Consultants propose building underground tunnels to alleviate Clear Creek flooding

To solve drainage issues along Clear Creek, experts working on the Lower Clear Creek and Dickinson Bayou Watershed Study have proposed several potential flood mitigation projects, including building miles of underground tunnels.

At a Nov. 4 meeting to update residents on the progress of the study, consulting firm Freese and Nichols, which is working with League City officials on the study, showed a map detailing 27 potential projects that could help address Clear Creek’s flooding during heavy storms.

Of the 27 projects, eight are storage projects, such as detention areas, mainly located upstream. The remaining 19 are conveyance projects, or bypass channels, including underground tunnels, which are meant to move more water quickly to Clear Lake and Galveston Bay.

"This is essentially a bypass channel. It’s just a bypass channel that’s underground,” said Brian Gettinger, a project manager with Freese and Nichols. “I can assure you that tunnels are quite doable here.”

According to a map consultants shared, the tunnels would run under League City, the Clear Lake area, Webster and Friendswood. One tunnel would run 8 miles from FM 2351 at Clear Creek to Clear Lake.

Gettinger, who has a background in stormwater tunnels, said tunnels are used in Austin, San Antonio and Dallas to divert water. They are minimally disruptive and allow for less property acquisition than would building bypass channels on the surface, but they are more expensive, he said.

These tunnels, which are built at least 75 feet underground, allow water to drop in at different points, thus providing inline storage while moving water toward an outlet, such as Clear Lake or Galveston Bay, Gettinger said.

Experts are also proposing projects for Dickinson Bayou, though they are not proposing as many, and none of them are tunnels. Consultants shared those details at a meeting last week.

All proposed projects are conceptual. Consultants are working to test the effectiveness of each project by running rainfall simulations through a 2D model they have been developing since February.

In March, experts will return to the public to propose final project suggestions and consider funding methods.