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Madison reviews decades of flood studies; Army Corps feasibility and FEMA grants discussed
Summary
Staff reviewed prior hydrology studies and Army Corps work, said a Park Creek tributary detention pond showed the highest net benefits in a Section 22/Section 205 analysis, and warned that recent FEMA map changes reduce the eligible floodplain and could lower benefit‑cost ratios required for federal funding.
Ryan, a city staff member, gave the commission an extended briefing summarizing flood events, prior studies and possible next steps to reduce flood risk in Madison and Lake County.
Ryan said Madison has experienced repeated major flood events (noting the 1993, 2012 and 2019 storms) and walked commissioners through prior technical work: a Banner Associates drainage and erosion study, a 2013 Local Emergency Planning Committee (LEPC) report, a 2014–2016 section 22 Army Corps of Engineers study, a 2017 Silver Jackets flood‑risk assessment, and the more recent Army Corps section 22 update that evaluated structural and nonstructural alternatives.
On the studies, Ryan told the commission that the Army Corps analysis found several alternatives with positive benefit‑cost ratios and that “the Park Creek tributary detention pond … has the alternate with the highest net benefits.” He described estimated costs the city would face and funding rules for a Corps Section 205 feasibility study: the federal government funds planning up to $100,000 and shares costs above that 50/50 for the appraisal phase, while construction cost‑share is typically 65% federal and 35% nonfederal. Ryan said the Army Corps indicated a maximum federal contribution of $10,000,000 for planning, design and construction combined; any costs above that limit would be local responsibility.
Ryan provided several cost examples from the materials presented: a Park Creek dam north of town was estimated at roughly $9,500,000 for construction; a combined two‑dam scenario was estimated near $12,400,000 (with an estimated local share of about $4,300,000 at 35%). He also described a section 205 dam‑safety feasibility assessment the Corps estimated in 2023 at roughly $700,000–$750,000, which would place a local share in the low‑to‑mid $300,000 range after the initial federal contribution.
Ryan warned that FEMA’s new Flood Insurance Rate Maps (FIRMs) had substantially reduced the special flood hazard area in Madison—from roughly 360 acres to 241 acres—and reduced the count of structures in the mapped special flood hazard area from about 381 to 230. He said those reductions would likely lower benefit‑cost ratios used to qualify Corps projects; he cited past benefit‑cost results from the Silver Jackets and section 22 work (examples: Park Creek detention pond BCR 1.31; Park Creek tributary BCR 3.91; combination BCR 1.48) and said a reduced floodplain and fewer structures could materially affect feasibility.
Ryan described non‑Corps funding options as well, including FEMA’s Flood Mitigation Assistance (FMA) and Hazard Mitigation Grant Program (HMGP). He said Madison has 19 repetitively damaged properties and about 100 structures remaining in the floodway—figures that make the community eligible to consider buyouts or mitigation projects under those grant programs. Ryan noted the FMA program is competitive and HMGP typically funds buyouts at approximately 75% federal / 25% local share.
Commissioners and residents asked questions about local options such as using Frisbie Park for detention or phased smaller projects, timelines, and budgeting. Ryan said the next formal step to pursue a Corps feasibility study would be for the city to send a written request to the Army Corps to initiate the Corps' initial appraisal; he suggested budgeting the city’s cost share in the 2026 budget and returning to the commission with a formal motion to send such a letter.
There were no final votes on flood projects at the meeting; commissioners expressed support for moving the process forward and asked staff to prepare next steps and budget estimates.
