Assess the relative importance of the impact of primary and secondary hazards caused by hurricanes and tropical storms

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Assess the relative importance of the impact of primary and secondary hazards caused by hurricanes and tropical storms

Hurricanes are one of the most destructive natural hazards in terms of frequency and number of deaths. They are a major threat to coastal areas, especially in densely populated low-lying delta areas, most notably Bangladesh; isolated island groups including the Japanese, Philippine and Caribbean islands and densely populated coast lines such as the Gulf of Mexico. Hurricanes are a multiple hazard since loss of life and property damage result from three main hazards of winds, heavy rainfall and storm surges. As well as these primary hazards often areas are vulnerable to further danger from secondary hazards such as, flooding and contamination of water supplies.

Hazardous processes of all types can have primary, secondary, and tertiary effects. Primary Effects occur as a result of the process itself. To begin with, high winds during hurricanes are a significant primary hazard as wind speeds have been known to be as high as 320km per hour. The strong winds associated with very low atmospheric pressure cause structural damage to buildings, roads, bridges and crops. Both the direct wind pressure and drag tend to propel loose objects at a high velocity. Hurricane Andrew was the second most destructive hurricane in U.S history, striking in August 1992. It swept across the northwestern Bahamas, southern Florida and south-central Louisiana. As a result there were a total of 65 deaths and $26 billion damage, all of these deaths and most of the damage was caused by the wind hazard as buildings collapsed and large debris particles were hurled around.

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Heavy rainfall is another hazard which occurs as a result of a hurricane. Rainfall figures are variable during a hurricane but can be extremely high resulting in secondary hazards such as flooding and landslides. On average hurricanes produce around 100mm per day within 200km of the eye. The largest total rainfall that has been recorded was during Cyclone Denise in 1966 on Reunion Island where 1144mm fell in 12 hours. With reference to Hurricane Mitch of October 1998, the most destructive aspect of this category 5 hurricane was the exceptional amount of rainfall. This was due to the storm’s slow ...

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