Search

Published After
Published Before

Search Results

  • Accumulation studies at specific sampling areas of the active floodplain in the Upper-Tisza region
    14-22
    Views:
    170

    In this paper the rate of accumulation was studied along four VO floodplain cross sections of the UpperTisza region between 1974 and 2014. VO floodplain cross sections are based on a mapping base-point grid (established in 1890), and they are located a few kilometers from each other. Furthermore, the roughness changes of different surface types, crossed by the VO floodplain cross-sections, were also determined between 1965 and 2015. The accumulation studies were extended to include the accumulation rates of the cut off meanders located along and/or close to the VO cross-sections. The roughness values increased in all four floodplain VO cross-sections since 1965; in two of them it reached or approximated 100 %. The average accumulation along the VO cross-sections was between 28 and 47 cm (0.73–1.23 cm/year) during the 38-year period. However, its areal distribution showed large differences. The highest values (169–309 cm, i.e. 4.44–8.13 cm/year) were found at the lowest points of the cut off meanders and swales in every case. The accumulation rate of the examined three cut off meanders near the floodplain cross-sections (140 and 1570 meters from the river bed) was lower (0.84–2.5 cm/year), but the study period was significantly longer (154 and 161 years, respectively). Comparing the values of the two periods, it is obvious that the accumulation of the active floodplain accelerates, presumably due to the significant increase of surface roughness.

  • Studying floodplain roughness in an Upper Tisza study area
    85-90
    Views:
    179

    Floods slowing down due to the significant decrease of the gradient have considerable sediment accumulation capacity in the floodplain. The grade of accumulation is further increased if the width of the floodplain is not uniform as water flowing out of the narrow sections diverge and its speed is decreased. Surface roughness in a study area of 492 hectares in the Upper Tisza region was analysed based on CIR (color-infrared) orthophotos from 2007. An NDVI index layer was created first on which object-based image segmentation and threshold-based image classification were performed. The study area is dominated by land cover / land use types (grassland-shrubs, forest) with high roughness values. It was concluded that vegetation activity based analyses on their own are not enough for determining floodplain roughness.

  • Hydromorphological assessment of the lower Hungarian Drava section and its floodplain
    109-116
    Views:
    320

    The hydromorphological properties of rivers and their floodplains receive increased attention both in basic research and water management. A comparison of hydromorphological parameters before and after river regulation (involving floodplain drainage) provides important information for river management, particularly floodplain rehabilitation. The paper assesses a selected reach of the Drava River and the corresponding floodplain utilising two international approaches, the REFORM framework and the Italian Morphological Quality Index.

  • Land use changes and their effect on floodplain aggradation along the Middle-Tisza River, Hungary
    1-10
    Views:
    62

    Land-use changes and their effect on overbank sediment accumulation were investigated on the
    floodplain of Middle-Tisza River. Military survey maps (1783, 1860, 1883 and 1890) and aerial
    photos (1950, 1965, 1980 and 2000) were used to evaluate land-use changes and to calculate the
    vegetational roughness of the area. To determinate the rate of overbank sedimentation sediment
    samples were collected from a pit, the grain-size, content of organic matter, heavy metal content (Pb,
    Cu, Zn, Ni and Cd) and pH were measured. Until 1950 meadows and pastures were typical on the
    floodplain, gallery-forest was along the river, the oxbow-lake and the artificial levee. Notable landuse changes were detected in the second half of the 20th century, as the aerial photo taken in 1965
    shows extensive forestry in the area. These land-use changes affected the average vegetational
    roughness, as it has been doubled since the disappearance of grasslands. Land-use changes highly
    affect the aggradation, as the increased roughness decreases the flood velocity on the floodplain,
    causing accelerated aggradation. Using Pb marker horizons and grain-size changes the studied
    sediment profile was compared to dated profiles (Braun et al. 2003), thus, the sediment accumulation
    rate could be determined for the periods of 1858-1965 and 1965-2005. According to our
    measurements the accumulation rate was doubled since 1965, very likely in connection with the
    doubled vegetational roughness.

  • Morphological grouping of fossil floodplain forms in the northeastern part of the Pannonian plain
    21-33
    Views:
    26

    The Bereg Plain is located in the northeastern part of the Pannonian Plain, close to the Carpathian
    Mountains. Clarification of the evolution of its topography is essential for the development of the whole
    area. The former single alluvial cone has been fragmented, some parts of it subsiding and others rising.
    The displacements of the subsided parts of the area were dominated by erosion processes, as in the Bereg
    Plain. As a consequence, a significant part of the sand in the area has been degraded and only traces of it
    remain in the Bereg Plain. The existing sand patches have been identified and classified using DEM. In the
    area identified 10 floodplain islands not yet mentioned in the scientific literature. The investigation of
    the numerous islands – hitherto unknown and be-longing to different morphological types – enabled us a
    reconstruction of the surface development of the Bereg Plain that is more differentiated and precise than
    ever before. Based on their morphogenetic properties, these floodplain islands can be divided into three
    main types: (1) erosion islands, (2) point-bars, (3) coastal dunes. In the area, I could recognize no pattern
    or re-gularity in the position of the individual forms of any type. In many cases, the direction of the
    longitudinal trends is perpendicular to one another, which excludes their Aeolian origin. The sediment
    of the floodplain islands mainly consists of medium-, small- and fine-sized sand, but the settlement of
    loess-mantled and loess-like layers among the sandy sediment of certain forms can also be observed. The
    layer with 15 % lime content and 53–60 % loess fraction (0.05–0.01 mm) – found in the 110–50 cm high
    section of the erosion island called the Homok-tanya in Mátyus – can be considered a typical loess, based
    on the detailed parameters. Its formation in all probability took place at the same time and under similar
    conditions than that of the more than 2 m thick aeolian loess mantle found in the Nyírség area, some 10
    km west from there, which had accumulated before the Bölling period. In case of an erosion island 2.5
    km to the south and lying some 2 m lower, such a loess mantle cannot be found anymore, despite the fact
    that the sandy layers of the two sediment series are almost completely identical. The background of this
    phenomenon is the more active and frequent, mainly erosional fluvial processes – because of the lower
    position –, which eroded the loess mantle.
    The composition of the surface sediments is de-termined by the absolute altitude as well. The cover
    sediment of the lower-lying islands is identical to the finishing silt-clay deposits found at the alluvial
    parts of the Bereg Plain, whereas the surface of higher-lying forms that have not seen flood for ages, is
    covered by sand or loessy sand.

  • Heavy metal content of flood sediments and plants near the River Tisza
    120-131
    Views:
    46

    The River Tisza is Hungary’s especially important river. It is significant not only because of the
    source of energy and the value insured by water (hydraulical power, shipping route, stock of fish,
    aquatic environment etc.) but the active floodplain between levees as well. Ploughlands, orchards,
    pastures, forests and oxbow lakes can be found here. They play a significant role in the life of the
    people living near the river and depend considerably on the quality of the sediments settled by the
    river. Several sources of pollution can be found in the catchment area of the River Tisza and some of
    them significantly contribute to the pollution of the river and its active floodplain. In this paper we
    study the concentration of zinc, copper, nickel and cobalt in sediments settled in the active floodplain
    and the ratio of these metals taken up by plants. Furthermore, our aim was to study the vertical
    distribution of these elements by the examination of soil profiles. The metal content of the studied
    area does not exceed the critical contamination level, except in the case of nickel, and the ratio of
    metals taken up by plants does not endanger the living organisms. The vertical distribution of metals
    in the soil is heterogeneous, depending on the ratio of pollution coming from abroad and the quality
    of flood.

  • Evaluation of environmental condition: water and sediment examination of oxbow lakes
    84-92
    Views:
    28

    As a result of the river regulation a number of oxbow lakes have arisen in the floodplain of the Lower-Tisza. The floodplain lakes represent natural values and major recreation areas of the lowland region. Due to the human activity the oxbow lakes' condition declined. It can be shown by the water quality, the channel discharge by deposit, the high eutrophication of the lakes and the heavy metal elevation of the sediment. Discovering these processes, analysing the condition and recultivation of the oxbow lakes came into prominence only in the past few years. Our research aims to conclude the current environmental pollution of the oxbow lakes from statistical analyses of the heavy metal content of the sediment and from the water quality data. The oxbow lakes have been classified by chemistry instead of chemical. Results of the research show differences between the floodplain oxbows and the lakes outside the dam in terms of the quality of the sediment and the nutrient content of the water.

  • Long-term analysis of River Tisza water level data with regard to the ecological water demand of floodplain water bodies
    16-32
    Views:
    231

    One of the main threats of our time is the increasing water demand not only globally, but also locally. These are often met at the expense of ecological water demand, jeopardizing the structural and operational conditions necessary to maintain good ecological status in aquatic and wetland habitats. This is why it is of great importance to explore possible water retention options. In 2019, based on the long-term data series on the water level of River Tisza, we studied the frequency and extent of flooding in the floodplain between Tiszabercel and Gávavencsellő, where there are valuable wetlands, including a ‘sanctuary’-type backwater. This was necessary because recently the floodplains have undergone negative changes. Their water volume has gradually decreased, their valuable wildlife has become rarer, some of them have completely dried out in the autumn and even one of them has burned out. From the analysis of the examined 48-years data, it could be concluded that flooding was relatively frequent in the sampled area, but the extent of water coverage had no significant effect either in space or time. It was also found that only water levels above 700 cm (based on the water meter of Tiszabercel, 98.36 mBf) could adequately ensure that the water bodies are filled up and flushed out. However, there is little chance of this, because of four reasons: (1) water levels of this height are becoming rare; (2) the duration and height of high water levels are mostly short in time; (3) water levels of several water bodies are artificially decreased; (4) the drainage effect of the River Tisza – which has been significantly incised after the river regulation – prevails in the area. Due to all, in the future, there would be a great need to maintain the water levels in the floodplain wetlands as efficiently as possible after the floods – for which we have made specific proposals for the places and methods to preserve the ecologically necessary amount of water.

  • Studying the development of fluvial landforms in the Berettyó-Körös Region using geoinformatic methods
    137-144
    Views:
    157

    Development of fluvial landforms from 1980 till nowadays was studied based on digital elevation maps
    (DEM) composed from contour lines of topographic maps, field data obtained by RTK GPS and aerial
    photos taken by a drone. Greatest denudation of 6-9 metres was measured in the eastern side of the
    erosional valley at Pocsaj caused by piping and mass movements. As a result, the valley widened and
    slightly deepened. Since 1980 around 1-2 metres of accumulation and erosion of similar rate have been
    measured in the secured floodplain environment dissected by abandoned beds, point-bars and swales
    at Kismarja. These values, however, rather reflect the geometric uncertainties and deficiencies of the
    contours of topographic maps than real land changes. Therefore topographic maps can give reliable basis
    for studying the development of lowland landforms only if they depict adequately large sized (minimum
    100 x 100 m) positive or negative forms with great height difference as well (minimum 8-10 m). Accuracy
    of DEMs composed from aerial photos using photogrammetric methods – taking off height faults caused
    by vegetation – is around the same as that of the models created on the basis of RTK GPS measurements.

  • Active point bar development and river bank erosion in the incising channel of the lower Tisza river, Hungary
    13-28
    Views:
    205

    The development of point-bars and bank erosion are critical near-bank processes, as they indicate
    the sediment and hydraulic regime of a river system, thus, they refer to the equilibrium conditions of
    a channel. However, throughout history, rivers have been modified for various benefits which change
    the development of point-bars and the rate of bank erosion. In the Lower Tisza River (Hungary), river
    regulations influenced the channel and floodplain development, altering the natural fluvial processes.
    The aim of the research was to determine the rate of near-bank processes and to make trajectory for
    future river evolution to support future engineering works. The bank erosion and point-bar development
    at human-influenced and freely meandering sections of the Tisza River were monitored since 2011.
    Behind a collapsed revetment, the bank erosion rate was 0.6 m/y, while at a freely meandering section it
    was 2.3 m/y. The studied point-bars are located in revetted and freely meandering sections. Their surface
    eroded within the period. These intensive erosional processes refer to an incising meandering channel,
    which must be considered during future planning of in-channel structures (e.g. revetments, bridges),
    thus, geomorphic methods must be considered in any river engineering scheme.

  • Water chemical analysis of the oxbow lakes near the Upper-Tisza River
    36-42
    Views:
    52

    The Tisza river plays an important role in the life of Eastern Hungary. Beside the river there are several oxbow lakes, cut off meanders. In this paper the water quality of these lakes was examined from
    the section of Tarpa to Rakamaz. 45 oxbow lakes were sampled and the chemical parameters were
    determined. Sodium was used as a pollutant (sewage water) indicator and 2 lakes were found extremely polluted. The lakes outside the dam were slightly polluted because of the lack of renewal of
    the water body and the ones in the active floodplain had good quality parameters.

  • Land use changes of the riparian landscape in Hungary between 1990 and 2018
    82-95
    Views:
    107

    The protection and the restoration of rivers is one of the most important challenges of our time, due to the impact of human activities. The aim of the research was to assess the land use changes in the Hungarian riparian landscape. Several landscape corridors of different (50-100-300-500 m) widths near rivers were analyzed since 1990, using the CORINE Land Cover database. Positive changes in the land use of riparian landscape can be seen: continuous increase in the case of forest areas; and slight decrease in the extent of agricultural land since 1990. Unfortunately, the extent of grasslands and other near-natural areas is reduced; and there has been a steady increase in built-up areas. Examining the changes in built-up areas in more detail, a big increase is shown by the extent of urban green areas. As a continuation of the research, an evaluation methodology is being developed to determine the restoration potential of urban rivers on study area level and on national level. The results presented in this paper on land use changes and land use conditions can be useful for the research about restoration potential at national level.

  • Present tendencies in landscape planning and recognition of the opinion of local citizens on the example of the Tiszazug
    1-9
    Views:
    126

    A survey based on online and face-to face interviews with 104 persons who live in the Tiszazug in the central part of the Great Hungarian Plain. According to the answers the character of the landscape here would change dramatically by disappearance of oxbow lakes, floodplain forests and vineries. The decreasing population and aging of the citizens result in decreasing intensity of landuse, increasing number of abandoned buildings and the attractiveness of the landscape is spoiled by illegal waste disposals and weedy water banks.