本文選題：長江河口　切入點：地貌演變　出處：《華東師范大學》2014年碩士論文　論文類型：學位論文

【摘要】：長江三角洲是長江流域的終端,兩千年來隨著長江大量下泄泥沙在河口區(qū)淤積,三角洲岸灘持續(xù)向外推展,直至上世紀80年代仍處于持續(xù)快速淤漲狀態(tài)。但是,隨著近30年來上游泥沙補給減少和頻繁的圈圍工程,長江口岸灘淤漲速率減緩,部分岸段呈現侵蝕趨勢,岸灘穩(wěn)定性勢必受到影響,直接關系到近岸工程、航運和人民財產安全。因此,在流域來沙持續(xù)減少,圍墾、東海和長江大橋及青草沙水庫等近岸工程增加,以及全球氣候變化等多重原因的驅動下,長江口區(qū)自潮間帶至水下岸坡發(fā)生了何種變化、演變趨勢如何等問題亟待深入研究。本文對長江口岸灘水文泥沙、沉積物、地貌進行觀測,并分析近30年不同時期的海圖資料,在此基礎上,探討長江口岸灘動力沉積地貌演變特征及影響因素,為港口工程和今后岸灘穩(wěn)定性防護工程建設提供參考依據。主要研究結果如下： 1.北港近岸潮流呈明顯往復流特性,落潮優(yōu)勢流明顯,岸灘演變主要受到落潮流的控制：自2004年至2012年,北港河槽上段洪季漲、落潮垂線平均流速、含沙量持續(xù)減小,含沙量減少約0.2kg/m3；同一時間段,枯季漲、落潮垂線平均流速、含沙量經歷了先減后增的變化過程,其中,2007年至2012年枯季漲、落潮垂線平均含沙量均增加1倍以上。南匯南灘地處開敞海域,潮汐潮流作用相對較強,洪、枯季實測水體含沙量均大于1.23kg/m3；2004年至2012年,南匯南灘洪季漲、落潮垂線平均流速增大；漲潮垂線平均含沙量減少；落潮垂線平均含沙量略有增大；枯季漲、落潮垂線平均流速、含沙量均大幅減小。 2.近30年來,長江口岸灘表層沉積物中值粒徑Dso與沉積物組分呈“向北變細、向南粗化”的變化特征,橫沙東灘北岸、長江和東海大橋下等主要大型工程附近淺地層沉積物柱狀樣粒序向上顯著變粗。 3.目前,除崇明東灘和九段沙外,長江口潮灘普遍較窄、坡度較陡,大部分岸段海塘外潮灘寬度在30-150m,少數岸段無鹽沼植被。近30年來,南北邊灘0m等深線以淺潮灘無明顯淤漲,崇明島奚家港至東灘南側沿岸岸灘Om等深線逐年蝕退；南匯嘴0m等深線內潮灘略有淤進,南灘0m等深線變化甚微。 4.近30年來,北港南北岸多段水下岸灘剖面下凹形形態(tài)特征明顯,坡度變陡,部分岸灘形態(tài)演變受岸外沙體變遷影響顯著；值得注意的是,2009年青草沙大堤合龍工程后至今,北港岸灘整體恢復淤積格局,青草沙水庫北岸沖刷由凸岸前緣有所下移,堡鎮(zhèn)港凹岸、東海大橋下方以及橫沙島北沿均發(fā)生侵蝕沖刷。南匯南灘水下岸坡坡度近30年來明顯增大,灘底發(fā)生沖刷,-7～-8m水深處灘底下蝕近1m；-5m水深以淺岸灘以凈淤積為主,-5～-6m等深線為水下岸灘沖淤節(jié)點；特別是自南匯邊灘圈圍工程及東海大橋建設以來,南灘及大橋下方岸灘大幅沖刷�？傮w上,以北港為代表的“江岸型”水下岸坡具有寬度窄、坡度陡、年際變幅大以及岸坡剖面坡折明顯的特點；而以南匯南灘為代表的“潮灘型”水下岸灘則具有岸灘寬闊平緩、剖面形態(tài)相對穩(wěn)定等特點。 5.影響近期岸灘演變的因子主要包括流域入海泥沙銳減、水動力條件差異、近岸大型工程建設、河槽沙體變遷以及鹽沼植被覆蓋。流域入海泥沙銳減是長江口水下岸坡坡度增大、潮灘淤漲速率減緩等侵蝕格局形成的全局性影響因素。鑒于水動力條件的差異性,受落潮流主控的“江岸型”水下岸灘與潮流作用為主的“潮灘型”水下岸灘發(fā)育與演變特點迥異；而且,長江口人工岸線新形勢下的近岸水動力條件發(fā)生顯著變化,勢必影響岸灘塑造和調整。圈圍及近岸大型工程是導致潮灘大面積損失,局部沉積物粗化的主要原因。河槽沙體變遷和鹽沼植被覆蓋對長江口局部岸灘演變起重要作用。
[Abstract]:The Yangtze River Delta is the terminal of the Yangtze River Basin, two thousand years with lots of sediment in the estuary of Yangtze River water siltation, delta beach continued outward development, until the last century, 80s is still in the rapid siltation state. However, with nearly 30 years of upstream sediment supply reduction and frequent reclamation project, the Yangtze River beach the siltation rate slowed down, part of the coast erosion present trend, bank stability will be affected, directly related to offshore engineering, shipping and people's property safety. Therefore, the reclamation in sediment decreased continuously, and the East China Sea and Yangtze River bridge coastal engineering and Qingcaosha Reservoir increased, driving as well as global climate change and other reasons. The Yangtze River Estuary, from the intertidal zone to the underwater slope the change and evolution trend of such issues should be studied thoroughly. The Yangtze River port beach sediment, sediment, geomorphology observation, Based on the analysis of recent 30 years' chart data, we will discuss the evolution characteristics and influencing factors of beach dynamic sedimentary geomorphology, and provide references for port engineering and future coastal stability protection engineering.
1. North tidal flow showed reciprocating flow characteristics, ebb flow significantly, coastal evolution is mainly controlled by falling trend: from 2004 to 2012, the upper north channel flood season tide rise, the average vertical velocity, sediment concentration decreases continuously, the sediment concentration decreases about 0.2kg/m3; at the same time, the dry season rose, the vertical the average flow velocity, sediment concentration changed, first decrease and then increase the 2007 to 2012 dry season ebb rose, the vertical average concentration increased more than 1 times. Nanhui South Beach at open sea, tidal effect is relatively strong, flood and dry season measured sediment concentration was greater than 1.23kg/m3; from 2004 to 2012. Nanhui South Beach flood season tide rise, the average vertical velocity increases; the vertical average sediment concentration decreases; ebb vertical average concentration increased slightly; the dry season rose, the average vertical velocity and sediment concentration were significantly decreased.
2. in the past 30 years, the Yangtze River beach surface sediment particle size Dso and sediment composition in North thinning, change characteristics of South coarsening, Hengsha East Shoal north of the Yangtze River and the East China Sea Bridge such major project near shallow sediment cores to significantly coarser grain sequence.
3. at present, except the Chongming Dongtan and nine sand, Yangtze Estuary generally narrow, steep slope, most sections outside the beach width in 30-150m, coastal salt marsh vegetation. A few over the past 30 years, South Beach 0m isobath in shallow tidal flat without obvious siltation, Chongming Island Xi to the south coast of Hong Kong Dongtan beach erosion in Nanhui by Om isobath; within 0m isobath tidal mouth slightly siltation, South Beach 0m Isobaths changed little.
4. in the past 30 years, the north shore of North and South segments of the underwater beach profile concave shape characteristics, the steeper slope, part of beach morphology evolution by offshore sand changes significantly; it is worth noting that in 2009 the grass sand levee closure works since the north shore, the overall recovery of sediment pattern. Qingcaosha Reservoir Shore scour by convex front down somewhat, harbour town of Donghai Bridge and below the main erosion occurred along the North Island. Nanhui South Beach underwater slope gradient in recent 30 years significantly increased, beach bottom erosion, -7 ~ -8m deep water erosion under the beach near 1m; -5m water depth in shallow beach. With a net deposition, -5 ~ -6m isobath underwater siltation node; especially since the Nanhui beach reclamation project and the construction of Donghai Bridge, South Beach and coastal erosion. Under the bridge a total, with north as the representative of the "River" water bank under out It has the characteristics of narrow width, steep slope, large interannual variation and obvious slope break, while the tidal flat type underwater beach represented by Nanhui South Beach is characterized by broad and flat shore and stable profile.
The 5. factor impact of recent coastal evolution include reduced sediment basin, different hydrodynamic conditions, the large-scale construction of coastal sand, river channel change and salt marsh vegetation coverage. Watershed sediment is the Yangtze River bank under the sharp slobber slope increases, the global factors affecting the formation of tidal flat deposition rate of slow erosion pattern differences. In view of the hydrodynamic condition, the falling tide master "Jiangan" underwater shoal and tidal action based "tidal" underwater beach development and evolution characteristics of different; and the mouth of the Yangtze River, artificial shoreline under the new situation of coastal hydrodynamic conditions changed significantly, is bound to affect the shape and beach adjust. Circle and offshore engineering is large in the tidal flat area loss, the main reason for local sediment coarsening. Channel sand and salt marsh vegetation changes in the Yangtze River Estuary local beach evolution play an important role Use.

【學位授予單位】：華東師范大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TV148

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