Interview with Simon Mortensen: The Designer Behind Palm Beach Reef
The Palm Beach artificial reef on the Gold Coast of Australia was recently completed by Simon Mortensen and a team of designers and engineers. As you may have seen or heard, the artificial reef produced a few good surf sessions before the swell died for the season, even before the reef was 100% complete.
We sat down with Simon Mortensen, Director at DHI Australia, who lead the artificial reef design efforts to discuss how this reef came together.
Simon, thanks for taking the interview! Like many over in your part of the world, I’m so excited by what I’ve seen happening with the Palm Beach reef, but before we dive into that part of the chat, I’d love to know more about you. Give us a little background on yourself and how you got the enviable job of designing a reef for surfing?
I grew up surfing on the North Sea coast of Denmark at a place called Klitmøller and started surfing at age 15 when good wetsuits finally started to become available. I studied coastal engineering as a means to get an interesting job by the beach. DHI offered me a job after graduation and I was lucky to be involved with the further development of our CFD models for 3D wave breaking, which to my understanding was very much ahead of its time 12 years ago. I was allowed the opportunity to validate our CFD model against a physical model test of a simple surfing reef and published the findings to the International Multipurpose Reef conference in J-Bay in 2009 and it gave be a good foundation in how to use CFD for reef design. I remember having to run my first simulations on a 4-core machine.
I remember those conferences.The fourth one was near here in Manhattan Beach. I hope they restart one day…
Yeah, I didn’t make it to that one, but I wish I had. I didn’t graduate university before 2006. I think Manhattan was the year before.
After the 2009 conference I remember I expected the phone to start ringing, as I knew that several surfing reef projects were underway and knowing off all the problems facings existing reefs. But it didn’t. We did a couple of projects on surfing amenity impacts of natural surf spots around the world, but none involving artificial reefs. It would take 4 more years before we won the Palm Beach Concept Design in open tender against 13 other hungry engineering firms, before I got my first chance to design a reef for a paying client. You could say that it gave you a lot of time to think about how you would do it when I got the chance.
Well the timing of that conference was right around when Kovalam and Bournemouth failed, right? That scared a bunch of enthusiast off, I suspect. They aren’t the only two failures, either. Many multi-purpose reefs have failed. What was your strategy for overcoming the fears that the Palm Beach reef would be yet another failure?
One of the biggest issues was to design a reef that was not too difficult to construct and that could last for the long term in a highly energetic marine environment. Another issue was to make sure that the structure created enough wave energy dissipation to benefit sand build up in the lee. We chose rock as the construction material as it is natural and has proven its merits for hundreds of years in marine design. We also tried to design the structure to focus as much wave energy as possible from the toe towards the crest, which would increase wave dissipation. It also had the additional benefit with regards to surfing, that waves got preconditioned well for surfing. Finally we had to make sure that the peeling speed and shape was fit for purpose for the average surfer. This included a lot of time spent on design and following numerous iterations using initially primarily numerical models.
What about the political or social perspective. Do you have any insight to how you, or others on the project, overcame doubt and fear in city officials and the public?
We were lucky that during Concept Design, the City of Gold Coast project managers allowed us to co-host about 5 community engagement workshops. That allowed us very early to experience the full brute force of a at that time very concerned and passionate group of diverse local stakeholders. The Council also made sure to include a seasoned local surfer in the subject matter review panel. Early and respectful stakeholder engagement is key for any successful coastal engineering project. You need to respect the locals. Never underestimate 30 years+ of local beach knowledge.
Well your strategy worked well, so congrats. Of all the places on the Gold Coast that suffer from erosion, why did you select the final spot?
Palm Beach was selected by City of Gold Coast due to having a historic track record of a very low beach volume to resist erosion events. We chose this particular spot on Palm Beach because it was in the lee of a natural wave focusing zone from the further offshore Palm Beach natural reef. It further improved wave preconditioning and wave dissipation in an attempted working with nature approach. The location was also chosen in order to attempt to maximize its coastal protection potential along the most sensitive part of the beach.
Tell me about the design process… Did you and your team start on computers and then move into the physical testing lab, or the other way around? How many major iterations on the shape of the reef?
It always starts with an idea for a shape and a lot of studying of the local coastal processes. It involved a few surf sessions at Palm Beach too, as well as thousands of hours surfing other spots in general, really. Then follows numerical modeling which is used to provide a more quantitative investigation of suitability and the reef impact with regards to coastal response and surfing performance. Numerical models are mostly used in an iterative fashion to improve and balance the performance of the reef. It does not develop the design on its own, but it allows you to test ideas with a high level of accuracy these days. Physical modeling is the most expensive and time consuming and was used for additional validation and accuracy improvements of parts of the numerical models. It was also important for detailed design of the rock size requirements for the final design.
Speaking of rocks, why did you go with rocks instead of geo-textile containers?
Rocks have proven their resilience through hundreds of years of coastal engineering structures. The element sizes are quite small compared to the structure, which makes it relatively easy to get the design shape right as long as it is not too complex. Rock is natural and provides many small crevasses for marine habitat. To our understanding every single reef using geo-textile has suffered problems with bags breaking, shifting or sinking. Most people think that failed geo-textiles would be cheap and easy to remove, but that has not been the case. There has been cases where removal costs have exceeded placement costs.
It’s ironic: when I end up talking about artificial reefs with other surfers, our laymen conversation often touches on the simplicity of a pile of rocks. After all, many of nature’s reefs are just that. I understand the rock was quarried and delivered from the Brisbane area. Any particular reason why? Is the rock special in some way?
We weren’t involved with the sourcing of rock. In our experience it is a matter of competitive market price and handling the logistics.
We’ll I’ve heard that construction finished early so RoyalHaskoning and Heron Construction must have done a great job, given the results. Speaking of, I saw the video of the working, and it looks incredibly fun. Have you surfed it? How would you describe the wave in typical, working swell conditions? What well-known wave would you compare it to?
Yes I have surfed it and it was really fun. I can’t wait for it to prove its worth on a big swell though. There has not been a single swell above 1.5 m since it was built and it has been months since we had any swell at all really. The reef will start working good at around 1.5m offshore height and low to mid tide. Depends on period and direction. It was designed to be a right hander that most people could surf. Not too difficult in the take off and as long a wall as possible. It is always a compromise with these things. Especially since the main focus was coastal protection. Once it gets big we should see another side to the reef through. And you might get a small intense drop on the left hander.
I’ll keep an eye out for swells, reports and videos, no doubt. Any measurable signs that its improving coastal protection? If not, when?
To our understanding the nearshore is undergoing an extensive surveying campaign the following years. Please stay tuned.
I understand the reef cost around 18m AUD. Roughly where does that money go?
You have to ask City of Gold Coast, but I would say that most of this would have gone to the cost of building material and marine construction costs.
What do you think is the biggest risk to the project? Reef sinks, boulders get relocated by wave action, someone gets hurt, etc.?
I think the City of Gold Coast have done a lot to mitigate risks on this project. The size of the boulders have been comfortably sized to sustain very large wave events and precautions has been taking from settling of the structure. There are clear warnings on the beach informing of the risks associated with the reef to marine craft users. Perhaps the biggest risk is if the public conclude it overall was worth the investment.
Makes sense. What types of precautions were taken to keep it from settling?
I’m not aware of the final design considerations that went into preventing settling, but on its own such a rock structure will be able to handle quite a bit of bed movements around its toe. Even if some local deformation of the toe were encountered, it still would be unlikely to compromise any noticeable part of the overall design. Think of jetties and breakwaters that lasts more than 50 years without sinking.
What would you do differently if you did it again?
I think we would have been more realistic in our budgeting on how long it would actually take to work on this reef. The City got a good deal.
We’ll if its as successful, you have a great, unique reference point for the next project you bid. Speaking of which, any other artificial surfing reefs that you are bidding or working on?
We have done a couple of other reefs the last few years, where the projects are currently on stand-by pending further action to proceed. This is usually where it ends with these projects. We have also worked closely with Surf Lakes for several years to improve their prime break Occy’s Peak, which you might have seen some video off. I was lucky enough to be invited to surf it a few times. By far the most enjoyable team of people to work with for sure. Their founder Aaron Trevis is one of Australia’s true creative geniuses in my view.
To be honest, even after Palm Beach, I don’t really expect the artificial reef call line to buzz crazily this time either. If the public overall appreciates the design, it will probably inspire a new breed of designers that would try their own luck with numerical modeling themselves which is so much more accessible these days. In the end, who does not want the chance to design your own reef. If anything, it would be the contractors such as that Heron Hall Venture that would get the most work following this. As long as new projects stay away from geo-textile and perhaps invite me to surf their wave and quote our paper, I will be happy as can be.
I love the altruistic perspective. Are you following what’s going on with the Air Wave in WA? What are you thoughts on that project?
Always curious to follow new initiatives that does not involve geotextile bags. I hope it goes well and the structure can endure the significant lift forces and turning moments it would likely be subject to.
We’re hoping the same thing. I hope to connect with Troy, the guy behind the Air Wave, soon, so stay tuned here for an update in the next few days. Thanks for you time Simon, it’s been a pleasure, and good luck with Palm Beach.
