cataract vs flash flood

cataract

noun
  • A flood of water. 

  • A clouding of the lens in the eye leading to a decrease in vision. 

  • A large waterfall; steep rapids in a river. 

  • An overwhelming downpour or rush. 

flash flood

noun
  • A sudden, rapid flood, usually of short duration and local impact. 

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