Author(s): Yan Tao

Linked Author(s):

Keywords: Reservoir confluence; Deposit bar; Confluence ratio; Turning point;

Abstract: River confluences in reservoir area usually create the deposit bars on intersection zone, especially the tributary entrance bar that is quiet adverse to reservoir operation. Take Baishi reservoir confluence located in Northeast china as the representative, Field investigation and model test were reported. Considering the variable confluence ratios and reservoir storage levels, the depth average velocity of cross section along the reach was tested, then the sediment transport capacity was calculated, which could explain the formation mechanism of deposit bar and its distribution character. Results suggest: tributary flow velocity always firstly increased then deceased along the reach, and changed more notable under the greater confluence ratio more than 0.5; the changing characteristic of sediment transport capacity was similar to flow velocity, and it would keep reducing from tributary channel to the downstream confluence when confluence ratio was greater than 0.5. While the situation in mainstream reach is quite different, no matter how big the confluence ratio was, mainstream flow velocity and sediment transport capacity always firstly increased then deceased along the reach, greater confluence ratio means sharper change, and the turning point located in the intersection zone. Due to the inhomogeneous changes of sediment transport capacity, the deposit bar formed in different place, which means the distribution of deposit bars could be deduced according to the confluence ratio during the main sediment transport period in flood seasons. As the result the Discriminate Conditions for deposit bar distribution based on the confluence ratio was established. By using the measured Prototype data, the relationship between the confluence ratio and distribution of deposit bar was verified which is consistent with the research results; As the reservoir water level increased, both flow velocity and sediment transport capacity weakened, as well as the change rate along the reach.

DOI: https://doi.org/10.3850/38WC092019-1129

Year: 2019