Vorderrhein

The Vorderrhein — the Anterior Rhine — is the longer of the two source rivers of the Rhine, rising from Lake Toma near the Oberalp Pass in the Swiss canton of Graubünden and flowing 76 kilometers northeast to its confluence with the Hinterrhein at Reichenau. For boaters, the Vorderrhein means one thing: the Ruinaulta. Known as the Swiss Grand Canyon, the Ruinaulta is a 13-kilometer limestone gorge between Ilanz and Reichenau carved through the massive Flims Rockslide — the largest known postglacial landslide in the Alps, which deposited approximately 9 cubic kilometers of rock into the valley roughly 10,000 years ago. The Rhine has spent the intervening millennia cutting a gorge through this debris, producing a canyon of white limestone walls, turquoise glacial water, dense riverside forest, and Class II-III rapids that make it the finest whitewater day run in Switzerland. The water color — that distinctive alpine turquoise — comes from glacial flour suspended in snowmelt from the Surselva peaks. The Ruinaulta is a UNESCO-level geological feature, a national landscape of significance, and one of the few places in Central Europe where a river still runs through a canyon with the character of genuine wilderness.

The Ruinaulta gorge is carved entirely through the Flims Rockslide — the largest known postglacial landslide in the Alps. Approximately 10,000 years ago, roughly 9 cubic kilometers of limestone collapsed from the Flimserstein mountain into the Rhine valley, damming the river and creating a lake. As the lake drained and the river reestablished its course, it carved the Ruinaulta through the compacted landslide debris — a gorge up to 400 meters deep through material that is geologically an instant old. The white limestone walls of the gorge are not bedrock — they are the cemented, eroded face of the rockslide deposit.

The Ruinaulta gorge is one of the most ecologically intact river corridors in the Alps. The gorge's relative inaccessibility has protected riverside forests from development. The Vorderrhein supports native brown trout populations, and the gorge walls provide nesting habitat for raptors including golden eagle.