Sunday, March 13, 2011

Ice Jam on the Lower Chippewa River

Ice jam on the Lower Chippewa River

This winter's near-record snow has finally started to melt, and the run-off is flowing into the Lower Chippewa.  The ice and snow covering the river has started to melt too.

But it was a chilly 26º F this morning when we went for a ride through the backwaters.  I was surprised to discover an ice jam behind the Riverview Community Center in Durand.

The Ice Jam down-river from Durand

What causes an ice jam?

When water from snow melt (and/or rain) increases water flow and raises water levels, the water pushes against the sheet of ice covering the surface of the river.  The rising water breaks up the surface ice into chunks that float downstream.  If they hit an obstruction - a frozen section of the river, a bridge or a shallow - ice piles up creating an "ice jam."

When the water flow is obstructed at an ice jam - flooding can occur up-river. 

Fortunately for Durand, this ice jam is small.  It will probably melt tomorrow when the temperature hits 40º F.

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