Elżbieta Gorczyca

Beaver ponds' impact on fluvial processes (Beskid Niski Mts., SE Poland).

Beaver (Castor sp.) can change the riverine environment through dam-building and other activities. The European beaver (Castor fiber) was extirpated in Poland by the nineteenth century, but populations are again present as a result of reintroductions that began in 1974. The goal of this paper is to assess the impact of beaver activity on montane fluvial system development by identifying and analysing changes in channel and valley morphology following expansion of beaver into a 7.5 km-long headwater reach of the upper Wisłoka River in southeast Poland. We document the distribution of beaver in the reach, the change in river profile, sedimentation type and storage in beaver ponds, and assess how beaver dams and ponds have altered channel and valley bottom morphology. The upper Wisłoka River fluvial system underwent a series of anthropogenic disturbances during the last few centuries. The rapid spread of C. fiber in the upper Wisłoka River valley was promoted by the valleys morphology, including a low-gradient channel and silty-sand deposits in the valley bottom. At the time of our survey (2011), beaver ponds occupied 17% of the length of the study reach channel. Two types of beaver dams were noted: in-channel dams and valley-wide dams. The primary effect of dams, investigated in an intensively studied 300-m long subreach (Radocyna Pond), was a change in the longitudinal profile from smooth to stepped, a local reduction of the water surface slope, and an increase in the variability of both the thalweg profile and surface water depths. We estimate the current rate of sedimentation in beaver ponds to be about 14 cm per year. A three-stage scheme of fluvial processes in the longitudinal and transverse profile of the river channel is proposed. C. fiber reintroduction may be considered as another important stage of the upper Wisłoka fluvial system development.

Channel Changes due to Extreme Rainfalls in the Polish Carpathians

This chapter describes a role of extreme rainfall events in the development and transformation of channels in the Polish Carpathians. An analysis was based on the example of four selected events, which occurred in different parts of Polish Carpathians (Western Tatra, Bieszczady, and Beskid Niski Mountains) during the period 2003–2010. The findings underline that changes of the largest extent follow short and heavy rainfalls. Furthermore, their geomorphic impacts are the most significant in small watersheds. The research showed that the largest transformations of mountain rivers occur in the main channel, while the floodplain is only locally altered. The regularities identified in the study areas are relevant for mountain river channels in forested terrains, where a large supply of woody debris, for example, stems and branches, is ensured.

Landslide Hazards in the Polish Flysch Carpathians: Example of Łososina Dolna Commune

Lithology and tectonics (jointing, faulting) combined with relative relief and steep slopes induce slope failures in the Polish Flysch Carpathians. Therefore, landslides are frequent within inhabited areas of the Polish Carpathians and a major problem for local communes. This chapter presents a case study from a rural commune, which is located on the borderline between the Beskid Wyspowy Mountains and the Carpathian Foothills. The local geology makes that area extremely susceptible to landslides. A recent episode of landslide reactivation occurred in May and June of 2010 there, as a result of the clustering of continuous and heavy rainfalls, which appear to be the most important factor capable of triggering diverse types of mass movement. The analysis was based on the fieldwork conducted in 2010–2011 in the Łososina Dolna Commune and the research methods established by Polish National Geological Institute for the SOPO Landslide Protection Program. A total of 572 landslides were identified and documented in the study area, which occupies 17.2% of Łososina Dolna Commune. This contribution demonstrates that mass movements are significant processes which limit human activities.

Can beaver impact promote river renaturalization? : the example of the Raba River, southern Poland

The European beaver (Castor fiber) was reintroduced in the Polish Carpathians in the 1980s after a few centuries of absence. It gradually colonized suitable habitats in the Raba River valley and elsewhere. The question arises as to whether beaver activity can play a role in the local improvement of hydromorphological conditions and spontaneous renaturalization of the Raba River channel. Field surveys were performed in morphodynamically and structurally homogeneous reaches of the river. Traces of beaver activity were identified and used to estimate the studied beaver population. Local beaver impact on the studied river channel was also determined. The Raba channel is trained along about 80% of its length and considerably incised. Traces of beavers activity were found in 16 out of 31 river reaches, mainly in the upper and lower river course. The study showed that relatively flat channel gradient, small maximum bed-material grain size, and high channel sinuosity favour beaver presence. The largest number of beaver habitats was identified in river reaches strongly altered by man and characterized by a uniform channel structure. Beaver impact on channel structure varies depending on differences of the river channel features in upper and lower reaches of the Raba River channel. In upper reaches, the impact of beaver activity (mostly dams) is reflected in increased lateral erosion, while slower water current reduces the tendency for bed degradation. In lower reaches, beaver impact is mostly limited to bank fragmentation (slides and burrows). Lateral erosion, accumulation of material at the toe of riverbanks, and wood debris accumulation all produce a local impact on river channel width. These beaver-initiated processes mostly alter artificially homogenized river reaches. Beavers may actually play a substantial role in future renaturalization of both upper and lower reaches of the Raba River.

Precipitation as a factor triggering landslide activity in the Kamień massif (Beskid Niski Mts, Western Carpathians)

Abstract On the landslide slope in the Beskid Niski Mts (Western Carpathians) 48 silver firs were cored for dendrochronological samples. Tree-ring widths were measured for the upslope and downslope sides of each stem. Events of landslide activity were dated using the method of the eccentricity index. The tree-ring record of landsliding was compared with the occurrence of precipitation in the study area. The nature of the relation between precipitation and landsliding is complex. We have found a statistically significant correlation between landsliding and the number of days with 24-hour precipitation totals above 20 mm and high 3-, 5-, and 10-day precipitation totals during winter half-years. Thus landsliding in the Kamień massif is triggered mainly by high precipitation totals in the preceding winter period. No such relation was found for annual precipitation totals and different types of precipitation totals in the summer period. Single landsliding events related to high summer precipitation totals were found, but the correlation is not statistically significant. In addition some landsliding events are 1–2 years lagged after the occurrence of high long-term precipitation totals. It seems that the strongest landsliding events resulted from sequences of wet summer, wet winter and once again wet summer seasons directly following one another.

Effects of environmental changes and human impact on the functioning of mountain river channels, Carpathians, southern Poland

Abstract In the northern slope of the Carpathian Mountains and in their foreland, river and stream channels have been significantly transformed by human impact. These transformations result from changing land use in river basins and direct interference with river channels (alluvia extraction, engineering infrastructure, channel straightening). Anthropogenic impacts cause significant changes in the channel system patterns leading to increased impact of erosion. This mainly leads to the channelling of the fluvial system. This article reviews studies of structure and dynamics of Carpathian river channels conducted based on the methodology of collection of data on channel systems, developed in the Department of Geomorphology of the Institute of Geography and Spatial Management, Jagiellonian University.