A polder is a low-lying tract of land that forms an artificial hydrological entity, enclosed by embankments known as dikes. The term "polder" is derived from the Dutch word "pol-", which means a piece of land elevated above its surroundings, with the augmentative suffix "-er" and epenthetical "-d-". Polders are created by reclaiming land from a body of water, often the sea, by constructing dikes roughly parallel to the shoreline, followed by drainage of the area between the dikes and the natural coastline. Polders are most commonly, though not exclusively, found in river deltas, former fenlands, and coastal areas.
The process of creating a polder involves several stages:
- Dike constructed around the area to be reclaimed to keep water from coming in.
- The area is drained using pumps and drainage canals.
- "Reeds" (a type of salt-tolerant plant) are sown by aircraft to help the soil form.
- After 3 years, reeds are burnt and the ash is used as fertilizers for the soil.
- After a period of up to 15 years, the polder is ready for growing crops, building houses, and constructing roads.
Polders are continually maintained by systems of drainage canals and pumps, which prevent them from becoming waterlogged and hence suitable for cultivation. The most notable example of polder construction is the system developed adjacent to the IJsselmeer (Zuiderzee) in the Netherlands.
