Soil loss in Rills and Its Temporal Variation During Rainfall in Different Soil Textures

Rill erosion is the detachment of soil particles by scouring and transport of sediments by a concentrated water flow on the hillslope. It plays an important role in soil loss on the hillslope. Various soil properties affect its resistance to rain drops impact and runoff shear stress، and consequently they influence rill erosion. The study was conducted to determine rill erosion and its temporal variation during rainfall in different soil textures. Simulated rainfall experiments were performed in eight soils (clay، clay loam، sandy clay loam، loamy، silty loam، sandy loam، loamy sand and sandy) at the plots (1Í 1. 2 m) installed in a hillslope. The plots were exposed to five simulated rainfalls with an intensity of 60 mm h-1 for 60-min. Rill erosion variation during each rainfall was determined by collecting sediment in a storage tank at the outlet of the plots. Results indicated that rill erosion was strongly affected by the soil texture (p ≤ 0. 01). The highest and the lowest rill erosion were observed in clay (322 g m-2) and sandy soil (zero)، respectively. Rill erosion rate was associated with water infiltration rate and transportability of particles in the soils. Rill erosion rate increased during the rainfall event due to disruption of soil aggregates and runoff generation. In the soils rill erosion rate rapidly increased at early times and finally reached a relatively constant level. The loamy soil showed lower variation in rill erosion rate than other soils due to greater resistance to soil erosion.