What happens when ice jams?

6:14 PM, Feb 5, 2013   |    comments
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Grand Haven, February 5, 2013.

GRAND HAVEN, Mich. (WZZM) - Ice jams on the Grand and Muskegon River have caused flooding in Ottawa and Mecosta County, but what exactly are ice jams, and what causes them?

At the U.S. 31 drawbridge, you can see the ice build up, but it's not necessary the freezing temperatures that are the problem: It is the freezing and thawing. Ice forms large chunks, which break off during a thaw and travel down the river where they get stuck.

In Grand Haven, the ice is getting stuck at the bridge. If the ice jam grows, it can become an ice dam which blocks all water from passing through. That leads to flooding upstream.

Larry Mierle has lived by the Grand River in Grand Haven for 70 years and has seen his share of ice jams. He says this ice jam is nothing special. "The last few years and in the last couple of decades it is actually about the same," says Mierle. "Years ago, I lived right here and used to catch the school bus. I used to see the ice stack up like a deck of cards."

Mierle says the danger with the current ice jam is if it breaks all at once and rushes down the river. "In the past, the ice jam had broken the dock and snapped the wooden pillars like matchsticks."

Mierle also points out just because the river is ice doesn't mean it is safe to cross, as the ice is shifting and there are holes where you can fall through.

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