Things get bad when Houston floods. Water swamps homes, takes lives and shuts down the city. But it should be so much worse. There shouldn't even be a city here.

But there is, and most Houstonians casually accept the enormous drainage system—the bayous, creeks and gullies—that keep it precariously dry in a former wetland.

Early settlers drained marshes to build Houston town in a muddy bog. Fast forward less than 200 years and the city stands above water, mostly, thanks mostly to 2,500 miles of managed waterways—the flying distance from Houston to Quito, Ecuador—that whisk the floods out to sea.

"If those channels didn't exist, this area would be flooding from every rain, not just the big ones," said Mike Talbott, executive director of the Harris County Flood Control District. "A very large percentage of the systems have not been made larger to meet current criteria."

Therein lies the problem. Tremendous rains this year and last pushed the limits, forcing gullies and bayous over their banks into neighborhoods that brim them. The only solution is to widen the waterways, which means buying up adjacent buildings and tearing them down. Talbott puts the price tag on a total upgrade at $26 billion, which will not happen soon.

The weather is outpacing Harris County's effort to tame, and according to scientists it's not going to stop. Citing his own research, state climatologist John Nielsen-Gammon said extreme rainfall events have increased in Texas over the past century, with a particularly large increase in Houston.

RELATED: State climatologist: Houston rains are getting worse

When the rains hit, they often hit harder than they used to. And the trend isn't expected to abate.

Nature is ignoring the occupation that Talbott is tasked with preserving. It's an old game for Houston. The city's past was built on drainage and its future will be too. It's just hard to imagine how.

City in the mud

Inundation is nothing new here. Right from the start, it took tremendous effort and loss of life to claim the Houston area from the prevailing floods.

O.F. Allen, an early settler and nephew of a Houston founder, wrote of his experience in the infant city:

"Once could hardly picture the jungle and swampy woods that a good portion of the city is built upon. These swampy grounds had to be cleared and drained. The writer himself quite clearly remembers that the southwestern portion of the city was a green scum lake, studded with giant sweet gum trees, and water from one to two and a half feet deep... The labor of clearing the great space was done by negro slaves and Mexicans, as no white man could have worked and endured the insect bites and malaria, snake bites, impure water, and other hardships. Many of the blacks died before their work was done."

That was just the beginning, and the labor by no means left the city dry. When famed naturalist John Audubon visited in 1837, he marveled that he approached President Sam Houston's cabin "wading in water above our ankles."

Where there wasn't water there was mud—mud that early settlers joked you could lose a horse in, that swallowed any attempt to build a road and bred clouds of disease-bearing mosquitoes. It was so bad that lawmakers primarily cited the mud in their decision to move the capital to Austin.

But occasionally Houston went from saturated to inundated. William Taylor, born in Houston in 1863, wrote of driving a ferry "from the foot of Main Street to Fifth Ward during the worst of the flood" of 1879, which lasted several days.

Floods were so common they merit only casual mentions in Houston's early history. Like how the Houston Electric Company built a dam and artificial lake on Little White Oak Bayou in 1904, but rains later that year washed it away.

If the region would ever host a metropolis, the floods would clearly have to be tamed.

An endless quest to tame the inundations

In Houston, the notion of large-scale publicly funded drainage infrastructure emerged in a 1908 plan by engineer George Horton. Citizens successfully petitioned the county to fund the plan and "render habitable" a small portion of southwest Harris County.

"I have seen several hundred acres underwater for days after large rains," Horton wrote (see page 25 below). "A complete system of drainage will do away with such cases as this... It will be the making of this section of the country."

Crews widened bayous, straightened their paths, eased their curves and ripped away logs that resisted their flow. Where there was a lack of natural waterways, they dug 44 miles of new channels.

In the decades since, similar endeavors appeared across the county, but they weren't nearly enough.

The worst rain the city remembered fell in 1929, and a worse one struck in 1935. Buffalo Bayou rose up to the second story in parts of downtown. Buildings collapsed. Swaths of city were destroyed.

PHOTOS: The Houston flood of '35

So in 1937 a coalition of local authorities petitioned the state to commission a flood authority that could work with the U.S. Army Corps of Engineers to orchestrate large-scale upgrades in Houston, and the Harris County Flood Control District was born of dire need.

Through the '40s and '50s, the USACE and HCFCD modernized Houston drainage. They drastically widened Brays and Buffalo bayous and concrete-lined some waterways. They built the Addicks and Barker reservoirs to catch rains that fell on the Katy Prairie and keep them from downtown.

In the '60s and '70s other dramatic upgrades were made.

As the city expanded, canals were built to drain new neighborhoods, and homes soon lined the banks of every gully, creek and stream. Much of the system was locked in without room to grow, though it was already massively expansive.

"It was unbridled urban sprawl without a whole lot of attention to what they should have been doing for correct urban drainage. There were a lot of mistakes made in those years," said Phil Bedient, a veteran professor of civil engineering and urban flood control at Rice University. "Now we find ourselves in a situation where we inherited this problem."

Evolving standards, static system

Houston got stuck with a huge but outdated system. Mid-century engineers didn't anticipate two important things: how bad the rains could get and how much urbanization would exacerbate the floods.

Later in the 20th century, understanding evolved with science. Federal floodplain mapping in the 1970s provided the first insight to where the water actually pools during torrential downpours.

Then computer models in the 1980s began to describe just how big those torrential downpours could get. That's when Talbott got involved. He got an engineering degree from Texas A&M University, an MBA from the University of Houston then joined the district in 1982 and never left.

Harris County flood control, he said, is his "one and only career."

He had an early hand in computer models of the flood threat at a time when scientists were awakening to a notion: weather runs in massive cycles, and every so often a monster storm hits.

The old system was built to drain the city's common floods, not to save it from the once-in-century deluge that could fall in any year.

"A lot of engineering was done before people understood the risks," Talbott said.

From the start, Talbott realized the enormous amount of work that remained to prepare for the big one. That, he said, is why he stayed around so long.

During his 35 years with the district he's labored on the colossal effort that may save the city when the great flood comes. They've widened some bayous, built dozens of new reservoirs and enacted policies requiring new subdivisions to build their own.

It amounts to solid progress. But today, Talbott said, the challenges facing the district seem as steep as ever.

No room to grow

Urban saturation put tremendous unanticipated strain on the drainage system. Where water used to sift slowly through thick grass and gullies, it tumbled off rooftops, into gutters, onto driveways then down the street to the waterway, which can receive the full fury of the storm condensed in its banks within an hour of the storm.

The surge comes too quickly for the waterways to handle, and they overflow, even during rains of a magnitude they were built to handle. The only solution is to build them bigger, but it can't easily be done.

Beneath a bridge on Mangum Road in northwest Houston, Talbott pointed out an approximately 100-foot wide concrete-lined Brick House Gully that drains about 10 square miles of cityscape into White Oak Bayou. It's no wider than it was in 1950, and it won't be expanded any time soon, even in spite of floods.

Back yards of homes and apartment complexes abut right up against the concrete lining of the waterway.

"They're pretty much all like that," Talbott said. "There's always a last row of lots that shouldn't have been built.

"I wish someone would have told us that 100 years ago," he said.

Intensifying rainfall

The system is already stressed, it can't easily grow, and it gets worse: the rains are getting harder.

"We've confirmed that there's an overall increase in extreme rainfall in Texas over the past century," said state climatologist John Nielsen-Gammon, citing his own unpublished research. "Specifically for Houston the increase has been particularly large."

Counties surrounding Houston don't exhibit the same trend, Nielsen-Gammon said, but the phenomenon has long been predicted by climate models and has been observed in the nation as a whole.

An independent review of more than 100 years' of Houston rainfall records showed the same—that the heaviest rains are skewed towards recent decades.

RELATED: 2015 becomes Texas' wettest year on record

Jeff Lindner, chief meteorologist for the HCFCD, pointed out three statistical anomalies in local rainfall: Tropical Storm Claudette in 1979, Allison in 2001 and the Tax Day flood in 2016.

"These would all be considered once-in-a-lifetime, off-the-charts rainfall and we've had it thrice in 37 years," he said.

In a region straddling Harris and Waller counties, the Tax Day storms approached a scale of rainfall that Lindner said the region should expect once in a thousand years.

"We're starting to get into a lot of estimation in those numbers, but clearly anything in that region would exceed the targets of our [flood drainage system] design," he said.

Brays Bayou, which has been widened in recent decades, surged over its banks in several spots, spilling feet of water into adjacent neighborhoods.

"In modern times, as long as we've been keeping rainfall records, we never had close to this amount of rain out there [in Brays Bayou]," Lindner said.

There is no single cause for the increase in torrential downpours, but long before the trend was observed, scientists theorized it would accompany a warming climate because warm air holds more water that plummets to Earth when pressure systems yield a storm. Houston seems poised for a dry spell ahead (barring tropical storms), but the long term shift towards intensified rains is expected to continue.

So what can Houston do to contain them?

Solutions

One thing is for sure: Houston's prosperous future depends largely on its ability to keep the floods at bay, especially the great one that could fall in any year.

The drainage system does an excellent job by relegating floods to a small portion of a region that would otherwise be entirely underwater. But modern expectations call for total mitigation of the threat.

RELATED: Talbott: Floods remind us of the work ahead

Talbott has a simple solution: allocate $26 billion, more than a fifth of the state's 2015 budget, mostly to buy property adjacent to the waterways, bulldoze and expand the canals. That amount of money, he said, could get all of Houston prepared to weather a city-wide, once-in-a-century storm.

"I'm surprised we haven't dug new bayous," said Ron Sass, a veteran climate researcher at Rice University. "You know, tear down some houses. We build freeways. I would think that a bayou would be as important to our infrastructure as a freeway."

Chris Bell, a former Houston city councilman, mayoral candidate and congressman, led the effort to win $53 million in federal appropriations for local flood control in 2004 in the wake of Tropical Storm Allison. The Memorial Day and Tax Day floods left several feet of water in his Meyerland home, and he said neighbors have been wondering aloud whether a buyback program is in order.

But he said the city would not be raising $26 billion any time soon.

Carroll Robinson, a former Houston city councilman and current professor of public policy at Texas Southern University, said the city couldn't afford to delay needed projects until the funds come in.

"The city should literally issue debt so it can bring forward flood control projects," he said, noting that debt is issued to fund parks and sewers. "On a pay-as-you-go basis you just can't build and maintain projects fast enough."

He also suggested forming a regional flood control district with surrounding counties or requiring new homes in flood-prone places to build like beach houses on stilts.

But Houston is already stuck with tremendous debt, such that Moody's Investors Service downgraded its bond rating in March. Issuing more debt would be a very tough sell.

Talbott said that no substantial chunk of the billions of dollars to retrofit Houston would come from the federal government.

"It just wouldn't fit in their model of benefits and costs," he said.

A few years ago the city levied a flood drainage fee, which could bring in several billion dollars in the coming decades. Bell pointed out that a $500 million revamp of Brays Bayou has kept the Medical Center above water ever since it flooded in 2001. That, he said, was a sign of hope.

"We've seen amazing engineering solutions throughout history," he said. "We have a lot of bright minds in Houston. I do think that there are engineering solutions to this problem."

It will probably just be extremely expensive.