Gully erosion in Hungary, review and case study

Abstract

Soil erosion is one of the most significant land degradation processes on agricultural areas in Hungary. 25% of the total area of Hungary (more than one-third of agricultural land) is affected by water erosion, 16% by wind erosion. The role of gully erosion has been recognized only lately. The hilly countries of Hungary are mainly covered by unconsolidated sediments, mainly by loess. Loess covered areas are prone to erosion and mass movements. The paper provides an analysis of environmental conditions of gully development in Hungary. The role of gully erosion in total soil loss at catchment scale is shown on the example of the Tetves catchment (120 km2, subcatchment of Lake Balaton catchment). A completely filled up sediment reservoir can be found at the catchment outlet. An attempt is made to determine the share of the material removed by gully erosion, based on the analysis of the sediment accumulated in the reservoir. If there is more topsoil in the reservoir then the role of sheet erosion is more important in the catchment, while more subsoil in the reservoir points to considerable gully erosion activity. Humus content and Caesium-137 activity were used as indicators of the topsoil. Gully erosion activity was investigated in the whole catchment in 1968, 1984 and 2004 using maps, air photos and field survey. The results show that approximately half of the deposited sediments came from the “subsoil” layer pointing to the important role of gully erosion. The main conclusion is that the Caesium-137 method proved to be very well applicable to identify sediments originating for gully erosion activity. For policy makers it is suggested that land use planning should ensure a minimum risk of gully erosion with special emphasis on afforestation.