hanging dam

ice formation

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Last updated

June 29, 2026

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A hanging dam is a significant accumulation of ice that can form in rivers. This occurs when frazil ice, produced upstream in colder conditions, is carried downstream. Beneath an existing ice cover, this frazil ice can deposit and build up to great depths, potentially blocking a large portion of the river's flow.1

In smaller, shallower streams, ice formations can be more varied. They may include shore ice, anchor ice, and smaller hanging-dam-like structures. In slower-moving areas, sheet ice can form. Groundwater can influence these formations by melting ice during warmer periods, but if all the water freezes, subsequent inflows can create large ice buildups known as icings or Aufeis. These can become so thick they completely block waterways. Ice dams, in general, can create barriers and lead to waterfalls.12

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ice in lakes and rivers
Ice buildups
…large accumulations that are called hanging dams. Such deposits may be of great depth and may actually block large portions of the river’s flow. In smaller, shallower streams, similar ice formations may be combinations of shore ice, anchor ice deposits, small hanging-dam-like accumulations, and (over slower-flowing areas) sheet ice.
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…large accumulations that are called hanging dams. Such deposits may be of great depth and may actually block large portions of the river’s flow. In smaller, shallower streams, similar ice formations may be combinations of shore ice, anchor ice deposits, small hanging-dam-like accumulations, and (over slower-flowing areas) sheet ice.
Read More