Identify the important driving forces on gully erosion, Chaharmahal and Bakhtiari province, Iran

Abstract Soil erosion is a serious threat to human well-being and life. Gully erosion is an important process of soil degradation that causes significant soil loss in different climates. Many researchers believe that the reason for paying attention to gully erosion is the high volume of this type of erosion compared to other types of erosion, and gully erosion produces several times more sediment. The soil that is eroded by the gully causes great economic losses by sedimentation in waterways, dam reservoirs, and port areas. The main aim of the present study was to identify the most important factors affecting gully erosion development in the Chaharmahal and Bakhtiari provinces of Iran and to obtain appropriate solutions to control this type of erosion. Areas affected by gully erosion in the study area were identified using field visits. Using the geographical location of identified gullies, a map of the spatial distribution of areas affected by gully erosion in the study area was prepared. Finally, among the identified gullies, 24 active and reagent gullies were selected for further studies. Gully volume as a dependent variable and factors such as sodium ratio, percentage of soluble salts, percentages of clay, silt, and sand in gully areas, gully floor slopes, gully upstream slopes, mean rainfall, and vegetation density as independent variables were considered. The measured parameters were statistically analyzed using SPSS software with a multiple regression relationship. The results showed that the three factors of the gully upstream slope, the percentage of soluble salts in the soil, and the density of vegetation with a coefficient of determination of 0.94 had the greatest effect on gully development in the study area. The slope of the watershed above the gully forehead (gully upstream slope) alone accounts for 86% of the changes in gully erosion volume. The main reason for this result can be attributed to the flooding of this factor and the speed of surface runoff.