alluvion vs catastrophe

alluvion

noun
  • The increase in the area of land due to the deposition of sediment (alluvium) by a river. 

catastrophe

noun
  • A disaster beyond expectations. 

  • Any large and disastrous event of great significance. 

  • The dramatic event that initiates the resolution of the plot; the dénouement. 

  • A type of bifurcation, where a system shifts between two stable states. 

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