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Conservation Science for a Healthy Planet

Houston’s flooding shows what happens when you ignore science and let developers run rampant

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Since Houston, Texas was founded nearly two centuries ago, Houstonians have been treating its wetlands as stinky, mosquito-infested blots in need of drainage.

Even after it became a widely accepted scientific fact that wetlands can soak up large amounts of flood water, the city continued to pave over them. The watershed of the White Oak Bayou river, which includes much of northwest Houston, is a case in point. From 1992 to 2010, this area lost more than 70% of its wetlands, according to research (pdf) by Texas A&M University.

In the false-color satellite images below, plants and other vegetation appear green, while urbanized and developed areas appear blue and purple. Drag the slider to see how northwest Houston has changed since 1986.

….In recent days, the flooding caused by Hurricane Harvey has raised water levels in some parts of the watershed high enough to completely cover a Cadillac. The vanished wetlands wouldn’t have prevented flooding, but they would have made it less painful, experts say….

….Between 1992 and 2010 alone nearly 25,000 acres (about 10,000 hectares) of natural wetland infrastructure was wiped out, the Texas A&M research shows. Most of the losses were in Harris County, where almost 30% of wetlands disappeared.

Altogether, the region lost the ability to handle nearly four billion gallons (15 billion liters) of storm water. That’s equivalent to $600 million worth of flood water detention capacity, according to the university researchers’ calculations.

To be sure, that’s a drop in the bucket of what Harvey will eventually unleash. The estimate was already at nine trillion gallons a couple of days after the storm made landfall. But saving and restoring wetlands is nonetheless an important part of making Houston more storm resistant, says Mary Edwards, a wetlands specialist at Texas A&M’s AgriLife Extension.

…It’s not just wetlands that are being destroyed. Prairies, which also act as floodwater sponges, have been decimated too. Below, maps show the change in the Katy Prairie, west of downtown Houston. By 1996, much of it was gone, but another 10% had been lost by 2010, while the developed acreage grew by 40%, data from HARC shows….

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