landflood vs tributary

landflood

noun
  • An overflowing of land by river; an inundation or freshet. 

tributary

noun
  • A natural water stream that flows into a larger river or other body of water. 

  • A nation, state, or other entity that pays tribute. 

  • A vein which drains into a another vein. 

adj
  • Related to the paying of tribute. 

  • Yielding supplies of any kind; serving to form or make up, a greater object of the same kind, as a part, branch, etc.; contributing. 

  • subordinate; inferior 

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