Characteristics of the Land Degradation in the Stavnic River Basin

摘要

Located in the Central Moldavian Plateau, the Stavnic catchment is associated to a left tributary of the upper Barlad River, and extends on 21,341 ha of which 39% is under forest. The typical hilly landforms, the alternation of permeable and impermeable rocks (clays, sands, loess-like deposits), the unrolling of wetted and dry periods, the sequence of freeze and thaw cycles, and the influence of the anthropogenic factor triggered the acceleration of land degradation processes. The present day geomorphic processes such as soil erosion, gullying, mass movements and silting of reservoirs represent a major threat to the local environment. Soil erosion on the agricultural land covers mainly the land with slopes of over 5%, and it highlights through different stages of intensity. By data processing, gained from the soil surveys undertaken by O.J.S.P.A. Iasi and Vaslui, it is obviously that moderate-excessive soil erosion extends on 52% of the surveyed area. The gully erosion apparently plays secondary role in the Stavnic catchment. However, there has been identified a total number of 330 gullies, most of them being included into discontinuous gullies class, often located on the hillslopes. Landslides are the most representative geomorphologic processes and they extend on 12,006 ha, which represents 56% of the Stavnic catchment. One mention must be made, that in the context of climate aridisation occurred during the last three decades, the landslides are almost all stabilized. The majority of the few active landslides have frequently formed through the reactivation of the old landslide diluvia. By using the Cesium-137 technique in dating the recent sediments from the Cazanesti accumulation, within the lower Stavnic catchment, the mean siltation rate of 4.5 cm yr-1 after the Chernobyl nuclear accident was estimated.