Thursday, April 23, 2009

9R Homework Week 5

Geographic Processes Involved
(Think of this as almost like an introduction)
· What is a Tropical Cyclone? → How and Why do they form?
· Where did Tropical Cyclone Tracy occur? → Indicate this on a map
· When did Tropical Cyclone occur? → Try to include a synoptic chart (weather map) and/or satellite photos for when the event occurred
· A description of what happened → Important to include relevant statistics

The Responsibility and Response of Individuals, Groups and Government

Tropical Cyclone Tracy was the first natural disaster managed by the National Disaster Organisation (known today as emergency management Australia EMA). A state of emergency was declared by the federal government. Darwin was evacuated with support from Qantas, Ansett, the RAAF and Darwin's emergency services. Many parts of Australia donated money, food, building supplies, blankets and medical supplies. This was distributed by the Red Cross. The Red Cross also established information centres to maintain a list of names for people who had died, been evacuated or moved to temporary accommodation. Darwin's police, ambulance and fire brigade also played a key role in the management of Tropical Cyclone Tracy, particularly in the lead up to the cyclone hitting and in the hours after it hit. The clean up operation took just over 6 months and in February 1975 the Federal government passed the Darwin Reconstruction Act which provided $300 million to rebuild Darwin's infrastructure.

Organisations That Provided Assistance


There were significant economic, social and environmental impacts as a result of Tropical Cyclone Tracy
Economic Impacts
- Estimated cost of disaster $950 million
- Darwin's population went from 45000 to 10500 as many evacuees did not return this had a major impact on the local economy
- Major damage to infrastructure (roads, electricity supply etc)
- Up to 80% of buildings were destroyed

Social Impacts
- Claimed 49 lives
- Approximately 650 people treated for injuries
- More than 35000 people evacuated
- Many people were placed under large amounts of stress due to loss of relatives, friends and property

Environmental Impacts
- Large amounts of vegetation destroyed (thousands of trees)

Impacts - Introduction

As geographers, we classify the impacts of natural hazards into three main categories:
- Social
- Economic
- Environmental

Tropical Cyclones are dangerous because they produce destructive winds, heavy rainfall with flooding and damaging storm surges that can cause inundation of low-lying coastal areas.

Cyclones have wind gusts in excess of 90 km/h around their centres and, in the most severe cyclones, gusts can exceed 280 km/h. These very destructive winds can cause extensive property damage and turn airborne debris into potentially lethal missiles. It is important to remember that, during the passage of the cyclone centre or eye, there will be a temporary lull in the wind, but that this will soon be replaced by destructive winds from another direction.

Heavy rainfall associated with the passage of a tropical cyclone can produce extensive flooding. This can cause further damage and death by drowning. The heavy rain can persist as the cyclone moves inland and decays, hence flooding due to a decayed cyclone can occur a long way from the tropical coast as the remains of a cyclone move into central and southern parts of the continent.

The destructive winds accompanying tropical cyclones also produce phenomenal seas, which are dangerous both for vessels out at sea and those moored in harbours. These seas can also cause serious erosion of foreshores.

Potentially, the most destructive phenomenon associated with tropical cyclones that make landfall is the storm surge. Storm surge is a raised dome of water about 60 to 80 km across and typically about 2 to 5 m higher than the normal tide level. If the surge occurs at the same time as a high tide then the area inundated can be quite extensive, particularly along low-lying coastlines.

Where Did Cyclone Tracy Occur?

Tropical Cyclone Tracy hit the City of Darwin in the Northern Territory of Australia (12*S, 130*E) at 1am on the 25th of December 1974. Cyclone Tracy was a category 4 Cyclone with maximum winds of 217km/h.

Geographical Processes

Tropical Cyclones

Tropical Cyclones are described by the Bureau of Meteorology as low pressure systems that form over warm tropical waters and have gale force winds (sustained winds of 63 km/h or greater and gusts in excess of 90 km/h) near the centre. Tropical cyclones are like giant whirlwinds where the air moves in a large spiral around the centre of very low air pressure Tropical cyclones generally occur in the northern parts of Australia and often cause widespread damage and destruction.