FLOODsite Task 25: Pilot Schelde

Transcription

1 FLOODsite Task 25: Pilot Schelde Marcel Marchand 12 February 2008 GOCE-CT

2 United Kingdom The Netherlands Belgium 12 February 2008 Schelde pilot 2 2

3 Contents Research team Problem setting Pilot objectives Approach and tasks Results / lessons learned Scientific development Technologies 12 February 2008 Schelde pilot 3 3

4 Partners and researchers WL Delft Hydraulics/Deltares: Marcel Marchand (pilot coordinator) Alessandra Crosato (till 2006), Karin de Bruijn, Marjolein Mens, Marnix van der Vat, Nathalie Asselman, Frans Klijn, Chris Sprengers, Claire Jeuken, Aljosja Hooyer, Arjan Wijdeveld Delft Technical University: Jill Slinger, Maaike Muller, Miriam Cuppen, Pieter van Gelder, Sayan Gupta, Michelle Hendriks Twente University: Joerg Krywkow, Anne van der Veen 12 February 2008 Schelde pilot 4 4

5 Problem setting Navigability Safety nature conservation Schelde estuary 12 February 2008 Schelde pilot 5 5

6 Additional complications Past land reclamations still exert an influence on local tidal ranges: eastern part of Westerscheldt experiences rise of highwaters of 50 cm/century (compared to 25 cm in other parts of Dutch coast) Evolution Schelde-estuary ( ) Van der Spek (1994) Climate change and sea level rise will cause an additional increase in high water risk. 12 February 2008 Schelde pilot 6 6

7 But nevertheless region has highest safety level ever in history, after 1953 disaster. So everybody happy.? yes, there is no immediate problem. no, climate change and recent tragedies (e.g. Katrina) stirred anxiety/ new approaches to flood risk revealed weakness in protection system / government discusses evacuation measures Belgium adopted new flood risk management based on risk maps innovative projects and plans for flood risk mitigation 12 February 2008 Schelde pilot 7 7

8 Ongoing projects and programmes Buitendijks Dijk Binnendijks Lange termijn visie Floodsite: wetenschap Safecoast: kustbeheerders Comrisk: kustbeheerders Fliwas Comcoast (concrete oplossingen voor 2 pilots langs Westerschelde) SBW (onderzoek) VTV (SBW = input) HIS operationeel Internationaal Landelijke systemen HR HIS Kust Sigmaplan Specifieke informatie Zwakke Schakels VNK Zeeweringen 12 February 2008 Schelde pilot 8 8

9 Flood management options 3. Storm Surge Barrier Vlissingen 1. Dyke enforcement 4. Overschelde ComCoast Braakman 5. Managed retreat Hedwige-Prosperpolder 2. Storm Surge Barrier Antwerp Potpolders 12 February 2008 Schelde pilot 9 9

10 The policy challenge How to accomodate present needs and future developments while 1. minimising flood risk 2. ensuring sufficient navigability, and 3. preserving nature values 12 February 2008 Schelde pilot 10 10

11 Pilot study objectives The overall purpose of the pilot study is: to develop and test the FLOODsite methodology on flood risk management for the Scheldt estuary More specific objectives: Risk analysis: To study the future vulnerability of the Scheldt Estuary to riverine flooding and coastal storms, taking into account both changing hydraulic conditions and land development scenarios; Assessment: To evaluate sustainable flood management strategies in association with stakeholders; and Transition: To provide guidelines on how to manage the transition to implementation 12 February 2008 Schelde pilot 11 11

12 Testing of FLOODsite science: Task 7: Reliability analysis of flood defences Task 8: Inundation modeling evaluation Task 10: Toxic risk prediction of flooding Task 14: Design and ex-ante evaluation of innovative strategies for flood risk management Task 17: Evacuation modeling Task 18: Development of Framework for Long-term Planning (DSS) Task 19: Flood event management DSS Task 25: Stakeholder involvement and transition management 12 February 2008 Schelde pilot 12 12

13 Current approach flood risk management safety level: 1/4000 per year Foreshore / dyke improvement Topography Population and land use Damage susceptibility prob. of exceedance prob. of failure storm and storm surge high water level / wave at shore dyke failure Inundation Damage/ ecological impacts Affected people / ecosystem economic losses prob. of flooding Injuries and Casualties Long term economic impacts source pathway receptor 12 February 2008 Schelde pilot 13 13

14 Potential measures Scheldt estuary Storm Surge Barrier Foreshore / dyke improvement Secondary dykes Raised grounds Planning and zoning Task 14/18 building codes Insurance; relief funds Topography Population and land use Damage susceptibility storm and storm surge prob. of exceedance high water level / wave at shore prob. of failure dyke failure Inundation Damage/ ecological impacts Task 7 Task 8 prob. of flooding Task 10 Injuries and Casualties Affected people / ecosystem Long term economic impacts economic losses Early warning Shelters and Evacuation Reconstruction funds Rescue and source pathway relief receptor Task 17/19 12 February 2008 Schelde pilot 14 14

15 Reliability analysis (7) failure mechanisms: - Overflow and wave overtopping - Covering damage/erosion of the dike - Bursting/piping - Sliding inner slope Preliminary results dyke ring 32 Failure probability > 1/11 per year NB: design standard for dyke is a 1/4000 per year water level failure does not automatically induce flooding! 12 February 2008 Schelde pilot 15 15

16 Inundation Modeling (8) comparison of models 1953 disaster as calibration 12 February 2008 Schelde pilot 16 16

17 Toxic risk of flooding (10) Trial modeling of deposition of polluted sediments during a dyke break and flooding in the Walcheren area. SOBEK 1D/2D including a sediment model (sand; silt and clay) considerable uncertainty toxic risk received hardly any attention up till now. 12 February 2008 Schelde pilot 17 17

18 Flood Risk Analysis (14) Inundation model (2D) Damage and casualties model Scenarios Alternative strategies Costs and benefits Multicriteria analysis (people, planet, profit) Current risk: 0.53 M /y 4 Could increase 2 considerably in future! 0 Risk (M /yr) Year World market National enterprise Local stewardship Global sustainability 12 February 2008 Schelde pilot 18 18

19 Evacuation models (17) ESCAPE, Evacuation Calculator, INDY resolution often too coarse to be of help for planning purposes evacuation of large areas along Schelde seems unwise, better focus on local refuges map of study area used in ESCAPE 12 February 2008 Schelde pilot 19 19

20 Long term planning DSS (18) visualisation of Task 14 results 12 February 2008 Schelde pilot 20 20

21 Flood Event Planning (19) X Hazard Exposure Consequence 12 February 2008 Schelde pilot 21 21

22 Study approach Task 25 citizens scientists In-depth interviews policy makers Workshop 1 with policy makers Flood risk assessment Workshop 2 citizens with scientists Workshop 3 scientists with policy makers Questionnaire to citizens Analysis and conclusions 12 February 2008 Schelde pilot 22 22

23 End user involvement Local level: inhabitants; water boards Regional level: Province of Zeeland National level: Rijkswaterstaat International level: Proses Different ways of involvement: interviews, workshops, meetings, etc. Sensitivity on the part of governments 12 February 2008 Schelde pilot 23 23

24 Observations: Local people are aware of flood risk: knowing that flooding could occur and yet not worrying about it is a REALITY for local inhabitants. Flood prevention measures are preferred, particularly raising and strengthening primary sea defence dikes. The shift exhibited by participants at the 2nd workshop to spread attention more evenly over the flood risk management phases represents learning by the citizens about the value of redundancy in combating a natural hazard. 50% 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% flood prevention flood amelioration recovery measures overarching measures 12 February 2008 Schelde pilot 24 pre post 24

25 Observations (2) Policy makers were surprised by the accuracy of the information of local people, the percipience of the questions and challenged on the precautionary planning issue. Public debate on measures hampered because of wrong information or perceptions (e.g. purpose and mitigating impact of managed retreat). Citizens have concern about planning process (for instance lengthy decision procedures) Reliability analysis provides useful new knowledge, but link with flood risk still unclear (not all failures result in a flood). Evacuation models/dss interesting, but not yet fit for use. End user needs unclear. Policy makers are concerned how to explain to citizens that you invest in disaster preparation while at the same time you ensure that it will never happen. Policy makers say that decision-makers make no decision but ask for more studies. 12 February 2008 Schelde pilot 25 25

26 Lessons learned Pilot opened 3 windows of knowledge: Scientific domain: probabilities, models and uncertainty Local citizens: perception and experience, that remains largely unused in decision making Policy and management institutions: innovative approaches compete with vested interests, procedures and legislation 12 February 2008 Schelde pilot 26 26

27 Lessons learned (2) Free flow of information between three domains hampered by four causes: 1. communication problems (complexity, jargon, differences in background) 2. difficult to incorporate all relevant stakeholder knowledge with scientific insights (social learning) (however successful at small scale as demonstrated in pilot) 3. inhabitants don t trust policy makers 4. international dimension of the Schelde estuary 12 February 2008 Schelde pilot 27 27

28 International dimension Scheldt river NL Risk characteristics: potential economic damage low - medium high potential number of high low casualties safety standard 1:4,000 year 1:70 up to 1:2,500 year Differences in physical and socio-economic characteristics: inundation process immediately after a breach a gradual rising of waters polder floods and water depths quickly reach high levels evacuation opportunities higher grounds are far away higher grounds are nearby land use predominantly agricultural highly industrialised around Antwerp main historic flood event and response 1953 disaster Deltaworks 1976 flood Sigma Plan B 12 February 2008 Schelde pilot 28 28

29 Lessons learned (3) NL is special case: high safety standard combined with high potential damages and casualties In some years time the 1953 disaster is faded from memory: how will people then perceive the risk? 12 February 2008 Schelde pilot 29 29

30 Further scientific development needed Long term hydro/morphodynamics (+ extreme conditions) of estuary vis-à-vis structural measures Model uncertainties, e.g. how to incorporate failure into flood modeling? Validity of models and knowledge beyond scientific domain (e.g. risk perception versus calculated risk) Methods for improving the Science-Policymakers- Stakeholders interfaces Integration of flood risk management in sustainable regional development Open exchange of data and joint research between NL and Belgium (ongoing) 12 February 2008 Schelde pilot 30 30

31 Technologies that can be used now: Fully fledged flood risk analysis (flood models, scenario and strategy development) Techniques for evacuation planning and real time systems, BUT should be tailor made to the explicit needs of the end user 12 February 2008 Schelde pilot 31 31

32 Questions? 12 February 2008 Schelde pilot 32 32