Why do ice jams repeatedly form and break apart in some rivers?

Ice jams repeatedly form and break apart because of the dynamic interaction between rising water levels and downstream ice conditions. When an ice jam forms, water builds up behind the blockage, increasing the pressure and force exerted on the ice. Eventually, this pressure causes the jam to break loose and move downstream, where it may encounter another stable ice cover or a section of the river with lower transport capacity, causing the jam to reform.12

This cycle is particularly common in northerly flowing rivers, where upstream ice is freed by spring thaws and moves toward colder, more stable ice covers downstream. As the ice moves, it can collide with and damage structures like bridges, and the repeated formation and failure of these jams can lead to significant, recurring flooding.12