With over a third of its land below sea level, the Netherlands have been fighting against the sea for hundreds of years. Over the centuries they have built dykes, dams and windmills to stop sea water from getting into the country. The last big disaster occurred in 1953. A storm that swept across the North Sea killed over 2000 people and flooded thousands of square kilometers of land. After this catastrophe something had to be done. A new plan, called the Delta Works, created a series of dams, locks, dykes and other barriers to protect the coastal areas from the sea. The mouths of the major rivers were closed and the coastline was shortened by about 500 km. As a result the water behind the dams turned into freshwater lakes. It took over 30 years to complete the Delta Works and officials say it is the world's best defense system. In addition, old dykes have been improved and made higher. Only a great storm that happens once in 10, 000 years can break them. The final part of the Delta Works, the Maeslant Barrier was opened in 1997. It was originally intended to keep sea water out of Rotterdam's Europoort harbor, most of which lies below sea level. But it also protects the surrounding towns and the farming land around it. When sea levels rise by 3 meters the two semi-circular gates of the 300 meter wide barrier close automatically. It is expected that the barrier will close once every ten years because of large storms but in the next 50 years it will probably close even more often. Near the coast sea levels have gone up about 20 cm in the last hundred years. If experts are right the sea near the Netherlands may rise up to 1.3 meters by the end of the century. In 2007 the barrier passed its first test and closed because of a storm.