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Tropical Cyclones Case Studies: Cyclone Heta, Niue, 2004 Cyclone Zoe, Solomon Islands, 2002 Cyclone Kina, Fiji, 1993 Processes that produce tropical cyclones The development of a cyclone is called cyclogenesis and occurs in the following way: 1. The ocean is heated to 27◦C by the overhead sun (between November and April). This causes warm moist air to rise and to condense into clouds. 2. As surface air rises a low pressure cell forms along the South Pacific Convergence Zone (SPCZ), drawing in the surrounding warm air. 3. The rising air spins clockwise due to the Coriolis Effect that deflects winds. Huge storm clouds form. 4. A jet stream or jet streams suck air from the top of the cyclone causing air to rush into the system even faster, speeding the cyclone’s development. Cyclone Heta – jet stream present that had a vacuum effect. Sequence of events in a tropical cyclone Before the tropical cyclone: - Pressure falls and wind speeds increase dramatically. Cyclone Zoe – pressure fell to 900hPa - Cyclone warning and preparations: windows are boarded by, roofs are secured, schools and businesses close, ripe fruit is picked, animals and boats are brought in. Cyclone Heta – cyclone alert issued the day before. Workers went home to secure houses. Boats were lifted out of the water and the airport was closed. During the tropical cyclone: - Torrential rain, hurricane force winds and storm surge cause severe damage to any thing in the cyclones path. Cyclone Heta – 200mm rain, winds exceeding 250km/h, 4-7m high storm surge. Cyclone Zoe – 1m storm surge, 350km/h winds - People take shelter. They usually shelter in the strongest buildings and in the highlands (mountains). Cyclone Zoe – people fled to mountain shelters - Deaths and injuries: mainly due to drowning, being hit by flying debris or crushed by collapsed buildings. Cyclone Heta – one person killed. Cyclone Kina – 22 people died either drowning or hit by flying debris. - Widespread destruction: business buildings, homes, schools and community buildings are destroyed. Cyclone Heta – Hotel Niue destroyed, phone system and homes destroyed. Cyclone Kina – homes had roofs blown off, no water, electricity or communications, three major bridges destroyed. After the tropical cyclone: - Emergency response: search and rescue, evacuations, etc. Cyclone Heta – evacuation centres were set up for those who had to leave their homes. Cyclone Zoe – survivors had to wait more than a week for help to arrive by sea. - Clean-up and Assessment: the clean up begins, overseas aid comes in, temporary shelters are set up and essential services are restored. Cyclone Heta – New Zealand gave $5 million. New Zealand and Australian aid workers went to Niue to help. Cyclone Kina – New Zealand sent 200 tents and emergency supplies. - Repair and Reconstruction: there is a decrease in tourism, new crops are planted (only subsistence at this stage), income is lost and rebuilding starts. Cyclone Heta – slowly reestablished the coconut and fruit tree plantations, loss of income from expected 2700 tourists. Cyclone Kina – some damaged hotels on the Coral Coast were forced to close. - Recovery: repairs to infrastructure, planning for reducing the effects of tropical cyclones in the future and life goes on – tropical cyclones are a part of Pacific life. Cyclone Heta – capital, Alofi, relocated to the centre of the island. Cyclone Kina – 3 major bridges took 6 months to rebuild. Effects of a tropical cyclone on the land - - - - Coastal erosion: storm surges alter the shape of the island and can destroy or change the shape of coral reefs. Cyclone Heta – shape of the sea cliffs and the coral reef changed. Flooding: low lying areas are flooded by storm surge, rainfall or rivers. Cyclone Heta – flooding occurred in coastal areas. Washed away top soil. Cyclone Kina – there was widespread flooding due to the heavy rainfall. Landslides: occur on steep and unstable slopes as a result of heavy rainfall. Cyclone Kina – landslides occurred in inland areas. Wind damage: the wind causes damage and destruction to the natural vegetation. Cyclone Heta – most trees were toppled, 80% of foliage stripped, burnt by salt spray. Salinisation: salt from the storm surge contaminates the soil and affects its fertility. Cyclone Heta – soil was contaminated by salt and become inhospitable to plants. Social effects of a tropical cyclone - - - Deaths and injuries: caused by drowning, falling debris and collapsed buildings. Cyclone Heta – 1 dead. Cyclone Kina – 22 dead from flying debris and drowning. Damage and destruction: to homes, schools, churches and other community buildings. Cyclone Heta – 100s of homes destroyed (10% of population homeless) and the hospital also destroyed. Cyclone Kina – 2000 people evacuated from homes which were covered in mud or had roofs blown off. Disease: stagnant water and “off” food. Cyclone Kina – outbreak of diarrhoea from people eating food that had gone off. - No drinking water: supplies cut or contaminated. Cyclone Heta – no running water, supplies contaminated with salt. Cyclone Kina – piped water supplies cut, salt contamination caused people to use muddy water from rivers. Economic effects of a tropical cyclone - - - - Reduced income: from agriculture because of crop losses and from tourism because of the damage to hotels. Cyclone Heta – Hotel Niue was destroyed, loss of income from expected 2700 tourists, $240000 of crops lost. Cyclone Kina – 30% of sugar cane was destroyed, rice crop and dairy industry were wiped out, hotels on the Coral Coast damaged. Cost of rebuilding: both business building and infrastructure. Cyclone Heta - $20 million to clean up, $25 million to rebuild, phone system destroyed. Cyclone Kina - $140 million damage, 3 major bridges destroyed, 3000 telephone lines wiped out. Dependence on foreign aid: they have to depend on other countries to help them rebuild and help their people. Cyclone Heta – New Zealand gave $5 million. Better rebuilding: towns and cities are rebuilt in safer locations and using better methods. Cyclone Heta – capital, Alofi, relocated to centre of island. How people increase the effects of tropical cyclones - - - Living and working around the coast: this means people are concentrated in the areas that are most affected by tropical cyclones. Cyclone Heta – most development was around the coast including the capital, Alofi. Growing cash crops: crops such as sugar cane and rice that are grown for profit are not as cyclone resistant as traditional crops such as taro. The tropical cyclone can wipe out the entire cash crop making the country reliant on foreign aid. Cyclone Kina – 30% of sugar cane destroyed and rice crop wiped out. Lack of reliable communication: remote islands and villages do not receive warnings so people aren’t prepared. How people decrease the effects of tropical cyclones - Evacuate: move people to higher ground. Cyclone Zoe – people took shelter in the mountains. Monitoring of cyclones: means that people can be warned and evacuated. Cyclone Heta – people were warned the day before. Preparedness: people should know what to do and have emergency kits ready for if a tropical cyclone strikes. Building stop banks: to stop major flooding. Building codes and land-use zoning: to stop people from building in hazardous areas and to make sure that buildings are strong. Cyclone resistant crops: grow these type crops (e.g. potatoes) that are not easily damaged by winds.