Investigation of the Relationship between Roughness Coefficient and Detachment and Deposition Rate in Plowed Soil using Rainfall Simulation in Laboratory Flume

Soil erosion is a process that is affected by surface roughness (SSR) and soil texture. The aim of this study was to investigate the relationship between roughness coefficient and detachment and deposition rate in plowed soil samples of drylands of Kouheen, Sararud and Gachsaran regions due to their susceptibility to erosion after plowing, by simulation. Two precipitations (R1 and R2) with a distance of 4 hours with an intensity of 111 mm / h were simulated in a 5.8 m2 laboratory flume with a slope of 12%. To determine soil loss, runoff was collected with sediment. Also, photographs were taken before and after each rainfall and a digital elevation model with a pixel size of 2 mm was prepared and from it, surface soil roughness was calculated and divided into three classes (rough, medium and soft). The difference of the digital elevation model (DOD) before and after each rainfall (R0, R1 and R2) was calculated to determine the amount of detachment, deposition and sediment delivery ratio (SDR) and their trend was roughly studied. Soil loss in Gachsaran soil sample were measured in 4796 and 3909 g, Kouheen, 3465 and 2464 g and Sararoud, 2679 and 2105 g, respectively. The ratio of harvest to sedimentation in the first event was 5.4, 7.3 and 1.8 in Kouheen, Sararud and Gachsaran soils and 3.2, 1.9 and 1.2 in the second event, respectively. The amount of SDR in the second rainfall in Kouheen, Sararud and Gachsaran soils has been 4.4, 6.3 and 2.3 times higher than R1, respectively. The direct regression relationship between soil loss and roughness with a coefficient of determination (R2) of 0.89 (P <0.05) was obtained. Finally, by preparing the DEM and eliminating its uncertainty, reliable amounts of detachment and deposition can be obtained.