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South Carolina Flash Flood

The National Weather Service describes flash floods as the deadliest weather-related fatality in the United States, behind extreme heat. On average, the country experiences about 140 deaths and $6 billion in property damage yearly due to floods, many of which are attributable to flash flood incidents. Learning about the disaster and how to prepare for it can help South Carolina residents avoid or limit damages when one occurs.

What Is a Flash Flood?

A flash flood is the rapid flow of a large volume of water into an area following excessive rainfall, a dam or levee failure, or the collapse of an ice or debris jam. Unlike other kinds of floods, which may take days, or even weeks, flash floods occur within a short period, usually six hours or less after the event that triggers them.

They happen quickly with little or no warning and are far more disastrous than other types of floods. Due to their rapid rise and raging torrent, flash floods can sweep people and vehicles, destroy buildings and bridges, tear out trees, and move boulders. The 1979 collapse of the Machhu II dam in India, considered the worst flash flood incident ever recorded, wiped out an entire town and nearby villages, leading to about 3,000 deaths.

Areas prone to flash flooding include places around mountains and streams, urban areas, and low-lying areas. There is currently no method of classifying the magnitude of flash floods.

Flash Flood Science

Flash floods occur when there is far more water than the ground can absorb, resulting in excess water flowing quickly into low-lying areas. The flood overwhelms storm drains and ditches, causing the rapid release of significant amounts of water. Therefore, events that cause large water discharge within an area can lead to a flash flood. The most common of such events is heavy rain.

Flash floods can occur due to prolonged rainfall over several days or intense rainfall over a short period. Flood-causing rainfall usually results from the rapid movement of thunderstorms over an area or the occurrence of hurricanes or tropical storms. Other natural causes of flash floods include melting glaciers during volcanic eruptions and the collapse of ice or debris jams holding water.

Besides natural forces, certain human activities also cause flash floods. The failure or breakage of a dam or levee can result in the instant release of fast-moving water, capable of devastating anything in its path. An example of such an incident is the Johnstown Flood which killed 2,209 Pennsylvanians in 1889. Blocked or inadequate drainages in urban areas can also result in flash floods, as they are unable to collect excess water.

What Makes a Place Prone to Flash Floods?

In addition to incidents that cause the release of excess water, an area's geography and land use contribute significantly to its flash flood risk. For example, areas closer to water bodies are usually susceptible to flash floods. Places around mountains are also at risk because water flows faster along steep terrain which are common around mountains.

Likewise, urban areas are also at risk of flooding because concrete and asphalt surfaces prevent the ground from absorbing water, which leads to flood water runoff. Other conditions that affect the soil’s capacity to absorb water include oversaturation due to recent rainfall and ground hardening following a drought. Deforestation also contributes to flash flooding. Without vegetative cover to help retain water and slow runoff, excess water flows freely into water channels, overwhelming them and causing flash floods.

Flash floods can happen at any time of the year, but they are more likely to occur in late Spring through Summer. The melting of Winter snow, warmer temperatures, and frequent thunderstorms common during this period provides an ideal condition for the occurence of flash floods.

What Is the Impact of Flash Floods?

The impacts of flash floods are usually devastating for individuals and communities. Flash floods can result in loss of lives, severe injuries, as well as damage to individuals and the environment.

Injuries and Death

The most common cause of death during flash floods is drowning. Rapidly rising water can trap and drown people in buildings. Likewise, fast-moving floods can sweep away anyone in their path, resulting in fatalities. People may also sustain injuries from collisions with objects carried by flood water. Flash floods lead to more deaths yearly than other weather-related disasters in the United States— except extreme heat.Furthermore, the hardship experienced during the disaster may have adverse psychological effects on people in affected areas.

Damage to Property

Flash floods can also destroy or severely damage properties and belongings. Building damage may result from the force of the flood water or collision with heavy objects carried by the water, such as boulders. Nevertheless, even structures that survive the impact of flood water and debris may become susceptible to harmful molds.

Flood water can also destroy vehicles and possessions by sweeping or submerging them. Additionally, flood water can ruin farmlands, devastate livestock and wildlife, and cause extensive damage to essential infrastructures like roads, bridges, and utility lines. Such a level of destruction leads to the closure of businesses and loss of livelihoods.

Contaminated Food and Water

Flash flooding also has harmful effects on the nutrition and health of persons in affected areas. Flood water may carry chemicals and other hazardous substances that can contaminate groundwater, making tap water unfit for consumption. There is also usually an increase in the risk of waterborne diseases in flooded areas.

Lost Economic Growth

According to the National Weather Service, in 2021, the United States recorded 135 fatalities, 57 injuries, and an economic loss of about $2.5 billion due to flash floods. Flash flood impacts cause prolonged economic difficulties and population displacements in affected areas, bringing development to a standstill. Population displacement results in mass migration into nearby urban areas. Such a situation may cause overpopulation which significantly affects urban planning and development.

South Carolina Flash Flood Threat Profile

South Carolina is a coastal state located in the Southeastern region of the United States. As of 2020, it has a land area of 30,064.28 square miles and a population of 5,118,425. The State is highly vulnerable to flash floods because of its humid and subtropical climate, low-lying topography, and proximity to the Atlantic Ocean.

Almost all counties in the State have required a Presidential Disaster Declaration, at some point, due to severe floods. The Great Pacolet Flood of 1903, considered the deadliest flash flood in South Carolina’s history, led to the death of at least 65 people and caused economic damages of $5 million (close to $170 million in 2022 dollar value). Other notable historical flash floods that have occurred in the State include:

  • The Record Flood of 1908, with heavy rainfall over two days that led to the flooding of over 80 percent of the State.

  • Flash floods from the Southeast Hurricane of 1940 near Beaufort. The incident caused between 30 and 50 deaths, including an estimated economic loss of $10 million ($210 million in 2022 value)

  • The Homestead Hurricane of 1945 moved into eastern South Carolina from Florida, causing flooding that led to one death and the loss of properties and crops estimated at $7 million ($115 million in 2022 dollar value).

  • Statewide floods during Hurricane Klaus and Tropical Storm Marco in October 1990. The event affected central South Carolina mainly, leading to four deaths in Kershaw County and one in Spartanburg County. 13 counties in the state required disaster declarations due to the flood.

  • Flash floods occurred in October 2015, during the State’s historical floods, causing significant destruction in the Charleston tri-county area. The National Oceanic and Atmospheric Administration (NOAA) considers it one of the billion-dollar disaster events in the country.

Most Common Causes of Flash Floods in South Carolina

Hurricanes and tropical storms continue to be the most significant triggers of flash floods in South Carolina. There have been four major occurrences in recent times: Hurricane Joaquin (2015), Hurricane Matthew (2016), Hurricane Irma (2017), and Hurricane Florence (2018), resulting in 37 deaths and 1,634 homes damaged. South Carolina experiences a lot of rainfall between June and September, with August being the wettest month of the year.

What Are the Risk Factors for Flash Flood in South Carolina?

Learning about your area’s flash flood risk makes your preparation more informed and precise. Factors that generally contribute to an area's risk include weather conditions, topography, and land use.

Generally, areas around water bodies and places that experience frequent rainfall and storms are likely to have flooding events. When this is combined with steep terrain associated with mountainous and low-lying areas, the risk of flash floods increases significantly. Urban areas and places without vegetative cover are also at risk because there is little or nothing to break the flow of water and enhance the soil’s absorption of excess water.

You can contact your local authorities for location-specific flash flood risks. Each county in South Carolina maintains a list of areas within its jurisdiction that are prone to floods. Similarly, the Federal Emergency Management Agency (FEMA) provides a map of floodplains across the state. The National Weather Service also provides statewide forecasts for floods and other extreme weather, which can help residents determine their risks within a particular period. Residents can also contact their local National Weather Service customer service for information on flash flood risk and preparation tips.

Preparing for Flash Floods in South Carolina

Flash foods can occur at any time without any warning. But considering the following tips can help South Carolina residents ensure they are well prepared for flash floods, no matter when it happens.

Prepare Your Home:

  • Elevate and reinforce your home, as a significant portion of South Carolina’s land area is designated flood prone or floodplains.

  • Elevate and anchor electrical components and appliances, including electrical panels, propane tanks, sockets, wiring, and heating systems.

  • Install check valves for your sewer connections to prevent flood water from entering them.

  • Protect your basement walls with waterproofing materials to prevent flood water from seeping in. Also, consider installing a sump pump in the basement to remove excess water continuously. A battery-powered backup pump is also essential, as a flash flood can result in a power outage.

  • Clear drains and gutters around your home to reduce the risk of them getting blocked during a flood.

  • Construct a flood barrier to prevent water from entering your home. Ensure that the construction is in line with your locality’s building codes.

Prepare Your Family and Pets

  • Know your community’s emergency plans, flood alert signals, evacuation routes, and emergency shelters.

  • Develop an emergency response plan for your family and pets, and practice it periodically. This would ensure everyone knows how to protect themselves during a flash flood. The plan should consider various scenarios, including camping or hiking outdoors.

  • Avoid camping or parking close to flood-prone areas like streams, creeks, and rivers.

  • Inform local authorities about any special needs, such as elderly, bedridden people, or anyone with a disability.

  • Assemble an emergency kit containing essential supplies that would last for at least three days, including non-perishable food, water, and medicine. Also, make sure you include torches, a flashlight, a first aid kit, NOAA Weather Radio or any portable radio, sturdy shoes, and extra batteries and charging devices. Consider each person’s and pet’s needs when preparing emergency kits.

Prepare Your Property and Important Belongings

  • Protect important documents by keeping them in waterproof containers. If possible, consider keeping documents with trusted family or friends that do not reside in disaster-prone areas. You can also create digital copies of documents in preparation for the worst-case scenario.

  • Place valuable items at higher levels of your building.

  • Keep an inventory and pictures of your belongings in a safe place. They can come in handy when preparing insurance claims.

  • Always park your car in an elevated place if your vicinity is prone to flooding.

  • Always have sufficient gas in your vehicles in case an evacuation is necessary during an emergency.

Protect Your Finances

  • Purchase flood insurance for your home as homeowner’s policies do not usually include flooding. You can obtain flood insurance through the National Flood Insurance Program (NFIP). Comprehensive auto insurance would typically cover flood damage.

  • Create a savings plan for your emergency response. This ensures that you have some financial security when a flash flood occurs.

Look out for Flash Flood Warnings and Alerts

Flash flood warnings and alerts notify residents of a particular area of their flood risks. Preparing for a flood requires residents to be attentive to information about floods in their area. There are three types of flash flood alerts: a flood watch, a flood warning, and a flood advisory.

A flood watch is issued when an area is experiencing weather conditions that can result in a flood, such as thunderstorms. It is useful to keep residents alert and ready for the worst-case scenarios. In contrast, a flood warning signifies that a flash flood is imminent, and you should immediately commence your emergency response. When you receive a flash flood warning, there is little or no time, and your safety should be the paramount concern. Meanwhile, a flood advisory is issued if there is going to be a flood, but it is not severe enough to issue a warning.

Do not disregard a flood advisory, as relatively simple floods can become catastrophic for unprepared persons. In any case, always be alert, as flash floods often strike without any warning. Begin your emergency response once you get signs of a flash flood, such as dark skies, heavy, persistent rainfall, levee or dam failure, and a roaring sound accompanying the movement of water.

In South Carolina, flash flood alerts are coordinated and disseminated through the state’s Integrated Public Alert and Warning System (IPAWS). Under the IPAWS, federal, state, and local agencies are able to send emergency information to local television and radio and residents’ mobile phones.

Residents may also receive Wireless Emergency Alerts (WEAs), which are like short text messages designed to get people's attention with a unique sound and vibration. Additionally, residents are advised to get an NOAA Weather Radio which provides round-the-clock, weather updates for their vicinity.

Finally, the South Carolina Emergency Management Division uses CodeRED alerts to notify residents when a flash flood is imminent or has just happened. But you have to sign up to receive CodeRED notifications. Information required for the registration includes your first and last name, street address, city, state, zip code, and primary phone number. You can also include additional phone numbers.

What to Do During a Flash Flood in South Carolina

The following steps and tips can help South Carolina residents reduce their risk of fatalities during an unfolding flash flood.

  • Avoid walking or driving through moving floods. Just turn around and don’t drown; six inches of moving water can knock you off. Fast-moving water can also sweep away your vehicle. Instead, identify a higher ground and move there immediately. This tip also applies when a flash flood occurs while you are camping or hiking.

  • Stay away from bridges and power lines in flooded areas.

  • If you are trapped by water rapidly rising through your car, exit the car, get to the roof, and call for help.

  • If you get trapped in a building, move to the highest level and only climb to the roof if necessary. Call for help immediately when you climb to the roof.

  • Be attentive to local TV, radio stations, or internet alerts for specific instructions, including whether to evacuate and how to do so. If you are advised to evacuate, do so immediately before the water level rises. In addition, never drive around barricades, as local rescuers use them to control traffic during a flood.

  • Do not forget to pick up your emergency kits before evacuating.

  • If time permits, take in outdoor belongings or tie them down, move valuables to a higher level, and turn off utilities and appliances. But avoid touching electrical appliances if you are drenched or standing in water.

  • Arrange for the immediate evacuation of livestock if you have the slightest signal that a flood might occur.

  • Monitor your pets closely as they may get overly excited or frightened.

What to Do After a Flash Flood in South Carolina

Appropriate response after a flood is essential to address injuries and damages caused by the flood and ensure that secondary effects of the flood do not lead to further casualties. As such, take note of the following tips on what and what not to do after you experience a flash flood in South Carolina.

Get Treatment for Injuries

  • Check for injuries and apply first aid treatment to them. Call 911 if there is a medical emergency.

  • Ensure open injuries do not come in contact with flood water. Water from flash floods are usually contaminated with dangerous substances, including sewage, bacteria, and harmful chemicals.

Assess the Damage to Your Property

  • Do not return to your building until local authorities confirm that it is safe.

  • Take pictures and videos of your damaged home and properties in preparation to make an insurance claim. Ensure that you contact your insurance agent and file your claim as soon as possible.

  • Contact a licensed electrician and plumber to assess the damage done to your utility systems.

  • Contact a building contractor to assess your home’s structure and conduct necessary repairs. Note that construction after a flood may require special local permits. Ensure that your contractor obtains such permits before proceeding with the repairs.

Clean Up the House

  • Beware of electrocution. Stay away from downed wires, and do not touch electrical appliances when wet or standing in water. Turn off your electricity if you were not able to before the flood hit.

  • Clean and disinfect items that came in contact with flood water. Discard items that you cannot clean, including items that absorb water, such as carpets, mattresses, and stuffed toys.

  • When cleaning after a flood, wear protective outfits, including thick gloves, sturdy boots, and long clothes. And do not let children join you in cleaning.

  • Beware of animals flushed into your house by the flood, especially snakes.

Get Clean Water and Food

  • Avoid drinking tap water until local officers have confirmed that it is safe to do so.

  • Discard food items that have come in contact with flood water.

  • Do not drive or go out except when it is absolutely necessary. Floods can destroy roads, and there might be sharp debris in the water that you might not see.

Get Local and Federal Aid

Apply for post-disaster assistance provided by the Federal Environmental Management Agency (FEMA) following a Presidential Disaster Declaration. A presidential declaration is usually made when a disaster causes large-scale destruction and affected communities require more assistance that they can gather locally.

Aids that accompany a disaster declaration includes nutritional, debris cleanup, and accommodation assistance. They are usually provided by FEMA in collaboration with state and local governments. Also, look out for tax reliefs and exemptions granted to victims of floods in the state.