Investigation of area slope threshold of gullies in the Zahirabad Watershed, Shazand, Markazi Province

Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. In this paper, the area- slope threshold was investigated in Zahirabad Watershed in Markazi province, Iran. First, based on field surveys and digital elevation model, morphometric characteristics of 14 gullies were measured, accompanied by soil sampling and vegetation cover measurements. Second, homogeneous groups of gullies were defined by factor and cluster analysis and power relations of area-slope was prepared. Results demonstrated that there was no considerable correlation between area and slope of gully watersheds. So, coefficient of determination of creation point and head-cut of gullies were 0.111 and 0.181, respectively. According to the results, the dominant process in creation and head cut development of gullies in Zahirabad was related to flow concentration and rill erosion of high slopes. Considering the prevail of loamy texture of soils land use changes and deterioration of vegetation cover, it is suggested to investigate the optimization of land use schemas, and land cover improvement on sloppy lands with the objective of gully control.