21世纪中叶天津沿海地区极端高水位趋势预测

据统计,天津沿海地区50年一遇的风暴潮极端增水水位为 4.092m,开展控沉工作后的地面下沉速率约为15mm/a,目前沿岸海挡顶面高程一般为 4.332m.参考孟加拉湾、伦敦、汉堡等沿海地区在2050年海平面上升(取较今高约0.2m的推测值)背景下的极端增水趋势预测(增加0.5m),推测天津沿海地区2050年的极端高水位将增加到 4.792m(4.092m 0.2m 0.5m),现有海挡顶面高程将下沉至 3.687m(以2007年为起算年份).2050年极端高水位将比届时的海挡顶面高1.105m,由此将加重风暴潮水漫溢致灾的危险.如果再考虑波浪叠加、河口效应、极端海面上升等不确定因素的影响,危险将更加严重.

Trend prediction of extreme high water levels in the coastal area of Tianjin, China in the middle of the 21st century

According to the available statistic data, the 1-in-50-year extreme water level (ewl) caused by storm tides was +4.092 m in the coastal area of Tianjin. The land subsidence rate is ~15 mm/a after the land subsidence is controlled. Now the elevation of the top of the coastal levee is +4.332 m above sea level in general. Following the 0.2m increasing of the projected sea-level-rise, adding extra 0.5m in Bengal Bay, London and Hamburger etc. in 2050 for the extreme high water, we forecast the local ewl will be increased to +4.792m (4.092m+0.2m+0.5m) in the area in 2050, while the top of levee will be sunk to +3.687m at that time (with the starting year of 2007). As a result, the predicted ewl will be 1.105 m higher than the sunk tops of levees in 2050. This will increase the risk of the flooding of storm tide water and occurrence of a disaster. This risk will be even graver in consideration of the influences of a number of uncertain factors such as wave superposition, estuarine effect and extreme sea level rise.