The strategic policy objective is to guarantee the safety against flooding during extreme events. The focus is typically on the small scale: the dunes should be kept at sufficient strength to withstand hydraulic boundary conditions with a predetermined exceedance probability (to be tested every five years officially). The protection level is a political choice, laid down in Flood Defence Act (TK, 1996), based on a cost-benefit analysis. For the densely populated Holland coast the dunes should be able to withstand hydraulic boundary conditions with an exceedance probability of 1 * 10-4 times per year; the Wadden coast 5 * 10-4 times per year with the exception of Texel (2,5 * 10-4 times per year); the Delta coast 2,5 * 10-4 times per year. The decision recipe is based on the Dune Erosion Point (DEP), a quantitative state concept that helps determine the dune strength under certain hydraulic boundary conditions (TAW, 1984). Both the method and the hydraulic boundary conditions are officially reviewed five yearly. Water boards, dedicated regional water management authorities, are responsible for executing this Coastal Safety policy.
