Polder

A polder is a low-lying area enclosed by dikes or levees and forms an artificial hydrological entity. There is no connection with surface water outside the polder other than through manually operated pumps or inlets. There are three types of polders: Land reclaimed from a body of water, flood plains separated from the sea or river by a dike, marshes separated from the surrounding water by a dike and subsequently drained. A polder usually has an excess of water as its ground level is often lower than surrounding water levels. Pumping or opening sluices at low tide is necessary.