Creating a saltmarsh between Holwerd & 't Schoor

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S H A P I N G A S A L T M A R S H

Creating a saltmarsh between Holwerd & 't Schoor

Wytze Kiers - S3469255 Supervisor: Jacco Kuper

Bachelor Spatial Planning & Design

June 2020

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Abstract

While the region of North-East Fryslân is in socio-economic decline, a group of people from the village Holwerd started an initiative called Holwerd aan Zee, with their goal to improve the socio-economic status of the village and add value to nearby nature. Part of the plan is the expansion of the saltmarsh east to the pier from which the ferry to Ameland departs, which would firstly become a purposeful place to deposit soil dredged from a fairway and secondly improve nature and tourism in the area. As a bonus, a saltmarsh could have a function as flood defence, decreasing costs for dike reinforcements. This thesis strives to find what experts think is the best way of enlarging the saltmarsh.

The experts’ opinions are gathered during semi-structured interviews. Results show that the project should not do disproportional damage to either the cultural or the natural landscape, besides the UNESCO heritage status of the region should be preserved. The best way of enlarging the saltmarsh would be with use of brushwood dams, which fits in the cultural landscape. Moreover, as the dams can be placed in a natural pattern, the influence on the natural landscape would be limited. There is however debate and uncertainty about the positive aspects of the saltmarsh concerning, among others, water safety, long term maintenance and the effects on nature in the area, moving the question from how to enlarge the saltmarsh, to whether the saltmarsh should be touched at all.

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Creating a saltmarsh between Holwerd & ‘t Schoor

Introduction

When travelling to the island of Ameland to enjoy the Wadden Sea area, one will pass a small village called Holwerd. With over half a million tourists visiting Ameland annually (Posperi, 2017), one could also expect the ferry port town of Holwerd to fare well. The contrary seems to be true as the residents of the village found it necessary to start Holwerd aan Zee initiative to increase the recreational and natural values of the village (Holwerd aan Zee, 2019). The worries of the residents seem to be right, as the number of inhabitants in the region has shrunk by 4,6% between 2002 and 2018. From 2005 onwards the region has only had negative population growth numbers (CBS, 2020). Residents report houses had turned unsellable, there is a job shortage and a retrenchment of liveability, care and wellbeing (Holwerd aan Zee, 2019).

The Holwerd aan Zee vision was to create a tidal lake next to the village, with an open connection to the Wadden Sea through a channel next to the ferry pier. The area around the lake would be converted from agricultural land to nature. Since its start around 2010, the initiative has gained a lot of significance and has developed from a wild dream into a project with involvement of various stakeholders, including the province and several nature conservation foundations. The plan has also grown, it is no longer only about a lake which connects the village directly to the Wadden Sea. One of the ambitions Holwerd aan Zee has added to their plan is to expand the saltmarsh on the seaside of the dike, between the pier and “T Schoor” (Figure 1). According to Jan Zijlstra, spokesperson of the initiative, the expansion of the saltmarsh would add value to the ecological side of the project, in the sense that a saltmarsh is a habitat for, among others, birds and fish. The saltmarsh could also serve as a purposeful place to deposit the dredged mud from the fairway to the inland lake.

Furthermore, Van Loon-Steensma (2015) describes how the expansion of the saltmarsh could adapt the flood defences, as a saltmarsh can slow down waves during storms, possibly getting rid of the necessity to heighten dikes.

The issue

At the moment, the saltmarsh is growing naturally. The natural growth comes very slowly and needs to be accelerated if the project is be completed within a reasonable timeframe. Since the Wadden Sea area is part of the UNESCO world heritage program, the natural values of the area should be preserved when interfering in the natural process. Van Loon-Steensma (2015) described how experts on flood defence are sceptical on the influence of the saltmarsh on the existing dike as they express their thoughts on how the saltmarsh might have an negative impact on the necessary maintenance of the dike.

The goal of this research is to explore in what way experts think the saltmarsh between the ferry pier and “t’ Schoor” can be expanded on a quicker pace without losing the natural values of the area and in such a way that the current flood defence is not affected in a negative way. This results in the following research question:

How do experts think the growth of the saltmarsh between the ferry pier and “T’ Schoor” be accelerated without losing the natural values of the Wadden Sea or affecting the existing flood defence in a negative way?

In the following section, history and context on saltmarshes along the Dutch Wadden Sea coast will be provided briefly, together with a theoretical framework. Next, the methodology will be discussed followed by the results. Finally, the results will be discussed and the research question will be answered in the conclusion.

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Theoretical framework

History of saltmarshes in the Wadden Sea

The famous saying that “God created the world, but the Dutch created the Netherlands” is also true for the Netherlands’ northern provinces. Since the 17^th century, farmers along the Wadden Sea coast have stimulated the sedimentation of clay along the coast by digging ditches. Resulting, saltmarshes appeared with an artificial, straight channelled drainage system. Until the 20^th century this “farmers method” of digging drainage channels was used with success. Due to property issues and economic circumstances, the reclamation of land almost stopped around 1925. Instead parts of the saltmarshes eroded, possibly leading to water safety problems. To prevent the saltmarshes from eroding too much, the Dutch government stepped in and restarted the reclamation program with another, German method. Introduced was the Sleeswijk-Holstein-method, a more complex system of settling fields, surrounded by brushwood dams and ditches. With the brushwood dams diminishing waves and currents, more sediments could sink to the bottom. In the 1990s this system of land reclamation changed into a system of maintenance and preservation, focussing on maintaining the existing saltmarshes, expanding the saltmarshes in a natural way and improving the natural vegetation from the first pioneer zone to the established saltmarsh vegetation (Dijkema et al., 2011).

As the saltmarshes lie in the Wadden Sea area, they are part of the largest system of intertidal sand and mudflats in the world, which is considered one of the most important areas for migratory birds (UNESCO, 2014). With such a unique area comes a plethora of conservation directives and agreements.

Starting in the 1970s with the incorporation of the area as Waterfowl Habitat into the Convention on Wetlands of International Importance. Besides, there are various European Union directives, like the Wild Birds Directive and the Habitats Directive, which in the Netherlands have resulted in the Wadden Sea being part of the Nature Conservation Act as a Natura 2000 area.

Furthermore, since 2009 the area has been declared a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). This means that every change made in the coastal zone is bound by strict rules (van Loon-Steensma, 2015). To cover all directives, the Dutch, Germans and Danish have set up the Trilateral Wadden Sea Cooperation as a way of having a combined strategy concerning the conservation of the area.

Regarding saltmarshes, the countries agreed to let the saltmarshes grow naturally and maintain them with as little human interference as possible, therefore letting nature be nature (CWSS, 2010).

Saltmarsh growth

Saltmarshes generally develop in the upper intertidal zones with limited wave action so that sediment can settle and accumulate (figure 2). Once the upper part of the sediments is no longer submerged with each tide, vegetation starts to grow. Once these salt-marsh plants are established, they trap sediments and therefore accelerate the accretion process (figure 3)(Allen, 2000). This natural process can be and has been accelerated by human interference (figure 4). With the limited human interference of today, monitoring reveals that the saltmarshes along the coast of Fryslân had an accretion rate of 1.5 cm per year between 1992 and 2009, which is outstandingly high. This might be a result of rising mean sea levels, as saltmarshes are well capable of following changing sea levels and adjust themselves accordingly. For growth, the pioneer zone adjacent to the sea needs additional protection because its vulnerability to erosion. To protect these pioneer zones, brushwood dams are

Figure 2: Natural saltmarsh growth without vegetation

Figure 3: Natural saltmarsh growth with vegetation

Figure 4: Saltmarsh growth with brushwood dams

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used (Dijkema et al., 2011). The question remains whether and/or how the traditional process with sedimentation fields can be accelerated even more without ignoring conservation policies to have the saltmarsh at Holwerd present as soon as possible.

Building with nature

The use of the natural sedimentation in combination with man-made brushwood dams can be conceptualised as building with nature. According to the concept of building with nature, society, engineering and nature work together to achieve goals (Slobbe et al., 2013). For successful building with nature, the system in which is built must be understood. Human change tends to focus on rapidly changing variables, but if a slow changing system variable or environmental condition is overlooked, rapid changes might throw the natural system into crisis (Holling, 1998). To prevent a crisis, a system can be “read” with the use of three elements (Slobbe et al., 2013). Starting with resilience, which is measured by the amount of change a system like the Wadden Sea can handle before its processes and structures change (Gunderson and Holling, 2001). The second element is social learning. As society needs to learn that due to uncertainties in dynamic systems, a straightforward uniform solution is no longer feasible (Funtowicz et al., 1998) and that learning from past events is necessary to adapt project strategies accordingly (Slobbe et al., 2013). The last element is the ecosystem services, especially the capability to use the functions of the ecosystem to serve the wishes of the people (Costanza et al., 1997). The use of brushwood dams might work in terms of building with nature, as long as the dynamic Wadden Sea system at the Holwerd coast is resilient to the changes made by the placement of the poles. Besides, stakeholders should understand that what works in other places along the coast is not sure to work here as well, only a prediction can be made based on past experiences. Finally, the natural sedimentation ‘service’ in the area must be understood to have the most saltmarsh growth, with the least impact on the environment.

Human interference in the Wadden Sea

Since its creation by nature 7,500 years ago, humans have left the Wadden Sea, spanning from the Netherlands to Denmark, untouched for about 5,000 years. About 2,500 years ago, permanent settlers began to change the landscape to protect themselves from the influence of the sea, separating the land from the sea and thereby starting the human dominance in the Wadden Sea ecosystem (Lotze et a., 2005). Over time, the Wadden Sea region has seen a lot of change, both natural and with human interference. The two major impacts of human interference in the Wadden Sea region are extinction and severe decline of species due to overexploitation and habitat change, with changes along the coastline as a prime example of the latter (Lotze et al., 2005). There has been a reduction of saltmarshes and mud flats from 33% in the Middle Ages to 2% today, a major change in habitat leading to a decline in species of coastal birds, which were unable to adapt to new sources of food.

Species that managed to adapt have flourished and increased in numbers (Reise et al. 1989; Lotze 2005). Human influence in the Wadden Sea ecosystem, made some species go extinct and enabled others to grow. According to Eriksson et al. (2010), even local hydraulic engineering can cause habitat destruction in large areas. Such acts, like the creation of a saltmarsh, change the hydrodynamic conditions and increase suspended sediment concentrations. For example, the supply of organic material from the North Sea to the Wadden Sea was one third of the locally produced primary production in the 1930’s, indicating that before the start of reclamation in 1932, the system had plenty internal regulation of pelagic and benthic production by seagrass meadows and blue mussel beds and low impact of imported nutrients from external sources. From the 1970’s onwards the amount of nutrients that are imported from the North Sea have increased, showing that the human-driven changes in the Wadden Sea have made the coastal system increasingly governed by external processes. Overall, the Wadden Sea has changed to a system dominated by sediment destabilisation, which is partly a consequence of human interference. It might be hard to restore the degraded habitats

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due to this interference as the system appears to be non-linear, meaning that when human interference in limited, nature will not automatically restore itself (Eriksson, 2010).

To preserve the natural habitats, the European Union has published the Habitats directive in 1992.

The goal of the directive is to preserve certain habitats that are described as different types in the directive. By enlarging a saltmarsh, the former habitat might be lost. Sites that are part of the habitat’s directive must be conserved, meaning that the natural habitats in those places must be maintained of restored. As part of the habitat’s directive, a coherent natural network of areas of conservation are set up under the Natura 2000 title, of which the Wadden Sea is one (EEC, 1992). This means that in the Wadden Sea region, the landscape should be preserved to remain the habitat that it is today, or it should be improved in that respect. Changes are allowed, but, for example, deterioration or destruction of breeding sites or resting places is prohibited if a protected is species breeding or resting in that area (EEC, 1992). Furthermore, in the so called Birds Directive, EU members agree to maintain populations of wild birds in Europe, therefore habitats for birds should be partially protected and marked as Natura 2000 area. Bird habitats should be conserved and, if destroyed, re-established.

Moreover, biotopes should be created (EC, 2009). Both directives state that changes conflicting with these directives are allowed in the interest of public health and safety, air safety, to prevent serious damage to crops, livestock, forests, fisheries and water or for the protection of flora and fauna (EEG, 1992 & EC, 2009).

Two landscapes

The natural landscape of the Wadden Sea region should, as it is a Natura 2000 site, be protected and preserved for the species living in it. It should, however, not be forgotten that one of those species is the human. As humans have been interfering in the Wadden Sea landscape for centuries to make it liveable, one could argue that currently two conceptual landscapes are present side by side, namely the natural and the cultural landscape. The natural landscape represents the habitat for animals, while the cultural landscape represents the visible influence people had on the landscape and the way in which the inhabitants of the Wadden Sea region feel connected to it (Walsh, C., 2018). It is important that changes to both the natural as well as the cultural landscape are considered well when changes are made to Wadden Sea landscape.

Methodology

The heart of the empirical research will consist of interviews with experts who have knowledge about the different aspects of the research. Besides interviews, observations have been made in the research area, as well as a larger saltmarsh under similar conditions, to analyse the differences. The different parts of the research will be explained more detailed below.

Interviews

As the research question concerns the vision of experts, experts must be interviewed. Interviews will provide a better opportunity for experts to share their knowledge compared to, for example, surveys, as the interviews will be semi-structured and therefore be open to additions by the interviewees and probing. To gain a more complete insight in the situation, experts from different disciplines will be interviewed. The experts interviewed come from Rijkswaterstaat, IMARES, It Fryske Gea, CWSS and Wetterskip Fryslân, further explanation can be found in appendix 1. Within each group multiple experts are to be interviewed, enabling the analysis of different opinions on the same issue and to have a back-up in case one of the two interviews fails to be completed. Besides the experts, an interview with a spokesperson from the Holwerd aan Zee initiative was conducted. This took place before the expert interviews, to gain better insights in their wishes and motives.

All interviews will consist of general questions and specific questions, meaning that a number of general questions about the Holwerd case will be asked to all experts to find differences in their

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opinions and that there will be specific questions based on the different expertise of the experts. The interview guides can be found in appendix 2. The transcribed interviews will be analysed using inductive coding to organise the data. In that way, the important parts of the interviews can be used in such a way that statements from different interviews can be compared more easily as they share the same code. It is not known before the interview what knowledge the respondent will share, therefore the coding will be inductive and based on the answers of the respondents. After the analysis, a code tree and a code book will be constructed which can be found in appendices 3 & 4.

Observation

As a last step in the research, on site observations will be made with the use of drone photographs.

This will be done at the research site, as well as the saltmarsh on the other side of the ferry pier. It is presumed that due to the close proximity of these sites, the conditions will be similar. Therefore the difference between the two sites might help understand how the growth saltmarsh in the research area can be stimulated to reach the same size as the saltmarsh on the other side of the ferry pier.

Photos will be taken from similar viewpoints of both saltmarshes, afterwards they will be put side to side for comparison. The locations and viewing angles of the photos, as well as the photos themselves can be found in appendix 5.

Answering the research question

The research question concerns the vision of experts on the expansion of a saltmarsh, therefore the expert interviews should provide a proper base for answering the research question. Besides, the theoretical framework and observations will provide some additional context to the knowledge gained in the expert interviews. Eventually, the combination of research approaches should provide a complete overview of what the experts consider the best answers to the research question and sub questions. The interviews will provide the opinions and experiences from experts on saltmarsh growth, while the observations will provide insights in the current state of the situation compared to a saltmarsh which has been enlarged. Using this multitude of methods, it is strived for to analyse the research problem from different angles and with more means than the opinions of the respondents, leading to more solid, objective conclusions.

To provide a visual representation for the research, a conceptual model is provided based on the concepts found in literature (figure 5). The conceptual model can be explained as follows: There is a wish for saltmarsh expansion, hence that is the outcome of the conceptual model. At the moment there is natural saltmarsh growth, but as this natural growth is insufficient to achieve the projects goal of having a saltmarsh between Holwerd and

‘t Schoor, a way should be found to accelerate this expansion. This can be done by stimulating natural growth and thus build with nature to make the saltmarsh grow faster. Another way could be by creating land artificially by moving mud from elsewhere to the saltmarsh. A combination of the tactics could also be possible, but any solution should work within the acceptable limits of influence on the natural and cultural landscape in the Wadden Sea area. Besides, the solution should not influence the current flood defences in a negative way.

Figure 3: Conceptual model

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Reliability & Validity

The experts approached for the interviews are deemed expert in the field by their organisation, with some of them having the research site as their job site. It will therefore be assumed that the knowledge the experts have on saltmarsh enlargement is valid and verifiable when compared to each other. To increase the reliability of the given answers by the experts, their anonymity will be guaranteed. As most of the respondents know each other from working together in the field, anonymity will give them more freedom of speech, even if their answers are not popular by their colleagues. The data from the interviews are therefore reckoned reliable and trustworthy. The observations will all be done under the same conditions and focussed on similar aspects, therefore the observations will also be seen as reliable and valid.

Hypotheses

The expected outcome of this research is not so much about finding a solution as it is about figuring out the best strategy to move on with the saltmarsh. Based on the theoretical framework, the hypothesis is that the natural growth of the saltmarsh could best be stimulated with for example the traditional Sleeswijk-Holstein-Method, using brushwood dams and ditches. As this method could be considered traditional to the area, it seems like this is one of the few options available considering the nature conservation policies. Another option could be that the nature conservation policies do not allow for any interference, in that case the saltmarsh expansion would be relying fully on the natural growth.

Results

The saltmarsh growth acceleration process

A saltmarsh can create itself. Under the right circumstances, the sediment in the water of the Wadden Sea could sink to the bottom and then a saltmarsh can arise after continuous deposition of sediment.

At the mainland Wadden Sea coast, of which the Holwerd saltmarsh is a part, this is not the case.

Due to the existing currents, there is too much movement in the sea for the sediment to sink and accrete. For a saltmarsh to grow at the east side of the pier at Holwerd, lee must be created in the water to enable sediment accretion and to maintain the saltmarsh. As expert 3 mentioned:

“You should find a way to secure the soil in one way or another to prevent it from drifting away towards Groningen during the first change in tides.”

Lee can be created in different ways, moles and brushwood dams are mentioned by the experts.

Moles would be running parallel to the ferry pier, to block the east-west current. Currently, the ferry pier is acting as a mole for the eastern saltmarsh. The presence of the pier provides enough lee for the saltmarsh to be maintained. Brushwood dams are

known as the traditional way in which land was reclaimed in this area. Therefore, the experts overall agree that in the Holwerd scenario, brushwood dams are the most suitable for the job and fit best in the cultural landscape.

Traditionally, the brushwood dams were placed in squares, creating so called, “bezinkvelden”. These square patterns are still visible in the landscape. One of the experts mentioned that to harmonise better with the natural landscape, other patterns can be used for placing the brushwood dams. This can result in a landscape with less straight lines, and more natural shapes. Expert 1 explains:

Figure 4: Brushwood dam (Van Loon- Steensma et al., 2012)

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“Often, we end up with brushwood dams as the best practise, but we do like to experiment with it and give it some more shapes, instead of square fields. You could also let the creek formation happen more naturally, to make it a bit more meandering instead of straight lines.”

When considering ways of saltmarsh creation, multiple experts expressed the importance of working with nature. With the use of brushwood dams, the natural sedimentation processes are stimulated by the created lee, resulting in a cooperation between human actions and natural processes. The process can be kickstarted by deposition of local material into the area, but this can only be done at the start of the project. Once vegetation starts to grow on the saltmarsh, spraying mud on top of it can be harmful for the pioneer vegetation. Besides, as soon as vegetation arises on the saltmarsh, the growth is accelerated as the sediments are grabbed by the vegetation.

Even though the experts individually agreed that brushwood dams would be best practise, one expert noted that the use of brushwood dams was stopped a couple years ago. As he explained, the ferry pier provides enough lee for the saltmarsh on the east side to stay like it is, so the efforts of maintaining the brushwood dams were unnecessary. The dams are still visible in the area, but as they are no longer filled with brushwood they have no function anymore.

Necessary changes to the area to enlarge the saltmarsh Away to the east from the pier, there is not

enough lee. In the current situation, the ferry pier provides enough lee for the saltmarsh to maintain itself. However, after the creation of the channel to the tidal lake (figure 7) action will be needed to maintain and expand the saltmarsh. As described above, this could either be done by moles or brushwood dams. When enough lee is provided, the eastern saltmarsh will expand through natural sedimentation processes, like expert 4 explains:

“The further you get away from the pier, the less lee there is so if you want to go east, to Ternaard, you should do something with brushwood dams to create lee for sediment to settle and can for pioneer vegetation to grow.”

Furthermore, to speed up the growth process, ditches should be dug in addition to the creation of lee, as better drainage accelerates the growth of the saltmarsh. The same conclusion can be found based on observation. When looking at figures 8 and 9, the difference between the two saltmarshes is clear. The western saltmarsh shows a system of straight ditches, a result from the land

reclamation works. The eastern saltmarsh does not have these straight ditches, instead the

landscape seems to be more naturally shaped. While the western saltmarsh has artificial drainage, the eastern saltmarsh relies on natural creek formation.

Differences can also be seen at the edge of the saltmarshes,. Again, on the western side (figure 10) the land reclamation fields are visible in the landscape. On the eastern side (figure 11) the dams are visible, but do not play a role in the existence of the saltmarsh. Also, it can also be seen that the eastern saltmarsh retracts landwards as it gets further from the pier. To sustain a saltmarsh width like the western saltmarsh along the coast, according to the experts, brushwood dams can be used on the whole trajectory as is visible at the western side.

Figure 5: Channel cutting through the saltmarsh

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The effect on nature & the heritage status

As the Wadden Sea region is a dynamic area, the effects on nature of any project in the area are unknown and can only be told with certainty afterwards. Experts did have some expectations on what kind of effects the creation of the saltmarsh could have on the nature in the area. First, with the creation of new saltmarshes and therefore new pioneer zones, pioneer vegetation emerges. This would contribute to the biodiversity in the area, mainly because pioneer vegetation contains more species than saltmarsh vegetation on an established saltmarsh. Secondly, the saltmarsh could be a habitat for birds. Especially when large parts of the marsh do not flood every tide, they could become rest spots for birds during high tide. Expert 4 explains:

“I think that saltmarsh could work well as a high tide rest place for birds. As soon as the tide drops, the birds forage on the sandbanks, but during high tide they search for places to rest and I am noticing an increasing amount of pressure on the Wadden Sea coast. (…) Tourists travelling along the coastline have a disturbing effect on birds and if you can create a quiet spot for resting birds, that could be positive compensation.”

Experts did mention that the increase in biodiversity due to pioneer vegetation only counts in the pioneer state of the saltmarsh, as there already are plenty established saltmarshes to which the later vegetation stadia would not contribute much. Besides, when the saltmarsh would be created it would replace what nature had put there, in this case mud. In other words, where new nature is created, existing nature is deteriorated. As mentioned by expert 1,

“Just because it’s under water, does not mean it’s not important”.

Figure 87: Western side of the Pier Figure 9: Easter side of the Pier

Figure 6: Western side of the Pier Figure 11: Eastern side of the Pier

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In terms of the region’s heritage status, everything would depend on the outcomes of an environmental impact assessment and the verdict of the UNESCO world heritage centre regarding it.

Changes cannot be prohibited by UNESCO, but when the impact on the area is too large, the heritage status can be removed. For the Wadden Sea region, three characteristics are relevant, namely: the outstanding geomorphological geological processes, the ecological, biological processes and biodiversity and last the management requirements. If one of these characteristics is compromised by the project, the area risks losing the heritage status and therefore an important part of the regional branding.

The effect on water safety

Saltmarshes having a positive effect on water safety is accepted as almost certain by all experts. The necessary conditions that have to be met for the saltmarsh as well as the surrounding area to increase water safety, are however uncertain. The dynamics of the Wadden Sea and the fact that the dike is not the same everywhere make it difficult to precisely predict the effect of a saltmarsh on the interplay between sea and dike. It is likely that the saltmarsh has a positive influence on water safety in the sense that the wave force will be decreased as the depth of the sea is decreased by the marsh, causing the waves to be smaller and therefore have less impact on the dike. For the waterboard, this could mean that reinforcement of the dike could be postponed, resulting in spending money at a later point or even spend less. There might also be a positive influence on the landscape; as the wave impact is expected to be lower with a saltmarsh, the dike could be coated with grass instead of tarmac.

Part of the money saved due to the saltmarsh might be reflected by extra maintenance. Organic material from the saltmarsh could, during a storm, be washed onto the dike. To maintain the dike this debris has to be cleared, leading to costs that are linked to a saltmarsh. Even though the saltmarsh related maintenance costs are not comparable to the financial burden of reinforcing the dikes, it might be of significance. When a dike is reinforced, 90% of the costs are covered by the state and 10% by the local waterboard, whereas the maintenance costs are covered by the waterboard only.

The time it would take for a saltmarsh to achieve the size at which it could have a notable effect on water safety is not certain, with guesses ranging from “10 years or even more” up to “25, 30 years?”.

For the waterboard, the cost savings can only be applied when there is certainty about the presence and stability of the saltmarsh. As the waterboard plans ahead for 50 years, certainty around the saltmarsh has to be given in 10 to 15 years. If there is no certainty about the existence, stability and functioning of the saltmarsh by then, it will not be taken into consideration in their plans.

Discussion

What started with the ambition of residents from the village of Holwerd to revitalize their hometown, has ended in a project larger than the village itself. Part of the project is the ambition to create a saltmarsh, firstly to be able to deposit mud residue from the tidal lake and secondly to create a touristic route between the villages of Holwerd and Ternaard. As a bonus the new saltmarsh would have a positive influence on nature, especially breeding birds. At the moment the saltmarsh east of the ferry pier is small and is wished to be enlarged, leading to the main question of this research:

How do experts think the growth of the saltmarsh between the ferry pier and “T’ Schoor” be accelerated without losing the natural values of the Wadden Sea or affecting the existing flood defence in a negative way?

It has become clear that lee must be created to secure sediments in order to create a saltmarsh, according to the experts the best practice is by placing brushwood dams. As expected based on the literature, brushwood dams are the most common way of creating saltmarshes in the area, as is

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confirmed by Dijkema et al. (2011). Therefore, brushwood dams will fit into the cultural landscape, the natural landscape comes with a different story. Naturally, hardly any saltmarsh growth would happen along the coast between Holwerd and Ternaard. This can only be done by human intervention, one might argue that every human influence disrupts the natural landscape. The challenge therefore seems to balance the cultural landscape with the natural landscape, which could for example be done by changing the pattern of the brushwood dams. When using more natural shapes in the placement of brushwood dams, an equilibrium could be found between the traditional practices found in the cultural landscape and the natural shapes of the natural landscape.

In terms of policy and the UNESCO heritage status, the enlargement of the saltmarsh is not expected to become an issue. Even though changes are made in the area, presumably deteriorating habitats of certain species and altering processes in the Wadden Sea landscape, similar projects have not found difficulty proceeding in the recent past. The project in this case might deteriorate parts of the landscape, but the saltmarsh will also have a positive impact. For example, the increase of biodiversity in the pioneer state of the marsh and the possibility for birds to rest on the marsh during high tides.

Resilience, social learning & ecosystem services

According to the experts and Dijkema et al. (2011), the use of brushwood dams is the most traditional way of creating a saltmarsh in the Dutch Wadden Sea. Based on past experience it can therefore be predicted that the system in the area near Holwerd will be resilient enough to enable the placement of brushwood dams without changing or losing critical processes. Also mentioned by the experts is the sufficiency in sedimentation. As the past has shown, with brushwood dams this ‘sedimentation service’ of the Wadden Sea system can be used to enlarge the saltmarsh near Holwerd as well. The processes in the Wadden Sea region, however, make every prediction uncertain. Although most of the experts mentioned how the Wadden Sea dynamics might not work the same at Holwerd as it does in other places, to some it should still be made clear that one cannot rely on a general, straightforward strategy. Even though past experience might indicate the strategy works, society, in this case the people aiming for brushwood dams as that is the traditional way, should learn that every project in a dynamic environment like the Wadden Sea calls for a tailor-made strategy for better handling of the area specific uncertainties. In terms of resilience and ecosystem services, the enlargement of the saltmarsh seems to be in line with the building with nature concept. However, in social learning some steps need to be taken to reach all involved stakeholders in order to fully utilise the building with nature concept.

The “if” question

What should be considered, however, is not the how but the if question. Multiple experts have shared their general considerations about the project and although there are positive aspects, there are also points of consideration.

First of all, the current situation is stable. At the moment, the saltmarsh maintains itself, in the lee of the ferry pier there is no further maintenance needed to preserve the marsh. Besides the fact that an expansion of the saltmarsh will not only bring costs in the implementation phase, the marsh will then have to be maintained bringing a periodically reappearing financial burden. The experts stress that a saltmarsh is not something to be bought once. Moreover, as the current saltmarsh is one of the most stable and natural on the Dutch mainland coast, it is seen as a sin to touch it and disrupt it. Only 5 years ago, the marsh has been transformed from a land reclamation work into a more natural saltmarsh (Staatsbosbeheer, 2014). Hence, there should be a good reason to alter such a stable marsh which has just been made into its current shape.

The experts state that whether or not the saltmarsh should be expanded must be considered thoroughly. Not only because the possible disruption of a stable system, but also because it is still

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unknown what the marsh would be replacing. Underwater nature is also valuable and should not be overlooked. this challenges the statement of the Holwerd aan Zee initiative that the saltmarsh will be good for the nature in the area. Additionally, one expert pointed out that the additional saltmarsh area could serve as a valuable resting place for birds, this function might however be affected when tourism is introduced. Human activity in the habitat of birds is likely to disturb the birds, losing the function of resting spot.(Murchison et al., 2016). It should therefore be considered that the saltmarsh is probably not able to serve a role in tourism, while being a proper bird habitat at the same time.

The positive effects of a saltmarsh on a flood defence system are well grounded. In the case of Holwerd, this could also add positive effects with the enlargement of the saltmarsh. The cost saving effect remains uncertain. The waterboard needs certainty about the shape, size and stability of the marsh as a condition to take it into account when designing for dike reinforcements. The timeframe in which the waterboard needs this certainty seems to be as long or shorter than the time needed to create a substantially sized and stable saltmarsh. Therefore it cannot be taken for granted that the enlargement of the marsh will result in cost savings in terms of flood defence, nor that it will result in a lower or greener design for a future dike. In any case, a saltmarsh in front of a dike can cause extra costs as debris from the saltmarsh can be sprayed onto the dike during storms, such debris must be cleared causing costs for the waterboard. As, in this case, the enlargement of the saltmarsh can cause additional costs with an uncertainty whether it will save costs in terms of water safety, this should not be a reason to proceed.

Furthermore, one of the main motives of the Holwerd aan Zee initiative for the expansion of the saltmarsh is as a solution to get rid of mud after dredging the fairway in their plan. The idea is that the mud taken from the fairway when dredging, could be deposited on the new saltmarsh. In this way, the growth of the marsh would be stimulated and there would be a purposeful place to deposit the mud.

Even though it is uncertain whether this deposited mud would settle in the right places, experts recon the deposition of mud can do no harm in the starting phase of the project. What should be noted is that this can only be done in early stages. As soon as vegetation rises on the saltmarsh, deposition of the dredged soil can do harm to the marsh, so, this is not the long-term solution as was intended by the Holwerd aan Zee initiative. Besides, the experts pointed out that the water in the Wadden Sea already contains such an amount of sediments, that adding extra soil to stimulate growth would be like a raindrop in the ocean.

For Holwerd the Holwerd aan Zee project is a one of a kind project, but across the Wadden Sea more similar project appeared in recent years. During the interviews, multiple experts have expressed worries regarding the amount of small projects in the Wadden Sea. All having a small impact on their own, but leading to significant changes in the region when combined. Especially in the Netherlands, the strategy of ‘let nature be nature’, as is agreed upon in the trilateral agreement (CWSS, 2010), seems to be interpreted broadly as seemingly unnecessary projects are not uncommon. It should be considered whether projects like Holwerd aan Zee without a necessity, like for example water safety or adaptation to sea level rise, should be desired. Creating “nature” by interfering with the natural processes of the Wadden Sea is expected to result in unstable nature, whereas leaving the processes to them self as much as possible will result in nature, even if this is not the nature we humans want.

Conclusion

As part of the Holwerd aan Zee project, there is the ambition to enlarge the saltmarsh to the east of the Pier with the ferry to Ameland. First of all to have a place to deposit the mud coming out of the heart of the Holwerd aan Zee project, the tidal lake. Secondly to have a touristic connection with the neighbouring village of Ternaard and add value to the nature in the area. As the best practice to enlarge the saltmarsh east of Holwerd must be found. This research has aimed at finding what is,

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according to experts, the best way to accelerate the growth of the saltmarsh, without losing the natural values of the Wadden Sea nor affecting the flood defences in a negative way.

In the Wadden Sea region, brushwood dams are determined the usual way of creating or enlarging a saltmarsh, for which this is expected to be the best practice for enlarging the Holwerd saltmarsh.

For a more natural marsh, the dams should not be placed in the traditional squares, but in more natural shapes as the shape does not affect the functioning of the dams, as long as enough lee is created for the sediments to settle. Once the saltmarsh would be enlarged, positive effects are expected for nature, especially birds looking for shelter during high tide, but also for biodiversity in the area. Besides, the saltmarsh is expected to have a positive effect on the flood defences once it reaches a substantial size and is stable.

Most positive effects of the enlargement of the saltmarsh are however overshadowed by uncertainty and compromises, leading to the question whether the stable saltmarsh in the current situation if worth altering. Examples are the uncertainty whether the saltmarsh will save money or increase costs concerning water safety, whether there will be enough resting space for birds when tourism is introduced or if the saltmarsh will become stable and will not disappear during a storm. The latter should be researched before any shovel is put into ground. Besides, an environmental impact assessment should be conducted to ensure the impact is not of such magnitude that the UNESCO heritage status might come in danger or that habitats are destroyed. Finally, this research has been limited by its theoretical approach. The optimal strategy for enlargement of the saltmarsh as derived from the experts’ opinions should be researched further with a geomorphological approach. Further reflections on this research can be found in appendix 6.

Concluding, for Holwerd the Holwerd aan Zee project is unique, but across the Wadden Sea more similar project have started to appear in recent years. The overall impact of these projects is considered significant on the Wadden Sea, leading to the question whether our desire to create nature in the Wadden Sea does not lead to working against the natural processes of the area. More research is therefore advised on the influence of small civilian initiated projects on the Wadden Sea region.

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References

Allen, J.R.L. (2000). Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe. Quat Sci Rev, 19(12), pp. 1155-1231.

CBS (2020). Bevolkingsontwikkeling; regio per maand. Retrieved on February 16, 2020 from https://opendata.cbs.nl/statline/#/CBS/nl/dataset/37230ned/table?ts=1581868982897 .

Common Wadden Sea Secretariat (CWSS) (2010). Wadden Sea Plan 2010. Willemshaven, Germany: Common Wadden Sea Secretariat (CWSS).

Constanza, R., Pérez-Maqueo, O., Martinez, M.L., Sutton, P., Anderson, S.J. & Mulder, K. (2008). The value of coastal wetlands for hurricane protection. Ambio, 37(4), pp. 241-248.

Dijkema, K.S., Duin, W.E. van, Dijkman, E.M., Nicolai, A., Jongerius, H., Keegstra, H., Egmond, L. van, Venema, H.J.

& Jongsma, J.J. (2011). Vijftig jaar monitoring en beheer van de Friese en Groninger kwelderwerken: 1960 – 2009. Den Burg: IMARES Wageningen UR, Leeuwarden: Rijkswaterstaat, Dienst Noord-Nederland en Waterdistrict Waddenzee & Beetsterzwaag: It Fryske Gea.

Eriksson, B.K., Hiede, T. van der, Koppel, J. van de, Piersma, T., Veer, H.W. van der & Olff, H. (2010). Major Changes in the Ecology of the Wadden Sea: Human Impacts, Ecosystem Engineering and Sediment Dynamics.

Ecosystems, 13, pp. 752-764.

Funtowicz, S., Ravetz, J. & O’Connor, M. (1998) Challenges in the use of science for sustainable development. Int.

J. Sustainable Developments, 1(1), pp. 99-107.

Gunderson, L.H. & Holling, C.S. (2002). Panarchy: understanding transformations in human and natural systems.

Island Press, Washinton, DC.

Holling, C.S. (1998). Adaptive environmental assessment and management. Environmental Pollution Series A, Ecological and Biological, 21(3), pp. 248.

Holwerd aan Zee (2013 – 2019). Over Holwerd aan Zee. Retrieved on February 16, 2020 from https://www.holwerdaanzee.nl/over-haz/project/. Holwerd: Holwerd aan Zee.

Kadaster (2020). BRT-Achtergrondkaart. [image] Available at: https://www.pdok.nl/introductie/- /article/basisregistratie-topografie-achtergrondkaarten-brt-a-

Loon-Steensma, J.M. van (2015). Salt marshes to adapt the flood defences along the Dutch Wadden Sea coast. Mitig Adapt Strateg Glob Change, 20, pp. 929–948.

Loon-Steensma, J.M. van , P.A. Slim, J. Vroom, J. Stapel en Oost, A.P. (2012). Een Dijk van een Kwelder.

Wageningen: Alterra.

Lotze, H.K., Reise, K., Worm, B., Beusekom, J. van, Bush, M., Ehlers, A., Heinrich, D., Hoffmann, R.C., Holm, P., Jensen, C., Knotterus, O.S., Langhanki, N., Prummel, W., Vollmer, M. & Wolff, W.J. (2005). Human transformations of the Wadden Sea ecosystem through time: a synthesis. Helgol Mar Res, 59, pp. 84-95.

Lotze, H.K. (2005). Radical changes in the Wadden Sea fauna and flora over the last 2,000 years. Helgol mar res, 53, pp. 71-83.

Murchison, C.R., Zharikov, Y. & Nol, E. (2016). Human activity and Habitat Characteristics Influence Shorebid Habitat Use and Behavior at a Vancouver Island Migratory Stopover Site. Environmental Management, 58, pp. 386- 398.

Prosperi, C. (2017). Meerjaren Marketing & Promotie Strategie VVV Ameland. Nes: VVV Ameland.

Reise, K., Herre, E. & Sturm, M. (1989). Historical changes in the benthos of the Wadden Sea around the island of Sylt in the North Sea. Helgol Meeresunters, 43, pp. 417–433.

Slobbe, E. van, Vriend, H.J. de, Aarninkhof, S., Lulofs, K., Vries, M. de & Dircke, P. (2013). Building with Nature: in search of resilient storm surge protection strategies. Nat Hazards, 66, pp. 1461-1480.

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Staatsbosbeheer (2014). Holwerd Buitendijks. [image] Available at:

https://www.google.nl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwj_ktbyuKTpAhWE2qQK HaF3DOwQFjAAegQIAhAB&url=https%3A%2F%2Fwww.staatsbosbeheer.nl%2F~%2Fmedia%2Fnoard- fryslan%2Fkwelder-holwerd.pdf%3Fla%3Dnl-nl&usg=AOvVaw0rnUFlfAsojhDHUYc6fw8A [Accessed: 8 May 2020].

The Council of the European Communities (EEC), (1992). Council directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and or wild fauna and flora. Brussels.

The European Parliament and the Council of the European Union (EC), (2009). Directive 2009/147/EC Of the European Parliamt and the Council of 30 November 2009 on the conservation of wild birds. Brussels.

UNESCO (2014). Decisions adopted by the world heritage committee at its 38^th session (Doha, 2014). WHC- 14/38.COM/16. Doha, Qatar: UNESCO.

Walsh, C. (2017). Metageographies of coastal management: Negotiating spaces of nature and culture at the Wadden Sea. Cultural geographies of coastal change, 50, pp. 177-185.

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Appendices

Appendix 1: Respondents

Holwerd aan Zee

- To gain better insights in the wishes and motives of the Holwerd Aan Zee initiative, a spokesperson will be interviewed. The spokesperson will not be regarded an expert but will probably already have a vision on how the saltmarsh should be shaped according to the initiative.

Experts on creating and maintaining saltmarshes

- Rijkswaterstaat, Rijkswaterstaat is the state’s tentacle in the Wadden Sea area. With the institution monitoring saltmarsh conditions and maintaining them, there will also be expertise on the topic within this organisation. Besides, as Rijkswaterstaat is the administrating party in the area, it is an important stakeholder in the execution of the project.

- IMARES, IMARES is a branch of the Wageningen University, conducting research on various aspects of the Wadden Sea area including saltmarshes.

Experts on nature conservation

- It Fryske Gea, It Fryske Gea is an organization which concerns itself with conservation of the Frisian landscape, including the Wadden Sea area. Besides, they are the keeper of most of the Frisian saltmarshes.

- Common Wadden Sea Secretariat (CWSS), the CWSS is an organisation linked to The Netherlands, Germany and Denmark. Its goal is to execute the strategy of the three countries in preserving the UNESCO world heritage site.

Experts on flood defence

- Wetterskip Fryslân, The Frisian waterboard is responsible for the Wadden sea dike in the province of Fryslân, and therefore also for whether or not adopting saltmarshes into their flood defence strategy. Besides, their sea dike lies at the same shore where the new saltmarsh would be created and as the saltmarsh might have influence on the dike, the Wetterskip Fryslân is also an important stakeholder.

Appendix 2: Interview guide

Introduction

- Who am I?

- What is my research about?

- Anonymity (respondents remain anonymous) & Recording General questions:

- Are you familiar with the Holwerd aan Zee project? (Make sure the interviewee understands the scenario).

- What ways to accelerate the growth of a saltmarsh do you know?

o Which of these ways would work in the Wadden sea?

- Of these methods, which would fit best in the Holwerd scenario to your opinion? why?

- To implement this method, what would have to be changed in the area? prima - What is your general opinion regarding the expansion of the saltmarsh? prima

o Is it feasible?

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 Costs?

 Long-term sustainability & sea level rise?

 Policies and laws?

o Effect on the area / nature / Heritage status?

o Effect on water safety & flood defences?

o How does the choice of strategy influence your opinion regarding the saltmarsh expansion? Would it be different is another strategy was chosen?

- Could there be external effects on nature and/or general landscape in the region due to saltmarsh expansion?

o Do you have examples of such external effects?

o Could the choice of strategy for saltmarsh expansion have any influence on these external effects? How?

Specific questions:

Holwerd aan Zee:

- What does your organisation want to do with the saltmarsh north-east of Holwerd?

- What do you want the saltmarsh to look like?

o Can you give an example of an existing saltmarsh?

- What time period is aimed for to finish the plans regarding the saltmarsh?

- What strategies for salt marsh expansion are considered?

Waterboards:

- How can a saltmarsh influence the sea dike when it is used as a flood barrier?

- Is there added maintenance for the waterboards due to the saltmarsh being there?

o What for?

- How does this affect your organisation?

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Appendix 3: Code Tree

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Appendix 4: Codebook

Code Meaning Example quote

General considerations General considerations

regarding the saltmarsh expansion

What is forgotten often in such projects, when you place dams you also have to maintain them.

Erosion The erosion of a saltmarsh If there is a channel from the Wadden system which grinds it away every storm, it is a pointless mission.

Let nature be

nature Letting nature manage itself as

much as possible That is what I’d say, let it be what it is.

Long term

maintenance Necessary maintenance to preserve the saltmarsh after it is completed

What is forgotten often in such projects, when you place dams you also have to maintain them.

Points of

consideration General point that should be

considered regarding the project Young saltmarshes with plenty vegetation have addition value, but they come at the cost of under water nature.

Project

timespan The necessary time to get from the current situation to a completed saltmarsh

What shall I say? 30 years? 25 years?

Saltmarsh

stability The stability of the saltmarsh over time in terms of size and strength

The dimensions must be right, the lee must be sufficient and the maintenance must be right.

Sea level rise The rise of the mean sea level Yes, because a saltmarsh can grow with the sea level over time.

Socio- Economic impact

The impact on the socio- economic status in the town of Holwerd and its surroundings

More attention to your area, tourism might increase, or foreign investments might increase.

Nature conservation The conservation of the nature

in the area What it is now will disappear,

which is a negative side.

Cultural

Landscape

Visual aspects of human

intervention in the landscape Sedimentation fields, basically the land reclamation works of the past, that is what they have always worked with.

Effect on heritage

status

The predicted effect of the project on the UNESCO heritage status of the region

if there is a big effect then the world heritage centre would put the area or part or part of the area in danger and there will be another evaluation and there is the risk that the area will then be taken out of the world heritage property.

Let nature be

nature Letting nature manage itself as

much as possible That is what I’d say, let it be what it is.

Natura2000 The policy regarding the EU birds

and habitat directives You should take a look at the targets of the Natura200 area, for example the conservation of saltmarshes.

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Natural

landscape Visual aspects of nature in the

landscape I think it is fantastic nature, but sand banks are also important for less visible species.

Nature

management The way in which nature is

managed and maintained The guiding principle for the trilateral cooperation, let nature be nature.

Negative

effect on nature

Negative effects of the project on

the nature in the area What it is now will disappear, which is a negative side.

Positive

effect on nature

Positive effects of the project on

the nature in the area They can store a lot of carbon.

Saltmarsh

creation The creation of a saltmarsh in

a location where there is none You should create lee in which the saltmarsh can be created.

Brushwood

dams Two rows of wooden poles with brushwood in between, acting as a dam

Well, the most traditional will be brushwood dams.

Building with

nature Using natural processes to

create something You should use the natural processes, when you go against them it will become difficult to construct a saltmarsh.

Double dikes Having a small dike seaward from the main dike to prevent the area in between from eroding

Well, I’ve heard for example of making these double dikes and in the middle of the two dikes allow for a saltmarsh to expand.

Influence on

growth speed The influence certain strategies of saltmarsh creation have on the speed at which the marsh grows

The more you drain, the faster vegetation will rise.

Lee creation The creation of lee in the water, to present erosion and support sedimentation

Because saltmarshes always form in the lee.

Necessary

changes Changes needed to create a

saltmarsh near Holwerd You should find a way to secure the soil, to prevent it from drifting to Groningen at the first tide.

Up silting Sedimentation of mud particles

resulting in a rising ground level At Holwerd it is the same story, there is plenty of up sitting around there.

Sediment

level The amount of sediment in the

water The research showed there is

already such an amount of sediment in the water that any addition does not really add up.

Slibmotor The deposition of sediment in such a way that it gets picked up by natural processes and

accelerates natural sedimentation

There they have deposited the slib from the harbour of Harlingen into a creek.

Soil deposit The deposition of soil to create

new land Well, I would not repeatably spray a layer of mud on a saltmarsh

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Stone dams Dams made out of stone to

create lee Place Moles.

Water Safety The prevention of unsafe

situations as a result of water and storms

A saltmarsh can reduce the wave and therefore the impact, meaning there is less wave impact on the dike.

Effect on

water safety The effect of a saltmarsh on

water safety Yes it is possible that there will be an effect on the coastel defences.

Negative

effects on finances

Saltmarshes leading to more

costs with regard to water safety When debris gets onto the dike, we will have to get rid of it which increases the costs.

Positive

effects on finances

Saltmarshes leading to less

costs with regard to water safety You could create a new design, through which you might be able to delay costs.

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Appendix 5: Aerial photography

Photo locations and views

Aalst, J.W. van, (2020). OpenTopo. [image] Available at: https://www.imergis.nl/htm/opentopo400.htm

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Appendix 6: Reflections

In this research a strategy was aimed to be found for the enlargement of a saltmarsh. To find this strategy, experts were interviewed who were presented by their organisations as experts on the topic, therefore the data gathered is seen as reliable and valid. The experts, however, also mentioned other stakeholders and specialists that were not interviewed. For a future research, the quality of the research might increase if such leads given by respondents are followed up. The research itself carried on at a steady pace, even during this extraordinary time of the covid-19 virus. As the interviews could be held by phone and were mostly planned before the pandemic, no harm was done to the time schedule. The fact that the interviews were conducted by phone might, however, have influenced that data slightly as face-to-face interaction was lacking. At last, it would have been good to have the aerial photographs during the interviews to have the experts shine a light on the differences between the two saltmarshes, but unfortunately this was not possible due to high wind velocities in the period before and during the interviews.

Creating a saltmarsh between Holwerd & 't Schoor

S H A P I N G A S A L T M A R S H