declivity vs upslope

declivity

noun

  • The downward slope of a hill; the downward slope of a curve. 

  • A downward bend in a path. 

  • An inward curve of the exoskeleton of an insect, such as between body segments; a segment of an insect's body where the exoskeleton curves inward. 

upslope

noun

  • an upward slope 

adj

  • in a direction up a slope 

adv

  • up a slope 

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