The Influence of Lithology and Soil on the Occurrence and Expansion of Gully Erosion, Toroud Basin – Iran

Gully erosion, is often associated as one of the most severe forms of soil erosion processes. Gully erosion forms after removal of soil along drainage lines from water surface after raining or thawing snow. Also gully erosion often results in much displacement of the soil mass, culminating in sedimentation, and degradation of the land. And has tremendous impacts on human activities which includes decreasing soil nutrients and agriculture productivity, river channel sedimentation and increasing floods and impact on water resources development within a river basin. Therefore type of the soil has a big role in its erosion and moving. According to the importance of the subject the research tries to evaluate the effect of soil and lithology on the formation and expansion of gully erosion and discover the erosion-sensitive area in Toroud basin- Iran. In order to achieve predetermined goals, the research examines two major objectives, which focuses on the effect of lithology and soil type on the formation and extension of gully erosion. To examine these objectives, this research uses GPS and GIS for preparing the maps. And also applies Soil test to define of the soil kind in this area. Hence Study in geology and soil type is a big conception for managing and using the land properly.