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

Content 1.Introduction 2.Coastal system of The Netherlands 3.Coastal maintenance using sand fighting structural erosion ! 4.Results coastal maintenance 5.Future developments 6.Lessons learned, experiments data needs 7.Concluding remarks March 11, 2011Coastal Maintenance in The Netherlands2

March 11, 2011Coastal Maintenance in The Netherlands3 Introduction: sand budget

March 11, 2011Coastal Maintenance in The Netherlands4 Introduction: coastal cells

March 11, 2011Coastal Maintenance in The Netherlands5 Introduction: coastal profile in dynamic equilibrium Active coastal zone

March 11, 2011Coastal Maintenance in The Netherlands6 The Netherlands: sandy coast 350 km Amsterdam Netherlands The Hague

March 11, 2011Coastal Maintenance in The Netherlands How were The Netherlands built? 7

March 11, 2011Coastal Maintenance in The Netherlands Long-term coastal evolution supply > demand : regression Demand tidal basin vs. Supply coast supply < demand : transgression 8

March 11, 2011Coastal Maintenance in The Netherlands Paleo-geography of The Netherlands 5000 BP demand > supply 2600 BP demand < supply 9

March 11, 2011Coastal Maintenance in The Netherlands Holocene sediment budget sources & sinks 10

March 11, 2011Coastal Maintenance in The Netherlands11 Total volume Holocene coastal deposits ( in billion m3 ) lithologyvolumepercentage sand % mud % peat115 % Total %

March 11, 2011Coastal Maintenance in The Netherlands Holocene sediment budget - Infilling with time periodperc.volumevol. / yr ( billion m 3 ) ( million m 3 ) BP60 % BP30 %6727 Since 3000 BP10 % “The Hague, we have a problem !”

March 11, 2011Coastal Maintenance in The Netherlands13 Sediment balance Dutch coast Western Scheldt Coastal Foundation Wadden Sea

March 11, 2011Coastal Maintenance in The Netherlands Solution: we do it ourselves !! Keeping up by nourishing sand 14

March 11, 2011Coastal Maintenance in The Netherlands15 What to do ? Coastal Maintenance Programme Yearly monitoring of coastline: jarkus Bring sand where you need it Yearly nourishment budget: 12 Mm 3 sand Why nourishing sand? 1.Compensating sand deficit 2.Feeding sediment fluxes 3.Building sand buffer

March 11, 2011Coastal Maintenance in The Netherlands16 Soft sea defence 350 km Amsterdam

March 11, 2011Coastal Maintenance in The Netherlands17 Why nourishing? 1.Fighting structural erosion Sand balance Dutch coast negative : -6,5 Mm 3 / yr Dynamic Maintenance (preferably sand …) 2.Reinforcing the coast upfront compensation SLR upscaling: mega-nourishments, Sand Engine 3.Land reclamation near future ?

March 11, 2011Coastal Maintenance in The Netherlands18 How to nourish ? 1.Beach 2.Shoreface 3.Channel 4.Combinations Future: directing natural processes ?

March 11, 2011Coastal Maintenance in The Netherlands Nourishment policy since – 2000: 6 Mm 3 /year : 12 Mm 3 /year 1990 – 2000: 6 Mm 3 /year : 12 Mm 3 /year 19

March 11, 2011Coastal Maintenance in The Netherlands Result 1: coast line position maintained 20

March 11, 2011Coastal Maintenance in The Netherlands21 Result 2: outbuilding of coastal dunes !! Wassenaar Katwijk aan Zee Noordwijk aan Zee

March 11, 2011Coastal Maintenance in The Netherlands dune growth pro-active nourishment approach is succesfull from: Arens,

March 11, 2011Coastal Maintenance in The Netherlands today1990 Prograding dune at Bergen aan Zee 23

March 11, 2011Coastal Maintenance in The Netherlands24 Safety against flooding residual strength days / meters MSL - 20m dunes beach shore face dunes

March 11, 2011Coastal Maintenance in The Netherlands25 basal coast line coastal foundation years / km decades – centuries / 10’s – 100’s km MSL - 20m days / meters dunes coast line coastal foundation Sustainable Safety against flooding residual strength pro-active nourishment policy

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 ?? March 11, 2011Coastal Maintenance in The Netherlands26

March 11, 2011Coastal Maintenance in The Netherlands27 Coastal Foundation Western Scheldt Coastal Foundation Wadden Sea active sand sharing coastal system

March 11, 2011Coastal Maintenance in The Netherlands28 Challenge: explore feasible ways of upscaling 12 Mm3/year 20 Mm3/year 85 Mm3/year

March 11, 2011Coastal Maintenance in The Netherlands29 Building a sand buffer …

March 11, 2011Coastal Maintenance in The Netherlands30 Kijkduin 2

March 11, 2011Coastal Maintenance in The Netherlands31 The new Delfland coast

March 11, 2011Coastal Maintenance in The Netherlands32 Pilot Sand Engine Surplus of sand, distributed by tide/waves/wind 20 mln m3 Initial design: Ca ha, 1000 m seaward Total budget70 Meuro Realisation planned Artist impression Holland Coast Sand Engine

March 11, 2011Coastal Maintenance in The Netherlands33 Joint initiative: Province National government Water Board Local authorities NGO’s Pilot Sand Engine ambition agreement Co-financing: 17 % 83 %

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 March 11, 2011Coastal Maintenance in The Netherlands34

March 11, 2011Coastal Maintenance in The Netherlands35 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 (zeetorenhvh)

March 11, 2011Coastal Maintenance in The Netherlands36 Monitoring and evaluation monitoring morphology hydrology ecology tourism management risks (zeetorenhvh) evaluation 5 years: years: years: 2030

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) March 11, 2011Coastal Maintenance in The Netherlands37

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 March 11, 2011Coastal Maintenance in The Netherlands38

March 11, 2011Coastal Maintenance in The Netherlands39 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

March 11, 2011Coastal Maintenance in The Netherlands40 Global nearshore sand resources Sand resource > 1 km 3 / 100 km Sand resource between 0,1 and 1 km 3 / 100 km

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? March 11, 2011Coastal Maintenance in The Netherlands41

March 11, 2011Coastal Maintenance in The Netherlands42 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

March 11, 2011Coastal Maintenance in The Netherlands43 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?

March 11, 2011Coastal Maintenance in The Netherlands44 Thank you for your attention !