Preliminary results of a nearly two-year study being conducted by the U.S. Army Corps of Engineers indicate the City of Hays could take steps to help mitigate the threat of severe flooding in Lincoln Draw.
The draw runs from north to south and covers approximately 4.25 square miles, flowing through the center of the city.
“Our purpose here is to not only evaluate, but also try to provide a recommendation on how to fix the problem and to determine whether there’s a federal interest in participating in a 65/35-percent cost share on a construction project,” said Cassidy Garden, a civil engineer with the U.S. Army Corps of Engineers division in Kansas City. “... The problem is, as we all know it, there is a high risk of loss of life and damages to properties due to frequent flash flooding in the Lincoln Draw watershed.”
The civil engineers hosted a public information meeting Tuesday evening at city hall to share preliminary results of the ongoing study, which was commissioned in 2015.
The downtown area is at greatest risk for severe damage from flooding, and the study is looking particularly at the possibility of a 100-year flood event.
Several possible structural and non-structural solutions were considered, but the most probable solutions include increasing water capacity underneath the U.S. Highway 183 Bypass. The preliminary study results also propose the possible creation of up to six more dry dam holding basins and modifications to two existing dams.
The study is not yet complete, and additional data will be collected and analyzed to determine how many additional dams would be needed and where they should be located, Garden said. If the project moves forward, it would be the city’s responsibility to obtain necessary land easements and right-of-way changes, which would count toward the city’s 35-percent cost share if a project is approved.
The cost of increasing capacity under the 183 Bypass and adding upstream detention dams is estimated at a total of more than $13 million. Other possible solutions — such as a floodwalls and replacing a downtown stormwater tunnel with an open channel — were determined impossible due to high costs.
A final report from the U.S. Army Corps of Engineers is expected in spring 2019, at which time the Corps and the City of Hays would determine if they want to move a project forward.
Approximately 30 residents, city commissioners and staff members attended Tuesday’s meeting. Several residents who live in areas affected by stormwater flooding issues expressed their concerns and asked questions.
Some questioned how the construction of additional dry dams upstream would effectively solve the more severe flooding problems in the older part of town near the downtown and university districts.
City of Hays project manager John Braun said the solutions currently being considered would not be a fix-all, but could significantly reduce the risk of a catastrophic flood in the event of a rare and severe rainstorm.
“This isn’t even intended to solve all of the flooding problems. … I mean the 100-year storm hasn’t happened in recent history, so I think what these are intended to do is to help with that storm that we haven’t even seen yet,” Braun said.
A project must demonstrate an economic benefit that is expected to outweigh cost to be eligible for federal match funding through the Army Corps of Engineers. While the projects being discussed might not be a perfect solution, it so far appears the work would help mitigate the city’s current flood risks, said John Grothaus, a project manager for the Corps’ Kansas City district.
“Our findings so far show we can reduce the flood risk and flood damage to a fairly significant number of structures,” he said. “And if we didn’t show that, we wouldn’t still be here. Can we completely eliminate flooding? No, no project can eliminate the risk of flooding.”
The study is funded with a 50/50 cost share, with the city paying approximately $330,000.