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Large-Scale Coastal Maintenance using Sand Experiences and Experiments in The Netherlands

Large-Scale Coastal Maintenance using Sand Experiences and Experiments in The Netherlands. MODEG meeting, March, 11, 2011 Ad van der Spek. Content. Introduction Coastal system of The Netherlands Coastal maintenance using sand fighting structural erosion ! Results coastal maintenance

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Large-Scale Coastal Maintenance using Sand Experiences and Experiments in The Netherlands

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  1. Large-Scale Coastal Maintenance using SandExperiences and Experiments in The Netherlands MODEG meeting, March, 11, 2011 Ad van der Spek

  2. Content • Introduction • Coastal system of The Netherlands • Coastal maintenance using sand • fighting structural erosion ! • Results coastal maintenance • Future developments • Lessons learned, experiments • data needs • Concluding remarks Coastal Maintenance in The Netherlands

  3. Introduction: sand budget Coastal Maintenance in The Netherlands

  4. Introduction: coastal cells Coastal Maintenance in The Netherlands

  5. Introduction: coastal profile in dynamic equilibrium Active coastal zone Coastal Maintenance in The Netherlands

  6. The Netherlands: sandy coast 350 km • Amsterdam Netherlands • The Hague Coastal Maintenance in The Netherlands March 11, 2011 6

  7. How were The Netherlands built? Coastal Maintenance in The Netherlands

  8. Long-term coastal evolution • supply > demand : • regression • Demand tidal basin • vs. • Supply coast • supply < demand : • transgression Coastal Maintenance in The Netherlands

  9. 5000 BP 2600 BP Paleo-geographyofThe Netherlands demand <supply demand > supply Coastal Maintenance in The Netherlands

  10. 2. 1. 4. 3. 2. Holocene sediment budget sources & sinks Coastal Maintenance in The Netherlands

  11. Total volume Holocene coastal deposits • ( in billion m3 ) • lithology volume percentage • ---------------------------------------------------------------------------------- • sand 151 - 157 67 -70 % • mud 59 - 65 26 - 29 % • peat 11 5 % • ---------------------------------------------------------------------------------- • Total 226 100 % Coastal Maintenance in The Netherlands

  12. Holocene sediment budget - Infilling with time No longer natural large-scale sediment accumulation • period perc. volume vol. / yr • (billion m3) (million m3) • ---------------------------------------------------------------------------------------- • 8000-5000 BP 60 % 136 41 • 5000-3000 BP 30 % 67 27 • Since 3000 BP 10 % 23 7 • ---------------------------------------------------------------------------------------- “The Hague, we have a problem !” Coastal Maintenance in The Netherlands

  13. Wadden Sea Coastal Foundation Western Scheldt Sediment balance Dutch coast Coastal Maintenance in The Netherlands

  14. Solution: we do it ourselves !! Keeping up by nourishing sand Coastal Maintenance in The Netherlands

  15. What to do ? • Coastal Maintenance Programme • Yearly monitoring of coastline: jarkus • Bring sand where you need it • Yearly nourishment budget: 12 Mm3 sand • Why nourishing sand? • Compensating sand deficit • Feeding sediment fluxes • Building sand buffer Coastal Maintenance in The Netherlands

  16. 350 km • Amsterdam Soft sea defence Coastal Maintenance in The Netherlands

  17. Why nourishing? • Fighting structural erosion • Sand balance Dutch coast negative • 1965-1990: -6,5 Mm3 / yr • Dynamic Maintenance (preferably sand…) • Reinforcing the coast • upfront compensation SLR • upscaling: mega-nourishments, Sand Engine • Land reclamation • near future ? Coastal Maintenance in The Netherlands

  18. How to nourish ? • Beach • Shoreface • Channel • Combinations Future: directing natural processes ? Coastal Maintenance in The Netherlands

  19. Nourishment policy since 1990 1990 – 2000: 6Mm3/year 2001 - : 12 Mm3/year Coastal Maintenance in The Netherlands

  20. Result 1: coast line position maintained Coastal Maintenance in The Netherlands

  21. Result 2: outbuilding of coastal dunes !! Noordwijk aan Zee Katwijk aan Zee Wassenaar Coastal Maintenance in The Netherlands

  22. pro-active nourishment approach is succesfull dune growth 1998 - 2007 from: Arens, 2010 Coastal Maintenance in The Netherlands

  23. Prograding dune at Bergen aan Zee today 1990 Coastal Maintenance in The Netherlands

  24. MSL dunes dunes - 20m beach days / meters shore face residual strength Safety against flooding Coastal Maintenance in The Netherlands

  25. SustainableSafety against flooding pro-active nourishment policy dunes days / meters residual strength coast line years / km basal coast line MSL - 20m coastal foundation coastal foundation decades – centuries / 10’s – 100’s km Coastal Maintenance in The Netherlands

  26. Conclusion: • The balance concept works • sea-level rise ≠ coastal erosion ! • Outbuilding: we can tip the balance • Future: maintaining coast with sand • Strict monitoring: • Coastline position: decision on nourishing • Development shoreface nourishments: learning • Coastal foundation: yes, but how ?? Coastal Maintenance in The Netherlands

  27. Wadden Sea Coastal Foundation Western Scheldt Coastal Foundation active sand sharing coastal system Coastal Maintenance in The Netherlands

  28. Challenge: explore feasible ways of upscaling 12 Mm3/year 20 Mm3/year 85 Mm3/year Coastal Maintenance in The Netherlands

  29. Building a sand buffer … Coastal Maintenance in The Netherlands

  30. Kijkduin 2 Coastal Maintenance in The Netherlands

  31. The new Delfland coast Coastal Maintenance in The Netherlands

  32. Pilot Sand Engine Holland Coast Sand Engine • Surplus of sand, distributed by tide/waves/wind • 20 mln m3 • Initial design: Ca 100-150 ha, • 1000 m seaward • Total budget 70 Meuro • Realisation planned 2010-2011 Artist impression www.kustvisiezuidholland.nl/zandmotor Coastal Maintenance in The Netherlands

  33. Joint initiative: Province National government Water Board Local authorities NGO’s Pilot Sand Engine ambition agreement • Co-financing: • 17 % • 83 % Coastal Maintenance in The Netherlands

  34. Sand Engine objectives • Long-term: guarantee coastal safety by promoting dune development • Medium-term: knowledge development, innovation • Short-term: create space for nature and/or recreation Coastal Maintenance in The Netherlands

  35. (zeetorenhvh) Sand Engine design • Dynamic design ( not a well defined end result ) • Dynamic optimization of different functions • Balance between long term benefits (safety against flooding) and short term benefits (nature and recreation) • Challenge: management of expectations with different stakeholders Coastal Maintenance in The Netherlands

  36. Monitoring and evaluation • monitoring • morphology • hydrology • ecology • tourism • management risks • evaluation • 5 years: 2015 • 10 years: 2020 • 20 years: 2030 (zeetorenhvh) Coastal Maintenance in The Netherlands

  37. Lessons learned (1): data needs • System analysis • Reconstruction coastal evolution • Sediment balance • Volume nearshore sand resources • Information enables design maintenance strategy • Monitoring • Relative sea-level rise • Coastal state (yearly) • Frequent monitoring large nourishments (learning by doing) Coastal Maintenance in The Netherlands

  38. Lessons learned (2): sand as a resource • Sufficient nearshore sand resources only on certain stable broad shelves • In other cases sand resources insufficient or sufficient only for nourishing coastal hot spots • For most shelves sand resources have not yet been investigated Coastal Maintenance in The Netherlands

  39. Sea-level low-stand river deposits • Sand deposits can be unexploitable: • too far from the coast • at too deep water • buried under non-sandy sediments Coastal Maintenance in The Netherlands

  40. Global nearshore sand resources Sand resource > 1 km3 / 100 km Sand resource between 0,1 and 1 km3 / 100 km Coastal Maintenance in The Netherlands

  41. Lessons learned (3) • Learning by doing: • Step by step • Co-operation with other countries • EU-programmes: • NOURTEC: shoreface nourishing • COAST3D: nearshore processes • SANDPIT: effects of sand extraction • SAFECOAST, EUROSION, CONSCIENCE etc. • Data availability • Central storage? • Flexible formats? • Fitting in relevant, extra information • Monitoring programmes or project-related acquisition? Coastal Maintenance in The Netherlands

  42. Concluding remarks: What is nourishing ? • Compensation of sand deficits • Feeding of sediment fluxes • Building a sand buffer • Flexible • Tailor-made • Relatively cheap • Swift reaction to unexpected changes Coastal Maintenance in The Netherlands

  43. Concluding remarks • Analysis sediment balance crucial • Available resources? • Sand volume? • potential resources? • sand captured in reservoirs • restoring sediment supply • Sand Engine experiment • case study for european coastal community? Coastal Maintenance in The Netherlands

  44. Thank you for your attention ! Coastal Maintenance in The Netherlands

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