storm of the same magnitude from a different direction may cause little flooding.
- The slope of the near-shore seabed will affect the level of surge in a particular area. Areas with shallow continental shelf slopes will allow a greater storm surge, but have smaller waves. For example, on the Gulf Coast of Florida, the edge of the shallow water (depth less than 300 feet) "Floridan Plateau" lies more than 100 miles (160 km) offshore of Marco Island in Collier County. As a result, Marco Island can receive a storm surge of 22 - 24 feet in an west-to-east moving Category 5 hurricane.
- Areas with deep water just offshore experience large waves, but little stormsurge. Miami Beach, Florida is a good example of this. The maximum storm surge from a Category 5 hurricane is 8 feet, for a east-to-west moving storm. This is a factor of 3 to 4 less than the typical maximum surge possible elsewhere on the U.S. Atlantic Coast. The edge of the Floridan Plateau, where the water depths equal 300 feet, lies just 2 miles (3 km) offshore of Palm Beach, Florida. Just 4 miles (7 km) offshore, the depth plunges to over 180 meters.
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