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Garnett, Kansas, using ‘concrete carpet’ to help prevent erosion, control flooding

City installed Flexamat around reservoir which supplies city’s drinking water
travis wilson.png
Posted at 4:05 PM, May 29, 2024

GARNETT, Kan. — Kansas is famous for the yellow brick road, but one city us using a “concrete carpet” to help prevent erosion.

Late last year, Garnett, Kansas, installed a product called Flexamat in an erosion prone area near the north end of Cedar Valley Reservoir.

Garnett draws on the reservoir to supply the city with drinking water.

Floods in 2018 and 2019 eroded an auxiliary spillway on the south side of the dam, which holds the reservoir in place.

Garnett City Manager Travis Wilson said if the erosion continued, it could have impacted the integrity of the dam, and in turn could impact the city’s water supply.

"If you have the dam blowout, we lose our drinking water, which is a bigger issue," Wilson said. "So overall, the integrity of the dam and integrity of the auxiliary side as well, it’s all pivotal in this area.”

Flexamat is a mat containing thousands of concrete blocks which act as bedrock and prevent water from further eroding areas like the auxiliary spillway.

Grass grows through the mat helping anchor the blocks in place.

The erosion solution got its first test this spring.

In April, Garnett received close to double its monthly average rainfall. Wilson said the “concrete carpet” did its job.

“It’s a huge relief,” Wilson said. “It’s been six years in the making since this project started. To see some, hopefully, finality out of it is a very huge lift off my shoulders for sure.”

Paying for the project was a hurdle.

The project came with a roughly $4.3 million price tag, but Garnett only collects a little more than $1.1 million annually in city taxes.

Because FEMA declared disasters after flooding in 2018 and 2019, the federal agency helped cover the expenses.

Wilson said FEMA paid for 75 percent of the project while the state of Kansas chipped in for 10 percent of the total, leaving Garnett to cover about 15 percent or $650,000.

“It would’ve took us three or four years or more just to come up with that [$4.3 million total]," Wilson said. "Taxes would’ve been raised; it would’ve been a huge detriment to the city, to the residents if we would’ve had to go that route."

Even on a Wednesday afternoon, fishermen were on the reservoir.

Frank Cashio said he caught several bream and crappie. He’s thankful the city and other government agencies invested tax dollars in the reservoir.

“You have to protect your resources, because once it’s gone, it’s gone,” Cashio said.