海平面上升与海滩侵蚀

SEA LEVEL RISE AND BEACH RESPONSE

世纪性的海平面持续上升，加大了海岸水下斜坡深度，逐渐减小波浪对沉溺古海岸的扰动作用而形成海底的横向供沙减少，却加强激浪对上部海滩的冲刷。逐渐上升的海平面，降低了河流坡降而减少了入海沙量。因此世界海滩普遍出现沙量补给匮乏。海平面上升伴随着厄尔尼诺现象与风暴潮频率的增加，水动力加大。这两者的综合效应，使海滩遭受冲刷，沙坝向陆移动。如按ＩＰＣＣ估计，至２１００年海面上升５０ｃｍ时，中国主要旅游海滨的沙滩将损失现有面积的１３％─６６％。主要对策是海岸防护与海滩人工喂养。

It has prevailed that the sea level rise amounted to 10-20cm over the past 100 years. The recent predictions of greenhouse-related sea level rise in the next century vary considerable, but all agree that an acceleration is possible. This process has gradually reduced wave winnowing on submerged coastal sediments. At the same time, erosion on the upper beach by break waves has been enhanced. On the other hand, following the rise of sea level, the slopes of the river beds have been reduced, decreasing the fluvial sediment discharges. The lack of coastal sediment supply is a world-wide phenomenon. Combined with the increasing frequency of ELNino and Storm surge, beach erosion and land ward migration of sand barrier islands are the comprehansive results of adjusting the coastal dynamic balance responsing the century trend of sea level rising.By using the Bruun's model, it is estimated that the major tourist beaches along the China coast zone will lose about 13-66% of their present area while sea level is continully rising to 50cm higher by the year of 2100. Beach protection by building up groin and artificial barrier and beach nourishment are the major methods used under such circumstances.