Causes of the Flood in the Downstream Weihe River in Shaanxi Province

The frequent flood in the Weihe River Basin,especially in the downstream area,has influenced seriously the social and economic development of Shaanxi Province.In the paper,the happening mechanism on the flood is discussed through the flood situation of that basin.The results show that the reasons include two aspects:the natural causes and anthropogenic factors,such as the centrality of the precipitation,the runoff including lots of sediment,the building of the Sanmenxia Reservoir and the weak flood-resisting projects.