System behaviour in flood risk calculations

Abstract

A risk-based safety approach is indispensable to support decision-making on flood protection strategies and measures. In most deltaic areas, flood risk analysis involves more than analysing the flood hazard and the potential damage, and flood defence systems also play an important role. In such systems consisting of rivers, estuaries and flood defences, interaction effects between local failures and hydraulic loadings and reliability elsewhere in the system can be significant. Hitherto, such system behaviour has been paid little attention in flood risk analysis approaches. This paper presents a computational framework for analysing flood risk while fully accounting for system behaviour. The approach is based on Monte Carlo sampling, in which the number of computationally expensive hydrodynamic model runs is reduced significantly to only those realisations, for which the flood defence system fails. A case study illustrates the approach and demonstrates that fully accounting for system behaviour can make a significant difference for both, reliability of flood defence structures and flood risk in terms of individual risk to life as well as economic damage.

Keywords:

• flood risk analysis
• system behaviour
• polders
• dikes
• river systems

Acknowledgements

This paper concerns the findings of the Delft Cluster Project DC04-30: ‘Safety from flooding, part C.2: System behaviour’ as well as findings of research conducted for Rijkswaterstaat, RIZA and DWW, Ministry of Public works, the Netherlands.