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7. Delta Management Plan

Within this chapter a short exploration of the research area is defined followed by a market research and financial feasibility plan, towards the usage of the engineering species Salix alba and Salix viminalis.

Exploring the research area

Around the world a change is occurring within our climate, called climate change. This change is affecting the weather patterns, the global temperature and the sea levels (IPCC, 2014).

This last one, sea level rise, is endangering around 50% of the world population (Creel, 2003) , because they live directly or on vicinity of a delta region.

Over the years, large hard engineering techniques, such as wave breakers, floodgates, seawalls and offshore breakwaters were created to counter/stall sea level rise and protect the hinterland from storm surges. Only thing is, these measurements were only a temporarily solution. Because of their hard structure, surface runoff into the natural soil is disrupted, and this runoff has caused flooding within the hinterland, and even in some cases to mud flows. These flows come to be, because for the hard engineering structures large pieces of forests are copped down or removed to make place for these structures. All the soil then which was stable, because it was kept in place by the root systems of these trees, were now loose and eventually washed away.

In recent years, people have become aware that only the usage of hard structures isn’t good enough and it isn’t green. Therefor allot of coastal redevelopment plans take building with nature into account. In this way, hard structures are built where is needs, and where it isn’t needed a more ecological approach is realized.

A good practical approach within the Netherlands is the room for the river project, where on 30 different sites, adjustments are made to improve the peak runoff of the river (Rijkswaterstaat, 2017). This is done to reduce the risk of flooding in the hinterland behind these dikes.

This building with nature approach is done worldwide, within the more tropical regions, the reforestation of mangrove forests is realized, since these forests form a primary storm surge barrier and a natural sediment capturer. This reforestation is done along the Vietnamize coast (Mazda, Y., Magi, M., Kogo, M. et al., 1997), were mangroves were cleared for agriculture and aquaculture (shrimp farming), but when these areas were depleted of their resources, they were in the first case not restored back to their former state, which left the hinterland open to storms and floods. Now these open areas are restored back to their former mangrove state, creating a barrier but also a new ecological living space of small aquatic life.

Within the more temperate regions of the world, like our environment within Europe, salt marshes tend to do the same as the mangrove forests do within the tropics. Only different plant species inhabit these salt/brackish areas.  Common plant species that inhabit these marshes are the Spartina spp. (aka cordgrass).

Moving a bit more upward, and towards the area where the research is at use, is the riparian system (rivers). Alongside these river banks, you can usually find the Salix spp. thriving. This specie can deal with flooding events, and is also quite capable into dealing with moderate salinity, which can intrude the river during upcoming tide.

Salix spp. in this research case Salix alba and Salix viminalis are fast growing species, with a strong root system to hold vast amounts of sediment. This is quite a useful feature; therefore Salix spp. is a recommended and used engineering species. But unfortunately, not much is known about the bio-mechanical capability of the Salix alba and Salix viminalis. And this bio-mechanical capability is of importance, because it’s necessary to know what these species can deal with in case of flooding and salinity to make optimal use of this engineering species. But then again, is there actually a global need for the reforestation of this engineering specie and where does it fit regarding building with nature?

The global relevance of willow usage

At first, the thoughts of bringing back the Salix spp. is an odd idea. But if you look more closely especially around agricultural grounds (fruit farmers) and river banks you can find these species.

First a short history about the human use of willows. The usage of willows predates from the stone-age (Ehrlich, 2015) Within the northern part of Europe and the Pacific northwest of America, willows represented the most used structural component for construction of shelters and fencing.

The flexible stems from the S. alba and S viminalis were also used as primary material to create baskets and the thicker stems were used for arrow shafts and fish traps. Within the Netherlands these stems were also used as a base within dike construction (ZBIGNIEW KLEDYNSKI, PIOTR KUZNIAR,, 2002).

Within North Amerika and Eurasia, the inhabitants used the willow bark as analgesics and for about two centuries, before a French pharmacist and Italian chemist produced the synthetic production of aspirin in 1829 (G.Mahdi, 2010), salicin extracted from Willow bark was commercially exploited.

In more recent years the global market has changed. The coming of synthetic produced aspirin, completely collapsed commerce exploitation of the willow bark. But I didn’t mean an end for the willow itself.  The range of application for willows is now more aimed at the minimization of negative impacts and outputs of the constructed environment on local ecosystems.

Within building with nature, Salix spp. is being used on a frequent base within environmental restoration work. It is a cost-effective material for stabilization and reclamation of disturbed landscapes, for both riparian and upland erosion control and biomass production.

Vision of building with nature with willows

For the vision, a practical application of the S alba and S viminalis is made for within the Dutch delta region. But due the temperate climate within the Netherlands, it is possible to use this example in foreign delta areas with a tempered climate as well.

Willow forests can function as a natural wave breaker and with that purpose they give a contribute towards the water safety of the hinterland (EcoShape, 2017).  Willows themselves cannot only protect the hinterland that’s why they should be used in a hybrid system. This system will consist of a dyke structure (a hard structure or an ecological rich dike), and in front of this dyke will be a zone where a willow forest can be grown. Because this willow forest is grown if font of the dyke structure, the height of this structure can be reduced.  In a recent research report, it states, that an average wave of a height of one meter, can be reduced to a height of 20 cm, while passing a full-grown willow forest (Mindert de Vries & Frank Dekker, 2009). In some areas, this reduction in wave height could mean that, instead of placing a rock covering, it could be exchanged for a more ecological covering, like grass with a basal layer of clay.

With creating these type of willow forests, you also create a recreational area and a biological living area for different species. These willow forests can also provide so called eco system services, these services are divided in four main categories: provisioning, regulating, habitat or supporting or cultural services (TEEB, 2017). TEEB (the Economics of Ecosystems and Biodiversity) is an international initiative to draw attention towards the benefits provided by biodiversity. TEEB presents an approach in which decision makers can recognize, demonstrate and, where appropriate, capture the values of ecosystems and biodiversity (: TEEB - The Economics of Ecosystems and Biodiversity (2013): Guidance Manual for TEEB County Studies, Version 1.0, 2013).

When creating these willow forests the following services will be of use:

 Provisioning:

o Purification of water: Willow forests can have a positive effect on the quality of water. This is because they take up nitrogen and phosphates out of the water, for their own growth. They also filter out so called heavy metals (lead, copper, tin, magnesium), and store them within their own biomass.

o Biomass: Within the upcoming bio based economy, renewable energy sources are getting more popular.  Willow forests can provide a steady stream of wood, for energy production within biomass fired electric power plants.

 Regulating:

o Erosion control: This is where arc GIS could be helpful (chapter 6 conclusion & recommendations page 24). To optimize the positioning of the willow forests so these can be placed in the most optimal location. This well-placed willow forests can reduce the height of waves and reduce the amount of erosion on the river banks, due to their root systems.

o Carbon Storage: Willows produce a great amount of biomass each year, due to their fast-growing properties. With this they capture a great amount of CO2.

o Local climate (micro climate): Both vegetation and water can influence the local temperature, humidity and wind speed in the local environment. Within the city, where the heat island effect normally takes place. Growing a willow forest could result in a 0.6-degree reduction per 10% of green (Deltares, RIVM, ECN, 2016).

 Habitat or supporting:

o Biodiversity: Willow forests create a diverse habitat for plants and animals to thrive in. For instance, different types of birds, and small mammals, but also different types of mosses.

 Cultural:

o Recreation: Willow forests contribute to a healthier living space, and created a nice location for recreation. Think about a good location to hike or bike. But also for bird spotters, due to the bio diversity these forests can have.

o Improve living conditions: Willow forests are a better adaptation towards coastal or river defense, then hard structures. Because these forests can reduce the wave height, the dike laying behand this forest could theoretically be reduced. Meaning that people living behand this dike, could enjoy more of the view behand the dike. Creating a better living condition.

o Educative function: These forests could be used to educate children and adults, in how these willow species protect the hinterland. They can be brought in contact with nature in their direct environment, this can act as a stimulation for children to have a better understanding of what nature does and can help the environment.

An added positive effect is, that the creation of these kind of willow forests to protect the hinterland, it also contributed towards the Natura 2000 network. This network I created to ensure core breeding and resting sites within Europe for rare and threatened species (EU, 2017). By creating these kind of areas, it might be possible to get funds from the European union to create them.

Building conditions

To make sure that the above stated positive influences these forests can give are achieved. There are a few conditions:

 First of all planting these forests in the right location is key. Next to their limited tolerance of salt and constant flooding (Chapter 4, results). These forests should only be grown where there is enough space. If this is not properly checked, these willow forests, can increase flow resistance and water levels (van Dènes Beyer, Claus van de Brink ...[et al.], Ministerie van Verkeer en Waterstaat, Rijkswaterstaat, Rijksinstituut voor Integraal Zoetwaterbeheer en Afvalwaterbehandeling (RWS, RIZA), red. I. van Splunder, 1997)

 Secondly the size of the forests matters. On average, a fully-grown forest should be around 100 meters long, and can reduce wave height up to 80%  (Mindert de Vries & Frank Dekker, 2009). The stem density should be around 4 stems per m2, increasing resistance.

Business model canvas related to creating a willow forest

The business model canvas is a strategic tool for new startups and developments. By using this model,

 the project of creating a hybrid dike, with willow protection will become more visual. The business model canvas consists of eight categories:

1. Value proposition: by constructing a hybrid dyke, a reduction in building costs is created. This is done in, due to the fact that the dyke itself will need to be less high, because of the protecting willow forest. But also, because the dyke itself doesn’t need to be covered in wave damping stone, so reducing costs and maintenance costs. Another plus side is that, because the dyke is lower, people can enjoy the view of the river. And the biomass off the willows will create in the long term a steady revenue, to maintain the dyke.

Next to a steady revenue from the biomass of the willows, also the creation of tourism to visit the areas biodiversity is another possibility of revenue.

2. Customer relations: This is important to be able to develop this kind of project. Because of the possibility of getting funds from the EU.

3. Channels: Communication with these kind of projects is important. Keeping track of opportunities within the government and with NGO’s and private parties to organize workshops and information evenings to discuss the opportunities these projects can make, and their revenue for the different parties involved.  

4. Revenue streams: Because this project is directly related to national safety, there is a national budget into creating these kinds of dykes. But because it is closely relatable to the Natura 2000 network, and will offer a resting place for rare and threatened birds and species, there is a big change it could get European funding. After the willows become mature, a steady flow of biomass is created each year. This biomass can be sold to power plants, that are converting to a more bio based economy fired fuel.

5. Key resources: To keep the area in the most ideal state, the following means are necessary:

Physical needs: Salix viminalis, Salix alba, selected planting area, recreation facilities

Intellectual needs: universities, researchers

Human needs: contactors, bushmen, investors, government, European union

6. Key activities: As stated within the previous paragraph, it’s important that the right location is selected to create a willow forest. Because otherwise it could have a negative influence then a positive one. To attract people towards the area after it is finished, promotion could be a possible resource to rely on. Also depending on where the forest is build, it could be promoted in on of the eight ‘inspiratie centrums’ that are run by the staatsbosbeheer (staatsbosbeheer, 2017), here people can take daily trips from and learn more about the flora and fauna within and around the area.

7. Partners: Because these projects are individually tailored to each selected location, one of the main partners will have to be a architect/construction company, which can calculate the height of de dike plus the costs that come with it. Another important partner is the government, in which funds can be asked of, to create these willow forests, and also the EU in which European funds can be asked to support building with nature projects. Also research institutes and universities are important, because their research and knowledge in natural defense and plant mechanics can help determine what species is best to use. And researchers and students can perform experiments within the area to improve future designs.

8. Cost structure: within the cost structure there are two visible costs:

Fixed costs:

Maintenance costs

Monitoring costs

Variable costs:


Upscaling natural defense

Policy and planning

To be able to start a project on this scale within the Netherlands, you need to get the project approved at government. This then needs to be put in place within spatial plan called a bestemmingsplan.  This is a planning policy that is used by Dutch municipalities, provinces and empire to describe what they are planning to do with spatial planning (ruimtelijkeplannen, 2017).

A possible re-construction of a current dyke or new dyke needs to pass a few policy’s/researches before they are approved by the government. These researches involve soil research, cultural research/historical values, nature and ecology. The results of these separate researches then presented and used to make a few options to improve the current dyke situation.  

When a plan is filed in the following policies and papers should be looked at:

 Government adjustment plan (Rijksinpassingsplan (RIP)): This plan is closely related to the bestemmingsplan.  The government adjustment plan is used in projects that are of national importance (RVO, 2017), like dyke enhancement or re-development. This all follows the spatial planning act, paragraph 2.6.3.

 Environmental impact report (Milieu Effect Rapport (MER)): This report brings in light the environmental impacts a project can have. This impact report is based on European guidelines (milieueffectrapportage, 2017). Within the Netherlands the MER is regulated by the environmental management act (Wet Milieubeheer ).

 Dike improvement plan: This plan consists of a report and several drawings per dyke segment. Within the report the short comings of the dyke are shown and what improvements need to be done to keep the hinterland secure.

Also, as of 1st of January 2017, new safety norms were instated for dykes, dams and dunes. The old safety norms were from the 60’s and were outdated to today’s weather patterns. These new guidelines for water security, are all stated within the 2017 deltaprograme.

DM conclusions and recommendations

Because we have become more aware that climate change induced sea level rise is going to influence out lives in the coming future, these building with nature solutions will become more common among our coastal defense implementations, instead of only hard structures.

Within the Netherlands there are already some project running into widening rivers and bringing them back into their meandering state. The implementation of these hybrid dikes, which are protected by a mature willow forest, will not only improve water safety for the hinterland. But also create a recreational area and a biological living area for different species.

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