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Accumulation studies at specific sampling areas of the active floodplain in the Upper-Tisza region
Published August 23, 2017

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.

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Hydromorphological assessment of the lower Hungarian Drava section and its floodplain
Published August 28, 2016

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. Th...e 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.

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Studying floodplain roughness in an Upper Tisza study area
Published July 14, 2021

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.

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Evaluation of environmental condition: water and sediment examination of oxbow lakes
Published December 27, 2011

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 h...igh 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.

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Land use changes and their effect on floodplain aggradation along the Middle-Tisza River, Hungary
Published March 21, 2019

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.

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Long-term analysis of River Tisza water level data with regard to the ecological water demand of floodplain water bodies
Published July 14, 2021

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 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.

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Heavy metal content of flood sediments and plants near the River Tisza
Published December 31, 2008

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 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.

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Studying the development of fluvial landforms in the Berettyó-Körös Region using geoinformatic methods
Published September 4, 2016

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 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.

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Present tendencies in landscape planning and recognition of the opinion of local citizens on the example of the Tiszazug
Published July 14, 2021

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 citiz...ens 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.

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Active point bar development and river bank erosion in the incising channel of the lower Tisza river, Hungary
Published December 20, 2019

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 th...e 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.

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Water chemical analysis of the oxbow lakes near the Upper-Tisza River
Published December 31, 2007

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.

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