Development of automated multicriteria GIS analysis of gully erosion susceptibility

In order to determine the presence and spatial distribution of gully erosion on the Pag Island (Croatia), a gully erosion susceptibility model was developed using GIS-based multicriteria decision analysis (GIS-MCDA). To simplify the GIS-MCDA modelling process, we developed automated multicriteria GIS analysis - GAMA method that is applicable to other karstic areas. The analytic hierarchy process (AHP) was used to assign specific weight coefficients to each criterion in regard to its importance for gully erosion occurrence. In total four different gully erosion susceptibility models were created, based on different criteria weight coefficients. The final GIS-MCDA model (3) was chosen based on the quality validation. Validation of GIS-MCDA model quality was done using ROC curves that were made based on two reference gully datasets. Validation confirmed the consistency of created models and proved that existing gullies are within high gully erosion susceptibility areas. The entire Pag Island was divided, through generated gully erosion susceptibility model into areas of: very low susceptibility, low susceptibility, medium susceptibility, high susceptibility and very high susceptibility. High and very high gully erosion susceptibility areas cover around 30% of the total area of Pag Island. Developed GAMA method allows easier and faster application of GIS-MCDA methodology in gully erosion susceptibility modelling, as well as in various other research areas.