Assessment of the important Factors on Gully Erosion in Arid and Semi arid Region in Ilam Province

One of the main types of water erosion is gully erosion in which a large volume of soil is washed away. Gullies، in addition to producing a large amount of sediment and consequently filling dams and tanks، make a vast area of lands unusable and change the overall appearance of the earth. In this study، considering the importance of gully erosion in Ilam province، effects of environmental and biological factors on this kind of erosion in three areas of Dehloran، Mehran (Saleh Abad) and an area near to Ilam city (Chawar) were investigated. For field studies، after detecting the major gully areas، in these areas different types of gullies were identified. Gullies were classified into three groups of linear، bulbous، claws. Then slope، geographical position، total size of the area، altitude، land use، vegetation and gravel percentage factors، and gully features including: length، depth، upper and lower widths، gullies’ head height were identified. Collecting soil samples from both surface and deep walls of the gullies was done. To investigate the influence and the relationship of various factors on the gully erosions under the study from the results of field visits، laboratory operations and data analysis we used Duncan Polynomial Test and Pearson; besides، for determining the most important factors affecting gully erosion analysis of the main components is used. Results showed that slope and altitude had a significant impact on Gully erosion in such a way that the maximum erosion was on a slope of 10-15%، and at lower altitudes، but geographical position has not such an impact. In addition، the maximum erosion was for agricultural land use and the minimum was for forest land use، and among physical and chemical parameters surface sand، total size of the area، superficial EC were positively correlated and vegetation percentage was negatively correlated with gully erosion. Based on the results، superficial sand، and depth of the gullies and total size of the area were the most affecting factors on gully erosion.