The Oosterscheldekering, a 9 km flood barrier linking the islands of Schouwen-Duiveland and Noord-Beveland in the Dutch province of Zeeland, has mostly stayed open since it was completed in 1986. Over its 40 years of operation, it has closed 28 times—roughly once every 17 months—with its most recent closure on January 31, 2022, during the storm Corrie. Only 3 km of the barrier can be closed to manage water levels, while the remaining 6 km stays open to maintain the salinity of the water, which is crucial for the local oyster and mussel fishing industry. The Oosterscheldekering was part of the Delta Plan, a large-scale engineering initiative launched in 1954 after the catastrophic 1953 North Sea flood, which claimed 1,835 lives and destroyed 4,500 buildings. The plan included 13 major projects to prevent such disasters in the future, with the Oosterscheldekering being one of the most ambitious. Initially, it was planned as a solid dike that would completely block the estuary, but public protests led to a redesign that allowed for selective closures to protect marine life and the fishing industry. Construction of the Oosterscheldekering began in April 1976 and was completed in June 1986. The structure features 65 concrete pillars, 30 to 40 meters high, and 62 massive steel gates that are 42 meters wide and weigh between 260 and 480 tons. The total weight of the barrier is approximately 1.2 million tons, with 450,000 cubic meters of concrete and 5 billion kg of rockfill used in its construction. It is designed to withstand a flood that occurs once every 4,000 years. The annual operating costs of the Oosterscheldekering are around 17 million euros, with the barrier closing approximately 28 times over the past four decades. Each gate is tested once a month by closing it briefly and then reopening it. The structure is expected to last more than 200 years, and routine maintenance is carried out between April and September, avoiding the storm season. While it is not the longest flood barrier in the Delta Plan—Oesterdam is slightly longer—the Oosterscheldekering remains a key part of the Netherlands' coastal protection system. Its operation is based on water levels exceeding 3 meters above sea level, rather than standard weather terminology, and closures are not automatic.