Dellewal Terschelling: Stunning Example Ancient Building With Nature

Panorama of the port of West Terschelling and constructed mudflat
Panorama of the port of West Terschelling and constructed mudflat

For most of us, the summer holiday is already long gone. So for me also. Still there is an observation I made that I want to share with you. We have been sailing on the Waddenzee1 this summer. Sailing, anchoring, mudflat hiking2, counting seals and other animals. One of the highlights was a visit to the island of Terschelling. A lot has changed since I was there last time with our boat. It must have been at least 30 years ago. At that time, we had to moor against the quay wall wherever one could find a spot. Now, there is a modern marine in the back of the port, specially made for yachts. Although stacking the boats next to each other is still the standard.

Port of West Terschelling and the new marina
Port of West Terschelling and the new marina

The new marina is more or less in the same area where we used to moor. From there you have an excellent view on a mudflat, that has been there been for ages3. When I was young, I couldn’t understand what its purpose was. Only that old fashioned Dutch flat bottomed boats were still allowed to anchor and stand dry. For us kids, it was an excellent place to muck about with our little dinghy and get dirty walking on the mudflat. We just enjoyed it was there. I still don’t know the exact name of the mudflat. I’ve seen it called ‘Dellewal’, although that seems to be just the quay side over there. Other names that I found on charts are ‘Oostelijk Ras’ and just ‘De Plaat’. Enjoying a nice sundowner and contemplating life and dredging in particular, I suddenly saw the purpose of the area: it works like a ‘Spuikom’4. I really don’t know how to translate this in English. So, let me explain what it is intended for.

Explanation on the working principle of a ‘Spuikom’
Explanation on the working principle of a ‘Spuikom’

Basically it is a part of the mudflat that is located at the south of Terschelling. About 85 ha in surface area, it is separated from the Waddenzee by a low dam. Just high enough to the high water level in the neap tides. The dam has an opening at the back of the harbour, near the marina. I Noticed that the water outside the marina was rushing by and the water inside was practically standing still. I figured out that the rushing tide was used to flush the old port. The huge surface area stores a lot of water that has to pass the quay in the port. Effectively increasing the flow velocity there and reducing sedimentation. This certainly helps in maintaining a navigable depth for marine traffic. Moreover, as each tide the area is filled from all around the dam and mostly emptied through the port, there is a resulting nett transport out of the port.

Hjulström diagram for particle transport in streams (Credit: Wikipedia)
Hjulström diagram for particle transport in streams (Credit: Wikipedia)

Voila, that is why the old islanders build those dams! Any other person would be satisfied with this plausible answer. Have pity on me, I can’t stop solving the riddles of the sands. Wouldn’t this be easier with a dredge? Apparently, near Terschelling, there is a sedimentation rate of 0.5 to 1 mm per year5, or about 600 m³ annually. With the dam, this has to be kept out of the port with the volume behind the dam. The average increase in flow is about 0.5 knots. According to the Hjuström diagram6, this will transport particles smaller than 10 mm out of the harbour. The stored volume has a potential energy as in a power dam of about 6.25 GJ. This is released twice each tide, resulting in a delivered power of 280 kW. Combined, this results in a specific transport power consumption of 4000 kW/m³/h. No contractor in his right mind will ever use a machine with such a performance. BUT: the energy is free and working flawlessly for at least 200 years. I still have to see a machine doing that. OK. We can step up the analysis even further. Drawing the 280kW continuously from the tide is eventually slowing down the rotation of the Earth. Just for those worried: each year, one day will be in the order of 10-19 seconds longer…

The moon decelerating earth’s rotation by tugging on the tides (Credit: NASA)
The moon decelerating earth’s rotation by tugging on the tides (Credit: NASA)

References

  1. Wadden Sea, Wikipedia
  2. Mudflat hiking, Wikipedia
  3. Landschapsvisie Baai Dellewal Terschelling, Feddes Olthof
  4. Spuikom, Wikipedia (Dutch))
  5. Slibsedimentatie in de kwelders van de Waddenzee, Arcadis
  6. Hjulström curve, Wikipedia

See also

2021: Muddling Along To A Healthy Year In Dredging

Calendar picture of a sunny dredging site
Calendar picture of a sunny dredging site

Dear readers, I sincerely wish you all the best for this new year. As things are looking positive on the vaccine front, we should keep testing negative this year. There are lots of items and events to look forward. Last year was not quite what we’ve hoped for and wished each other.

I do hope all of you are OK and are still together with your loved ones. I am fortunately in that respect. So, next to the Covid situation, there were a lot of other noteworthy items. Most of them have been featured here on Discover Dredging. My trip to Bangladesh, just before all the lockdown measures. The graduation of Carsten1 and Omar2 that were completely over Teams. Some attention to our Damen Dredging Experience3. And some other items. Did you enjoy the Donald Duck review?4

Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)
Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)

One sad event was, the last issue of Dredging and Port Construction5. We’ve had to say goodbye to our trusted DPC. Although by now, there has been a kind of digital revival on the CEDA Website6. They opened up a section for Industry News, edited by Namrata Nadkarni. It stands out from the other online media covering dredging as there has been some attention to smaller topics, that would normally not get covered. As I think it is a good initiative, I urge you to subscribe and also participate by sending them any noteworthy news items for publication. Not specifically the usual company press releases, but also the more thought provocative opinions and perspectives on the activities of our dredging community. Active participation could make this CEDA Industry News flourish this year.

Announcement of the CEDA Industry News section (Credit:CEDA)
Announcement of the CEDA Industry News section (Credit:CEDA)

Further personal activities within CEDA are the Dredging Management Commission7 and I am looking forward to the exciting new concept for the CEDA Dredging Days8. Will you participate? Also, I already took the course on ‘Dredging for Sustainable Infrastructure’9, but you should keep an eye out on the next instalment, coming soon10.

A continuation from last year on my Discover Dredging will be some more articles on our Damen Dredging Experience. There are still some exhibit left to review and teaser:… There are some new exhibits arriving! Hope to have that covered when the pandemic will fizzle out we can show you around through our museum. And I hope to continue on pump and dredge technology.

Overview of the Damen Dredging Experience
Overview of the Damen Dredging Experience

Currently, there are some students working on their graduation thesis. Their very interesting topics will be highlighted here as well. Some others will start soon. When you are looking for a fun place to have your internship our your graduation, you might consider a visit to our career page11 or contacting Frank Bosman for any opportunities. Although most positions are filled at the moment, later this year we would welcome fresh brains again.

As our offices will be closed for regular work, I will be working from home most of the time. Probably most of you will do likewise. To keep track of the passage of time over the days, you should have a calendar. As a special service to my audience, I was granted the use of a set of beautiful pictures to create a calendar. You can download the file here and with some DIY skills you should have some original wall decoration for this year.

Stay healthy and stay safe. Hope to see you later this year.

Selection of calendar pictures
Selection of calendar pictures

References

  1. Graduation Of Carsten Markus: Designing And Casting Of Impellers, Discover Dredging
  2. Graduation Omar Karam: Rock Cutting The Egyptian Way, Discover Dredging
  3. Selected articles on the Damen Dredging Experience, Discover Dredging
  4. Book Review: Donald Duck A Muddy Fine Business; Artistic Equipment Design; Discover Dredging
  5. The Last Dredging And Port Construction Magazine, The End Of An Era; Discover Dredging
  6. Debut of CEDA Industry News section and monthly newsletter, CEDA
  7. Selected articles on the CEDA Dredging Management Commission, Discover Dredging
  8. Call for Papers for CEDA Dredging Days 2021 issued, CEDA
  9. Book Review: Dredging For Sustainable Infrastructure, Discover Dredging
  10. 2nd Online Course Dredging for Sustainable Infrastructure planned for March 2021!, IADC
  11. Welcome to the best years of your life, Damen

See also

Book Review: Dredging For Sustainable Infrastructure

‘Dredging for Sustainable Infrastructure’ (Credit: CEDA & IADC)
‘Dredging for Sustainable Infrastructure’ (Credit: CEDA & IADC)

Last week, I attended the last sessions of the ‘Dredging for Sustainable Infrastructure’ course, jointly organised by CEDA1 and IADC2. This course is intended to quickly absorb the contents of the book of the same name3 and have a hands on experience of the novel methodology proposed. The book has been written by many different people as members of the participating organisations. As such, it is the condensed knowledge and ideas of the dredging community on a modern approach to infrastructure projects. Although there is a straightforward structure in the book, the publishers initiated courses as an introduction to the book.

Structure of the book (Credit: CEDA & IADC)
Structure of the book (Credit: CEDA & IADC)

As Covid-19 swept across Europe and thwarted the intended live course days, the sessions were postponed and eventually held online. The presenters, Erik van Eekelen, Thomas Vijverberg and Mark Lee did a good job of introducing us to the book and supervise us in the break out working groups. The central storyline of the working groups was the harbour expansion of the fictional port of Tomigo in the fairy land of Quandany. Each of the participants was assigned a role to represent the consultant, the fishing community, the nature conservancy organisations, the power plant etc. A revelation for me from this interaction is how easy you are inclined to be egocentric in the defence of your interests. With just a little more attention to the other interests, there might be much better opportunities for yourself and for the whole of the project.

New harbour basin development at the port of Tomigo (Credit: CEDA & IADC)
New harbour basin development at the port of Tomigo (Credit: CEDA & IADC)

The incentive to produce a book on this novel approach in dredging projects was the UN initiative to launch 17 Sustainable Development Goals4 and the book addresses most of these goals. If we can truly lift the proposed working procedures into an industry standard or even a social mentality, this will be a paradigm shift from where the project was the centre of attention to: ‘Where can nature and society benefit from an economic requirement?’ The next step will be from philosophy to action.

United Nations ‘Sustainable Development Goals (Credit: United Nations)
United Nations ‘Sustainable Development Goals (Credit: United Nations)

The focus of the book is very much on the initial stages of a project: include sustainability on the basis of the design of a project, demonstrating options for sustainable solutions suggestion of sustainable techniques. As a dredging equipment manufacturer5, most of the topics will not affect my daily work. Still, in the work group sessions, it was interesting to see the interaction between the various parties that are involved with the initiation of a project. As a dredge builder4, we usually meet the requirements for the equipment applied. Though, the technical solution to achieve this might be not the most commercial solution. However, the book makes it clear and provides examples, that taking all aspects of a project into account, including social and nature opportunities, the benefits of a sustainable approach of a project might still make a viable business case.

Three pillars of sustainability (Credit: CEDA & IADC)
Three pillars of sustainability (Credit: CEDA & IADC)

The verdict on the book: it is a reference book. And as such it is very tiresome to plough through. However, the course is very enlightening as introductory lectures into the contents. Then the meticulously compiled information starts to live. Don’t depend on the courses alone, also leaf through and note all the valuable tables, graphs and diagrams, especially the guiding boxes that can assist you in setting up your dredging project. It definitely belongs on your bookshelf.

‘Dredging for Sustainable Infrastructure’ in our bookshelf
‘Dredging for Sustainable Infrastructure’ in our bookshelf

References

  1. CEDA and IADC launches new ‘Dredging for Sustainable Infrastructure’ Course, CEDA
  2. Online Course ‘Dredging for Sustainable Infrastructure’, IADC
  3. Dredging for Sustainable Infrastructure, CEDA&IADC
  4. The 17 goals, United Nations
  5. Damen Dredging Equipment, Damen

See also