Rainfall is vital to life on Earth and either too much or too little can have devastating impacts on both the environment and on human life. Floods and droughts are normal aspects of the Earth’s climate, but human activity modifying drainage or irrigation can have a strong influence locally.
Excess rainfall in a river catchment area is one common cause of flooding. Rivers have always flooded, but increased development in the catchment area can exacerbate the problem. This video demonstrates some of the issues in building on flood plains and in catchment areas, using a model which you might like to reproduce at home.