With artificial simulation rainfall tests

runoff processes on the bare loess slope are studied and the following results are obtained:(1) Runoff rate varied with rainfall course and could be described with logarithmic equations.Runoff rate didn't change until 10～15 min after rainfall began;(2)Slope gradient influenced runoff depth and could be described with parabola equations.The critical slope degree was about 25°

above which runoff rate changed its trend;(3) Generally runoff depth changed with slope length and their relations could be describedwith logarithmic equations and the critical length was 80 cm;(4)Rainfall intensity affected runoff depth much more greatly than slope gradient did and could be described with linear equations.The action of the latter was al2 most glossed over by that of the former;(5)The integrated impact of the three factors on runoff depth could be expressed using a plural linear function.Rainfall intensity showed much more influential on runoff depth than slope length and gradient.