Ice Jams An Ever-Present Winter and Springtime Threat

Melting ice on lakes, rivers and streams can produce a major hazard, ice jams. Blocks of ice can clog waterways and produce major flooding.

Heavy snowfall and extended cold snaps during the winter months often create a layer of ice on waterways, particularly across the northern Rockies, Upper Midwest, Great Lakes and interior Northeast.  As temperatures warm, the ice begins to melt and break-up, forming chunks.

Typically, these mini icebergs pose no problem.  However, when chunks of ice become lodged along bends in waterways or start piling up in shallow or narrow passages, the situation can quickly become dangerous.  These so-called ice jams have in the past escalated into life-threatening flooding in mere minutes.

On March 11, 1992, Montpelier, Vt., experienced firsthand the destruction an ice jam can cause.  An accumulation of ice chunks in the Winooski River near the Bailey Avenue Bridge effectively formed a natural dam, stopping the flow of the river.  Water quickly piled up behind this jam and began pouring into the historic downtown area.  

Within a matter of minutes, a peaceful morning became a chaotic scene, with 3 to 5 feet of water flowing through the Montpelier business district.  Cars were submerged, and homes and businesses flooded.

Not only do ice jams represent a real threat to life and property, they can also have far-reaching economic consequences.  Lost revenue due to suspended commercial navigation and resulting shortages of supplies as well as damage to bridges and other infrastructure costs the U.S. millions of dollars every year.

Although little can be done to stop these forces of nature, being ready to act quickly in the event of a jam can go a long way in preventing personal tragedy.  When a flooding situation becomes apparent, the National Weather Service will issue flood warnings for the affected area.