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The Saffir-Simpson Hurricane Scale
The greatest potential for loss of life in coastal areas related to a hurricane is from the storm surge, which historically has claimed nine of ten victims.
Storm surge is simply water that is pushed toward the shore by the force of the winds swirling around the storm. 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 tides. Because much of the United States' densely populated Atlantic and Gulf Coast coastlines lie less than 10 feet above mean sea level, the danger from storm tides is
tremendous.
Communities with a steeper continental shelf will not see as much surge inundation, although large breaking waves can still present major problems. Storm tides, waves, and currents in confined harbors severely damage ships, marinas, and pleasure boats.
Storm Surge
An abnormal rise of sea along a shore as the result, primarily, of the winds from a storm.
These surge values are averages for these storm categories. Actual surge depths may be much greater.
Category 1: Minimal Damage
Winds: 74-95 mph
Along the South Carolina coast, surges of up to 4 to 5 feet can be expected.
No real damage to building structure. Damage primarily to unanchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier damage.
Category 2: Moderate Damage
Winds: 96-110 mph
Along the South Carolina coast, surges of up to 6 to 8 feet can be expected.
Some roofing material, door, and window damage to buildings. Considerable damage to shrubbery and trees with some trees blown down. Considerable damage to mobile homes, poorly constructed signs, and piers. Small craft in unprotected anchorages break moorings.
Category 3: Extensive Damage
Winds: 111-130 mph
Along the South Carolina coast, surges of up to 9 to 12 feet can be expected.
Some structural damage to small residences and utility buildings with a minor amount of curtainwall failure. Damage to shrubbery and trees with foilage blown off trees and large trees blown down. Mobile homes and poorly constructed signs are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by battering of floating debris.
Category 4: Extreme Damage
Winds: 131-155 mph
Along the South Carolina coast, surges of up to 13 to 18 feet can be expected.
More extensive curtainwall failures with some complete roof structure failures on small residences. Shrubs, trees and most signs are blown down. Complete destruction of mobile homes. Extensive damage to doors and windows. Major damage to lower floors of structures near the shore.
Category 5: Catastrophic Damage
Winds: More than 155 mph
Along the South Carolina coast, a surge higher than 18 feet can be expected.
Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Most shrubs, trees, and signs blown down. Complete destruction of mobile homes. Severe and extensive window and door damage. Massive evacuation of residential areas on low ground may be required.
