With each issue, Trib+Water brings you an interview with experts on water-related issues. Here is this week's subject:
Samuel D. Brody is a landscape architecture and urban planning professor at Texas A&M University's College of Architecture, as well as the Department of Marine Sciences at Texas A&M-Galveston. He is a director at the Institute for Sustainable Coastal Communities and leads the affiliated Center for Texas Beaches and Shores. He's also the co-author of the book Rising Waters: The Causes and Consequences of Flooding in the United States, which focuses on flooding in Texas and Florida.
Editor's note: This interview has been edited for length and clarity.
Trib+Water: We’ve seen heavy flooding in recent weeks and will see more with Tropical Storm Bill. Are you surprised by anything you’ve seen?
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Samuel D. Brody: No. These areas are some of the most flooded and flood damaged areas in the country, so we expect chronic and repetitive flood events over time. It’s all been exacerbated by increasing development and impervious surfaces. I think actually one of my surprises is I think we should do better at warning and preparing residents. In all the floods that have occurred, most of the people who die from floods or are injured from floods are not aware of the risk or aren’t appropriately warned of impending inundation.
Trib+Water: So what can officials do to better warn people?
Brody: There are a lot of different options. Some are long term and proactive like educating different neighborhoods. There’s a lot of visualization tools available on the internet that could be developed so that anyone can see where they lie in relation to a floodplain or low-lying area. And then there’s shorter term solutions where we can warn people based on flood gauge readings via cell phone, via emails — not just blanket warnings but very specific residences.
I think we need more flood gauges. So the Blanco event, if we had more flood gauges and better understood the timing of the rise of that river, we could’ve been able to warn people and keep people away from those flooded areas much more effectively, and I think it probably would’ve reduced the loss of life.
Trib+Water: Any other lessons that policymakers and officials should take from what we’ve seen with these storms?
Brody: You need to look at the big picture. So we have all these ad hoc and site-specific mitigation techniques. Looking at the system and the big picture, we have a lot of the ad hoc, site-specific mitigation measures in place, but we’re not looking at the larger forces at play and the tremendous development that the area and the region — Houston and to the west — have experienced in the last 15 years and the spread of pavement and impervious surfaces across the landscape, which change the drainage patterns and make flash floods more likely because the water runs directly into the bayous and the streams and the rivers.
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Even though we have retention and detention ponds, it’s not enough to keep pace with the growing development. Harris County alone between 1996 and 2011 added 150 square miles of pavement. That’s huge. That’s like a 24 percent increase in 15 years. So we need to think about the regional growth patterns, where we’re putting structures, where we’re putting pavement over time. Again, Houston and Texas in general, the most hazards from floods occur there, the most damage per capita from flooding historically has occurred there. I think we’re doing a lot, but we can do things a little better.
Trib+Water: Is there a way to have increased development while keeping the area safe?
Brody: Yes, we’ve done a bunch of studies that show there’s different techniques where you can develop and still avoid losses. The No. 1 technique — vertical avoidance — is elevating buildings above the base flood elevation at your flood level. Nationally, that’s saving communities approximately $960,000 in reported losses per year. We did a national study for FEMA.
Another technique is what we call horizontal avoidance and that’s pulling back a little bit from these bayous and rivers and creating open space and recreational areas in there. You’re removing structures and people from harm’s way but you’re also creating these natural retention and detention ponds, the areas where water can be stored and slowly released. You can have development but these areas, leaving those alone or pulling away from those — that’s what we’re doing in some of the bayous and have done in Europe for years and years — and allowing the river to flood more but without harming people has been shown to be really effective.
Trib+Water: What terrain and climate features make this the “flash flood alley”?
Brody: You’ve got coastal areas that have no typography or are basically at sea level, and they’re vulnerable to inundation from storm surge like we’re seeing today but also they’re areas that experience heavy bursts of rainfall. So you’ve got this kind of dual threat on the coast of rainfall based on flooding and surge based flooding. And then further to the west and northwest you still have those heavy bursts of rainfall. The soils tend not to allow infiltration of rainwater very easily, so the water runs right into the rivers, and that creates flash floods. But really that’s happened forever. What we’re doing is we’re exacerbating those floods with development and we’re putting people more and more in harm’s way. Those two factors are causing more damage and greater human casualties over time.
Trib+Water: Your work has pointed out local communities have increasingly taken responsibility for planning for floods. What are the implications of that trend in Texas?
Brody: We’re finding that communities who either join the community rating system program (the federal program that provides jurisdictions incentives to plan and mitigate at the local level) or communities who are just doing it outside of any institutional program, they’re experiencing significantly lower per-structure, per-capita flood damage over time. And we’ve shown that in a bunch of our studies and our books.
So mitigation works, particularly if it’s done at the local level and it’s done in a hybrid fashion. So it’s a combination of different strategies. It’s not just a wall or just education and warning. It’s all those things together that form local programs and that’s why it’s best done at the local level so you can cater to the different characteristics of the community. When done together and implemented in a genuine way, we’re finding significant reductions in damage.