Study On Empirical Model Of Sediment Yield For Single Rainstorm Based On Unit-Watershed In Chabagou Catchment Of Hilly Areas Of Loess Plateau, North China

Hilly area of Loess Plateau is the main source of the Yellow River sediment. Soil and water loss in this region is extremely serious. Researchers have built many statistical models of runoff generatoin and sediment yield, but the problem of factors optimization of runoff and sediment is still not completely solved. This problem need still be further explored. Further more, the study on sediment delivery ratio(SDR) model, which is a very good tool that can simulate erosion and sediment of watershed, is at the research stage, and there is a long way when applied. In view of this, the thesis, based on the data of experiment station located in northern Shaanxi, launched the study on factors of unit-wateshed runoff generation, including rainfall, antecedent rainfall content, vegetation cover, and topography, and of unit-wateshed sediment yield, including runoff depth and peak discharge, and on the SDR model. Specific conclusions are as follows:(1) For unit-watershed(its area<1 km2) without soil and water conserveation measures, rainfall and antecedent rainfall content are the main factors of affecting runoff generation for single rainstorm, and vegetation cover and topography are not. In the factors of rainfall, the composite index made up of rainfall volume and 10-min rainfall intensity is most closely related to runoff depth, and 10-min rainfall intensity related to runoff coefficient. So this composite index and 10-min rainfall intensity arc the optimalizing ones. In the factors of antecedent rainfall, the 11～15-day rainfall precipitation prior are most closely to antecedent soil moisture and their difference are not significant.(2) Based on the study of factors of affecting sediment concentration of single flood, it is found that peak discharge of single flood and maximum sediment concentration of single flood are important affecting factors. Also according to the definition of sediment transportation content of single flood, runoff depth and sediment concentration of single flood are respectively proportional to watershed sediment, and two watershed transportation sediment modesls were biult, which catch great modelling accuracy. Deep analysis found that, influenced by different flow mechanisms, for the events less than 300t/km2, the results modeled by logarithmic function was better than that by exponential model. However, the results modeled by exponential modeling was better than that by logarithmic modeling for the events larger than 1000t/km2.(3) The average of SDR for years in Shejiagou is less than 1. The range of SDR for single rainstorm is from 0.483 to 1.111. The most affecting factor of SDR model is maximum sediment concentration, followed by runoff coefficient, sediment storage days and rainfall duration, and the index of sediment storage days is much stronger than rainfall volume, rainfall duration and average rainfall intensity.