Environmental change let it be induced either by climatic or anthropogenic factors has had a key ... more Environmental change let it be induced either by climatic or anthropogenic factors has had a key role in determining the rate of aeolian sediment transfer, on the highly sensitive landscape of the Danube-Tisza Interfluve, Hungary. The study area is located on a former alluvial fan of the Danube, abandoned by the river in the Late Pleistocene, and then reshaped by aeolian activity. The resultant dune fields were time to time reactivated during the Holocene and historical times. As this part of the Carpathian Basin is often stricken by droughts, anthropogenic factors, such as forest clearances and/or overgrazing could easily lead to the disturbance of morphological stability. These effects acted on a local level, however in certain historical periods they supposedly were more extended and general. An era of this type was the time of Turkish occupation (16th-17th c.) and the following two centuries. During the Turkish rule the territory was cleared of forests and became deserted. Following the slow recolonisation by people and vegetation the land was mainly used for grazing. There are numerous historical reports on repeated sand storms and wind erosional events. However, we have no concept on the true amount of sediment reworked these times and the rate of geomorphic change. The major aim of the present study is therefore to quantify the possible amount of sediment transfer in a wind blown depression-hummock system on the central part of the Danube-Tisza Interfluve during the past 500 years. The determination of dune formation and migration rate provides further insight into the active morphological processes of the region, and also highlights the possible geomorphic responses to environmental changes (mostly climatic) currently affecting the central part of the Carpathian Basin. Seven drillings were made on the chosen hummock and the adjacent blow out to set up the chronological framework of dune formation by the means of luminescence dating (OSL). The relatively high resolution of dates in this "young" environment was achieved by IRSL feldspar dating. The verification of luminescence ages and the reconstruction of past environment and environmental change was made on the basis of historical reports, military survey maps and municipal maps from the 17th, 18th and 19th centuries. The assessment of transferred sediment volumes and visualisation of dune evolution was carried out by digital terrain modelling based on high resolution on site measurements. According to our preliminary results the 8-9 m high hummock was primarily formed around 400 years ago, due to the clearance and abandonment of the area. Subsequent events were less intensive, resulting only approx 1-2 m vertical accumulation. Horizontal development (migration) seems to be much less intensive. In all 75 000 m3 of material was moved and reworked in the past few centuries in the investigated morphological system.
Palaeohydrological record coupled with geochronology can serve as key tools for reconstructing pa... more Palaeohydrological record coupled with geochronology can serve as key tools for reconstructing past environmental and climatic change. The alluvial plains of the Carpathian Basin are hosting numerous generations of paleochannels which developed in response to highly varying water and sediment discharges. Our investigations focused on the Lower Tisza Basin where palaeomenaders remained recognisable only in a relatively narrow N-S belt along the Tisza river. The width and wavelength of these channels significantly exceed contemporary values even if compared to that of the Danube. Two major channel generations were investigated: one located on a higher level of the floodplain, having larger but more blurred pointbars and main channel, and another in the level of the present floodplain, having smaller but much fresher forms. The primary aim of the research is create the chronological framework of fluvial activity in the region and to determine palaeodischarges, thus to evaluate the trend and magnitude of climatic change. On the other hand the rate of morphological evolution is also assessed, which provides a more detailed insight to the environment in which the meanders were developing. The age and development rate of meanders were determined by the means of luminescence dating (OSL). 16 drillings were made to sample pointbar and channel sediments of two megameanders. Fluvial stratigraphy and sedimentological correlations were set up by laser grainsize analyis. Discharges were calculated on the basis of plaeohydrological equations, however by estimating palaeo cross-sectional area and slope more reasonable results were received. In all more than 30 sediment samples were measured by OSL. In numerous cases both their polymineral fine grain and quartz coarse grain fractions were also dated in order to assess the adequacy of bleaching during deposition, and the applicability of the more abundant fine grain sediments for dating purposes. Luminescence measurements show that coarse grain minimum ages are in a relatively good coincidence with fine grain ages, thus both types of sediments can be applied for OSL in this meandering system. The formation of the more elevated, larger meander was dated to the Bölling-Alleröd Interstadial (12-14 ka). The smaller meander started to evolve approx. 10 ka ago, suggesting that incision and the development of the present floodplain level took place during the shift from the Younger Dryas to the more moderate Holocene climate. Based on calculations, channel forming discharges were around 10 000 and 5 000 m3/s, respectively. The rate of lateral accretion was also very different. The older meander developed at a rate of 1 m/y, while this value could be three four times higher in case of the younger one. This refers either to much higher energies or less stabilised boundaries acting within the fluvial system in the Early Holocene.
Page 1. 197 Morphometric change due to altered hydrological conditions in relation with human imp... more Page 1. 197 Morphometric change due to altered hydrological conditions in relation with human impact, River Hernád, Hungary Tímea Kiss, Viktória Blanka and György Sipos with 10 figures and 3 tables Summary. On the slightly ...
Environmental change let it be induced either by climatic or anthropogenic factors has had a key ... more Environmental change let it be induced either by climatic or anthropogenic factors has had a key role in determining the rate of aeolian sediment transfer, on the highly sensitive landscape of the Danube-Tisza Interfluve, Hungary. The study area is located on a former alluvial fan of the Danube, abandoned by the river in the Late Pleistocene, and then reshaped by aeolian activity. The resultant dune fields were time to time reactivated during the Holocene and historical times. As this part of the Carpathian Basin is often stricken by droughts, anthropogenic factors, such as forest clearances and/or overgrazing could easily lead to the disturbance of morphological stability. These effects acted on a local level, however in certain historical periods they supposedly were more extended and general. An era of this type was the time of Turkish occupation (16th-17th c.) and the following two centuries. During the Turkish rule the territory was cleared of forests and became deserted. Following the slow recolonisation by people and vegetation the land was mainly used for grazing. There are numerous historical reports on repeated sand storms and wind erosional events. However, we have no concept on the true amount of sediment reworked these times and the rate of geomorphic change. The major aim of the present study is therefore to quantify the possible amount of sediment transfer in a wind blown depression-hummock system on the central part of the Danube-Tisza Interfluve during the past 500 years. The determination of dune formation and migration rate provides further insight into the active morphological processes of the region, and also highlights the possible geomorphic responses to environmental changes (mostly climatic) currently affecting the central part of the Carpathian Basin. Seven drillings were made on the chosen hummock and the adjacent blow out to set up the chronological framework of dune formation by the means of luminescence dating (OSL). The relatively high resolution of dates in this "young" environment was achieved by IRSL feldspar dating. The verification of luminescence ages and the reconstruction of past environment and environmental change was made on the basis of historical reports, military survey maps and municipal maps from the 17th, 18th and 19th centuries. The assessment of transferred sediment volumes and visualisation of dune evolution was carried out by digital terrain modelling based on high resolution on site measurements. According to our preliminary results the 8-9 m high hummock was primarily formed around 400 years ago, due to the clearance and abandonment of the area. Subsequent events were less intensive, resulting only approx 1-2 m vertical accumulation. Horizontal development (migration) seems to be much less intensive. In all 75 000 m3 of material was moved and reworked in the past few centuries in the investigated morphological system.
Palaeohydrological record coupled with geochronology can serve as key tools for reconstructing pa... more Palaeohydrological record coupled with geochronology can serve as key tools for reconstructing past environmental and climatic change. The alluvial plains of the Carpathian Basin are hosting numerous generations of paleochannels which developed in response to highly varying water and sediment discharges. Our investigations focused on the Lower Tisza Basin where palaeomenaders remained recognisable only in a relatively narrow N-S belt along the Tisza river. The width and wavelength of these channels significantly exceed contemporary values even if compared to that of the Danube. Two major channel generations were investigated: one located on a higher level of the floodplain, having larger but more blurred pointbars and main channel, and another in the level of the present floodplain, having smaller but much fresher forms. The primary aim of the research is create the chronological framework of fluvial activity in the region and to determine palaeodischarges, thus to evaluate the trend and magnitude of climatic change. On the other hand the rate of morphological evolution is also assessed, which provides a more detailed insight to the environment in which the meanders were developing. The age and development rate of meanders were determined by the means of luminescence dating (OSL). 16 drillings were made to sample pointbar and channel sediments of two megameanders. Fluvial stratigraphy and sedimentological correlations were set up by laser grainsize analyis. Discharges were calculated on the basis of plaeohydrological equations, however by estimating palaeo cross-sectional area and slope more reasonable results were received. In all more than 30 sediment samples were measured by OSL. In numerous cases both their polymineral fine grain and quartz coarse grain fractions were also dated in order to assess the adequacy of bleaching during deposition, and the applicability of the more abundant fine grain sediments for dating purposes. Luminescence measurements show that coarse grain minimum ages are in a relatively good coincidence with fine grain ages, thus both types of sediments can be applied for OSL in this meandering system. The formation of the more elevated, larger meander was dated to the Bölling-Alleröd Interstadial (12-14 ka). The smaller meander started to evolve approx. 10 ka ago, suggesting that incision and the development of the present floodplain level took place during the shift from the Younger Dryas to the more moderate Holocene climate. Based on calculations, channel forming discharges were around 10 000 and 5 000 m3/s, respectively. The rate of lateral accretion was also very different. The older meander developed at a rate of 1 m/y, while this value could be three four times higher in case of the younger one. This refers either to much higher energies or less stabilised boundaries acting within the fluvial system in the Early Holocene.
Page 1. 197 Morphometric change due to altered hydrological conditions in relation with human imp... more Page 1. 197 Morphometric change due to altered hydrological conditions in relation with human impact, River Hernád, Hungary Tímea Kiss, Viktória Blanka and György Sipos with 10 figures and 3 tables Summary. On the slightly ...
Uploads