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Ganges Delta


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Ganges Delta

  1. 1. Bangladesh Delta
  2. 2. Aim: to understand the processes that lead to the formation of a delta <ul><li>Define source, mouth, estuary, delta, load, alluvium </li></ul><ul><li>Recognise that rivers are agents of erosion, transportation and deposition </li></ul><ul><li>Understand how rivers transport their load </li></ul><ul><li>Understand the factors that lead to deposition </li></ul>
  3. 3. <ul><li>A rivers SOURCE IS …… </li></ul><ul><li>The work of a RIVER : </li></ul><ul><ul><li>Erosion </li></ul></ul><ul><ul><li>Transportation </li></ul></ul><ul><ul><li>Deposition </li></ul></ul><ul><ul><li>EROSION </li></ul></ul><ul><ul><li>Attrition </li></ul></ul><ul><ul><li>Corrasion </li></ul></ul><ul><ul><li>Hydraulic Action </li></ul></ul><ul><ul><li>Corrosion </li></ul></ul><ul><ul><li>TRANSPORTATION </li></ul></ul><ul><ul><li>Traction </li></ul></ul><ul><ul><li>Suspension </li></ul></ul><ul><ul><li>Solution </li></ul></ul>
  4. 4. <ul><ul><li>DEPOSITION </li></ul></ul><ul><ul><li>A river deposits its load when it has insufficient energy to carry it. This may be caused by: </li></ul></ul><ul><li>A decrease in the gradient (=a decrease in speed) </li></ul><ul><li>A widening or meandering of its channel </li></ul><ul><li>A decrease in volume (e.g. after a flood) </li></ul><ul><li>A decrease in velocity (speed) when it enters a lake or sea </li></ul>
  5. 5. Main physical features of a delta: <ul><li>Flat </li></ul><ul><li>Triangular in shape </li></ul><ul><li>Low lying </li></ul><ul><li>Alluvium </li></ul><ul><li>Marshy, colonised by marsh plants </li></ul><ul><li>Islands </li></ul><ul><li>Lagoons </li></ul><ul><li>Distributaries </li></ul>
  6. 6. Islands lagoons distributaries
  7. 7. Case study: Ganges delta Source of R. Ganges is in the Himalayas. The Ganges flows across its floodplain for over 1500km through N.India The Ganges delta is found at the mouth of the river as it flows into the Bay of Bengal The Indian city of Kolkata (Calcutta) lies on the western side of the delta. Most of the delta is in Bangladesh
  8. 8. Facts and figures <ul><li>These three rivers flow into the Ganges Delta: </li></ul><ul><li>Ganges ( Padma ) </li></ul><ul><li>Brahmaputra ( Jamuna ) </li></ul><ul><li>Meghna </li></ul><ul><li>It covers more than 105.000 km² </li></ul>
  9. 9. Reasons for the formation of the Ganges Delta: <ul><li>Material is eroded from the highlands </li></ul><ul><li>Deforestation also causes more sediment to be washed in to the river </li></ul><ul><li>Load is carried down stream </li></ul><ul><li>Flow of river slows down on reaching the sea </li></ul><ul><li>Deposition occurs </li></ul><ul><li>Sediment is deposited faster than the tides can remove it (tidal scour) </li></ul><ul><li>Deposits build up above sea level </li></ul><ul><li>River flow is blocked by so much deposition that he river splits up into distributaries </li></ul>
  10. 10. Past Exam Q’s <ul><li>2005 </li></ul><ul><li>Describe the main physical features of the area shown on the map (2marks) </li></ul><ul><li>Explain how the area has been formed. You may use diagrams to help your answer (6 marks) </li></ul><ul><li>1996 </li></ul><ul><li>Most of Bangladesh is part of the Ganges Delta. Describe the main physical features of a delta and explain how they are formed. You may use labelled diagrams if you wish (5 marks) </li></ul>