GEOMORPHOLOGY AND SEDIMENTOLOGY OF RIVER BERETTYÓ CONSIDERING ENVIRONMENTAL PROTECTION

Riverbed sediments accumulated over recent decades along a 9 km long section of Berettyo River between Esztar and Kismarja were studied from geomorphological, sedimentological and environmental protection points of view. The riverbed along a narrow floodplain was modified several times due to the natural development of bends along the course of the river. Bars developed in the modified environment were sampled with the help of drillcores. Grain size distribution and elemental concentrations were determined at every 5 cm. Ground-penetrating radar measurements were performed as well along the studied section of the riverbed. In order to better understand the radar image and the development of bars three boreholes were drilled into a particular bar. Based on archive aerial photos, natural and anthropogenic changes in the morphology of the riverbed and in the sedimentation conditions in it can be observed. Forms in the riverbed were exposed by the five boreholes. Based on grain size distribution, the material of the bed can be classified into two groups: fossil material composed of silt, clay and fine sand and a recently deposited material dominated by coarse and medium-coarse sand. Elemental concentrations and their change are in close relationship with grain size distribution. The concentration of several elements changes together. Based on the geoaccumulation classification of the elements and the limit values of the appropriate decree,neither element can be considered pollutants and that neither element exceeded the pollution limit of the KvVM-EitM-FVM decree 6/2009 (IV.14).GPR measurements and boreholes exposed the structure of a 17 m long, similar to 3-4 m wide and max. 1 m thick sedimentary body. At least four major flooding cycles can be identified in the translational accretion of the point bar based on its graph and GPR profile.