Erosion-Based Classification of Mountainous Watersheds in Greece: A Geospatial Approach

Soil erosion is a key factor in land degradation across Mediterranean mountain regions, yet comprehensive assessments at the national scale are still uncommon. In this study, the Erosion Potential Method (EPM, Gavrilović method) was applied to 1127 mountainous watersheds of Greece in order to classify their erosion severity through the erosion coefficient (Z). Information on relief, geology and vegetation was combined so that each watershed could be assigned to one of five erosion severity classes. The classification revealed that 53.2% of the watersheds fall into the slight category, while 26.0% are moderate and 16.3% are very slight. Severe cases account for 3.9%, and only 0.5% are classified as excessive, though these few basins are locally very important. The distribution is far from uniform: severe watersheds occur more often in North Peloponnese (EL02), Thessaly (EL08), and the Western Sterea Ellada (EL04). By contrast, Crete (EL13) and the Aegean Islands (EL14) include a relatively greater proportion of watersheds in the moderate category. This variation indicates that erosion risk should not be considered a uniform condition across the country. Even watersheds with low overall Z may contain steep or degraded slopes that act as local hotspots. Consequently, effective management should move beyond country-wide averages and instead focus on the sub-areas that are most exposed and susceptible to erosion.