catchment area vs nullah

catchment area

noun
  • An area from which water drains into a particular lake, river, etc.; the catchment area of a large river includes its tributaries. 

  • The area served by a local institution, such as a hospital or school, or by extension, a railway station. 

nullah

noun
  • A stream-bed, ravine, or other watercourse; a drain for rain or floodwater. 

  • An open-air, concrete-lined channel for draining rain or wastewater. 

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