Monitoring of Rainfall Induced Landslides in Relation to Weather Conditions at Selected Locations in Polish Carpathians

Abstract

Rainfall water plays the basic role in mass movements activation in Polish Carpathians. Its infiltration has impact on seepage processes and changes of pore water pressures and thus affect the strength parameters of soils inside the slopes. Investigated colluviums built from flysch layers of weathered claystones and sandstones were difficult for in situ and laboratory tests. High quality core drillings, sampling, geophysical investigations, laboratory tests and instrumentation provided data for slope stability analysis. Monitoring played a special role in the project. Recognition of weather and groundwater conditions influence on movement’s activation was realized using inclinometer, piezometer, pore pressure and meteorological monitoring instrumentation. In 2010 new automatic, on-line early warning system was installed at Szymbark landslide near the city of Gorlice. Measurements in standard system allowed observation of landslide behavior after intensive precipitations in Polish Carpathians in June 2006 and May-June 2010. Measurements in on-line system started during intensive rainfalls and flood in June 2010. The results confirm the relationship between rainfalls, changes of pore pressure values and displacements activation. The highest rainfalls were followed by intense increase and decrease of pore pressures. The movements usually occurred after precipitations of 200–250 mm, lasted one or a few days depending on the initial saturation conditions. These processes caused reactivation of existing landslides or forming a new ones. Research proved that monitoring of rainfalls, pore pressures and displacements could help in recognition of movement activation triggers for selected landslides. It may be also useful in landslide prediction, remediation works and early warning.