Geography of the European Netherlands European part of the country can be split into two areas: the low and flat lands in the west and north, and the higher lands with minor hills in the east and south. The former, including the reclaimed polders and river deltas, make up about half of its surface area and are less than above sea level, much of it actually below sea level. An extensive range of seawalls and coastal dunes protect the Netherlands from the sea, and levees and dikes along the rivers protect against river flooding. The rest of the country is mostly flat; only in the
Delta Works After the North Sea flood of 1953, a Delta Works Commission was installed to research the causes and develop measures to prevent such disasters in future. They revised some of the old plans and came up with the "Deltaplan". Unlike the Zuiderzee Works, the Delta Plan's purpose is largely defensive and not for land reclamation. The Delta Plan is a national programme and demands collaboration between the national government, provincial authorities, municipal authorities and the water boards. The plan consisted of blocking the estuary mouths of the Oosterschelde, the Haringvliet and the Grevelingen. This reduced the length of the dikes