The effects of land use type on soil erodibilty indices in Galyan-Atasu Dam Watershed, Trabzon, N.E. Turkey

Erodibility indices together with other soil properties of Atasu Dam watershed in Trabzon, Turkey, were analyzed according to land use regimes (grassland, cultivated land, coniferous forest land and broadleaf forest land) and the granite parent material from which the soil develops. The findings could be applied to future management plans with the aim of enhancing the ability of Atasu Dam to supply water for drinking, domestic use and irrigation to the region. Forty sample plots having the same northern aspect were selected from bordering lands. Cross-section soil samples from depth levels of 0-10 cm and 10-30 cm were gathered from the selected sites. Particle size distribution, soil organic matter (SOM), dispersion ratio (DR), erosion ratio (ER), colloid-moisture equivalent ratio (C-MER), structural stability index (SSI), water dispersible clay (WDC), clay dispersion ratio (CDR), clay flocculation index (CFI), exchangeable cations, exchangeable sodium ratio (ESR), sodium adsorption ratio (SAR) and soil reaction (pH) analyses were performed. A variance analysis was carried out in order to determine if the obtained results varied according to land use type. Soil samples from a variety of sites in areas with granite as parent material were applied to erodibility indices and the sites were found to be susceptible to erosion. Some other characteristics were also found to be effective on the erodibility indices, including the relationship of soil organics, which was also considered to be to a factor of interest in this study. Soils that were developed from granite parent material in areas covered by forest were observed to be more susceptible to erosion. These results were fairly significant in the context of the study area of the Galyan-Atasu Dam watershed. This study suggests that incorporating these findings in planning and management-related activities can potentially lead to improvement of the basin and contribute to the economic life of the dam.