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Flooding News Update For Madison Isthmus

August 25, 2018

Sunny skies but very humid conditions have greeted people in Madison all day.  On the isthmus there is a very strong drive for more sandbagging as operations continue to fill bags and place them in vital places for the waters which are forecast to rise as more rains are expected to fall.

As of this morning the news came that Lake Monona was down 1 inch and Lake Monona was up 1 inch. The level of the Yahara River at East Main Street was up 1.8 inches. The Tenney Dam is discharging at 730 cubic feet per second and Dane County is planning to slow the discharge rate starting this evening.  As a result, by Sunday morning the drop in Lake Mendota is expected to slow and Lake Monona is expected to stabilize.  The elevation of the Yahara River is expected to drop by about an inch.

While that is the good news there is some bad news on the horizon.  The next significant chance of rain will occur starting around 4:00 PM Sunday.  Low lying areas of the isthmus are now at the same elevation as the elevation of the Yahara River or Lake Monona.   That is simply awful news.

What that means is the water now in the streets are essentially a back water of the Yahara River or Lake Monona. Storm inlets and pipes are the only way to drain the street. When it rains, instead of water draining into a dry pipe, the water entering the pipe has to push water out.  This makes the storm sewer much less efficient.  Urban flash flooding is a concern during heavy rainfall and, depending upon the severity, property and vehicles could be flood.

This is an hour by hour chess game with Mother Nature.  While holding steady now the odds do not look good for some living in the lower lying areas of the isthmus.

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