Any good hiking trails close to Freiburg?
Freiburg is surrounded with the Black Forest, thus naturally there are numerous hiking trails. While I am not a hiking enthusiast, I can still recommend the hiking trail for Todtnau, as it does have waterfalls. Also you might want to look at the app Komoot, it has loads of information trails around the globe.
Zweribach waterfalls close to St. Märgen (you can reach St. Märgen via Bus from Kirchzarten). Start and end are both in St. Märgen.
Waterfall trail from Feldberg to Todtnauberg has two large waterfalls: Fahler waterfall and Todtnau waterfall. The trail starts at Feldberg Hebelhof (can be reached via Bus) and ends at a bus stop in Todtnauberg.