Kossuth County supervisors ask staff for culvert cost estimates after resident reports recurring flood damage

A Kossuth County resident told the Board of Supervisors on Tuesday that a gravel road near Highway 169 has flooded repeatedly over decades and that lowering the road or adding larger culverts could reduce water damage to nearby property.

The resident said the road has been overtopped in 18 of the last 45 years and that “if you took it down 3 feet, you’d alleviate the problem.” County staff and supervisors spent more than an hour discussing hydraulic constraints, culvert capacity and possible options.

County Engineer Doug (staff member) warned that lowering the road would increase the frequency of inundation because the road sits in the floodplain and that during large floods the entire floodplain carries flow. He said a 1% (100‑year) event in the watershed can generate on the order of 14,500 cubic feet per second and a 0.5% (500‑year) event about 16,500 cubic feet per second. “As that flow increases and needs to use more of the flood plain naturally, it uses it,” Doug said.

Supervisors and residents discussed alternatives including lowering the road, adding multiple culverts, placing a larger single culvert (a 6‑foot diameter was mentioned) and routine repairs. The county engineer noted limitations: culvert capacity depends on outlet elevation and hydraulics, culverts can “silk in” (silt up) and multiple parallel culverts can be prone to plugging during high flows.

Supervisor Kyle asked for cost estimates for additional culverts and asked staff to return with pricing for 42‑inch and 48‑inch culverts and an option for a larger diameter, noting a desire to evaluate lower‑cost options first. Doug said he could obtain estimates and expected to have information ready within roughly two weeks.

No formal vote was taken; the board’s direction to staff was to gather cost and feasibility information and place the item on a future agenda. The county engineer also noted the potential for many similar requests countywide if the board chooses to add culverts to reduce local flooding frequency.

The discussion included practical details residents raised about gravel delivery, previous repairs using crushed asphalt and concerns about traffic and property access when roads are closed, and the engineer’s note that some county roads must be closed during certain flood events.

Supervisors did not authorize construction or commit county funds during the meeting; they instructed staff to return with cost estimates and feasibility analysis for additional culverts and to place the matter on a future agenda so supervisors and residents can review the options.

A follow‑up agenda item to review the culvert prices and options was discussed for two weeks out.