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Meandering Rivers

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Umer Khayam
Umer Khayam

Meandering rivers form sinuous patterns as they erode the outer banks of bends and deposit sediments inside bends. This process causes the river channel to migrate back and forth over time. Key features of meandering rivers include point bars, which are sediment deposits inside bends, and oxbow lakes, which form when meander loops are cut off from the main river channel. Meandering rivers have a single channel and flow in helical patterns that erode the outer bank and deposit sediments inside bends, causing the characteristic sinuous shape over time.

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MEANDERING RIVERS UMER KHAYAM FINAL YEAR (Eve)
MEANDERING STREAM A stream consisting of successive Meanders A  meander  in general is a bend in a sinous watercourse.
FORMATION A meander is formed when the moving water in a river erodes the outer banks and widens its valley. 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. The result is a  snaking  pattern as the stream meanders back and forth across its down-valley axis.
Point bar deposits Thalweg
MORPHOLOGY It occupies a position downstream from braided streams and upstream from deltas in fluvial system They are most commonly formed in coastal plain regions They are characterized by single channel in contrast to multichannel braided streams
MORPHOLOGY Meander develops as a result of disruption in uniform flow across the channel Caused by variation in; Sediments Slope or Gradient Bed roughness etc... The channel profile comprises of a steep side & a gently sloping side relative to stream bed The steep side experiences lateral erosion and gently sloping side is characterised by sedimentation
EROSION & DEPOSITION Point bar deposits } Meander loop Cut Bank
PROCESSES They are characterized by turbulent flow; velocity varies both horizontaly & vertically across the channel It transport the material both as bed load and wash load Unlike braided streams, meandering streams provides a regular pattern of flow There is a consensus about the flow in meanders which may be ellaborated as;
FLOW IN MEANDERS Helical Flow It is the major flow in the meander bends. This flow causes an elevation of water level on the outside of meander 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 This has the net effect of producing a circulation cell which interects with the bed to carry sediments upslope along the accretion surface
 
FEATURES There are numerous environments & subenvironments related to meandering streams; each having characterstic deposits These include; Channel Lag Point Bar Overbank Deposits Natural Levees Crevasse-splays Flood Basin Deposits
DEPOSITS OVERVIEW
FEATURES Point Bar The sediments accumulatation on the convex side of the meandering loop results in the formation of characteristic point bar Most of the sedimentation occurs inthe form of point bar
FEATURES OxBow Lake Oxbow lakes  are created when growing meanders intersect each other and cut off a meander loop, leaving it without an active cutting stream. Over a period of time, these oxbow lakes tend to dry out or fill in with sediments
 
Maximum erosion Maximum deposition FORMATION SEQUENCE OF OXBOW LAKES
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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

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