Václav STACKE¹ & Petr TÁBOŘÍK^2
1Centre of Biology, Geoscience and Environmental Education, University of West Bohemia; Klatovská 51, Plzeň, Czech Republic, e-mail: vaclav@stacke.cz
²Institute of Hydrogeology, Engineering Geology and Applied Geophysics, Charles University in Prague; Albertov 6, Praha, e-mail: petr.taborik@post.cz

INTERACTION OF THE HILLSLOPES AND VALLEY BOTTOMS ON THE NW SLOPE OF THE LYSÁ HORA MT., THE HIGHEST PEAK OF THE WESTERN BESKIDS

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To reveal the slope-channel interaction in the highest parts of the Western Beskids, we studied the valley floor, colluvial accumulations and slope deformations in the Satina River valley (Outer Western Carpathians, Czech Republic). GNSS geomorphological mapping, geophysical sounding and detailed lithological analyses (grain-size, fabric, clast orientation and particle shape) of the valley infill enabled the presumable reconstruction of the processes that formed the valley. In the uppermost part of the valley the gradual change from the U-shaped to the V-shaped valley is distinctive. The river channel is vertically cut in the middle part of the valley (ca 19 m into the sediments and further 3 m into the bedrock formed by thinly laminated claystones). Colluvial layers formed by multigenerational debris flows with fluvial intercalations form the sedimentary infill in this stretch. The method of electrical resistivity tomography has confirmed deep-seated disintegration of the Lukšinec ridge and the occurrence of several generations of rockslides and rather shallow debris slides on the slopes above the studied site. Accumulations of the landslides are considered to be the source area of a large volume of colluvial sediments in the Satina river catchment. The alternations of layers of different genesis indicate high dynamics of the landscape development in the area. Particular debris flow events were separated by periods of prevailing fluvial processes. A part of the landslide area had been saturated and its consequent reactivation led to the formation of the new debris slide with shallow planar slip plane after the 1997 extreme rainfall event. The canyon-like valley incised into the sandstone flysch rocks is preserved in the lower parts of the catchment. The studied part of the catchment is thus characterized by the geomorphological processes pattern change observed in the formation of a large accumulation in transport limited conditions of a colder period of the Pleistocene (forest-free area) and intensive vertical cutting in supply limited conditions of the Holocene.