Posted on August 19, 2026
Dane County’s years-long effort to dredge sediment from the Yahara River and reduce flooding risks throughout the region will no longer include an urban portion of the river stretching from Lake Mendota to Lake Monona.
The fifth and final phase of the multimillion dollar project was dropped from the county’s plans at the beginning of this year after a city watershed study concluded that removing sediment from the isthmus area of the river would have little impact in reducing flash flooding during large storms.
Dredging between Mendota and Monona lakes would have been expensive and difficult without heavily disturbing the historic Yahara River Parkway, the study also found.
Originally projected to cost Dane County an estimated $15 million, the effort will now cost less than $10 million, according to John Reimer, assistant director of Dane County’s Land & Water Resources Department, who oversees the project.
New stormwater infrastructure along Madison’s isthmus would be a better fit to addressing local flooding concerns, the watershed study found. During major rain events in recent years, flooding in the area has come from backed up storm sewers rather than the Yahara River.
The county’s ongoing dredging project seeks to improve water flow through river channels to minimize the frequency of flooding. The idea to dredge the river followed a historic rainfall in 2018 that caused major flooding and killed one Madison resident.
That flood caused over $154 million in damage and led to high lake levels. Dane County has seen flooding about every 10 years, Reimer said, but the project hopes to minimize that frequency further.
The dredging project, which now consists of four phases at five locations along the Yahara River, began in 2019. Teams are aiming to finish the first part of phase three by the end of this year, focusing on a channel between Lower Mud Lake and Lake Kegonsa, Reimer said. The second part of phase three will take place over the next two summers.
“We never really had an end date with any of these phases,” Reimer said. “A lot of our work depends on the weather. … We have to wait until after fish spawning time, and then we continue throughout the summer until we hit the fall. We’re talking some time in October, maybe November if we’re lucky.”
Once the water starts freezing, the project ceases until the following spring. The final phase of the project will target a stretch of the river from Highway B to Stoughton and likely won’t start before 2029.
The county’s goal is for water that normally takes two weeks to travel through the channels to take half as long after the project is completed.
The county owns a $650,000 dredging machine, which removes built-up dirt and clay in channels to clear bottlenecks that prevent the river from flowing as well. The county purchased the machine in 2021 after paying a contractor $3.25 million in 2019 to complete the first phase of the project, dredging between lakes Monona and Waubesa.
Reimer estimates the machine has removed about 237,000 cubic yards of sediment to date. The county estimated in 2021 that more than 8.5 million pounds of sediment enter the Yahara chain of lakes every year because of urban runoff.
Sometimes the sediment includes rock. The current stage of the project involves separating those rocks and saving them to take back to the 11 miles between Waubesa and Lower Mud Lake, which borders McFarland, Reimer said. The rocks will eventually make up a blanket on the river floor for fish spawning.
“We always wanted to return rock to the (fish spawning areas),” he said. “We decided to take a bit more effort and time and try to reuse the rock already in the river.”
Ella Hanley is a reporting intern for the Cap Times in 2026. She recently graduated with a bachelor’s degree from the University of Wisconsin-Madison School of Journalism and Mass Communication. Email story ideas and tips to Ella at ehanley@captimes.com.
