viaduct vs waterway

viaduct

noun
  • A bridge with several spans that carries road or rail traffic over a valley or other obstacles. 

waterway

noun
  • A body of water, such as a river, channel or canal, that is navigable. 

  • A conduit or watercourse, such as on the deck of a ship, to drain water. 

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