In the recentyears intensified landslidingwas observed in the surroundings and in the town of Koronowo near Bydgoszcz. (Krajeñskie Lake District). The gently undulated moraine upland, a wide valley of the Brda river, its relatively steep valleysides and incised valleys of tributaries are morphologicfeatures related to modeling by North Polish Glaciation. Quaternary tills alternated with fluvioglacial sands and gravels are underalined by Miocene clay and mud with brown coal intercalations. Due to such morphologic and geologic setting the study area isprone to slope instability. Failure apt soil massifs were assigned to 4 groups. Out of 32 identified landslides, 9 were selected for detailed examination. To register a nature and rate of failures a complex monitoring system was installed on slopes where the selected landslides resulted in severe damages to municipal infrastructure. The system was facilitated with inclinometers andpiezometers, supported by a network of GPS-RTK geodetic benchmarks as well as with a recording weather station. The performed examination revealed that the most unfavourable arrangement of the layers is, when under a non-cohesive soil (e.g. sand, gravel) lies a cohesive impermeable layer (e.g. clay, loam). The landslides are rather shallow ones (except 2 incidents) with slow rate of displacement of an order offew mm/year. The landslide triggeringfactor is water originatingfrom precipitation and snow melting. Influence of water was especially significant in early Spring 2011, due to the combined effect ofsnow melting and infiltration of thawing water originating from the former, exceptionally high rainfalls. The influence of hydrologic conditions on slope deformations is complex. There is a significant timelag between a movement initiation and unfavourable hydrometeorological conditions. That is exemplified with the landslide that was initiated in February-March 2011 in consequence of atmospheric conditions of November-December 2010. The obtained results formed the background for inventing engineering treatment measures aiming at current remedial stabilization of slopes and mitigation ofpossible landsliding in the future.
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