In June, the long-awaited trip to Switzerland could finally take place - the DEFSUP team (DEbris flow impact Forces on bridge SUPerstructures) around Christian Scheidl and Dirk Proske participated in the latest Austrian-Swiss debris flow networking meeting. In addition to visiting debris flow research facilities, a lively technical exchange with international experts took place.

As part of the FWF-funded project DEFSUP, the Institute for Alpine Natural Hazards (IAN) is using physical model tests to investigate the forces that occur when debris flows hit bridge superstructures. The experimental setup consists of a 4 m long, semicircular flow section with a diameter of 300 mm and an inclination of 20°. Material is released from a rectangular container during a dam failure scenario, accelerated over a length of 1.2 m, and directed into the semicircular section. With an initial mass of 50 kg, different flow heights and velocities are achieved depending on the material composition and water content.

Last year, the experimental flume was prepared in the IAN laboratory and tested in the course of the two master's theses by Lisa Dankwerth and Anna Fuchs. In September 2021, the series of experiments with miniature bridge prototypes will start as part of Caroline Friedl's dissertation. Peter Zelinka, who studies the flow behavior of experimental debris flows in detail, supports her in this work.

In the course of the trip, the BOKU team visited the Swiss Federal Institute for Forest, Snow and Landscape Research in Zurich (WSL) and the Bern University of Applied Sciences (BFH). In addition to technically exciting discussions the team was able to establish new networks and revive already existing ones in order to pave the way for synergies in research. Due to the enthusiasm and discussions about the planned experiments, the exchange about the international status quo of physical debris flow model experiments and the goal to present the work of the IAN and especially the DEFSUP project, the five days in Switzerland were almost too short!