South Carolina's low-lying topography, combined with its humid subtropical climate, makes it highly vulnerable to inland or riverine flooding. According to SCEMD, riverine flooding occurs when the flow of rainwater runoff is greater than the carrying capacities of the natural drainage systems. The largest riverine flood in South Carolina, based on the area affected, was the 1903 flood. Relentless rains associated with warm moist air and a low-pressure system caused this flood. Clifton and Pacolet were hardest hit. The Pacolet River rose as much as 40 feet in an hour, resulting in the deaths of 65 people.
Coastal flooding is usually the result of a severe weather system such as a tropical storm or hurricane, which contains an element of high winds. The damaging effects of coastal floods are caused by a combination of storm surge, wind, rain, erosion and battering by debris. In 1999, three tropical systems resulted in over 24 inches of rain in Horry County. The Waccamaw River and tributaries caused significant flooding throughout northeastern South Carolina.
The Federal Emergency Management Agency (FEMA) offers these facts on floods:
Floods are one of the most common hazards in the United States. Flood effects can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states.
However, all floods are not alike. Some floods develop slowly, sometimes over a period of days. But flash floods can develop quickly, sometimes in just a few minutes and without any visible signs of rain. Flash floods often have a dangerous wall of roaring water that carries rocks, mud, and other debris and can sweep away most things in its path. Overland flooding occurs outside a defined river or stream, such as when a levee is breached, but still can be destructive. Flooding can also occur when a dam breaks, producing effects similar to flash floods.
Be aware of flood hazards no matter where you live, but especially if you live in a low-lying area, near water or downstream from a dam. Even very small streams, gullies, creeks, culverts, dry streambeds, or low-lying ground that appear harmless in dry weather can flood. Every state is at risk from this hazard.
Familiarize yourself with these terms to help identify a flood hazard:
Flooding is possible. Tune in to NOAA Weather Radio, commercial radio, or television for information.
Flash Flood Watch:
Flash flooding is possible. Be prepared to move to higher ground; listen to NOAA Weather Radio, commercial radio, or television for information.
Flooding is occurring or will occur soon; if advised to evacuate, do so immediately.
Flash Flood Warning:
A flash flood is occurring; seek higher ground on foot immediately
To prepare for a flood, you should:
During a Flood
If a flood is likely in your area, you should:
If you must prepare to evacuate, you should do the following:
If you have to leave your home, remember these evacuation tips:
Driving Flood Facts
The following are important points to remember when driving in flood conditions:
The following are guidelines for the period following a flood: