The upper Isar between Mittenwald and Sylvenstein reservoir is Germany’s last major alpine wild river landscape, making it a conservation highlight. Since the establishment of the Walchensee power plant in 1924, the natural upper course of the Isar has been altered by diverting a large portion of the Isar’s water to the Walchensee. Nevertheless, the upper Isar remains a near-natural habitat with various rare or endangered species.
The natural dynamics of the landscape are evident through the free movement of water within the wide riverbed, fluctuations in water levels, and the constant formation of gravel banks and islands, especially after flood events. The presence of willows is also characteristic of the upper Isar valley. The area is home to some characteristic species dependent on the river’s dynamics, such as the German tamarisk and the spotted grasshopper. Because they are also breeding grounds for rare birds, access to some gravel banks is prohibited during the breeding season.
The Research Focus
The primary goal is to understand the river’s behavior, sediment transport, and the impact of human activities on this unique ecosystem with its willow and bush-covered floodplains.
To gather aerial imagery and generate high-resolution 3D maps, Unoccupied Aerial Vehicles (UAVs) equipped with cameras are flown over the Isar environment, capturing images that are processed to create detailed orthophotos and 3D models of the topography. This method is beneficial for covering large areas quickly and – once repeated – identifying changes in the river’s course and floodplain vegetation.
“We are interested in how sediment is transported here by the river. Naturally, but also when discharge events are controlled a bit upstream. We are using UAV photogrammetry, and later, we will reconstruct a precise 3D model from the drone imagery. And, if we come back here multiple times, in fall and next year again, we can quantify very accurately how the sediment changes”, explains Anders.
The researchers also use a Global Navigation Satellite System (GNSS) to obtain precise location data. GNSS is used to map the river’s course and georeference the digital landscape over time to monitor changes. This technology provides high-accuracy positioning, essential for tracking the river’s shifting banks and sediment deposits.
To create a detailed 3D model of the terrain, Terrestrial Laser Scanning (TLS) captures the topography of the riverbed and surrounding areas with millimeter precision. These 3D models help analyze erosion patterns, vegetation growth, deadwood detection and quantification, and the overall geomorphology of the floodplain.
“This is the start of what hopefully becomes a longer-term monitoring project where we can better understand how this natural river environment and the riverbank dynamics change over time”, said Anders.
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Professorship of Remote Sensing Applications
Professorship of Big Geospatial Data Management
Degree Program Geodesy and Geoinformation B.Sc.