Climate Background of Flooding and Waterlogging and Disaste Inducing Factors of the Yangtze Valley
长江流域洪涝气候背景和致灾因子分析

The Yangtze Valley is rich in resources and culture. Yet the frequennt torrential rainfall made the Yangtze a flood river, frequently causing serious floods. Therefore, it is of great importance to analyze the rule of precipitation and climate change of the valley for deep understanding of flood formtion and correct prediction. The precipitation characteristics in flood season and climate change in the past 50 years in the Yangtze Valley were studied. In addition, the impacts of physical geography, hydrologic factors and unadvisable human activities on flood formation were analysed by taking severe 1998 flood as an example. The results indicated that: 1) climate tended to be warmer in flood season, and both variation and frequency of positive precipitation anomaly increased; 2) days of torrential rain in the flood season tended to increase slightly since the 1980s, and showed a cycle of 2 to 3 or 5 years; 3) the spatial and temporal distribution of torrential rain in this valley is in favor of flood formation and disadvantageous to flood defence; and 4) though the cycling and annual variations of precipitation are the main factors leading to floods, the severe eco environmental deterioration resulting from unadvisable human activities in the past 50 years also played a very important role in flood formation.