本文選題：長(zhǎng)江口 + 南槽��； 參考：《華東師范大學(xué)》2014年碩士論文

【摘要】：河口處于陸地河流與海洋交接的地帶,是河海相互耦合作用的關(guān)鍵區(qū)。作為陸地、海洋、大氣和生物之間各種過程相互作用最為活躍的區(qū)域,河口往往受潮汐、潮流、波浪和入海徑流等一系列自然營(yíng)力的建造與破壞,人類的各類活動(dòng)如大型水利工程也對(duì)其產(chǎn)生巨大影響,這些影響更為直觀地體現(xiàn)在河口的地貌變化。因此,河口的時(shí)空變化過程尤其是動(dòng)力地貌演變一直是陸海相互作用研究的核心和焦點(diǎn)內(nèi)容。 南槽作為長(zhǎng)江口第三級(jí)分漢口,是長(zhǎng)江輸水輸沙的主要通道。在北槽深水航道整治工程之前,一直作為長(zhǎng)江口出海主航槽。然而,近年來受長(zhǎng)江入海水沙變化和長(zhǎng)江口大型涉水工程的影響,南槽的動(dòng)力地貌過程發(fā)生了巨大改變,南槽正不斷進(jìn)行自我調(diào)節(jié)以適應(yīng)這些變化。顯然,分析和揭示近年來南槽的動(dòng)力地貌變化過程對(duì)理解長(zhǎng)江河口響應(yīng)人類活動(dòng)和自然驅(qū)動(dòng)作用的變化具有重要意義。 本文基于長(zhǎng)江河口南槽2012～2013年水文觀測(cè)數(shù)據(jù)、懸沙樣品資料,大面積走航所采集表層沉積物樣品和多年來水下實(shí)測(cè)地形數(shù)據(jù)分析南槽的懸沙輸移擴(kuò)散機(jī)制及其動(dòng)力成因、區(qū)域內(nèi)動(dòng)力沉積特征,探討沉積物的輸運(yùn)過程與輸運(yùn)方式,進(jìn)而研究該區(qū)域河槽沖淤演變的基本規(guī)律。主要結(jié)論包括： 南槽內(nèi)以往復(fù)流為主,漲落潮流流向與河槽走向基本一致,落潮平均流速大于漲潮平均流速,落潮歷時(shí)大于漲潮歷時(shí),流速和懸沙濃度都隨著小潮到大潮潮汐潮流作用不斷增強(qiáng)而變大。觀測(cè)期間的歐拉余流UE方向均指向口外,斯托克斯余流Us方向均指向陸,二者流速均從小潮到大潮呈現(xiàn)明顯的增加趨勢(shì)。 南槽沉積物總體較粗,其中沉積物以砂質(zhì)粉砂為主,次要類型為粉砂、粉砂質(zhì)砂、泥和砂。從沉積物的分布來看,南槽自上而下河槽呈現(xiàn)為粗～細(xì)～粗的分布格局,相應(yīng)沉積環(huán)境的水動(dòng)力表現(xiàn)為強(qiáng)～弱～強(qiáng)的遞變過程,體現(xiàn)出徑流、潮流以及其他水動(dòng)力之間的博弈作用。同時(shí),沉積物的分形計(jì)算表明南槽內(nèi)沉積物粒度組成具有分形結(jié)構(gòu),分維值的大小能夠反映沉積物的演化過程。此外,南槽上段沉積物自上向下沿河槽方向運(yùn)動(dòng)；南槽下段(出�？谖恢煤途哦紊骋韵�)呈現(xiàn)從深水區(qū)向淺水區(qū)域輸運(yùn)的明顯趨勢(shì),沉積物向九段沙尾和南匯東灘部位運(yùn)動(dòng),九段沙沙尾呈現(xiàn)淤積態(tài)勢(shì)。 長(zhǎng)江口南北槽分流口以1998年為界,呈現(xiàn)不同的地貌狀態(tài)。1998年以前,分流口地貌經(jīng)歷了由不穩(wěn)定-相對(duì)穩(wěn)定-動(dòng)態(tài)平衡的階段,其中分流口沙洲洲頭出現(xiàn)下挫-上提-下挫、主泓線則經(jīng)歷分流口南側(cè)-北側(cè)-南側(cè)的周期變化,河槽斷面由U型發(fā)展為W型。長(zhǎng)江大洪水是導(dǎo)致分流口地貌格局出現(xiàn)變化的動(dòng)力因素。在洪水發(fā)生的間歇期,分流口地貌則處于由不穩(wěn)定向相對(duì)穩(wěn)定發(fā)展的調(diào)整階段。1998年修建沙洲洲頭潛堤工程后,沙洲洲頭出現(xiàn)上提-下挫-上提的微弱變化,但總體上沙洲頭向北偏移,這導(dǎo)致進(jìn)入北槽的分水分沙比有所減小。自2002年以來,沙洲洲頭因分流口的淤積而緩慢上提,潛堤北側(cè)北槽上段淤積加重,潛堤南側(cè)尤其緊貼潛堤部位侵蝕加劇,南槽分水分沙增大,分流口落潮沖刷槽進(jìn)一步向南槽發(fā)展。 南槽河段在1989年江亞南沙并灘前后呈現(xiàn)兩種不同的地貌演化階段。江亞南沙并灘前,南槽普遍發(fā)生淤積,兩側(cè)淺灘不斷淤漲,河槽總體上呈縮小態(tài)勢(shì)；江亞南沙并灘后,南槽南岸普遍性沖刷,上段江亞南沙和下段九段沙不斷淤漲。南槽呈現(xiàn)出“上段沖刷加深,中段微沖、兩側(cè)邊灘淤積”的狀態(tài)。同時(shí),河流和海洋作用二者此強(qiáng)彼弱間的變化,使得南槽整體呈現(xiàn)出季節(jié)性的洪枯沖淤變化規(guī)律：上段在洪、枯季均受徑流和落潮流影響,呈沖刷態(tài)勢(shì)；中段尤其是沿九段沙區(qū)域呈現(xiàn)明顯洪沖枯淤特點(diǎn),下段則具有洪淤枯沖的特點(diǎn)。此外,近期南槽地貌的沖淤演變過程與南北兩側(cè)工程的實(shí)施進(jìn)度密切相關(guān)。基于此,受人類活動(dòng)影響的南槽動(dòng)力地貌過程需要進(jìn)一步深入研究。
[Abstract]:Estuaries are the key areas of the interaction of rivers and seas. As the most active regions of land, sea, atmosphere and biology, the estuaries are often built and destroyed by a series of spontaneous forces, such as tides, tidal currents, waves, and sea runoff, and human activities such as large scale. Water conservancy projects also have a great impact on them, which are more intuitively reflected in the geomorphic changes in the estuary. Therefore, the temporal and spatial changes in the estuaries, especially the evolution of the dynamic landforms, have been the core and focus of the study of land sea interaction.
The South trough, as the third grade Hankou in the Yangtze Estuary, is the main channel for water transport and sediment transport in the Yangtze River. Before the regulation of the north channel deepwater channel, it has always been the main channel of the Yangtze Estuary. However, in recent years, the dynamic and geomorphic process of the South trough has changed greatly by the change of the water and sand in the Yangtze River and the large water project of the Yangtze Estuary in recent years. It is obvious that the analysis and Revelation of the dynamic and geomorphic process of the South trough in recent years is of great significance to the understanding of the changes in the human activity and the natural driving effect of the Yangtze Estuary.
Based on the hydrological observation data of the South trough of the Changjiang River estuary for 2012~2013 years, the sediment sample data, the surface sediment samples collected from the large area and the measured topographic data under the inflow of the river for many years are used to analyze the mechanism of suspended sediment transport and diffusion in the South trough and its dynamic causes, the characteristics of the dynamic deposition in the region, and the transport process and transport mode of the sediment. The basic law of scouring and silting evolution in the area is studied.
In the South trough, the past reflow is the main flow. The flow trend is basically the same as the channel direction. The average flow velocity of the ebb tide is greater than the average velocity of the tide, and the ebb tide is greater than the ebb period. The velocity and the suspended sediment concentration increase with the effect of the tide to the tide tidal current. The UE direction of the Euler residual current in the observation period is all pointing out of the mouth, Stokes's surplus. The flow direction of Us is all directed toward land, and the velocity of the two directions presents an obvious increasing trend from neap tide to spring tide.
The sediments in the South trough are generally coarser, and the sediments are mainly sandy silt sand, and the secondary types are silt, silty sand, mud and sand. From the distribution of sediments, the bottom trough of the South trough shows a coarse to coarse distribution pattern, and the hydrodynamic force of the corresponding sedimentary environment is strong to weak to strong progressive process, reflecting runoff and tidal current. At the same time, the fractal calculation of sediment shows that the size composition of sediment in the South trough has a fractal structure, and the size of the fractal dimension can reflect the evolution process of the sediments. In addition, the sediments in the upper part of the South trough are moving upward and downward along the river trough direction, and the lower section of the South trough (the outlet position and the nine section sand) is presented. The obvious trend of transport from deep water area to shallow water area is the movement of sediment to nine segments of sand tail and the east beach of Nanhui, and the nine segments of sand tail are silting.
The diversion port of the north and South trough of the Yangtze River estuary is bounded by the 1998 as the boundary, presenting different geomorphic state.1998 years ago, the distributary mouth geomorphology experienced the stage of instability relative stability dynamic balance, in which the diverting estuary sandbank head fell down - up - up and down, the main branch line experienced the periodic change of the southern side of the distributary mouth - the north to the south side, and the channel section from the U type. The large flood of the Yangtze River is the dynamic factor that causes the change of the distributary geomorphic pattern. In the intermittent period of the flood, the distributary geomorphology is in the stage of the adjustment from the unstable to relatively stable development. After the construction of the Sha Chau Chau head dike project in the.1998 year, the head of the Chau Chau Island is slightly changed, but on the whole the sand continent is in the sand continent. From the north to the north, the ratio of water and sand to the North trough has been reduced. Since 2002, the head of the Chau Island has been slowly raised because of the siltation of the distributary mouth, and the siltation in the upper part of the North trough on the north side of the dike is aggravated, and the south side of the dike is especially closely attached to the submerged dike, and the water separation and erosion in the South trough will increase, and the tidal flushing trough of the diversion outlet is further developed to the South trough.
There are two different geomorphic evolution stages in the south channel of the south channel of Nansha in 1989. Before the Nansha and shoal of Jiangya, the silt in the South trough is generally silted up in front of Jiangya and the beach in the south of Jiangya. The river trough is constantly silting up, the river trough generally shows a shrinking trend; after the Nansha and the beach in Jiangya, the South Bank of the South trough is generally scoured, the upper reaches of Nansha and the lower section of the upper section of the Yangtze River are constantly rising. The South trough presents. At the same time, the change of the strong and weak between the two sides of the river and the ocean, and the change of the strong and weak between the river and the ocean, makes the whole of the South trough show the seasonal variation of the flood and scouring and siltation: the upper section is affected by the flow and the ebb flow in the flood and the dry season, and the middle section is especially along the nine section of the sand area. In addition, the evolution of the erosion and siltation in the southern trough is closely related to the progress of the north and South bilateral projects. Based on this, the dynamic geomorphic process of the South trough affected by human activities needs further study.

【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TV148;P737.121

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本文編號(hào)：1806063