‘Floods could be really catastrophic’

The chances of a superstorm occurring in the Netherlands are pretty low. But the Dutch Government wants to be prepared for the possibility and PhD student Paul van Wiechen is helping by doing research on coastal dunes.

“I was born in the Netherlands, but moved to Belgium when I was six so that’s where I grew up. I came back to the Netherlands to study Civil Engineering in 2013. I really enjoyed everything related to water so that’s why I chose Hydraulic Engineering. During my master’s I became very enthusiastic about doing research so that’s one of the reasons I decided to do a PhD.

The Netherlands is a low-lying country where floods could be really catastrophic. The Dutch coastline is approximately 540 km long, of which 250 km consists of sandy dunes. These dunes act as the primary defence against storm surges. To meet the strict Dutch safety requirements, they should be able to withstand a predefined superstorm. This is a storm with a frequency of occurring of approximately one in 10,000 years, depending on which coastal stretch in the Netherlands you are looking at.

The conditions of these superstorms are known, and how the dunes respond is based on the results of laboratory experiments. Imagine a big wave tank and then at the end we have a dune that we test by shooting waves at it. Using these experiments, we know how a dune will perform in a storm. There are downsides to doing it this way because we’re basing everything on the conditions of the experiments and those wave basins are only one dimensional. So, imagine if the real waves at the coast arrive at an angle, it’s going to be different.

‘We’re actually going to test this new model’

So the Dutch Government is looking into a new type of testing which can actually include all these processes and can look more at the physical processes behind dune erosion instead of the empirical results of experiments. The Dutch Government is really looking into this and they have a new model, but within this model there are still uncertainties. And those uncertainties are basically why my project started.

We’re actually going to test this new model, which should be better than the former model, and we’re going to do that through fieldwork. We’re going to build a massive, full-size dune on the coast and then we’re going to monitor it and see whether those model outcomes actually add up with what we’re seeing in the field.

The Dutch dunes are built to withstand a superstorm, but with the chances of one occurring around one in 10,000 years it’s really unlikely. That means it’s also something you can’t really test in the field. So what we’re going to do is build a 1:1 scale dune which would significantly erode during a normal storm. It will be smaller than the dunes you currently see at the coast, but it’s the order of several hundreds of metres long and about six to eight metres high and about 30 metres deep. It’s quite impressive.”

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Heather Montague / Freelance writer