catchment area vs slough

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. 

slough

noun
  • A type of swamp or shallow lake system, typically formed as or by the backwater of a larger waterway, similar to a bayou with trees. 

  • A small pond, often alkaline, many but not all formed by glacial potholes. 

  • Dead skin on a sore or ulcer. 

  • A muddy or marshy area. 

  • A state of depression. 

  • The skin shed by a snake or other reptile. 

  • A secondary channel of a river delta, usually flushed by the tide. 

verb
  • To shed (skin). 

  • To slide off (like a layer of skin). 

  • To discard. 

  • To commit truancy, be absent from school without permission. 

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