Why are spring breakup ice jams usually more destructive than freeze-up ice jams?

Spring breakup ice jams are typically more destructive than freeze-up ice jams primarily because they involve significantly larger quantities of ice.12

During the spring, increased runoff from snowmelt and rain raises river water levels and exerts greater forces on the ice cover. When these forces exceed the strength of the ice, the cover breaks up and is transported downstream, where it can accumulate in volumes that exceed the river's transport capacity.12

The resulting jams are dangerous for several reasons:
* Sudden Flooding: The accumulation of stacked and clustered ice can build to thicknesses sufficient to raise water levels rapidly, causing localized and regional flooding.12
* Physical Impact: The moving ice itself can collide with and severely damage infrastructure, including the destruction of bridges.12
* Dynamic Failure: Jams may break loose and reform multiple times as they move downstream, creating a recurring threat to areas along the river.12

In contrast, freeze-up jams generally form as water freezes in narrow river stretches or at lake outlets, typically involving less total ice volume than the massive, forced movement seen during spring breakups.2