Following Hurricane Harvey, contractors staged equipment for the Army Corps of Engineers’ dredging of the West Fork of the San Jacinto River east of Highway 59, Wednesday, Aug. 1, 2018 in Humble.
Mark Mulligan/Staff photographer
Following Hurricane Harvey, crews began an emergency dredging operation in the San Jacinto River West Fork on Thursday, Sept. 20, 2018.
Courtesy of the US Army Corps of Engineers
Col. Rhett Blackmon, commanding officer and chief engineer for US Army Corps of Engineers Galveston District, answers questions during a press conference on Thursday, June 22, 2023 at Judson Robinson Sr. Community Center in Houston.
Yi-Chin Lee/Staff photographer
Some Kingwood-area residents are concerned that sediment roiling into the flood-ravaged San Jacinto River will create blockages like those that sent floodwater into nearby homes during Hurricane Harvey.
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“It’s percolating right now, let me tell you, it’s moving along,” said Bob Rehak, a Kingwood retiree who follows the area’s flooding and sits on Harris County’s Community Flood Resilience Task Force. He said he was concerned this week’s fast-moving water will push sediment into new sand banks near his community, even after the Army Corps of Engineers’ dredged out much of the former accumulation after Harvey.
Rehak said storms always reshaped the riverbed. During Harvey, he said, so much sand was added to existing bottlenecks that two large sandbars blocked 90% of the river’s flow along its west fork, pushing backed up water into the neighborhood. After this weekend, I expect to find new sandy choke points in the river.
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“The peak hasn’t even hit us yet here in Kingwood,” he said.
Rehak has pointed to the thousands of open sand mines farther up the river as the source of its problematic volumes of sediment, picked up by fast-moving currents during floods. In the past, the Texas Aggregates and Concrete Association has refuted these claims, saying that the operations’ sand removal is reducing the total sediment that could be pulled into the waterway.
Jason Krahn, the chief infrastructure and operations officer for the Harris County Flood Control District, said all rivers and streams move a certain amount of sediment and woody debris regardless of human intervention, sometimes catching at key locations along the route.
“It’s just going to be something that has to be managed in time,” said Krahn, noting a “balance between flood risk mitigation for the folks who live around that area and the natural processes.”
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Krahn said that large sandbanks like those dredged out by the Army Corps after Harvey are likely to form over time, rather than all at once.
That leg of the river system contains two managed bodies of water with dams to control their flow: Lake Conroe, managed by the San Jacinto River Authority, and Lake Houston, owned by the city. But none of those authorities nor the county flood control district say they are in charge of managing new sedimentation in river stretches.
Tim Garfield, a retired geologist whose Kingwood home was one of an estimated 16,000 in the area that flooded during Harvey, said he spent months after trying to ensure the sandbank at the river mouth in his area was part of the Army Corps’ dredging plans.
Corps contractors did dredge it, after some debate with local officials, but Garfield said he worried that the work was insufficient and “just gave it a haircut.”
Another major flood “will back sediment right into the part that they did dredge in no time,” he said.
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After Harvey, Army Corps officials said they were authorized only to restore the river to its pre-storm condition. Although the federal agency dredges 30 to 40 million cubic yards of material annually in the Galveston area to keep big ships and their cargo moving, the San Jacinto River is not a federal navigable waterway.
“The sedimentation from recurring annual flows in the San Jacinto River are not within the USACE Galveston District’s FEMA Mission Assignment or current assignments,” said the Corps’ Galveston-area spokesperson Neil Murphy. Their work after Harvey with contractors Great Lakes Dredge and Callan Marine, which they said removed more than 2.5 million cubic yards of accumulated sediment, was a specific federal response to the disaster.
If flooding worsens as anticipated over the weekend, Kingwood residents must wait until the water recedes to see where new sand settles, how it will change the river’s flow, and who will be responsible for cleaning it up.
