I hadn’t heard of Rotterdam’s equivalent of the Thames Barrier, but after reading some news on the latest flood threats, found this on Flickr.
Maeslant Barrier closed in the rain
Maeslant Barrier closed in the sun
All originally uploaded by dut97
Where some interesting details are included in the description:
During water levels of 3 metres above Amsterdam ordnance zero, the arms of the barrier are activated. The waterway, with a width of 360 metres, can then be closed completely. At first sight, it is almost unbelievable that such a barrier is capable of such an achievement. The Maeslant barrier is almost as long as the Eiffel tower and weighs about four times as much. It is the only storm surge barrier in the world with such large moveable parts. The storm surging doors have a length of 240 metres each. Under normal circumstances, these doors are fully opened, so that the ships have access to the port of Rotterdam. The doors are stored in docks with a length of 210 metres, which lie along both shores.
During storm tide the docks are flooded and the hollow doors begin to float. They are driven into the water by means of a small train. This lasts for about half an hour. When the doors are situated in the middle of the river, valves are opened and as a result the doors are flooded. Consequently, the doors sink to the bottom because of their weight. On the bottom, there is a concrete threshold. A lot of silt gathers on this threshold. To close the New Waterway properly, arms need to be positioned exactly on the threshold. The doors do not sit directly on the threshold yet, but are hung a little above them. The current under the doors becomes so strong that the silt is washed away. After about an hour, the doors can sit flat on a silt-free threshold. The water level on the seaside is then higher than the water on the riverside. The force against the surging wall during a storm is about 350 Mega Newton: this is equal to the weight of 350,000 strong men, carrying 100 kilograms each. The pressure difference is so large that a ship of equal measurements would capsize instantly. The unique shape of the barrier prevents this from happening.
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