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• Active point bar development and river bank erosion in the incising channel of the lower Tisza river, Hungary

  13-28

  Gabriel Jonathan Amissah

  Tímea Kiss

  Károly Fiala

  Views:

  424

  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.

• Types and characteristics of the oxbow-lakes in Lower-Tisza-valley - classification from landscape planning perspective

  19-25

  Zsófia Molnár

  Views:

  147

  The study area is located in Hungary on the South of the Great Plane called Alföld in Hungarian. There are ten oxbow lakes are located in the region of the Lower Tisza Valley. The quality of the area’s oxbow lakes are rather different. There are protected, highly valuable sites in terms of landscape and nature conservation, yet degraded areas utilized for economic purposes can also be found. In the course of river-control in the Lower Tisza Valley was affected by the 84-90th cutoffs, therefore oxbows have been formed in the area. Four of these oxbows are on the part that is not effected by floods, and six of them are located in the active floodplain.The attributes or usage of oxbow lakes allow for a complex system of categorisation. The assessment and classification of oxbow lakes can establish the grounds for assessment, as well as for planning the interventions of landscape restoration.

• Evaluation of environmental condition: water and sediment examination of oxbow lakes

  84-92

  Margit Tamás

  Andrea Farsang

  Views:

  111

  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.