Die Gefahr vom See

"On my guided tours to the former Lüschersee, I always show people a marmot burrow. This shows particularly well that the soil material in the former lake basin is completely different from the surrounding area. When the lake still existed, dead aquatic plants as well as mud, lime and clay were deposited. This layer of lime clay is estimated to be about 80 centimeters. In the former lake basin, therefore, a completely different vegetation grows than in the surrounding landscape, which is why you can see the shoreline so well. In the lake basin, for example, there are many thistles; So be careful where you sit down."

The shales of the Nolla clay weather easily, but are impermeable to water. As a result, rainwater accumulates in the uppermost layers, causing a mushy mass. Since the layers on the Heinzenberg slope against the valley, the whole slope slides slowly downhill. In the uppermost part of the slope, on the ridge, the mountain breaks apart; this creates a restless topography. The locally formed depressions are filled with water.

In the case of the former Lüschersee

, it was feared that the water from the Lüschersee without surface runoff would accelerate the landslide process. As early as 1742, the first voices are known that suspected a connection between the Lüschersee and the landslides on the Heinzenberg.

The fears of the local population are also evident in the legend of Lake Lüscher: "In the bottom of the lake, the folk legend lets a dragon dwell, which roars when the weather changes. Every hundred years, the monster emerges from the lake and, leaving a trail of devastation behind, rolls down the mountain." (Gino Romegialli: Das Ende des Lüschersees. Verlag Desertina, Chur, 2012.)

When reading the legend, one involuntarily thinks of periodic floods, a great threat to the villages and settlements on the mountain and to the Domleschg. Thus, the underground outflow of water from the Lüschersee was classified by several engineers as an important reason for the landslides and the measure to empty the Lüschersee by the federal government was decided in 1906. 

The lake

outlet The
plan was to build a water drainage tunnel, which would allow the gradual draining of the lake water. The construction of the tunnel proved to be a challenge for the construction company. The construction workers had several deviations of the tunnel axis as well as too little wood on site for the excavation of the tunnel and shortly before completion a misblasting claimed three dead and three injured. After all, the Lüschersee had almost no water in the winter of 1910 during the tunnel construction and the lakeside section could be dug in the dry.

To date, there is no clarity as to whether the lake outlet really contributed to slope stabilization. This would require comprehensive geological investigations. Many wish this beautiful mountain lake back – pure reverie or perhaps reality?

The re-damming
Extensive investigations showed that the lake had only a minor influence on it, which is why it has now been sealed again and fills with water with the melting snow in 2022. The project will be closely monitored during the test phase to rule out any influence on the landslides. On June 23, 2022, a excursions to the former Lüschersee will take place.