In February 1953, a severe storm flooded much of the Delta region of The Netherlands, killing more than 1,800 people. After that disaster, the Dutch government decided to greatly increase protection from flooding for all Delta estuaries. This article presents the design philosophy adopted for the main sea defenses. By 1975, all the estuaries had been protected except the largest, the Oosterschelde. The original plan called for the closing of this estuary with an impervious dam, and work had already started when opposition to the plan grew rapidly because of rising interest in the natural environment. After a period of political maneuvering, the Dutch Cabinet decided to build a barrier-type of dam with gates which could be closed during severe storms, but which would be open at all other times. The policy study — which supported the decision-making process and which analyzed three basic alternative means of protection against flooding — is briefly discussed here. Construction of the storm surge barrier was completed and its was opened in a formal ceremony by Queen Beatrix on October 4, 1986. Some original and actual cost figures are given. This article highlights the difficulties of managing such a megaproject.