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Potential landslide hazard in a zone of stabilised earthen embankments illustrated by Wysoka Gorka in Chełm

100%

Demczuk P. , Zydron T. , Dobrowolski R. , Dzieńkowski T. , Słuch M.

nr 1

Plant cover is an important element in the management of earthen structures and slopes improving their aesthetic values and limiting their vulnerability to denudation processes. With regard to landslide hazards, an important aspect in the presence of plants is the effect of their root systems on the shear strength of the substrate and, consequently, on slope stability. The aim of the study was to determine the impact of the tree cover at the Wysoka Górka archaeological site on the stability of the earthen embankment on Góra Katedralna in Chełm (Lublin Province). These architectural elements originate from the times of Chełm’s glory in the first half of the 13th century, when it became the capital of Halych-Volhynia Duchy and a residence of Prince Danylo Romanovych (Isaiecić 1999). The research involved identification of the geological structure of the embankment (surveying, measurement of the filtration coefficient) and laboratory determination of the geotechnical parameters of the soil (particle size distribution and soil compressive strength measured in a triaxial compression apparatus). In the next stage of the study, stability was calculated with limit equilibrium methods in the GeoStudio program. Standard calculations of the embankment stability were performed and the stability coefficient for the slope devoid of vegetation and the tree-covered slope were compared assuming zero suction pressure. The shear strength parameters of soil reinforced by plant roots were adopted following the recommendations specified by Hubble et al. (2013). The authors performed a probabilistic analysis in order to determine the probability of critical values of the safety factor (<1.0) and comparative stability calculations, taking into account hydrological effects for the tree-covered and tree-devoid (after felling the trees) embankments (Sonnenberg et al. 2010, Simon and Collison 2002). The results of the stability calculations demonstrated that the presence of viable plant roots in the substrate increased slope stability, and the presence of tree stands at the bottom of the embankment appeared to be more favourable. Modelling the slope stability with consideration of the effect of atmospheric factors has shown that the presence of woody vegetation contributed to increased water infiltration into the embankment, resulting in reduction of suction pressure. In turn, tree felling led to reduction in suction pressure due to inhibition of evapotranspiration.

Interdisciplinary studies of spring mire deposits from Radzików (South Podlasie Lowland, east Poland) and their significance for palaeoenvironmental reconstructions

72%

Dobrowolski R. , Pidek I. A. , Alexandrowicz W. P. , Hałas S. , Pazdur A. , Piotrowska N. , Buczek A. , Urban D. , Melke J.

tom Vol. 39, no. 1

10-29

The paper presents the results of interdisciplinary (multi-proxy) palaeoenvironmental studies of peat – calcareous tufa depositional sequences of spring mire from Radzików site (east Poland). Analyses of three biotic proxies (plant macrofossils, pollen, molluscs) were supplemented with sedi-mentological, geochemical, oxygen and carbon stable isotopes analyses and radiocarbon dating and used for reconstruction of environmental changes in Late Glacial and Holocene. The obtained results enable us to (1) reconstruct main phases of mire development and (2) determine environmental fac-tors influencing changes of water supply. The object started to develop in Allerød. The Late Glacial and Early Holocene deposit sequence is relatively thick (about 1.0 m), with good palaeoecological record. The boundary between Younger Dryas and Preboreal is especially well confirmed by palynological and malacological analyses as well as radiocarbon dating. The Mesoholocene deposits are considerably worse preserved. Mire develop-ment was evaluated in terms of general mire ecology.