course of a river; land along a river
Refers to the path a river takes or the area alongside it. Often used in geographical or descriptive contexts.
This river course has been a key transportation route since ancient times.
川筋の集落では、昔ながらの生活が残っている。
In the settlements along the river, traditional ways of life still remain.
Compound of 川 (kawa, 'river') and 筋 (suji, 'line, course'). The reading かわすじ is a straightforward combination of the kun'yomi readings of the two kanji.