Tag: lab experiments

Veni!

Large populations near the sea are vulnerable to coastal floods, making coastal safety and sustainability an urgent societal priority. This is especially true in the Netherlands, where over a quarter of the country lies below sea level, and the main protection from deadly coastal floods is a barrier of wide, high sandy beaches and dunes. However, this sandy buffer is constantly moving and chronically eroding. To plan effective future coastal adaptations, we need to know where that sand is coming from, going to, and which paths it takes to get there. I am delighted to share that I have just received a Veni grant from the Dutch Research Council (NWO) to investigate this!

Where is the sand on beaches going, and how does it get there?

My overarching goal is to enable effective sediment-based climate adaptation strategies for vulnerable coasts. To approach this, I consider coasts as an interconnected network of sediment pathways, like a subway map showing how stations are linked. This connectivity reveals the hidden structure underlying chaotic sediment pathways through coastal systems. These pathways are immensely difficult to identify on real coasts due to the challenge of tracking individual sand grains from multiple sources in such a dynamic environment.

Proof-of-concept connectivity analysis of a beach and harbour.
(a) Map of tracer particles in example SedTRAILS model from 7 different source patches at a snapshot in time. (b) The number of particles (np) from a given source in each receptor is counted to yield a connectivity matrix, graphically represented by a connectivity network diagram (c).

To deal with this challenge, this grant will enable me to develop both a scale model in a physical laboratory and a numerical model in a digital laboratory. In a wave tank the size of an Olympic swimming pool, I will construct a beach from multi-coloured sand. As waves disperse the sand, the resulting rainbow of sediment will reveal their pathways, which I will then quantify as a network in the digital laboratory. The resulting open datasets and numerical models will serve as a benchmark for the coastal research community, generating new theories and improved tools. My collaborators in the Netherlands, US, and New Zealand will help me to implement these findings in research, engineering practice, and coastal management policy. In this way I hope to enable more effective management of sediment for coastal adaptation and a more holistic understanding of our coastal systems.

Stay tuned for more updates once the project begins!

Can 3D-Printed Corals Help Us Prevent Flooding?

Coral reefs around the world are dying; that much is clear from the headlines we see in the news that grow increasingly distressed with each passing year. This is an ecological catastrophe, but are we also losing another key benefit of reefs? Coral reefs provide a form of natural protection against wave-driven flooding on tropical coastlines. This is partly because the physical form of the reef (often a big rocky shelf) serves as a sort of natural breakwater, but is also due to the frictional effects of the corals themselves.

Many species of coral have complex shapes that disrupt the flow of water across reefs, generating turbulence and dissipating energy. This has the effect of reducing the height of waves as they travel across the reef towards the shore. However, these effects are incredibly complex and poorly understood, so we usually just simplify them in our predictive models by considering a reef to be more “hydraulically rough” than a sandy beach, for example. But we need to do better: these models are used to forecast flooding and estimate the impact of future climate change on vulnerable coasts.

How can we improve this? In coastal engineering, we often conduct experiments in the laboratory to test our theories and understand the chaos of natural systems in more controlled settings. What if we could make a scale model of a coral reef and measure exactly how waves are dissipated?

I am extremely proud to announce the graduation of Paul van Wiechen, one of the Master’s students whom I have had the pleasure of supervising. Yesterday, he defended his thesis, “Wave dissipation on a complex coral reef: An experimental study“, where he built a tiny coral reef in the TU Delft wave flume (a 30-m long bathtub with a wave-making paddle at one end) using hundreds of 3D-printed coral models.

Paul’s thesis, “Wave dissipation on a complex coral reef: An experimental study“.

It was one of the coolest projects I have ever seen, and his research provides us with valuable measurements that give us a deeper understanding of the vital role that corals play in protecting our coasts.

He also did all of this in the middle of a global pandemic, and somehow managed to stay completely on schedule. We are very lucky, because Paul will be joining the Coastal Engineering department here at TU Delft to start a PhD on dune erosion this fall. We are all glad to have him on the team and eager to see what his research unveils next!