ST. PAUL, Minn. (AP) — Unpredictable and destructive ice jams are upending some residents who live along Minnesota waterways during this spring flooding season.
More than 40 people had to be evacuated from a Waite Park restaurant recently when an ice jam caused the Sauk River to suddenly rise and flood the building.
U.S. Geological Survey hydrologist James Fallon told Minnesota Public Radio News that ice jams usually form in the spring as snow melts and a river's volume and flow increase. The water lifts the ice and breaks it into chunks.
Oftentimes, the chunks of ice get carried downstream, melting along the way without causing issues. But Fallon said ice that's too thick can cause chunks to block the water's flow. The buildup can lead to flooding and damage to structures, such as bridges, buildings or docks.
It's difficult to predict ice jams because they can form quickly and at random, Fallon said.
Local agencies monitor for problematic ice jams and try to break them up before significant damage is caused.
Delano city crews used an excavator recently to break up a large ice jam that was caused by the South Fork Crow River rising to major flood stage.
The frigid weather and snow in January helped create thick ice on Minnesota rivers and lake, creating nearly perfect conditions for ice jams, according to Fallon.
Fallon said he's seen more ice jams in southern Minnesota over the last two weeks than during any year in the past two decades he's worked in stream monitoring.
Luckily, this year's gradual sprig warming is reducing the likelihood of significant flooding. But Fallon said the slow warmup has also kept river flow rates lower than if the melt happened all at once, which means bodies of water may not have the capacity to carry the ice chunks away.