Current development of mass movements in lowland river valleys at the site of old landslides - case study form Vistula Valley, Poland

Abstract:

Landslides in Polish lowlands are found mostly in the escarpment zone of river valleys. In this geomorphological position, landslides were investigated in the middle of the Lower Vistula Valley – major polish river valley (53°14’N 18°14E). In the zone between Fordon and Kozielec landslides develop within Quaternary tills, sands and clays with glacitectonic deformation. Determination of contemporary activity of landslides in the escarpment zone is based on field work, such as a detailed inventory and documentation of the landslide forms, geotechnical and geological drillings, geodesic measurements, and analysis of aerial photographs. Shearing slides, often in the multiple rotational form, are the most common type of landslides. Most landslides are developed within the main scarps of old landslides. The size of contemporary landslides ranges from 500m² to 70000m². While the old, inactive landslides’ area varied between 120000m² to 300000m². Contemporary active forms represents 58%, regularly active for 17%, and inactive for 25% of the identified landslides. Depending on geomorphological zones, landslides cover up to 30% of the area of the slopes. Currently, in the study area precipitation and geological settings are the most important factor of landslide activation. This study was supported by the Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association and the research project no. N N306 0860 37 Polish Ministry of Science and Higher Education.