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Black Hills Potential For Mudslides

Officials in Washington State are switching from rescue to recovery mode in the tragic mudslide that buried several homes there late last week.

More than 170 people are still as missing in the disaster.  The death toll stands at over a dozen and is expected to rise.

The Black Hills are not immune these sort of disasters.   Geologists sometimes call these events “debris flows.”  They can move like tsunamis, but with the constancy of wet concrete.  

Officials note a significant debris flow in Deadwood that damaged homes and swept away vehicles after heavy rains soaked the 2002 Grizzly Gulch fire area.   

Perry Rahn is a Professor Emeritus of Geology at the South Dakota School of Mines.    He adds that it’s important for anyone digging into a hill side for a new foundation or road to have a geologist assess the hazard potential of the area.

“What usually happens I’ve seen is they just build and then later have some problem.  And, I think one of the easy remedies is to keep the water out away from your house.  In other words, where the roof drains, where that exits, keep it away from the foundation of your house,” says Rahn.   

Rhan says water is a key ingredient that triggers mudslides.   He says these kinds of slides are more apt to occur in years with above average precipitation.