downslope
/ˈdaʊnˌskaʊl/Definitions
1. noun
a slope or incline on the downward side of a hill or mountain
“The hikers had to navigate through a steep downslope on the mountain trail.”
2. adverb
in a downward direction or on the downward side
“The skiers sped downslope, their skis gliding smoothly over the snow.”