Pier Perfection (Or Maybe Knot?)

For day 10, we woke up early for our hour-long bus ride to Deltapark Neeltje Jans, located in the Zeeland region. The museum is dedicated to the aftermath of the Flood of 1953 and the Delta Works projects that followed. It specifically focuses on the Oosterscheldekering (“Oosterschelde Barrier”) and how it was constructed. After the horrific flood, the Netherlands were determined to prevent any and all catastrophes going forward. So, the Delta Works were proposed in order to shield all of the major inlets from the North Sea. The dam and surge gates built in the Oosterschelde estuary were the most difficult and expensive segment of the Delta Works.

The challenge with constructing the Oosterscheldekering was the complexity required to build a permeable barrier. While a fixed dam could have been built, many people protested this idea because of the disastrous effects it would have on the marine wildlife in the estuary. A fixed dam would have prevented the tidal cycles that are so important to organisms like mussels, and would have also caused the water within to lose its salinity over time, completely shifting the delicate ecological balance of the area.

So, the engineers of the Netherlands got to work on designing a barrier with operable sluice gates that would still allow for the natural flow of water to continue. The Oosterscheldekering is a marvel of engineering comprising 65 concrete pillars and 62 steel doors. To begin, the entire seabed had to be compacted by massive vibrating needles. Then, several giant mats, which were made of rocks put in metal baskets and sandwiched in between two layers of plastic-based textile, were laid along the seabed to provide a base for the pillars to be placed on.

Each gargantuan pillar weighs approximately 18,000 tons, the same weight as about 230,000 people. These pillars were built in artificially made pits surrounded by dykes. When they were complete, the dykes would be destroyed and the pits were flooded so that a specially designed ship could sail in, pick up, and place the pillars one by one. There was a very small margin of error for the placement of the pillars (approximately 15 cm) so an anchored boat would guide the transport ship into place, where it would dock and then gently lower each pillar on top of the mats.

Then, the sluice gate was inserted into each pillar and reinforced concrete beams were placed in between them on the sea floor. Afterwards, 15 million tons of imported rocks were carefully placed around the pillars to anchor them in place and a highway was installed atop the piers, thus marking the end of the decade-long construction of the Oosterscheldekering.

Notes on Sustainability

There are very specific criteria for when the Oosterscheldekering sluice gates are allowed to be lowered as defined by Dutch law. The water levels must be over three meters above sea level (for reference, the Flood of 1953 was 4.2 meters above) for the gates to be completely closed, which prevents the unnecessary waste of energy and also places an emphasis on preserving the well-being of the wildlife that so heavily depend on the tide and brackish water of the Oosterschelde estuary.

Another this that I found especially interesting about the Oosterscheldekering was that it was initially projected to last for 100 to 200 years. However, with the continued rate of climate change and rising sea levels, it’s now estimated that it will only continue to operate as a permeable barrier until 2070, when water levels will rise so high that they will be touching the bottom of the flood gates when they’re in the raised position. Unfortunately, the Oosterscheldekering cannot be modified from how it was originally built, so it won’t be able to adapt to the change in sea levels even if it needs to. However, it shouldn’t have to – instead of focusing on addressing the consequences of climate change, we should work towards stopping the root of the problem to mitigate all of the other issues it causes.