József Lóki

Recent Landform Evolution in Hungary

Fluvial geomorphic processes (channel and floodplain evolution) are widespread in the extensive lowlands of Hungary. Since flow regulation in the nineteenth century, river channels have shown adjustments of considerable degree. Some agricultural areas in hills and low mountain basins are seriously affected by water erosion, particularly gully development on loess. Although all sand dunes have been stabilized by now, historically wind erosion has also been a major geomorphic agent in blown-sand areas. The areas affected by mass movements and karst processes are limited but their processes still operate – partly in function of the changing climatic conditions. Applied geomorphological research focuses on ever intensifying human impact on the landscape (particularly in mining districts), which has become the primary driver of recent geomorphic evolution in Hungary, too.

The potential wind erosion map of an area covered by sandy and loamy soils - based on wind tunnel measurements

Summary. Wind erosion causes an enormous problem in agriculture, and the stirred-up dust influences the air quality and is harmful for human health. In the cultivated agricultural areas of Hungary, soils with different textures often suffer from wind erosion, and due to the global climate change an ever increasing risk rate can be expected. In this study we examined in a wind tunnel the thresholds of wind velocity and erodibility of 80 different soil samples originated from an area covering of approximately 5,000 km 2 . Afterwards, based on the resulting data the soils with different texture types were categorized in erosion risk classes. Using the experimental results and the CORINE land cover database, we compiled a potential wind erosion map for the studied area.

Agriculture: Crop Cultivation and Horticulture

Alteration to the surface began with hoed cultivation; it is thus claimed that crop cultivation is the oldest production activity with geomorphic impact. The physical and social factors that influence the type, features, density, etc. of landforms resultant from agricultural activities are summarized. Crop cultivation has its main impact on the planation of the surface. Sloping surfaces impede cultivation, thus humans often reduced slope gradient or established horizontal plots. The relief of gently sloping areas gradually decreases by contour tillage. In areas with no soil conservation (such as in the Mediterranean) bare rocks indicate the full degradation of soils. In large-scale farming of mechanized cultivation, surface levelling is common. Mainly large-scale farmlands are also affected by wind erosion. In arid regions with water deficit, irrigated crop cultivation has been practised for ages and irrigation canals have formed an integral part of the agricultural landscape. Tillage modifies soil erodibility (slope, soil moisture, soil water management and structure, surface roughness and coverage) and thus water erosion, particularly on arable lands with soils on loess parent material.

Parabolic Dunes of the Southern Nyírség

A series of alluvial fans extend into the Carpathian Basin from the encircling mountains, and one of the biggest among them is the Nyirseg, built by the Tisza River and its tributaries. In the late Pleistocene and Holocene aeolian processes reworked its surface, therefore sand dunes are the characteristic forms today. Approximately one quarter of the area of the Southern Nyirseg is occupied by dunes, which form dune fields separated by former river courses. Although previous studies held parabolic dunes as the typical forms, only 6 % of the total dune area covered by filled, partially filled or unfilled parabolic dunes. Most of the dune area (ca 40 %) belongs to the valley-marginal dunes, which are associated with waterlogged paleo-courses and depressions. The rest of the features are transitional between straightened valley-marginal dunes and parabolic dunes. The present dune assemblage developed during the late Pleistocene, although due to human impact the sand was mobilized time to time, and smaller features (e.g. blowouts, hummocks) developed.