At least eight people have been reported dead and nine missing in the floods in Germany, Austria, Switzerland and the Czech Republic.
The Danube hit its highest level since 1501 in Passau on Monday before receding a half meter (yard) by Tuesday morning. German Chancellor Angela Merkel was on her way to the city, where waters were expected to recede by another 2 meters (yards) by midday.
But farther downstream in Regensburg, streets were being closed as the Danube rose.
Other rivers were flooding cities in the eastern states of Thuringia, Saxony Anhalt, Saxony and Brandenburg.