Why do ice dams form on the Vistula River in spring?

Ice dams form on the Vistula River in spring primarily due to the breakup of the winter ice cover. As temperatures rise, snowmelt and spring rains increase the river's flow, which raises the water level and breaks the ice loose from the banks.123

This dislodged ice is then transported downstream. When the quantity of ice exceeds the river's transport capacity—often occurring where the river's slope changes from steeper to milder or where moving ice encounters an intact ice cover—the ice accumulates and forms a jam. These dams are particularly dangerous on the Vistula because the river's low gradient and abundant sandbanks can impede the flow of ice and water, leading to significant flooding of surrounding areas and potential damage to bridges and embankments.32