A flood occurs when water pours over dry land. Floods can cause massive damage when they happen unexpectedly.
Heavy rain can cause floods.
If a lot of rain falls quickly, the earth is unable to soak it up, and the water builds up on the ground. When it runs off into the rivers, the rivers overflow their banks. The worst floods happen where the land is flat and low-lying. Mud, earth, and large objects, like cars, can be carried long distances by flood waters. They rip up anything not firmly anchored to the ground.