An American gets used to flooding reports up in Minnesota, Missouri and along the Mississippi River. It's part of the lifestyle you accept if you live near flood-prone areas.
Germany is mostly the same way. There are thousands of cities, towns, and villages....built along rivers and streams.
For some locations.....you might get one decent flooding every twenty years, usually from a single storm dumping several inches of rain in a matter of one hour. Some major cities are built right on top of the river, and have some type of flooding every single year. It's the price that folks pay....for the unique experience of living along the riverbanks.
Doing something to avoid the floods? This has generally been talked about by the smart engineering guys for a long time. Some ideas have centered around having a 'dumping-ground' where you'd create a huge pit of sorts, and just allow the excess river water to pour into some field with high walls, and attempt to temporary store the water there until the river gets back to lesser levels.
In this case, you'd have to pay the farmers for use of the land, and the loss of crops. So far, this idea hasn't advanced too fr.
Higher walls along the rivers? In some cases, it's already been done and helped. There's a limit to this, and locals always have a priority with being able to see the river and it's part of the landscape.
My general advice for Americans moving into Germany....look at the area that you want to rent an apartment, and think about the consequences. You might have a great chance to rent a place right on top of a riverbank. I'd pause to think about what might happen, and just exercise some caution. And if the scenery is a big deal.....just buy lots of insurance.