What is the reason of flood?

Excessive rain cause flood because due to it the rivers become overflow and due to lack of infrastructure the water takes an enormous face. Cloud burst also cause flood as sudden water is impossible to manage and due to which it is causing huge destruction. The melting of glaciers brings excessive water into the rivers which causes a flood. Also due to lack of development, the water is unable to stop or controlled and thousands of people die every year from floods and thousands of people migrate.