Polder

A polder is an artificial ground extent whose level is lower than that of the sea. The polders are carried out by drainage causing the draining of Marais, Estuaire S, of Lac S, or littoral zones . The Netherlands are often associated with the polders, since most of their surface was gained on the sea during the centuries (see Géographie of the Netherlands). Such zones also exist in the Northern of France in the area of the Watergang S or Wateringue S (of Dutch ways of water ; to pronounce ouatringues ), close to Dunkirk.

There exist also river polders, natural extents in the zone of flood of a river, arranged in polder by a system of drainage.

With the probable rise of the oceans, certain Dutch polders are or will be returned to the sea.

The point low of the French territory (- 4 m) is located on a polder in a named commune of the district of Dunkirk Moëres (of Dutch moeren which means marsh ) One finds also projects of polders or industrial polders in work in Japan, in bays of Tokyo and Osaka, which are in the middle of the Japanese megalopolis

The Netherlands and polders

The progressive draining was often carried out by pumps actuated by windmills. The first polder of this type was the Polder of Beemster in septentrional Holland in 1612.

The technology of construction on sea developed by the Dutch is with the world point. Thus, it is a Dutch subcontractor who currently carries out the Palm Islands with Dubai in the Arabo-Persian Gulf.

Origins

Before the polders directly taken on a stretch of water, the adventure started in the Marais. The latter, in the beginning simply drained by rivers were exploited for agriculture and the Tourbe in period basic water and given up in period of rising. The subsidence, due to the human activities, making the floods more frequent, one started by building Digue S of protection isolating the marsh from the river. Basins of drainage were added for, in period of rising, to contain infiltration and rainwater, in basic period water, the basins being emptied simply in the river. The ground continuing to subside, this solution was not sufficient any more.

The first windmills made it possible to obtain a more important water level in the retaining tanks than in the polder. The level of low waters not being more sufficiently low to empty the basins, those became simple channels of drainage by means of additional mills functioning all the year.

See too

Simple: Polder

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