A proposal for a reliability rating system for fluvial flood defence embankments in the United Kingdom

A reliability rating system for river embankments is illustrated. The system is based on a new index, called Index of Inadequate Performance, which reflects the results of a simplified and approximated reliability analysis. The approach allows decision makers to quantify the expected performance of each stretch in an inventory of embankments and rank them according to an indicative measure of the likelihood of failure under extreme hydraulic conditions. Giving a measure of the influence of the basic characteristics of embankments on their performance, the system can also quantify the effect of not knowing some of these basic characteristics. Decision maker are thus provided with a tool which enables them to estimate the impact of this ignorance, or basic epistemic uncertainty, on the reliability assessment. The rating system also indicates which information should be collected in order to effectively reduce this type of uncertainty.