6000aBP以来长江下游地区古洪水与气候变化关系初步研究

Relationship between Climate Changes and the Flood Occurrences since 6 000 a BP in the Yangtze River Delta

通过对埋藏古树、泥炭、以及海相贝壳测年资料进行搜集和整理 ,结果表明 :长江下游地区 6 0 0 0aBP以来古洪水的发生与气候变化有着密切的联系 .由于长江下游地区地势低平这一地貌特点 ,使得海面变化对于研究区洪水发生有着重要的影响 ,气候变化导致的海面上升对长江下游河段径流的顶托作用导致河流上溯以及地面排水不畅 ,致使洪水发生频率加大以及洪水危害的程度加强 ,出现“小水大灾”的现象 .长江三角洲地区古洪水发生频率与美洲地区古洪水发生频率的对比研究表明 ,长江三角地区乃至整个长江流域在大的气候变化趋势上与全球其它地区是相似的 ,既有全球气候变化特点的同时又具有区域响应的特点 ,这对于未来研究区洪水发生的预测有着重要意义 .

Comprehensive collection and further study performed on the 14C data materials of buried paleotrees, peat and shell ridges indicate that there exists close relationship between flood occurrences and climate changes in the Yangtze River Delta. The frequent flood periods are corresponding to the climatic transition periods. The study region, characterized by low-altitude geomorphology, is influenced by the high sea level more seriously with flooding events. High sea level causes drainage of surface water during wet climate periods more difficult, leading to more serious inundation and higher frequency of flooding. Comparing the studied results on paleoflood occurrences in the Yangtze River Delta and in the America indicates that the features of climate changes in the Yangtze River Delta, and even in the whole Yangtze drainage basin, are similar to those in other places of the world, but the study region has its own local characteristics of climate changes. Also, it is indicated that there exists close relationship between flooding occurrences and El Nino events. Further study should be made on this relation, which is meaningful practically and theoretically in the future forecast of the flooding events in the region.