Houston’s Growth at any Cost Makes Floods Inevitably Worse

You’d think nobody ever watched “Jaws”.

Texas Tribune:

The area’s history is punctuated by such major back-to-back storms, but many residents say they are becoming more frequent and severe, and scientists agree.

“More people die here than anywhere else from floods,” said Sam Brody, a Texas A&M University at Galveston researcher who specializes in natural hazards mitigation. “More property per capita is lost here. And the problem’s getting worse.”

Why?

Scientists, other experts and federal officials say Houston’s explosive growth is largely to blame. As millions have flocked to the metropolitan area in recent decades, local officials have largely snubbed stricter building regulations, allowing developers to pave over crucial acres of prairie land that once absorbed huge amounts of rainwater. That has led to an excess of floodwater during storms that chokes the city’s vast bayou network, drainage systems and two huge federally owned reservoirs, endangering many nearby homes — including Virginia Hammond’s.

On top of that, scientists say climate change is causing torrential rainfall to happen more often, meaning storms that used to be considered “once-in-a-lifetime” events are happening with greater frequency. Rare storms that have only a miniscule chance of occurring in any given year have repeatedly battered the city in the past 15 years. And a significant portion of buildings that flooded in the same time frame were not located in the “100-year” floodplain — the area considered to have a 1 percent chance of flooding in any given year — catching residents who are not required to carry flood insurance off guard.

Scientists say the Harris County Flood Control District, which manages thousands of miles of floodwater-evacuating bayous and helps enforce development rules, should focus more on preserving green space and managing growth. The City of Houston, too. And they say everyone should plan for more torrential rainfall because of the changing climate. (A host of cities in the U.S. and around the world are doing so.)

But county and city officials responsible for addressing flooding largely reject these arguments. Houston’s two top flood control officials say their biggest challenge is not managing rapid growth but retrofitting outdated infrastructure. Current standards that govern how and where developers and residents can build are mostly sufficient, they say. And all the recent monster storms are freak occurrences — not harbingers of global warming or a sign of things to come.

The longtime head of the flood control district flat-out disagrees with scientific evidence that shows development is making flooding worse. Engineering projects can reverse the effects of land development and are doing so, Mike Talbott said in an interview with The Texas Tribune and ProPublica in late August before his retirement after 18 years heading the powerful agency. (His successor shares his views.)

The claim that “these magic sponges out in the prairie would have absorbed all that water is absurd,” Talbott said.

He also said the flood control district has no plans to study climate change or its impacts on Harris County, the third-most-populous county in the United States.

Of the astonishing frequency of huge floods the city has been getting, he said, “I don’t think it’s the new normal.” He also criticized scientists and conservationists for being “anti-development.”

“They have an agenda … their agenda to protect the environment overrides common sense,” he said.

But Talbott acknowledged that projects in the works wouldn’t come close to protecting against something like a Tax Day flood. Those include retrofitting old drainage, widening bayous and building more ponds to temporarily store floodwater.

Eric Holthaus in Politico:

Houston has been sprawling out into the swamp for decades, largely unplanned and unzoned. Now, all that pavement has transformed the bayous into surging torrents and shunted Harvey’s floodwaters toward homes and businesses. Individually, each of these subdivisions or strip malls might have seemed like a good idea at the time, but in aggregate, they’ve converted the metro area into a flood factory. Houston, as it was before Harvey, will never be the same again.

Harvey is the third 500-year flood to hit the Houston area in the past three years, but Harvey is in a class by itself. By the time the storm leaves the region on Wednesday, an estimated 40 to 60 inches of rain will have fallen on parts of Houston. So much rain has fallen already that the National Weather Service had to add additional colors to its maps to account for the extreme totals.

Harvey is infusing new meaning into meteorologists’ favorite superlatives: There are simply no words to describe what has happened in the past few days. In just the first three days since landfall, Harvey has already doubled Houston’s previous record for the wettest month in city history, set during the previous benchmark flood, Tropical Storm Allison in June 2001. For most of the Houston area, in a stable climate, a rainstorm like Harvey is not expected to happen more than once in a millennium.

In fact, Harvey is likely already the worst rainstorm in U.S. history. An initial analysis by John Nielsen-Gammon, the Texas state climatologist, compared Harvey’s rainfall intensity to the worst storms in the most downpour-prone region of the United States, the Gulf Coast. Harvey ranks at the top of the list, with a total rainwater output equivalent to 3.6 times the flow of the Mississippi River. (And this is likely an underestimate, because there are still two days of rains left.) That much water—20 trillion gallons over five days—is about one-sixth the volume of Lake Erie. According to a preliminary and informal estimate by disaster economist Kevin Simmons of Austin College, Harvey’s economic toll “will likely exceed Katrina”—the most expensive disaster in U.S. history. Harvey is now the benchmark disaster of record in the United States.

As with Katrina, Harvey gives us an opportunity for an inflection point as a society. The people of Houston didn’t choose this to happen to them, but what happens next is critically important for all of us.

Washington Post:

Hurricane Harvey has brought “500-year” rainfall and flood conditions to the Houston area, according to officials at the Harris County Flood Control District.

By the time the storm finally leaves the Houston area the true magnitude may be even greater than that, surpassing 1,000-year thresholds — potentially even more.

But 500-year floods, as it turns out, happen more frequently than you might expect. The Houston area alone has seen no fewer than three such events in the past three years, according to local officials: Memorial Day floods in 2015 and 2016, followed by Hurricane Harvey’s torrential rains this year.