我国海岸带主要灾害地质因素及其影响

MAIN GEOLOGICAL HAZARDOUS FACTORS AND INFLUENCES ON CHINA COASTAL ZONE

我国海岸带灾害地质主要有构造、坡地重力、水动力、地下水、岩土与地层结构、海平面上升、地球化学、风力灾害等地质因素,具有复杂、连锁和差异性空间分布的特征.根据验潮资料,近百年来我国海平面上升19～20 cm,上升率为2～3 mm/a.整体以海平面上升为主,但也有岸段下降,主要是山东半岛,平均速率为-0.13 cm/a.预测2050年上升幅度:天津70～100 cm;黄河三角洲40～50 cm;长江三角洲50～70 cm;珠江三角洲40～60 cm.地面沉降大部分是由过量开采地下水引起的.我国96个地面沉降城市和地区中80%在沿海地区,如天津、上海、苏州、常州、无锡、嘉兴、宁波、湛江、台北等.累计沉降量为460～2 780 mm,沉降速率10～56 mm/a.由于地下水的过量开采,20世纪80年代以来,我国辽宁、河北、天津、山东、江苏、上海、广西、海南和台湾等省市,均发生不同程度的海水入侵,给国民经济和社会发展造成重大损失.我国70%砂质海岸和大部分淤泥质海岸发生侵蚀.这种态势始于上世纪50年代,80年代明显加强.海岸侵蚀主要有区域环境变化、河流水利工程拦截泥沙以及海岸人工采沙等因素.

Coastal hazardous geologic factors of China are represented by tectonic, slope, hydrodynamic, groundwater, rock, soil, stratigraphic structure, sea-level rise, geochemical, and wind hazards, which are complicated, chainlike, and different in space distribution. According to tidal data, China's sea level has risen by 19~20 cm since the past 10 ka, with the rising rate of 2~3 mm/a. Generally, the sea level rises, but some coastal sections see the sea level drop. Shandong Peninsula is a representative example. It has an average rate of -0.13 cm/a. From prediction, by 2050, sea level will have risen by 70~100 cm in Tianjin City; 40~50 cm in the Yellow River delta; 50~70 cm in the Yangtze River delta; and 40~60 cm in the Pearl River delta. Ground subsidence generally results from overexploitation of groundwater. 80% of 96 cities that have ground subsidence are located in the coastal areas such as Tianjin, Shanghai, Suzhou, Changzhou, Wuxi, Jiaxing, Ningbo, Zhanjiang, and Taibei. The subsidence amount is accumulated to be 460~2 780 mm, with the subsidence rate of 10~56 mm/a. Since 1980s, due to the overexploitation of groundwater, some provinces and cities of China have suffered from seawater invasion. The seriously attacked areas are Liaoning, Hebei, Tianjin, Shandong, Jiangsu, Shanghai, Guangxi, Hainan, and Taiwan. Seawater invasion has caused great losses to national economy and social development. 70% of sandy coast and most of muddy coast in China suffer erosion. Such situation occurred in 1950s, and became more serious in 1980s. Coastal erosion is mainly caused by regional environmental changes, dams blocking silt discharge and human sand excavation.