Polder

A polder is a low-lying tract of land reclaimed from a sea, lake or river and protected from flooding by a surrounding dike, with water that seeps or is pumped in continually removed to keep the land dry and usable. The technique was developed and progressively refined in the Low Countries from around the eleventh century onward, with Dutch engineers combining dikes, drainage canals and, from the sixteenth century, windmill-driven pumps to reclaim large areas of farmland and, later, whole settlements from the sea. Steam, and eventually electric and diesel pumps replaced windmills for drainage from the nineteenth century on, and polder construction remains a defining Dutch civil-engineering achievement, most dramatically in the large-scale twentieth-century reclamation of the former Zuiderzee.