Shoreline damage due to ice and frost heaves has reached epic proportions on area lakes this year, toppling walls and trees and forcing up ridges as high as 10 feet in some places.
The lack of snow and dramatic swings in temperature this winter created the perfect conditions to encourage lake ice movement. As ice thaws and rapidly refreezes, stress fractures develop, and ridges form when ice sheets collide. The ice applies pressure to the shoreline, causing it to buckle and heave. Without snow to insulate the ice, these effects are amplified, said Chris Pence, Crow Wing County land services supervisor.
"Every lake has it," Pence said. "I don't think there's a lake that's going to get away with not having it."
"Every lake has it," Chris Pence, Crow Wing County land services supervisor said. "I don't think there's a lake that's going to get away with not having it."
He said he's received reports of damage all over the county. Boathouses on Pelican Lake in Breezy Point and Crow Wing Lake in Fort Ripley have been damage or tipped over. On White Sand Lake in Baxter, shoreline damage is evident in cracked and falling beach walls and heaves in people's yards.
Dan Neff, a resident on White Sand Lake for more than 40 years, said he's never seen damage so dramatic.
"Our yard is about four feet high close to the lake," Neff said. "It's weird. ... Everybody's got a mess."
Neff said the public access on White Sand is damaged and the ramps are shoved up into the air.
"I don't know how guys got their fish houses off the lake," he said.
Earlier this winter, the Schwen family on Gull Lake experienced extensive sidewalk damage after what they described as a boom that shook their homes, likely caused by sudden ice sheet movement.
Pence said dealing with shoreline disturbances are a normal part of lake living, although it's usually not as widespread. He said some people believe it's due to high water levels, but he does not think this plays much of a role. It often appears to come out of nowhere with little visual evidence of what created the ridges.
"You go out there and you expect to see this huge chunk of ice just pushing on this, but you don't," Pence said. "You see the dirt pushed up and you don't see any ice that pushed it. You don't get to see the smoking gun, per se."
This is one of the reasons the county has setback requirements, he said, because buildings too close to the shoreline are more likely to be damaged. The county does not require residents to obtain permits to level off their property, as long as the damage occurred within the same year. Historic ridges, formed in previous years, that have since developed vegetation or trees are not included in this exception. Shoreland alteration permits are required to make changes to these.
"Additionally, the Minnesota Department of Natural Resources and the U.S. Army Corps of Engineers may need to be consulted if restoration work extends below the ordinary high-water level of the lake," a news release states.
He encouraged residents to contact county land services to ensure they are following ordinance and he also said they should begin making phone calls now to line up shoreline repair.
"We have a lot of shoreline and we have a limited number of contractors to do that work," Pence said.
Pence said preventing the damage is not always possible, but there are ways to mitigate it. He suggested planting buffers of native vegetation along the water's edge to strengthen it against ice pressure. These buffers also help with erosion from waves once the ice has thawed.
"Ice, it's pretty tough and it's going to move what it wants," Pence said. "But you're going to have a better chance the more vegetated your shoreline is."
Riprap, or a buffer made from rocks, is another option, he said. Although generally the Minnesota Department of Natural Resources and the county suggest vegetation as the preferred buffer alternative, if used appropriately, riprap can prevent some damage.
"Riprap will allow the ice to come up on top and it will curl and fall back on itself," Pence said. "I wouldn't say that riprap is good in every situation, but there are some situations in which riprap can be helpful."
Neff said he had a riprap buffer on his shoreline, but he will have to do some work to get it back to its original location.
"The rocks have all been shoved toward the yard," Neff said. "It's going to take quite a process to get it taken care of."
Pence said one ice heave on the shores of Lake Edward in Merrifield was between eight and 10 feet high. He observed the shoreline there was mowed to the water's edge with no buffers, so it's possible Neff's damage could have been more severe had he not placed riprap.
The ground can also be disturbed by frost heaves. As frost descends deeper into the ground, the water below freezes and expands, causing disturbances in pavement and building foundations. James Swanstrom of Merrifield said on the same night the Schwens heard the loud boom on Gull Lake, he also heard one - 15 miles away.
There was a crack running north/south, and it crossed my entire driveway," Swanstrom wrote in an email. "I am positive it also affected the foundation of my house."
Lukas Marks of the highway department said they sometimes deal with cracks in roadways as a result of frost damage, although this year does not appear to be worse than usual. Marks did note, however, County Road 10 near Bay Lake in western Crow Wing County has sustained damage along with the shoreline.