Identification of the Causes of a Landslide in Koronowo (Polish Lowlands)

Abstract

The paper discusses difficulties of identifying the causes of a landslide. These difficulties are illustrated in the example of a catastrophic landslide on the embankment of the western bank of the Brda River, which affected a bridge abutment of a disused narrow-gauge railway line from Bydgoszcz to Koronowo (Polish Lowlands). The railway was closed in 1992, and after the removal of the track, the bridge served as a pedestrian overpass. The landslide occurred in February 2011. Investigations revealed that the first signs of the landslide were cracks and subsidence that appeared at the embankment crest. Then, an initially slow movement accelerated suddenly, resulting in an over 45 m total displacement of the soil mass. The primary passive cause of the landslide movement resulted from the geology of the mass (loose soils underlain by cohesive soils) and from the steep inclination of the embankment surface. Active causes, however, are often ambiguous. In this case, no significant apparent phenomena which could trigger the movement occurred in the days preceding its initiation. Therefore, a detailed analysis of atmospheric conditions was carried out to identify and explain the causes. It was proved that the fundamental triggering cause of the landslide was a combination of rainfall, snowfall, snow-melting and air temperature. Moreover, an important cause was a faulty construction of a ditch with a sewage pipe on the crest of the embankment.

Mass-Movement Causes and Landslide Susceptibility in River Valleys of Lowland Areas: A Case Study in the Central Radunia Valley, Northern Poland

“…However, the methods used in landslide susceptibility allow for the assessment of the role of anthropogenic factors to a limited extent [20], which is related to the difficulties caused by including factors that rapidly change in time and space in two-dimensional GIS analysis. Field surveys and stability analysis, as well as groundwater level and inclinometric monitoring, are carried out on individual landslides and, therefore, allow for the determination, to a greater extent, of the influence of anthropogenic actions on the activation and progression of landslides [21][22][23][24][25]. Such thorough research makes it possible to compare and supplement the conclusions resulting from susceptibility analyses.…”