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Application of reliability-based flood defence design in the UK

F.A. Buijs1, H.A.J.M. van Gelder2 and J.W. Hall3
1  HR Wallingford, Wallingford, United Kingdom
2 Delft University of Technology, Delft, The Netherlands
3  University of Bristol, Bristol, United Kingdom

Increasing concern about recent and potential impacts of flooding in the UK are leading to the adoption of risk-based methods for planning, appraisal, design and operation of flood defences.  Probabilistic methods for assessment and design of flood defences are relatively well developed in the Netherlands because of the potentially devastating impacts of flooding. This paper describes a test application of reliability-based design tools developed for dike rings in the Netherlands to the flood defence system at the Caldicot Levels in South Wales. Although constrained by data limitations (even at this relatively data-rich site, by UK standards) the reliability method provides estimates of the probability of failure of the flood defence system, identifies weak system components and identifies which parameters contribute most to the probability of failure. However, for reasons described in this paper, reliability methods developed in the Netherlands are not universally applicable in the UK context.

Key words: PC-Ring, failure modes, flood defence system, probability of failure, weakest links