Expert judgment-based reliability analysis of the Dutch flood defense system

The Wettelijk Beoordelingsinstrumentarium (WBI) is the legal set of instruments for flood risk analysis in Netherlands. Often, engineers have impression that some failure probabilities defenses resulting from these are overestimated. In an effort to better estimate dikes along Dutch river Rhine, this study sets out assess them with experts and compare model results. We used Cooke’s method combining experts’ estimates a structured way follow two approaches system probability. first approach, discharges lead at least one dike failure. This gives plausible results; between 1/30 1/17.000 year. second approach based on adjusting existing model-based assessment results, by estimating model-bias incorporating additional dependencies. mostly leads large, implausible, probabilities: Experts tend give more conservative answers as they asked detailed without clear reference values. results large uncertainty consequently (too) high probabilities. Our research shows when applied frame reference, expert judgments can be successfully reliability defenses.