A flash flood is characterized by sudden flooding in an otherwise dry area. It happens unexpectedly and, in most cases, without warning. This can happen for various natural and anthropogenic (man-made) reasons, and it can significantly negatively influence both the natural and urban surroundings.
A flash flood is one type of flooding. Flooding, in general, is the overflow of water into normally dry terrain. River floods, for example, happen when rivers begin to overflow their banks due to rising water levels caused by days of continuous rain and snow melt. While some floods develop slowly over several days, others develop quickly in a few hours.
Flash floods are considered destructive due to their catastrophic impact and lightning-fast speed, which allows them to destroy entire communities. Although they occur only briefly, their impacts can last months or even years. Flash floods have disastrous and diverse consequences, including extensive structural damage, destruction of plants and wildlife, loss of human lives, and massive financial costs.
A flash flood happens when floodwaters rise rapidly and without warning within a few hours, usually less than six hours, following a heavy rainstorm. It occurs when there is more water in a given area than the soil can absorb. Flash floods can occur in rural and urban settings, but it is more frequent in areas near water sources such as rivers or lakes. Still, they are not limited to places that already have water. Damaged levees, dams, or ice jams can release high walls of water into normally dry areas. Natural and man-made elements can create or intensify flash floods.
Cloudbursts: Cloudbursts occur when a large amount of precipitation falls over a given area in a short period of time. They are sometimes accompanied by hail and thunder, and they have the potential to cause floods. Cloudbursts occur when a powerful upward flow of warm air containing water vapors interrupts the path of continually falling rain and returns it to the cloud. When the cloud cannot support the weight of such huge amounts of both old and fresh rain, or when the upward circulation of warm air weakens, the water is dropped on a specific place. This causes a large amount of precipitation to fall in a short period of time, eventually leading to flash floods.
Overflowing River Banks: Flash floods can occur when excessive rainfall causes rivers, streams, and other water bodies to overflow and breach their banks.
Melting Glaciers: Rapidly melting ice and snow can also lead to flash floods, which are especially deadly when mountain snow begins to melt. Although human activities may contribute largely to melting glaciers, volcanic eruptions on glacial mountains can also cause hot lava to melt the glacier.
Slow-Moving Thunderstorms: These thunderstorms travel slowly over an area, dropping heavy rain and causing flash floods.
Hurricanes and Other Tropical Storms: Tropical storms, hurricanes, and other storms bring a lot of rain, which can cause flash floods.
Drought: After a drought, flash flooding can occur when the soil becomes too dry and brittle to absorb the following precipitation. Flash floods are common in desert areas during heavy rains and in areas with shallow soil depths over solid bedrock, which inhibits the soil's ability to absorb rainwater.
Dam Failures: One of the most common human-caused flash floods is dam failures or breakages, which can induce flash flooding in a region and even turn valleys into lakes. Dams may break due to poor design or construction.
Blocked or Improper Drainage System: Flash flooding can occur when it rains heavily, but the drainage system is congested or ineffective in handling such large amounts of water. Also, if there has recently been rain in the area, the soil may be entirely saturated with water and unable to absorb any more. This could also result in flash floods.
Climate Change: Human activities are the fundamental cause of climate change. Human consumption of fossil fuels and the destruction of rainforests increase the earth’s average annual temperature. leading to irregular weather patterns and extreme weather events like hurricanes and other storms that lead to flash floods.
Deforestation: Forests help to reduce flood speed and volume by allowing water to soak into the ground more easily and quickly. The risk of flooding increases when there is a shortage of vegetation (including trees, grass, and other plants). When this buffer zone is breached, floodwaters can reach a location at full force, resulting in a flash flood.
Flash flooding can have serious implications, affecting not just the economy but also the environment and the people who live there. Flash floods have various repercussions, including:
The loss of lives
Substantial structural damage
Loss of crops and livestock
Destruction of essential infrastructure.
When communication links and infrastructure, such as power plants, roadways, and bridges, are damaged or destroyed, economic activity is put on hold. This causes disturbance and dysfunction in daily life for far longer than the timeframe of the disaster. Consequences of such infrastructure damage include disruptions in clean water and electricity supplies and disturbances in transportation, communication, education, and health care. These reduce residents’ ability to make purchases or manufacture goods.
Also, the additional expenditures of restoring affected areas, relocating people and their belongings, and removing damaged entities from those areas may divert funds needed to keep production running. The enormous cost of relief and recovery may severely impact investments in infrastructure and other development activities in the region and in some cases, may be enough to collapse the region's already weak economy.
Flash floods also have psychosocial consequences. Flood victims and their families might be traumatized and suffer from post-traumatic stress disorder (PTSD). The death of a loved one can have a tremendous impact on those left behind, especially children. Being displaced from one's home and losing means of survival can all lead to chronic stress. The stress of dealing with these losses can sometimes have long-term psychological consequences.
Overall, depending on the extent of destruction a flash flood causes, affected communities may require multiple years to recover and rebuild to the point where normalcy may be restored.
Mississippi has a long history of catastrophic flooding. This is because the state is home to part of the world’s major river basins. The Mississippi River receives its water from a vast catchment region. It is the world's fourth-largest watershed, spanning 31 states and covering 3.1 million square kilometers (1.2 million square miles). Precipitation and runoff from mountainous areas as far apart as the Rocky Mountains in the west and the Allegheny Mountains in the east flow to the Mississippi River through a complicated network of over 200 tributaries.
As a result, the river is influenced by both local and distant events. The rivers can rise to unexpected heights in the spring and summer, especially when snowmelt and a lot of rain combine. The Mississippi River is not just prone to overflowing but also notorious for catastrophic floods. As a result, its surrounding areas face an increased danger of inland flooding. According to research, the danger appears to have increased over the last decade and this tendency may continue.
Due to climate change and the severe weather events and natural disasters that came along with it, flash floods are becoming increasingly common in many parts of the world, including Mississippi. Warmer temperatures alter ocean current patterns, influencing weather all around the planet. In some regions, more precipitation will fall than the ground can absorb. There will also be less rainfall in some areas, making the earth to become drier and less capable of absorbing rainfall when it does fall.
According to the Environmental Protection Agency (EPA), intense rainfall is increasing due to climate change. The frequency of heavy rain events is also predicted to increase by two to three times the historical average, and hurricanes and storm surges will raise the risk of flash flooding. Warmer temperatures may also increase snowmelt, which may cause sea levels to rise.
Flash flooding has a significant and negative impact on both natural and man-made environments and all living beings. Preventive measures against flash floods should be adopted alongside climate change adaptation and mitigation actions to help lessen the severe effects of climate change. Some of these measures include:
Increasing the number of green spaces that function as buffer zones
Building embankments to divert water away from open land
Maintaining floodplains and overflow zones along rivers and streams to allow them to flood without causing damage
Development of efficient urban drainage systems
Implementation suitable rain-management strategies.
Improving flood warning systems and disaster response strategies
Public education and awareness initiatives on how to properly prepare for flash floods.
Flash floods occur swiftly and often catch people off guard. This often results in catastrophic damages. As a result, planning is the ideal way to survive a flash flood and limit its costly consequences. Staying informed and having a plan can help Mississippi residents boost their chances of survival.
Before a flash flood, residents are urged to prepare a disaster plan that covers all household members and pets. This plan must detail how the family would communicate, meet, and evacuate in the event of a flash flood emergency. Consequently, the plan must include:
Assembling emergency supply kits that contain enough non-perishable food and water to last at least three days. It should also include a first aid kit, battery-powered radio, a flashlight, safety equipment, and other necessities that individuals or pets might require in the event of an evacuation.
A list of all emergency contacts, including family members and emergency response services.
An evacuation plan that maps out trails to get to higher terrain and drier circumstances in an emergency.
Possible shelters to stay if evacuation is necessary.
Flash flood drills that allow household members to practice evacuating quickly.
Understanding various flood alerts.
Filling sinks, baths, and bottles with clean water because floodwater may contaminate water sources
Staying informed by listening to a National Oceanic and Atmospheric Administration (NOAA) Weather Radio or a local news station.
This plan can help an entire household to make efficient decisions in a flash flood emergency.
In addition to endangering human life, flash floods are extremely destructive. However, there are means of reducing the extent of structural damage. Homeowners can safeguard their property by doing the following:
Knowing Their Flood Risks
Flash flooding can occur anywhere there is a possibility of rain. Residents can learn more about the flood risk connected with their homes using a flood map, such as the type of flood zone it is in and, if available, the probable flood elevation. They may also research their proximity to any drainage channels, streams, or other low-lying areas prone to flash floods. Knowing the risks helps decide the best countermeasures. Due to the ever-changing topography and climate, it is best to run a risk analysis periodically.
Obtaining Flood Insurance
Homeowners in Mississippi should insure their possessions and property to protect themselves financially during a flash flood. Even if their home is in an area with a low or moderate risk of flooding, they are strongly advised to obtain flood insurance.
Flood water damage can cost thousands of dollars and is usually not covered by an ordinary homeowner's insurance policy. As a result, it is critical to purchase flood insurance. The National Flood Insurance Program (NFIP) provides flood insurance guarantees.
Improve Property Landscape and Drainage
Homeowners can identify potential issues by determining how water flows through their community and where it pools. Then, if necessary, they can adjust the landscaping to increase drainage and divert water away from the building. This may require filling low spots around the house's foundation, constructing drainage ditches, and altering the yard so it slopes away from the house.
It is critical to clean and maintain gutters, downspouts, and splash pads regularly so that rainwater collected on the property may easily flow away. Residents must ensure that any nearby drainage ditches or storm drains are clean and clear of impediments.
Reduce the Number of Impervious Surfaces Around the Property
Water pours off concrete and asphalt when it rains intensely, causing storm sewers to quickly reach or exceed their capacity. Retaining and maintaining natural green space surrounding the property can help to reduce sewage overflows by reducing the amount of stormwater runoff. Homeowners can consider alternatives such as rain gardens and permeable pavements, allowing the earth to absorb more rainfall.
Keep Valuables Safe
Important documents and other valuable or sentimental items should be relocated to a safer location well above the projected flood elevation and placed in watertight containers. This increases the chances of the contents remaining intact despite a flash flood.
Install Flood Vents
Flood vents are small permanent holes that allow floodwater to flow through an enclosure like a crawlspace or garage freely. Flood vents that are properly positioned and installed protect properties during flash floods by minimizing water pressure buildup that can destroy walls and foundations. Once installed, it is important to keep flood vents clear of debris and open to allow floodwater to flow freely.
Use Flood-Resistant Construction Materials
Property owners should incorporate flood-resistant materials for internal walls and ceilings, such as lime plaster, concrete, or pressure-treated and decay-resistant wood. Metal and other flood-resistant solutions may also be used to replace timber doors and window frames.
Safeguard Utilities and Service Equipment
A licensed electrician can help raise the height of all electric service panels (fuse and circuit breaker boxes) and all outlets, switches, and wiring to at least one foot above the anticipated flood elevation. The main components of the heating, ventilation and air conditioning (HVAC) systems should be relocated to a higher floor or the attic.
If relocation or elevation is impossible, low floodwalls and shields can be used to protect service equipment that is already in place. This low-cost strategy can help reduce the amount of severe damage and disruption caused by a flash flood.
Document All Valuable Possessions
Take photographs and videos of the entire structure as well as other valuable possessions and store them in a safe place. If a flash flood damages the property, homeowners can use these items to support their flood insurance claim.
The National Weather Service (NWS) issues either a flash flood watch or a flash flood warning.
A flash flood watch indicates that weather and environmental conditions are suitable for flash flooding. While a flash flood watch does not guarantee one will occur, it is a strong signal that the area may experience extreme weather. Residents should therefore be on the lookout for flash flood warning signs and be prepared to evacuate if necessary. When this signal is issued, those in high-risk locations are advised to move to higher ground.
On the other hand, a flash flood warning is issued when a flash flood is occurring or is imminent. A warning may also be issued due to excessive rain, dam failure, or snow melting. If a flash flood warning is issued, inhabitants in the affected region should leave immediately because there may only be a short time to flee. They should move to higher ground immediately, away from any local rivers, streams, creeks, or storm drains.
Various factors determine the rate at which a flash flood can occur and the location where it can occur. These flash flood risk factors include:
The Intensity and Duration of Rain
The rate at which it rains is referred to as the intensity, while the duration is the length of time it falls. Flash flooding occurs when rain falls so quickly that the underlying ground cannot keep up or drain it away quickly enough. As a result, the areas of Mississippi with the most rainfall are at risk of flash floods. For example, residents of Gulfport, Jackson, and Pascagoula are at risk of flash floods because these cities receive the most rain in the state.
Nonetheless, it is worth noting that Mississippi was one of the states that received the most rainfall in the United States in 2021. The state had 66.84 inches of precipitation that year. Since flash flooding is probable anywhere there is rain, all state residents should be vigilant and prepared.
Urbanization and Land Use Change
Aside from extreme weather events, land use change and other human activities might make some areas of the state more prone to flash flooding than others. The loss of plant cover, particularly forests, which are essential for controlling hydrological systems, collecting rainwater, and managing floods, increases flash flood risk. However, as the human population grows and infrastructure and roadways connecting other infrastructures are built, certain regions that were formerly covered by vegetation have been altered into residential zones.
The challenge generated by urbanization and infrastructure development is the development of an impervious surface. Following heavy rain, such surfaces limit infiltration and promote surface overflow, resulting in flash floods. Water that cannot seep into the ground accumulates on the surface of roads and has the potential to turn main streets into fast streams. Since impermeable surfaces are common in Mississippi's urbanized areas and cities, these areas are at risk of flash floods, and residents are urged to prepare accordingly.
Low-lying areas are those that are close to or at sea level. In general, Mississippi is low-lying, with the highest point reaching only around 800 feet (240 meters) above sea level. Flash flooding is a problem in low-lying locations, whether the water rises slowly or quickly and whether the place is urban or rural. When it rains, surface runoff can swiftly move from mountainous or hilly places to low-lying areas, making them more vulnerable to flooding. Because water always goes in the slope direction, the rain will seek out the lowest point along a likely path.
Parking lots, streets, and basements are common low-lying areas in cities. Creeks and rivers in rural areas with steep topography can also turn into fast torrents due to flash flooding.
Natural Drainage System
Although flash flooding is not limited to bodies of water, residents who live near water sources should be aware that they are at risk. Mississippi has various rivers, creeks, bayous, and other natural drainage systems. Flash floods may occur when these places fill up with water too quickly.
Safety is critical when a flash flood warning is issued. Residents are advised to maintain safety by:
Moving promptly to higher ground, such as the top level of the home
Staying tuned for more information
Avoiding low-lying areas because they are more likely to flood without warning
Staying away from previously flooded areas
Evacuating immediately if the order is issued
Avoiding floodwaters, especially if they are moving
Closing the main gas valve and turning off all utilities
Avoiding contact with any electrical equipment when standing in water or even just slightly damp.
Being watchful of displaced wildlife, particularly snakes.
Individuals caught in their vehicles during a flash flood are advised to not drive through flooded areas. Instead, they should get out of the vehicle and onto higher ground, particularly if the water level is rapidly rising.
Residents in affected localities must do these after a flash flood:
Individuals who evacuated must only return with authorization from the appropriate authorities
Report injuries to the nearest hospital or clinic
Stay away from disaster areas to maintain safety and to prevent interfering with other emergency operations and relief activities
Use only stored water until authorities deem the community supply safe to use.
Inspect their homes’ electrical components and appliances for signs of damage
Notify the proper authorities about any affected utilities
Fix any broken appliances and have a professional check the house's structure.
Look out for gas leaks, electrical system damage, and broken water or sewage lines.
Perform a thorough inspection of the building to check that the walls, floors, doors, staircases, and windows are not in danger of collapse
Look for cracks and other types of damage in the foundations
Take out any food that has been contaminated by floodwater
Search the yard for any wild animals that the flood may have relocated
Stay away from buildings that are surrounded by floodwaters because floodwaters often destroy foundations, causing floors to sink or break and, in the worst cases, the whole building to collapse.
Wear sturdy shoes and protective clothing during cleanup
Use battery-powered flashlights to reduce the risk of fire
Scrub and disinfect all walls and floors with a bleach solution or any other products that kill germs.
After returning home, affected homeowners can begin the insurance claims process. To do so, they must photograph and video the flood-damaged areas of their home and personal belongings. They may also save some samples of the damaged items to show their insurance assessor the extent of the flood damage. After photographing and videotaping the damage, it is critical to dispose of any items that have been destroyed by flood water and pose a risk to public health.
The amount paid out on the claim will be determined by the supporting evidence provided and the insurance policy's coverage. It is up to the property owner to provide evidence to back up their claim and to adhere to any deadlines that could be set.