This research applies the fuzzy set theory via Geographical Information Systems

(GIS) - based analysis to investigate the slope erosion by water. The main steps of this procedure are the definition of the input variables (rocks’ susceptibility to erosion, slope angle, slope morphology), the development of a fuzzy inference system based on theoretical and empirical knowledge, transforming the input to output variables (erosion – deposition) and the visualization of the output variables (spatial distribution of the erosion-deposition processes). The method was applied at the Corinth drainage basin, located in the north-eastern part of Peloponnese (Greece), where a series of catastrophic erosional events have recently occurred.