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What are ice jams, and why do they happen?

Following the milder temperatures and widespread rain moving across the area, we are watching for ice jams across area rivers, streams and creeks.

By: Katie McGraw

Posted

With the milder temperatures, a thaw has been occurring over the last few days. We are also tracking widespread rain over the next two days. Therefore, the risk of ice jams or ice dams is increasing. Ice jams happen when chunks of ice clump together to block the flow of a river. This can then cause flooding in communities near the river.

WHY DO ICE JAMS HAPPEN?

As temperatures warm, rapidly melting snow and ice causes rivers and streams to rise or swell. In the meantime, the layer of ice on top starts to break apart into chunks of ice.

The rushing river carries large chunks of ice downstream; sometimes, a group of ice chunks gets stuck in a narrow river passage. The ice chunks form an ice jam, which blocks the river's natural flow.

Ice jams can be dangerous for people living in towns nearby. Because the river is blocked, the rushing water has nowhere to go, and it can cause flooding in the surrounding area.