- Anchor Ice Accumulation
- Active frazil deposited on bed
- Grows upward from stream bed, raising water level
- In turbulent, shallow areas
- Occurs during freeze-up
- Referred to as an 'ice dam'
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- Surface Congestion
- Layer of frazil pans and rafts
- Forms at constriction or floating obstacles
- In slow-moving water
- Occurs at freeze-up or break-up
- Referred to as a 'surface jam'
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- Undercover transport/deposition
- Frazil/small blocks carried beneath ice cover come to rest in slow-moving areas
- Accumulations build until velocity too great to allow deposition
- Tends to fill deep sections with accumulation following topography of streambed
- Referred to as a 'hanging dam'
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- Submergence/Frontal Progression
- Pans/blocks submerge at upstream edge of jam or obstacle
- Jam progresses upstream at thickness greater than individual pieces
- Little transport beneath jam
- Thickness great enough to withstand increased external forces
- Referred to as 'narrow channel jam'
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- Failure and Thickening
- Existing jam fails when downstream forces surpass jam strength
- Cover transported downstream until resisting force increases
- Cover thickens when it comes to rest, increasing jam strength
- Commonly occurs with break-up jams
- Referred to as 'wide channel jam'
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- Pressure Ridge Ice Jam
- Line or wall of broken ice forced up by pressure.
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