Monitoring of Debris Flows with an Improved System Setup at the Lattenbach Catchment, Austria

The Lattenbach creek, District of Landeck, Tyrol is a very active torrent located in a geologic fault zone in the western part of Austria with a catchment area of 5.3 km². The channel separates the Northern Limestone Alps in the North from the Crystalline Alps in the South. The highest elevation in the watershed is around 2900 m above sea level (asl), the confluence with the river Sanna at 840 m asl. Aside from the regular flood events with bedload transport, the torrent produced five debris flows and three debris floods within recent years. Due to the frequent debris flows and debris floods events the torrent is monitored by the Institute of Mountain Risk Engineering since several years. The parameters that are currently measured during an event include meteorological data (rainfall, temperature, etc.) in the upper part of the catchment (station Dawinalpe) and run-off data from the middle and lower reach of the torrent at the villages Grins and Pians. In the last years the monitoring equipment has been constantly improved. Additional to the standard sensors like radar for water level measurements, seismic sensors for ground motion detection and infrasound sensors for acoustic wave identification a high frequency Pulse Doppler Radar has been installed, which provides the opportunity to measure the surface velocity of a debris flow in different range gates. Together with a recently installed 2D-Laser scanner this setup provides the possibility to determine a very precise approximation of the discharge with a high temporal resolution. In August 2015 this setup worked properly for three debris flows, which occurred within eight days. These torrential events proved the applied concept to record data of debris flows in a high temporal resolution.