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How the city's development may have contributed to devastating flooding

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Houston calls itself “the city with no limits” to convey the promise of boundless opportunity. But it also is the largest U.S. city to have no zoning laws, part of a hands-off approach to urban planning that may have contributed to catastrophic flooding from Hurricane Harvey and left thousands of residents in harm’s way.

Growth that is virtually unchecked, including in flood-prone areas, has diminished the land’s already-limited natural ability to absorb water, according to environmentalists and experts in land use and natural disasters. And the city’s drainage system — a network of reservoirs, bayous and, as a last resort, roads that hold and drain water — was not designed to handle the massive storms that are increasingly common.

Certainly, the record-shattering rainfall on Houston and its surrounding area this week would have wreaked havoc even if stricter building limits and better runoff systems were in place. And local officials have defended the city’s approach to development.

People walk through floodwater near Interstate 10 in Houston on Sunday. Rising water from Hurricane Harvey pushed thousands of people to rooftops and other higher ground. (Jabin Botsford/The Washington Post)

But the unfolding disaster — at least 22 people are dead and 30 percent of Harris County, which includes Houston, is underwater — is drawing renewed scrutiny to Houston’s approach to city planning and its unique system for managing floodwater.

“You would have seen widespread damage with Harvey no matter what, but I have no doubt it could have been substantially reduced,” said Jim Blackburn, co-director of Rice University’s research center on severe storm prediction and disaster evacuation.

Over many years, officials in Houston and Harris County have resisted calls for more stringent building codes. Proposals for large-scale flood-control projects envisioned in the wake of Hurricane Ike in 2008 stalled. City residents have voted three times not to enact a zoning code, most recently in 1993.

Rather than impose restrictions on what property owners can do with their land, Houston has attempted to engineer a solution to drainage. The region depends on a network of bayous — slow-moving streams that run east into Galveston Bay — and concrete channels as the main drainage system. Streets and detention ponds are designed to carry and hold the overflow.

In previous public comments, the leaders of the Harris County Flood Control District have rejected the idea that the city’s growth is responsible for massive flooding. They also have disputed the scientific assessments. Those officials were not available this week.

Bill St. John, a retired civil engineer and former project manager for the district, said in an interview: “There are people who would turn around and say there needed to be stronger rules and regulations. And in hindsight, it’s real easy to say that. But the rules and regulations were what they needed to be at the time. There was no scientific proof it needed to be stronger at the time, so it wasn’t.”

HOUSTON IS ON SOME OF THE U.S.’S LEAST ABSORBENT SOIL Permeability rating of soil 0.1 or less Over 1 Houston Source: U.S. Geological Survey, 1995 HOUSTON IS ON SOME OF THE NATION’S LEAST ABSORBENT SOIL Permeability rating of underlying soil 0.1 or less Over 1 Seattle Boston New York Chicago San Francisco Washington Los Angeles Atlanta Dallas Houston New Orleans Miami Source: U.S. Geological Survey, 1995 HOUSTON IS ON SOME OF THE NATION’S LEAST ABSORBENT SOIL Permeability rating of underlying soil 0.1 or less Over 1 Seattle Boston Detroit New York Philadelphia Chicago San Francisco Washington Los Angeles Phoenix Atlanta Dallas Houston Orlando New Orleans Tampa Bay Miami Source: U.S. Geological Survey, 1995 data

But in a city built on a low-lying coastal plain, on “black gumbo,” clay-based soil that is among the least absorbent in the nation, many experts say those approaches no longer suffice. They say that new homes should be elevated and that construction should be prohibited in some flood-prone areas.

Since 2010, at least 7,000 residential buildings have been constructed in Harris County on properties that sit mostly on land the federal government has designated as a 100-year flood plain, according to a Washington Post review of areas at the greatest risk of flooding. Some other cities also allow building in flood plains, with varying degrees of regulation.

“Houston is the Wild West of development, so any mention of regulation creates a hostile reaction from people who see that as an infringement on property rights and a deterrent to economic growth,” said Sam Brody, director of the Center for Texas Beaches and Shores at Texas A&M University. “The stormwater system has never been designed for anything much stronger than a heavy afternoon thunderstorm.”

Cars sit in floodwater along Interstate 45 in Houston on May 29, 2015, after heavy overnight rain flooded parts of the highway. (David J. Phillip/Associated Press) Chance Morgan canoes past flooded townhouses in the Forest Cove neighborhood on June 2, 2016, as he tries to get to his home near Kingwood, Tex. (Michael Ciaglo/Houston Chronicle via Associated Press)

At the same time, severe storms are becoming more frequent, experts said. The city’s building laws are designed to guard against what was once considered a worst-case scenario — a 100-year storm, or one that planners projected would have only a 1 percent chance of happening in any given year. Those storms have become quite common, however. Harvey, which dumped up to 50 inches of rain in some places as of Tuesday afternoon, is the third such storm to hit Houston in the past three years.

In May 2015, seven people died after 12 inches of rain fell in 10 hours during what is known as the Memorial Day Flood. Eight people died in April 2016 during a storm that dropped 17 inches of rain.

Like other coastal areas, Houston and its surrounding areas have repeatedly turned to federal taxpayers for help rebuilding.

Harris County has received about $3 billion from the Federal Emergency Management Agency for losses in the past four decades, federal data show. It ranks third in the amount paid by the National Flood Insurance Program, behind Orleans and Jefferson parishes in Louisiana, which sustained significant damage during Hurricane Katrina in 2005.

An overhead view of the flooding in Houston, from Buffalo Bayou on Memorial Drive and Allen Parkway, is seen as heavy rain continued to fall on Monday in Houston, which is still largely paralyzed. (Karen Warren/Houston Chronicle via Associated Press)

In the 1940s, the Army Corps of Engineers built two massive reservoirs that serve as holding areas during big downpours. In the following decades, the city carved out additional concrete channels and lined bayous with pavement to shunt water away.

“The system is dependent on bayous that have been there forever and had a certain capacity,” said Gerry Galloway, a professor of civil engineering at the University of Maryland and a visiting professor at Texas A&M. “Over the years, that was probably a reasonable way to deal with this. As the city grew, and there was more development, there was less and less capacity to carry the runoff.”

Houston’s population climbed to 2.2 million in 2015, a 25 percent increase from 1995. Harris County had an even bigger bump over that time, 42 percent, and now has 4.4 million residents. As the population grew, the city expanded, covering fallow land that had served as a natural sponge.

Between 1992 and 2010, 30 percent of the surrounding county’s coastal prairie wetlands were paved over, according to a 2010 report from Texas A&M.

Projects to widen the bayous and build thousands of retention ponds for excess water have not kept pace with the new rooftops, roadways and parking lots needed to accommodate about 150,000 new residents a year, experts say. As a backup, roads were built below grade and designed to take on excess water when storm drains overflow.

THE EDGE OF HOUSTON HAS ADDED A LOT OF CONCRETE Developed impermeable surfaces in greater Houston Impermeable surfaces as of 2011 Added between 1996 and 2010 HOUSTON 10 MILES Sources: NOAA, U.S. Geological Survey THE EDGE OF HOUSTON HAS ADDED A LOT OF CONCRETE Developed impermeable surfaces in greater Houston Impermeable surfaces As of 2011 Added between 1996 and 2010 Lake Houston HOUSTON Galveston Bay 10 MILES Sources: NOAA, U.S. Geological Survey THE EDGE OF HOUSTON HAS ADDED A LOT OF CONCRETE Developed impermeable surfaces in greater Houston Impermeable surfaces As of 2011 Added between 1996 and 2010 Lake Houston HOUSTON Galveston Bay 10 MILES Sources: NOAA, U.S. Geological Survey

“The philosophy was: Wouldn’t you rather have water in the street than in your house?” said D. Wayne Klotz, a water resources engineer and senior principal at RPS Klotz Associates and a former national president of the American Society of Civil Engineers.

When the streets fill up, though, evacuation becomes more difficult.

In the days before Harvey struck, city officials urged residents to stay put. On social media, local officials knocked down predictions that as many as 50 inches of rain were expected — reports that overstated the forecast at the time but turned out to align more closely with the eventual rainfall.

When the rain came, roads turned into waterways, requiring door-to-door boat rescues.

In many areas of the city, especially the older parts, water that breaches the roadways flows into homes that sit on ground-level slabs. Blackburn said that requiring higher elevations of homes in flood-prone areas — the current requirement is one foot above the level of a “100-year storm” — would have stemmed the losses from Harvey and past storms.

John Jacob, director of the Texas Coastal Watershed Program and a professor at Texas A&M, said he was particularly incensed to hear about a nursing home in Dickinson, southeast of Houston, where residents in wheelchairs were sitting in waist-deep water. They were rescued after photos of them went viral on social media.

Residents of the La Vita Bella nursing home in Dickinson, Tex., sit Sunday in waist-deep floodwater caused by Hurricane Harvey. After this photo went viral, all of the residents were removed from the facility. (Trudy Lampson/Associated Press)

“That should never have been built,” Jacob said of the nursing home that sits across the street from the floodplain boundary. “We’re putting people in harm’s way.”

Jacob lives in a neighborhood east of downtown called Eastwood that he said was spared from flooding damage because many lots are above street level, and homes have been built on “pier and beam” foundations that include a crawl space of a few feet. That adds thousands of dollars to the cost and isn’t required by city or county building codes.

All of Harris County’s 34 municipalities have their own plans for addressing flooding issues whose causes and solutions extend beyond borders.

“There never has been a comprehensive plan that considered all the area that would affect Houston,” Galloway said.

Last year, the state’s high court dismissed a class-action lawsuit brought by 400 Harris County homeowners who suffered flood damage three times in five years — during Tropical Storm Frances in 1998, Tropical Storm Allison in 2001, and an unnamed storm in 2002.

The county argued in court that it had spent tens of millions of dollars on flood control and disputed the homeowners’ claim that developers had free rein. A majority of the court agreed, saying residents failed to directly link development in one part of the watershed with flooding in their particular homes.

“Even by the homeowners’ reckoning the flooding resulted from multiple causes,” the court found, including “acts of God.”

Helicopters drop off people they have rescued on Highway 69 in Houston on Monday. (Jabin Botsford/The Washington Post)

Aaron C. Davis, Jack Gillum and Andrew Tran contributed to this report.