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Little Blue River study outlines major regional costs, local impacts and proposed dry basins
Summary
A U.S. Army Corps of Engineers-led study identified reduced channel capacity and rising flood risk in the Little Blue watershed. Tentatively selected plans include dry detention basins and stream restoration; estimated construction costs are large and would require multi-jurisdictional local cost-sharing or congressional action.
George Binger, city engineer, briefed the Public Works Committee on Feb. 10 on the Little Blue River flood risk mitigation and ecosystem restoration study being coordinated with the U.S. Army Corps of Engineers and multiple jurisdictions.
Binger said the Corps' updated modeling shows the channel has lost roughly one-third of its conveyance capacity since the original study in the 1970s, raising water-surface elevations by about two feet in portions of the watershed. "The channel has lost about a third of the capacity over time," he told the committee, and that rise in water surface can bring floodwaters into low-lying buildings in the Oak Ridge Meadows area during a 1% (100-year) event.
The Corps' tentatively selected plan favors a combination of measures, Binger said, including dry detention basins (one of which, called Basin 3, would lie in Lee's Summit), channel realignment or meanders to restore conveyance, and ecosystem actions such as native tree planting along Mouse Creek. He said some large structural options the Corps considered — taller levees and flood walls — performed poorly on federal cost-benefit metrics and were not recommended.
Binger reported the Corps' initial benefit-cost analysis showed a future-without-project damage estimate approaching $47 million per year across the entire watershed. Construction-cost estimates presented in the briefing were substantial: the flood-risk components were in the hundreds of millions, producing a local match obligation on the order of $175 million across participating agencies based on current formulas.
"That's a big number," Binger said. He explained the study's next steps: public presentations of the tentatively selected plan (expected in spring), a Corps dam-safety analysis for proposed basins, finalization of the Chief's Report by 2027 and potential congressional funding consideration in 2028 with construction aimed around 2029 if federal authorization and appropriations are secured.
Binger noted the Corps' ecosystem measures (tree plantings and wetland or prairie options) found native tree plantings most favorable due to cost and resident preferences. He said the dry basins would hold stormwater briefly (about 24 hours) and that Basin 3's footprint overlaps low-lying private property that may require some buyouts.
Committee members asked about assembling multi-jurisdictional cost shares and political support. Binger said local agencies have cooperated on the study but discussions about the significant local match and long-term maintenance costs will be necessary; he suggested exploring federal waivers and regional funding mechanisms.
