River dams won't prevent floods
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JANESVILLE — The Rock River soon will be flowing over land that has been river-free for 100 years or more.
What’s going on, and why can’t we do anything about it?
First the background: Heavy rains across the southern half of the state have saturated the Rock River in Wisconsin, covering hundreds of square miles.
The river is expected to reach a record high level at Janesville on Wednesday.
But all those dams on the river will keep the water in check, right?
Nope.
How about Lake Koshkonong, won’t it absorb the water?
No. Sorry.
Truth is, those dams are not designed to hold vast amounts of water, and Lake Koshkonong already is full, said a Sue Josheff, a DNR civil engineer responsible for the lower Rock River basin.
The rule for anything that holds water, be it a wetland or a huge reservoir, is that once it’s full, it’s full, said Kenneth Potter, civil and environmental engineering professor at UW-Madison.
It’s a bit more complicated than that, Potter said, but in essence, that’s the situation all along the river.
Wetlands can absorb floodwaters, up to a point. So wouldn’t we be better off with more wetlands and fewer dams?
“Wetlands are useful,” Potter said, “but when you get this kind of rainfall, you just better not be in the floodplain.”
Potter said recent rains were unusual in that they were so intense over such a wide area. And they came after much of the land already was saturated.
The water behind dams such as the Centerway Dam in Janesville already is flooding low-lying areas. There’s no other place for it to go, Josheff said.
Wisconsin, with about 3,800 dams, has very few that are designed for flood control, Josheff said.
Most dams were built to create millponds and drive water wheels. Janesville’s Monterey Dam is one of those.
Others were built or converted to produce electricity. The dam in Beloit and the Centerway Dam in Janesville still produce electricity. The Indianford Dam used to.
The Monterey Dam, owned and operated by the city of Janesville, keeps the river high as it flows through the city, so it keeps the river looking better than if it trickled through a muddy channel in the summertime.
But other than that, the dam doesn’t serve any purpose, said Jack Messer, director of public works.
Private businesses or municipalities operate most dams, Josheff said. The DNR regulates some of them, giving operators a range of water level they must maintain. The federal government regulates the hydropower generators.
During floods such as this, the DNR tells operators to open the gates as wide as possible and let the river run as freely as it can, Josheff said.
The DNR has been monitoring river levels and offering advice to operators and emergency government officials as needed as flooding progressed across the state recently, she said.
The silver lining to this rain cloud is that the Rock River is big, and it flows over rather flat land. It reacts slowly.
Smaller streams, such as the Sugar River, will give rise to flash floods with localized thunderstorms.
The Rock has a huge drainage area, or watershed. Recent rains oversaturated most of that watershed, and now, days later, the effect is being felt downstream.
“The nice thing about the Rock, from your viewpoint, is that it’s not flashy,” Potter said.
And that means cities such as Janesville have time to plan.
“I think this is a good test for the city,” Potter said.
Climate experts are saying more intense weather is part of global climate change, although it would be difficult to pin any one event on global warming, Potter said.
However, it’s prudent to plan for more intense weather such as this, Potter said.
City officials should learn from this incident, he said, and ask themselves what they can do to prepare for future events, maybe ones with even higher water.
Jun 16, 2008 at 9:50 a.m.
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Yep, the old catch-all at the end of this article, too ............"global warming"
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"Global warming" is blamed for droughts too, so what was the explanation for the great drought of the 1930's??
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Jun 15, 2008 at 10:25 p.m.
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So the government is responsible for someone who WANTS to build in a floodplain? What ever happened to being responsible for your own mistakes?
Jun 15, 2008 at 10:15 p.m.
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The government declares where floodplains are located.
The government also controls building of homes and businesses through building permits etc.
So the government should be somewhat accountable if they allow a person to build in a known floodplain.
Jun 15, 2008 at 4:58 p.m.
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Just like people building homes right up to an airport & then complaining about the noise.
Jun 15, 2008 at 4:35 p.m.
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I really like how you pointed out the obvious. Really, I mean it. People forget that they are building in the flood plain that is meant to be inundated with water when rivers, lakes, etc. overrun their "boundaries."
Unfortunately, times like this are that stark reminder. Regardless, people will complain that municipalities are not doing enough to protect them. But, like you said, people knowingly built there.
Jun 15, 2008 at 11:52 a.m.
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It's taken a number of Mississippi River communities a while to realize that a floodplain is for floods. You can build in the floodplain, but you had better be prepared to be periodically inundated. The river made the floodplain -- by changing its course back and forth over thousands of years -- and when it floods that's where the water should go. Keeping water out of where it wants to go is difficult and expensive compared to an adaptive and flexible approach of accepting that you're building in land that belongs to the river.
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Janesville generally has good land use in the floodplains with some exceptions. The city really has to decide if maintaining those exceptions in the long run is worth the expense in emergency situations like this.
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