Determination of the Influencing Factors on the Length Extension of Gullies in Ghazeian Watershed, Fars Province

Due to soil degradation and abundant of sediment production, the exact recognition of affecting factors on gullies erosion, and the impact of various factors on gully’s formation and development, require a more accurate study. In this regard, in the present study the length of gully, the area above headcut, headcut slope, percent of closed grain, bare soil, cover vegetation, litter, saturated electrical conductivity, pH, percent of organic matter, sodium absorption ratio, and percent of clay, silt and sand were measured in 30 gullies in 2018. Factor analysis with SAS software (version 9.1) was performed to determine the factors affecting the samples classification. Backward regression method in SPSS software (version 16) was used to determine the affecting factors on extension length of gullies, considering the length of gullies as dependent variable and other measured parameters as independent variables. The results of this study showed that the saturated extract electrical conductivity, the area above headcut and the percentage of bare soil factors play the most important role on the length extension of gullies in the Ghazeian watershed, located in the north of Fars province. Therefore, it is recommended to control erosion at headcut and through establishing the adaptable and resistance canopy copy cover, reduces the uncover area and increases the roughness coefficient. Also, it is essential to have a watershed in different part (climate) of the country having gully erosion to perform accurate research on soil particles, canopy cover, type and rate of rainfall, runoff height, shear stress, flow velocity, morphological characteristics, type of slope and its cover, mechanism of creation and expansion of gullies, and the gully erosion control methods.