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11.
By use of bathymetric chart,recent change of the riverbed in the North Passage of the Yangtze Estuary has been studied in this paper.The main channel of the upper,middle and lower(section)in the North Passage has been successively eroded and its groin field significantly deposited.At the same time,sediment has been deposited on the entrance region.Erosion and deposition had responded rapidly to the construction of the regulation engineering.There was about one year duration of lagging between erosion in the deep channel and the construction of the regulation engineering.The siltation lag of time in the groin field varied with the initial depth,but the average deposited thickness was about 0.5 m per year.Volumetric analysis demonstrates that there is a increasing trend of siltation in the North Passage after 2002,because of the difference in duration and quantity between erosion in the deep channel and deposition in the groin field.The water volume of the North Passage was reduced by ≈9%(280 million m3)between 2002 and 2006.Sediment budget reveals that the main sediment deposited in the North Passage takes its source from the river and the ocean.The decreasing water volume was attributable to shoaling in the groin field.Its triggering factors for increased sedimentation are the navigational improvements(jetties and groins)after 1998,which altered the passage boundary and destroyed the equilibrium state on the average ebb and flood sediment fluxes.The establishment of a stable estuary is attributed to a reduction in depth of the groin field.The forecast on the sediment deposition quantity and continuous infilling time in the groin system is about 325×106m3 and 6~7 years,respectively. 相似文献
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有关长江河口治理的几个关键性问题 总被引:1,自引:0,他引:1
长江是我国第一大河,长达6300公里,多年平均入海年迳流量9240亿立米,输出泥沙4.86亿吨。自安徽大通起,长江开始受潮汐影响;从治理角度言,可将徐六泾以下作为河口段(图1)。徐六泾以下河口展宽,其断面宽度为5公里,七丫口断面宽14公里(其中南支宽9.4公里,北支4.6公里),鸭窝沙断面宽26.4公里(其中南港7.2公里,北港8.8公里,北支10.4公里),口门——北岸的寅阳角至南岸的南汇嘴,其宽度90公里。 相似文献
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上海作为中国的大都市是国人所公认的,但还称不上世界大都市,这是因为受上海港深水港区不足等基本条件的限制。在改革开放的今天,继宝钢建设、浦东开发之后,上海还需要做点什么,才能跻身于世界大都市的行列?毫无疑问,扩展上海港是当务之急。 相似文献
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上海市已被列为全国缺水城市之一。这对于长江口、太湖水网地区的一个大都市而言,好象是不可思议的。然而,事实确是如此:丰富的水资源地区,城市给水存在困难,都市进一步发展,水源何在?浦东开发如何供水,已成为上海市民众所关心的问题。1990年10月22日,笔者提出了“干净水源何处寻,长江河口江中求——把长兴岛建设成上海市水源岛的建议”。本文将进一步阐述为,什么把长兴岛至青草沙之间的水域作为上海的水源地?这里的水环境如何?含水质条件、所受盐水入侵影响及对策、取水口附近河槽稳定性如何等问题。 相似文献
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The mouth bar in the Yangtze estuarine waterways has a significant influence on navigational transport within the estuary,flood discharge and construction of the Shanghai Port.In this paper the morphological evolution and mechanisms of mouth bar formation of the Yangtze estuarine waterways are studied by analyzing hundreds of years of historical data and the latest profile maps of some or the main mouth bar channels in the Yangtze Estuary.The results are shown as follows:The mouth bars in the North Branch have moved gradually from outside the mouth to the inside and formed a huge sand bar.In the North Channel,the head of the mouth bar has migrated about 30 kilometers downstream,and a channel bar has been developing since 2001.Two mouth bar tops,which always existed in the North Passage,disappeared in 2010.The head of the mouth bar in the South Passage has migrated downstream about 14 km and the number of tops increased at first but is reduced to only one now.According to the results,we can conclude that the evolution of the mouth bars differs depending on their location.In the North Branch it is directly related to large-scale reclamation in Chongming Island,but in the North Passage it has a close relationship with regulation of the Yangtze Estuary Deepwater Channel.However,the evolution of mouth bars in the North Channel and South Passage is not only connected with the Yangtze Estuary Deepwater Channel Regulation Project,but also with the reclamation in the East Hengsha Shoal and the closure of the Qingcaosha Reservoir. 相似文献
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江泽民同志指出:“开发和利用海洋,对于我国的长远发展将具有越来越重要的意义。”上海临海而兴,在“十五”以及21世纪的发展中,上海要提升城市综合竞争力,需要加强海洋资源和海洋空间的开发与保护,重视海洋产业的培育、升级和发展,使海洋经济对上海的可持续发展作出较大贡献。我们提出十点具体建议:一、明确海洋产业的内涵并建立海洋经济子帐户海洋产业具有相当大的渗透性,要研究海洋产业在上海可持续发展中的作用并推进其发展,需要建立有关海洋经济在上海整个国民经济中的比重、内部结构以及增长率的基础资料和信息。首先,要… 相似文献