Identification of causes of the occurrence of Gully erosion with emphasis on soil-related factors (case study: Agh Imam watershed)

Gully erosion in one of the different types of soil erosion by water that initiation and advancement of it can tend to the great changes on landscape and degrades the lands. The objective of the current study is to analyze the effects of soil-related factors on the occurrence of Gully erosion in the Age Imam watershed. This watershed, with an area of 5442.45 hectares, is located in the east of Golestan province, and experiences many substantial difficulties due to Gully erosion. In this study, ditches in the region were identified through field study. Then five ditches were selected and 10 soil samples from the within the ditch and 10 from outside the ditch were taken (a region in the adjacent area above the ditches), from two depths (0-30 cm, and 30-60 cm) and were subjected to laboratory analysis. The comparison of the averages of the two statistical populations was used to analyze the physical and chemical characteristics of soil taken from two depths, Results showed that significant differences existed (on a 5% level) among some soil characteristics between surface soil and the soil below that, as: Percentage of Silt (at both depths, taken from the ditch), percentage of saturation humidity (at both depths, taken from the ditch), electric conductivity (at the lower depth, taken from the ditch), neutralizing substances (at both depths, taken from outside the ditches), cation exchange percentage (lower depth, taken from outside the ditch), sodium absorption ratio (lower depth, taken from the ditches), and the percentage of exchange sodium (at the lower depth, taken from the ditches), had an effective role in Gully erosion, due to the higher amounts and statistical significances.