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A Revision Guide For A Section Of The Hazardous Earth Unit

Home > Study Notes > A Revision Guide For A Section Of The Hazardous Earth Unit
Published in: Science
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The revision guide focuses on tropical storms.

Phil H / Abu Dhabi

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  1. Hurricanes (typhoons, cyclones, tropical storms) Hurricanes: A hurricane is a large low pressure system characterised by high winds and heavy rain. Hurricanes are also known as typhoons in East and South-east Asia and cyclones around the Indian Ocean. To be classified as a hurricane, winds must exceed 119km/hr (74 mph). Small low pressure systems are called tropical storms (63-118km/hr) and tropical depressions (0-62km/hr). Distribution of Hurricanes Hurricanes mainly between are found the tropics. Because hurricanes obtain their energy from the sea, they are found in coastal areas. 300 The main hurricane hotspots are: C i MSS • rRoprcÉL DEPR CRTE60Rr 1 CRTESORr 3 -tfiTü0nr CFTESORr Index OOUTC zoaystpoa'D1; OüUTC 3: zooyssposjn: 15: OOUTC OOUTC 7: zßüystpoa,'aa: OOUTG OOUTC 3: '*5: OOIJTC üOUTC eat MONTAGE or-- 1 URN Robinson Projection The Caribbean, Central America and Southern US SE and E Asia e.g. Japan, China, Indonesia and the Philippines Northern Australia Bay of Bengal e.g. India and Sri Lanka East Africa and the Southern Arabian Peninsula e.g. Oman and Kenya. UbJ„CIMSS It is possible for hurricanes to form and travel from these main locations but it happens very rarely.
  2. Hurricane Formation and Location of Hurricanes Hurricanes are intense low pressure systems that develop over warm tropical seas. Because hurricanes form at sea and are extremely dangerous, there development is not fully understood. What is known is that they gain their energy from warm water. The conditions needed for hurricanes to develop are: 1. Warm waters. At least 27 degrees centigrade to a depth of 60 metres. 2. The low pressure has to be sufficiently further enough away from the equator for the Coriolis force to create a hurricanes circular motion. 3. There has to be low pressure systems (depressions) that have the potential to grow. Less than 10% of tropical disturbances turn into hurricanes. Hurricanes can turn into massive systems up to 800km wide, but the intense storm around the eye rarely exceeds 300km. Because hurricanes need warm water to develop they normally occur towards the end of the summer. Hurricanes are associated with very intense winds and heavy rainfall. The winds are generated by the difference in pressure between the eye (very low pressure) and the edge of hurricane (higher pressure). The high winds and heavy rainfall can also create a number of secondary hazards like storm surges, flooding and landlsides. Because of the conditions needed for storms to develop (warm seas) it means that storms are only found in warm tropical areas - ideally over warm shallow seas like the Caribbean. Once hurricanes hit land, they lose their source of energy and lose their strength very quickly. Hurricane Hazards and Key Words • The Eye: The centre of a hurricane is called the eye. As the eye moves overhead conditions can turn temporarily calm. Landfall: The location that the storm hits the coast (land). Formation: The location a hurricane is created. • Dissipation: Where a hurricane breaks up and loses strength. Primary Hazards Wind: Hurricanes are associated with strong winds. To be classified as a hurricane wind speed has to exceed 74mph (119 km/hr) Rain: Because hurricanes suck up large amount of energy and moisture from the sea, they are associated with intense rainfall, up to 500mm in 24hours. Secondary Hazards Landslides: Because hurricanes bring very intense rainfall, they can cause hillsides to become saturated very quickly increasing the stress on them and the likelihood of landslides. Flooding: The intense rainfall can also cause severe flooding. The rainfall may also be combined with a storm surge making the flooding worse. Storm Surges and Heavy Seas: Because of the friction between the wind and the surface of the water, large waves can be created. Also the hurricane can literally drag water in land, causing coastal flooding. Storm surges can be especially bad if they coincide with high tides (especially spring tides).
  3. Diseases: Conditions such as Malaria, Cholera and Typhoid can spread if stagnant water is left and things start to rot. This can become a major issue if there are not enough medical supplies. Predicting and Measuring Hurricanes Because hurricanes form at sea, meteorologists do have the chance to try and predict the movement of hurricanes (track hurricanes). However, hurricanes are enormously unpredictable an calculated courses can vary by hundreds of kilometers. Therefore even though stretches of coastlines can be put on general warnings, the exact landfall may not be known until 12 hours prior. This short period gives authorities and residents a much shorter time to evacuate. The National Hurricane Centre in the US predicts and tracks storms in the Caribbean region. You can look at current storms on their website: National Hurricane Center Hurricanes are normally measured by using the Saffir-Simpson Hurricane Scale developed by the National Oceanic and Atmospheric Administration. Hurricanes are measured on a scale of 1-5 depending on their wind speed and storm surge. However, it must be noted that category five storms don't always cause the most damage. The amount of damage caused by hurricanes can depend on a number of factors including: Where landfall is (populated or non-populated area) The development of the country The warning given to residents and the preparedness of residents. The existing conditions (saturated ground or not) The timing of landfall (high tide or low tide) However, even developed countries like the USA can suffer massive damage. Hurricane Katrina which was category 5 caused widespread damage and loss of life despite warning and defences.
  4. Comparing Storms Dates Location Magnitude Deaths and injuries Cyclone Nargis Formed: April 27th 2008 Landfall: May 2nd 2008 Dissipated: May 3rd 2008 Hurricane Katrina Formed: August 23rd 2005 Landfall: August 25th 2005 (South Florida) and August 29th New Orleans Dissipated: August 30th 2005 Cyclone Nargis formed in the middle of Hurricane Katrina formed as a tropical the Bay of Bengal. It then tracked west depression near the Bahamas. It then towards India before turning north east tracked west crossing the southern tip of and tracking straight to the Irrawaddy delta in Burma. Category 4 135mph (215kph) Pressure 962 millibars 138,366 deaths (many believe the figure was under-reported) 20,000 - 50,000 injured Up to 3.2 million homeless Economic Loss $10 billion (Nearly 53.5% of GNI based Florida before veering north and hit Louisiana. Category 5 175 mph (280kph) Pressure: 902 millibars 1,833 deaths 5,000 treated at emergency triage centre in airport (injured) Estimated 12,000 made homeless in New Orleans $108 billion (0.83% of GNI based on 2005 figures) 70,000 jobs lost (estimate based on unemployment rise) from cyclone/hurricane Population Population indicators on 2008 figures) Farming sector devastated Population: 49.2 million (2008 figures) Population: 296.5 million (2005 figures) Population density: Between 70 and 75 per km2 Life expectancy: 62 Birth rates: 19 Death rates: 10 Fertility rate: 2.2 Population density: 80 per km2 Life expectancy: 78 Birth rates: 14 Death rates: 8 Fertility rate: 2
  5. Economic Indicators Transport and Communications Education and healthcare Aid Total GNI: GNI per capita: $379.6 % below absolute poverty line of $2: Data not released % of internet users: 0.22% % of telephone users: 1.25% (cell phones and landlines) Motor vehicles per 1000 people: 7 Amount of paved roads: 27,000km Adult literacy: 84.7% Primary enrollment: 98.5% University enrollment: Data not released Doctors per 1000 of population: 0.36 Healthcare expenditure per capita: $4.5 Infant mortality: 68.78 Government initially declined aid. First aid flights arrived on 7th May but rescuers found it hard to obtain visas. UK biggest single donor with about $33.5 million. The UN requested a total of $841 million in aid to help victims, but only about $190 million was ever collected from donor countries. Total GNI: GNI per capita: $43,551 % below absolute poverty line of $2: 0% % of internet users: 78.2% % of telephone users: 73% own cell phones (2005) Motor vehicles per 1000 people: 819 Amount of paved roads: 4,148,395 km Adult literacy: 99% Primary enrollment: 98.5% University enrollment: 72.6% Doctors per 1000 of population: 2.3 Healthcare expenditure per capita: $6,096.2 Infant mortality: 6.81 US also delayed asking for international help. Officially they asked the EU for help one week after the disaster. Most relief is in the form of assistance e.g. tents, food, blankets and not money. Cuba did offer to send over 1,500 doctors, but this offer was declined. In total it is estimated $854 million in aid was offered, but up to half was never taken. N.B. All data comes from www.nationmaster.com www.wikipedia.com or http://unstats.un.org. For the US I have used the nearest available data to 2005 and for Myanmar the nearest available data to 2008. In terms of magnitude Hurricane Katrina (category 5) was actually slightly stronger than Cyclone Nargis (category 4). However, in terms of deaths and damage Cyclone Nargis was actually far more devastating. The information in the table is statistical evidence that helps support some of the reasons below of why Nargis was more devastating than Katrina: Education: Even though levels of primary enrollment are the same in the US and Myanmar, the overall literacy rates are much higher in the US. It is not only important to be able to read and write so that you can understand the risks posed by hazards and how to minimise the risks, but it is also important that as a population you are educated about hazards by the government. The US local and national government is good at educating its citizens about how to prepare and react to natural disasters. They education people in terms of evacuation plans and also educate rescuers on how to save lives and rescue people. Transport: Car ownership is much high in the US than Myanmar (over 100 times higher). The US also has a much more extensive road network. In fact in the Irrawaddy Delta where Nargis hit there are
  6. virtually no roads and the main form of transport is by boat. The US also has a much bigger air network with established airlines like United, Delta, Continental and American. This means that people in the US were much better able to evacuate the oncoming hurricane and also rescue teams were more easily able to reach victims, thus reducing the overall number of casualties. It also allows water, food, tents, medical supplies to reach affected areas. In times of flooding helicopters are also important - the US who spends more money on its army than any other country in the world has an abundance of helicopters. Communications: Internet and phone usage is extremely low is Myanmar, where they are both over 70% in the US. Good communications are vital in reducing casualties because it allows people to receive warnings and updates of approaching hazards as well as call for help if they have been impacted by hazards. Again the Irrawaddy Delta is very remote and will probably have even lower internet and phone ownership than the rest of Myanmar. Healthcare: The US spends a lot more money on its healthcare than Myanmar and has significantly more doctors per person than Myanmar. Therefore it is in a much better position to treat victims of natural disasters and in a better position to reduce many of the secondary hazards like disease common with natural disasters like Nargis and Katrina. Level of Development: The US is an MEDC and has the largest economy in the world. Myanmar is considered by most to still to be an LEDC. Because of the US's level of development it has much more money to prepare for natural hazards and a lot of money to recover from them. Countries like Myanmar often become reliant on aid in times of natural disasters - something that they were actually slow to accept. Aid: Both countries were slow to accept aid and the US even declined aid including the offer of over 1500 doctors from Cuba. However, Myanmar's delay in accepting aid and actually declining visas to maid aid workers was much more significant because they were much less able to help themselves. By not accepting aid more victims would have died because of their initial injuries and more people would have suffered from secondary hazards like exposure and disease. Building Design: Most people living in the Irrawaddy Delta are poor farmers and fishermen who nearly all live in temporary structures made out of things like plastic, wood and reeds which are unable to withstand the strong winds and rain associated with cyclones. On the other hand the US has strict guidelines about building regulations and although many buildings did flood in New Orleans most stood up to the winds associated with Katrina. Defences: Even though many of the levees protecting New Orleans failed and caused significant flooding, there were actually many other levees and coastal defences that held and reduced the impact of the hurricane. In the flat Irrawaddy Delta there were virtually no defences and even many of the regions natural defences like mangroves had been removed making the region more vulnerable and increasing the number of victims. Insurance: Most people and businesses will have insurance in the US. This means that they can afford to live in temporary accommodation if their house has been damaged and afford for totally to be repaired. Businesses can also claim for lost income and repair any damage. This means that people are able to recover much quicker and are less likely to suffer from secondary hazards and future primary hazards. In the Irrawaddy Delta in Myanmar most people would never of heard of
  7. insurance, let alone have it, meaning that they have to rebuild their houses from temporary materials and will lose significant income which may lead to secondary hazards like famine, exposure and disease. So even though the Hurricane Katrina was one of the US's worst ever natural disasters, its impacts were not as great as Cyclone Nargis because of peoples education and the country's transport, communications and healthcare networks as well as the US's higher level of development and more stringent building regulations and defences.

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