Cyclone Yasi

Key Geographical terms

On the 3rd of February, Cyclone Yasi crossed the Queensland coast at about 25km/h and with wind gusts of 285km/h. Thousands of people were evacuated from Cairns after fears the city could take a direct hit. Yasi's path crossed the coast at Mission Beach, flattening sugar cane farms, damaging banana crops, and causing huge damage to the Great Barrier Reef. The cyclone was so powerful that it didn't completely disperse until it reached the centre of Australia, near Alice Springs. It's estimated Cyclone Yasi caused $3.6 billion in damages - the most costly cyclone in Australia to date.

Cyclone Yasi approaches Queensland

What causes tropical cyclones to form and what characteristics of them do we need to be concerned by?

Cyclones start as tropical storms that travel over the warm waters of areas such as Queensland. The warm water is evaporated, and with the circulating winds of a storm, the cyclone grows. As the cyclone travels with the wind, it grows stronger, and if it does move over residential areas, it can have catastrophic effects. The gale force winds can extend hundreds of kilometers from the cyclone centre. The sustained winds around the centre can reach around 118 km/h.

Tropical cyclones occur in a band close to the equator, because the climate is perfect for them. Warm water, moist air and tropical storms make great cyclones.

Cyclones cause horrific damage to communities in tropical areas. Flooding is common, which causes water damage; damaging houses and businesses. The strong wind collapses trees and houses, making it dangerous to drive, and unsafe to be outside. Water surges are common, pulling boats into the jetties and shores, damaging not only the boats, but also houses and piers. The damage that tropical cyclones cause is catastrophic economically; rebuilding infrastructure, funding farmers with damaged crops, and fixing broken communities is not friendly on the wallet. Cyclone Yasi cost the Australian Government between $800 million and 3 billion dollars, meaning that the disaster not only caused damage to Australian communities, but also to the Government's financial needs.

The movement of cyclones is very important. If a cyclone travels on the water for a long time before moving onto land, then it is going to be big. The movement defines the outcome of the places that are affected, and which regions could be damaged. It also affects the scale of a cyclone. If the wind is not very strong, and the amount of water in the air is low, then the movement of the storm will be small. But on the other end of the scale, if the storm’s wind is big, and the amount of moisture in the air is large, then there is a greater threat on coastal communities.

Tropical cyclones occur in a certain region, which consists of a minimum of 26°C water temperature, between eight and twenty degrees latitude. The climate has to be tropical, which is what limits it to this area of the world.

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What was the pathway of Yasi and how did this affect the cyclone?

On the 26th of January 2012, Yasi started as a tropical disturbance 300km off the coast of Fiji, then turning into a tropical cyclone headed straight towards the Australian coast. The cyclone travelled roughly 2,396km over warm water, giving it an insane amount of time to grow bigger and stronger, so when it hit the coast near Mission Bay on the 3rd of February, it had an explosive effect.

The eight days it had to develop had a huge impact on the cyclone. The image below shows the cyclone's path, and indicates when it was strongest. As you can see, for the first day or two, the cyclone was small, but eventually grew stronger, as indicated with the yellows and reds.

The cyclone was at it’s strongest off the coast of Australia, which increased the storm surge, helping the torrential rain flood the area. It then dies down over the land (as all cyclones do) because there is no water to build the foundation of the storm. The cyclone still travelled an amazingly far way when off the water, making its way to Alice Springs in Central Australia.

The scale of Yasi was measured as a category 5 cyclone. This is important because it was heavily influenced by Yasi’s path. The cyclone travelled over a lot of water, giving it a lot of time to grow.

The movement of cyclones depended on how far it travels. Cyclone Yasi travelled a long way over warm water, which is what dictated the size of the storm.

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What were the characteristics of Yasi?

Cyclone Yasi was a catastrophic natural disaster, bringing with it torrential rain, extreme winds and storm surges that damaged thousands of people’s homes and businesses. The cyclone was arguably one of the worst cyclones that Australia has ever witnessed.

Wind speeds reached 250 kilometers per hour, and gusts up to 305 kilometers per hour. This means that the wind was constantly 250km, with bullet winds at 305km. In Port Phillip Bay on a windy day, we might get 50 km, just to put it into perspective.

The storm surge on the coast reached 7 meters above high tide, so with the torrential rain and storm surge, flooding was a given, damaging thousands of homes in its wake.

The heaviest rainfall recorded during the cyclone was more than 300 millimetres. As you can see (in the image below), where the cyclone hit the coast, there was approximately 200mm of rain seen in a very short period of time. The areas around Mission Bay don’t look like they were effected as much by the rain. To put it in perspective here in Melbourne we get an average of 50mm of rain a month, and these areas got that and above in a 5 day period.

Cyclones only occur in a certain region, between 8° and 20° latitude. This is a key characteristic of a cyclone.

Spacial change over time is a good way of demonstrating how much a cyclone can grow. The time lapse of Yasi’s path shows us this. The change over time is dependant on the water the cyclone is over. The storm grows faster over water than over land, hence why this KGI is important.

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How were the natural and cultural landscapes affected by Yasi?

The Great Barrier Reef was obviously affected, as I have talked about before. 300km of reef was damaged to various degrees, leaving coral on the sea floor and species with fewer numbers. Scientists have declared that the reef will take anywhere between 5 to 15 years to fully recover.

The Mahogany Glider was already an endangered species before Cyclone Yasi, and with the torrential winds, these little possums’ numbers lowered even more. The Glider was already limited to a small section of Sclerophyll Forest, and when that forest was damaged during the cyclone, their food source narrowed.

The Southern Cassowary’s natural habitat is in the lowland rainforest of Mission Beach, which as we know was where the cyclone first hit the coast. The bird was already endangered, and in the 12 months following Cyclone Yasi, 31 birds died. This tells us that the Cassowary’s food source was limited after the cyclone, due to the damage done to vegetation.

400,000 people were living in Cyclone Yasi’s path. We are very lucky that the cyclone only took one person’s life, considering the scale of the disaster. Thousands of homes were destroyed due to water, electrical and wind damage, leaving so many Queensland residence without a roof over their head.

The distribution of where people lived during Cyclone Yasi determined the number of houses damaged. There is a greater population of people living on the coast because it is better suited to people. The problem with this is disasters like Yasi are possible, and will end in catastrophe.

This also effected the numbers of cassowaries and gliders. They were distributed in a small area of forest right in the middle of Yasi's path, which resulted in reduced numbers.

Effects Yasi had on banana plantations

75% of Australia’s banana plantations were destroyed during the cyclone, resulting in over $800 million dollars damage in agriculture. The price of bananas went through the roof. Before the cyclone Woolworths were selling bananas for an average of $2.00/kg, compared to $15/kg after the natural disaster.

The destroyed crops also meant that farmers didn’t have product to sell, giving them no source of income. Banana trees take approximately 9 months to start producing fruit. This means that farmers whose crops were destroyed during the cyclone had to sustain themselves for at least 9 months before they could start selling fruit and earning an income.

The banana plantations were distributed in the same area. This meant that most of the plantations were damaged, leaving very little bananas edible and sellable.

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Effects Yasi had on the Great Barrier Reef

Damage to the reef extended over 89,090 km2 of coastline in patches. Most areas effected either suffered severe damage or minor damage, depending on the area. With this piece of evidence, scientists have concluded that severely damaged areas will recover between 5 and 15 years.

Branching coal suffered from the most damage during the storm. The coral’s light limbs were snapped off and deposited on the sea floor, along with plate corals that had been snapped in half. Sensitive organisms such as sea grass and coral are known to become stressed during events such as Cyclone Yasi, which in sever cases has killed them.

The Cyclone also affected the tourism side of the reef. Companies that specialize in Reef snorkeling were put on hold the let the reef recover, as the damage done was just as bad as the thousands of homes that were destroyed.

The special interaction between Cyclone Yasi and the reef is actually meant to happen. The reef is obviously in a dangerous situation when it comes to cyclones, but the storm is a time for the reef to rejuvenate and change the scenery.

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What changes for the region and for wider Australia have occurred due to Cyclone Yasi?

Cyclone Yasi made Australia realise what the natural world is capable of. Since the cyclone the Queensland government has adopted a new policy demanding stricter regulations for building houses in cyclone prone areas. This regulation was put into place to minimise damage to houses and to better prepare families for cyclones such as Yasi.

The government has also put in new laws on building new structures. Before Cyclone Yasi, telephone poles were placed on the top of hills; during the cyclone the strong winds easily tore the poles out of the ground, highlighting the problem. The site for a new building must be approved after undergoing wind load and wind speed tests. Houses being built on low-lying plains are particularly prone to flooding and must now be built on stilts, or preferably not in these areas.

I think Yasi taught Australia how dangerous cyclones can be, and that when disaster does strike, we need to be prepared for it.

Cyclone Yasi wasn’t cleaned up in one night. It took months to bring life back to normal, which special change over time would help with. Every tree off the road and house made livable was a step forward in the troubled area of Queensland.

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