Spatial modelling of gully erosion in Mazandaran Province, northern Iran

Gully erosion is one of the most severe environmental problems in large areas of Iran. The spatial distribution of gully erosion and its susceptibility zonation was studied using different bivariate statistical models, such as frequency ratio (FR), weights of evidence (WofE), and index of entropy (IofE). For this purpose, 109 gully erosion locations were identified and divided into training (70%) and validating (30%) datasets. Effective factors, including elevation, slope aspect, slope degree, slope-length (LS), topographical wetness index (TWI), plan curvature, profile curvature, land use, lithology, distance from river, drainage density, and distance from road were selected to develop maps of gully erosion susceptibility. The spatial relationship between gully erosion and each effective factor was calculated by the mentioned models. The relative operating characteristic (ROC) curve was implemented for evaluating the accuracy of the applied predictive models. Results indicated that frequency ratio model had better performance (80.4%) than the weight of evidence (79.5%) and index of entropy (79%) models. The produced gully erosion susceptibility maps can be helpful to make decisions for soil and water planning and management and finally sustainable development in the Valasht watershed.