Policy implications of uncertainty integration in design

In this paper, the implications of integration of uncertainties in the design of flood protecting structures will be analysed. In particular the probability of inundation of the low-lying polders protected by dikes from the Dutch Lake IJssel (1200 km(2)) is studied on the basis of a physical model. The uncertainty in the probability of overtopping is analysed with a first order reliability method (FORM). The FORM-calculations showed that the uncertainty in the wind speed and the uncertainty in the water level contributed most in the total uncertainty of the probability of overtopping of a dike with given height. A comparison has been made between the results of the FORM-calculations and the calculations where only intrinsic uncertainty has been assumed in the basic variables. Furthermore, in this paper, the reliability-based optimal design of the dikes along the lake is studied. Finally the policy implications of the uncertainty integration in the design of dikes are discussed.