Plot-size Runoff and Sediment Yield Affected by the Type of Geological Formations and Implications for Water Erosion in a Semi-Arid Region

Examining the relationship between factors affecting the amount of sediment production is essential in understanding the erosion process and watershed response. The aim of this research is to investigate the relationship between runoff and sediment components and some soil properties in the geological formations of a watershed in a semi-arid climate in the Northwest Iran. The study approach in the current research is field experiments and statistical data analysis to assess the soil attributes influence on runoff-sediment components. After determining the sampling locations in different geological formations, a rainfall simulator was used to simulate rainfall. The components of runoff initiation time threshold, runoff termination time, runoff amount, and sediment concentration were recorded through field experiments. Also, the factors of soil organic matter, soil texture and percentage of different sizes in soil samples were measured. The differences between different geologic formations in terms of runoff and sediment components were analyzed using ANOVA. Then the Scheffe's post hoc test was used to examine the differences between the mean of classes. According to the results, the runoff volume of the obtained samples was between 135 and 9504 ml, and the volume of sediment was between 4 and 299 g/l, which indicates the high variability of runoff and sediment among geological formations. The results showed that the runoff termination time component had a significant difference (& alpha; < 0.05) in different geological formations. Comparing the difference between the geological formations based on the percentage of clay showed that the difference in the runoff termination time and the volume of the runoff was significant (& alpha; < 0.05). In comparing the difference between the geological formations based on soil sand amount, there was also a significant difference in the runoff initiation and termination time (& alpha; < 0.05). In general, it can be said that the type of geological formations can strongly affect the runoff and sediment yield components. Incorporating the factors attribute to geological formations along with rainfall amount and intensity, and land use attributes can help in better estimation of sediment production in future studies.