What does the word drainage mean?

Usage examples for drainage

  1. There appears also, in many cases, to be such a correspondence in the openings of caverns on opposite sides of some of the valleys, both large and small, as to incline one to suspect that they originally belonged to a series of tunnels and galleries which were continuous before the present system of drainage came into play, or before the existing valleys were scooped out. – The Antiquity of Man by Charles Lyell
  2. Since that time several canals have been finished, and I have no doubt, as the country becomes more populous, others may be undertaken for the purposes of drainage and internal communications; but my own personal knowledge has satisfied me that Railroads would be far more useful and a far more ultimate benefit, for there is no doubt that the waters of Canada have a general inclination to subside. – A Letter from Major Robert Carmichael-Smyth to His Friend, the Author of 'The Clockmaker' by Robert Carmichael-Smyth
  3. 1835. Smith of Deanston, the father of modern drainage. – A Short History of English Agriculture by W. H. R. Curtler