full geography secondary 3 express- floods and droughts 1

Arman Alluwie TP2 SHSS

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3 Express Pure Geog:Floods and Droughts19h April 2012Causes of Floods and Droughts


2+Administration

Class Tests will be returned latest on Tuesday 24th April

Floods and Droughts Causes (Today) Impact and Adaptation (Monday 23rd April)

Revision Lectures Bring your own Questions Tuesday 24th April, Wednesday 25th April


3+What did we learn last lesson?

Impact on Plants and Animals

Wrapped up on Climate Change with a “Hot Planet?” alternative technology current concerns of climate change

Class Test


4+Lesson Objectives

By the end of the lesson, I would have described the natural and human causes of floods

and droughts


5+

Natural Hazards

Floods Droughts

Causes Natural causesEg. Excessive rainfall

Natural causesEg. Delayed or insufficient rainfall

Human causesEg. Clearing of forests

Human causesEg. Reduced forest cover

Impact on people and the

environment

Eg. Loss of lives Eg. Shortage of water and food

How people have adapted to floods

and droughts

Eg. Building artificial levees or dykes

Eg. Management of watershd and agricultural practices

pg. 149 of textbook

Today


6+Past O Level Questions (2000- 2009) Select one of the climatic disasters shown on Fig.

2, either droughts or tropical storms State the climatic disaster selected and name an area

where it occurs [1] Explain the reasons for its occurrence in that area [4] Describe how it affects people living in the named

area [5] Describe some of the measures taken to reduce its

effects on the loves of people in this area [5]

N2001 P2 Q3c


7+Past O Level Questions (2000- 2009) What is a drought? Describe the effects of drought

on the lives of people living in areas such as the Sahel or Southern Africa [5]

N2006 P2 Q1b,c

Describe the effects of either floods or droughts upon the lives of people in areas where they are experienced. [5]

N2007 P2 Q1b,c


8+Past O Level Questions (2000- 2009) Severe weather conditions may also cause human

disasters. Using examples, discuss the impact of droughts on human lives and the environment. [8]

N2008 P1 Q1c


9+

Natural Hazards

Floods Droughts

Causes Natural causesEg. Excessive rainfall

Natural causesEg. Delayed or insufficient rainfall

Human causesEg. Clearing of forests

Human causesEg. Reduced forest cover

Impact on people and the

environment

Eg. Loss of lives Eg. Shortage of water and food

How people have adapted to floods

and droughts

Eg. Building artificial levees or dykes

Eg. Management of watershd and agricultural practices


10+Floods and Droughts

Hazard Definition: can endanger lives and destroy property

Flood Definition: occurs when land that is usually dry is

submerged by large amounts of water

Drought Definition: prolonged period with little or no rainfall normally occurs in regions which receive 250- 500

mm per year


11+Causes of Floods

Natural Causes1. Excessive rainfall

2. Storm surges

3. Melting snow

4. Global atmospheric processes

5. Movements of the Earth’s surface

Human Causes1. Clearing of forests

2. Urban development

3. Impacts of enhanced greenhouse effect


12+Natural causes of floods:Excessive rainfall Areas experiencing Tropical Monsoon

Climate

Excess rainwater is unable to seep into the ground

When rivers overflow their banks because river channels can no longer contain excess water

amount (more than usual) frequency (prolonged rain)


13+Natural causes of floods:Excessive rainfall Eg. Yangtze River and Yellow River, China

rain washes large amounts of sediments into rivers sediments deposited on the river beds rivers become shallower


14+Natural causes of floods:Storm surges strong winds raise the waves in the ocean to

exceptionally high levels

tropical storms blow strong winds over the ocean creating gigantic waves, which crash onto the coast

and flood the land


15+Natural causes of floods:Storm surges

http://www.nhc.noaa.gov/surge/animations/hurricane_stormsurge.swf


16+Natural causes of floods:Storm surges Eg. Bangladesh

low-lying relief 80% sits on low-lying

floodplains of Brahmaputra and Ganges Rivers

35% is less than 6 meters above sea level

pg 132 of textbook


17+Natural causes of floods:Storm surges

shallow shelf deep shelf

not all coastal areas would be affected


18+Natural causes of floods:Melting snow Areas experiencing cool temperate climate

Melting snow in spring releases large amounts of water intro rivers

eg. 1986 St. John River, Canada

19+Natural causes of floods:Global Atmospheric Processes El Nino/ La Nina

Alternate patterns of heating and cooling between eastern and western parts of South Pacific Ocean

For a specific place, floods during El Nino, Droughts during La Nina

Eg. ‘97- ’98: flooding of Piura River, Peru Intense El- Nino brought heavy and prolonged rains to

Peru for several months


pg. 133 of textbook


20+

Indonesia/Australia

Peru,South America

http://www.mygeoscienceplace.com/ElNinoLaNina.html


21+

Indonesia/Australia

Peru,South America


22+

Indonesia/Australia

Peru,South America


23+

Indonesia/Australia

Peru,South America

http://www.mygeoscienceplace.com/ElNinoLaNina.html


24+Natural causes of floods:Global Atmospheric Processes El Nino/ La Nina

Alternate patterns of heating and cooling between eastern and western parts of South Pacific Ocean

For a specific place, floods during El Nino, Droughts during La Nina

Eg. ‘97- ’98: flooding of Piura River, Peru Intense El- Nino brought heavy and prolonged rains to

Peru for several months


25+Natural causes of floods:Movements of the Earth’s surface earthquakes cause landslides

soil along hill or mountain slopes loosen up deposited into a river and may cause the water to

overflow

earthquakes triggering off tsunamis undersea earthquake 2004 Indian Ocean Tsunami affecting Banda Aceh,

Indonesia


26+Human causes of floods:Clearing of forests Areas with extensive clearing of forests

Eg. China and Bangladesh (Ganges and Brahmaputra Rivers)


27+Human causes of floods:Clearing of forests Title

Legend


28+


29+

30+Human causes of floods:Urban development Land is cleared to meet needs of urban population

Built-up areas increase Concrete pavements and tarred roads prevent

rainwater from seeping into the ground Less natural vegetation to intercept rain Increase in surface runoff

eg. Areas around River Thames, London



31+Human causes of floods:Impacts of Enhanced Greenhouse Effect Global warming

Higher rainfall in wetter regions

Reduction of ice cover in the polar regions rising sea levels affecting low-lying coastal regions


32+Causes of Droughts

Natural causes of droughts1. Delayed rain or insufficient rainfal

2. Global atmospheric processes

Human causes of droughts1. Reduced forest cover

2. Impact of enhanced greenhouse effect

3. Overuse of water


33+Natural causes of Droughts:Delayed rain or insufficient rainfall Areas with little rainfall

250- 500 mm per year

or Tropical Monsoon Regions Bangladesh/ India Delay of monsoon winds

Prolonged dry season


34+

Indonesia/Australia

Peru,South America

Natural causes of droughts:Global atmospheric processes


35+

Indonesia/Australia

Peru,South America

Natural causes of droughts:Global atmospheric processes


36+Human causes of droughts:Reduced forest cover lower rates of transpiration, leading to less water

vapour fewer clouds formed

ground exposed to direct heating by the Sun soil dries up quickly

load Google Maps (Brazil)


37+Human causes of droughts:Impact of enhanced greenhouse effect Droughts in places with drier climates

Sahel in Africa

Rapid evaporation, which dries up land, rivers and lakes

More imminent with increase in emission of greenhouse gases


38+Human causes of droughts:Overuse of water population, more water is needed for homes,

industry and agriculture

eg. Kothariya, India drought in 2001 population of 4000 get their water from five water

holes dug into floors of ponds


39+Lesson Objectives

Am I able to describe the natural and human causes of floods and

droughts?

full geography secondary 3 express- floods and droughts 1

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