clog blog: De Maeslantkering

This weekend we took a chance with the weather and went to find the Maeslantkering!

We took the train from Rotterdam to Hoek van Holland and then cycled the 3 km to the storm surge barrier. For the first time we took our bicycles with us on the train! We had to buy a ticket for our bicycles and the best place to sit is the special bicycle compartment that has more space to accommodate bikes. Once at Keringhuis, the information and visitor centre, we took a tour of the barrier itself.

The Maeslantkering is the storm surge barrier on the Nieuwe Waterweg that protects the Port of Rotterdam and the province of South Holland (where we live). As you might know, 40% of the Netherlands is below sea level and flooding from the sea is a constant threat. Rotterdam is 1 m above sea level but the lowest point is at Zuidplaspolder near Nieuwerkerk aan den Ijssel at ~6.7 m below sea level. Even though the coast has been fortified and there are many dykes and polders to help deal with changes in water, flooding events still occur. In 1953 the North Sea flooded after heavy storms and waters rose 5.6 m above sea level. 1835 people died in the Netherlands and there was much damage. It was decided that a flood of this extent should not happen again and the idea for the Delta Works was born. The original idea was to extend the dyke system, however 20 000 houses would have to be moved along the 800 km of the intended area making it logistically and economically unfeasible. Eight hundred kilometres sounds like a lot but there is already over 17 000 km of dykes in the Netherlands that require yearly maintenance!

The Maeslankering is part of the Delta Works, an extensive project spanning 50 years of construction and several provinces to protect the Netherlands from the sea. This storm surge barrier is different to other storm surge barriers in that two arms swing across the river and consequently the river is not blocked at all. This was an important criterion for the design and construction of the barrier as it is used heavily for shipping and would negatively affect the Port of Rotterdam should this part of the river be blocked.

Each arm of the barrier is composed of a ball and socket joint to allow it to pivot into the river, steel trusses which make up the arm and the gate. The arms were constructed 6 months apart to ensure supplies of all the materials needed. Each arm is as long as the Eiffel tower and has twice the amount of steel! Wow! The ball and socket joint is 10 m in diameter, weighs 680 tons and had to be precise to within 0.5 mm, a feat of engineering in itself. Only one European steel manufacturer said they would attempt it, Skoda Works in the Czech Republic, and they got it spot on. The ball and socket joint is encased in concrete with immense concrete and steel rod foundations. 52 000 tons of concrete were used for each arm! All the concrete made in South Holland over a period of four days was used when constructing each arm. That is a lot of concrete! The steel trusses are 237 metres long the main tubes of which are 9 cm thick and 1.8 m in diameter, big enough for an adult to stand in! Each gate is 210 m long and 22 m high, high enough to reach to the bottom of the river (17 m) and provide 5 m of protection against rising waters. The whole structure is painted white not only for visibility but to reduce expansion caused by heat. The whole arm only expands by 20 cm in the summer compared to the Eiffel tower which is 1 m longer in summer than in winter.

Construction of the storm surge barrier took 6 years from 1991 to 1997 when the Queen officially opened the barrier on 10 May 1997. The Maeslantkering is expected to be needed only every 7 years or so but is tested every year to make sure everything is in working order. Maintenance is performed every year between March and September and the barrier is tested at the end of the maintenance season. This year’s date is set for the 24th of September. The barrier will only close when water levels rise to 3 m above normal sea level. So far the barrier has only been used once in 2007 when the water rose to 3.2 m. A computer controls the system and measurements are taken every 10 minutes to determine whether it is necessary to close the barrier. The computer decides 24 hours in advance if the barrier will close giving enough time for everyone involved to be present and to give the Port of Rotterdam some notice. An unscheduled closure, i.e. every closure except the planned once a year maintenance closure, costs the port 5 million euro’s, ouch!

It takes 30 min for the arms to reach the middle of the river and 1.5 hours for the gates to be filled with water and drop to the bottom of the river. The barrier will then be closed for at least 12 hours. The barrier can only be closed for 36 hours at a time otherwise the water moving out of the river into the ocean will get too high and also pose a problem. After 36 hours the gates are lifted up to allow the water to flow out and are then dropped again if necessary.

It was so interesting walking around the area today and seeing this massive barrier, truly an engineering feat. But it made me more than a little weary of living below sea level! Water is constantly being pumped out of the low lying areas into dykes and polders which then flow out to the sea. If these pumps had to stop or be switched off, the province of South Holland would flood in 72 hours. What a scary thought! I feel a little safer knowing we live on the third floor. But there is also a balance of water, if it is too dry the dykes which are mostly made of peat will crumble. This April was particularly dry apparently and the dykes had to be sprinkled with water because the water table got too low.

After exploring the barrier area we wanted to explore Hoek van Holland and see the beach there but it was raining quite a bit and quite windy by this stage so we gave it a skip. Cycling in the wind is not ayoba! On the next rare sunny weekend day we will have to go back for more exploring!

In other news this week, Bron got her first real pay check! Woohoo! Since I have a FlexDelft contract at the moment I can be paid every week on a Tuesday if I get my signed time sheet in by Monday afternoon. This will probably change when I have a real TU Delft contract. Something I forgot to mention in the last blog was how much leave I get. A standard work week is 38 hours and standard annual leave is 232 hours or about 29 days. But if you choose to work 40 hours a week, you get an extra 90 hours leave! So in the 7 months of this contract I will have about 23 days leave which is more than most people get in SA in year ‘~) A lot of people here work a 4 day week though, then they get 90 hours less leave a year.

Later this afternoon we are going to watch the new Harry Potter movie. Hoping it is a goodie! At least we know it will have a real conclusion this time…

Hope you are well and having a good weekend! Please leave us comments! We would love to hear from you!

On the train with our bikes! Marph came with too =)

What the barriers look like when they are closed. No, they were not closed when we were there! We would not have gone in a storm... and you can't get very close when the gates close because the surrounding area was designed to flood to keep curious onlookers (read the media) away!