CAJ | 학술논문

分汊口的地貌演化格局对于三角洲建造和下游河槽的稳定具有重要作用。作为长江河口的第三级分汊口（南、北槽分流口），形成历史较短，但又经历了长江口最大的水利工程（北槽深水航道工程）的影响，故该分流口的变化是近年来长江河口研究的核心内容之一。本文基于近50 a的地形、流域入海水沙和南北槽落潮分水分沙比等数据，探讨了南北槽分流口的动力地貌变化过程。结果表明：（1）在1998年前，长江口南北槽分流口经历了由不稳定-相对稳定-动态平衡的阶段，其中分流口沙洲洲头出现下挫-上提-下挫、主泓线则经历分流口南侧-北侧-南侧的周期变化，河槽断面由U型发展为W型。（2）长江大洪水是导致分流口地貌格局出现变化的动力因素。在洪水发生的间歇期，分流口地貌则处于由不稳定向相对稳定发展的调整阶段。（3）1998年修建沙洲洲头潜堤工程后，沙洲洲头出现上提-下挫-上提的微弱变化，但总体上沙洲头向北偏移，这导致进入北槽的分水分沙比有所减小。（4）自2002年以来，沙洲洲头因分流口的淤积而缓慢上提，潜堤北侧北槽上段淤积加重，潜堤南侧尤其紧贴潜堤部位侵蚀加剧，南槽分水分沙增大，分流口落潮冲刷槽进一步向南槽发展。
분차구적지모연화격국대우삼각주건조화하유하조적은정구유중요작용。작위장강하구적제삼급분차구（남、북조분류구），형성역사교단，단우경력료장강구최대적수리공정（북조심수항도공정）적영향，고해분류구적변화시근년래장강하구연구적핵심내용지일。본문기우근50 a적지형、류역입해수사화남북조락조분수분사비등수거，탐토료남북조분류구적동력지모변화과정。결과표명：（1）재1998년전，장강구남북조분류구경력료유불은정-상대은정-동태평형적계단，기중분류구사주주두출현하좌-상제-하좌、주홍선칙경력분류구남측-북측-남측적주기변화，하조단면유U형발전위W형。（2）장강대홍수시도치분류구지모격국출현변화적동력인소。재홍수발생적간헐기，분류구지모칙처우유불은정향상대은정발전적조정계단。（3）1998년수건사주주두잠제공정후，사주주두출현상제-하좌-상제적미약변화，단총체상사주두향북편이，저도치진입북조적분수분사비유소감소。（4）자2002년이래，사주주두인분류구적어적이완만상제，잠제북측북조상단어적가중，잠제남측우기긴첩잠제부위침식가극，남조분수분사증대，분류구락조충쇄조진일보향남조발전。
Evolutionary formation of distributary mouth morphodynamic processes is important for deltas building and downward river channel stability.Distributary mouth between the South and North Passage(DMSN),which is the third distributary mouth of Changjiang Estuary,had a comparatively short evolutionary time,which had been experienced seri-ous impacts from the largest hydraulic engineering of the Deepwater Channel Regulation Project.Thereafter,the changes of distributary mouth become the key research topic of Changjiang estuary in recent years.In this paper,data including topography with the time interval of 1950s~2012,water and sediment load into the estuary,and ebb tidal water and sed-iment load into the North and South Passage were collected to analysis the morphodynamic processes of the DMSN.Mean-ingful results are thus summarized as the following.(1)DMSN changes had been experienced 3 stages,i.e.instability, relative stability and dynamic equilibrium before 1998.During these stages,shoal head located at DMSN was appeared as downward decrease,upward shift,and downward decrease again.The thalweg depth was experienced similarly changes shifted from location situated at the south of the DMSN,the north,and the south of the DMSN again.The appearance of river section was from the originated‘U'to the present‘W'formation.(2)The largest floods occurred in the Changjiang River is the determinative hydraulic factor impacting the DMSN morphodynamic processes.However,during the interval of flood occurrences of Changjiang River,DMSN geomorphology is under adjustment from unstable to stable stage.(3) Due to construction of submarine dike at the shoal head in 1998,there were minor shifts of the shoal head from the up-ward to downward change.However,the shoal head was in general leaned to the north which caused decrease in water and sediment load into the North Passage.(4)The shoal head located at the DMSN has experienced slowly upward de-velopment since 2002 due to DMSN accretion.Meanwhile,the northward part of the submarine dike located in the up-stream of the North Passage had been serious accreted.But the southward part of the submarine dike located in the up-stream of the South Passage had been serious eroded which induced and increased in the water and sediment load into the South Passage and a further extension of the ebb channel located at the DMSN to the South Passage.