Sediment yield, runoff and hydraulic characteristics in straw and rock fragment covers

Soil loss is a major global challenge threatening the future of soil and water resources. The significant implications of soil loss necessitate the adoption of appropriate soil conservation practices and soil management solutions according to the regional climate. Investigation of the effects of soil cover on soil erosion process can provide the information necessary for the success of soil and water conservation practices. In this study, the effect of rock fragment and wheat straw covers on the hydraulic properties, runoff, and sediment yield were investigated in plot scale laboratory experiments using artificial rainfall. Experiments were carried out on the plots prepared based on two types of soil cover (rock fragment, wheat straw) and three coverage ratios (35%, 65%, and 90%) in addition to a control (bare soil) plot, each with three replications. In these experiments, 2 m long, 0.55 m wide, and 0.30 m deep plots with a 15% slope were subjected to artificial rainfall with a duration of 70 min and an intensity of 90 mm h(-1). The results showed a significant difference at the 5% level between the mean runoff rate of rock fragment cover (0.38 mm min(-1)) and that of wheat straw cover (0.42 mm min(-1)), but no such difference was found in terms of sediment production (Sig. = 0.73). The Wheat straw cover was more effective than rock fragment cover in increasing the Manning roughness (n) and Darcy-Weisbach friction (F) coefficients, and flow depth (h) and reducing the velocity (V), Reynolds (Re) and Froude (Fr) numbers. It was also found that, for both covers, increasing the coverage ratio increased the h, F, and n and decreased the runoff and sediment production, V, Re, and Fr. After investigating the relationship between hydraulic properties and sediment concentration in different plots, a direct linear regression relationship with a relatively high coefficient of determination (R-2 > 0.614) and a significant relationship at the 1% level (P < 0.01) were found between sediment concentration and discharge per unit width (q), V, h, and Re. In general, it can be concluded that rock fragment cover and wheat straw cover both have a satisfactory effect on the hydraulic properties and runoff and sediment production.