On March 30, officials from consulting firm Freese and Nichols showed the public ways to mitigate local flooding in the Dickinson Bayou Watershed. The firm also studied and came up with flooding solutions for the Clear Creek Watershed, which the firm will present March 31.
League City hired Freese and Nichols to come up with regional flooding solutions. Other municipalities, including Pearland, Friendswood and others, added money into the study.
The options Freese and Nichols presented included building multiple detention basins and a 500-foot-wide diversion channel that would take flood water from Dickinson Bayou to Galveston Bay.
The first option included building five detention basins in the watershed. The estimated cost is $220 million.
A couple of the bigger detention basins, such as one proposed near MacFarland Road, would be built in mostly rural areas. While they would help flooding overall, the biggest impact would be in their immediate vicinity, and because the rural areas do not have many structures nearby, the flood mitigation would not necessarily be obvious, Freese and Nichols Project Manager Brian Gettinger said.
Another option Freese and Nichols presented included building a massive diversion channel in addition to the five detention areas for an estimated $500 million. Over 50 years, such a solution would prevent an estimated 15,000 structures from flooding and prevent $245 million in flooding damages, which is three times the benefit compared to building the detention ponds alone, Gettinger said.
“A dramatic increase in benefits,” he said. “A huge number of structures are removed from the flooding risk.”
The channel would be over 50% bigger than the length of a football field and miles long. It would require buyouts of properties to build, Gettinger said.
Such an idea has been on the books since at least 1994, and Freese and Nichols said they hope they can be the ones to actually see a diversion channel come to fruition, Gettinger said.
Despite these dramatic propositions, thousands of structures would remain at risk of flooding. With the detention ponds and channel in place, an estimated 1,800 structures would flood during a 10-year storm in what Gettinger called “the bowl,” an area east of I-45 that is prone to severe flooding, Gettinger said.
“The bowl is improved [with these projects], but it remains a problem area,” he said.
One project Freese and Nichols considered was building a flood wall along FM 517 and building large pump stations along Dickinson Bay. The $200 million-$250 million project would prevent flooding during 10-year storms only; anything more severe and water would breach the flood wall and enter structures, Gettinger said.
To fund hundreds of millions of dollars’ worth of projects, League City will need state or federal partners, such as the Texas General Land Office, the U.S. Army Corps of Engineers, the Federal Emergency Management Agency, the U.S. Department of Agriculture, the Department of Housing and Urban Development, or the Texas Water Development Board. However, partnerships come with their own complications, such as determining cost-benefit ratios, Gettinger said.
Another funding idea is to create a Dickinson Bayou Flood Control District that includes League City, Dickinson, Texas City, Alvin and other municipalities. This body could potentially tax its residents to fund flood-control projects, similar to the proposed Gulf Coast Protection District state legislators are considering to fund a coastal barrier.
Next, Freese and Nichols will consider public feedback on the proposed projects and come up with official recommendations, Freese and Nichols associate Chuck Wolf said.