Historically, when the Elbe rose too high, it would flooded the Jeetzel, which flowed "backwards" and flooded the surrounding area. Today, a system of canals prevents such flooding.
^Hans-Joachim Uhlemann and Martin Eckoldt, Kleine Nebenflüsse der Elbe oberhalb des Tidegebietes, published in Hans-Georg Braun's 1988 Flüsse und Kanäle.