Long-term reconstruction of a large-scale landslide of a LIA lateral moraine in the Upper Kaunertal in Tyrol, Austria

Since the end of the Little Ice Age around 1850, global warming has led to rapid landscape changes, especially in high mountain areas. The ongoing glacier melt leads to an expansion of the LIA glacier forefields, so-called proglacial areas. The exposed lateral moraines often show increased sediment activity over decades and centuries, which is generally described as the paraglacial adjustment process. Slope instabilities are caused, for example, by the loss of the support from the melting glaciers, which can lead to large landslides and thus heavy deformations. In order to understand corresponding geomorphological processes, it is important that surface changes can be reconstructed and analysed in high spatial and temporal resolution. However, aerial photographs of the European Alps, which are well suited for observing proglacial areas, only extend to the middle of the 20th century, thus resulting in a temporal limitation.

Therefore, in this work we show a nearly 100-year quantitative monitoring of a large-scale deformation of a LIA lateral moraine in the glacier forefield of the Gepatschferner in the upper Kaunertal (Tyrol, Austria). We achieve this long-term (1922 to 2021) observation by combining different topographic data sets based on different remote sensing methods and techniques. The reconstructed earth surfaces are based on airborne LiDAR data (2006 to 2021) and photogrammetric DEMs (1953 to 2003) as well as a historical stereophotogrammetric map from 1922, which was also generated into a DEM. In total, eight DEMs were generated and corresponding DoDs calculated.

Different landslides within the first three epochs (1922 to 1953, 1953 to 1971 and 1971 to 1983) could be determined on the slope, which can be directly linked to the corresponding glacier melt. Even after the landslide processes (from 1983 onwards), continuous geomorphological activity could be observed until today (2021), whereby the total volume of net erosion of all epochs (from 1922 to 2021) added up to approx. 486,000 m³.