Spatial Distribution of Water Erosion Using Stochastic Modeling in the Southern Isfahan Province, Iran

Abstract

Soil erosion is often regarded as one of the main processes of desertification. Many parts of the world have been affected by soil erosion, resulting in major environmental problems and causing land degradation, loss of agricultural land, destroyed villages and infrastructure as well as historic places. Soil erosion particularly affects arid and semi-arid regions due to long dry periods and often-intensive precipitation events. The soil particles washed off by surface and subsurface runoff are the biggest pollution factor in terms of amount and volume. Our case study is located in the Southern Isfahan province, Central Iran. The area is severely affected by water erosion such as gullies, rills and badlands. The main aim of this study is to predict the spatial distribution of the different water related erosion types and their susceptibilities using a probabilistic Maximum Entropy Model approach based on the following environmental layers: lithology, soil textures, land use, precipitation, Normalized Difference Vegetation Index and topographic indices derived from an SRTM DEM with 30 m spatial resolution. An inventory of the erosion forms and features such as gully erosion, rill erosion and badland erosion was determined based on Google Earth images (GE), aerial photos and a field campaign conducted in 2018. In order to validate the stochastic modelling approach, we divided the entire sample in a train (70%) and test (30%) dataset. We validated the model performance using the Area Under Curve (AUC) value. The model yields good (rill and gully erosion) to excellent (badland) results for both train and test data. The spatial prediction of susceptibilities for rill, gully and badland erosion show that in total more than 40% of the study area is affected by water erosion processes (4.8% rill erosion; 23.4% gully erosion and 17.9% badland erosion). The knowledge of susceptible areas is crucial for a proper land management and related soil conservation measures to guarantee a sustainable land use.