东江沙卵石河床浅滩-深潭序列水沙演变特征

东江是珠三角网河区入汇河流之一，属少沙河流，其上游浅滩-深潭序列密集分布，河床结构的演变特性尚不清晰。选取东江浅滩-深潭序列河段进行现场河床质与推移质测量，结合试验得到不同流量和坡降中水流与河床在无上游来沙补给中的互馈机理。试验结果表明:浅滩与深潭交替造成沿程平均流速不连续变化，浅滩中部在洪水流量的塑造下容易产生紊动能峰值。无上游来沙条件下，序列中粗化层的形成、破坏过程交替与循环发生，其中静态分选是主导因素且导致沿程级配不连续。流量与坡降的增大促进浅滩-深潭序列发育，同时使得深潭与浅滩的纵向长度缩短；有上游来沙条件下推移质输沙率增大，无来沙条件下输沙率减小。

Water and sediment evolution characteristics of pool-riffle sequences in gravel-bed rivers of the East River

The East River is one of the confluence rivers in the Pearl River Delta, which belongs to less sediment river. Pool-riffle sequences are densely distributed in the middle and upper reaches of the channel, but the evolution characteristics of that under the condition of no sediment supply are not clear. Therefore, it is of certain scientific significance to improve the understanding of evolution rule. This study selected the sequences of the East River to measure the bed surface and bedload, and obtained the feedback between flow and bed morphology without sediment supply under different flow and slope in the laboratory. Experimental results show that the alternation of pools and riffles results in the discontinuous variation of average-velocity longitudinally, and the peak value of turbulent kinetic energy is easy to occur in the middle riffle under the shape of flood discharge. In the absence of sediment supply, the formation-destruction processes of periodic armoring layer occur alternately, in which static sorting is the dominant factor and leads to discontinuous gradation longitudinally. The increase of flow discharge and slope effectively promoted the sequence development, but at the same time shortened the length of pools and riffles. With or without upstream sediment supply, the variation of bedload transport in the sequence is enlarged, i.e.,the bedload transport rate in the sequence increases with sediment supply;on the contrary, the bedload transport rate decreases without sediment supply.