Determining soil loss via streambank and gully erosions in the Tortum-north sub-watershed within the Coruh River basin

When look at the historical development of soil, the soil formation is the result of very long processes. Although the formation of soil takes very long time, it is very easy and fast to erode or transport under the absence of necessary protection. In situ conservation of fertile soils lost by erosion is important both for the sustainable use of agricultural land and for the survival of forest areas. Streambank and gully erosion is one of the most important types of erosion increases soil loss and accompanying sedimentation. The aim of this study was to measure streambank and gully erosion soil loss from 1st, 2nd order streams and gully channel using "erosion pin method" in Tortum-North watershed within the Coruh River Basin. In order to calculate total soil losses, bank soil bulk density, height and the area of the bank and the total stream length were measured during the two-year study period. In the end of the study period, the measured average erosion rate was 1.6 cm/yr (first year rate: 0.7 cm/yr, second year: 2.5 cm/yr). The average soil loss rate was 29.6 t km-1 yr-1 (first year rate: 20.5 t km-1 yr-1, second year: 38.8 t km-1 yr-1). The highest soil loss was 8818 t yr-1 (%73) contributed by the gully channels compared to first and second order streams. The total soil loss by all the gully and streambanks was 12014 t yr-1. In conclusion, considering the two-year study period the measured erosion rates were low and that can be explained by the low rates of the precipitation amounts. Thus such studies should be carried out for a longer period so that the wet periods or rainy years can be accounted on the effects of bank erosion in holistic way.