The sediment delivery ratio is a crucial factor in conducting research in soil erosion and sediment yield relationship. Most previous research only focused on the topography as well as other environmental influence on the sediment delivery ratio. Many researchers compared its difference among drainage basins.
Experimental results at Yangdaogou, a tributary of the Wangjiagou drainage basin in the Loess Plateau, China, indicate that the range of sediment delivery ratio changes with time. Based on the data collected from 1963 to 1968 at Yangdaogou, the calculated long-term average sediment delivery ratio was close to 1.0. Due to temporary storage and re-transportation in the bottom of the gully, inter-annual sediment delivery ratio ranged from 0.36 to 1.12. The range of storm sediment delivery ratio was between 0.36 to 1.85. According to the X2 test, the frequency of storm sediment delivery ratio followed a normal distribution N (1.02, 0.38). The mean, median, and mode were all around 1.0. Other frequency of sediment delivery ratio for each storm can be calculated by the following probability function:
Correlation analysis between 11 causative parameters and the storm sediment delivery ratio showed a significant power function relationship. The regression equation of storm sediment delivery ratio can be expressed as:
SDR = 0.0277R-0.29 C0.19 Sm0.59 (Ea/E)0.44
This equation has both a very high correlation coefficient and explicit physical meaning. Besides, the four selected parameters can be easily obtained from field experiment stations. Calculation of storm sediment delivery ratio based on this equation for more than 20 events between 1963 and 1968 have attained a very high degree of accuracy as compared to the field data. It is feasible, therefore, to use this equation to predict the storm sediment delivery ratio and to explain in some degree the mechanism of sediment delivery at Yangdaogou.