Flash floods are abrupt weather events that often occur within minutes to hours of a strong rainfall storm. They arise when there is more precipitation (rainfall) than the ground can absorb. When this happens, and the soil cannot effectively drain the excess water, it swiftly flows into rivers and streams, substantially increasing their levels, and causing a flash flood. During this event, roads get overrun with fast-moving water, which can destroy structures and carry vehicles away.
Flash floods may also occur in the absence of precipitation if a water control structure such as a dam collapses, if there is a levee failure or if there is a fast release of water caused by debris or ice obstruction. Dams that fail can generate large flash floods in the surrounding area, resulting in loss of life and property destruction. These occurrences might occur unexpectedly and with little or no warning.
Although this phenomenon shares some characteristics with floods, they are ultimately different. Flooding and flash flooding both include an overflow of water that submerges normally dry land; however, compared to flash floods, floods develop slowly. Floods are typically more predictable and occur over a longer period of time (several days or weeks).
On the other hand, a flash flood often occurs suddenly, usually after heavy precipitation that falls in a short period. They are significantly more dangerous and destructive than floods because it is difficult to adequately prepare for their rapid force and impact. They are often distinguished by violent floods that rip over riverbeds, streets, or mountain slopes, sweeping everything in their path.
Flash floods are responsible for the majority of flooding-related deaths in Texas. They endanger lives and inflict significant property damage; however, these dangers can be reduced by effectively planning for them and keeping a close watch on the weather.
Flash floods result in extensive losses ranging from loss of life to economic impacts.
Large debris and moving water can cause structural damage to critical infrastructures, such as roads, power, telephone, and cable lines. Furthermore, flood waters can alter or contaminate groundwater, making tap water unsuitable for drinking.
According to the National Weather Service, flash floods are the most lethal form of weather-related disaster in the United States. The immediate consequences of flash floods can include human casualties, the loss of crops and animals, and the deterioration of health conditions owing to the spread of waterborne illnesses.
Flash floods are exceedingly difficult to predict and occur quickly due to their intrinsic nature. People suffer severe injuries and even death considering they often strike without warning. Furthermore, flash floods can happen when people are asleep, increasing the risk.
Flash floods cause extensive property damage, both instantly and over time. They typically transport debris such as large boulders, which may cause significant structural damage to homes, leaving them uninhabitable. The water may also seize valuable properties, such as vehicles, art, bikes, mowers, etc.
When communication lines and infrastructures such as power plants, highways, and bridges are damaged or disturbed, economic operations halt. This disrupts inhabitants' daily lives for far longer than the time of the flash floods. This may result in a loss of means of subsistence, particularly in flash flood-prone locations.
The businesses may be forced to evacuate and cease all commercial activities, resulting in income and salary loss.
Flood victims and their families may suffer significant psychological and social consequences, leaving them traumatized for long periods. The death of a loved one may have a tremendous impact on those left behind, especially children. Additionally, displacement from one's home, property devastation, loss of family valuables and livelihoods, and disruptions to work and social activities are all possible sources of stress. The stress of dealing with these losses can sometimes be excruciating and have long-term psychological consequences.
Flash floods cause enormous costs for the populace and the government. The expense of relief and recovery may severely impact investments in infrastructure and other development activities in the area. The additional expenditures of reconstructing flood-affected areas, relocating people and their possessions, and removing damaged goods from such regions may divert the funds required for other development. Also, flash floods in a particular location may make long-term investments less desirable to the public and commercial sectors.
Many homeowners do not consider the danger of flash floods while insuring their houses since they are unusual and unpredictable. This often results in a tremendous loss for uninsured homeowners affected by the flash flood. Flood damage is not covered by ordinary homeowners' or renter's insurance policies; instead, flood insurance is bought via the National Flood Insurance Program.
The geology and terrain of Texas play a role in flash floods being the state's most prevalent weather-related cause of death. Some of Texas' largest cities are familiar with the threat of flash floods. However, certain parts of Texas are more vulnerable than others. In Southeast Texas, flash floods are most common along significant watersheds such as the Colorado, Brazos, or Trinity Rivers, and near urban areas such as the Houston metropolitan area.
Furthermore, a portion of Central Texas is known as the "Flash Flood Alley" because of its steep topography, shallow soil, and high rainfall rates. This terrain was formed by the Balcones Fault zone, which may be seen on the surface as the Balcones Escarpment. The escarpment runs through the heart of Texas, past Waco city to the north of Austin and San Antonio to the southwest of Austin.
Severe flash floods in the Balcones Escarpment are triggered by significant rainfall events and hydrologically effective drainage of the slope. Warm and moist air masses from the Gulf of Mexico combine with chilly air masses from the north and moisture from the Pacific Ocean over Texas. When huge volumes of warm and cold air clash, the hot air tends to rise above the colder air, creating an unstable atmosphere. The rising air generates condensation, which leads to rain. This impact is enhanced over the Balcones Escarpment, creating a substantial quantity of rainfall in a short time.
Additionally, nearly all regions' terrain directly to the north and west of the escarpment and along the escarpment itself is sloppy and fluvially dissected. This means that when it rains, the water flows out into the streams all at once rather than pooling there. This causes significant increases in the flow and eventually flash floods.
Another contributing factor is the region's clay-rich soil types. Clay soils have poor penetration and cause excessive runoff once saturated with water. When combined with the fact that there is more impermeable cover surrounding cities and suburban areas, all of these elements interact in almost perfect synergy to cause major flash floods.
Flood experts predict that future regional development would result in more impervious surfaces and hence more runoff, increasing the risk of flash flooding in the already flash flood-prone area. Furthermore, as a result of climate change, Texas is becoming increasingly prone to severe weather occurrences. The heavy rainfall in the state will only worsen due to increasing temperatures and shifting weather patterns.
Erin developed in the Gulf of Mexico on August 14th, 2007 from a continuous area of convection. It attained tropical storm status in the following days. A tropical storm, also called a tropical cyclone, forms when low-pressure air is accompanied by thunderstorms that create a circular wind flow with maximum sustained speeds of less than 39 miles per hour. The storm resulted in sixteen fatalities and worsened an already-severe flooding issue in Texas. The storm directly caused nine deaths, and its remnants caused seven more, mainly due to inland flooding from heavy rainfall.
The storm developed over the northwestern Gulf of Mexico and moved inland over the upper Texas coast, producing extremely heavy rainfall and catastrophic floods in Houston. The storm dropped an unusual amount of rain over a large stretch of Southeast Texas during its meandering journey through the region for five days in June 2001.
Within these 5 days, a substantial part of Houston and the surrounding areas received between 15 and 35 inches of rain, causing destruction in the form of flash floods. The most significant amount of precipitation fell between 6 to 12 hours on the 8th and 9th of June, which resulted in 22 deaths in the Houston area. Thousands of houses were either damaged or completely destroyed, and automobiles were submerged in water during the storm.
Tropical Storm Allison produced significant damage that cost billions of dollars, making it one of the most expensive tropical storms in Texas and the United States history.
From the evening of October 30th through late afternoon on October 31st, 2013, there was widespread heavy rainfall of 2-14 inches across Texas. The rain resulted in significant flash flooding along the I-35 Corridor from Georgetown to New Braunfels and major flooding of several creeks and rivers. The flash flood caused Onion Creek to reach its highest level since 1921. This resulted in 825 homes being damaged, 40 highways being closed, and, most tragically, four people being killed.
The southern area of Blanco County received between 10 and 13 inches of rain, causing the Blanco River to rise dramatically. This caused severe devastation in Wimberley, Texas, resulting in the deaths of 13 people and the destruction of about 350 homes.
Texas Hill Country is a geographical area in Central and South Texas. The Llano river, which runs for a reasonable distance in the hill country, swelled after receiving 8 to 12 inches of rain in 2018, causing the Kingsland Bridge to collapse.
This also led to the opening of multiple dams in the Highland Lakes System, flooding communities downstream. Following this disaster, Austin residents were required to boil their drinking water for a week because the amount of debris and garbage in the water posed significant difficulties for the city's drinking water system.
Planning is the best way to prepare for a flash flood in Texas. This is because flash floods regularly occur without warning. When it happens, it is often too late to devise a plan of action for dealing with it. Locals, their families, and the government must all participate for any preparatory approach to be successful.
Local government officials can ensure that they are informed of the most recent weather alerts, advisories, and statements issued by the weather service and that they are prepared to respond as necessary. They should also look out for floods or rising water in areas prone to flooding. Finally, they can make provisions for additional power supply to assist hospitals and other entities that are adversely disrupted by power outages.
On the other hand, the local population can do the following to prepare for a flash flood:
Know the flood risk at their home or business and prepare accordingly.
They may insure valuables and flood-proof belongings.
Store clean water because flood waters may contaminate the drinking water supply in the area.
Make a flood disaster supply kit that contains:
When a flash flood is imminent, a flash flood warning is issued, individuals in flood-prone regions must promptly seek higher ground. Flash flood warnings are transitioning to an Impact-Based style to increase public reaction. Impact-based warnings provide details about the threat, source, and potential impact.
The general flash flood alerts or warnings include:
Flash flood watch: This caution is issued first, indicating that the current weather conditions favor flash floods. Even while a flash flood watch does not ensure that there will be one, it is a strong signal that the neighborhood may experience severe weather.
Flash flood warning: This caution implies that a flash flood is already happening.
Central Texas is located in an area where flash floods are a known risk; as such, the region has taken numerous precautions and created warning systems to mitigate this risk. Examples include:
The City of Austin's Flood Early Warning System.
The Regional Notification System, which residents and other parties in the area can use to register their landlines and cell phones to get notifications about potential threats to their lives or property.
Hays County's Community Emergency Response Team. Its members are ready to respond to disasters such as wildfires, tornadoes, automobile accidents, and flash floods.
Hays County website for disseminating reliable information during emergencies
San Marcos, the Hays County Sheriff's Office, and the Hays County Emergency Operations Center have set an extraordinarily high standard in preparing for future flash flood disasters. During flash floods, they provide information on road closures and re-openings, alternate routes, repair plans, and advice to residents. Some instructions include public safety curfews and debris removal instructions for appliances.
These systems took time to plan and execute, and the outcomes of these efforts have evolved over several years.
Because flash floods are difficult to predict, the local population must be continually aware of the variables that may cause them:
There is a risk of flash flooding within the first six hours following a downpour
Collapse of a water control structure such as a dam or levee
Slow-moving storms passing over the same area multiple times
Hurricanes because they are a prominent cause of heavy rain, which often lead to flash floods
The National Weather Service has issued a "flood watch" or "flood warning" for the area.
A person’s location determines the most critical measures to take while stuck in a flash flood. Individuals on foot should be cautious since raging torrents may sweep them away. As a result, they are advised to avoid running water and seek higher ground.
Individuals stuck in their vehicles are advised not to drive across flood waters or underpasses. The water may be deeper than it appears, and the vehicle may become entangled or carried away by fast-moving water. If the car breaks down, passengers should get out, move to higher ground and avoid moving water.
On the other hand, individuals who are not in immediately dangerous situations should keep their radios tuned to emergency alerts to find out what areas are affected, what routes are safe, where to go, and what to do if the local emergency team orders an evacuation. In this instance, it is critical to keep an emergency kit on hand in case an evacuation is required.
After a flash flood, one of the essential things to do is ensure people's safety and get the home/business back in order as soon as possible. However, when flood restoration begins too quickly or too late, it can result in long-term difficulties such as mold development, bug infestations, and the deterioration of wood and wall coverings. As a result, the procedures involved in the repair and recovery should be taken cautiously.
Before returning inside the house after a flash flood:
Listen to local radio, television, or weather radio for essential information. Even when the water level has dropped, flooding is always a threat. The news updates help affected parties to stay informed about the situation and notify them when it is safe to travel or return home.
Watch for downed power lines.
Returning home after a flood should be attempted only when local officials signal it is safe.
Examine the building's utilities and structure to ensure their safety. Homeowners can look out for buckled walls or floors, shattered glass, or other potentially dangerous objects.
Individuals are advised only to re-enter a house after a certified electrician determines it is safe. This is especially critical if the main power switch was not turned off prior to the flash flood. When electrical equipment that have been submerged in water are turned on, they pose a risk of electric shock or fire. As a result, it is critical to avoid using any appliances, heating, pressure, or sewage systems until a professional electrician has thoroughly cleaned, dried, and inspected all electrical components in the house.
Individuals should only drink water from storage until the water in the affected area is officially determined to be fit for human consumption, free of contamination from waste, fuels, and other impurities.
Adults must practice extreme caution with children and pets.
It is essential to maintain a safe distance from any flowing water. Flowing water as shallow as just six inches may knock people off their feet, and most vehicles can be swept away by water as shallow as two feet.
It is suggested that persons whose homes or businesses have been impacted by flood water seek the aid of specialists for cleanup and restoration services for water-damaged things. They are strongly advised to use only competent contractors with a good reputation for the required cleanup and repair work.
Individuals assisting with cleanup and repairs are advised to use protective clothing, such as rubber gloves and boots, while cleaning.
Individuals are advised to dispose of anything immersed in floodwater, including food, medications, and other personal care products.
Homeowners with flood insurance must contact their insurance adjuster as soon as possible. They should also document their losses as proof. An ordinary homeowner's policy will likely not cover the damage. In such cases, if the President declares the flood a federal disaster, affected persons can apply for assistance.
During flash floods in Texas, it is not uncommon to find automobiles submerged in water. When exposed to water, the electronics, lubricants, mechanical systems, and car safety aspects, such as airbags, are vulnerable to damage. When individuals find their vehicles submerged in water, they should avoid starting the engine. Starting a flooded engine will cause significant damage and total the vehicle.
When evaluating whether or not a flooded vehicle can be repaired, it is essential to examine the extent of water damage to the car. If water made its way into the electrical areas of the vehicle, it might be considered a total loss.
Additionally, the likelihood of a flooded vehicle being repaired also depends on the type of water that flooded it. If the vehicle owner lives in a coastal area, it is conceivable that salty water may have gotten into the vehicle. If this is the case, there is no use in trying to save it because cars that have been damaged by seawater are usually beyond repair. But if the water is fresh, a seasoned auto mechanic may be able to repair the car without issue.
The expense of repairing automobiles submerged in flood water may exceed the cost of acquiring a new vehicle. It is best to have a mechanic check the car and offer feedback on the extent of the vehicle's damage. Overall, affected car owners are urged to consider all of their options thoroughly and consider if the cost of repairs will be higher than or equivalent to the cost of acquiring a new vehicle. Affected individuals with comprehensive auto insurance may be entitled to compensation for repairs or the vehicle's value.