This is a sonar image of the bottom of the Allegheny River in Pool 5. The dashed line going from top to bottom indicates the center of boat taking the sonar samples. Left of that, a very conspicuous 'bite' out of the river bottom from a clamshell dredger. Further left, the undisturbed, rippled river bed. To the right, a series of continuous, clamshell dredging. At the bottom of each pit, fine sediments accumulate, decomposition takes places without oxygen, and colder temperatures prevail, all detrimental to river-dwelling animals.

This document is part of the Resource Center of the Watershed Atlas of the Allegheny River.