A tsunami is a natural geohazard that is almost impossible to prevent from forming or occurring. Though it cannot be prevented, damage from a tsunami can be reduced through sophisticated early warning systems, effective response and community preparedness. The United Nations Environment Program also suggests that tsunamis cause less damage in areas where there are natural tsunami barriers, such as coastal vegetation, coral reefs and mangroves.
Tsunamis are generated by seismic activity, such as earthquakes, volcanic eruptions, underground explosions due to detonation of underground nuclear weapons, and other natural or manmade disasters that can cause disturbance below or above the water. A storm surge, sometimes called a meteotsunami, is often due to deep tropical cyclones, which suddenly raise the water's level above normal.
A timely warning system issues information bulletins and warnings, such as the predicted arrival of the tsunami, to selected communities. Residents of the warned communities are expected to evacuate to higher grounds, such as extremely strong buildings or a multi-story car park. The local government should increase awareness of tsunamis and the risks of living in a low-lying coastal area. Operating a tsunami information system and making it accessible to the public, along with awareness information and education, is essential to be prepared in case of a tsunami. While the effectiveness of tsunami barriers is not well established, tsunami-prone nations, such as India and Bangladesh, have planted coastal trees and mangroves to serve as barriers against future tsunamis.