Assessing Soil Erosion Risk for Rhodes Island, Greece with a GIS-based Multi-Criteria Decision Analysis

Abstract

Reducing erosion in the Mediterranean region is a major priority because of its susceptibility and millennia long human inhabitation. The objective of this paper was to assess soil erosion risk on the semi-arid island of Rhodes, Greece. Rhodes has many protected areas that are part of the Natura 2000 network. To implement this assessment a Geographic Information System based Multi-criteria Decision Analysis was conducted. The Multi-criteria Decision Analysis was a combination of the Analytic Hierarchy Process and the Weighted Linear Combination. The criteria used, in the order of importance, were: I) Land-use, II) Slope, III) Normalized Difference Vegetation Index (NDVI), IV) Geology, V) Distance from Streams, VI) Fire Density, VII) Precipitation, VIII) Soil Quality, IX) Flow Length, X) Distance to Roads XI) Aspect and XII) Wetness. The final erosion risk map for the entire island had ranking values only of 3-6 although the scale ranged from 1-9. This indicates that there are no areas with extreme erosion risk. While less than 1% of the area had an erosion risk of 6, a significant percentage (15.4%) ranked as 5. Land managers should firstly implement best management practices in these areas (ranked as a 5 and 6). When comparing the Natura 2000 areas to the non Natura 2000 areas, the Natura 2000 had a larger percentage (~ 6%) of areas that ranked as 5, while the non Natura 2000 areas had a larger percentage (~ 6%) of areas that ranked as 4. Since the Natura 2000 areas are protected by the European Union, it was expected that they would be less vulnerable to erosion. The percentages of this study indicate that additional measures need to be implemented in these Natura 2000 areas to reduce soil erosion.