River morphology as_the_science_of_sustainability

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Extract of presentation "River morphology: the science of sustainability", held in Lalitpur, Nepal, 15 March 2012

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River morphology as_the_science_of_sustainability

  1. 1. River morphology:the science of sustainabilityErik Mosselman (extract of original presentation)A joint meeting on river morphology, sediment transport,catchment hydrology and flood forecasting issuesHimalaya Hotel, Lalitpur, Nepal, 15 March 2012
  2. 2. Nepal, 1985
  3. 3. Nepal, 1985
  4. 4. Fundamental concept: the Exner principle ∂zb dqs ∂u + =0 ∂t du ∂x erosionsedimentation erosion sedimentation top view side view of flow in channel with uniform widthof flow over horizontal bed
  5. 5. Application: river narrowing for navigation constriction
  6. 6. Application: river narrowing for navigation constriction
  7. 7. Application: river narrowing for navigation long-term equilibrium constriction
  8. 8. Application: river narrowing for navigation Bed degradation: advantage of lower flood levels?
  9. 9. Application: river narrowing for navigation navigation bottleneck
  10. 10. Application: river narrowing for navigationRiver bed degradation:• Limited depth above fixed layers• Restrictions for sluices and river port entrances• Instability of banks and hydraulic structures• Shift in discharge distribution at bifurcations• and for the Netherlands… angry Germans!
  11. 11. Application: river narrowing for navigationJohann Gottfried Tulla In derrule, no As a Regel, keinriver or Fluß oder Bach derin the stream Welt brauchtneeds world mehr als ein Bett more than one bed
  12. 12. Application: river narrowing for navigation Oberrhein below Basel 1828 1872 1963
  13. 13. Application: river narrowing for navigation Narrowing produced up to 10 m bed degradation
  14. 14. Application: river narrowing for navigation
  15. 15. Application: river narrowing for navigation Navigation impossible … Construction of lateral canal: Grand Canal d’Alsace
  16. 16. Application: river narrowing for navigation
  17. 17. Application: river narrowing for navigation
  18. 18. Application: river narrowing for navigation
  19. 19. Application: river narrowing for navigationLesson learned:River narrowing to improve navigability:• effective on a short term• leading to expensive measures to maintain navigability on a long term• due to river morphology
  20. 20. Application: water withdrawal for irrigation water withdrawal
  21. 21. Application: water withdrawal for irrigation water withdrawal
  22. 22. Application: water withdrawal for irrigation water withdrawal long-term equilibrium
  23. 23. Application: water withdrawal for irrigation water withdrawal
  24. 24. Application: water withdrawal for irrigation sedimentation: • rise in bed levels • rise in water levels water withdrawal
  25. 25. Application: water withdrawal for irrigation sedimentation: • rise in bed levels • rise in water levels • raised embankments
  26. 26. Application: water withdrawal for irrigation sedimentation: • rise in bed levels • rise in water levels • raised embankments
  27. 27. Application: water withdrawal for irrigation sedimentation: • rise in bed levels • rise in water levels • raised embankments
  28. 28. Application: water withdrawal for irrigation sedimentation: • rise in bed levels • rise in water levels • raised embankments flooding
  29. 29. Application: water withdrawal for irrigation Effect of water withdrawal made worse in case of barrages and subsidence flooding
  30. 30. Application: water withdrawal for irrigationLesson learned:Water withdrawal for irrigation:• lowers water levels on a short term• raises flood water levels on a long term• due to river morphology
  31. 31. Both applicationsLesson learned:Morphological effects on long term:• opposite to initial effects, hence easily overlooked• involving high costs
  32. 32. There is more to river morphology … RIVER MORPHOLOGY Bed sediment River shape composition Bed Bed Bank Bank degradation aggradation retreat advance
  33. 33. Nepalese river morphologistsSanjay Giri
  34. 34. Nepalese river morphologistsLochan Devkota Umesh Singh
  35. 35. Nepalese river morphologists
  36. 36. Nepalese river morphologists

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