Arctic ice jams can raise river levels thirty feet

When the spring thaw begins in the Arctic, the ice does not simply melt; it shatters into jagged slabs that pile up in narrow river bends. These frozen blockades act like natural dams, forcing the water behind them to rise as much as thirty feet in just a few hours. This hydraulic pressure is so immense that while the upstream banks are swallowed by water, the riverbed beneath the jam is scoured away, eroding more than three feet of sediment in a single day.