Perth Academy. Geography Department

Transcription

1 Perth Academy Geography Department Natural Hazards Tropical Storms

2 Natural Hazards Natural Hazards affect a large percentage of the world s population. Despite the damage and destruction caused, there are still many people living in areas affected by them. Unit Overview In this unit we will examine the main features of natural hazards, with a main focus on tropical storms. Over the coming weeks we will focus on the following aspects of tropical storms: What are natural hazards? Where are they found and why? How are they formed? Their effects. Contrasting case studies of a tropical storm in a developing and a developed country. Methods of predicting tropical storms. Preparing for tropical storms. 1 Unit Introduction What is a natural hazard? Where do they take place? In your groups, write down everything you know about natural hazards onto your section of the place mat, you have 2 minutes to do this. Watch the video clip on natural hazards and answer the following questions in your jotter: 1. Write down 3 types of natural hazard. 2. How do natural hazards affect humans? 3. What hazards can human activity contribute to? 4. In which area has the risk of flooding increased? 5. How can humans reduce the risk of hazards?

3 The exposure of an area to various natural hazards depends on its location in the world. Some areas are more prone to earthquakes than others, some are more at risk of hurricanes etc. Using your blank world map, shade in the world s natural hazards hotspots, from the diagram below and on the screen. 2 With the help of an atlas, use your shaded map to name 10 countries threatened by the risk of natural hazards. Throughout history, these hazards have caused many problems for societies, whether it be structural damage, loss of plant life, or indeed death. Read over the accompanying data sheet, showing some of the deadliest hazards in the world s history. Construct a bar graph, showing the 10 deadliest natural hazards in world history, using the information sheet. Your graph must have: A title Labelled axis Units of measurement An appropriate scale Colour A key

4 Tropical Storms What is a tropical storm? Tropical storms are large areas of intense low pressure and extreme depressions. On a satellite image (see picture above), a tropical storm will show as a huge, swirling mass of cloud. 3 A low pressure system, or "low", is an area where the atmospheric pressure is lower than that of the area surrounding it. Lows are usually associated with high winds, warm air, and atmospheric lifting. Because of this, lows normally produce clouds, precipitation, and other bad weather such as hurricanes and cyclones. At the centre of a tropical storm, there is a calm area with no wind known as the eye of the storm. The route taken by a tropical storm is called its path. Does Scotland get Tropical Storms? Why do they not form everywhere? The Location of Tropical Storms

5 Using the blank map provided, shade in the areas where tropical storms form and glue this into your jotter under the heading, The Location of Tropical Storms. Under your map, write a paragraph describing the areas where these storms are found. Remember to include as much detail as possible, such as the names of countries, oceans and lines of latitude. What do you notice about the names of the tropical storms across the world? 4 The Formation of Tropical Storms Tropical storms use warm, moist air as fuel. That is why they form only over warm ocean waters near the equator. The warm, moist air over the ocean rises rapidly upward from near the surface and becomes saturated with evaporated moisture. This means that there is less air left at the surface (i.e. low pressure). Air from surrounding areas with higher air pressure rushes in to the low pressure area to try to equalise the pressure. Then that new air becomes warm and moist and rises, too. As the warm air continues to rise, the surrounding air swirls in to take its place. The rotation of the Earth encourages violent winds to rotate around the central eye of the storm. These winds are anti-clockwise in the Northern Hemisphere. In the central eye, the pressure is very low with descending winds, increasing temperatures, clear skies and calm, dry conditions. As the warmed, moist air rises and cools off, the water in the air forms towering cumulonimbus thunderclouds (because there is a huge amount of condensation). The whole system of clouds and wind spins and grows, fed by the ocean s heat and water evaporating from the surface.

6 : Pop-up tropical storms Complete this task in your jotter using templates, coloured pencils and instructions from the powerpoint. World Distribution of Tropical Storms As we have seen from our map, tropical storms are only found in certain areas of the world. These are the areas that have the necessary conditions for them to form. These are: Warm seas, which have a surface temperature of 27 C or more and water to a depth of at least 60 metres. A low air pressure, with the air beginning to rise. Damp moist air with a relative humidity of 60% or more. Between latitudes 5 and 20 north and south of the equator i.e. between the Tropic of Cancer and the Tropic of Capricorn. 5 Copy the bullet points showing the necessary conditions for tropical storms to form into your jotter under the heading Necessary Conditions for Tropical Storms. As you will remember from your map showing the location of tropical storms, depending when you are in the world, a tropical storm will have a different name. For example: In America, the Caribbean and the Gulf of Mexico i.e. the Atlantic Ocean, these storms are called Hurricanes. In the Pacific Ocean they are known as Typhoons. In the Indian Ocean they are known as Cyclones. In Australia they are known as Willie-Willies. What do you notice about these tropical storms? Why does this happen?

7 A tropical storm is classified as a hurricane when wind speeds reach 74 miles per hour, though hurricane winds can be much faster. The centre of a hurricane is called an eye, where winds are light and cloud is broken. Since 1954, all tropical storms have been given names so they can be identified quickly and told apart. The first storm of the year will be given a name beginning with A' for example Alexandra, the next with B etc. Only women s names were used in the past, but from 1979 alternate male and female names have been used. There are six lists of names that are used in rotation and recycled every six years so the 2013 list will be used again in The names of powerful hurricanes, which caused a lot of damage, are never used again. 6 Effects of Tropical Storms

8 Tropical storms can have devastating effects on people, wildlife, plant life and infrastructure. Areas affected often take many years to recover from a single storm. The effects that areas experience can be divided into primary and secondary. Primary effects are the immediate physical effects which an area can experience. For example: High winds Torrential Rain Storm Surges Localised Tornadoes and Waterspouts 7 Secondary effects are the longer term impacts, which affect the area for an extended period of time. The length of time it takes for an area to recover is largely dependent upon its development, i.e. its wealth. This is something we will focus on in more detail during our case studies. These secondary effects can be social, economic or environmental: Social: effects on people and society Economic: effects on the wealth of the area Environmental: effects on the atmosphere, landscape, plant life, wildlife etc. In pairs, organise the cards showing effects of tropical storms under the correct heading - social, economic or environmental. Once you have decided where each of the cards should go, we will discuss as a class and then copy the final list into your jotters under the heading Effects of Tropical Storms.

9 Storm Surges Storm surges occur where the sea level along a shoreline rises as the result of a storm. This is shown in the diagram below: 8 There are two main causes of storm surges: 1. The Eye Pile: The low pressure draws the water beneath it upwards to form the eye pile. It gets dragged along with the eye. The eye pile grows in height as it is forced into shallower water. It splats onto the land as the storm makes landfall. 2. Wind-blown Water: Zonal winds push the water in the same direction that they are moving. If the wind blows long enough and hard enough, the water banks up and floods the land when the wind blows onshore. Copy the diagram and information on storm surges into your jotter. Measuring Tropical Storms You may have heard in some of the videos reference to a category of hurricane in reference to how severe it is. The strength of a tropical storm is measured using the Saffir- Simpson Scale:

10 Using the information from video, write down a named example of each category of hurricane and the year it hit. How many category 5 hurricanes have made landfall in the USA? Tropical storms usually weaken when they hit the land because they are no longer being fed by the energy from the warm ocean waters. When passing over the Caribbean, they can weaken as they pass over the islands before strengthening again as they pass over water and head towards the coast of the USA. 9 Developed Country Case Study Research a tropical storm of your choice and present your findings e.g. poster, powerpoint, written report, newspaper report, creative eyewitness account etc. Regardless, you will need to make sure that you include the following: The name and dates of the storm How the storm formed Where the storm formed The strength of the storm The path that the storm took from beginning to end Include the names of countries, oceans and/or US states that it passes though Describe the effects of the winds and heavy rainfall on people and the landscape including: Forests Farming Buildings Bridges Communications Describe the impact of the storm surge in coastal areas on people and the landscape The more detail you include, the better your work will be. Make sure that you include diagrams and pictures to prove what you have written.

11 Developed Country Case Study: Hurricane Katrina On the morning of August 23 rd 2005, Hurricane Katrina formed over the skies of Florida due to hot and humid weather conditions. As it worked its way across the state, it was still only classified as a category 1 hurricane but had already started taking lives and causing destruction. When she reached the Gulf of Mexico, she had grown to a category 3 hurricane, due to the warm water in the gulf. By the time she was in full flow, Katrina had reached a staggering category 5 status, making it the 6 th most powerful hurricane in history. This new surge and growth that she had gained caused death and destruction from Florida to Texas. The states affected most by the hurricane were Louisiana, Mississippi, Texas, Alabama and Florida. 10 Shade in the areas affected by Hurricane Katrina on your blank map of the USA and glue this into your jotter. Identify the following areas on your map: the Gulf of Mexico, New Orleans, Louisiana, Alabama, Mississippi, Florida. Of all the areas affected by Katrina however, New Orleans suffered by far the most in terms of the people and the landscape. These effects are still visible in the area today. In reflecting upon this great storm hitting the area, many scientists believe that more could have been done to limit the damage from the storm. Watch the documentary on Hurricane Katrina and take notes under the following headings: Effects on People, Effects on Landscape, Causes, Response to Storm. Using the information you have gathered, in pairs produce a story board, outlining the key stages in the storm s impact on New Orleans.

12 Predicting Tropical Storms With the increased use of and improvements in technology over the last 20 years, it has become easier for patterns of weather to be tracked in advance. The use of satellite communication has made this a much more simplistic exercise, giving forecasters an opportunity to produce detailed reports in advance, which can be broadcast via television and the internet. 11 Why Where are does tropical this information storms easier come to predict? from? Rich developed countries, such as the USA, can invest in technology to predict the general area in which hurricanes will strike. This technology is not so readily available to developing countries although many countries receive information from organisations such as the Joint Typhoon Warning Centre (Pacific) or National Hurricane Centre (Atlantic) to help them prepare for storms. The track of a tropical storm is affected by a great many factors, so they are very unpredictable. Forecasters have a 20-25% chance of knowing exactly where a tropical storm will hit 48 in advance of landfall. Forecasts are made available to residents on the internet so that they can make decisions about whether they need to evacuate. This is obviously a much more useful means of communication in a developed country where the percentage of residents with internet access is much higher than in developing countries. Indeed one of the major problems in preparing for a storm in a developing is communicating with the people in an area that is likely to be affected as the infrastructure may well be poorly developed. Watch the above clips showing some of the methods used to predict hurricanes and take notes in the form of a mind map.

13 Preparing for Tropical Storms 12 As a result of improved technology and communication systems governments are now better equipped to warn their residents about the onset of a tropical storm. Due to differing levels of risk for individual storms and the possibility of inaccurate predictions, full evacuations are not always possible or practical; citizens are informed by governments of the steps that can be taken in preparation for a hurricane. Brainstorm with the person sitting beside you the different ways that you think that both countries and individuals can predict that tropical storms will happen and ways of planning to reduce the damage that storms may cause. Share this information with your table and combine all of your thoughts. Create a spider diagram showing all of your ideas.

14 Hurricane Survival Kit Surviving the threat of a tropical storm can be made easier through the correct advice from governments and the owning of appropriate items. In this lesson you will work in pairs to examine the types of recommended items to include in a hurricane survival kit and think about why this is the case. You will then produce a hurricane safety information leaflet outlining the main information and advice you would give to people in order to survive a hurricane. 13 Read through the information guide provided in your pairs. Identify what you think are the 5 most important items for ensuring survival and give reasons why this is the case. Use the information from the survival guide to produce a leaflet outlining the key steps for hurricane survival. Ensure that your leaflet is well illustrated so that those who do not speak English would be able to make sense of it. Extension : Thinking Skills Why might such a document be less effective in developing countries? Summarise your answer in a paragraph.

15 Responding to Tropical Storms: The Role of Aid Agencies When responding to any natural hazard, aid can be provided in two forms, short term and long term. Short term aid comes in the form of aid that is immediately required by an affected area such as temporary shelter, canned food, clothing, bottled water and medicine. Long term aid comes in the form of things that an area requires to permanently repair damage and get back on its feet. This type of aid includes reconstructing roads, schools, hospitals and houses, repairing power lines and clearing debris. Long term aid can also include educating citizens of an area in basic healthcare and alternative farming methods in order to help citizens deal with any future problems. 14 Aid can also be classified depending upon who is providing it: Bilateral Aid is aid given from one country to another, e.g. from the USA to Bangladesh. Multilateral Aid is aid given by international organisations to a country e.g. The United Nations (UN) to Bangladesh. Voluntary Aid is aid given by non government organisations such as charities, to an affected area e.g. Oxfam, Red Cross, Christian Aid. Financial Aid is where banks give loans to a country to assist its development e.g. World Bank. While countries who suffer from natural hazards in particular rely upon aid given by various organisations, it is often argued that this aid can actually further disrupt their development. This is a huge issue, particularly for developing countries such as Bangladesh who have no choice but to accept aid regardless of who it is coming from. Read through the types of aid listed above. Which of these do you think could result in further problems for a developing country? Write a paragraph to explain and justify your answer.

16 Why do People Live in Areas Affected by Tropical Storms? Case Study: Florida 15 Florida, USA is one of the world s most desirable places to live and one the most popular holiday destinations for worldwide tourists. Situated just off the warm waters of the Gulf of Mexico however, it is also prone to devastating tropical storms on a regular basis. So with this in mind, why do people continue to live here? : Watch the following video clips: Write down 3 things that make Florida an attractive place to live and work. Citizens of Florida as well as tourists are well aware of the risk of tropical storms in the area but continue to live and visit here. With preparation measures widely in place as well as information from the government readily available, the threat of tropical storms to human life in Florida is significantly reduced. In developing countries such as Bangladesh, however, people are less fortunate.

17 Case Study: Bangladesh 16 Situated on the coast of the Bay of Bengal, the warm waters of the Indian Ocean make perfect conditions for cyclones to form. With this in mind, once again we can ask, why do people live here? Alongside difficulties in forecasting and communicating the threat of cyclones, governments are limited in their ability to support citizens when a cyclone hits in Bangladesh. The citizens themselves also have great difficulty in knowing about the threat of cyclones and vacating areas affected by them. In developing countries the vast majority of people are forced to live in these affected areas for various reasons. : Thinking Skills In groups of 3, come up with 2 reasons why people in countries like Bangladesh are unable to move away from areas affected by cyclones. Try to imagine what life is like in these countries, the wealth that people have, the knowledge that people have and the types of job that they do. You may use the Bangladesh country factfile to help you.