After the end of the last ice age, the Würm Glaciation about 10,000 years ago, the lower Wiese valley had been filled by gravel and boulders from the Feldberg Glacier and the valley floor was formed at about 20 to 30 metres above today's level. As a result of the melting of ice age glaciers, large quantities of meltwater were released and the Wiese cut downwards up to 15 metres below today's level. After repeated gravel deposition and the formation of the present river terraces about 2,500 to 6,000 years ago, the Wiese created the present valley floor with its river meadows and broad meanders by further downward erosion. In the area of the Wiese river delta, these ice age river deposits so strongly affected the course of the Rhine that its river bed was pushed about five kilometres to the southwest, where it flows today around the characteristically shaped Rhine Knee ("Rheinknie"). In Kleinbasel, below the Riehenring bridge, the Wiese was in turn deflected by an existing Nagelfluh gravel bank, which resulted the striking 90° bend in the lower reaches of the Wiese.