2. Biological reasons: due to the rapid economic development in southeast China, many land areas have been converted into urban construction land, and the existence of deforestation has reduced the degree of water conservation of plants and reduced the role of delaying precipitation;
3. Engineering factors: excessive logging in the upper reaches of the river makes a lot of sediment enter the river, the riverbed rises, the water capacity of the river decreases, and the water level tends to rise in flood season. In addition, it is not excluded that the quality of some water conservancy facilities is not up to standard, and managers do not grasp the timing of flood discharge and drainage;
4. Topographic reasons: The summer rainfall in China is generally the whole basin rainfall, with heavy rainfall, and the rainwater from the upstream directly flows into the downstream, further aggravating the flood risk in the downstream area;
In addition, the drought in the south is actually in Yunnan-Guizhou area, which is less affected by the southeast monsoon. Her precipitation mainly comes from the southwest monsoon of the Indian Ocean. Now the flood in the south actually refers to the south of China.