Page - 348 - in Book of Full Papers - Symposium Hydro Engineering

ANALYSIS OF KEY INFLUENCING FACTORS FOR THE EVOLUTION OF THE SAND BAR IN THE TRIBUTARIES IN THE XIAOLANGDI RESERVOIR AREA* Yuanjian WANG Senior Engineer, Yellow River Institute of Hydraulic Research, Zhengzhou, China Enhui JIANG Deputy Dean, Yellow River Institute of Hydraulic Research, Zhengzhou, China 1. INTRODUCTION Sand bar is a geomorphologic pattern which is often observed in estuaries and reservoirs. For estuaries, Sand bar alleviates water depth and blocks water and sediment transportation. It is also a threat for navigation (Li, 1997). For reservoirs, San bar blocks river mouth of tributaries, reduces storage volume of reservoirs (Li et al., 1985; Wang and Hu, 2003). Therefore, the research on the evolution of sand bar is valuable for engineering. Separately, the evolution of sand bar in estuaries is influenced by the flow conditions upstream and oceanic dynamic conditions downstream (Hu and Zhang, 2006). And the evolution of sand bar in reservoirs is caused by two ways： the first way usually occurs in a small or median reservoir, the slope in the main channel is mild while in the tributaries is steep. In flood season, the water with sediment and gravel will flow from the source of the tributaries to the main channel and deposit in the river mouth of the tributaries(Qi, 1996); the second way usually occurs in a large reservoir, the slope in the main channel is steep while in the tributaries is mild. In flood season, the water with sediment and gravel will flow form the main channel to the tributaries and deposit in the river mouth of the tributaries (Wang et al., 2011). Because the evolution of sand bar is influenced by many different factors, it is a focus for scientists and engineers. Limited by the complexity of the problem and traditional techniques, former research on sand bar mainly fixed on the influence of a single factor (Shen et al., 1983; Li and Ji, 1988; Yang et al., 2001). With the development of new analysis techniques, now the research turns to be quantitative (Wu et al., 2002) and modelling (Zhang et al., 2003). Accordingly, this paper established a response formula between the height’s increment of the sand bar in the tributaries in the Xiaolangdi Reservoir area and a number of influencing factors. Using sensitive analysis, the key factor for the evolution of the sand bar is also found to support the engineering constructions for dealing with sand bar in the reservoir area. * titre de l'article complet 348