Tropical Cyclones

Geography

Natural hazards: tropical cyclones

Year 9 assessment task 3

Sam borron

Year 9

Mr Hine

Tropical cyclone Larry

Geographical processes associated with tropical cyclones

Tropical cyclones form over warm oceans (above 26.5Лљ C) as low pressure systems and gradually build up intensity. They have clockwise wind circulations and produce gale force winds. These winds can extend hundreds of kilometers from the cyclone center

Tropical cyclones can persist for many days and many follow quite erratic pats. they usually break up or dissipate over land or cooler oceans the circular eye or center of a tropical cyclone is an area carctorise by light winds and often by clear sky. The diameter of the eye is usually aprrox 40 km but can rang from 10 to 100km.the eye is surrounded by a dense ring of cloud about 16 killomiters high,know as the eye wall,witchmarks the belt of the stongest winds and heviest rainfall. The severty ofa tropical cyclone is described in terms of categories ranging from 1 to 5 realated to the the zone of maximum winds

Natural disasters and hazards

A hazard is an event that is a potential source of harm to human life/health/and possessions

Natural hazards are dangerous occurrences in the physical environment event such as a river flooding and earth quakes occur naturally but are only considered hazards in relation to human occupation of a particular place

It’s only a hazard if human life is affected

A natural hazard becomes a natural disaster when damage to people property or society is sufficient to cause a long recovery and rehabilitation process

The four major hazards that affect are

1. drought

2. bush fires

3. tropical cyclones and storms

4. floods

Cyclone Larry

• AT LEAST 30 PEOPLE WERE INJURED; MOST INJURIES WERE MINOR.

• ABOUT HALF THE BUILDINGS IN INNISFAIL AND 80 PER CENT IN BABINDA, TO THE NORTH, WERE DAMAGED.

• THE BANANA INDUSTRY REPORTED LOSSES OF UP TO $300 MILLION, LEAVING UP TO 4000 PEOPLE OUT OF WORK.

• MORE THAN 120,000 HOMES WERE WITHOUT POWER, WATER OR SEWERAGE

• ALL SCHOOLS AND MOST BUSINESSES WERE LIKELY TO BE CLOSED FOR THE WEEK

Severe Tropical Cyclone Larry caused a significant storm surge. The largest recorded surge was 2.30 metres at Clump Point. Cardwell and Mourilyan recorded storm surges of 1.76 metres and 1.34 metres respectively. Unfortunately no gauges were located at the site of the maximum onshore winds, so the highest storm surge associated with Larry was not sampled. However, the highest inundation recorded was a very substantial 4.9 metres above the expected tide at Bingil Bay, and 4.2 metres at Etty Bay. There was no evidence of significant waves in the main impact area, indicating that the majority of the inundation was produced by the storm surge. Storm surge data was provided by the Queensland Environmental Protection Agency (EPA), in the publication “Fact Sheet Tropical Cyclone Larry”Rainfall associated with Larry resulted in flooding in the Mulgrave, Russell, Tully and Murray Rivers on the north tropical coast and in the Gulf Rivers. Road and rail access was disrupted for several days due to flooding and, at times, prevented road access to the Babinda-Innisfail area from both the north and south. Fortunately, the river rises in the Johnstone River at Innisfail remained below minor flood level.

Rapid river rises occurred in the Mulgrave and Russell Rivers on 20 March following heavy rainfall. The highest rainfall total recorded was 139mm in 3 hours to 9am at The Boulders on Babinda Creek. Major flooding occurred in the Mulgrave River during the day with the river level at Gordonvale peaking at 15.2 metes, which was one metre over the Bruce Highway bridge.

The heaviest rainfall in the Tully River catchment was over 500 mm recorded at Euramo, near Tully, in the 72 hours to 9am 22 March. River levels rose slowly in both the Tully and Murray Rivers and major flood levels overtopped the Bruce Highway from 21 to 24 March.

Economic impacts

• Total estimated costs of damage is $1.5 billion

• Insurance bill for more than $1,200 for household insurance, almost double last year's bill of $693.

• The high winds caused enormous damage to infrastructure

• Approximately 40% of homes were damaged

Social impacts

• Cyclone Larry took no human lives

• A lot of hospital police stations and fire stations were damaged

• A few people after cyclone Larry hit were psychologically damaged

Environmental impacts

• Cyclone Larry destroyed 80-90% of the bananas

• Scientists have calculated that around 30% of the Wet Tropics World Heritage Area was impacted to some extent by Cyclone Larry.

(1) �Cyclone science’ shows rainforest impacts and recovery

Reference: 07/44

A year on from Cyclone Larry research into the environmental impacts of the category 4/5 storm is starting to deliver interesting results. This suite of projects involving 25 scientists from 5 institutions was set up shortly after the cyclone hit to investigate its effects on the rainforests of the Wet Tropics.

20 March 2007

“This is probably the most