There are problems with the example illustrated by this page and simplifications implied. Isterdalen (illustrated) is an example of a glacial trough which exhibits a large step (downwards) in its long profile, but, as can be seen in one of the pictures, it is a U-shaped valley up-stream of this point as well. A better example is the Loch Avon basin of the Cairngorms in Scotland which starts at a trough-end, and the land up-stream shows little or no modification by glacial processes.