Trudności w wyznaczaniu osuwisk na obszarach historycznych i zurbanizowanych na przykładzie Twierdzy Przemyśl

Difficulties in determining landslides in historical and urbanized areas – a case study of the Przemyśl Fortress. A b s t r a c t.The Przemyoel Fortress is a huge complex of defensive objects from the turn of the 19 th and 20 th centuries. Various types of objects, ruins and remains of the fortress and signs of fights have been preserved to different extents in the area to this day. They constitute a huge problem when determining landslides. The greatest difficulties are caused by vegetation-covered ruins of forts, trenches, remnants of ramparts and defense ditches, and signs of fights preserved in places. Such residues can be interpreted as a landslide or a part of it, especially if they occur in a neighbourhood or inside a landslide. The problem then arises of clearly identifying the boundaries of the landslide and the correct identification of its internal forms, e.g. a devastated trench around the fort can be marked as a landslide. Similar difficulties are provided by numerous inactive quarries, excavations, clay pits, e.g. a closed limestone open-pit mine from the 19 th century, located in Kruhel Wielki. Elements of the old mine are deceptively reminiscent of intra-field forms and they are difficult to separate from the real colluvial forms of the neighbouring landslide. Difficulties in determining landslides arise not only from the history of this region and its geological structure, but also from the degree of urbanization of the area. Strong anthropopression blurs the natural morphology of the slopes, and the limited availability of the area makes cartographic work difficult. It is difficult to distinguish between natural and artificial forms in such areas. Good examples are landslides on the ski slope, on the municipal cemetery, in the castle park and in the area of military areas, housing estates and allotments.