A natural disaster is a catastrophic event that takes a severe toll on the human populace in terms of environmental, financial or mortality losses. Natural disasters fall into several main categories. Geological disasters are earthquakes, volcanic eruptions, avalanches and sink holes. Hydrological disasters include floods, tsunamis, tidal waves and, very rarely, limnic eruptions. Meteorological disasters are comprised of hurricanes, tornadoes, hailstorms, blizzards, and droughts. Other natural disasters may include wildfires, epidemics, solar flares and meteoroid showers.
An earthquake is the sudden release of seismic energy within the planet's crust resulting in large magnitude geological shaking and land eruption. The greatest risk reduction for an earthquake is preparation: earthquake engineering, earthquake preparedness and earthquake prediction. Earthquake engineering is the minimalization of seismic risk through mechanical and civil engineering, earthquake preparedness is the emergency management and evacuation plan of a region and earthquake prediction is the use of geological and seismic measures to forecast the approximate time and particular place an earthquake is likely to occur.
An avalanche is a unpredicted and rapid flow of snow down an incline that occurs whenever a manmade or natural activity triggers the snow pack past its critical point. There are a number of precautionary measures for preventing avalanches. In addition to ski advisories and artificial barriers to guide the flow of snow, safety administrators also use controlled detonations to set off smaller avalanches in order to break up heavy snow accumulations into more manageable fragments.
Floods are inundations of water in places normally covered by dry land. Ninety percent of all natural disasters in the United States are flood-related. In some areas prone to flooding, the government has offered monetary assistance to residents in order to rebuild damaged homes at higher planes. The National Science Foundation has conducted studies that indicate a great need for preparedness and prevention: dam construction, sea walls, levees, tide gates and barrier islands.
A tsunami is a sequence of high-powered water waves caused by displacement of a large volume of water. The geologic shift can result from earthquakes, volcanic eruptions as well as underwater explosions and landslides. A number of prediction systems have been put in place to warn residents of a pending tsunami as well as evacuation routes to lead residents from dangerous areas.
Hurricanes or tropical cyclones are inward spiraling storm systems that have a low-pressure center, or "eye," and intense rain and wind velocities (between 75 and 155 miles per hour with gusts up to 200 miles per hour) around its perimeter. Hurricanes result when saturated air rises from a large body of water. The mass of air is energized by changes in temperature from heat of condensation, usually brought on by solar heating and deep convection. Doppler weather radar and satellite-based tracking systems can predict the position and strength of hurricanes. Forecasting and evacuation alerts have been the major form of precautionary measure in preventing loss of human life.
During several decades, escalating costs have been associated with natural disasters, despite improved forecasting and preventive measures. Some of this is attributed to increased migration to coastal areas, which make populations worldwide at increased risk to many of the hazards associated with these events. According to the National Oceanic and Atmospheric Administration (NOAA), in the United States, more than half of the American population lives within 50 miles of the coast. These high densities of population not only put a large amount of people at risk, but also place a large amount of stress on the environment in these areas.
Natural disaster risk reduction is a global effort to implement observation, measurement, monitoring, forecasting and warning procedures with the singular intent to preserve human life and critical infrastructure. Well-known organizations in the United States involved with disaster response programs include the Centers for Disease Control (CDC) and the Federal Emergency Management Agency (FEMA). Globally, organizations that operate disaster risk-reduction programs include the World Meteorological Organization (WMO) and the World Health Organization (WHO). According to Eric Schwartz, the U.N. Secretary General's Deputy Special Envoy for Tsunami Recovery, as reported in The Boston Globe (1996), virtually every dollar spent on natural disaster risk reduction yields a 5- to 10-fold savings in disaster losses. Only 4 percent of the the annual $10 billion in humanitarian assistance, however, currently goes to preventive measures.