Weed Cutter

Dane County's Land and Water Resources Department is using aquatic weed cutters to help unclog the Yahara River, which helps water move more quickly through the system to lower lake levels and prevent flooding.

Flooding concerns are low along the Yahara River lakes, Dane County and Madison officials said, but that doesn’t mean there is no risk.

While Lakes Mendota, Monona, Waubesa and Kegonsa are slightly above the summer maximum water level — as designated by the state Department of Natural Resources — the lakes are at a lower level than they were at this time last year, said Laura Hicklin, county Land and Water Resources Department director.

A deluge of rain last August and September led to widespread flash flooding and prolonged flooding on Madison’s Isthmus and along Lake Monona. Officials have said similar flooding can happen again if another massive storm comes through the region.

To try to keep the lake levels manageable, aquatic weed harvesters have also been sent out into the Yahara River downstream and between the lakes to remove plants that clog up the river and slow the flow of water.

Report on historic Dane County flooding offers prevention, management options

The county also plans to dredge out parts of the riverbed to increase the flow of water out of the system, letting the county drain the lakes more quickly if they fill with more water. The first dredging operation will be in the Yahara River between Lakes Monona and Waubesa, where the county hopes to remove sediment build-up of two to three feet along about 1.75 miles of the river.

The city of Madison — which was hit both by flash flooding in a torrential downpour last August and steeped in floodwater for weeks as the lake water overwhelmed storm sewers on the Isthmus — has been studying the effects of the heavy rainstorm and other rain events on eight different watersheds across the city, Engineering Division spokeswoman Hannah Mohelnitzky said.

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Future flood prevention and storm water management has been a priority of the Engineering Division since last summer, Mohelnitzky said.

Because the current lake levels are not drastically high, the city is not concerned at this time that the Isthmus or other low-lying areas will experience flooding, but the chance of flash flooding is as unpredictable as the weather.

“Flash flooding can happen at any time, so we keep an eye on every storm,” Mohelnitzky said.

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The division hasn’t decided on any new practices for flood prevention yet, she said, because it is still gathering data on the watersheds and what areas of the city face the greatest threats from heavy rainstorms. As part of the watershed studies, the city is holding public hearings and convening focus groups.

“We’re trying to listen and hear where the problems are,” Mohelnitzky said.

The city sends out weekly updates related to its efforts on flooding. Area residents can sign up to receive the updates at go.madison.com/flood-updates.

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