How did the Netherlands reclaim land from the sea?

The Netherlands has historically reclaimed land from the sea through the creation of polders—tracts of low-lying land enclosed by dikes and drained of water.1

The Polder Method

To create a polder, engineers construct dikes roughly parallel to the shoreline to isolate an area of water. Once enclosed, the water is removed:1
* Drainage: If the land is above low-tide level, water is discharged into the sea through tide gates that open at low tide and close automatically to prevent seawater from re-entering.1
* Pumping: For land below low-tide level, water must be mechanically pumped over the dikes.1
* Soil Preparation: Newly reclaimed soil is often saline, requiring specific procedures to remove salt before the land can be used for agriculture.1

Major Projects

The most significant reclamation efforts occurred in the 20th century:
* Zuiderzee project: Beginning in 1920, this project included the construction of the 19-mile Afsluitdijk, completed in 1932. This dam sealed off the Zuiderzee from the North Sea, creating the freshwater IJsselmeer and allowing for the construction of four large IJsselmeer Polders.234
* Delta Works: Following a catastrophic 1953 flood, this massive project closed off various sea inlets in the southwest to protect the region, shorten the coastline, and combat soil salination.52