Insights from a long-term monitoring system of a slow-moving landslide at Hofermühle, Lower Austria.

The occurrence of landslides poses a significant threat to communities and infrastructure worldwide. Detailed knowledge of the triggering factors and process mechanisms of this geomorphic hazard still remains challenging. To reduce landslide risks, negative societal impacts and to deepen our understanding of the preparatory and triggering factors for landslide initiation, long-term monitoring approaches can be helpful. However, long-term monitoring projects required to study slow-moving landslides with varying periods of activity are rare due to financial and/or project time constraints. Here, we present the results of a long-term monitoring system, that includes a variety of methods to monitor the surface and subsurface of a slow-moving landslide, at the Hofermühle, in Lower Austria.

The region of Lower Austria is heavily affected by landslides. Therefore, the present research focuses on a small, retrogressive, slow-moving (cm-dm/a) earth slide-earth flow system of ~0.15 km² at Konradsheim, Waidhofen/Ybbs in Lower Austria, which is representative of thousands of landslides in the region. It is located in a complex geological transition zone, of which the Flyschzone is known to be prone to shallow and deep landslides. It is characterized by high clay contents and the advanced weathering stage of the lithology. In addition, anthropogenic influences such as drainage mechanisms and land-use changes complicate the situation at the study site. Movements at the Hofermühle have been reported since the 1970s. In 2013, sliding processes increased in speed and magnitude, with heavy precipitation being the main trigger. As a result, monitoring systems were continuously established in 2014 and have been in operation since then. In this study, hydrometeorological data and remote sensing, such as UAV and TLS, combined with subsurface and geophysical data (e.g., inclinometers, TDR-probes, ERT) provide meaningful insights into the dynamics of slow-moving landslides.