Flooding occurs when water overflows onto ground that is dry in normal conditions. Flooding can occur on low-lying coasts as a result of extreme weather, such as cyclones or tsunamis, which causes water to surge onto land. Another common cause of flooding involves rivers or streams overflowing after excessive rain, landslides, a burst dam or levee or rapidly melting ice in the mountains, according to the Natural Disasters Association.
There can be benefits to natural flooding, because it can create fertile areas by moving deposits that are rich in nutrients onto agricultural land, such as the Mississippi Valley. However, severe flooding can be disastrous, as in the case of the Mississippi flood of 1993. That flood, caused by abnormal levels of rainfall that inundated the river, resulted in destroyed infrastructure and displaced people.
Heavy precipitation during the monsoon season in Bangladesh makes it the country most vulnerable to flooding in the world. In 1998, flooding lasted for two months and impacted two-thirds of the land in Bangladesh. The Yellow River Valley in China also experiences significant floods that cause loss of life.Learn more about Storms