flum

An open channel or trough used to direct or divert liquids, especially to carry materials (logs, mined material, etc) or people (as a water slide), especially (but not always) one where the walls are raised above the surrounding terrain rather than recessed like a ditch.

A ravine or gorge, usually one with water running through.

(transitive) To transport (logs of wood) by floating them along a water-filled channel or trough.