The barrier consists of huge ports that move simultaneously at the same speed.
The barrier functions as follows:
When the water level exceeds more than 3 m from the surface of the water, then the moving parts of the barrier are activated. The waterway with a width of 360m can then be completely closed. At first sight, it is almost unbelievable that such a barrier is capable of such an achievement. The Maeslant barrier has a length almost as the height of the Eiffel tower and weighs about four times as much. It is the only storm surge barrier in the world with such large movable parts. Each of the mobile ports has length equal to 240 m. Normally, the doors are fully open so that ships to access the harbor of Rotterdam. When the barrier is open, the doors are disposed along the two banks of the river.
During inclement weather, the special sockets of the doors are flooded and start to float. Then, they slip into the sea by means of a traction mechanism and this procedure lasts about half an hour. When the doors are now in the middle of the river, special valves open when the flooding ports sink downward due to their increased weight. In the bottom there has been constructed a reinforcing concrete layer, while a large amount of sludge is concentrated on it. To completely seal the waterway mobile ports of the barrier must be in perfect contact with the bottom concrete layer. The ports are not placed immediately above in this layer, but essentially are suspended just above them. The speed of the flow due to reduction of the flow area becomes so strong that the sludge is entrained away. After approximately an hour, the doors can be placed on the concrete layer which is mud free. The water level in the sea then becomes higher than the water level of the river side. The force applied to the doors during a storm is about 350 MN and this force is equal to the weight of 350,000 strong men weighing 100 pounds each. Furthermore, the difference of pressure between the sides of the doors is so big that a ship of equal dimensions with the barrier would be reversed immediately.
The Maeslant barrier is necessary for several reasons. It is the most important measure for the protection of Rotterdam and the surrounding area, while the seawater threatens more and more land due to the rising sea level.
The mobile gates of the barrier are actually a human achievement. However, the Maeslantkering barrier is controlled by a computer. In case of a storm, the decision whether or not to close the barrier is obtained by a computer system (BOS) since the probability of errors is greatly increased if people were to take that decision. A computer will follow the predefined procedures and does not take last minute decisions as it is not affected by poor environmental conditions. The system takes into account only the water conditions and the weather forecast bulletins. According to these, it estimates the expected levels of water level in Rotterdam, Dordrecht and Spijkenisse. When the system BOS decides to close the barrier, it gives orders to another computer system BES. This system works completely automatically, but it remains under the constant human supervision on the procedures followed.
Watch the video provided under media below!