Sloterplas is a man-made lake in west metropolitan Amsterdam where there had been a natural lake until 1644.1
People had been living in this area since about 1100, farming and fishing, and managing the levels of the water around them. The land all of west Netherlands was delta clay and sand overlaid with peat bogs and wet grasslands all of it occasioned by meandering rivers and lakes of changeable size. Slotermeer was a shallow body that would vary seasonally in area. It was often dry in the summer or dryish. It was wetland, and a lake in the sense that it was usually covered by water.
Just lower than the surrounding property, Slotermeer was left as wetland until the riches and technology of the Dutch Golden Age -- and its hunger for more arable property demanded and enabled its reclamation.*
Poldering was an ancient practice by the early 1600's, but drainage of wetlands had only become possible as the technology of the water-pumping windmill had improved. The first large area to be drained was only about a half-century old when Slotermeer fell dry.
The new land, surrounded by dikes and dried impoldered became Sloterdijkermeerpolder.
The area was not large as polders go; but was another example of the remarkable new ability to make dry land of a watery area.
But Sloterdijkermeerpolder didn't always keep its inhabitants' feet dry. It flooded six times between 1647 and 1726, due to breaches in the dike system. After each flood, and each repair job, the polder's windmill pumped its land dry; but it was in a dangerous area, and was difficult to maintain.
The district of Sloten, roughly triangular, was endangered on two sides: the Ij, an arm of the sea, was to the north, and the Haarlemermeer, a big lake, was to the west. The Haarlemermeer was in a state of growthfulness, and in fact it swallowed a couple of Sloten villages in the 17th and 18th centuries.
The famed engineer Jan Adriaanszoon Leeghwater called in 1641 for the drainage of Haarlemermeer. It would have been a massive project, requiring 200 windmills, to drain and keep dry a lake that had grown to cover nearly 170 square kilometers. The lake would remain in place for two centuries, and would remain a threat, until the invention of the steam engine.
In the autumn of 1836, a storm overwhelmed the control systems, and the whole of Sloten, up to the edge of Amsterdam, fell under water. This provided incentive and prompted a decision to finally drain the Haarlemermeer and be done with its danger.
According to an elevation model of the Netherlands, and its comparison between the ground-level at the building where I lived in Osdorp and that of an adjacent historical polder, the level rose during the sand-moving project of the late 1940's and 50's by about three meters.
From 1870, Amsterdam began to grow outside of the Singelgracht, now its inner canal. After expanding southward in 1896 into what is now Amstelveen, the city proceeded to swallow Sloten, officially annexed in 1921. The sparsely-populated Sloten became part of the municipality of Amsterdam, and in 1935 it was an important part of the General Expansion Plan (Algemeen Uitbreidingsplan, the AUP.) The Sloterdijkmeerpolder would be a critical part of the AUP. The reason for a new lake within residential/commercial-zoned land was not for its recreational nor esthetic value, but for the harvest of sand. The development of Sloten included this massive relocation of earth, from the reborn (and much-deeper) lake into the outlying neighborhoods.
World War II slowed plans for the dredging of the site of the former Slotermeer. But after the war and with a renewed sense of urgency in its need for new housing the city proceeded with its expansion plan. Sloterdijkermeerpolder was dredged and its material spread over wide areas of Sloten between 1948 and 1956.
The modern Sloterplas is, at 30 meters, deeper than most of the Netherlands is high.
1.) The date that Slotermeer was completely drained is variously given as 1634 and 1644. The later date accords with a suggestion that a decision to dry the area was made by 1639.
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* The English-language term "reclamation" is a misnomer, since it refers to a process of claiming land, not of reclaiming it. .
The Dutch word, landwinning, is more accurate.
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