February is Flood Safety Month and a time to brush up on ice jam safety. Streams can carry chunks of floating ice. If there is some sort of obstruction of the stream’s current, like a river bend, dam or bridge, chunks of ice can accrue and create a jam. There are two ways an ice jam can happen. A freeze-up jam happens when cold air freezes open water, creating large amounts of ice that can jam a stream. However, the most common ice jam, a break-up jam, happens when ice quickly thaws or when a runoff entering a river system and breaks up the ice. If the dam or bridge breaks then a flash flood can happen. In the Midwest, freeze-up ice jams are fairly common and typically occur late November to mid-February. Break-up jams can occur between mid-February and late March.[1]
Nebraska Department of Natural Resources, state and federal agencies, and local governments monitor river conditions. To learn more about ice and ice jams visit http://dnr.nebraska.gov/fpm/ice-jam.
[1] NOAA National Weather Service, Ice Jams, (October 2011); ://www.crh.noaa.gov/Image/dvn/downloads/backgrounder_DVN_Ice_Jams.pdf
Picture is showing the January 2015 ice jam of the Papio-Missouri River; http://dnr.nebraska.gov/fpm/ice-jam-january-2015