Estimation of soil erosion, sediment discharge and deposition in reservoir using empirical methods with emphasis to the influence of rainfall

Due to the lack of specific site measurements of soil loss or sediment transport, the development of a theoretical frame- consisted of empirical relations and models- is attempted, so as to estimate the annual quantities of soil loss, sediment yield and deposition of sediments. The aim of this thesis is to estimate the amount of deposition for dimensioning the dead volume on Tsiknias dam, at the homonymous stream and the deriving basin which is located in the central area of Lesvos island. The soil erosion models RUSLE (Renard et al., 1997) and Gavrilovic (Gavrilovic, 1988) are applied, for the estimation of the soil loss, in accord with the sediment delivery ratio (Vanoni, 1975) in order to determine the sediment yield. In addition, the Lara and Pemberton (1963) methodology is used for the total volume of depositions in the reservoir to be determined. Emphasis is given on the analysis of the rainfall erosivity, which is considered the most significant influential factor of erosion. Analytical calculations are carried out (Renard and Freimeund, 1994), so as to estimate the erosivity from the processing of the precipitation sensor data in a 12 years period. The results are compared with the ones, deriving from experimental correlations, and are at the same time utilized in the creation of indicative relations of estimating R factor. The RUSLE is therefore applied in an environment of GIS software, aiming at the inclusion of spatial variance in the calculations, along with the reclaim of the ability to define the most vulnerable in erosion areas, through the development of maps. Moreover, according to the offered possibilities by the GIS, there is an effort to exclude the possible deposition areas from the calculations of soil loss, in order to mitigate the existence of overestimations.