NNBF Examples and Flood Risk Reduction Measures in the Netherlands

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1 NNBF Examples and Flood Risk Reduction Measures in the Netherlands Quirijn Lodder Principal Advisor Coastal Flood Risk Management TU Delft NASA

2 I like to read history books.. 2

3 I like to read history books.. History provides a mirror to the present 3

4 I like to read history books.. Churchill on the Dutch: They are completely selfish and only fought when they were attacked and then only for a couple of hours 4

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6 Holocene Marine and fluvial sediments Pre-holocene glacial and Aeolian sediments 6

7 Flood Prone Netherlands 26% below sea level 55% is susceptible to flooding 60% of our population lives below sea level > 60 % of our economic value is earned in the lowest-parts of the country Strong correlation with sediment origin 7

8 2020 Economic Flood Risk ( /ha/year) 8

9 2020 Localized Individual Risk 9

10 Flood Risk Standards 10

11 Examples flood risk management for Rivers and the Coast Key messages: - Systems approach - NBS/NNBF are used a lot, they are not a goal. Many times they turn out to be the most appropriate solution. 11

12 Room for the River Flood Risk Management objective: Reduce water levels occurring with a Rhine discharge of m3/s to the water levels of a m3/s. Hmax, Q16.000m3/s = Hmax, Q15.000m3/s 12

13 Effect of high discharge events on statistics 13

14 Non Flood Risk Management objectives have been to enhance: Spatial Quality of the Landscape Nature values Recreational values 14

15 Adaptation to the plan was possible, but combined all measures should still deliver. -> System Approach -> Stakeholder Engagement 15

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17 Examples 17

18 30-60 cm water level reduction ha new river nature 18

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20 Afferdense en Deestse Waarden 5 cm water level reduction 158 ha new river nature 20

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22 Performance, Metrics and Adaptive Management Water level reduction objective is known per measure and being monitored on a system scale. Non-FRM benefits are not always monitored very well. Non compliance with FRM goals will lead to adaptive management. Non compliance with Non-FRM generally not.. 22

23 There is more then just high discharge events Discharge distribution Different branches Differential bed erosion 23 Differential bed erosion

24 Bed erosion 24

25 Bed erosion 25

26 Negative effects on navigation 26

27 Sediment management in the river? Recycle sediments upstream? Might be beneficial but quite some R&D is needed before we commence.. 27

28 Coastal Management of Beach and Dune systems 28

29 Holocene Marine and fluvial sediments Preholocene glacial and eolian sediments 29

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37 25cm/100y 37

38 25cm/100y Sediment budget! 38

39 Strategic objective Provide the conditions to sustainably preserve the functions of the coastal zone including: - Protection against flooding - Nature - Recreation - Fresh water extraction 39

40 Strategy Hold the line Grow with sea level NNBF measure: Feed the coast with sediments 40

41 Performance objectives & metrics Current coastline position irt a reference coastline Probability of beaching of the flood defenses No significant negative impact on EU protected habitat and species 41

42 Bring sand from offshore Deeper that close depth 42

43 Bring sand from offshore Deeper that close depth 43

44 Bring sand from offshore Deeper that close depth 44

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47 Cross-shore NL Zandvoort Longshore km

48 Cross-shore NL Zandvoort Longshore A km

49 Cross-shore NL Zandvoort Longshore km

50 Cross-shore NL Zandvoort Longshore km

51 Cross-shore NL Zandvoort Longshore km

52 Cross-shore NL Zandvoort Longshore km

53 Cross-shore NL Zandvoort Longshore km

54 Cross-shore Longshore 0 A A A -2 B m Cross Shore m Long Shore km A km -12

55 R&D Effects of subsequent nourishments? Recolonization vs nourishment frequency Cumulating of effects? Monitoring 56

56 Ecological monitoring of Ameland Shoreface Nourishment B 57

57 So back to Churchill 58

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59 I think you are doing the right thing with our NNBF effort 60