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120511 Iasi Morphology Mr Hendrik Havinga


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Morphological challenges: morphological impact resulting from the demands of the individual interests. some Dutch examples

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120511 Iasi Morphology Mr Hendrik Havinga

  1. 1. Morphological challenges: morphological impactresulting from the demands of the individual interests. RESTORE – WORKSHOP Part 1 Sharing River restoration knowledge and experience in Europe, Iaşi-ROMANIA, 9-11 May 2012 Hendrik Havinga 1 Dutch Ministry of Infrastructure and Environment Rijkswaterstaat Oost Nederland
  2. 2. River restoration topics• Goals (increase bio-diversity, WFD)• River functions• Current situation (natural river, regulated river, physics)• Restoration measures problems (challenges..)• Mitigating measures• Monitoring• Maintenance• Administration processes
  3. 3. The river and its user functionsPrimary functionAdded functions
  4. 4. Regulated River The Waal River, NL
  5. 5. The Primary function (safe discharge of water, ice and sediment)Discharge control at Pannerden Weir 1993 flood in Waal River at KekendomBridge upstream city of Kampen, 1996
  6. 6. New levee after breach, Dongting Lake , 1998Sedimentation in branch of Yangtze River in Dongting area
  7. 7. Added functions
  8. 8. Current situation, Rhine example• Historical developments• Today
  9. 9. Rhine River catchment Istein
  10. 10. The Oberrhein in early days...(at Istein) Basel
  11. 11. View at Istein today.. Restrhein + Canal d’Alsace
  12. 12. The OberrheinRegulering regulation
  13. 13. River regulation German Oberrhein Johan Gottfried Tulla
  14. 14. River training: also closing of side channels
  15. 15. Dike failure through ice dams (may very well start on shoals, at side channel inlets)
  16. 16. River Regulation MeasuresMeasure Hydromorphological effectSingular groynes (jetties) Width reductionDikes (Levees) “Normalisation “Bend cut-off River shorteningLocks and dams Sediment withdrawalDeforestation Sediment supply
  17. 17. The regulated riverlevee floodplain fairway summerdike groyne Why this lay-out ?
  18. 18. LAY-OUT PREFERENCESInterest Geography Defenses HydrologySAFETY Summer dikes "armoured" guarding max. design water-AG AINST Winter dikes constructions levels and dischargeFLOODING Groynes (ice) rock distributionsNAVIGATION summer dikes "armoured" up to 4,0 m waterdepth: Deep minor bed constructions total discharge through minor rock bed.AGRICULTURE summer dikes "armoured" no flooding polder dikes constructions grass no natural vegetationECOLOGY summer dikes with "soft" frequent flooding inlets and outlets constructions secondary no rock channels Natural vegetation
  19. 19. The regulated riverlevee floodplain fairway summerdike groyneImpact of levees, dikes and groynes ?
  20. 20. Width reductiontop view Flow direction l leve W aterlongitudinal view Bed
  21. 21. short term effects of width reductiontop view Flow direction l leve W aterlongitudinal view Bed
  22. 22. Final effects of width reductiontop view Flow direction l leve W aterlongitudinal view l leve Bed
  23. 23. Bend cut-offtop view n irectio F low d A B vel Water lelongitudinal view Bed B A
  24. 24. Short term effects of Bend cut-offtop view n irectio F low d A B W ater leve llongitudinal view Bed B B A
  25. 25. Final effects of bend cut-offtop view n irectio F low d A B W ater leve llongitudinal view Bed le vel B B A
  26. 26. Dam in the rivertop view Flow direction level waterlongitudinal view Bed
  27. 27. Short term effects of dam in the rivertop view Flow direction level Waterlongitudinal view Bed
  28. 28. Long term effects of dam in the rivertop view Flow direction level waterlongitudinal view el Bed lev
  29. 29. Side-effect of regulation works: increased flood levels Q 8000 m3/s Worms ΔQ = 1820 m3/s Maxau Δt = - 45 hrΔQ = 1100 m3/s Δt = - 45 hr Maxau 1882/1883 4000 1995 Worms 1882/1883 1995 2000 Flood wave Oberrhein 0 t 1 2 3 4 5 6 7 8 9 10
  30. 30. • Dutch Rhine
  31. 31. Other side-effect: Bed degradation (Waal River) Ochten Hulhuizen IJzendoorn Dodewaard Haalderen Tiel Ben. Leeuwen Gorinchem Pann. Kop Herwijnen Haaften Opijnen Dreumel Erlecom Nijmegen Zaltbommel St.-Andries seasedimentation dredging z: 2 cm/year turning pointerosion
  32. 32. The regulated river levee floodplain fairway summerdike groyneRegulation led to increase of flood levels and severe bed erosionAlso nature values have been harmed
  33. 33. Today’s major river projects in the Netherlands• Room for the River Program: – Lower flood levels – Some 40 measures to increase flood conveyance (400 km) – Increase of landscape quality • Natural vegetation, side channels – Ready in 2015 – Budget € 2.3 billion• European Water Framework Directive (WFD): – Good Ecological Potential – Only banks and floodplains can help
  34. 34. Overview of Room for the River projectsites
  35. 35. Room for the River measuresMeasures with ecological potential
  36. 36. WFD Project scope for central and eastern NL until 2015 95 ha floodplain lowering 25 km secondary channel 2-sided IJssel 8 km secondary channel 1-sided 60 km ecological river banks 15 ha shallow reed zonesL. Rhine-Lek 41 fish passages Waal Budget 130 80 million € Postponement of measures after 2015
  37. 37. Many projects Example IJssel River (120 km)
  38. 38. Restoration measures
  39. 39. Normalised Rivers : hydromorphologicalpressures Groynes narrow main channel and prevent lateral migration Main channels incise Floodplains aggrade All large rivers are designated as heavily modified and can only to a limited part be rehabilitated
  40. 40. Types of measures for ecological improvement for fish, macrofauna and waterplantsTheme MeasureRestoration of habitats and natural Ecological banks dynamics Connecting lakes to rivers• Shallow areas, low flow velocity Construction of secondary channels• Protected from waves from ships Lowering of floodplains• Variation in conditions (substrate, flow velocity, water depth)• Sandy banks with a gradual slopeRemove barriers for fish migration Construction of fish passages• Connect rivers and brooks Rehabilitation of mouth of brooks• Connect fresh and marine waters Introduction of seeds of water plantsClear and clean water Creation of shelter by e.g. a dam
  41. 41. Ecological river bankActualPlan
  42. 42. Erosion from ecologicalriver bank Sedimentation in navigation channel Concern from navigation sector Morphological study
  43. 43. Secondary channels Waal channel Amerongseand Nederrijn-Lek Bovenpolder 5,8 km Gameren Maintenance Vreugdenrijkerwaard - Sedimentation in main and secondary channel - Vegetation
  44. 44. Fish passage Weirs Nederrijn
  45. 45. Restore connection for fishmigration between rivers andbrooksPumping station winde Mouth of brook 45
  46. 46. Assignment• Group divided in 4 subgroups – Discuss of your home situation, executed/planned restoration measures and problems – Give short outline on flipoverflaps• Results will be presented tomorrow• Possible rearrangement of content
  47. 47. Results of the assignment
  48. 48. Restoration measures problems (challenges..)• Free banks• Side channels
  49. 49. Removal of bank defenses and re- introduction of side channels may present management problemsRiver restoration measures – Natural vegetation – Free banks – Side channels
  50. 50. Natural vegetation decreases flood protection
  51. 51. Example: longitudinal dam in groyne fields (prevents erosion, increases fairway) (Waal River near Opijnen)
  52. 52. Side channel through groynes = fish passage
  53. 53. Vegetation DevelopmentOpijnen 1992
  54. 54. Vegetation DevelopmentOpijnen 2003
  55. 55. Intervention and Monitoring ??? What is the right moment to intervene ?Quality: flood protection level, sailing depth, stability, ecological potential,..
  56. 56. Historical bank erosion (by cattle and ships)was reason for bank protection 56
  57. 57. Removal of bank protection (right bank) at Engelse Werk (Zwolle) dynamic land- water gradient • Removal of rip rap, construction of new groynes • Sandy banks, tolerated bank erosion • In time accretion in navigation channel IJssel Engelse werkphoto: B. Boekhoven
  58. 58. Engelse werk, 13 years later 16 m (16 m in 1995-2001) 28 m (8 m in 1995-2001)21 m (12 m in 1995-2001) Original bank February 2008
  59. 59. Increased morphodynamics sedimentation during flood Initial outflanking of groynesbank erosion by wave attackMore various macrofauna communities
  60. 60. Side channel in the Klompenwaard (Waal River near bifurcation Pannerden)
  61. 61. Bakenhof dike set-back,Nederrijn River, 2000near bifurcation Westervoort
  62. 62. Impact on lowPlan Westenholte:Lowered flood plains + side channel water bedAggradation of bend First shoal Flood shoal Increased flood levels Hindrance to navigation
  63. 63. Morphological effects on main channel (1/3)elevation(m+NAP) gradualflow velocity acceleration abrupt (m/s) deceleration abrupt gradual acceleration decelaration
  64. 64. Morphological effects on main channel (2/3) gradual acceleration abrupt flow velocity deceleration (m/s) abrupt gradual acceleration decelaration sedimentation frontinitial bed level changes (m/day) sedimentation erosion erosion expansion wave
  65. 65. Morphological effects on main channel (3/3) sedimentation frontinitial bed level changes sedimentation (m/day) erosion erosion expansion wave elevation (m+NAP)
  66. 66. Gameren
  67. 67. Side channel (Waal River near Gameren)
  68. 68. Aggradation main channel as planned (2 dm, channel discharges < 3%). Local erosion at groyne roots and transfer zones undefended/defended banks West channel East channelLarge channel
  69. 69. Computed bed level respons Gameren (2 dimensional morphological model Delft3DMOR, repeated yearly hydrograph)Deltares (former WL Delft Hydraulics, 2004)
  70. 70. Control principles for side channels (from) MSc Study of Mr. Bhuban Ghimire S control (local) student at UNESCO-IHE Delft (2003), titled: “No-regret” solutions for intakes for side channels Quantity of Sediment Entering Q control (local) Channel Stability Sediment Transport Increasing sediment size Increasing slope capacityRiver X-section controlWaal (whole channel) Degradation Aggradation Secondary Sediment load Water discharge Channel Lane’s Balance
  71. 71. Control principles.. Sediment distributionHydraulic control Sediment control Sediment Sediment Transp. Cap. distribution distribution ΔS(Qcontrol)⎛ S sc ⎞ ⎛ S sc ⎞ ΔS (S control)⎜ ⎟ ⎜ ⎟⎜ SW ⎟ ⎜S ⎟⎝ ⎠ ⎝ W⎠ Transport capacity ⎛ Q sc ⎞ ⎛Q ⎞ ⎜ ⎟ ⎜ sc ⎟ ⎜Q ⎟ Cross-section control ⎜Q ⎟ ⎝ W ⎠ Sediment transport capacities ⎝ W ⎠ for different channel sections Normal channel ⎛ S sc⎞ Deep ⎜ ⎟ channel ⎜ SW ⎟ ⎝ ⎠ Wide channel ⎛ Q sc ⎞ ⎜ ⎟ ⎜Q ⎟ ⎝ W ⎠
  72. 72. End of part 1 72