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MEANDERING RIVERS UMER KHAYAM FINAL YEAR (Eve)
MEANDERING STREAM <ul><li>A stream consisting of successive Meanders </li></ul><ul><ul><li>A  meander  in general is a ben...
FORMATION <ul><li>A meander is formed when the moving water in a river erodes the outer banks and widens its valley.  </li...
Point bar deposits Thalweg
MORPHOLOGY <ul><li>It occupies a position downstream from braided streams and upstream from deltas in fluvial system </li>...
MORPHOLOGY <ul><li>Meander develops as a result of disruption in uniform flow across the channel </li></ul><ul><li>Caused ...
EROSION & DEPOSITION Point bar deposits } Meander loop Cut Bank
PROCESSES <ul><li>They are characterized by turbulent flow; velocity varies both horizontaly & vertically across the chann...
FLOW IN MEANDERS <ul><li>Helical Flow </li></ul><ul><ul><li>It is the major flow in the meander bends.  </li></ul></ul><ul...
 
FEATURES <ul><li>There are numerous environments & subenvironments related to meandering streams; each having charactersti...
DEPOSITS OVERVIEW
FEATURES <ul><li>Point Bar </li></ul><ul><ul><li>The sediments accumulatation on the convex side of the meandering loop re...
FEATURES <ul><li>OxBow Lake </li></ul><ul><ul><li>Oxbow lakes  are created when growing meanders intersect each other and ...
 
Maximum  erosion Maximum  deposition FORMATION SEQUENCE OF OXBOW LAKES
Stage # 1
Stage # 2
Stage # 3
Stage # 4
Stage # 5
Stage # 6
Stage # 7
Stage # 8
Stage # 9
Oxbow Lake Oxbow  cuttoff Meander scars Final Stage
QUESTIONS & ANSWERS From Professor M.Haneef The honourable Chairman!
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Meandering Rivers

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Transcript of "Meandering Rivers"

  1. 1. MEANDERING RIVERS UMER KHAYAM FINAL YEAR (Eve)
  2. 2. MEANDERING STREAM <ul><li>A stream consisting of successive Meanders </li></ul><ul><ul><li>A  meander  in general is a bend in a sinous watercourse. </li></ul></ul>
  3. 3. FORMATION <ul><li>A meander is formed when the moving water in a river erodes the outer banks and widens its valley. </li></ul><ul><li>A stream of any volume may assume a  meandering  course, alternatively eroding sediments from the outside of a bend and depositing them on the inside. </li></ul><ul><li>The result is a  snaking  pattern as the stream meanders back and forth across its down-valley axis. </li></ul>
  4. 4. Point bar deposits Thalweg
  5. 5. MORPHOLOGY <ul><li>It occupies a position downstream from braided streams and upstream from deltas in fluvial system </li></ul><ul><li>They are most commonly formed in coastal plain regions </li></ul><ul><li>They are characterized by single channel in contrast to multichannel braided streams </li></ul>
  6. 6. MORPHOLOGY <ul><li>Meander develops as a result of disruption in uniform flow across the channel </li></ul><ul><li>Caused by variation in; </li></ul><ul><ul><li>Sediments </li></ul></ul><ul><ul><li>Slope or Gradient </li></ul></ul><ul><ul><li>Bed roughness etc... </li></ul></ul><ul><li>The channel profile comprises of a steep side & a gently sloping side relative to stream bed </li></ul><ul><li>The steep side experiences lateral erosion and gently sloping side is characterised by sedimentation </li></ul>
  7. 7. EROSION & DEPOSITION Point bar deposits } Meander loop Cut Bank
  8. 8. PROCESSES <ul><li>They are characterized by turbulent flow; velocity varies both horizontaly & vertically across the channel </li></ul><ul><li>It transport the material both as bed load and wash load </li></ul><ul><li>Unlike braided streams, meandering streams provides a regular pattern of flow </li></ul><ul><li>There is a consensus about the flow in meanders which may be ellaborated as; </li></ul>
  9. 9. FLOW IN MEANDERS <ul><li>Helical Flow </li></ul><ul><ul><li>It is the major flow in the meander bends. </li></ul></ul><ul><ul><li>This flow causes an elevation of water level on the outside of meander </li></ul></ul><ul><ul><li>This helical flow produces a component of flow which is normal to stream bank; towards the eroding bank near the surface and towards the accreting bank near the bottom </li></ul></ul><ul><ul><li>This has the net effect of producing a circulation cell which interects with the bed to carry sediments upslope along the accretion surface </li></ul></ul>
  10. 11. FEATURES <ul><li>There are numerous environments & subenvironments related to meandering streams; each having characterstic deposits </li></ul><ul><li>These include; </li></ul><ul><ul><li>Channel Lag </li></ul></ul><ul><ul><li>Point Bar </li></ul></ul><ul><ul><li>Overbank Deposits </li></ul></ul><ul><ul><li>Natural Levees </li></ul></ul><ul><ul><li>Crevasse-splays </li></ul></ul><ul><ul><li>Flood Basin Deposits </li></ul></ul>
  11. 12. DEPOSITS OVERVIEW
  12. 13. FEATURES <ul><li>Point Bar </li></ul><ul><ul><li>The sediments accumulatation on the convex side of the meandering loop results in the formation of characteristic point bar </li></ul></ul><ul><ul><li>Most of the sedimentation occurs inthe form of point bar </li></ul></ul>
  13. 14. FEATURES <ul><li>OxBow Lake </li></ul><ul><ul><li>Oxbow lakes  are created when growing meanders intersect each other and cut off a meander loop, leaving it without an active cutting stream. </li></ul></ul><ul><ul><li>Over a period of time, these oxbow lakes tend to dry out or fill in with sediments </li></ul></ul>
  14. 16. Maximum erosion Maximum deposition FORMATION SEQUENCE OF OXBOW LAKES
  15. 17. Stage # 1
  16. 18. Stage # 2
  17. 19. Stage # 3
  18. 20. Stage # 4
  19. 21. Stage # 5
  20. 22. Stage # 6
  21. 23. Stage # 7
  22. 24. Stage # 8
  23. 25. Stage # 9
  24. 26. Oxbow Lake Oxbow cuttoff Meander scars Final Stage
  25. 27. QUESTIONS & ANSWERS From Professor M.Haneef The honourable Chairman!
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