120512 Iasi morphology part 2 - Mr Hendrik Havinga

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Morphological challenges: some Dutch examples.

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120512 Iasi morphology part 2 - Mr Hendrik Havinga

  1. 1. Morphological challenges: morphological impactresulting from the demands of the individual interests RESTORE – WORKSHOP Part 2 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)• River functions• Current situation (natural river, regulated river, physics)• Restoration measures problems (challenge..)• Mitigating measures• Monitoring• Maintenance• Administration processes
  3. 3. Mitigating measures/maintenance• Removal of vegetation• Dredging• Structural measures
  4. 4. Removal of vegetation• Cutting trees, etc.• Concept of cyclic rejuvenation in the floodplains – Measures are taken to restore the discharge capacity and increase natural diversity. These measures “rejuvenate” the area, e.g. silted up floodplains are excavated, on the bare ground pioneer vegetation will start to develop, thus restarting vegetation succession.
  5. 5. General concept of Cyclic Rejuvenation• Cyclic sediment- and vegetation management: solution to combine flood protection and ecological rehabilitation• Measures to restore the discharge capacity and to increase natural diversity, “rejuvenate” the area, e.g. excavation of silted up floodplains. On the bare ground pioneer vegetation will start to develop, thus restarting vegetation succession• Tailormade approaches• Demands: Expertise of hydraulics + morphology, ecological processes, flexibility
  6. 6. Design of Cyclic rejuvenation measures• Knowledge of ecological processes• Knowledge of river engineering• Socio-economic factors• Success factors – Legislation: Flood protection, dike stability, flora and fauna, forestry, bird- and habitat, environment, soil management, water pollution, Water Framework Directive (WFD). – Small environmental impact – Reduced maintenance. Innovative techniques are important: • Precise dealing with (contaminated) soil • Sub-suction of sand (leaving the top layer intact) • Complete removal of trees (including roots).
  7. 7. Cyclic rejuvenation of floodplainsUse of innovative techniques: Subsuction of sand
  8. 8. Dredging• ..and dumping to reduce bed erosion
  9. 9. Dredging instead of structural measures• Consequences of dredging: hampering of navigation, increase of maintenance, decrease of flood protection, CO2 emissions• However, dredging is cheaper than structural measures 9
  10. 10. Manners to cope with the situation1. Accept the consequences of dredging.2. Start with dredging operations and begin developing mitigating measures. In time reduce dredging efforts by executing structural measures3. Include mitigating structural measures in the Room for the River and WFD projects
  11. 11. 1. Accept the consequences• Natural banks and side channels will enforce dynamic river management concepts. This means regular monitoring of vegetation succession and morphological changes, checks of floodlevels and sailing depths. On an irregular basis maintenance is required.• Estimated increase in maintenance costs (Netherlands): 3 M Euro/year for 200 km of river, or 15,000 euro/km/yr.• 5-10 % of time the sailing depth’s will be less than optimal, leading to higher transport costs, estimated 15 M Euro/yr. This may effect a change in the transport modal split, i.e. more cargo by truck (>CO2).• If maintenance is neglected also flood safety is at stake.
  12. 12. 2. Start dredging, develop structural measures• Dredged material has to be redeposited in the low water bed, to limit further longitudinal bed erosion.• As dredging has become rather cheap, capitalisation of this maintenance results in limited capital for structural measures.• Reduction of dredging amounts are achieved by structural measures. Irrigation scheme solutions might help.• The dredged spoil and vegetation waste could be used to build temporariy structures that limit shoaling.
  13. 13. Structural measures• Groyne adaptations near inlets and outlets• Guide bunds• Longitudinal dams• Inlet structures
  14. 14. Mitigating measures to reduce impact of free• banks: Forebank protection, longitudinal dams, Island groynes
  15. 15. Example of temporary sructure
  16. 16. Groyne field protections made of vegetation
  17. 17. palenrij Doorsnedewilgenscherngeotextielsedimentvulling
  18. 18. The idea is to use these structures to minimise dredging, within a program called Self Supporting River System
  19. 19. The Self Supporting River System (SSRS)• Natural morpho-dynamics and available ‘spoil’ (sand and vegetation) are used to solve bottle-necks in a structural way• This leads to reduction of cost• The use of natural products like biomass, sand and clay is optimised to finance maintenance efforts
  20. 20. Maintenance according to• SSRS Small-scale changes in the river lay-out create a natural equilibrium locally (e.g. local constrictions)• SSRS means: search for the local natural equilibria that solve local problems• This is called “maintenance (building) with nature”,
  21. 21. SSRS-example: natural longitudinal• dam “Gabions” can be made from vegetation waste and dredged spoil• Estimated lifetime: 2-6-10 (?) years• Can be the basis for a tradional dam made of tissue and stone revetment, that is made later on, when more budget is available• In the meantime research can be carried out
  22. 22. Reduction of maintenance• Adequate design of structures/measures• No attitude “we will see what happens..”• Example of this attitude in next slides of Gameren side channels
  23. 23. Increasing flow conveyance : The Gameren floodplain June 2000
  24. 24. Upstream viewSouth and East channels
  25. 25. Downstream view South and West channels
  26. 26. Erosion at intakes
  27. 27. Erosion of groyne root
  28. 28. Dealing with side channels: limiting uncertaintiesApplying a Dynamic River Management System: – Quick-scan monitoring systems – Adequate Data storage and presention (GIS) – Impact assesment/design of measures using 2-D hydraulic and morphological models – Quick implementation of correcting measures
  29. 29. Use of inlet structures to limit sedimentload• Use sandtraps near the upstream end of side channels• Use surface screens and bottom vanes to direct the sediment to a preferred (dredging-) site.• Sills
  30. 30. Surface screen (‘bandall’)From MSc. Thesis of Siem Troost (TU-Delft):“Experimental research on the effects of surface screens on a mobile bed” 33
  31. 31. Solutions for intakes for side channels• Limited sediment inflow• No hampering of navigation• Moderate cost of construction and later adjustments
  32. 32. Sediment control methods CurativePreventive Overview of sediment handling methods (Eichenberger, 2001)
  33. 33. Preventive measuresSiting of intake at outer bend Intake at outer bend Alignment of intake
  34. 34. Sediment excluding methodsRaised entrance sill
  35. 35. Bottom vanesSubmerged vanes in front of intake Conceptual flow pattern
  36. 36. Vortex tubes Across the river Partially from the river bank Secondary channel Bed material River flowOther preventive measures:Skimming wallSloped training wallsBottom/surface deflectorsConcave- convex guide wallsUndersluicesTunnel (vortex) excludersBarrage regulation
  37. 37. Monitoring• Ecological monitoring• Vegetation succession (flood levels)• Morphology
  38. 38. Ecological monitoring• In the Netherlands a Hydromorphological monitoring handbook is used. Description of 45 parameters to monitor.• Some results from study ‘Rhine in the picture’ (Rijn in Beeld).
  39. 39. Project Ewijkse Plaat
  40. 40. Ewijkse PlaatSituation 1989
  41. 41. Vegetation changes 1992- 2009
  42. 42. Plan for extra channels
  43. 43. Gameren side channels Situation 1995
  44. 44. Actual situation
  45. 45. Developments inspecial plants1980-2009
  46. 46. Distribution ofspecial plants2009
  47. 47. Development in Waterplants and pioneervegetation since 1987
  48. 48. Developments in birds
  49. 49. Developments inBankswallows
  50. 50. Processes organisation
  51. 51. The increase of ecological potentials of riverbanks and floodplains requires:• Application of a Dynamic River Management System:• Changes in river administration methods (cooperation, active management)• Conditions for succes are: money, research, adequate river management, tailor made approaches
  52. 52. Dynamic River ManagementSeparate presentation: DRM explanation
  53. 53. Monitoring• Hydraulic monitoring: waterlevels and discharges through side channels. Indications for silting up.• Echo-sounding for bathymetry• Frequency of Monitoring
  54. 54. Detailpeilingen Slijk-Ewijk - km 889 - 891 - (-3.20m) 2-8-1998
  55. 55. Multibeam echolood meting • Kribben bij Haaften • November 2002 • Meetdienst DON1-11-2004
  56. 56. Parameter Mapping scale FrequencyVegetationThicket and Forest Visual survey 1 / yearVegetation structures 1:5.000 1/5 yearMorphologyBedlevel floodplain 1:5.000 1/10 year(includingembankments)Bedlevel of 1:5.000 1/5 yearsecondary channelsand lakesErosion near Visual survey After every highconstructions dischargeFrequency of Monitoring
  57. 57. Administration processes• Different responsibilities: – Terrain manager -> nature management – River manager -> reliable river works, flood protection, good inland navigation• So… Transparent communication is necessary• Expert team to bridge the gap!
  58. 58. Planning and design of projects• Use 1D and 2D morphological analyses• Projects in river system must be technically sound to safeguard all the functions of the river, otherwise opposition against river restoration may rise• Establish a masterplan with defined targets concerning: – The river’s dynamic equilibrium: bed levels, sedimenttransport capacities. – Navigation channel dimensions (width and Least Available Depth during low (5%) discharges). This requires a reference waterlevel going with this low discharge.• The impact of individual projects may not sustainably change these targets.
  59. 59. Discussion• What is the first thing you will discuss at home ?
  60. 60. End of part 2Thank you for your attention !
  61. 61. LiteratureBreen, L.E. van, Jesse, P, Havinga, H 2005: River restoration from a river manager’s point of view. In: Rehabilitating large regulated rivers, Proceedings of Lownland River Rehabilitation Conference (Archiv für Hydrobilologie), Wageningen, 2003. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart.Ghimire, B. 2003: No-regret solutions for intakes for secondary channels. M.Sc. Thesis. International Institute for Infrastructural, Hydraulic and Environmental Engineering (IHE), Delft.Havinga, H. & Smits, A.J.M. 2000. River management along the Rhine: a retrospective view. In: Smits, A.J.M., Nienhuis, P.H. & Leuven, R.S.E.W. (Eds.). New Approaches to River Management, Backhuys Publishers, Leiden, pp. 15-32Havinga, H. & Smits, A.J.M. 2000: River management along the Rhine: A retrospective view. In: Smits, A.J.M., Nienhuis, P.H. & Leuven, R.S.E.W. (Editors.) - New Approaches to River Management. Backhuys Publishers, Leiden.Peters, B., Kater, E., Geerling, G. 2006: Cyclic management in floodplains (in Dutch). Centrum voor Water en Samenleving, Radboud University, Nijmegen.PIANC, EnviCom Working Group 107 2009. Sustainable Waterways Within The Context of Navigation and Flood Management.PIANC, 2003. Guidelines for sustainable inland waterways and navigation, Report of working group 6.Sustainable Development of Floodplains, report: http://www.ecrr.org/sdfproject/sdfproject.htm

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