Flood, tsunami, landslide

Floods, tsunamis and landslides are all forms of natural/environmental events. Floods are volumes of water that overflow parts or large segments of land and include river-, coastal-, and flash floods. These can be caused by heavy rainfall, melting snow, heavy winds, high tides or a breaking dam for instance. Tsunamis are multiple series of waves, caused by large displacements of water (usually in lakes or oceans), which are in turn caused by for example an earthquake. Landslides are large displacements of mass (such as rock, mud or debris) caused by natural (such as earthquakes) or unnatural (such as road maintenance) events, that fall down slopes, hills or mountains. Slope stability and gravity are important factors for landslides to occur.

A flood can lead to polluted or destroyed wildlife habitats, damaged property and endangers lives. Traffic may be delayed or impossible, it may interfere with drainage and use of farmland, and lead to big financial losses. Floods can be controlled by planting vegetation to retain extra water, terracing hillsides to slow flow downhill, construct floodways to divert water, create lakes, dams and reservoirs to retain surplus water. Tsunamis cause damage by the smashing force of a wall of water travelling at high speed, and the destructive power of a large volume of water draining off the land and carrying a large amount of debris with it. Currenly tsunamis cannot be precisely predicted, nonetheless there are some warning signs of an impending tsunami, and automated systems can provide warnings immediately after an earthquake in time to save lives. One of the most successful systems uses bottom pressure sensors, combined with computer models and sirens to infrom the public. Some countries place tsunami walls to stop waves and protect the public. Landslides produce a debris flow or mud flow (and even rock avalanche) that can damage any property in its way and lead to river blockages, flooding and tsunamis. Landslides can be predicted by landslide hazard analysis, decision support systems and remote sensing, including use of aerial photographs and satellite imagery. It can be countered by adjusting the slope of a hill, reduce the amount of water in the ground (drainage) or strengthening the slope itself with chemical and mechanical methods (reinforcement). 

Related keywords: landslip, rockfalls, deep-seated slope failures, erosion, mudflows, debris flows, inland floods, storm surge, tidal wave, seismic sea wave, man-made tsunami