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
Flood control in the Netherlands these waters. The Zuiderzee Works (Zuiderzeewerken) are a system of dams, land reclamation, and water drainage works. The basis of the project was the damming off of the Zuiderzee, a large shallow inlet of the North Sea. This dam, called the Afsluitdijk, was built in 1932–33, separating the Zuiderzee from the North Sea. As result, the Zuider "sea" became the IJsselmeer—IJssel lake. Following the damming, large areas of land were reclaimed in the newly freshwater lake body by means of polders. The works were performed in several steps from 1920 to 1975. Engineer Cornelis Lely played a major part in