The Handy Geography Answer Book. Paul A Tucci

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      The Deep-Ocean Assessment and Reporting of Tsunami (DART) array helps to warn people early of an approaching tsunami.

HURRICANES

      Why are hurricanes so destructive?

      It is the floods caused by hurricanes that are the most destructive element. The low-pressure center of a hurricane causes a mound of water to rise above the surrounding water. This hill of water is pushed by the hurricane’s fierce winds and low pressure onto the land, where it floods coastal communities, causing significant damage. Hurricanes also spark tornadoes that contribute to the devastation.

      How fast do hurricane winds blow?

      The strongest hurricanes, or category 5 hurricanes, often have winds that reach speeds well over 150 miles (240 km) per hour.

      How are hurricanes ranked?

      We use the Saffir-Simpson Hurricane Wind Scale to rank the intensity and destructive capacity of hurricanes. Hurricanes are ranked on a scale of one to five, with category one hurricanes being the weakest and category five being the strongest and most destructive. The rankings for damage caused by each category of hurricane are: 1, minimal; 2, moderate; 3, extensive; 4, extreme (such as Hurricane Andrew in 1992); and 5, catastrophic.

      What was Hurricane Katrina?

      Hurricane Katrina was the name given to the hurricane that developed in the Gulf of Mexico and struck New Orleans and many other cities along the southern coast of the United States in late August 2005. Winds from Katrina were initially only a category two hurricane, with a tidal surge ranked as a category three.

FLOODS

      How many people died as a result of the subsequent failure of the levees and flooding after Hurricane Katrina struck?

      Approximately 1,460 people lost their lives following the landfall of Hurricane Katrina.

       Was the 2005 New Orleans disaster caused by a flood or a hurricane?

      The initial cause of the disaster was Hurricane Katrina, which whipped up tides and forced rain and seawater against a very fragile levee system that protected New Orleans. Since the city is 49% below sea level, when the man-made levees broke, flood waters moved in and inundated much of the city.

      How much precipitation may cause flooding?

      The amount varies widely for different areas. In some U.S. western deserts, or in some large urban areas, just a few minutes of strong rain will cause a flash flood in canyons and low-lying areas, both urban and rural. In areas prone to greater rainfall amounts, it often takes quite a bit more rain (sometimes a few days’ or weeks’ worth) to cause rivers to overflow and dams to fill up, raising concerns of those who live downstream. Areas that normally receive more rainfall have better natural drainage systems and are usually home to plants that readily absorb the extra water.