Comparison of runoff and erosion simultaneous threshold in the soil of different land uses

By determining the threshold of runoff and erosion by rain simulator, it can be determined rainfall amount that causes runoff in different conditions with more speed and accuracy and lower cost. After determining the threshold of runoff and erosion in each region, using biological methods and operations can prevent the conversion of runoff to flood. In this research, considering that the threshold of runoff and erosion occurs simultaneously and mistakenly only the term of runoff threshold is used in different researches and do care less about erosion threshold and in order to determine the most important factors affecting the simultaneous threshold of runoff and erosion of different land uses of Aghajari and Gachsaran formations, part of Margha and Kuhe Gach watersheds of Izeh city with an area of 1609 and 1202 Hectare selected. This study was conducted to determine the relationship between runoff and erosion threshold using a rain simulator with some soil physical and chemical properties such as very fine sand percentage, sand, clay, silt, pH, electrical conductance, moisture, calcium carbonate and organic matter in different land uses of Aghajari and Gachsaran formations. Then, sampling was done at 13 points and with three replicates in Aghajari and Gachsaran formations at different rainfall intensities of 0.75, 1, and 1.25 mm/min in 3 land uses of rangeland, residential area, and agricultural land using a rain simulator. SPSS and EXCEL soft wares were used for statistical analysis. The most important factors affecting runoff and erosion threshold were identified by multivariate regression. In general, in Gachsaran formation in all three land uses, clay and calcium carbonate showed the highest role in increasing the threshold of runoff and erosion. The most roles in reducing runoff and erosion threshold showed very fine sand and moisture content in Gachsaran Formation. However, in the Aghajari Formation, in all three land uses, the highest role in increasing the threshold of runoff and erosion, showed clay and organic matter. In addition, the most roles in reducing the threshold of runoff and erosion in the Aghajari formation showed very fine sand and soil sand and salinity.