There are a variety of floods. There are river floods, seacoast floods, and flash floods. Floods may be helping or harmful.
A big flood in Rapid City, South Dakota killed 238 people in 1972. The Huang He in China floods its banks. It is also known as the Yellow River. The Nile River has yearly floods.
A flood occurs when water rises over its normal level. Some people have built levees or dikes to prevent river floods.