Expert cautions on rebuilding within Guadalupe River floodplain

As important as warning systems might have been to help save lives in recent flooding, other experts say we should also think very hard about where we rebuild along rivers.

Adnan Rajib is an assistant professor of civil engineering at the University of Texas at Arlington and director of its H2I Lab, which just modeled to the Guadalupe River flooding. He joined Texas Standard for a discussion. Listen to the interview above or read the transcript below.

This transcript has been edited lightly for clarity:

Texas Standard: You are heartbroken like the rest of us, but not shocked by the devastation of the July 4th flooding. Before we get into the specifics of the Guadalupe River, can you tell us briefly about your work on floodplain disturbances in general?

Adnan Rajib: Yes, over the last couple of years, we have used state-of-the-art satellite data, both from NASA and European space agencies. We modeled how humans are disturbing the natural floodplains within the U.S. and globally. And we have found some really shocking outcomes.

We found that, globally, in the last 20/25 years, we lost more than 500,000 square kilometers of natural floodplains. And that’s almost the size of France. Imagine one big country disappearing from the face of the Earth.

So protecting the natural floodplain is fundamental to protecting people from flood hazards, but we are not doing that.

Well, what do we know about the buildup along the Guadalupe River?

The flooding at Guadalupe River is not very new. In the past 25 years, that river segment near Kerrville reached close to moderate or major flood stage at least seven times. So this flood disaster is not new.

However, what made this particular disaster more significant is because of human settlements that popped up in recent years. From 1990s up until 2020, Kerrville area – that Guadalupe River floodplain near Kerrville – lost more than 100 acres of natural floodplains.

And when we modeled the July 4th flood and overlaid the flood map on the natural terrain, we found even Camp Mystic, part of the camp, was within the floodplain. And there are other campsites and Airbnbs and whatnot. So 100 acres from a small area being lost is a big deal.

» RELATED: ‘An awful day’: Former Hill Country EMT remembers deadly 1987 Guadalupe River flood

Well, people might not be ready to hear this right now, but what do we need to do differently in the Hill Country when it comes to floodplain building?

So, first of all, we need awareness. We focus too much on developing flood data. Having the data available to the public is great, and the state of Texas is doing a great job. However, when it comes to protecting the floodplain and making people aware of making room for water within the floodplain, we need to have more advanced data, such as risk data.

Floodplain alteration is sort of a risk data which is different from traditional flood warning. Within that risk data paradigm, people will get to know these are the flood hazard areas and this is how it changed over time and this is why you should not build a new home.

So are you saying that even with a warning system, we shouldn’t build back before along the Guadalupe?

Yes, exactly. Because when you build homes and build developments within the floodplain, what we do is we take the natural landscape away from the floodplain.

The floodplain is supposed to use that natural ability to store the water. And if we build homes and parking lots within the flooding, that naturalability gets compromised. So water doesn’t have anywhere to go.

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