Abstract: Indoor artificial rainfall simulation tests are used to study the effect of gravel on the runoff and sediment yield from the engineering accumulation slopes in Guanzhong Plain and to analyze the relationship between water and sediment, under the rainfall intensities of 1.0, 1.5, 2.0 and 2.5 mm?min-1 for gravel mass fractions of 10%, 20% and 30% in comparison to a pure Lou soil slope (i.e. no gravel). The results show that 1) the runoff rate and mean flow rate are correlated insignificantly with gravel fraction (P > 0.05), but significantly with rainfall intensity (P < 0.05). 2) At rainfall intensity of 1.0-2.5 mm?min-1, mean sediment yield is decreased with the increasing gravel fraction, following a power function relationship. Relative to the no-gravel case, sediment yield of the slope is decreased by 17.1%-67.5%, 13.8%-81.1% and 25.5%-92.0% at gavel fractions of 10%, 20% and 30% respectively. 3) As the rainfall intensity decreases from 2.5 mm?min-1, the curve of accumulative water and sediment changes from a linear function to a power function (P < 0.01). This study helps predict and reduce soil and water loss of the engineering accumulation in Guanzhong region.

Key words: engineering accumulation, mass fraction of gravel, Lou soil, runoff yield, sediment yield, water-sediment relationship