A flume is a human-made channel for water in the form of an open declined gravity chute whose walls are raised above the surrounding terrain, in contrast to a trench or ditch. Flumes lead water from a diversion dam or weir to a desired location. Many flumes took the form of wooden troughs elevated on trestles, often following the natural contours of the land. Originating as a part of a mill race, they were later used in the transportation of logs in the logging industry. They were also extensively used in hydraulic mining and working placer deposits for gold, tin and other heavy minerals.