Tsunamis have a devastating effect on an area that is close to the sea. This effect does not just effect an area of land that is close to the sea, but can also cause devastation for several miles beyond a costal region depending upon the size of the tsunami. Tsunamis thus, create massive amounts of major flash flooding. Tsunamis destroy homes and entire cities. Tsunamis can cause deaths of people caught in their wrath. They can wipe out entire civilizations if bad enough.