What Is a Flash Flood?
Flash floods happen very fast. The National Weather Service defines flash flooding as flooding that happens quickly in an area that is normally dry or when water in a stream or creek rises very quickly above a predetermined flood level. An official flash floodt has to occur 6 hours or less after an event like a storm, a dam breaking, or an ice jam breaking.
The Worst Flash Flood in Texas History
It’s hard to say exactly what makes a flood the absolute worst. Is it how much the water rose? How many people died? How many buildings were destroyed or damaged? The cost of the damage? There are many metrics to determine just how terrible a flood was.
1. The Highest Flash Flood in Texas History
On June 25, 1954, Hurricane Alice rolled into town after a record drought. It caused flooding that was ranked as a 1 in 2,000 years event, meaning there is a 0.0005% chance of it happening in any year. The Rio Grande crested at 61.35 feet in Laredo, which is 10 feet higher than its previous flood crest. Over 16 inches of rain fell in 24 hours, leading to as much as 8 feet of floodwaters in towns like Eagle Pass and Ozona. Perhaps the most damaging part of this storm was a flash flood in the small town of Ozona. A 30-foot high flash flood described in some sources as a “wall of water” forced its way through a typically dry ravine and flooded the entire town, killing livestock and destroying the homes of 500 families. Flooding also heavily affected the city of Laredo. It washed away the international bridge between Laredo and Nuevo Laredo, the city on the Mexican side of the border. It also damaged the water treatment plant so badly that it took nearly a week for the water service to resume.
2. The Deadliest Flash Flood in Texas History
On September 8th and 9th, 1921, a tropical depression made its way to San Antonio, Texas. The storm released 18 inches of rainfall onto the city. Just a few hours away in the small town of Thrall, over 38 inches of rain were recorded in 24 hours. That is the record for the most rain in 24 hours of any US storm. Unfortunately, a huge 12-foot swell from the San Antonio river suddenly swept downtown in highly populated San Antonio, catching many by surprise. People rushed to upper floors of buildings and higher ground, but 51 people drowned in San Antonio alone. Across the whole state, over 200 people drowned in the flood waters. As a result of this storm, a dam and bypass channel were built to help protect downtown San Antonio from future flooding.
3. The Most Buildings Damaged By a Flash Flood in Texas History
Hurricane Harvey is one of the worst and most damaging storms ever in the US. It damaged over 204,000 homes in Texas, mostly in the Houston area. Most of these were damaged from flooding. The worst part is, most of these homes were outside of the 100-year flood plain so many homeowners did not have flood insurance. It wasn’t one flash flood that destroyed these homes but a series of flash floods caused by the hurricane. The storm was devastating and dangerous. Private citizens used their boats to take matters into their own hands and rescue their neighbors and deliver supplies. The Houston Police also contributed to the rescue efforts. Their dive team rescued more than 3,000 people in the first four days during and after the storm. A group of five police officers rescued 40 people in 24 hours. In the entire Gulf Coast Area, including Texas and Louisiana, over 1 million vehicles were damaged or destroyed. 800 wastewater treatment plants and 13 superfund sites flooded, spreading toxic waste throughout the flood waters. The highest coastal storm surge of 12.5 feet in Aransas County caused flash flooding in a nature preserve and caused a lot of damage in the town of Port Aransas. The town of Nederland, just across the border from Louisiana, reported over 60 inches of rain. That set the record for the most rain in a single storm. However, the hardest hit area was Harris County, where Houston is located. Its dense population and geography made the situation dire. The county is 1800 square miles. 70% of that was flooded with at least 18 inches of water. The city of Houston actually sank up to 2 centimeters due to the weight of the water, but it rebounded once the waters had receded. The reason this storm had so many flash floods was that instead of moving over the region over a period of hours, it stalled in one place for several days, just dumping rain, mainly from August 25 to 26, 2017. However, flooding in some areas of Texas, like Brazoria County, started as late as August 29, 2017, due to breached levees.
4. The Most Expensive Flash Flood in Texas History
Hurricane Harvey is the most expensive storm in Texas history. It cost $125 billion dollars in damages overall. However, the most expensive flash flood event in Texas might be a recent storm that happened on August 22, 2022, in the Dallas-Fort Worth area. A storm dumped 15 inches of rain on the area in 24 hours. 100 homes were damaged, which seems like peanuts compared to Hurricane Harvey, however, with all considerations in place, including spoiled food from power outages that is now more expensive due to recent inflation, damage to businesses, and disruption to the supply chain, experts believe the cost of this storm will be as much as $6 billion dollars. This would be the most expensive flood in the state that was not caused by a hurricane.
More Bad Floods in Texas History
Texas has had more than its fair share of floods. While there have been bigger floods since these ones came to pass, in their time, they were some of the worst floods to hit Texas up to that point.
5. 1913 Brazos River Flood
In December of 1913, the Brazos River spilled over its banks. It is one of Texas’ largest rivers and runs from the Gulf of Mexico to near Freeport. On December 11, 1913, it reached its highest crest of 56.4 feet. To this day the river has never flooded that high again. This came from a storm that happened between December 1 and 5 that year. It dumped over 15 inches of rain in the area. It had already been a high rainfall year and the ground was saturated with water between storms, already in a slightly flooded state. During this storm, the Colorado and Brazos Rivers actually merged briefly due to the flooding. 180 people drowned due to swift flood waters.
6. 1972 Flash Flood Disaster in South Central Texas
In 1972, 16 inches of rain fell across South Central Texas in just two hours. Flash floods from Blieders Creek and the Guadalupe and Comal Rivers inundated the small city of New Braunfels in minutes. 18 people drowned in the city. Other nearby cities of Seguin and San Marcos had no deaths but severe damage. The storm cost $20 million in damage, which would be over $140 million in damage today. Experts at the time predicted that many lives were saved by warnings sent out quickly by the Weather Service Offices in San Antonio and Austin.
7. 2015 Texas–Oklahoma Flood and Tornado Outbreak
Following a week of heavy rains, a strong and slow storm settled over Texas and Oklahoma. Starting on May 24th, flash flood warnings were issued in South East Texas. Overnight, between May 25th and 26th, 11 inches of rain fell in the Houston area, resulting in more flash floods. The flooding caused a 25-square-foot sinkhole at the Dallas Fort Worth Airport. The Blanco River in Central Texas rose over 35 feet in a few hours. Overall, 14 people were confirmed dead in both Texas and Oklahoma, but more were listed as missing as they were never found.
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The National Weather Service defines it as flooding that happens quickly in an area that is normally dry or when water in a stream or creek rises very quickly above a predetermined flood level. To be an official flash flood it has to occur 6 hours or less after an event like a storm, a dam breaking, or an ice jam breaking. What was the highest flood in Texas? On June 25, 1954, after a record drought, Hurricane Alice came rolling into town. It caused flooding that was ranked as a 1 in 2,000 years event, meaning there is a 0.0005% chance of it happening in any year. The Rio Grande crested at 61.35 feet in Laredo, which is 10 feet higher than its previous flood crest. What was the deadliest flood ever in Texas?
On September 8th and 9th, 1921, a tropical depression made its way to San Antonio, Texas. The storm released 18 inches of rainfall onto the city.
Unfortunately, in highly populated San Antonio, a huge 12-foot swell from the San Antonio river suddenly swept downtown, catching many by surprise. 51 people drowned in San Antonio alone. Across the whole state, over 200 people drowned in the flood waters.
What is the most rain to fall in 24 hours? In the small town of Thrall, Texas, over 38 inches of rain were recorded in 24 hours between September 8 and 9, 1921. That is the record for the most rain in 24 hours of any US storm. Which storm damaged the most buildings in Texas? Hurricane Harvey damaged over 204,000 homes in Texas, mostly in the Houston area. What is the most expensive flash flood in Texas History? The most expensive flash flood event in Texas might be a recent storm that happened on August 22, 2022 in the Dallas-Fort Worth area. A storm dumped 15 inches of rain on the area in 24 hours.Experts believe the cost of this storm will be as much as $6 billion dollars. If it is, it would be the most expensive flood not caused by a hurricane in the state.
