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The Netherlands

Massive Dutch waterworks projects

There have been several massive water projects in the recent history of the Netherlands.

• The Afsluitdijk, or closure dike, isolated the former Zuiderzee from saltwater in 1932, and three massive polders took their place in the suitable clay-based areas of what was from that time the Ijselmeer. It was a huge project, three-quarters of a century in realization.

The two largest polders, the Noordoostpolder and Flevopolder, form an entire new Dutch province.

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• The Nieuwe Hollandse Waterlinie was a Dutch military defense work, built in the late 1800's consisting mainly of an area — a line — that was immersible in shallow water.

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• The Stelling van Amsterdam, based upon the technologies of earlier waterlines, was a "city wall made of water," designed as protection of the last bastion in event of an invasion.

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• The Delta Works was a great set of projects, the net goal of which was the protection of the southern, river-mouth area of the country from the rise of the North Sea in times of storm.

The project entered initial work phase in 1950, the final piece complete in 1997. Plans were not complete when the initial phases begun, and indeed the engineers gave consideration for the fact that if they started in some of the easier sections they'd gain important experience and the knowledge that it would take to accomplish the more difficult parts.

Many consider the great flood of 1953 to be the impetus for the Deltaplan. The disaster provided incentive, but the works were already in execution phase when the flood came.

The complex of waterways that was the mouthing of the great northern-European rivers could not be protected by normal reinforcement of dikes, and one of the primary goals of the Delta Works was to shorten the country's coastline by about 700 kilometers. A series of dams and storm-surge barriers either shut off tidal areas or stood prepared to do so in emergency.

Inland ports had to be allowed their commerce; and rivers must flow to sea. The harbor at Rotterdam is the busiest in the world. In order to maintain its operability, and protect land from sea, there was required a means of opening and closing the great river — a gate. That is in fact what the Maeslantkering is. The Maeslantkering, on of the largest moving structures on Earth, is a computer-operated shutoff gate. If the machine's algorithm determines that a dangerous storm-surge is likely, it will close the barrier. The mechanism is based upon two semi-circular walls that maneuver into position floating and pivoting on huge ball-joint anchor points. Filled with water, they sink and isolate the tidal outer sea from the inland river area. This capacity is of course only temporary because the river keeps flowing seaward -- but in theory the time required to await the passage of a low-pressure sea-level-raising storm system would be brief enough that river-water could be released soon enough to avert flooding.

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• The Christian Democratic Party in 2007 proposed construction of a huge polder in the North Sea — an area of land claimed from water to encompass as much as 100 square kilometers.