City of Madison, Wisconsin | Legislative Information Center
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File #: 53504    Version: 1 Name: Requesting Dane County and the City of Madison convene a technical work group to study strategies for reducing the risk of future high lake level events and flooding on the Yahara River and the Yahara Lakes.
Type: Resolution Status: Passed
File created: 10/11/2018 In control: Engineering Division
On agenda: 10/16/2018 Final action: 10/30/2018
Enactment date: 11/5/2018 Enactment #: RES-18-00766
Title: Requesting Dane County and the City of Madison convene a technical work group to study strategies for reducing the risk of future high lake level events and flooding on the Yahara River and the Yahara Lakes.
Sponsors: Paul R. Soglin, Marsha A. Rummel, Arvina Martin, Michael J. Tierney, Michael E. Verveer, Larry Palm, Barbara Harrington-McKinney, David Ahrens, Keith Furman, Ledell Zellers
Fiscal Note
No Fiscal Impact
Title
Requesting Dane County and the City of Madison convene a technical work group to study strategies for reducing the risk of future high lake level events and flooding on the Yahara River and the Yahara Lakes.
Body
Lakes Mendota and Monona are at water levels well above the WDNR ordered summer maximums much of the summer in a typical year. This year is no exception. In the months leading up to the August 20, 2018 storm that devastated parts of western Dane County, the Madison lakes were already well above their summer maximum elevation. The August 20 storm caused the lakes to rise to critical elevations. Lake Monona rose to 10 inches above the 100 year flood elevation and high water on the Yahara River caused road closures within the lower lying areas of the isthmus, including one of the three arterials traversing the east isthmus. In addition, there were lane closures on East Washington Ave (US 151) due to flooding.


With the Tenney Dam, located where water exits Lake Mendota into the Yahara River, water elevations on Lake Mendota can be well controlled. Unfortunately, there is little that can be done to control water levels on Lake Monona in a flooding situation, because the capacity of the Yahara River downstream of Lake Monona is limited. This sets up a situation where water must be released out of Lake Mendota to preserve the integrity of the dam but the water coming into Lake Monona can’t leave at a rate high enough to prevent a significant rise in water level on Lake Monona.

The Yahara River through the east isthmus between Lake Mendota and Lake Monona has good capacity but the capacity of the river does become problematic when the discharge rate is extremely high. High release rates from Lake Mendota combined with high water levels on Lake Monona create a significantly higher profile on the river and this increases the potential for flooding, especially flash flooding when storm sewers, filled with water...

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