Ben,
There are clubs but as always it easier with your own motor. Germany has some sweet kayaking but as you seem to like it steep and technical I would recommend you base your self in the south of the Country. Munich/Ausburg or any other town in Bayern would be a good option possible the best. Konstanz/Freiburg are all uni towns and close to the Alps. Just look at a map check out where the alps are and your options
As for more info talk to these boys
www.alpiner-kajak-club.de
The will defintely be able to point your in the direction of some V runs
Try to get here as early as possible the season is best in spring/summer but there is some runs for fall to boot. But winter can be cold. A bit of warm weather/ hard rain will bring in the Black Forest and some of the smaller mountain run offs
Here is a river map of Austria
www.kajaktour.de/oesterreich.htm
Switzerland
www.kajaktour.de/schweiz.htm
Enjoy your trip its a nice place