Validation of the predicting model for land vulnerability to gully erosion in arid watersheds (Case study: Boushehr province)

This research was conducted to validate a conceptual fuzzy model for predicting gully hazard zonation under arid climatic condition in Bousher province. Based on gully map of the Province، Dareh Koreh Watershed was selected and terrain mapping unit was prepared through overlaying different maps including landuse، land component، lithology and slope. In order to determine the soil attributes، soil infiltration and land protection cover، three gullies were chosen in each terrain unit and soil samples were taken. Based on gully density ratio in every terrain unit، quantitative values of the model parameters were obtained as an input for standard fuzzy set operations including fuzzy intersections and union، fuzzy Gamma operator and index overlay in GIS. The results indicated that the model which includes lithology، slope gradient، soil type، average annual precipitation، landuse and land protection cover is adequetly able to predict vulnerable areas to gully erosion. Moreover، based on observed gully and predicted maps، the fuzzy Gamma operator of 0. 8 showed to be the most reliable method for gully hazard zonation map. In the method، slope class of 0-5%، hilly landforms and soil protection areas less than 10% are the most influencing components for gully development.