Minnesota isn’t usually considered a problem area for landslides and mudslides. But in the past several years, the state has seen several devastating examples of each:
• Two children killed in a 2013 landslide during a field trip at Lilydale Regional Park in St. Paul.
• The collapse of a slope on West River Parkway in Minneapolis in 2014 that cost millions of dollars to repair.
• Houses destroyed along Purgatory Creek in Eden Prairie and along the Minnesota River in Henderson, Minn.
So Eric Waage, Hennepin County’s emergency management director, was recently invited with other experts to brief Congress on landslide threats and the science behind them.
He discussed a relatively rare local-scale landslide assessment that Hennepin County is doing and why it’s important to local emergency officials.
“When I attend a conference like this, I’m asked if I’m lost,” he said. “This issue is usually associated with mountainous states.
“But I was there to indicate it’s just not a mountain range problem.”
Waage, a retired officer with the Minnesota National Guard, was the only speaker at the meeting with first responder experience. The other three speakers were Jonathan Godt with the U.S. Geological Survey, Penny Luehring with the U.S. Forest Service and Jennifer Bauer with Appalachian Landslide Consultants.
Rep. Doug Lamborn, R-Colo., held the briefing. It included observations from the hurricanes in Puerto Rico and how science can help decisionmakers reduce losses and respond to threats.
Waage said preliminary data show that landslide activity is rising in Minnesota.
“It makes sense if you peg it to an increase in frequency and intensity of precipitation,” he said.
‘A rational explanation’
Waage, who long has had an interest in geology, gained experience working on floods, lost children, forest fires and other incidents requiring first responder assistance.
When he became Hennepin County’s emergency management director, the threat of landslides wasn’t a major concern, he said.
Then the spring of 2013 brought a lot of rain, loosening the earth.
Fourth-graders Mohamed Fofana and Haysem Sani were killed on a school field trip when a waterlogged cliff in a St. Paul park collapsed under them as they searched for fossils.
A year later, a riverfront slope near the University of Minnesota Medical Center in Minneapolis washed out. It took two years to rebuild, longer than the new Interstate 35W bridge after the old one collapsed.
“People struggled to explain how this could happen, saying it was an act of God,” said Waage. “But there was a rational explanation.”
Hennepin County has commissioned an atlas to identify and assess all types of hazards and threats. The information can be used for planning emergency responses and to recognize physical conditions that precede landslides, allowing the county to issue alerts during times of higher risk.
The atlas will contain maps of known landslide locations and their dates, a few dozen of which are known in Hennepin County right now, Waage said.
It also will include locations of more than 1,000 slides of unknown dates that were found using LIDAR (light detection and ranging) analysis.
The landslide assessment was a cooperative effort of Hennepin County’s Emergency Management Department and Regional Railroad Authority, the U, the DNR, the State Climatology Office, the U.S. Geological Survey, the National Weather Service and the Freshwater Foundation.
The county assessment format served as the basis for an appeal to the Legislature to fund similar assessments in four parts of the state by different universities.
“It’s important to note that no detailed local landslide information was available to us before this effort,” said Waage. “Current landslide hazard maps are very generalized at a national level of detail. Existing data on slides had mostly been split up among highway departments, railroads and emergency managers.”