瓯江江心屿河段分流比演变及其影响因素

Evolution and influence factors of diversion ratio of Jiangxinyu reach in Oujiang River

研究分汊河段分流比变化及原因,对河流综合保护利用具有重要意义。瓯江是典型的山溪性强潮河流,其下游的江心屿河段分流比多变。通过收集大量的水文地形资料,结合数学模型与物理模型试验结果,分析了江心屿河段自然条件和人类活动影响下分流比变化规律及原因。研究结果表明:①历史上江心屿河段主支汊易位频繁。20世纪70年代,在整治工程影响下,北汊单向淤积,主汊从北汊逐渐移至南汊,1999年后进入相对稳定期。②分流比变化与水沙条件、边界条件和人类活动密切相关。在1970年以前自然交替变化期,较强的径潮流共同作用、洲滩边界变化、上游河势及大洪水作用等是分流比变化的主要原因;在近几十年人类活动影响下,河道边界条件相对稳定,分流比趋于稳定。

It is of great significance to study the changes of diversion ratio of bifurcated river for protection and utilization of a river.Oujiang River is a typical mountain-stream and strong-tidal river,where Jiangxinyu reach is located at the its downstream reach and its diversion ratio varies frequently.After collecting hydrological and topographical data,the mathematical model and physical model of Jiangxinyu reach were adopted to analyze the changes of the diversion ratio under conditions of nature and human activities.The results showed that:(1)the location of the main branch of Jiangxinyu reach moved frequently in history.After the completion of the regulation projects in 1970s,sedimentation problems occurred in the north branch,and the main branch changed from the north branch to the south branch gradually.After 1999,the diversion ratio was in a relatively stable situation.(2)The change of diversion ratio was closely related to the water-sediment conditions,river and shoal boundaries and human activities,etc.Before 1970,the diversion ratio changed frequently under natural conditions,which were mainly affected by co-action of runoff and tidal currents,changes of shoal boundaries,changes of the river regimes in the upstream reach and floods.In recent decades,the river boundaries conditions had been relatively stable and the diversion ratio had been in a relatively balance situation due to human activities.