Research

Hydrographic survey of five scours in the riverbed of the river Wienfluss 1) Hydrographic survey a) Unmanned survey boat for use in very small waters The survey boat includes a semi-autonomous navigation unit with survey-grade satellite navigation unit (GNSS) with double antenna system for precise alignment of the survey boat. b) Multibeam echo sounder (MBES) Norbit iWBMS (minimum water depth under the transducer: 0.2 m) The MBES scans the bottom of the riverbed with 512 beams per ping. The possibility of swiveling the fan allows adjacent areas to be detected which cannot be navigated by boat due to the water depth, but in particular steeply rising bank areas (drop-offs) can be detected. c) Post-processing of the echo sounder measurement data The existing shallow water depths and narrow scour areas cause strong multipath reflections of the signals, which require extensive manual post-processing of the measurement data. This includes manually cleaning the point cloud of multipath reflections and filtering the data sets for subsequent DTM creation. DTM creation of the recorded underwater area with a grid width of 20 cm 2) Terrestrial photogrammetric survey and evaluation of the scour edge areas Due to the greatly reduced water level caused by the pumping out of the Wien River, the scours are no longer covered with water up to their upper edge. This means that, contrary to the original plan, the scour edge areas cannot be recorded with the echo sounder. For this reason, it was decided to carry out a photogrammetric survey and evaluation of the scour edge areas. The photogrammetric images are analyzed using the structure from motion (SFM) method and the surface is displayed as a 3D point cloud. The point cloud is filtered and artifacts from the evaluation are removed manually. In order to merge the underwater DTMs with the surface DTMs of the scour areas, the water-covered areas of the surface model are masked out manually.

Climate change is altering the geomorphological processes in high alpine regions. In the MurMo project, the Teufenbach and the Lachegggraben in the Rauristal, Salzburg, are being equipped with measuring stations by the Institute for Alpine Natural Hazards, University of Natural Resources and Life Sciences (BOKU) on behalf of the Forest Engineering Service for Torrent and Avalanche Control (WLV). The aim of the project is to document the activity of debris flows, the flow dynamics and the deposition geometries of debris flows and to prepare the data for the further development, testing and calibration of simulation models. The duration of the project is 3 years.

Torrent and avalanche control structures are core elements with a central protective function against natural hazards in the Alps. In the event of failure, there is an increased risk to settlements and infrastructure. In the area of torrential processes, key structures are often designed so that, in the event of an incident, they retain the entrained bedload (sediment) and wildwood at the structure's location. However, once the retention volume has been used up, the protective function of the key structure is severely impaired or barely existent. For these reasons and because an increase in sediment input is expected due to climate change, the torrent and avalanche control authorities see a particular need for a standardized nationwide monitoring and warning system for key structures for torrent processes. The intention of our consortium (IBTP Koschuch, Almosys, IAN, ÖBB, WLV) is to develop and establish an automated in-situ monitoring and warning system for key torrent control structures. Integrated into an Internet of Things (IoT) scheme, the system should be able to provide information on the filling level of the connected protective structures at any time via user-friendly remote access and automatically issue a warning to decision-makers in the event of time-critical events. We are convinced that our consortium's synergy of scientific expertise and technical sophistication will provide a future-proof answer to the specific protection goals.