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(1) Causes of flood disaster 1, natural causes A, characteristics of water system: there are many tributaries of water system (fan-shaped water system and dendritic water system); River bend (Jingjiang reach); Lack of natural rivers flowing into the sea (Huaihe River); Low-lying (Haihe River, Pearl River). B, hydrological characteristics: there are many rainstorms in summer, and the river surges. C. Climate characteristics: the precipitation lasts for a long time and is concentrated (such as rainy weather in the Yangtze River basin); The change of summer monsoon intensity (the second highest intensity: drought in the south and waterlogging in the north; Weak subtropical high: waterlogging in the south and drought in the north); The influence of typhoon; El Nino phenomenon, etc. 2. Deforestation caused by man-made causes has aggravated soil erosion and raised the riverbed; Reclamation around the lake weakens the regulation ability of the lake; Unreasonable water conservancy project construction (Weihe River Basin) and other human factors will cause floods. (2) The difference between rainstorm and flood disaster: rainstorm does not necessarily cause flood, but flood must be caused by rain.