Minn. geology combined with wet soil is recipe for mudslides

Live near a sloping hill? Satish Gupta thinks you should be worried.

Gupta, professor at the University of Minnesota's Department of Soil, Water and Climate, has his eye on mudslides — like the one that sent a Mississippi River bank plummeting last week near the University of Minnesota's Fairview Medical Center campus.

Or the one that tragically killed two fourth-grade students in Lilydale Regional Park last year.

Or the many that slid onto Highway 169 near Mankato last week, one of which was captured on a Minnesota trooper's dash cam.

Gupta told MPR's Tom Crann that Minnesota's geology — combined with the heavy rain we've been seeing — creates conditions ripe for mudslides.

That's because bedrock, or sediments packed tightly by the weight of glaciers that once blanketed Minnesota, sits below surface soils in many areas.

In heavy rains, these dense layers prevent water from flowing downward to join groundwater. Surface soils then become saturated and heavy. If these soils are on a sloping hill, the weight of gravity will simply pull them down.

What can be done to prevent mudslides? Dry out the soil, Gupta says.

One tactic would be to place a pipe with holes in the soil to serve as a drainpipe, but depending on the depth of that soil. Another option would be to carve out terraces on the slope, draining each individually with pipes. But these projects can quickly become expensive.

KMSP-TV