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Jaap Kwadijk Director of Science Deltares

Science & Tools: Effectiveness and Multiple Benefits of Natural Defenses/Infrastructure: How Does It Stack Up Against and Integrate with Built Infrastructure Dutch experiences. Jaap Kwadijk Director of Science Deltares. Flood risk in The Netherlands. 2/3 flood-prone, 9 million inhabitants,

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Jaap Kwadijk Director of Science Deltares

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  1. Science & Tools: Effectiveness and Multiple Benefits of Natural Defenses/Infrastructure: How Does It Stack Up Against and Integrate with Built InfrastructureDutch experiences Jaap KwadijkDirector of Science Deltares

  2. Flood risk in The Netherlands 2/3 flood-prone, 9 million inhabitants, 65% GNP, 1800 billion € invested value Economically Efficient Flood Protection Standards

  3. All generations have their own flood) 1675 1682 1916 1953

  4. Before 1995, Dutch reaction built infrastructure 4

  5. 1995, a transistion, Room for the River ?

  6. New solutions to prevent floods New standards  fail proof, multifunctional Deltadikes? Building with nature, sand engine, oyster reefs (eco engineering)

  7. Focus on ecosystem-based eco-engineering Why should we make use of natural processes and ecosystem services in flood risk mitigation (in combination with hard engineering)? • Cost reduction • Reduces risk on failure • Adaptable

  8. Dutch historical large scale land reclamation = building with nature Marshland kwelders • Foto paesens-moddergat Effective low cost low tech saltmarshproduces safety & large natural value

  9. soft eco-engineering dike concept with reef, marsh, dune combinations Not safe enough? Sandy foreshore needs nourishment safe Marshes/ mangroves reefs Very safe Long term safety: Marshes grow with SLR

  10. Wavereducing forest-dike combi ‘fort Steurgat’ Clay dike will be lower than traditional design 100m wide Wave reducingwillow-tree plantations Low cost low tech Deltares/RWS concept achieves required 1/2000 safety standards and now under construction

  11. Muddy coast Soft Safe Dike: saltmarsh/dune/dike hybrid Existing dike • Vegetatie als golfremmer Wave reducing saltmarsh Super storm stable vegetated dune Hinterland Saltmarsh grows with sea level and maintains stability and safety Flexible, low tech, low maintenance cost, longshore connectivity Muddy coastline Old dike 500m

  12. Artificial oyster reefs Oyster reefs as a short / midterm solution for erosion problem in the Oosterschelde Small scale pilot 2009 Large scale pilot 2010 Each reef: 400 m3, ± 230 tons of oyster shells 200 x 10 m 12 x 4 m

  13. Sand Engine to cope with SLR: Experiment Observed evolution (1st year)

  14. Measured / predicted evolution (Delft3D) D3D Model prediction 20 years (pre-project) Initial Measured bathymetry after 1 year After 3 year After 5 years After 10 years After 20 years Figures courtesy of Rijkswaterstaat / Shore Monitoring & Research

  15. Problem: Safest delta in the world • By law (water act): • Extremely high safety standards • Maintenance of the structures • Detailed standards on flood prevention structures

  16. Pro’s and con’s • Some are extremely efficient examples (sand nourishment) • Some are probably effective • Potentially more adaptable • Potentially multi purpose • Not clear how effective the measures are • No handbooks on design and evaluation • Not considered as “engineering” • Not “one size fits many” • Legal risk to implement them

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