The aim of the study was to gain knowledge about changes in the nival conditions prevailing in the lower part of the Babia Góra massif in the winter, during the period from 1960/61 to 2014/15.
The performed analyses concerned the daily snow cover thickness in the winter seasons of the years 1960/61–2014/15, and were based on data recorded by a meteorological station established by the Institute of Meteorology and Water Management – National Research Institute (IMGW-PIB) in Zawoja (697 m altitude). The study was focused on the period from the first to the last day of the appearance of the snow cover in the season.
Based on long-term measurements carried out in in Zawoja, it was found that the average length of the occurrence of snow cover with the thickness of ≥ 1 cm was 104 days, which showed variability in individual seasons that ranged from 47 days in 2013/14 to 145 days in 1993/94. It was noted that the period of snow cover occurrence was shortened – from 118 days in the decade 1960/61–1969/70 to 96 days in the recent decade (2000/01–2009/10). The potential duration of snow cover was on average 157 days. The snowiest months were February and January, when snow cover occurred for 81% and 75% of all the observation days, respectively. The largest thickness of snow cover was recorded during these two months, with the maximum of 178 cm (January 30, 1976). In contrast, snow cover was not observed in July, August and September. The studied multi-year period was characterised by high variability of the winter snowiness index: from 1.61 in 2013/14 to 8.00 in 1962/63.
In the period 1960/61–2014/15, in Zawoja, there was observed the distinct periodicity (16–19 years) with regard to the number of days with snow cover, the average and total snow cover and the winter snowiness.
Mountain streams are subjected to the continuous reshaping of their river beds during floods, with the greatest changes occurring during extreme floods caused by sudden and heavy rainfall. River bed transformations during these flash floods are more severe in forested areas, where wooden logs carried by swollen streams are more likely to be deposited on the ground, which in turn leads to the greater accumulation of other transported material and debris.
The study was conducted in the Rybny Potok catchment area (Babia Góra National Park). An extreme flash flood occurred on 15–16 May 2014 because of heavy rainfall, which, on 15 May amounted to 138 mm. The total amount of precipitation in the catchment area was 216.5 mm in three days. This resulted in sudden and full streams in spate, contributing to significant geomorphological transformations reaching all the way to the bottom of the river beds. During the flash flood, already established river beds and streams increased in size and many new river courses were formed.
Michał Zatorski, Krzysztof Buczek and Paweł Franczak
The landslide in Huta Polańska (Beskid Niski/Lower Beskids) is an example of a particular lake geoecosystem. The largest inter-colluvial depression forms a lake basin constantly filled with water, with a natural outflow in the form of a watercourse. Three drainless sink-holes constituting places of periodical accumulation of water and organic-mineral sediments were localized within the landslide. The direction of the landslide movement and its wedge-like shape are determined primarily by the fault surface located in its south-western part. It also forces the linear course of the streams and the cascade location of depressions between colluvial ramparts, seasonally or permanently filled with water. The inventory of minor tectonic structures and the morphotectonic analysis indicate tectonic conditions of this landslide lake geoecosystem. The structures located within the fault surfaces are indicative of shear stresses and their orientation determines the direction of rock movement (Zuchiewicz, 1997a; Szczęsny, 2003). The morphological analysis and correlation of landslide forms indicate the combined rotational-translational motion. It was ended by mud and debris flow which divided the valley longitudinal axis and damming the waters of the Hucianka stream. The result is a landslide dam lake, whose effects are visible within the floodplain above the former landslide dam. In order to formulate the final conclusions regarding the morphotectonic analysis and the slope transformation phases, laser scanning photos were also used.