From PathfinderWiki
The Iceflow originates in Winterwall Glacier and flows south to join the Rimeflow River.

The Iceflow river flows out of the vast Winterwall Glacier and then forms, for its entire length outside the glacier, the border between the nations of Irrisen and the Lands of the Linnorm Kings. As the border is contested, the western banks are heavily patrolled by Freyr Darkwine's Blackravens as they are in his kingdom of Hagreach. After about 170 miles of meandering, the river becomes a tributary of the mighty Rimeflow River.123