Studies on changes of diversion ratio of the Southern and Northern Branches and navigation channel training of the Minjiang River

CHEN Cheng; ZHENG Chaoying; WANG Zhihui; CHEN Haoyan; HUANGFU Kailong

doi:10.3969/j.issn.1000-1123.2025.10.009

Abstract：Dynamic evolution of the diversion ratio of the Southern and Northern Branches in the lower reaches of the Minjiang River and studies on channel training strategies are crucial for navigation safety of the region,stability of flood control system and sustainable development of urban areas.By collecting data of diversion ratio of the Southern and Northern Branches and channel training,studies were made on influencing factors and change process of the diversion ratio after 1975.Based on analysis of the history of channel training of the Huai'an and Southern and Northern Branches,new ideas for channel training of the Southern and Northern Branches were proposed considering the current situation of diversion ratio.The study results show that the upstream hydropower stations and large-scale sand mining are the main factors leading to changes in the diversion ratio.Sand mining and artificial spur dike construction in the Northern Branche caused significant scouring of the riverbed and a big increase of the diversion ratio.From 1975 to the present,the diversion ratio of the Northern Branche has increased first and then decreased,while the diversion ratio of the Southern Branche has shown an opposite trend.After the catastrophic flood in 1998,the riverbed at the entrance of the Southern Branche was washed through,and the combined effects of tidal uplift and sand mining increased,reversing the diversion ratio and gradually making the Southern Branche the main discharge channel.This change has resulted in siltation increase in the Northern Branches and a sharp increase in flow velocity in the Southern Branche,posing multiple threats to navigation capacity of the waterway,safety of bridges crossing the river,and stability of flood control dams.Regarding the above trend,a new model of intelligent renovation that"combines dredging and blocking"was developed.An intelligent system that can adjust the diversion ratio of the Southern and Northern Branches was designed through opening the gate of the Northern Branche.