Delta Plan, flood control and reclamation project, S Netherlands, in the Rhine River delta. Built in 1957–81, it involved construction of four major dikes (up to 131 ft/40 m high) across the Rhine's four estuaries on the North Sea, three auxiliary dams, and a storm-tide barrage 38 ft (11.5 m) high and 262 ft (80 m) wide across the IJssel River. The project shortened the Dutch coastline by c.440 mi (700 km), reclaimed 6,100 acres (15,000 hectares), and created a freshwater lake (33 sq mi/85 sq km). Two navigable waterways to Antwerp and to Rotterdam and Europoort were left open.
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