Justin Fox: Making 500-year storms happen every year

Justin Fox is a Bloomberg View columnist.

Here’s a bit of Houston history for you, courtesy of the Harris County Flood Control District: When the Allen brothers founded Houston in 1836, they established the town at the confluence of Buffalo and White Oak Bayous. Shortly thereafter, every structure in the new settlement flooded.

 

And so things continued for the next century:

Harris County suffered through 16 major floods from 1836 to 1936, some of which crested at more than 40 feet, turning downtown Houston streets into raging rivers.

In 1937, the flood control district was founded. Together with the U.S. Army Corps of Engineers it set to work building dams and deepening channels to keep floodwaters away from downtown Houston and residential neighborhoods throughout the county. For more than half a century, these efforts succeeded in preventing region-wide floods — although there were certainly some terrible local ones, like the 1994 rainfall that devastated areas north of Houston.

Then, in 2001, came Tropical Storm Allison, a “500-year storm” that dumped more than two feet of rain on the area and flooded 73,000 homes. More recently there were the paralyzing Memorial Day floods of 2015 and Tax Day floods of 2016, also “500-year” events by some standards. And now the soggy remnants of Hurricane Harvey, which have already generated at least a 500-year-flood, and maybe a 1,000-year one.

So either Houston has been desperately unlucky lately, or something has changed to sharply increase the likelihood of epic floods.

One much-discussed potential culprit is global warming, which while it hasn’t clearly increased the frequency of tropical storms, does appear to be bringing periods of much more intense rainfall. By causing sea levels to rise, it’s also raising the risk from hurricane storm surges, although that hasn’t been the issue with Harvey and Houston.

A far more dramatic change, though, is that in 1940, when organized flood control efforts were just getting going, there were 528,961 people in the Houston metropolitan area. Now there are 6.8 million. That not only means millions more houses to flood, but also fewer places for water to soak harmlessly into the ground. Just between 1996 and 2011, estimates marine science professor Sam Brody of Texas A&M University at Galveston, the Houston area saw a 25 percent increase in the area covered by impervious surfaces such as buildings and pavement.

This argument — that the Houston area has built its way into recurring disaster — is still pretty controversial in a place where development is gospel. As the outgoing head of the flood control district, Mike Talbott, told the Texas Tribune and ProPublica last summer, the idea that “these magic sponges out in the prairie would have absorbed all that water is absurd.”

But something is different. As the 2016 Texas Tribune/ProPublica series in which his quote appeared documented, neighborhoods in and around Houston that never flooded before are flooding now. Successfully reducing the risk of floods after 1937 enabled the Houston area to boom so spectacularly that the flood-risk-management measures that worked from 1937 to 2000 just aren’t doing the trick anymore.

This is the point where, as a card-carrying East Coast opinion merchant, I’m supposed to shake my head disapprovingly about people choosing to live in a sprawling, freeway-laced city built on boggy flatlands abutting a hurricane-prone sea. But all big cities are nature-defying creations, and Houston’s build-first-ask-questions-later approach to development has in some ways been its greatest economic strength. It has produced a gloriously vibrant, diverse, inventive, adaptable metropolis.

Now comes another opportunity for adaptation. In 1937 Houston and Harris County figured out a way to keep floods from thwarting their growth. They and surrounding counties are going to have to do it again. This time political advances (revamping flood insurance, reclaiming green space and so on) seem at least as important as technical ones — and political advances are usually much harder. Still, figuring out new ways to grow is what Houston does. Don’t count it out.

Justin Fox is a Bloomberg View columnist.

 

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