backwater

A section of river where the current is absent or reversed — water backed up behind an obstruction, in a side channel, or in a flooded area adjacent to the main flow. Backwaters are quiet, warm, and biologically rich: nurseries for young fish, habitat for amphibians and invertebrates, and feeding grounds for wading birds. The word's metaphorical sense — a place bypassed by progress — carries a judgment the ecological sense does not deserve.