'A thesis is not a sprint but a marathon'

Michael Boyall wins the HZ Stern with research on mega sand replenishments

On 15 December 2021, CT student Michael Boyall received the HZ Stern for his thesis Analysing & Optimising Sand Nourishments at Walcheren. The laureate expressed his happiness with the prize via a video link: "It's great to win the HZ Stern. I wanted to finish my studies at a high level; I feel I have achieved that and even more." The conclusion of his research is that one large sand nourishment (mega-suppletion) is better than applying the same amount of sand in several small nourishments. Mega-supplementation has less impact on the environment, increases the beach area available for tourism and nature, and lasts longer; in short, it offers more value for the same money.

Kees Bal, editor HZ Discovery

The topics of sand nourishment and building with nature (see box) were completely new to him, as he had participated in the construction of a giant nuclear power plant in the UK during his last 12-month internship. But the opportunity appealed to him to explore something that would provide new insights.

He tried to think in a logical, scientific way and to be guided by the facts. "I think it's important to remain critical of your own work and to question your own assumptions. For example, I really wanted to be confident in my results for the mega suppletion, so when I got the information from the erosion climate along the Walcheren coast, I made sure I included a scenario that was much more extreme. I think this really helped to demonstrate that the design of the mega nourishments is feasible and cost-effective, even if the erosion is much greater than the current one."


Michael's path to HZ was different to that of most students, as he was 28 years old and living in Sydney when he decided to go back to university. He chose to study civil engineering. "It's a very broad field that takes me everywhere because CT people are always needed, no matter what." He believes that being older than the other students and having worked in different countries and industries helped him tremendously to do well, especially in projects and presentations. "On the other hand, I was also a difficult person to be in a group with, because I expected a higher quality of work and didn't want to cut corners."


The biggest challenge in his research (apart from the pandemic and the Brexit, which made a Christmas trip to the UK last 3.5 months and caused a lot of uncertainty) was getting the modelling software to work. The modelling laid the foundation for the rest of the thesis and led to valuable and verifiable results, Michael explains. In the end, he is most proud of his determination and perseverance. "A thesis is a marathon, not a sprint." His biggest fear in the final weeks was that his data and results were good, but that no one would understand. So he went through the report again and again to make sure that someone from the outside would understand what he had done. And he succeeded, because the jury of HZ Stern also complimented him on the high degree of readability. Good solution

If a mega-suppletion is carried out in Zeeland in the future, Michael will be pleased about it. "It is a good solution, provided the location is right. The economies of scale that a mega nourishment offers are really very important." At the moment, however, Michael has joined the French company EDF and is working in the nuclear design organisation. "These are exciting times as a number of new plants are being licensed and EDF is looking to export its nuclear expertise around the world. Right now the sky really is the limit for my future. I expect to work in many different countries."


Does Michael have any advice for ambitious HZ students? "I think the best students are not necessarily the smartest, but the most organised. Make the most of the opportunities you get and don't expect a university to hand you everything on a silver platter. You have to work for it yourself." And for a thesis, it's important to see it as a whole package: each part of the package must be of high quality and fit with the other parts. "Good work is useless if someone else doesn't understand it and you don't present it well."

Analysing & Optimising Sand Nourishments at Walcheren

The report examined the cost-effectiveness of sand nourishment, both in relation to 'hard' coastal defence and to the size of the nourishments themselves.

Sand nourishments are used in many places to protect the coast and widen the beaches for tourism and nature. Coastal defences are becoming increasingly important due to the rise in sea level and the ever-increasing concentration of population in coastal areas. The risk of flooding is increasing while the consequences are also growing. The expectation is that more and more work will be done on coastal defence, which makes it important to look closely at cost efficiency.

Michael Boyall's research focused on two topics. The first was a comparative analysis. On Walcheren, sand nourishments have been carried out on a large scale for 40 years, but it is not known whether it would have been cheaper to construct and maintain dunes or dykes instead.

The second part of the study examined so-called mega-suppletions. Is a much larger-scale sand suppletion with a lifespan of around 20 years feasible along the Walcheren coast? Mega-supplementation is less environmentally damaging and cheaper, but the concept is still new. It is a subject of debate whether mega-suppletions (such as the 'sand motor' near The Hague) are also suitable for other areas.

The conclusion of the first question was that the Dutch 'soft where possible, hard where necessary' approach with sand replenishments is more advantageous. Not only do they provide the required safety, but they also enlarge most of the coastline, reduce maintenance and increase the beach area for recreation.

The second conclusion is that mega-subtractions offer better value for money in terms of lifespan and beach width compared to individual sand replenishments. This can be seen in the following example for the beach near Domburg. A mega-suppletion that costs as much as all sand suppletions in the period 2000-2019 would have a width of 275 metres (dry beach and intertidal area of 137 metres). This mega nourishment would have a half-life of 15 to 30 years and after 20 years a width of 160 to 200 metres would remain. It therefore offers protection longer than until 2019. A smaller mega replenishment (200 metres wide, a half-life of 10 years, and a width of 100 metres after 20 years) would have sufficed to provide protection 'only' until 2019. Such a mega replenishment is 6.24 million euros cheaper than the total cost of all sand replenishments between 2000 and 2019 at this location.

In addition, mega-suppletions reduce the impact on the environment and increase the availability of the beach for tourism and wildlife.