The Weather Notebook: Breaking Up Ice Jams

Breaking Up Ice Jams
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Think of it, chunks of ice the size of furniture; thousands of tons of ice packed into a river channel with the flowing water looking for a way around it. Sometimes this new route goes right through a road, a yard, a town, or a city. The whole mess is due to an ice jam. Hi, I'm Dave Thurlow and this is The Weather Notebook.

Latest real-time image of a new low-cost structure to control ice breakup on the Lamoille River in Hardwick, Vermont. It consists of four slope-faced, 42-ton granite blocks placed in the river adjacent to a natural floodplain. CRREL Photo
To find out about ice jams I visited the Cold Regions Research & Engineering Lab in Hanover, NH. There I spoke with Steve Daly, a hydraulic engineer, who explained how ice jams form. He used the example of a river in Vermont.

"There's a case where the Winooski River had an ice cover, quickly it broke up, the ice cover ran downstream and jammed at one location. That jam formed a large blockage to flow, which caused the stages, that is the water surface elevation upstream of the jam to rise and diverted the river through the town."

Because this type of flooding oftentimes happens quicker than a flood caused by heavy rain the need for a solution was immediate. In a nearby river, a plan was tested. 4 large granite blocks were placed upstream from the local town.

"When the ice cover broke up, it hit these granite blocks and actually stopped there. And the flow went around in the flood plain and there's trees in the flood plain, they strained the ice out and allowed the flow to go around but held the ice in place. And then that prevented the ice jam from occurring down in town. And it's been quite successful."

A simple solution to a potential very expensive problem. For more, be sure to visit our website at mountwashington.org. Thanks to Subaru and the National Science Foundation.