Determining of Effective Factors on Gully Longitudinal Advancement (Case study: Dareh Koreh Watershed)

Gully erosion is one of the most destructive types of channeled water erosion that removes a considerable volume of soil as it develops. This type of erosion consists of complex a geomorphic process that has been known as an indicator of accelerated soil erosion. In this research the advancement of 25 headcuts were assessed through digital interpretation of multi temporal aerial photos, field observations and GIS data analysis over the two periods of 1967-1995 and 1995-2008. Moreover, the stepwise regression analysis procedure was applied to extract the effective factors on gully head advancement (such as topography, physico-chemical soil attributes and morphology of gully). The results indicated that the mean of gully head advancement over the periods of 1967-1995, 1995-2008 and the mean of two periods were measured 1.36, 1.23 and 1.3 m/y, respectively. Further, regression analysis revealed that headcut's contribution area, distance of gully-head to ridge, height of gully head cut and SAR are the main factors on gully head advancement. Therefore, distance to ridge, headcut high and presence of plunge pool could use as suitable criteria to distinguish the active gullies in order to prioritizing the conservation activities.