Is Houston Prone to Flooding?

Is Houston Prone to Flooding?

While flooding impacts nearly all Americans across the country, some places are more at risk than others. Some of the top states with the biggest risk of flooding include New York, California, Louisiana, New Jersey, and Texas. In fact, Texas ranks no. 1 in this list. All the coastal cities like San Antonio, Corpus Christi, Galveston and Houston, Texas are located in flood risk areas.

In the Texas city of Houston, extreme rainfall events are nothing new. In fact, these natural disasters have been increasing in recent years. If you’re living in Houston, you have most likely experienced major flooding at least once or twice. 

According to the National Centers for Environmental Information of the National Oceanic and Atmospheric Administration (NOAA), Harris County, where Houston is located, recorded an average of four to five days of flooding annually from 1996 to 2015. 

Floods in Houston have three major sources: excessive rainfall, overflow of rivers or streams due to heavy rainfall or snowmelt, and seawater inundation of coastal areas due to storm surges, high tides, or sea-level rise. 

The U.S. is prone to many natural disasters, including floods. Flooding constitutes 90% of the natural disasters that hit the country. This natural disaster causes more significant economic damage, along with loss of life and property, than winter storms, tornadoes, hurricanes, earthquakes, or wildfires.  

Houston Flood Risk

Space City has a moderate risk from flooding, according to First Street, with more than 350,000 properties in the city at risk of flooding over the next 30 years. Over half of that number is at risk of flooding today. 

The Texan cities with the highest flood risk are Port Arthur, Galveston, and Bolivar Peninsula, while Forth Worth, Arlington, and Lubbock have the lowest flood risk. To compare: Port Arthur has a consistent 99.4% flood risk now, in 15 years, and in 30 years, respectively. Meanwhile, Fort Worth has a 9.9% risk of flooding now, 10.3% in 15 years, and 10.6% in 30 years. 

Houston, on the other hand, has a 62.6% flood risk now, 61.4% in 15 years, and 60.2% in 30 years. This is more than the average flood risk in Texas which is 25.5% and well above the country’s flood risk in 15 years which is at 20.6%. 

Table 1. Percent of properties at risk from flooding in Texas

CityNow15 Years30 Years
USA20.6%
vs.
Texas25.5%25.5%25.5%
vs.
Houston62.6%61.4%60.2%
vs.
Port Arthur99.4%99.4%99.4%
Fort Worth9.9%10.3%10.6%

Source: First Street 

Causes of Houston’s Flooding Problem

Flooding in Houston is not something new. In fact, it is considered to be the region’s no. 1 disaster. 

There are three primary factors that contribute to Houston’s flood problem. The deluge in Space City can be attributed to a combination of geography, urban planning and development, and climate and climate change. 

Geography

Houston’s landscape features a relatively flat topography. It’s just a little over 40 feet above sea level. This doesn’t make it easy for floodwater to drain or move toward the Gulf of Mexico. Even its flat system of bayous drains water very slowly.

In addition, Space City is filled with soft-clay-based soil, which also does a poor job of absorbing or draining water from hurricanes, tropical storms, or heavy rain.  

Urban planning and development

From 1997 to 2017, nearly 187,000 football fields were added to Houston’s metropolitan area, according to a study by the Kinder Institute for Urban Research at Rice University

“What was once farm or wetlands is now pavement and suburbia,” Matt Lanza, an operational meteorologist in energy based in Houston, told the National Weather Service (NWS). “Thus, there is less barren land to suck up the rain now, and that further exacerbates flooding.”

The added urban development is equivalent to a 63% increase in impervious surfaces, such as asphalt and concrete. Herein lies the problem: These surfaces don’t absorb rainfall. 

“Impervious surfaces do not soak up heavy rainfalls the same way that natural landscapes do, not to mention the ways in which changing elevations and rerouted waterways rework watersheds,” the researchers wrote. “Without nature’s super sponges, water can run roughshod.”

Perhaps because of this, streets have become the city’s primary drainage mechanism, flushing water to the bayous and then to Galveston Bay and the Gulf of Mexico. However, they aren’t doing a good job of it. 

“As far as our streets are concerned, it is important to remember that our primary drainage mechanism throughout this city is our streets,” Houston Public Works Chief Operating Officer Randy Macchi said at a news conference. “For better or worse, that is the reality of the situation.”

Climate and climate change

Houston is located near the Gulf Coast, where warm air tends to develop into hurricanes or other tropical cyclones. In other words, the city’s climate makes it susceptible to torrential rains and storm surges.

Because of Space City’s geography and urban planning hurdles, this huge amount of water has a hard time getting absorbed by the soil or draining out into nearby bodies of water, such as Galveston Bay and the Gulf of Mexico. Flooding then ensues. 

“You’re getting to the point where you just have no place to put the water,” Richard Rood, a professor emeritus of climate and space sciences and engineering at the University of Michigan, told The Washington Post.

Furthermore, with sea levels rising due to climate change, repeated floods have only resulted in the rise of water tables. Combined, these factors create an excellent condition for floods to occur.

“Climate change has exacerbated flood risk across the country, especially when it comes to sea-level rise,” Federal Emergency Management Agency Administrator Deanne Criswell noted.

In other words, Houston’s climate predisposes it to an influx of water that its geography and urban development has a hard time absorbing or draining, and climate change just makes things worse. 

 “Climate change is happening right now with real and substantial costs,” Kevin Smiley, a sociologist at Louisiana State University, said in a statement. “Three to five extra inches of rainfall from climate change can make the difference between your lawn getting soaked and your house getting flooded leaving it uninhabitable.”

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