1. COMRISK Workshop Norden 12./13. May 2004 Failure probability of the Ribe sea defence Andreas Kortenhaus Leichtweiß-Institut for Hydraulics (LWI) Dept. Hydromechanics and Coastal Engineering Beethovenstr. 51a 38106 Braunschweig

2. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Contents Introduction Location of Ribe sea defence Input parameter Deterministic calculations Uncertainties Probabilistic calculations Overall failure probability Summary / concluding remarks

3. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions On the richness of English language Question: how is the German word “schräg”, Dutch: “”, Danish “” translated into English  leaning (in terms of the tower of Pisa or the church in Norden)  oblique (in plan view for wave attack)  diagonal  sloping (in terms of slopes of a structure)  inclining (in terms of walls)  tilted (in terms of very large angles)  at an angle (in terms you do not know exactly)

4. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Definition of risk Flooding risk R f c = ( P f ) S ·E(D) Expected damage and consequences of flooding E(D) Failure probability P f

5. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Location of project area

6. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Map of Ribe area and sea defences Mandø Ribe Ribe-Å Southern wing dike Northern wing dike Sluice Ribe-Å Outlet V. Vedsted Outlet Konge-Å Outlet Darum Potential flooding area Main dike line Ribe Contiguous dike line N Ebb way Contiguous dike line

7. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Standard dike profile 0,00 m DVR90 h k = 6,88m h t = 2,38m B k = 2,50m d DWL = + 5,22 m Sandcore 1:3 1:10 d fr Clay layer 1:100 dbdb ParameterValue Slope of foreland (length 100m)1:100 Height of dikefoot h t 2,38 m Height of crown h K 6,88 m Width of crown B K 2,50 m Seaward slope 1:n1:10 Shoreward slope 1:m1:3 Thickness clay layer outer slope d fr 1,0 m Thickness clay layer inner slope d b 0,5 m

8. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Ribe sluice Outer floodgates 0 mDVR90 DWL = 5,22 m Outer flood gates (closed) -3,60 m Sole paving 5,78 m 5,88 m Chamber walls Inner floodgates

9. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Outlet Konge-Å 0 m DVR90 -2,00 m 5,22m DWL 6,88 m Floodgate Sandcore Grass layer Clay layer Storm gate Stone mattress Berm 1:3 1:2 4,23 m 2,50 m 1:7 Filter gravel Drainage Pavement Sole (concrete)

10. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Location of profiles analysed Wave rider Fanø Fanø Mandø Ribe N 3156 6644 9400 14499 8422 10403 Sluice Ribe-Å Profile 270 Profile 1 Profile 250 Profile 290 Outlet Konge–Å Outlet Darum Outlet V. Vedstedt Sluices / outlets Dike profiles Wind measurements Water level measurements

11. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Adaption of profile data to model – profile 3156 Ribe N 3156

12. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Adaption of profile data to model – profile 6644 Ribe N 6644

13. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Adaption of profile data to model – profile 8422 Ribe N 8422

14. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Adaption of profile data to model – profile 9400 Ribe N 9400

15. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Adaption of profile data to model – profile 10403 Ribe N 10403

16. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Adaption of profile data to model – profile 14499 Ribe N 14499

17. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Typical input parameter for two sections 0,00 m DVR90 h k = 6,73m h t = 1,92m B k = 2,80m d Clay:  K,  Kr DWL = + 5,22 m H s, T p, θ Sand:  S,  Sr,  s 1:3,1 1:20 1:11 d fr km 8422 H s =1,47md fr =1,0mc u =15,0 [KN/m 2 ] T p =6,01s  K =17,0 KN/m 3 d G =0,05[m] θ =20°  Kr =20,0 KN/m 3  S =19,0 [KN/m 3 ] t s =6,5hc s =35,0 KN/m 2  Sr =22,0 [KN/m 3 ] d=3,3mc ss =10,0 KN/m 2  s =40,0[°] 0,00 m DVR90 h k = 7,08m h t = 2,66m B k = 2,00m d Clay:  K,  Kr 1:12 1:10 DWL = + 5,22 m H s, T p, θ Sand:  S,  Sr,  s 1:2,6 d fr km 6644 H s =1,51md fr =1,0mc u =15,0 [KN/m 2 ] T p =4,89s  K =17,0 KN/m 3 d G =0,05[m] θ =20°  Kr =20,0 KN/m 3  S =19,0 [KN/m 3 ] t s =6,5hc s =35,0 KN/m 2  Sr =22,0 [KN/m 3 ] d=2,65mc ss =10,0 KN/m 2  s =40,0[°]

18. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Failure modes for dike profiles Core Clay Layer Global failure modes: Overflow Overtopping Dike breach Dike slid Failure modes shoreward slope: Velocity overflow Velocity overtopping Gras erosion Clay erosion Infiltration Kappensturz Phreatic line Clay uplift Clay slid Bishop shoreward slope Sand erosion Failure modes seaward slope: Revetment stability Impact Revetment uplift Velocity wave run-up Gras erosion Clay erosion Phreatic line Cliff erosion Bishop shoreward slope Internal failure modes: Piping Matrix erosion

19. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Failure modes Ribe sluice Global failure modes: Overtopping Overflow Hydraulic uplift

20. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Results of deterministic calculations

21. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Results of sensitivity analysis

22. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Uncertainty analysis of water level

23. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Correlation of water level and wave heights

24. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Uncertainties of input parameter

25. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Fault tree calculations

26. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Probabilistic results (overview)

27. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Probabilistic results of scenario approach (sect. 10403)

28. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Probabilistic results (sensitivity analysis)

29. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Definition of sections of Ribe sea defence

30. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Overall failure probability for Ribe sea defence all sectionsall (modified)only dikes P f,max 6,3 10 -1 6,2 10 -3 7,1 10 -5 sectionRibe sluice Dkm 10403 P f,Ribe 9,5 10 -1 2,6 10 -2 2,5 10 -4

31. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions study of input parameters  good representation of dike cross sections  soil parameters taken from measurements if possible deterministic calculations of all cross sections and sluices  overtopping failure at sluice for design conditions  grass erosion failure for all sea dikes uncertainty analysis of input parameters  detailed study of water level  correlation of water levels and wave heights probabilistic calculations of all cross sections and sluices  reduction of scenario tree to most important elements  overall failure probability for dikes in the range of P f = 10 -5  failure probability for sluice in the range of P f = 10 -1 Overall failure probability of sea defence  sluice and outlets to be considered correctly  overall probability governed by dike failure probability

32. LWI Introduction Location Input param. Det. calc. Uncertainties Prob. calc. Conclusions Thank you very much for your attention Andreas Kortenhaus Leichtweiß-Institut für Wasserbau Technische Universität Braunschweig Tel.: 0531 / 391-3981 E-mail: a.kortenhaus@tu-bs.de LWI