Reclaiming land

Safeguarding knowledge = reclaiming land

Mangroves form natural coastal protection along the Asiatic coast. These forests are extraordinary and unique areas of natural beauty. The roots of the mangroves reclaim land while also serving as breakwaters. In some places, the trees flourish of their own accord, but in others, nature needs a helping hand. Researchers from the Faculty of Civil Engineering and Geosciences explore the various qualities of mangrove trees, and attempt to determine the best approach for the Asiatic coast. Consulting existing academic sources is not always easy, as Henk Jan Verhagen, Associate Professor in Hydraulic Engineering, explains.

Henk Jan Verhagen

Henk Jan Verhagen in the water lab

‘Mangrove forests are difficult to access. It is only possible to work there when conditions are calm, while we actually want to research what happens during cyclones. In order to research precisely which mechanisms come into play when water flows through a mangrove forest during a storm, we created 3D scans of a mangrove tree during our collaborative project with the National University of Singapore <>. We used a 3D printer to create scaled reproductions of these scans, which we then placed in a tank in our Waterlab. We subsequently conducted measurements and found that different types of current are created when using scaled models. However, the turbulence of the current does not decrease in line with the geometric scale. So you are actually measuring something else in the lab than in field conditions. The extreme natural circumstances and alternate lab conditions mean that a limited amount of data is available, including in the Library collection’.

‘My students do look for information in the Library, but are not always naturals when it comes to searching the collection. If you search for ‘mangrove forest’, the majority of the references are concerned with biology. And even if you search our own repository, a search for ‘mangrove’ returns 383 hits, and most of the biological literature has already been filtered out. Students have difficulty extracting the relevant literature from the large number of elements. I always suggest that they make sure they have the names of the scientists, and start their search using them. Instead of focusing on the subject. Once you find publications by relevant scientists, you will find useful reference lists, allowing you to look in the correct web of information’.

Tips from the Library:

By using the term ‘mangrove forest’, you immediately make your search very specific. It is a good idea to widen your search, by looking for ‘flooding’ in a range of forested areas, for example. It is likely that a wider search will uncover information that is useful for the research specifically examining mangrove forests.

Searching for names of scientists is indeed another potential strategy for finding information and articles. Such names are often available from the existing network, and a wide, generic search could help track the names of other scientists. Locating a summary article (review) can often result in new leads. Reviews outline the most recent state of affairs in a particular field, and contain a vast number of references.

Coast near HaiPhong, with young mangroves in front of sea dike with revetment blocks

Coast near HaiPhong, with young mangroves in front of sea dike with revetment blocks (photo: HJ Verhagen)

‘Back to the mangrove forests. Of course, it is not the case that absolutely no expertise on the protective function of mangroves is available. We are using several methods to research the subject. Moreover, the coastal managers possess an enormous amount of practical experience, unfortunately it is not their job to share their expertise in scientific journals. Which means that their knowledge remains local. The Netherlands is naturally also home to a great deal of knowledge in the fields of coastal protection and land reclamation. Although it is a completely different context, the Wadden Sea offers a comparable situation: a situation in which we wanted to promote accretion, in this case by using dams and mud-flats (salt marsh works). In the beginning, it was also a matter of trial and error. And you actually learn the most when things don’t go to plan, as you subsequently have the opportunity to improve your theories and constructions. However, such moments are never properly scientifically documented, and there are hardly any experts left from back then for us to direct questions to. Excursion reports, internal reports and articles from non-scientific journals do contain a lot of information. Data that you could also apply in a scientific context. However, these documents are not as well indexed as scientific articles and searching for material can be very difficult. Searchable key word indexes, for example, would be helpful. But they simply do not exist.

You learn the most when things don’t go to plan

Another resource are internal reports from organisations such as Deltares and Rijkswaterstaat. Again, they are also difficult to access. In order to facilitate the process, we add a lot of these kinds of reports to our repository in their entirety. For example, 34 ‘grey’ reports about salt marsh works are currently available online at: (select ‘Hydraulic Engineering Reports’ under ‘Collection’)’.

Tips from the Library:

One option could be to chart the subject of mangrove forests using visualisation, for example. By searching for the term ‘mangrove’ in the Scopus database, for instance, and visualising the results from the last 5 to 10 years, it might be possible to gain an idea of the various research subjects. In turn, this could potentially help in focusing the search on the specific research subject.

Using Google Scholar can also help to contextualise the subject. For example, the series of terms ‘mangrove flooding hydrology data model’ results in more than 12,000 hits in Google Scholar, and quickly scanning the titles provides an idea of the potential relevance.

‘Alongside teaching our students how to search effectively, we also teach them how to properly record their collected data, so that others can use them in the future. Lab data is added to the 4TU data repository with a crosslink to the textual repository. It is a prerequisite that you properly and systemically store your data, including an interpretation and information about the measurement equipment that was used, and so forth. This allows other researchers to navigate their way around the many gigabytes of data, and avoids the need to reinvent the wheel’.

More information:

Contact Henk Jan Verhagen:
Contact TU Delft Library – Dirk Jan Ligtenbelt:

More about coastal protection and hydraulic engineering:

TU Delft Library