Abstract: Sand bars often form at the mouth of the tributaries into a sandy river reservoir. They affect the normal functions of the reservoir, but no effective treatment method is available so far. This paper presents a long-term prevention and control method of these sand bars that is based on mobile diversion piles and verified by flume model experiments. The results show that in the case of no control measure, a sand bar forms in the tributary mouth, and develops at a speed proportional to the flow and sediment discharge in the mainstream. Its cross section shows a parallel uplift, its vertical profile takes an inverted V shape, and its highest elevation is formed in the highest turbidity zone of the intersection area. After the control piles are installed, the opening of a water barrier is closed during the high mainstream water level, so as to make most of the sediment settle down and deposit outside the barrier. In the low water level period, the opening is activated to make the water body already stored in the tributary flow through a narrow passage between two diverting walls, and to allow this flow to scour the sand bar so as to form a stable gully at its upper surface and supply as a connection of the main stream to the tributary. Our model experiments show this method can achieve the effect of long-term prevention and control of the sand bar. The method features a clear mechanism, low cost, flexible operation, and lasting effect, so its further improvement could lead to a new practical technology for long-term prevention and control of sand bars.

Key words: sandy river reservoir, tributary, sand bar, long-term prevention and control, mobile diversion piles, water-sediment regulation, river dynamics