South Carolina is a state highly vulnerable to flooding. The state's low-lying topography and humid subtropical climate are prone to flooding, but there are also 8 major water sheds: Broad, Catawba, Edisto, Pee Dee, Salkehatchie, Saluda, and Savannah, all of which cover over 30,000 miles of waterways.
You can hide from the wind, but must run from the water.
Flooding can't just occur when it rains; it can also come from waterways overflowing and from storms over the ocean pushing water onshore. Flash floods often occur in highly populated cities due to urban development, which leaves fewer areas for water to drain. The more concrete there is, the more prone an area will be to flooding. It is important to avoid building in a flood-prone area unless you elevate and reinforce your home.
South Carolina's population has grown by 10.7% from 2010 to 2020.
It is expected to grow 22.4% by 2035. Also, by 2035, about 32% of its population is expected to live in coastal counties.
River flooding occurs when the water level overtops its banks due to excessive rainfall. River flooding can be especially tricky because it doesn't have to happen right where the heaviest precipitation fell; it can happen anywhere along the river.
Tides and nearby storms often cause coastal flooding. Tropical systems don't have to make landfall to cause major flooding. Often, a large tropical system or one moving slowly can cause significant flooding, leading to loss of life. Keep in mind that higher-than-normal tides can also cause coastal flooding, which often causes major headaches for those who live or transit along the coast. Coastal flooding is being exacerbated by sea level rise.
WHAT IS A 100-YEAR FLOOD?
A 100-year flood is a flood that has a 1% chance of occurring in any given year (a 1-in-100 chance). Similarly, a 500-year flood has a 0.5% annual chance. These terms describe the probability of a flood happening each year, not how often they occur. Flood depth projections for events like 100-year or 500-year floods show how deep flooding could be in certain areas if an event of that severity occurs.
To be best prepared before a flood occurs, you must be aware of any recent events that could make your area more prone to flooding. How are the levels of nearby rivers? If you are along the coast, could the high tides be higher due to the Moon-Earth-Sun alignment? Has it rained recently? How heavy? Even during a drought, you can be at risk of flash floods. As the soil becomes more compacted, it drains more slowly, allowing flooding to occur more easily. If you are at risk of flash flooding, it is best to head to high ground, even if the flood is not happening. Flash floods occur fast, often leaving little time to escape.
Average annual precipitation in South Carolina is about 47.6 inches. Extreme rainfall events from hurricanes or stalled storms are the main drivers of major floods.
It is important that you know your terminology.
A watch is often given well in advance, at least 12 hours before an event. A warning is an alert that an event is imminent or in progress. When in a warning and you are advised to evacuate, it is imperative that you follow orders.
Flooding tips:
- If you come to an area covered with water, it can be more profound than expected: Turn Around Don’t Drown®.
- Six inches of fast-moving water can knock adults off their feet and sweep them away.
- Twelve inches of moving water can carry off a small car.
- 18 to 24 inches of moving water can carry away larger vehicles, including
- Get to higher ground if you are in an area subject to flooding.
- Follow evacuation orders and heed warning signs.
- If you have time before you evacuate, disconnect utilities and appliances.
- Avoid floodwaters: It is NEVER safe to drive or walk through them. Live wires, sharp objects, and animals can be in the water. Floodwaters could be contaminated, exposing you to harmful or even deadly bacteria.
- Review your insurance policy. Flood coverage is not part of most homeowner, mobile home or renter’s
- insurance policies. There is a 30-day waiting period before coverage takes effect.
Flash flooding claims more than 140 deaths annually statewide, making it the deadliest thunderstorm-associated hazard.