And in general hiking, referring to streams and rivers one may follow or cross, there are the "true left" and "true right" banks of the stream. Meaning, left or right looking the way the water is flowing: downstream.
"East bank" and "west bank" are also used for the sides of a watercourse that flows generally north/south, even for bits of it that are flowing east/west or have curved around to flow south/north. Which is why West St. Paul (Minnesota) is directly south of St. Paul proper -- it's on the "west bank" of the Mississippi, while St. Paul is on the "east bank".
(Same story, mutadis mutandis, for "north bank" and "south bank" of generally east/west-flowing rivers.)
