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1
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Zmienność kształtu wydm gwiaździstych w obszarach o bimodalnym reżimie wiatru

100%
Biejat K.
Prace i Studia Geograficzne
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2012
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tom 49
Contemporary morphological changes of star dunes are observed mainly in certain parts of these dunes. They occur as lateral migration of crestlines of dune arms and modifications of inclination of their slopes. The aim of the research was to determine annual variability of shapes of compound and complex star dunes in bimodal wind regime. Precise measurements of 5 star dunes were performed with use of GPS RTK in March, 2011, and March, 2012, on Erg Chebbi (Morocco). Based on these measurements, 3D models of the dunes were created, which in turn, allowed for calculation of annual magnitude and direction of crestlines migration of star dune main arms. The results show that the resultant drift direction was in accordance with long-term regime of active wind in the study area. Both, the resultant drift direction and its magnitude were similar in all studied dunes. Variability of star dune shapes occurred to be independent from their stage of development (size of a dune) or its type. The most important feature determining morphodynamics of the star dune arms are: i) the angle between the arms and the active wind, and ii) slope inclination of the arms.
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Kształt barchanów jako wskaźnik reżimu wiatru na przykładzie Sahary Zachodniej Maroko

63%
Dluzewski M., Biejat K.
Prace i Studia Geograficzne
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2012
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tom 49
Barchans are characterized by a symmetric shape independently of their stage of development and the axis of symmetry parallels to the dominant wind direction. However, shape of the dunes can be modified by several factors, among which most important are: change of wind regime, dune collisions or interaction of closely spaced dunes, ground surface relief, asymmetric sediment supply. The aim of the study was to analyze the impact of short-term (diurnal) and long-term (seasonal) changes in wind direction and velocity on shape of barchan dunes. The study was conducted in southern Moroccan area of Western Sahara, between Tarfaya and Laâyoune. This area is characterised by significant variability of active wind (RDP/DP=0,66) which is unfavourable for barchans development. Measurements were conducted in two spring seasons of 2011 and 2012 and two autumn seasons of 2007 and 2011. 52 isolated barchans were selected for detailed studies. Based on GPS-RTK measurements, precise 3D models of the landforms were obtained allowing the detailed analysis of dune shapes. Changes of basie morphological parameters were analyzed as well as shape changes occurring the windward slope and within dunes horns. The shapes of the barchans were correlated with the short-term and the long-term wind regime. It was found that basic morphological parameters are not good indicators of wind variability, with the exception of barchan horns lengths which change according to the seasonal wind regime. Short-term wind regime changes are well registered by: i) "collars" developing along the dune crestlines, ii) "tongues" developing at the ends of dune horns and iii) location of the dune apex. On the other hand, beaded horns testify for very strong wind. I was found, that mentioned features develop and undergo modification during first days or even hours of changed wind regime. The analyzes of barchan shapes, performed in different seasons, proved that even a several-month long period of highly diversified wind regime does not change basie shape of the barchans. Therefore, it can be inferred that barchans development does not depend exclusively on wind regime.
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Źródło wilgoci w barchanach Sahary Zachodniej

51%
Dluzewski M., Zmudzka E., Woronko D., Biejat K.
Prace i Studia Geograficzne
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2012
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tom 49
The aim of the study was to determine the impact of climatic and meteorological conditions on aeolian sand transport within barchans. The study area was located at Western Sahara, around the towns of Tarfaya and Laâyoune. Particular attention was paid to the factors that increase the moisture content of the surface and subsurface layers of sand dunes. It could be one of the important factors to have an influence on threshold wind velocity. Western Sahara dune fields are situated in the zone of the dominant wind direction from the northern sector, which determines the barchan dunes shape and orientation, as well as the supply of moisture from the Atlantic Ocean. The results of investigations confirm that dunes receive quite a lot of moisture from rainfall and such phenomena as fog as well. Studies have confirmed that the water supply from the fog is comparable to, or even exceeds the amount of water from rainfall in the area. Wetted surface layer reduces the transport of aeolian material, even in case of a wind speed greater than 4-5 ms⁻¹. The presence of fog and dew does not affect the moisture of the deeper sand layers, which occurs after rainfall. Analysis of aeolian sand transport within the barchan dunes in the areas such a Western Sahara, should not be therefore limited to the measurement of wind speed and its direction. It must include the investigations on other meteorological elements, especially air temperature and humidity conditions, responsible for the amount of atmospheric deposits on the dune surface.
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Formy i procesy fluwialne w obszarze Morza Egejskiego na przykładzie Ikarii (Grecja)

51%
Krzemien K., Biejat K., Dluzewski M., Tsermegas I.
Prace i Studia Geograficzne
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2012
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tom 49
Main aims of the research were: i) to assess the degree of development of fluvial landforms on Aegean Islands and ii) to determine the influence of fluvial processes on modification of islands relief. Field studies were conducted on the Ikaria Island, with highly diversified geology and relief, typical of mountainous islands of the Aegean Sea. The island is heavily dissected by deeply incised valleys and gorges with very steep slopes. The valleys on Ikaria Island vary in size, direction, geological setting and maturity. In the four small catchments located in the northern part of the Ikaria Island four types of valleys (from 1st to 4th order, according to Strahler) were studies in detail. Uppermost parts of these valleys (1st order valleys) have slightly concave cross-sections covered with regolith without developed channels. Such forms gradually evolve into 2nd order valleys with seasonal river channels, and further downstream, into well developed deep river valleys. Ravines with channels incised into solid rock are characteristic of the 3rd order valleys. The 4th order valleys are well developed, deeply incised gorges with wide channels sometimes accompanied by river terraces. Channels of small streams, rivers and field tracks in the mountains are subject to differentiated modelling by running water. In islands of the Aegean Sea, intensity of this modelling is diversified and rather small. It depends mostly on rainfall intensity, bedrock resistance to erosion, slope inclination and aspect. Catastrophic hydrometeorological events such as one which occurred in Ikaria in October, 2010, are responsible for rapid modification of whole valley floors and modification of river channels at lower river runs, within deltas and alluvial fans.
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Degradacja tarasów rolnych w warunkach śródziemnomorskich - wybrane przykłady z Wysp Egejskich (Grecja)

51%
Tsermegas I., Dluzewski M., Biejat K., Szynkiewicz A.
Prace i Studia Geograficzne
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2012
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tom 49
The main aim of the study was to estimate the influence of relief, lithology, climatic conditions, methods of wall construction and actual agricultural practice on the degradation of traditional agricultural terraces on the example of three Greek islands. We selected 7 research plots situated in 5 different geological settings - 3 on the Ikaria island, 2 on Thira, and 2 near Plati village on the SW edge of Lassithi Plateau on the Crete island. We used the following methods: GPS RTK measurements, mapping of erosion features, georadar profliling, infiltration rate measurements and interviews with farmers. We find that lithology is the most important factor controlling terraces degradation, but only in relation to methods of cultivation. Traditional agricultural practice helps terraces to remain stable, because cultivated field increases the possibility of infiltration and limits surface runoff. Heavy rainfalls do not affecting terraces stability due to high ground infiltration rate or high permeability of dry-stone walls. Terraces are more stable if they are concordant to the natural slope profile. On the terraced slope erosion is lower than on non-terraced slope. This is true only on the slope with very limited vegetation cover.
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Wpływ morfodynamiki koryt rzecznych na działalność człowieka w atlasie wysokim na przykładzie doliny Górnego Dades - Maroko

45%
Sobczak K., Biejat K., Dluzewski M., Gierszewski P., Michno A.
Prace i Studia Geograficzne
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2012
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tom 49
The paper describes the results of research in the Upper Dades Valley in the High Atlas Mountains in Morocco. The purpose of the research was to identify the impact of river channels changes, fluvial accumulation nad erosion on human activity. Fieldwork and maps were used to characterize the structure of the Dades river channel and the intensity of present-day fluvial processes. Research data show that the Upper Dades Valley is shaped primarily by short but frequent and intense hydrometeorological events. The structure of the Dades river channel indicates a complex functionality. Tributary episodic riviers and gorges sections supply most of the weathering material. Narrow sections of Dades channel serve for material as transfer zones, while deposition occurs across broader areas. Research has shown that extreme fluvial processes occurring in semi-arid mountains result in fast river chanels changes and accelerated deposition of weathering material across valley floors, which usually leads to limits on the development of agriculture in such areas.
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