长江口未来环境演变的若干影响因子及减灾对策

CONTROLLING FACTORS OF CHANGES OF NATURAL ENVIRONMENT AND COUNTERMEASURES IN THE YANGTZE RIVER ESTUARY

三峡水库建成、南水北调逐步实施和沿江抽水加剧将使下一世纪长江入海水沙特征发生重大变化；长江口相对海面在未来１００年中将上升１ｍ左右；全球气温上升将使本区夏季降水增多、台风频率增大。下世纪在这些因素影响下：（１）长江口海岸工程需增加投入约相当于现有工程量的１／２，方能维持现有的安全系数；（２）潮滩湿地将动态损失相当于现有面积的５０％以上；（３）冲刷岸段将增多，淤涨岸段将减少；（４）洪涝威胁将明显加重，需将抽排水能力提高４～５倍；（５）因海面上升引起的特枯季节灾害性海（咸）水入侵则可望通过三峡水库的调节功能得以控制。

The construction of the Three Gorge Reservoir in combination with the progressive practice of the Northward Transfer of Southern Water and the aggravation of pumping water from the Yangtze River will greatly change the characteristics of the Yangtze River water and sediment emptied into the sea in the next century.The relative sea level rise along the estuarine coast will reach about 1 m.The rise of the worldwide temperature will increases the summer rainfall and the frequency of typhoon in the studied area.As the effects of these factors,(a) half as much as the present engineering mass should be added to the coastal structures in order to maintain the safety coeffient;(b) a dynamic loss of about 400 km 2 of wetlands,as much as one half of the present total area,would be caused;(c) erossive shore will increase while accumulative one decrease;(d) to hinder the increase in flood disaster,dynamic capacity for draining water must increase by at least 4～5 times as large as the present;and (e) the disastrous salt water intrusion caused by the sea level rise could be counteracted by the increase in water discharge from the Three Gorge Reservior in the dry season.