Estimation of soil erosion and sediment discharge in Greece

In a period of rapid changes in both climate and land use, due to global change, it is vitally important to be able to assess the state of soil erosion at a European level, using an objective methodology. This methodology refers to the empirical model calculation of soil erosion, RUSLE equation. The Joint Research Centre (JRC) which is the European Commission's science and knowledge service, has obtained data from all EU countries to estimate the factors model in various raster analysis, and the soil erosion (RUSLE2015). The files are freely available without charge to the site of European Ground Centre (http://esdac.jrc.ec.europa.eu/themes/erosion).

The K-factor is estimated for the 20,000 field sampling points included in the Land Use/Cover Area frame (LUCAS) survey and then interpolated with a Cubist regression model using spatial covariates such as remotely sensed data and terrain features to produce a 500 m resolution K-factor map of Europe. The R-factor is calculated based on high-resolution temporal rainfall data (5, 10, 15, 30 and 60 min) collected from 1.541 well-distributed precipitation stations across Europe. The C-factor was modelled in non-arable lands using a combination of land-use class and vegetation density while in arable lands C-factor is based on crop composition and land management practices (reduced/no tillage, cover crops and plant residues). The LS-factor is calculated using the recent Digital Elevation Model (DEM) at 25 m and applying the equations proposed by Desmet and Govers (1996). The P-factor takes into account a) contour farming implemented in EU agro-environmental policies, and the protection against soil loss provided by (b) stone walls and (c) grass margins.

The data processed in a environment of GIS software to create the maps of each RUSLE factor for Greece and the individual water districts, afterwards to identify the most vulnerable in erosion areas. Moreover, according to the offered possibilities by the GIS, exported the statistical characteristics of each factor and the value of soil erosion in Greece and in reservoirs of Kremasta and Marathona. Then is calculated the sediment delivery ratio (Vanoni, 1975) to determine the sediment yield in order to compare the result values with the corresponding values from previous studies.