Reliability of linear structures - Latest advances and challenges from a European perspective

1. Reliability of linear structures - Latest advances and challenges from a European perspective Marie Naulin, Andreas Kortenhaus & HocineOumeraci | 9 December 2011 | FRMRC Science of Asset Management Workshop | SAM 2011 | London

2. Contents • Motivation • Reliability analysis - Latest advances in XtremRisK project • Introduction • Reliability analysis of sea dikes, coastal dunes & flood defence walls • Time dependency • Further research projects incl. reliability aspects in Europe • Future challenges

3. North Sea Flood of 1962, Hamburg, Germany

4. Legal Background • European Flood Directive (2007/60/EC) • Directive on “the assessment and management of floods” • Required steps of the member states: • Preliminary flood risk assessment (22 Dec 2011) • Flood hazard and flood risk maps (22 Dec 2013) • Flood risk management plans (22 Dec 2015)

5. Source Receptor Pathway German Joint Research Project “XtremRisK” • Development of methods to perform an integrated risk analysis based on the "Source-Pathway-Receptor - concept “ for open coasts and estuaries exposed to extreme storm surges • Analysis of current (2010) and future (2100) scenarios • Term of project: 2008 – 2012 • Partners: three German universities, local authorities & other consulting partners Vulnerability assessment (tangible/ intangible) Flooding probability Extreme storm surges storm surge area at risk flood defence structures Integration (Risk analysis, risk evaluation and risk management)

6. Overview of Subproject 2 (Risk Pathway) • Objectives • Analysis of the loading and reliability of coastal flood defence structures under extreme storm surges • Methodology • Reliability analysis of flood defences • Breach modelling of dikes and dunes • Results • Failure probabilities Pf of the flood defence systems • Initial flooding condition due to wave overtopping/ overflow and / or breaching  results will used for inundation modelling of the hinterland and for integrated flood risk analysis

7. Input Data by Subproject 1 (Risk Source) • Empirical and statistical analysis of observed water level gauges • Parameterization of storm surges and development of a storm surge generator • Multivariate statistical assessment of the storm surge curves using the parameters ‘highest turning point' and ‘fullness‘  Joint exceedance probability Pe Definition: „Fullness“ Source: Wahl et al. (2010)

8. Reliability Analysis of Flood Defences b) Failure mechanisms and limit state equations (LSE): z = R – Sz < 0: failure, z > 0: no failure a) Description of flood defence system q Mobile flood wall Dike LSE Wave Overtopping/Overflow z = qadm - q Wave Overtopping q Storm surge barrier Flood wall Overflow d) Fault treeanalysis c) Uncertainties, calculation of failure probabilities

9. Failure Mechanisms of Sea Dike waves andwater level at structure overflowovertopping • Failure mechanisms at landward slope • Velocity wave overtopping • Velocity overflow • Erosion (grass, clay, sand) • Sliding of clay layer • Uplift of clay layer • Deep slip (Bishop) • Breach development • Failure mechanismsat seaward slope • Wave impact • Velocity wave run-up • Erosion (grass, clay, sand,) • Instability revetment • Uplift revetment • Deep slip (Bishop) • Breach development loading at structure geometry and soil parameters of the dike • Non-structural • failure mechanisms • Wave overtopping • Overflow • Failure mechanismsin the dike • Piping • Matrix erosion • Sliding • Failure mechanismsat dike top • “Kappensturz” LOADING RESISTANCE

10. Overview of General Fault Tree for Sea Dikes TOP Flooding of Hinterland OR Non-Structural Failure Dike Breach OR OR Failure Inner Dike Failure Seaward Slope Failure Landward Slope Failure Dike Top LSE Over-topping LSE Overflow OR OR OR OR LSE 1 LSE 1 LSE 1 LSE 1 LSE o LSE n LSE p LSE m LSE = limit state equation

11. Failure Mechanisms of Coastal Dune waves andwater level at structure overflowovertopping • Failure mechanisms at landward slope • Overwash • Breach • Failure mechanismsat seaward slope • Erosion loading at structure geometry and soil parameters of the dune • Non-structural • failure mechanisms • Wave overtopping • Overflow LOADING RESISTANCE

12. Overview of General Fault Tree for Coastal Dune TOP Flooding of Hinterland OR Non-Structural Failure Structural Failure OR OR LSE Over-topping LSE Overflow LSE Erosion LSE Breach LSE Overwash LSE developed for dikes LSE = limit state equation

13. Overview of General Fault Tree for Flood Defence System TOP Flooding of Hinterland Dike Sea Estuary OR Dune Lock Dune River dike Dike Flood wall Lock River Sea * * * * Protected area OR River dike (levee) Dike section 1 Dike section n Flood wall OR * Non-Structural Failure Dike Breach flood defence system with flood threat from sea and river (e.g. estuary) * *

14. Time Dependency detoriation detoriation Legend

15. Adjustments of Limit State Equations • Example: LSE for wave overtopping and overflow LSE compares overtopping/overflow rates of flood defence structure: Where: qadm= admissible overtopping rate [m³/s/m] q= actual overtopping rate [m³/s/m] q • z = qadm – q q mean overtopping/ overflow rate • Adjustment • LSE compares total overtopping/overflow volumes of flood defence system: Where: Vadm = admissible overtopping/overflow volume [m³] V= actual overtopping/overflow volume [m³] • z = Vadm – V V(t) total overtopping/ overflow volume

16. Research Projects incl. Reliability Aspects at TU Braunschweig • Recent: • FLOODsite(EU) Integrated Flood Risk Analysis and Management Methodologies • Ongoing: • XtremRisK Extreme storm surges at open coasts and estuarine areas - Risk assessment and mitigation under climate change aspects • NTH BAU – SP4 A risk-based strategy for monitoring, inspection and maintenance of coastal protection structures as an integral part of life cycle calculation and optimization processes • COMTESS Sustainable coastal land management – trade-offs in ecosystem services • ProMoHaImplementation of probabilistic calculation of estuary sea dikes in Hamburg, Germany • Falster DikeImplementation of probabilistic calculation of sea dikes and coastal dunes in Falster, Denmark

17. Selection Research Projects incl. Reliability Aspects in Europe • Recent: • ComCoast (EU), FLOODsite (EU),SafeCoast(EU), RIMAX (DE) • Ongoing: • BaltCICAClimate Change: Impacts, Costs and Adaptation in the Baltic Sea Region (EU) • CRITERREApplication of geophysics to levee assessment and ERINOHNational research project on internal erosion (FR) • FloodControl2015 / SBW Solutions for smart flood control (NL) • FloodProBE – WP3 Reliability of urban flood defences (EU) • FRMRC Flood risk management research consortium (UK) • HoRisKFlood risk management for coastal areas (DE) • LDA / TOI Levee Design and Assessment (NL) • THESEUS Innovative technologies for safer European coasts in a changing climate (EU)

18. Some Future Challenges • Mean sea level rise • Increased storminess • Transitions • Length effects • Time dependence • Flood defence systems • Single point structures • Human and organisation errors (HOE) • ... Church & White (2006) Transitions Mean sea level rise FloodControl 2015 Time dependence HOE

19. X R trem isK Thankyouforyourattention! Contact Marie Naulin Leichtweiß-Institute for Hydraulic Engineering and Water Resources • Department of Hydromechanics and Coastal Engineering • TU Braunschweig T: +49 531 391-3937 F: +49 531391-8217 E: m.naulin@tu-braunschweig.de www.xtremrisk.de