Dane County Showcases Latest Phase of Project to Reduce Yahara Lakes Flooding Risk from Climate Change Rains

July 06, 2022
Ariana Vruwink, 608-267-8823
County Executive, Land & Water Resources

Dane County Continues Multi-Year, 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 at Babcock County Park to showcase the second phase of its Yahara Chain of Lakes Sediment Removal Project. The County hopes to remove approximately 152,000 cubic yards (or about 12,000 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.

“The rain and storms we are experiencing this week are an ongoing reminder of why this climate change project is so important to help mitigate future flooding risks,” said Dane County Executive Joe Parisi. “This 11-mile sediment removal initiative will help us increase the flow of water through the Yahara Chain of Lakes and improve the management of lake levels during high water periods. We are excited to keep this project moving forward.”

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. A recent 2021 report by UW-Madison climate scientists concludes that Wisconsin continues to get warmer, wetter, and will experience extreme weather events more frequently:

• The last two decades have been the warmest on record, and the past decade has been the wettest.
• Wisconsin has become wetter – average precipitation has increased 17 percent (about five inches) since 1950.
• Southern Wisconsin has experienced the highest increase in precipitation, and very extreme precipitation events will increase in the future.
• Extreme events are already causing immense impacts across the state, and the frequency of those events will generally increase.

The second phase of this multi-year initiative focuses on two stretches of the Yahara River: Lake Waubesa to Lower Mud Lake and Lake Kegonsa to Highway B. The work between Lake Waubesa and Lower Mud Lake started in summer of 2021 and will near completion in fall of 2022. Approximately 52,000 cubic yards of sediment will be removed from that section of the Yahara River. The work between Lake Kegonsa and Highway B started in summer of 2022. Currently, a dewatering basin is being built to store sediment that will be pumped by a hydraulic dredge. The hydraulic dredging is anticipated to start in spring of 2023. Approximately 100,000 cubic yards of sediment will be removed from that section of the Yahara River.

Between Lake Waubesa and Lower Mud Lake, Dane County is using its “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.

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 in fall 2020.

Parisi included $2.5 million in his 2021 budget and $3 million in his 2022 budget to keep the initiative moving forward.