Determining the dominant factors affecting the length of permanent gullies using stepwise multivariate regression in southern Iran

The present study is set to determine the controlling factors of the length of permanent gullies in the Khalili watershed, Larestan, southern Iran. Hence, 17 causative factors were measured for 60 recorded gullies. The factors included length, the slope above the head cut, discharging point slope, head cut slope, creation area, development area, surface closed grain, bare soil, vegetation cover, surface litter, permeability, the electrical conductivity of extracts saturation, acidity, organic matter, sodium adsorption ratio, soil texture, runoff height, and shear stress. The most suitable equation between gullies’ length as the response variable and other measured parameters as independent variables was obtained using stepwise multivariate regression. The results revealed that the creation area, development area, and bare soil had the most crucial role in increasing gullies’ length, while the form factor has a decreasing role. Also, critical inferences of this work revealed that, based on Pearson’s correlation coefficient and the attained significance level, the gully length was significantly affected by surface closed grain, shear stress in discharging point, and form factor, and, to a lesser degree, discharging point slope and runoff height. Based on the inferences derived from this study, controlling gully erosion in its head cut and reducing the longitudinal advance of permanent gullies by restoring vegetation cover are recommended.