Dane County Starts New Phase of Climate Change Mitigation Project to Reduce Yahara Lakes Flooding Risk

June 17, 2021
Ariana Vruwink, 608-267-8823
County Executive, Land & Water Resources

Dane County’s “Dragon Dredge” Now in the Water, Continuing 11-Mile Sediment Removal Initiative to Improve Management of Lake Levels During High Water Periods

Today, County Executive Joe Parisi joined Land and Water Resource Department staff in McFarland to announce that Dane County has officially begun the second phase of its Yahara Chain of Lakes Sediment Removal Project. This phase of the project kicked off this week, with dredging equipment now in the water, working between Lake Waubesa and Lower Mud Lake. The County hopes to remove approximately 52,000 cubic yards (or more than 4,000 dump truck loads) of sediment in the project’s second phase to help improve water flow, flood storage capacity, and fish and wildlife habitat in the Yahara Lakes.

“We are excited to kick off this next phase of our flood mitigation project in the Yahara Chain of Lakes,” said County Executive Parisi. “As climate change continues to impact our area, Dane County is committed to mitigating future flooding risks. When complete, this 11-mile sediment removal initiative will help increase the flow of water through the Yahara Chain of Lakes and improve the management of lake levels during high water periods.”

While Dane County has been fortunate to avoid sustained high water events on area lakes more recently, staff are moving forward expeditiously to keep the project going, given the unpredictability of climate change rains. The second phase of the initiative will focus on two stretches of the Yahara River: Lake Waubesa to Lower Mud Lake and Lake Kegonsa to Highway B.

Between Lake Waubesa and Lower Mud Lake, Dane County is using its newly acquired “Dragon Dredge,” first unveiled in March 2021, to help move water through the Yahara Chain of Lakes at a steadier clip and help mitigate the risk of flooding. Parisi included $5 million in his 2020 budget to purchase this new equipment and create four staff positions to carry out the job. By owning and operating its own equipment, Dane County can ensure for years to come that it has the tools and expertise in-house to manage work demands created by the new realities of climate change and rapid urban development.

Currently, water comes into the Yahara Chain of Lakes faster than it goes out—taking two inches of rain over two weeks to leave the Yahara Lakes system. The efficient movement of water downstream can be undermined by sediment loading. While sediment movement is a naturally occurring process, accumulation of sediment in the Yahara River and Lakes is greatly increased by human activity, including urban development. It is estimated that over 8.5 million pounds of sediment enter the Yahara River and Lakes each year from urban runoff.

Staff predict about half of the work will be completed between Lake Waubesa and Lower Mud Lake by the end of 2021, with the other half expected to reach completion in 2022. Work between Lake Kegonsa and Highway B, the other section of river covered in phase two, is currently under process for bidding. Dane County hopes to have mobilization start this fall, with dredging kicking off in 2022.

The sediment removal project in the Yahara Lakes system will take place in five phases, with each phase carried out as Dane County secures permitting. In May 2020, Dane County kicked off the first phase of the project between Lakes Monona and Waubesa. The County removed approximately 40,000 cubic yards—or more than 3,000 dump truck loads—of sediment before the $3.25 million effort concluded last fall.

Parisi included an additional $2.5 million in his 2021 budget to keep the initiative on track this year.