MULTI-TEMPORAL SOIL EROSION RISK ASSESSMENT IN N. CHALKIDIKI USING A MODIFIED USLE RASTER MODEL

The aim of this work was to test a modified version of the Universal Soil Loss Equation (USLE) for assessing the risks of erosion in N. Chalkidiki, Greece. USLE estimates the severity of erosion, thus assisting the decision process in selecting erosion control measures. Although USLE has several limitations, it was selected because it is the simplest approach while remaining robust, and it partially solves the problem of data availability. Modifications referred to here concerned the es- timation of factors C and k (representing land management and soil vulnerability, respectively). More specifically, the C-factor was estimated using multi-temporal NDVI layers derived from LANDSAT images, while the k-factor was estimated based on the geological map. All USLE factors were calculated as grid layers after processing the original data, then they were multiplied together (according to the USLE) in order to derive the final risk map for three different seasons. A scale of 1:100 000 was selected and the mapping unit was set at 1 ha. The results, assessed for their accu- racy by experts, showed that the use of multi-temporal NDVI gave a better insight than a single date approach in understanding the erosion procedures in the study area and facilitated the com- parison between seasons and areas.