couloir vs flume

couloir

noun
  • A steep gorge along a mountainside. 

  • A corridor or passage. 

flume

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

  • An open channel or trough used to direct or divert liquids. 

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

How often have the words couloir and flume occurred in a corpus of books? (source: Google Ngram Viewer )