Probabilistic design of water defense systems in The Netherlands

After the disaster in 1953, a statistical approach to the storm surge levels was chosen and an extrapolated storm surge level would be the basis for dike design. In recent decades, the development of reliability theory made it possible to assess the flooding risks taking into account the multiple failure mechanisms of a dike section and the length effect. It is pointed out that economic activity in the protected areas has grown considerably since the 1950s and that even more ambitious private and public investments, particularly in infrastructure, are planned. Moreover, the safety of a growing population is at stake. These considerations justify a fundamental reassessment of the acceptability of the flood risks.