Up the River

Hal leaves his home on the river and paddles his canoe at a steady constant pace upstream. He reaches a spot that he knows is one mile from his home. At this moment, a gust of wind blows his hat off his head into the water. He doesn’t stop to pick it up, and continues to paddle upstream for an additional ten minutes. He then decides to turn and paddle home, paddling with the same steady methodical pace as before. When he reaches his home, he notices his hat being carried under his pier by the gentle current of the river.

How fast is the current of the river traveling?