Here we explain some of the unique features of the Netherlands.
The Dutch created their own land...
This explains the concept of 'polders'. Unlike landfill, where dirt is
thrown into the water until it reaches above the water, a polder is a
lake or part of the sea where a dike is placed around. The water is then
pumped out (this picture
shows the different water levels).
This (very simplified) animation describes the steps:
Here we see a lake.
A dike ('ringdijk') is build around it. If it is a lake, a canal
('ringvaart')is created around the dike, to allow for the pumped
out water be carried out. If the polder is part of the sea, this
canal is not needed.
Mills are placed on the dike. In the old days, these were windmills.
Now, we use electric or diesel mills.
If we are not adjacent to the sea, a canal is dug to connect the
canal around the polder to the nearest open body of water.
The water is pumped out.
And continues... This may take years for a large polder.
... and continues...
Finally, when it is empty, and only mud remains, musterdseeds
are spread out by planes. Musterdplants suck up a large amount
of water and will help dry out the mud.
Canals are dug which will help keep the waterlevel. Several
mills will remain on the dikes to regulate the water level.
Now roads, farms, and communities are created.
Some polders are so deep that walking on the street you are 15
feet below sealevel...
Now that we have all these different waterlevels,
how do boats go from one level to another? Well, we use a sluice or waterlock
('sluis') for that. This is how it works (very simplified):
A boat on one level (inside a polder) sails into the sluice
on the side where the doors are open and the waterlevels are the
same.
The doors close.
And close...
...and close...
Now that the doors are closed, the waterlevel in the middle
chamber is made equal to the waterlevel on the other side of the
exit door.
