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 movement from October 29th to November 3rd and the orographic effects of the Central American mountains. Historic amounts of rainfall in Honduras and Nicaragua were recorded with unofficial reports of up to 75 inches.Deaths due to catastrophic flooding made it the second deadliest Atlantic hurricane in history; nearly 11,000 people were killed with over 8,000 left missing by the end of 1998. The flooding caused extreme damage, estimated at over $5 billion. Additionally, Tropical Storm Alberto (1994) drifted over the Southeast United States and produced torrential rainfall. More than 21 inches of rain fell at Americus, Georgia causing severe floods in which Thirty-three people drowned with damages exceeding $750 million. Therefore, although the primary hazard of rainfall presents significant danger the secondary hazard of flooding in the case of hurricane Mitch caused far more damage and destruction than the initial hazard.
Storm surges also present significant danger causing 90% of deaths from hurricanes and extensive damage to agricultural land by salt contamination from the inflowing sea water. The storm surge results from the piling up of water by wind-driven waves, with their greatest effect on low-lying coasts. However the impact of a surge depends on numerous factors. There are both physical and human variables which play a part in the impact a surge can potentially have on an area. Physical variables such as the height of the tide, wind strength and angle of incidence of the storm are significant when looking at the impact a surge could have. Whereas human variables such as land use, population density and types of building will also be dependable factors. The worst surge recorded in the U.S. this century was the 24-foot-high dome of water that Hurricane Camille pushed into Pass Christian on August 17th, 1969. At least three feet of surge hit places as far as 125 miles east and 31 miles to the west of Pass Christian. It destroyed or seriously damaged more than 18,000 homes and 700 businesses.
However, it is not just the primary hazards that have devastating impacts; secondary impacts are potentially just as damaging causing both loss of life and property damage. Firstly, hurricanes can cause many different types of flooding occurring from torrential rain, storm surges or wind driven water from rivers or estuaries. In the last 30 years inland flooding has been responsible for more than half the deaths associated with hurricanes and tropical storms. Tropical Storm Claudette (1979) brought 45 inches of rain to an area near Alvin, Texas, contributing to more than $600 million in damages. As well as this, Hurricane Agnes (1972) produced floods in the Northeast United States which contributed to 122 deaths and $6.4 billion in damages. Impacts of flooding can be severe at all levels of development although flood impacts do follow the pattern of other hazards, with LEDC’S suffering the most deaths and MEDC’S suffering the highest total economic losses.
Landslides are also a threat during after hurricanes. A landslide is a which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. Although acting on an over steepened slope is the primary reason for a landslide, there are other contributing factors affecting the original . During a hurricane the intense rainfall cause the sol to become saturated creating groundwater pressure which makes the slope unstable. The flooding and landslides in El Salvador from Hurricane Mitch resulted in 374 persons killed and 55,864 displaced.
In conclusion it is evident that both primary and secondary hazards present significant dangers resulting in great impact as a result of hurricanes and tropical storms. However, to assess the relative importance of the impact of primary and secondary hazards is questionable. Firstly, it is clear that the type of hazards that occur is dependent on the characteristics of the hurricane, therefore the impact which takes place will depend upon this. Furthermore, the type of hazards that do occur will all be of importance whether they are primary or secondary because they are all likely to have an impact. Although, it is evident that some hazards present a greater danger and these are mainly the primary hazards such as high winds and storm surges. Nevertheless it is apparent that despite heavy rainfall being a primary hazard the secondary hazard of flooding appears to cause far more damage and destruction than the initial hazard as with the case of Hurricane Mitch and tropical storm Alberto. Therefore, on the whole every hazard whether primary or secondary is of great importance, however certain hazards such as high winds, storm surges and flooding present the greatest danger.