The aim of this study was to investigate the relationship between the effects of rainfall intensity and aggregate sizes on sediment concentration and hydraulic parameters. Flow velocity, flow width, shear stress and stream power are the hydraulic parameters. The impact of various rainfall intensities with differing aggregate sizes (D1.18 mm and D2.00 mm) was also studied. Under the rainfall simulator, the different aggregate sizes, D1.18 mm and D2.00 mm, were set up at a slope angle of 20o. The flow of runoff was collected for 2 hours at several intervals (30, 60, 90 and 120 min). Then, the hydraulic parameters and concentration of the sediment were measured. As a result, the increased rate of rainfall creates a higher concentration of sediment on a steep slope from 7.988 to 3233.569 gm-3 and 2.954 to 976.736 gm- 3 for aggregate sizes D1.18 mm and D2.00 mm, respectively. Generally, as the flow depth and shear stress were reduced, the estimated sediment concentration was higher. On the other hand, flow velocity and unit stream power were directly related to the sediment concentrations.