ABSTRACT
Several large floods in the Swiss Alps caused considerable damage, blocking major roads and train lines, during the summer of 1987. This chapter describes debris flows occurring in short and steep side valleys as the Varuna, the Minstiger or Geren valley. It discusses events in the 40 km long Reuss valley, which led to the blockage of the most important north-south connection over the Gotthard pass. In the Minstiger valley, the debris flow must be assumed to have started in a steep rock gorge filled with morainic debris which had become ice free within the last few decades only. Loose material within the main starting zone of the large debris flow in the Minstiger valley, the rock gorge beneath the Minstiger glacier, has now been essentially removed. River mechanics and river morphology tells us that unless certain threshold values are exceeded, no erosion or meandering takes place.
