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This Storm Has It All'. Hurricane Harvey
Climate Climate Greenhouse gas

Hurricane Harvey is about to slam into Texas this weekend as a Category 4 storm, the first of this magnitude to make landfall in the U.S. in 12 years. Some forecasts are calling for a staggering 40 or more inches of rain, with storm surges cresting between six and 12 feet. In anticipation of the deluge, Texas Governor Greg Abbott declared a preemptive state of emergency and issued orders of evacuationspanning 30 counties. As the storm churns toward land, its precise path—and the destruction its 120-mph winds will leave behind—is somewhat uncertain. But by nearly all accounts, the situation is going to be dire.

The degree to which storms become “disasters” is determined, at least in part, by factors beyond wind speeds or rainfall numbers, as Laura Bliss pointed out in 2016. One major contributor is “how many people and buildings are in the wrong place at the wrong time.” On this front, the situation in Houston could hardly be worse.
As the population has boomed across this Sunbelt city in recent years, an increasing number of people and buildings find themselves in a vulnerable position. Meanwhile, thousands of acres of wetlands that might have helped absorb excess rainfall have been gobbled up by development. When paved surfaces can’t perform the crucial work of stormwater retention, “even lesser storms are invested with more destructive power,” Kriston Capps noted last summer. Harvey is no minor storm—and it is slated to batter a city with relatively poor flood infrastructure and no statewide insurance requirement.

Just how bad will this be? CityLab spoke with Samuel David Brody, director of the Center for Texas Beaches and Shores at Texas A&M Galveston, to find out.

Some meteorologists have sounded blazing alarms about the forecast’s combination of rainfall, wind, and inland flooding. Based on your research, why is this confluence of factors especially threatening?

The storm right now is reminiscent of a storm of 2001 called Tropical Storm Allison. It hit the coast and stalled out and dumped ridiculous amounts of rainfall in the Houston area. So this storm is going to be a surge event down south, with wind and rising seawater, but then a ginormous rain event to the northeast in the Houston area.

How many people lived in Houston in 2001 compared to now? There’s been a 23 percent population increase. There’s been miles and miles of new pavement and structures put in harm’s way. Allison was one of the most devastating storms of all time in the United States. This is going to be much worse, if something with that much rainfall sits over Houston for a couple of days.
This storm has it all. It’s got surge and winds, but for the Houston area, right now the biggest threat is the rainfall. The economic impact and loss of property and human lives could be significant.

In addition to evacuating, what other steps can people take right now to keep themselves and their property safe?

One of the unsung heroes of flood risk reduction techniques is drainage maintenance. It’s not sexy, and it never gets in the news, but I drive around all these neighborhoods in Houston and I see clogged street drains. So when the rains come and they’re filled with trash and debris, it’s like they're not even there. They can’t operate. And then you got a lot of street and home flooding that way. Make sure your drains in the street and on your property are working. Move your valuable contents to the second floor or an attic, if you have one.

Much of your research focuses on urban flooding. How do those conditions differ from a water-related deluge in non-urban areas? Why is the Houston-Galveston area so susceptible to flooding and other water hazards?

The 100-year flood plain is almost nonsense in places like Houston. When we look at insured losses over time, almost half of them are outside the 100-year flood plain. That marker of risk really isn’t capturing reality, because we’ve so altered the natural drainage patterns over time through built environment interventions. That shows up more easily in Houston. It’s so flat, you sneeze and the floodplain changes.
Houston has a large amount of pavement—impervious surface—put down in a very low-lying, flat area that experiences heavy rainfall events. I tell my students that the problem is complicated; there are lots of underlying factors. There are physical conditions. There's environmental change increasing these heavy rainfall events. There’s sea level rise and changing temperatures. All of those are small, slow-moving gears as part of this overall problem. The bigger gear moving much faster is human development—the built environment. Houston added 100,000 people last year alone. That set us up for this potential catastrophe.

Last year, ProPublica reported that development has claimed 75 percent of flood-absorbing land in the Katy Prairie area, which helped manage stormwater. What’s the effect of building on or paving over these types of areas?

I think it’s a combination of lots of different factors, [including] developing the Katy Prairie area, particularly converting those wetlands that store, hold, and slowly release storm water. This is an important part of the problem. It’s the lack of smart development and spatially targeted development that looks at the system—the watershed and the drainage patterns over a large region, not just a specific parcel or set of parcels that will realize short-term economic gain. Over the long term, this creates a drainage pattern that causes homes to be lost and people to die.
In my mind, the story isn’t so much climate change and environmental change—which is real and important. It’s more about the way we've constructed our urban fabric without thinking about building codes and regional development in a systematic way. [This] makes Houston more susceptible to this type of event than any other city in the country.