This paper oriented to study hydrodynamic characteristics of steep loess slopes (25°~50°)

in an attempt to lay down a foundation for elucidating the in-depth relationships of the hydrodynamic characteristics of shallow water flow on slopes with soil erosion. An indoor experiment was carried out to simulate rainfalls on steep loess slopes. The experiment was designed to have only one soil type (loessal soil)

three rainfall intensities (1.0 mm/min

1.5 mm/min and 2.0 mm/min) and six slope gradients (25°

30°

35°

40°

45° and 50°). Results showed that:(1) Soil erosion rate increased with rising rainfall intensities on slopes with the same gradient

and under the same rainfall intensity

the effects of slope gradients on soil erosion rate exhibited a critical point in gradient

that was

between 40° and 45°. On slopes with gradient lower than the critical point

soil erosion rate increased with rising slope gradients

whereas on slopes with gradient higher than the point

soil erosion rate decreased with rising slope gradients. (2) Flow shear stress

stream power and unit energy of water-carrying section were increased with the rising rainfall intensities and slope gradients

while stream power had the best regularity. (3) The increasing power functions were found between soil erosion rate with flow shear stress

unite stream power and unit energy of water-carrying section

with the determining coefficient of R2(ω)>R2(τ)>R2(E). So stream power was the best one of all the hydrodynamic parameters tested to describe the soil erosion process on the steep loess slopes.