noun which may take the genitive case particle 'no'
along the river; riverside
Used as a noun or no-adjective to describe a location, path, or area that runs alongside a river.
川沿いの道を散歩した。
I took a walk along the riverside path.
この町には川沿いに桜並木がある。
In this town, there is a row of cherry trees along the river.
Compound of 川 (kawa, 'river') + 沿い (zoi, 'along'), the continuative form of 沿う (sou, 'to run along').