Full Geography Secondary 3 Express- Floods and Droughts 1
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Full Geography Secondary 3 Express- Floods and Droughts 1 Presentation Transcript

  • 1. + 3 Express Pure Geog: Floods and Droughts 19h April 2012 Causes of Floods and Droughts Arman Alluwie TP2 SHSS
  • 2. + 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 AprilArman Alluwie TP2 SHSS
  • 3. + 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 TestArman Alluwie TP2 SHSS
  • 4. + 4 Lesson Objectives  By the end of the lesson, I would have  described the natural and human causes of floods and droughtsArman Alluwie TP2 SHSS
  • 5. + 5 Natural Hazards Floods Droughts Causes Natural causes Natural causes Eg. Excessive rainfall Eg. Delayed or insufficient rainfall Human causes Human causes Eg. Clearing of forests Eg. Reduced forest cover Today Impact on people and Eg. Loss of lives Eg. Shortage of water the environment and food How people have Eg. Building artificial Eg. Management of adapted to floods and levees or dykes watershd and droughts agricultural practices pg. 149 of textbookArman Alluwie TP2 SHSS
  • 6. + 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 Q3cArman Alluwie TP2 SHSS
  • 7. + 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,cArman Alluwie TP2 SHSS
  • 8. + 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 Q1cArman Alluwie TP2 SHSS
  • 9. + 9 Natural Hazards Floods Droughts Causes Natural causes Natural causes Eg. Excessive rainfall Eg. Delayed or insufficient rainfall Human causes Human causes Eg. Clearing of forests Eg. Reduced forest cover Impact on people and Eg. Loss of lives Eg. Shortage of water the environment and food How people have Eg. Building artificial Eg. Management of adapted to floods and levees or dykes watershd and droughts agricultural practicesArman Alluwie TP2 SHSS
  • 10. + 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 yearArman Alluwie TP2 SHSS
  • 11. + 11 Causes of Floods  Natural Causes 1. Excessive rainfall 2. Storm surges 3. Melting snow 4. Global atmospheric processes 5. Movements of the Earth‟s surface  Human Causes 1. Clearing of forests 2. Urban development 3. Impacts of enhanced greenhouse effectArman Alluwie TP2 SHSS
  • 12. + 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)Arman Alluwie TP2 SHSS
  • 13. + 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 shallowerArman Alluwie TP2 SHSS
  • 14. + 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 landArman Alluwie TP2 SHSS
  • 15. + 15 Natural causes of floods: Storm surges http://www.nhc.noaa.gov/surge/animations/hurricane_stormsurge.swfArman Alluwie TP2 SHSS
  • 16. + 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 textbookArman Alluwie TP2 SHSS
  • 17. + 17 Natural causes of floods: Storm surges shallow shelf deep shelf not all coastal areas would be affectedArman Alluwie TP2 SHSS
  • 18. + 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, CanadaArman Alluwie TP2 SHSS
  • 19. + 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 textbookArmanAlluwie TP2 SHSS
  • 20. + 20Indonesia/ Peru,Australia South America Arman Alluwie TP2 SHSS http://www.mygeoscienceplace.com/ElNinoLaNina.html
  • 21. + 21Indonesia/ Peru,Australia South America Arman Alluwie TP2 SHSS
  • 22. + 22Indonesia/ Peru,Australia South America Arman Alluwie TP2 SHSS
  • 23. + 23Indonesia/ Peru,Australia South America Arman Alluwie TP2 SHSS http://www.mygeoscienceplace.com/ElNinoLaNina.html
  • 24. + 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 monthsArman Alluwie TP2 SHSS
  • 25. + 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, IndonesiaArman Alluwie TP2 SHSS
  • 26. + 26 Human causes of floods: Clearing of forests  Areas with extensive clearing of forests  Eg. China and Bangladesh (Ganges and Brahmaputra Rivers)Arman Alluwie TP2 SHSS
  • 27. + 27 Human causes of floods: Clearing of forests TitleArman Alluwie TP2 SHSS Legend
  • 28. + 28Arman Alluwie TP2 SHSS
  • 29. + 29Arman Alluwie TP2 SHSS
  • 30. + 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, LondonArmanAlluwie TP2 SHSS
  • 31. + 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 regionsArman Alluwie TP2 SHSS
  • 32. + 32 Causes of Droughts  Natural causes of droughts 1. Delayed rain or insufficient rainfal 2. Global atmospheric processes  Human causes of droughts 1. Reduced forest cover 2. Impact of enhanced greenhouse effect 3. Overuse of waterArman Alluwie TP2 SHSS
  • 33. + 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 seasonArman Alluwie TP2 SHSS
  • 34. + 34 Natural causes of droughts: Global atmospheric processesIndonesia/ Peru,Australia South America Arman Alluwie TP2 SHSS
  • 35. + 35 Natural causes of droughts: Global atmospheric processesIndonesia/ Peru,Australia South America Arman Alluwie TP2 SHSS
  • 36. + 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)Arman Alluwie TP2 SHSS
  • 37. + 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 gasesArman Alluwie TP2 SHSS
  • 38. + 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 pondsArman Alluwie TP2 SHSS
  • 39. + 39 Lesson Objectives  Am I able to  describe the natural and human causes of floods and droughts?Arman Alluwie TP2 SHSS