Study on the characteristics of navigation-obstructing of typical serial rapids and regulation in the downstream of Minjiang River

Some sections of mountain rivers have interlocking rapids and troughs, and multiple beaches coexist, and influence each other in rarious complicated ways, which have been the key problems of navigation development in southwest China. To address the problem of unclear ideas and principles for the management of serial rapids in mountain rivers, we analyze the navigation-obstructing characteristics, water and sediment conditions, and evolution of river bed of serial rapids based on the Xinkaihe serial rapids in the lower reaches of the Minjiang River. In addition, calculation analysis and optimization research are carried out by combining the physical model and the two-dimensional flow and sediment mathematical model. The results of the study show that for the problems of “sharp, curved, dangerous and shallow rapids” from upstream to downstream, the regulation scheme should be targeted for each rapid. Firstly, for the problems of “shallow” in the downstream, a combination of “dredging and remediation” should be used to enhance the water-sand dynamics of the shallow section. Secondly, for the problem of “curved and dangerous”, regulating structures should be used to adjust the flow path and improve the flow pattern. Finally, for the problem of “sharp” in the upstream, the focus should be placed on widening the channel and slowing down the flow speed. At the same time, on the basis of avoiding the remediation measures downstream from worsening the “rapid and dangerous” of the upstream rapid, it is also necessary to comprehensively coordinate the sand transport balance of the whole serial rapids. The research results of this paper can enrich the regulation technology of complex serial rapids in mountain rivers, and can also provide a reference for other serial rapids management in China.