从长江口南汇东滩冲淤变化探讨合理选择促淤造陆边界

随着上海人口与经济的发展，建设用地迅速增加，人-地矛盾越来越尖锐。按相关规划预计，至2010年，上海市建设用地总需求2 267.80 km2，现有建设用地存量2 224.39 km2，未利用的土地仅有9.00 km2，因此围垦造地是上海目前和今后解决人—地矛盾的根本出路所在。河口海岸地区动力条件复杂，地形变化剧烈，如何选择围垦促淤造陆与疏浚促淤造陆边界尤为关键。利用数字高程模型（DEM）和地理信息系统（GIS）研究长江口南汇东滩1996~1999年的冲淤演变规律，结果表明：0.5~1 m高程带为南汇边滩冲淤平衡带，年平均冲刷率为0.007 m/a，在此带以上，滩涂多年的结果表现为淤积，此带以下，滩涂多年的结果表现为冲刷。结合长江口水文泥沙的实测资料分析结果，根据低滩围垦造陆实践和长江口深水航道治理的实际情况，认为长江口低滩围垦促淤造陆和利用工程促淤造陆的边界定在0.5~1 m之间较为合理可靠。

EROSION-DEPOSITION ANALYSIS ON EAST NANHUI TIDAL FLAT OF YANGTZE RIVER ESTUARY AND SCIENTIFIC DECISION BORDERLINE ABOUT ACCELERATING RECLAIM AND MAKING LAND

With the increase of population and development of economy in Shanghai, the demand of land increases rapidly, and the contradiction between human and land becomes more and more badly. The population of Shanghai will be 17.5 million, and the demand of land will be 2 267 km\+2 by 2010.The ultimate way is to accelerate reclaiming of tidal flat and land making,because Shanghai faces three side waters. How to choose reasonably the borderline of accelerating reclaming tideal flat and making land is an important problem of coastal and estuarine engineers. The deposition erosion change of East Nanhui tidal flat of the Yangtze estuary is rationally simulated by DEM(Digital Elevation Model)and GIS(Geography Information System)technology from 1996 to 1999.By Comparing this method with the traditional method of landform analysis, the synthesis method of DEM and GIS is quickly calculated,with less workload and supernal precision.The research results are as following:the 0.5~1 m elevation zone is the balance zone of erosion depostition in Nanhi tidal flat,up that zone,the tidal flat is depositional, down that zone,the tidal flat area is eroded. According to the practical instances deep water river dredge about the Yangtze estuary, and on the basis of the hydrology and suspend sedimentation data of the Yangtze estuary and the land making practice about lower tidal flat,we think that the 0.5~1 m elevation zone is the rational area as borderline about accelerating reclaiming and making land. The research results will provide the theory for the sustaining development of tidal flat resources in Shanghai.