Yes, they do. Rivers often overflow their banks and flood the land around them. This can happen when there has been a lot of rain or a lot of snow has melted in the mountain where the river starts its journey. Floods are often very destructive. They can damage crops and houses and kill people. But in the long run they can also do some good. They bring fresh soil down the river and spread it on the flooded land. Egyptian farmers have been dependent on the annual flooding of the Nile for thousands of years. The Amazon and the Ganges rivers regularly bring fertile soil to the agricultural areas downstream.