Ch-ch-ch-ch-changes

Big news to start 2023: I am now an Assistant Professor in Coastal Engineering here at TU Delft! An opening appeared online last summer, and after weeks of preparing applications, several rounds of interviews and a teaching demonstration, and a lot of waiting, I finally got the good news. This has been my dream job for a long time and I can’t believe it came true.

Officially, my new portfolio will focus on “Climate-Robust Deltas”. How does sediment contribute to the strength and adaptability of our coasts and deltas against the effects of sea level rise and climate change? In my research we approach this gigantic problem by quantifying sediment pathways and connectivity for strategic placement of sediment, using a combination of numerical modelling and field measurements. In the coming years, I hope to build up a diverse team of enthusiastic, coastally curious researchers to tackle these challenges. Stay tuned for opportunities to join our group!

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PhD Summer School Opportunity

EXCITING OPPORTUNITY ALERT!

At the end of June, we will welcome a group of about a dozen American PhD students for our second annual IRES summer school, hosted at Deltares/TU Delft/Utrecht University and organized by the University of New Orleans and The Water Institute of the Gulf in Louisiana.

Last year we hosted 14 American PhD students for two (fully funded!) weeks in beautiful Delft. It includes D-Flow FM model training, cool field trips to sites around the Netherlands, a lab session, networking galore, guest lectures, and time for exploring the area. Last year everyone seemed to learn a lot and have a pretty good time (I sure did!).  We have a great team and are excited to make it even better this year. Please share this with anyone in your network whom you know might be interested!

More details can be found in the pdf below. If you are interested you can apply here before January 27th, 2023. We will host the summer school for a third and final time in 2024, so if you are too late or ineligible this year, stay tuned for another chance next year!

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Book Club (2022)

It so happens, though – a wholly unforeseen accident – that the feel and appearance of a book when combined with a literate person in a straight chair can create a spiritual condition of priceless depth and meaning. This form of meditation, an accident, as I say, may be the greatest treasure at the core of our civilization.

– Kurt Vonnegut

2022 was an intense year in many respects, but an excellent year for reading! A few people have recently asked me for book recommendations, so here are my favourite books that I read in 2022, presented here in (more or less) the order that I read them. These are the books that sucked me in, resonated deeply, changed the way I thought, or simply gave me a big literary hug in a crazy year. This post has nothing to do with coasts but a great deal to do with my curiosity, so I thought it was still worth sharing here. I hope that you find something you like here, too!

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Tracking Sand that Hides from the Sun

Keeping Dutch feet dry is mainly done by placing piles of sand along the coast as “nourishments”. These nourishments build out the beaches and dunes to act as a protective buffer against storms. However, as was recently pointed out by an official at Rijkswaterstaat, the Dutch water ministry, the Hamvraag or “bacon question” is still “where the heck does all that sand actually go?”

Knowing where nourished sand goes is important for understanding the ecological impact of nourishments, as well as their effectiveness. If you want your sand to reach a certain destination, how much of it actually gets there and how quickly?

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Going Where No Cyclone Has Gone Before

Tropical cyclones or hurricanes threaten the lives of millions and cause billions of dollars in damage every year. To estimate flood risks at a particular location, scientists and engineers typically start by looking at the historical record of all previous storms there. From these records, they can statistically predict how likely a storm of a given size is (e.g., the biggest storm likely to occur there in 100 years).

There are two problems with this approach: (1) What if there isn’t much historical data in the records? This is often the case for Small Island Developing States (SIDS) and in the Global South. If you don’t have enough data points (particularly for rarer, more extreme events), your statistical estimates will be much more uncertain. (2) What if the historical record isn’t representative of the conditions we are likely to see in the present and future? This is also a big problem in light of climate change, which is expected to bring sea level rise and changes in storminess to coasts around the world.

To address these challenges, our team led by Tije Bakker came up with a new approach to estimating tropical cyclone-induced hazards like wind, waves, and storm surge in areas with limited historical data. Our findings are now published open-access in Coastal Engineering here!

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Sediment Pathways on Ebb-Tidal Deltas

After 5 years of blood, sweat, and tears, I present to you my PhD thesis: Sediment Pathways on Ebb-Tidal Deltas: New Tools and Techniques for Analysis! I will defend my PhD on March 8th.

How do sand and mud move around on our coasts?  This is a question that we need to answer in order to sustainably manage coastlines in the face of sea level rise and climate change. To do so, we use a combination of field measurements and computer simulations at Ameland Inlet in the Netherlands. In the course of my PhD we developed several new methods, including morphodynamic mapping techniques, a sediment composition index (SCI) derived from optical and acoustic measurements, techniques for sediment tracing, the sediment connectivity framework, and a Lagrangian sediment transport model (SedTRAILS). Together, these approaches reveal new knowledge about our coasts which can be used for managing these complex natural systems.

That’s a bit of a mouthful, so let’s break it down and try to explain what I have been doing with sand for the last half-decade…

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Custom Colourmapping

As a kid, I was obsessed with maps. Give me an atlas and I would be sucked in for hours. Eventually I wound up in coastal engineering and took a GIS course with the amazing Dr. Kate Parks in Southampton. This reignited my interest in cartography, as I now had the tools I needed to make my own maps. Over the coming years this led to an interest in how we can map our coastal regions to better communicate their morphodynamics. Also (mostly), I just wanted to make pretty maps! Making figures sometimes feels like one of the only avenues for artistic expression that we have in science.

To reach these goals, a good colourmap is a key ingredient. For a map showing the topography/bathymetry of a coast, a colourmap is the range of colours that correspond to a particular elevation. In this post, I will walk you through how I created two of my favourite colourmaps.

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Waterloo Sunset

It already seems like an eternity ago – from 2007 until 2012, I studied civil engineering at the University of Waterloo in Ontario, Canada. I was recently contacted by the UW alumni department to reflect on my undergraduate experiences for prospective students. They eventually posted their Q&A online, so I thought I would share it here too, in case anyone reading this blog is contemplating a career in civil engineering or going to UW.

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Weird waves cause big trouble on small lands in the middle of the big blue wet thing

Originally presented earlier today at the AGU 2021 Fall Meeting in the “Upgoer Five” Session, this video was inspired by the XKCD comic and book in which scientific concepts are described using only the 1000 most-common words in the English language. I participated in the session last year and had so much fun, I thought I would try it again with my coral reef research.

Unfortunately, ”ocean” and ”sea” were not on the list, so I had to go with ”big blue wet thing” instead. Want to give it a try yourself? Here is a handy tool which checks your writing to see if it meets the list of 1000 most common words: https://splasho.com/upgoer5/ It’s harder than it looks!

Here is a summary of my video:

Some small but beautiful lands in the middle of the big blue wet thing were built by tiny animals that turn into rock when they die. Although these lands might seem perfect and calm most of the time, they are actually in big trouble. The big water is going up and up and up, and the little lands could be completely under it before our kids grow old. However, they are also in trouble right now — waves can hit the little lands and make them go under the water too, even if just for a short while. These waves can hurt people and make the drinking water not-drink-able. It is hard to guess if the waves will cause trouble because they break in different ways than we are used to when they hit the rocks built by animals. The waves become longer and weirder as they move across the rocks, and can hit the land with more power than we would expect. It is even harder to guess what the waves will do because every small land made of rocks built by animals is different, and there are so many of them all around the world. To keep everyone safe, we showed a computer lots of made-up waves so that it could learn how waves look when they hit different sorts of rocks and land. The computer can then make good guesses about what real waves would do if they hit real rocks and land. If the computer thinks that the waves will cause trouble, we can warn people to go somewhere safer until the waves stop. In this way, we hope to keep everyone’s feet dry until long after our kids are old.

You can find more about this stuff in bigger words here:

1. Pearson, S.G., Storlazzi, C.D., van Dongeren, A.R., Tissier, M.F.S., & Reniers, A.J.H.M. (2017). A Bayesian‐based system to assess wave‐driven flooding hazards on coral reef‐lined coasts. Journal of Geophysical Research: Oceans, 122(12), 10099-10117. https://doi.org/10.1002/2017JC013204

2. Pearson, S.G. (2016). Predicting Wave-Induced Flooding on Low-Lying Tropical Islands Using a Bayesian Network. MSc Thesis, Delft University of Technology. http://resolver.tudelft.nl/uuid:c3988f4b-99f8-4936-9504-261b32bb0cd1

3. Roelvink, F.E., Storlazzi, C.D., van Dongeren, A.R., & Pearson, S.G. (2021). Coral reef restorations can be optimized to reduce coastal flooding hazards. Frontiers in Marine Science, 8, 440. https://doi.org/10.3389/fmars.2021.653945

4. Scott, F., Antolinez, J.A., McCall, R., Storlazzi, C.D., Reniers, A.J.H.M., & Pearson, S.G. (2020). Hydro-morphological characterization of coral reefs for wave runup prediction. Frontiers in Marine Science, 7, 361. https://doi.org/10.3389/fmars.2020.00361

Sediment Pathways in Vancouver

In the past few weeks, Vancouver and the BC Lower Mainland have suffered not just one but three record-breaking rainstorms, a succession of ”atmospheric rivers” that dumped several hundred millimetres of rain. Highways washed out and disappeared, and numerous communities were flooded. This resulted in an enormous quantity of sediment reaching the sea via the Fraser and other local rivers. But where exactly does the sediment that’s already in the sea around Vancouver go? How has that changed in the past few hundred years since Europeans colonized the area? To get to the bottom of this, we enlisted Carlijn Meijers.

Last week, Carlijn successfully defended her thesis, ”Sediment transport pathways in Burrard Inlet”. To answer these questions, she created a detailed hydrodynamic and sediment transport model of Burrard Inlet and Georgia Strait in D-Flow FM. She then used the SedTRAILS model that we have developed to visualize sediment transport pathways.

Modelled sediment transport pathways in Burrard Inlet. The red arrows highlight key patterns in the SedTRAILS particle trajectories. Burrard inlet is characterized by strong flows through the narrowest points of the fjord, and large eddies in the wider areas. Source: Meijers (2021).

From these models, Carlijn showed that sediment transport is largely controlled by flow through the First and Second Narrows (where the Lion’s Gate and Ironworker’s Memorial bridges cross). As the tide comes in, the water shoots through these narrow passages at speeds of up to 2 m/s and comes out the far side as a jet, spiraling off into eddies. The tide then goes out and the same happens in reverse, with water shooting out the opposite side.

Conceptual diagram showing the dominant sediment pathways in the Inner Harbour. Source: Meijers (2021).

Due to the sheltered nature of the inlet, waves have only a minor role in sediment transport. However, given the intensity of the tides and the great depths of Burrard Inlet (especially the Indian Arm fjord to the north), most sediment liberated by erosion tends to get carried away from shore and is essentially lost from the coastal sediment budget.

Another key point of her project was to investigate how land use changes and other human effects (e.g., damming rivers, port construction) have changed Burrard Inlet. Using the model, Carlijn showed that these changes to the inlet have shrunken its tidal prism, influencing the currents and sediment transport patterns.

Comparison of the present-day shoreline with the high and low tide lines from 1792, prior to colonization by European settlers. The Second Narrows are so narrow because they were formed by the delta of Seymour River and Lynn Creek. The area has since been dredged and walled off for the construction of the port and to create log booming grounds. Source: Meijers (2021).

These changes are especially evident when we compare satellite photos from the present day with the oldest available images from the 1940s.

Second Narrows in the 1940s and 2021. Please forgive my crappy georeferencing, I eyeballed it. Source: City of Vancouver and Google Earth.

Carlijn wrote an excellent report and capped it all off with one of the best master’s thesis defenses that I’ve seen in a long while. She also handled the cultural context of the project with great respect, interest, and sensitivity.  If anyone reading this is looking to recruit a new engineer/researcher with heaps of potential, I cannot recommend Carlijn enough.

All in all, this was a fascinating project and one very close to my heart — I was born in the Vancouver area and was excited to see how the SedTRAILS model could be used in my original backyard. Let’s keep the Delft-Vancouver collaborations going!