Why is waterlogging prevalent in summer in China?

This is caused by the following points: first, there is a lot of rain in summer, especially heavy rain will cause a lot of water in a short time; Second, the drainage system in many cities is not very scientific, and the water after rain cannot flow away in a short time; Third, due to ecological damage, reservoirs and rivers can not be maintained and can not play the role of water storage and water transfer; Fourth, there are more and more extreme weather and uneven rainfall.