Wikipedia
Jeetzel
The river Jeetzel, which begins in the Altmark under the name Jeetze, flows from Saxony-Anhalt through Lower Saxony, in Germany. From its source near the village of Dönitz, it flows north through Beetzendorf, Salzwedel, Wustrow, Lüchow and Dannenberg, before joining the Elbe in Hitzacker. Its total length is .
A left tributary of the Elbe, the Jeetzel has itself several tributaries, including the Salzwedel Dumme and the Wustrow Dumme. The name is Slavic, and means ash (tree)- stream.
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.