Abstract: Hilly red soil region in south China is a region with the most severe water and soil loss in China. Severe soil erosion will lead to soil degradation and will also affect the sustainable development of agricultural production. Studying the erosion law of red soil slope is of great significance for the prevention and control of water loss and soil erosion in hilly red soil region in south China. The features of runoff and sediment yield on red soil slope were studied in this research through artificial rainfall and scouring test. Slope gradient was designed as 5°, 10°, 15°, and 20°, and rainfall intensity at four levels, namely, 0.8 mm/min, 1.2 mm/min, 2.1 mm/min, and 2.6 mm/min, and the corresponding scouring discharge 1.4 L/min, 3.0 L/min, 5.7 L/min, and 7.0 L/min, respectively. Research results are concluded as follows: 1) Under both artificial rainfall and scouring conditions, the initial runoff yield duration of red soil slope declined with the increase of slope gradient and scouring discharge, and such decline was the most remarkable on slope of 5° gradient in the presence of 0.8 mm/min rainfall intensity (1.4 L/min scouring flow rate). On slope of small gradient (5° and 10°), initial runoff yield in artificial rainfall test came earlier than in scouring test. 2) Under both test conditions, runoff stabilized within 15-20 min; sediment load stabilized in 10-15 min under artificial rainfall and 15-20 min under scouring. 3) The total volume of runoff and sediment yield on red soil slope increased with the rise of rainfall intensity and scouring discharge, and such increase was particularly apparent on slopes of small gradient in the presence of small rainfall intensity and scouring discharge. The total volume of runoff in artificial rainfall test was larger than that in scouring test; on the contrary, the total sediment yield in artificial rainfall test was smaller than that in scouring test under small rainfall intensity and scouring discharge, but became larger with the rise of rainfall intensity. 4) In addition, attentions should be paid to the prevention of soil and water loss on slopes of 5° gradient as the total runoff and sediment yield on 5° slope gradient changed more dramatically than on other gradients despite rainfall intensity and scouring discharge. The research results are conducive to understanding red soil erosion and offer data support for the treatment of red soil erosion in south China.

Key words: red soil, artificial rainfall, scouring, runoff volume, sediment load