How Houston’s layout may have made its flooding worse
(CNN) — Tropical Storm Harvey, which has flooded thousands of Houston-area homes, is serving up a hard lesson for city planners in Texas.
Experts say better urban design and stricter regulations might have made the deadly storm less destructive.
“Houston is not designed to handle this kind of rainfall,” said Professor Sam Brody, an expert on urban and floodplain management at Texas A&M University.
It’s not like the nation’s fourth-largest city isn’t aware of the problem. Tropical Storm Allison triggered mass flooding and caused 20 Texas deaths in 2001. Last April, storms in Houston flooded more than 1,000 homes and were blamed for $5 billion in property damage.
But longtime Houston residents say the flooding from Harvey is the worst they’ve ever seen.
“The water didn’t come in as much … last time,” said Maralyn Rice, who has lived in the city for 37 years. “This one here, this is much worse. I told my daughter, ‘We’re going to move on.’ I’m not coming back no more.”
No amount of planning can completely prevent a disaster like Harvey, which dumped an unprecedented 50 inches of rain on parts of Texas in less than four days. But experts in floodplain and storm water management say its damage could have been lessened if authorities in Houston had paid more attention in recent years to three big factors:
1. Urban sprawl
The rapid growth of strip malls and housing developments has turned Houston — and many other areas of America — into concrete jungles.
Houston has seen a 23% population increase since 2001, Brody said, including 100,000 new residents last year alone. Harris County, where much of Houston is located, saw the construction of nearly 360,000 new buildings from 2000 to 2015, according to the Houston Chronicle.
Throughout the Houston metro area, decades of virtually unplanned growth has resulted in thousands of square miles of paved streets, parking lots and other hard surfaces covering the ground. According to the city’s website, its metro area measures nearly 9,000 square miles — an area larger than New Jersey.
All this concrete makes it harder for stormwater to be absorbed naturally into the ground. And Houston is more spread out than many other cities, said Bruce Stiftel, who chairs Georgia Tech’s School of Regional and City Planning.
“When you have a less dense urban fabric, you’re going to have more impervious surface and you’re going to have more runoff,” Stiftel said. “That’s clearly an important consideration in Houston.”
Brody said, “Houston has done a wonderful job since (Allison in) 2001, but now I wonder if we should do more than focus on pipes.”
Brody believes Houston should put more focus on water management in broader terms. City planners, he said, should think more about how development in one region affects water runoff in another.
And some areas probably shouldn’t be considered for new construction at all, he said.
2. Weak rules and regulations
Houston is a low-lying city in a coastal floodplain that’s a frequent target for Gulf hurricanes. And yet its policies underestimate the potential hazards of flooding, experts say.
“Houston is somewhat legendary for having no real zoning,” said Chad Berginnis, executive director of the Association of State Floodplain Managers. “That’s important because zoning allows local agencies to say, ‘look these are inappropriate uses for building in these areas.'”
Many places across the nation have requirements for how high above the ground homes and businesses should be built — to protect against possible flooding. They create what’s called a freeboard — the distance a building must be built above the level of the highest flood that occurs every 100 years.
Much of Houston has a 1-foot freeboard, Berginnis said. But urban areas with poor drainage are not accounted for, he said. And maybe a 1-foot freeboard isn’t high enough, Berginnis said.
Brazoria County, south of Houston’s city limits, adopted a 2-foot freeboard in 2007.
Or consider Nashville, Tennessee, which has a freeboard of 4 feet. Nashville has mandated that level for residential properties since 1979, said Roger Lindsey, a Nashville storm water and floodplain manager. The added freeboard helped prevent additional damage to many homes during the city’s floods in 2010, he said.
After Allison, critics in Houston complained unsuccessfully that detention ponds designed to collect rain weren’t big enough.
“We need to ask what decisions could have been made during Allison and the 2016 floods,” Brody said.
Nationwide, storm water standards in terms of flooding “are very patchwork,” said Berginnis. There are higher standards that local communities could adopt to protect themselves, he said, including specific limits against building too close to bayous or creeks.
Earlier this year, Rod Pinheiro, director of Houston’s Storm Water Maintenance Branch, wrote that certain areas developed before 1985 were prone to flooding because of “inadequate and undersized infrastructure.”
In January, the Houston city council approved $10 million in initial funding to reduce drainage problems along three of its bayous.
“These projects will greatly reduce the flood threat for residents along these bayous and remove hundreds of properties out of the 100 year flood plain,” Mayor Sylvester Turner said at the time.
In January, Pinheiro said the money would be used to replace storm sewer and outfall pipes, regrade ditches, replace culverts and other repairs.
Pinheiro did not respond to repeated requests for comment this week on Houston’s storm water infrastructure.
Stiftel said he doesn’t think any city “could have fully been prepared to prevent the serious consequences of a storm of this magnitude.” In general, he said, cities are not designed to handle the volume of rain that Houston has had this week.
“It would just be impossible to put in place a reliable system to handle that much water,” he said.
Nonetheless, Stiftel said he was “confident” that Houston officials “could have done much better than they’ve done.”
3. Poor reservoir and land management
On Monday, the US Army Corps of Engineers started releasing water from the Addicks and Barker dams in west Houston. Officials said it was safer for nearby neighborhoods to manage the water with controlled releases instead of letting uncontrolled water flow over the edge of the dams.
The dams control the flow of water into Buffalo Bayou, a winding Houston river surrounded by residential areas.
Harris County flood control officials now estimate at least hundreds of structures have water in them as a result of the release across the two dams.
The larger question for planning experts was: Why were there homes and businesses in the path of that released water? The dams were built in the 1930s, long before many of the homes and businesses in the water’s path.
For Brody, it’s an example of how the lack of long-term planning on a broader level can have disastrous consequences.
“We need a broader strategy that protects areas with natural infrastructure like wetlands, which are still the best system we have to hold, store and slowly release floodwaters,” he said.
Obviously making changes after Allison in 2001 wouldn’t have saved all properties from Harvey’s floods, but it might have prevented some damage, Brody said. “More planning, I think, would have really reduced the impact,” he said.
The disaster in Houston, he said, proves that urban flooding is becoming a national problem. “These issues are just getting worse,” Brody warned.
As far as solutions are concerned, Stiftel of Georgia Tech takes the long view.
“I wish that as a society we paid more attention to projections about the future and thought about issues like natural hazards from a community point of view,” he said. “I wish we tried to build our cities in a way that anticipated these problems.”