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Flash Floods in Louisiana

A flood is a natural disaster that occurs when an overflow of water submerges what is normally dry land or area. It is often caused by heavy rainfall, overflowing rivers, ruptured dams, rapid snow or ice melting, and storm surges arising from tropical cyclones or tsunamis. Floods are the most common environmental hazards and can occur anywhere, including both coastal and inland areas. Whenever flooding happens, there is often loss of life and enormous property damage. This is because floods have massive destructive power and can pick up large objects including trees, cars, houses, bridges, and even people.

Flash Flood Introduction

Flash flooding is the most dangerous type of flood because of its destructive power and incredible speed. It occurs when there is a sudden rush of water over dry land, usually resulting from excessive rainfall, dam breakage, or rapid snow thaw. This type of flooding begins within six hours of intense rainfall and often happens due to severe thunderstorms, hurricanes, or any other weather event. Flash floods differ from other types of floods such as river floods, coastal floods, and inland floods. The differences between flash floods and these other kinds of floods can be seen as follows:

  • Flash Floods vs. River Floods: Flash flooding arises when fast-moving waters submerge usually dry land or area. River floods, on the other hand, occur when a riverbank or stream gradually overflows and exceeds its capacity due to persistent rainfall, snow melt, or ice jams. Unlike a flash flood which arises rapidly and without warning, river flooding occurs slowly. It is therefore easy for people to still find time to prepare and evacuate to a safer place when river floods occur. This type of flood therefore rarely leads to loss of life but can cause significant property damage.

  • Flash Floods vs. Coastal Floods: While both flash floods and coastal floods generally arise when large quantities of water submerge dry land, coastal floods are particularly known to occur in areas that lie on the coast of a sea, ocean, or other large body of open water. Also, several factors may cause a flash flood such as prolonged rainfall, levee failure, and rapid snow melt. On the other hand, coastal flooding is primarily caused by extreme weather and storm surges associated with tropical cyclones, tsunamis, and heavy sea tides.

  • Flash Floods vs. Inland Floods: Although flash floods and inland floods are sometimes used interchangeably, they have a few differences. Generally, inland flooding happens when water exceeds the capacity of natural and built drainage systems. The term covers all types of flooding that occur in inland areas, including flash floods. Hence, while inland flooding may develop slowly or suddenly depending on the intensity of rainfall and other factors, flash floods are known to occur within hours and without any form of warning.

Flooding occurs in every state in the U.S. and is a threat anywhere in the world that experiences rainfall. In the U.S., flash floods remain the most destructive weather phenomenon that kills more people annually than lightning, hurricanes, and tornadoes. This is confirmed by the National Weather Service (NWS) data which reported that the national 30-year average for flood deaths in the U.S. is 88. This is in contrast with a 30-year average of 41 deaths from lightning, 45 from hurricanes, and 68 from tornadoes. The report further indicates that nearly half of all flash flood fatalities in the U.S. are vehicle-related. The majority of victims are males, and flood deaths affect all age groups.

Flash Flood Science

Flash flooding is rapid flooding that occurs in a short time frame generally within six hours after an intense storm or heavy rainfall. This type of flood is not only caused by excessive rainfall, but can also be caused by dam or levee failures, snowmelt, and ice jams. According to the National Oceanic and Atmospheric Administration (NOAA), most flash floods are caused by slow-moving thunderstorms, heavy rains from hurricanes, and tropical storms. Other factors that may contribute to the occurrence of flash flooding include the topography and land use of the region, the soil conditions, vegetation cover, and density.

Low-lying areas and steep topographies are prone to flash floods, irrespective of whether it is an urban or rural setting. This is because these areas are characterized by shallow soil depths above solid bedrock that prevent the soil from absorbing rain. Flash flooding is however more likely to occur in urbanized areas than in rural settings, since the former promotes runoff of rainfall and snowmelt, rather than allowing the rain to be absorbed into the ground.

Flash Flood Impacts

Flash flooding occurs at any time of the year and happens so quickly that it catches people by surprise. The rapid rising of flood water, therefore, makes it the deadliest weather condition in the U.S. after heat-related deaths. When the water rises suddenly and very quickly, it traps people in their homes or offices and can lead to massive loss of lives and destruction of properties. Flood victims and their family members suffer from extreme economic losses and psychological impacts due to the death of a loved one, loss of livelihoods, or displacement from their homes.

In addition, the force of flash floods can rip trees from the ground, wash away cars, sweep people off their feet, and destroy bridges and houses. Most flash flood fatalities are caused by drowning, or traumatic injuries resulting from being carried along in the water or swept into a stationary object. Flash flooding also destroys plants in the area and drowns many animals including pets, farm animals, and wildlife. It causes the runoff of pollutants into water bodies like rivers and streams and increases rapid soil erosion in substantial amounts.

Flood waters can also cause structural damage to communications and public infrastructure such as bridges, roadways, power, telephone, and cable lines. This natural disaster ultimately disrupts economic activities and results in the loss of livelihoods, reduction in purchasing power, and loss of land value. The huge economic impacts of flash flooding also cause mass migration or population displacement. Mass migration to cities ends up contributing to overcrowding and causes even more complex social problems in urban areas.

Louisiana Flash Flood Threat Profile

Located along the southernmost part of the Mississippi River Basin, Louisiana has experienced many catastrophic flash floods with heavy rainfall and thunderstorms over the years. The state is particularly vulnerable to flash floods because much of New Orleans and other populated areas sit below sea level. These areas are protected by levees and pumping systems that prevent rainwater from absorbing into the ground. According to the U.S. Environmental Protection Agency (EPA), changing climate and heavy rainstorms are likely to increase the risk of flooding in Louisiana. Flooding in Louisiana may result from weather conditions such as thunderstorms, hurricanes, storm surges, or infrastructure failures like dams, levees, and floodwalls. Louisiana can have high rainfall from varied weather patterns seasonally. During summer seasons, the state generally experiences heavy rainfall that results in flash flooding. In cooler months, heavy streamflow that produces river floods is common in the state.

Over the years, Louisiana has recorded many flash floods resulting in human casualties and economic losses. Between 1980 and 2009, the state reported an average of 91 flood-related deaths per year. Furthermore, Louisiana experiences more deaths due to flash floods than any other thunderstorm-related weather event such as hurricanes and tornadoes. Some of the historic flash flood threats in Louisiana include:

  • Great Mississippi Flood of 1927: This is considered one of the worst natural disasters in U.S. history. The flood submerged more than 23,000 square miles (60,000 square km) of land, killing 246 people and causing over 700,000 displacements. Aside from Louisiana, other states such as Mississippi, Texas, Missouri, Indiana, Illinois, Kansas, Tennessee, Kentucky, Oklahoma, and Arkansas were greatly affected by the natural disaster. Property damage was estimated to be over $400 million, which is equivalent to over $5 billion today. Furthermore, over 20 Parishes situated in southeastern Louisiana, including St. Bernard and Plaquemines Parishes experienced serious flooding and property damage.

  • Mississippi flood of 1973 (March to May): This flood occurred around the lower Mississippi River in Louisiana and other states like Mississippi, Arkansas, Missouri, and Tennessee. It is ranked the third most severe flooding out of the seven largest floods on the Mississippi River between 1927 and 1997. Louisiana and other Mississippi Valley states incurred more than $250 million in damages as a result of the flood.

  • Mississippi Flood of 1983 (May and June): This is ranked the second most destructive flood since the Great Mississippi Flood of 1927. Red River Landing in Pointe Coupee Parish experienced serious flooding for 115 days. Property damage was estimated to be $15.7 million.

  • The May 1995 Floods: Louisiana and southern Mississippi experienced severe floods on May 8 to 10, 1995. The flood resulted in six fatalities and $3.1 billion in damage. The entire New Orleans metropolitan area recorded $360 million in damages, and about 56,000 homes were destroyed in 12 Parishes. The flooding is known to be destructive and costlier than the Easter Floods of 1979 and the Floods of 1989 combined.

  • Mississippi River Flood (23 April to 7 May 2011): This flooding submerged thousands of square miles of agricultural and residential land in the central parts of the U.S. It led to approximately 20 fatalities in several states, including Louisiana, Arkansas, Missouri, and Ohio. Property damage accounted for about $2 to $4 billion as of 2011. There was widespread displacement and several environmental impacts, particularly on the fishing and farming sectors.

  • Louisiana floods of 2015: This took place in June 2015 after the Red River at Shreveport reached record levels and caused serious flooding in the state. The flood affected Louisiana communities like Rapides Parish, Caddo Parish, Natchitoches Parish, Bossier Parish, and cities like Shreveport, Alexandria, and Coushatta.

  • Louisiana floods of 2016: This flooding occurred in August 2016 due to prolonged rainfall across southern Louisiana. Many rivers and waterways reached record levels and the flash flood caused serious property damage across multiple parishes in southeastern Louisiana. The flooding killed 13 people and destroyed about 50,000 to 75,000 structures. Property damage was estimated to be within $10 to $15 billion.

Preparing for Flash Flood in Louisiana

Flash floods can occur suddenly without any warning and can catch people off guard. Where this happens, it is important to take note of the following safety tips when preparing for a flash flood in Louisiana:

  • Check the media for emergency information and updates: It is essential to stay informed about the possibility of a flash flood threat by paying close attention to weather forecasts, warnings, and public safety information before, during, and after the flood.

  • Know if your home/business/school is a flood-prone or high-risk area: This is one of the first steps to take when preparing for a flash flood in Louisiana. Check flood maps to see if you reside in an area prone to flash floods or any other type of flooding. Since you may not be at home during the occurrence of a flash flood, it is also necessary to find out if your office, school, or any other place you frequently visit is a flood zone.

  • Create a flood disaster family plan: Once you discover that your home is in a flood zone, create a family emergency plan and ensure you find out about the flood evacuation routes in your area. You should always be prepared to evacuate if you live in a flood-prone area.

  • Assemble an emergency kit: Your flood emergency kit should have enough food, water, and medicine to last you for days. Since electricity and water service may be interrupted, you would have to take this into account when packing your emergency kit. Make sure to pack a First Aid kit, flashlights, blankets, duct tape, rubber boots, rubber gloves, NOAA Weather Radio, batteries, multi-purpose tools, and other items of important use during an emergency.

  • Minimize your financial burden by getting flood insurance: Since flood losses are not covered under standard home insurance policies, it is important to purchase flood insurance by reaching out to your insurance company. This should be done as early as possible and before a flash flood threat, to ensure that you meet the 30-day waiting period for the insurance policy to take effect.

  • Make a list of your personal property: It is important to make a record of your personal property such as clothing and valuables by either taking photos or videos of them and keeping these records in a safe place.

  • Prepare your home: Where there is sufficient time, use sandbags, plastic sheeting, plywood, or other materials to protect your home from flood waters. Ask a professional to install check valves in plumbing to prevent flood waters from entering the drains of your home. In addition, make sure all electrical appliances are unplugged and move important items from the lowest parts of the home to avoid water damage. Also, ensure to construct barriers such as levees and floodwalls to prevent flood waters from entering your home.

  • Prepare your family and pets: Since you may end up evacuating, prepare and review the evacuation plan for your family and pets. Ensure your family members have a way of contacting each other if separated during an emergency.

  • Evacuate: It is important to evacuate as soon as possible if it is likely that your home will be flooded. Make sure to know the evacuation routes in your area. You should have alternative plans for a place to stay or consider staying with a local emergency shelter.

Flash Flood Warnings and Alerts

In Louisiana, the NWS issues flood alerts, watches, and warnings based on precipitation (rain) forecasts. These weather statements help the public to know about the severity of an imminent or occurring flood, and provide them the opportunity to prepare for such a disaster. Some of the specific flash flood warnings and alerts issued in Louisiana include:

  • Flood Watch: This is issued when conditions are favorable for flooding to occur. It does not mean flooding will occur, but it is possible. This type of flash flood alert, therefore, helps to keep people prepared in case a disaster eventually occurs.

  • Flood Warning: This is the most serious weather alert issued by the NWS. This alert is sent out when there is a severe threat to human life from a flash flood and catastrophic damage is imminent or already occurring. A flash flood can arise so quickly that there is little or no time to issue a flood warning. This type of flood alert, therefore, urges people to take immediate steps to keep themselves and their families safe. People who live in flood zones would have to pay close attention to the water levels in their area and move to higher ground if those levels start to increase.

  • Flood Advisory: This is the mildest kind of flash flood alert in Louisiana. It is issued when minor or nuisance flooding is imminent or already occurring. This means that a flood may arise due to a problematic weather condition, but the flooding is expected to be less severe if it occurs. Even in this situation, people should take critical safety steps because such flooding may end up becoming more serious and pose a risk to life and property.

In addition, Louisiana uses a flash flood advanced warning system such as the NOAA Weather Radio and the Emergency Alert System (EAS) which provides public warnings in cases of emergencies through radio and television broadcasters, cable TV, wireless cable systems, satellite, and wireline operators. There is also the Integrated Public Alert and Warning System (IPAWS) which is an advanced warning system used to provide the earliest warning about whether to expect a flood, when the flood will occur and how severe it will be.

The Governor's Office of Homeland Security and Emergency Preparedness (GOHSEP) uses IPAWS to ensure that Louisiana residents have the information and resources they need during a storm. A good example of an IPAWS channel used by GOHSEP during an emergency is Rave Alert. This is a mass notification system used by governments, organizations, and schools, to send out messages in just three clicks. The system, therefore, allows public safety officials to easily and quickly send out alerts across multiple modes of communication.

Flash Flood Risk Factors

Louisiana is particularly prone to flooding because it lies on low-lying marshes where the soil saturates quickly during heavy rainfalls. Some of the risk factors associated with flash floods in Louisiana include precipitation, topography, soil texture, vegetation, and seasonality. Flash flooding may also occur due to other factors such as urbanization and land use arising from agricultural and forestry activities that may accelerate soil erosion.

It is important to view flood maps to determine whether your home or business is a high, moderate, or low flooding risk area. The information provided in the flood maps helps to determine where you can seek shelter if a flash flood occurs in your area. The Federal Emergency Management Agency (FEMA)'s Flood Insurance Rate Maps is a good example of a flood map.

When Caught in a Flash Flood

Even after all the preparations made, it is possible to still get caught in a flash flood, particularly the type that occurs suddenly and without warning. Consider the following safety tips if caught in a flash flood at home:

  • Move to higher ground immediately: If your home is in a low-lying area, you should move to higher ground immediately and stay put. Avoid moving to an enclosed space because you may end up becoming trapped by rising flood waters.

  • Do not hesitate to follow an evacuation order: Once a mandatory evacuation order is issued in your area, it is essential to take them seriously and follow every instruction given. Do not wait till the flooding begins before you take action to evacuate because it may already be too late.

  • Avoid contact with floodwater: It is best to avoid any form of contact with flood waters that enter your home. This is because such waters may have been contaminated with sewage or contain dangerous insects or animals. In addition, avoid touching flooded gas or electrical equipment, and stay away from rooms where electrical outlets have been submerged in flood water. You may end up suffering from electrical shock if you do not.

  • Continue to check the media for updates: Ensure you continue to listen to local radio or television for emergency information. This will keep you informed about the ongoing situation and help you determine the next steps to take to keep yourself and your family safe.

If you get caught in a flash flood in your vehicle, take note of the following safety tips:

  • Do not drive through floodwater: It is dangerous to drive through floodwaters because your vehicle can be swept away in just two feet of fast-flowing waters.

  • Stay in the vehicle if trapped in rapidly moving water: Avoid exiting the vehicle if surrounded by fast-moving waters. This should only be done if the water is rising inside your vehicle. Where this happens, get out of the car and seek refuge on the roof.

  • Avoid driving around barricades: If you come across barriers on a flooded road, back up and find an alternative route. Avoid driving around such barriers for your safety.

  • Do not drive on bridges during a flash flood: Flash floods can wash out large objects such as bridges. It is therefore important to avoid driving on a bridge under which floodwater is rapidly moving.

Other general safety tips to consider include:

  • Avoid walking or swimming through flowing water. You may end up drowning since only six inches of rapidly moving water can knock you over.

  • Avoid walking on beaches or riverbanks during flash floods.

  • When stranded on a surface out of reach of floodwaters such as a tree or rooftop, stay put until rescue comes.

  • Keep children and pets away from flood waters.

  • Avoid entering flood water because of the risk of contamination with sewage, or contact with dangerous animals.

  • Avoid areas such as low spots, canyons, and underpasses that can easily become flooded.

  • Whenever in doubt of your safety, remember to turn around, don't drown.

After the Flood

Even after a flood, there are certain precautions to take for your safety. Some of these include:

  • Return only after being asked to: You might decide to return to your home or office immediately after flood waters recede. However, it is important to stay where you are until the local authorities say it is safe for you to leave.

  • Continue to receive updates from the media: Keep listening to NOAA Weather Radio for emergency information and other updates.

  • Check on your loved ones: It is important to check on family, friends, and neighbors, and keep track of how they are handling the stress. Ensure to check up on children, pets, the elderly, people with disabilities, and those who may need special assistance.

  • Be careful of flood waters when returning home: Following a flash flood, roads and walkways can experience damage due to erosion. Pay close attention when approaching areas that have been covered by floodwaters, and avoid them at all costs. You can try to find an alternate route where there are no flood waters, or stay put till the water recedes.

  • Be careful of downed power lines: Avoid stepping inside water following a flood because the water may have covered up some power lines. It is important to pay attention to this safety tip to avoid the risk of being electrocuted.

  • Check for structural damage to your home: Before entering your home after a flash flood, it is essential to ensure that it is not at risk of collapsing.

  • Follow electric safety precautions: Do not enter any structure after a flash flood until you are sure that power has been cut off. Avoid touching wet electrical appliances, or entering rooms where the electric outlets have been flooded.

  • Document property damages: Make sure to take photos of your damaged home because it can come in handy when filing a claim with your insurance company. The receipts for all repairs done should also be kept safe for insurance purposes.

Some cleaning and repairing tips to follow after a flash flooding include:

  • Make sure to wear protective clothing, including facemasks, waterproof gloves, and boots when cleaning up.

  • Wash flooded floors and walls with household bleach and clean water.

  • Dry all areas and home items quickly and thoroughly to avoid mold growth.

  • Dispose of any food, beverage, or previously opened medicine that has come into contact with flood waters.

  • Check your water for any contamination and avoid using it to brush your teeth, wash your hands, do dishes, and prepare food. To disinfect your water, the Louisiana Department of Health recommends that you use five drops of liquid household bleach to each gallon of water and wait for at least 30 minutes for disinfection to be completed.

  • Sanitize food contact surfaces and any other parts of the house that may have been contaminated.

  • Dispose of items that absorb water such as mattresses and carpeting which cannot be cleaned or disinfected.

  • Call a professional to repair damaged water and sewage systems.

  • Keep children, pets, and people with weak immune systems away until your home has been thoroughly cleaned and disinfected.

The state of Louisiana has put in place several flood recovery resources for disaster survivors. The Louisiana Department of Economic Development has a flood recovery resource page that provides information on how businesses affected by the flooding can receive assistance. The state also has a disaster distress helpline which provides a toll-free support service to people experiencing anxiety and emotional distress due to a storm. The helpline is available 24/7 via telephone (1-800-985-5990) and SMS (text ‘TalkWithUs’ to 66746).

To access federal disaster assistance, the governor must request for a major disaster declaration from the president for parishes under the declaration. Victims of flash flooding whose parishes have been declared as federal disasters should register for disaster assistance with FEMA. They can register online on the FEMA disaster assistance website, or call the registration phone number at 1-800-621-3362. Individuals that have a speech or hearing disability and use TTY should call 1-800-462-7585, while those who use 711 or Video Relay Service (VRS) should call 1-800-621-3362. Residents whose parish has not been declared yet should contact their parish Office of Homeland Security and Emergency Preparedness (OHSEP) to report damages. The governor can include the parish in the declaration if the state receives more damage assessments.