Idrija mercury mine used to be the second biggest in the world, and needed enormous amounts of timber to operate. The timber was cut on nearby hills, but lacking roads (and efficient means of transportation), the most suitable method to bring it to the mine was floating along natural water routes. The tributaries of Idrijca river do not have that much water, so from the 16th century on engineers constructed "klavže", water barriers, to accumulate water. When the wood was prepared, the barrier was opened and the wood would float down to the "rakes" in Idrija.
Kanomeljske klavže were built under Napoleon, in 1812 and were in use until 1812. In 2015 the were nicely renovated and very worth visiting. They are accessible on foot (1 km walk from the road) or by bicycle (gravel/mtb).