Sunday, October 21, 2018
Pictured is the Korn Dam, which was one of three flood control dams in the Town of Portland that failed during the September 28 rain storms that dropped over 12 inches of rain on the area in less than eight hours. The aerial view shows the breach on the left. The emergency spillway on the right began to erode before the dam failed. The actual berm remained intact.

Failed dams leave area vulnerable

Portland residents back rebuilding flood control structures that failed in September storms

Residents of the Town of Portland are well aware of what Mother Nature's fury can wreak.

On September 28, a line of thunderstorms hammered the township, located on the southwest border of Monroe County, with over a foot of rain in a six to eight hour period.

That unprecedented deluge resulted in millions of dollars of damage, not only within the township itself, but to public infrastructure and private property downstream from the coulees that are a feature of Portland's terrain.

Hidden within those coulees are seven flood control structures of varying size, designed and built in the early 1960s, to slow the flow of rainwater runoff in the Coon Creek Watershed and alleviate flooding in the valleys.

Unfortunately, the PL566 dams, as they are called, weren't designed to withstand September's heavy rainfall and three of them failed, releasing huge volumes of water downstream, washing out roads, bridges and driveways and inundating communities.

"Unfortunately, we had a disaster that nobody saw coming," said Bob Micheel, Monroe County land conservationist.

He was speaking to a crowd of around three dozen property owners and town officials, who gathered at the Portland Town Hall Wednesday.

Micheel, along with Monroe County zoning administrator Alison Elliott and emergency management director Darlene Pintarro, were there to for an informational meeting and to gauge local support for reestablishing flood control measures lost when the dams were breached.

Micheel told the group the dams were built with 1960s technology and weren't designed to handle big rain events that are becoming more and more common.

The dams are designed to temporarily hold rainwater runoff from large drainage areas up to thousands of acres and slowly release it through a pipe built into the berm. There is an emergency spillway on one side of the dams but its the other end where the problems occurred.

While the actual berms remained intact, it was where the dam abuts the side of the hills that the breaches occurred (see photo). The hills crumbled away under the rushing water.

"Nobody thought about those dams overtopping," said Micheel.

Between La Crosse, Vernon and Monroe counties, there are around 32 flood control structures and a dozen of them overtopped during the September flooding.

"That's the first time that's ever happened," said Micheel, adding that the first time emergency spillways ever ran in the structures was in last year's July flood when three of them became that full.

"We're ramping up in water and intensity."

"Whether you believe it or not, our climate is changing," he added, pointing out  that since 2007, there have been 16 significant flood events in the drifltless region and that some of the warmest years on record have occurred since 2000.

With those increased temperatures comes increased evaporation, more moisture in the atmosphere and more intense rainfall.

"We can take rain scattered over a 24-hour period, but we can't take rains of six to seven inches in an hour and half. There's nothing we've designed that can handle that."

The seven Portland dams control a vast amount of upland acreage, but also have a huge impact on downstream property owners. Joe Schaitel, who owns a farm in the Town of Leon, is one of them.

"Those dams are extremely important to us down there on that land," he said.

Dan Korn, chairman of the Town of Washington in La Crosse County, pointed out that the runoff in the Town of Portland eventually ends up in La Crosse County.

"I strongly encourage some type of reconstruction of those dams because as they fail, all the residents downstream pay the price," he said.

Micheel said flood controls in the watershed need more robust and resilient designs and he is expecting federal engineers and surveyors to come up with those plans in the coming months. He insisted any solutions will have to include other land conservation methods.

However, those solutions are going to be costly. How costly has yet to be determined, but there are funds available through the Natural Resources Conservation Service, Federal Emergency Management Administration, the DNR and the county, as well as non-governmental organizations.

Micheel pointed out that abandoning the damaged dams would require land-use planning, including moving crops and structures out of flood plains, which also wouldn't be cheap.  

Those who attended the meeting endorsed Micheel's efforts and told him to move forward. Micheel said he would schedule another meeting in six months, but in the meantime wanted more feedback from residents.

"We want to make sure everyone is confident in the direction we're going," he said, adding the wise thing to do is to look at the Coon Creek Watershed as a whole.

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