Previous incidents and statistics of floods in Texas

On August 25, 2017, Hurricane Harvey struck Texas. It became the country’s first major hurricane since Wilma hit Florida in 2005, and that of Texas since Hurricane Celia in 1970. It caused around $125 million in damages, making it the second most costly hurricane to hit the US mainland since the 1900s. At least 39,000 people were forced out of their homes to seek safer shelters.

Floods are considered the most common and costly disasters in the US. In the past five years, floods have struck all of the country’s 50 states. A single inch of water could cost more than $26,000 in property damages.

The Hill Country and Central Texas are more prone to flood incidents than most regions in the United States. The area is called the Flash Flood Alley because of its steep terrain, shallow soil, and unusually high rainfall rates.

Texas has two rainy seasons, with April and May as the wettest months. Spring thunderstorms form in the northwest of Texas over the Balcones Escarpment, a range of cliffs that drop from the Edwards Plateau to the Balcones Fault Line and leads to the Coastal Plains in the Southeast. Meanwhile, storms from the Gulf of Mexico cause rains in September and October. While these storms also cause floods, they are different from those of the “Flash Flood Alley.”

The phenomenon which causes the major floods is called the orographic effect. Dr. Nelun Fernando, a hydrologist at the Texas Water Development Board, said that the rising air condenses which causes rainfall. He added that the effect gets concentrated over the Balcones Escarpment, and if the slow-moving frontal systems come through, then the constant stream of moisture from the Gulf of Mexico will produce inches of rainfall in just a short period.

The Flash Flood Alley caused many tragic incidents, taking people’s lives and destroying property. In September 1921, a 12-feet deep wave flooded downtown San Antonio, killing 51 people over a two-day period. The intense rain continued, and 38.2 inches of rainfall was recorded northeast of Austin from September 9 to September 10, causing an additional death toll of 87 people.

On May 2015, during the Memorial Day weekend, the Blanco River rapidly rose and flooded the Wimberley area which killed 11 people. The river went from 5 feet to 40.3 feet in just four hours which not only took lives but also destroyed bridges and homes. After the incident, local governments organized the Blanco River Regional Recovery Team which helped more than 1,000 families.

The National Weather Service advised those living near the Flash Flood Alley to stay informed and prepare beforehand during a storm. They added that after a flood, people should avoid disaster areas and wait for them to clear before accessing them.