Impermeable

Impermeable rock restricts this movement, encouraging more rapid runoff. Soil conditions matter too: clay-rich, frozen, saturated or compacted soil allows less infiltration.

Much of its bedrock is impermeable, and the peat is saturated for more than six months of the year. Impermeable rock limits water passing down into the ground, while already saturated peat has little capacity to store additional rainfall. More water therefore flows over the surface and reaches river channels quickly.