Natural hazards It became clear 30 years ago: Falli Hölli is lost
It was 30 years ago: on July 19, 1994, the Falli Hölli vacation home settlement above Plasselb FR was finally abandoned. A huge landslide was just about to carry 37 buildings into the depths.
10.07.2024, 05:31
SDA
The event had begun quite harmlessly in March 1994, when drinking water pipes had to be replaced twice in the settlement. In April, the owners of the vacation chalets noticed the first cracks in their houses. In May, it became clear that something bigger was going on in this area of the Senseoberland.
Wide trenches had opened up in the terrain on the eastern slope of the Plasselbschlund and the first houses were suddenly leaning. At first it was thought that the heavy rainfall of the previous months had caused the landslides. It soon became apparent that the entire subsoil had started to move.
Earth on the move
Between 30 and 40 million cubic meters of earth slid down the Schwyberg towards the valley - over a length of up to two kilometers, a width of up to 700 meters and a depth of up to 70 meters. That is an amount equivalent to the contents of 12,000 to 16,000 Olympic swimming pools.
The earth slid up to six meters per day. Most of the chalets were destroyed, as was the Falli Hölli hotel-restaurant, which included a ski lift. The vacation and military camp next to the hotel was also destroyed.
In August 1994, the earth reached the bottom of the valley and thus the Höllbach stream. A dam 400 meters long and 30 meters high was formed. Fortunately, the dam did not burst.
The landslide came to a halt in spring 1995. Since then, the Plasselbschlund has been as quiet as before - the ruins of the houses were demolished in the summer of 1996. Apart from a few remnants and a memorial stone, there is nothing left to remind us of the settlement.
The geologists had warned
The municipality of Plasselb and private promoters wanted to profit from the emerging tourism when the vacation settlement was planned in the early 1970s. The concerns of geologists were thrown to the wind.
Freiburg geologist Hugo Raetzo later told the Freiburger Nachrichten that the slope in question had been sliding for thousands of years. Before 1994, the last time the slope had been in strong motion was in 1612. It simply "woke up from a dormant phase" in 1994. The heavy rainfall contributed to the landslide.
Consequences for spatial planning
The owners of the 37 houses that slid down the slope were ultimately paid a total of CHF 15 million by the Fribourg buildings insurance company. In 1976, the insurance company had opposed the building permit for the military and vacation camp, citing the geology.
The Falli Hölli case had consequences for spatial planning. In 1995, the cantonal government of Fribourg decided to zone out 500,000 square meters of building land in endangered areas. And it was not least because of Falli Hölli that the hazard maps in Switzerland were improved.
