New England Faces Higher Ice Jam Flood Risk as Spring Approaches

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After an exceptionally cold winter, rivers across New England are becoming more vulnerable to ice jams, raising the risk of flooding as the region heads toward spring. Ice jams form when chunks of ice floating along a river or stream pile up and restrict the flow of water, forcing water to back up and sometimes leading to sudden and significant flooding.

Why it matters

Ice jams can pose a serious threat to communities located along rivers in New England, as the sudden and unpredictable flooding they can cause can lead to property damage, transportation disruptions, and even threats to public safety. Understanding the factors that contribute to increased ice jam risk is crucial for local officials and residents to prepare and mitigate the potential impacts.

The details

This winter, Portland, Maine has recorded 42 days below freezing since December 1, allowing the ground and waterways to freeze more deeply. Inland areas have experienced even colder days and nights. As temperatures warm toward the end of the season, the ice on rivers begins to break apart and move downstream, where it can get stuck at narrow spots, bends in the river, or structures like bridges, creating ice jams. The deeper freeze this winter increases the potential for ice jams this spring. Additionally, as the snowpack melts, the added water flowing into rivers downstream from the mountains can raise river levels and further increase the risk of ice jam flooding.

• As of February 17, this has been Portland's coldest winter since 2003.
• The next 3-4 weeks are expected to be slightly warmer than average, which could bring more days above freezing and rain events that, combined with melting ice, may increase the risk of stronger and more impactful ice jams.