What are Ice Jams?


Spring is the time of year when ice-covered rivers begin to thaw. As this ice breaks up into chunks, they move downstream and can jam in areas where the water flow bends, near bridges and abutments or in shallow areas. The restricted ice can then act as a dam, causing water to back up behind it. River levels behind the ice jam can rise rapidly, often flooding areas upstream. And ice jams that break can quickly release water, causing flash floods and sending huge chunks of ice downstream in the torrent.

NOAA's National Weather Service continuously monitors conditions that lead to flooding and issues forecasts, watches, and warnings when necessary. and NOAA Weather Radio All Hazards are some of your best sources of such critical flood alert information.

Each year, more than 100 deaths occur due to flooding. Why? Because people underestimate the force and power of water. Just six inches of fast-moving flood water can knock you off your feet, and a depth of two feet will float your car! Never try to walk, swim or drive through water-covered roads. Remember: Turn Around Don't Drown™. 

This month’s expert: Larry Wenzel , National Hydrologic Outreach Program Leader, NOAA's National Weather Service, Hydrologic Services Division

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