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flood tunnels

More on flood tunnels

They’re a thing, I swear.

Japanese flood tunnel

While it’s far from clear whether it will ever happen, the concept almost immediately generated widespread response when it was announced earlier this spring. Local officials told the Houston Chronicle it’s outside-the-box thinking with benefits that could outweigh the heavy price tag. Residents reading about the project on social media have expressed fears of sinkholes from the underground construction. Even entrepreneur Elon Musk, who owns tunnel construction company The Boring Company, jumped into the conversation on Twitter.

So would such a tunnel system really be a logical solution for Houston’s flood woes?

Drilled 100 to 200 feet underground, the underground channels act as temporary storage for floodwater during intense rainstorms, said Larry Larson, a senior policy adviser at the Association of State Floodplain Managers. Once the rain has stopped, the stormwater can be used for a variety of purposes. It can be pumped back to the surface into a river or wetlands or even used to recharge aquifers.

If cities have a section of river that regularly overflows, a tunnel can convey extra water underground and help reduce the amount of water that flows onto land during storms, said Christof Spieler, project manager of the Greater Houston Flood Mitigation Consortium. Large-scale tunnels can also act as an additional set of waterways, taking pressure off undersized drainage networks, he said.

But Larson and Spieler said it’s hard to tell if such a system would make sense for Houston — a low-lying coastal city that’s experienced three 500-year floods in the past three years.

[…]

Flood control tunnels are nothing new to Texas — San Antonio built the San Pedro Creek Tunnel in 1991 and completed the longer San Antonio River Tunnel in 1997. Austin continues to put the finishing touches on the Waller Creek Tunnel and a tunnel in East Dallas received the long-awaited go-ahead in February.

Should the district choose to pursue the project, tunnels could cost up to $100 million per mile, Steve Costello, the city’s chief resilience officer, told the Houston Chronicle.

See here for the background. There’s a longish and very wonky conversation with Larson and Spieler about flood control, which if you read it you will know is basically an oxymoron, so do read the full article. There wasn’t any mention of other Texas flood tunnels in the earlier article, so I appreciate the Trib bringing those examples. I have a hard time imagining that this will happen here, but as noted the cost of the study is negligible, so why not at least examine the possibility? The worst that can happen is you wind up crossing it off the list.

Flood tunnels

It’s so crazy, it just might work.

Japanese flood tunnel

The Harris County Flood Control District is exploring the possibility of building several massive, deep tunnels aimed at keeping storm water out of flood-prone neighborhoods and carry it underground for miles to the Houston Ship Channel during major storms.

Never before tried around Houston, the project likely would cost several billion dollars and it is not clear where the money would come from, officials said. Specialized machines methodically digging 100 to 200 feet underground would take several years to complete the tunnels, which would seek to drain floodwaters from bayous across the county.

Officials with the flood control district said the idea could be a bold answer to the devastation wrought by Hurricane Harvey, and dramatically improve Houston’s defenses against deadly floods where other strategies have fallen short.

“What the flood control district has been doing for decades doesn’t occur fast enough or it doesn’t have the benefits that the public really wants,” said Matthew Zeve, director of operations at the flood control district. “We’ve been challenged to try to think of new ideas and new strategies and this is an answer to that challenge.”

[…]

A feasibility study is expected to cost around $400,000 and be completed by October.

News of the proposal fueled optimism and skepticism Friday — optimism that Harvey finally could force radical changes to Houston’s flood control strategy, and skepticism that such a monumental project could be accomplished when much less ambitious ideas have languished for decades.

Rep. John Culberson, R-Houston, said in a statement he is “encouraged” the flood control district “is thinking outside the box and plans to conduct a feasibility study on this proposal. It certainly seems like this type of project could be partially funded by FEMA hazard mitigation grants and, perhaps, through other federal sources, as well.”

Houston’s flood czar, drainage engineer and former city councilman Steve Costello, said the project could be a potential paradigm shift for the region’s flood risk.

“We’re trying to lower the risk; we’re never going to be able to totally eliminate the risk,” Costello said, referencing efforts to improve drainage through local projects. “Well, a tunnel system, quite possibly, could eliminate the risk.”

As expensive and complex as it would be – Costello said he was told it could cost perhaps $100 million per mile, in Houston’s soils – he said tunnels may be the most cost-effective way to achieve the gold standard of 100-year storm protection in every major channel.

Jim Thompson, regional CEO for engineering Giant AECOM, said the tunnels are “worthy projects” that warrant further study, but said officials ought to prioritize long-identified projects along bayous and city streets first.

“Would it provide the cure-all relief that everybody is seeking? No,” Thompson said. “Would it provide a noticeable decrease in flood levels and risk of flooding? The answer is possibly yes.”

There’s a connection to Elon Musk in all this, because of course there is. Other cities, like Tokyo, have similar tunnels, so the idea is neither crazy nor unprecedented. But like all things, until and unless there’s a budget and an appropriation, it’s just an idea. Commissioners Court has approved the feasibility study, so we’ll see what they come up with.