Effect of stone content on water flow velocity over Loess slope: non-frozen soil

- Flow velocity over slopes of different stone contents was measured.
- Velocity increased with stone content from 0% to 10% and decreased at higher stone content.
- Discharge rate of 2 to 8 L/min had the greatest difference of impacts on flow velocity.

Stony soils are commonly found worldwide and are considerably studied for their hydrological characteristics and effect on soil erosion. Water flow velocity is an important parameter in understanding the effect of stone content on hydrodynamics and soil erosion. In this study, laboratory experiments were used to measure rill flow velocity by using electrolyte tracer method under different hydraulic conditions: flow rates of 1, 2, 4, and 8 L/min, slope gradients of 5°, 10°, 15°, and 20°, and stone mass contents amounting to 0%, 10%, 20% and 50%. Nine sensors, which were 1 m apart along the 8 m long rill, were used to measure flow velocity by tracing solute transport. Measured flow velocity increased with slope gradient and flow rate. The highest increase in flow velocity was measured from 15° to 20° which were also affected by flow rate. Effects of discharge rate on flow velocity presented the largest difference when flow rate increased from 2 L/min to 8 L/min at slope gradients higher than 5°. The effects of different factors were quantified by a regression model with high accuracy of 0.99. Maximum flow velocity of water was predicted at 15.23% of stone content. Flow velocity increased with 0-15.23% of stone content but decreased at higher values. This study aims at further understanding the hydrodynamics of soil erosion and sediment transport behaviors in hillslopes with different stone contents to obtain information for quantifying soil erosion on stony slopes.