摘要
在分析1950年以来系列监测资料的基础上，对今后20年长江入海泥沙量和口门区5m等深线以浅滩涂的冲淤趋势作了初步估计，结果表明：（1）人类活动巳导致长江入海泥沙通量减少约2／3。大通站输沙率从20世纪60年代后期开始出现趋势性下降，尤其是80年代后期以来输沙率下降加快。1996～2005年的输沙率（2．80亿t／a）比1956～1965年的输沙率（5．04亿t／a）下降了2．04亿t／a，降幅达44％；三峡水库蓄水后的2003～2005年大通站输沙率（1．89亿t／a）比1956～1965年降低63％。（2）滩涂淤涨速率明显下降。河口口门区4大滩涂（崇明东滩、横沙东滩、九段沙和南汇东滩）的合计淤涨速率在1958～1977年、1977～1996年和1996～2004年3个时段分别为19．1、5．1和4．9km^2／a。（3）目前上海5m等深线以上的滩涂面积主要分布在口门4大滩涂，它们分别是崇明东滩（701km^2。）、横沙东滩（464km^2）、九段沙（410km^2）和南汇东滩（462km^2），占总面积的80％。（4）考虑北槽深水航道工程的影响后得出，大通站输沙率（10^8t／a）和口门区4大滩涂淤涨速率（km^2／a）之间的关系为Y=9．51X=29．1，r=0．925。预测表明：2006～2015年和2016～2025年时段大通站平均输沙率估计将分别降至1．5和1．2亿t／a左右。根据上述关系，2006～2015年和2016～2025年时段口门4大滩涂5m．等深线以上面积将分别蚀退148和177km^2，即20年累计损失占现有面积的13．8％。在现有工程条件下，今后20年口门的4大滩涂5m等深线以上的面积累计损失可能为10％左右。因此，作为上海滩涂资源主要来源的长江口门区滩涂淤涨速率在自然条件下随着长江入海泥沙的减少而迅速下降，若无有效的工程保护措施，今后随着长江来沙的进一步降低将出现净的蚀退。采取适当的工程促淤措施，利用高悬沙浓度的有利条件，上海仍可望获得新的滩涂，以实现滩涂资源的可持续利用。
About 15% of the land needed for Shanghai＇s urban development came from the reclamation of the tidal flat of the Changjiang River delta over the last 50 years. Further reclamation is needed for Shanghai＇s urban expansion. However, due to damming, sand extraction and afforestation in the Changjiang River basin, there has been a decreasing trend for the riverine sediment into the East China Sea since 1960 s, which presents a threat to the source of the tidal flats for Shanghai that needs to be further examined. Based on the analysis of the series monitoring data since 1950, the amount of the riverine sediment delivery into the East China Sea and the general scour and silting trend at the outlet （shallower than 5 m isobath） of the Changjiang River Estuary in the next 20 years is estimated. The results show that： （1） The riverine sediment has greatly decreased by two thirds due to anthropogenic activities. The sediment load at the Datong Gauging Station has shown a decreasing trend since the late 1960s and it has been accelerated since the late 1980 s. The sediment discharge in the past 10 years （averaging 2.8 × 108 t/a） is only about 44% of that between 1956 and 1965 （averaging 5.04 ＊ 10^8 t/a）. （2） The progradation rate of the tidal flats has been decreasing evidently. The combined progradation rate of East Chongming Shoal, East Hengsha Shoal, Jiuduansha, and East Nanhui Shoal was 19.1 km2/a between 1958 and 1977, 5.1 km2/a between 1977 and 1986, and 4.9 km2/a between 1996 to 2004. （3） Thearea of the tidal wetlands above 5 m isobath at the outlet accounts for 70% of the total, in which East Chongming Shoal is 701 km2, East Hengsha Shoal 464 km2, Jiuduansha, 410 km2 and East Nanhui Shoal 462 km2. （4） There is a linear correlation between the sediment load （108 t/a） at the Datong Gauging Station after taking the impact of the dredging activity in the North Passage into consideration and the progradation rate of the tidal wetlands （km2/a） at the outlet, that is, Y=9. 5136X-29.05, R=0. 925. Based on these results, it can be predicated that the sediment load at Datong will decrease to 1.5×108 t/a between 2006 and 2015 and 1.2×10^8 t/a between 2016 and 2025. As a result, the tidal wetlands near the Changjiang River mouth may be eroded by 147.8 km2 between 2006 and 2015 and by 176.3 km2 between 2016 and 2025, which is about 6.3% and 7.5% of the present tidal wetlands respectively. The current Deep Waterway Project in the North Passage and the reclamation project at the East Hensha Shoal may hinder erosion in the future. If there are no further engineering protection measures to be taken, there will be a 10 G loss of total tidal wetland area in the next 20 years. The conclusion is as follows： due to the decrease in sediment load from the Changjiang River, the progradation rate of the tidal wetlands in the Changjiang River mouth has been decreasing and the tidal wetlands may be eroded in the future if there are no engineering protection measures to be taken. But the submerged delta may provide a source for sediment via resuspension resulted from flood tide erosion. If suitable measures are adopted to utilize the high suspended sediment concentration, Shanghai is expected to have new tidal wetlands for urban development. Further protection of the tidal wetlands and reclamation under high suspended sediment condition will secure the existing tidal wetlands resource and provide land for Shanghai＇s urban expansion.
出处
《海洋学研究》
2009年第2期7-15,共9页
Journal of Marine Sciences
基金
上海市科委重大资助项目(07DJ14003-01)
国家科技部重点实验室专项课题资助项目(2008KYYW01)
国家自然科学基金资助项目(40721004,40576043)
国家海洋公益资助项目(200705020)
关键词
滩涂
河流供沙
可持续利用
长江口
上海
coastal wetland riverine sediment supply sustainable utilization Changjiang River Estuary Shanghai
