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The IJsselmeer is a former sea arm in the Netherlands, separated from the sea in 1932 by a 32 km long dam, the Afsluitdijk. Along the northeast coast of this lake the former saltmarsh have developed into valuable freshwater wetlands which help protecting the shore of the province of Friesland. In 2009, planning started of three so-called ‘sand engine experiments’ along this shore, meant to investigate whether a gradual supply of sand would enable the wetlands to follow a rise in lake level along with sea level rise. The implementation is governed by a coalition of regional and national actors, led by It Fryske Gea, a regional NGO for nature protection.

Building with Nature Design Traditional Design

Creating semi-natural floodplains on lake shores in front of existing dikes may help to dissipate wave energy, thus reducing wave attack on the dike. Additional positive effects are created by pioneer species colonising these new habitats and people recreating on the new beaches. Depending on the specific situation, sand is nourished a few hundred metres offshore and natural wave-related sediment transport gradually brings the sediment onshore. Furthermore Bio-engineers are stimulated to grow on the newly deposited sediments, thus preventing erosion.


To reduce the storm-related risk of flooding in Delta Lakes and Reservoirs, a traditional and proven solution is to raise the level of the (older) dikes. The strengthening of dikes usually involves raising as well as broadening the dike, which can have a profound impact on the landscape and the cultural values present. Despite the fact that dike strengthening enhances the safety level of a given area, the impacts on the landscape and user functions of such projects can trigger adverse reactions from local stakeholders. Moreover, in the case of the Frisian coast the ecologically valuable wetlands would not be enabled to follow the rising lake level and would sooner or later be lost.

    General Project Description


    Title: Soft sand engines Frisian IJsselmeer shore
    Location: Hindeloopen/Workum/Oudemirdum, Friesland, the Netherlands
    Dates: 2009, start of the project; 2011: Workumerwaard nourishment realised; 2012: Oudemirdum nourishment realised; decision to postpone the Hindeloopen nourishment.
    Companies: It Fryske Gea, Province of Fryslân, Wetterskip Fryslân, Municipalities, Directorate-General for Public Works and Water Management, Ministry of Infrastructure and the Environment, Building with Nature
    Costs: € 2.000.000
    Abstract: In front of the Frisian IJsselmeer coast three sand nourishment experiments are planned, meant to gradually nourish the coastal wetlands. These semi-natural flood plains should enhance flood safety, create new nature areas with conditions for pioneer species and provide the recreation sector with new opportunities.
    Topics: soft sand engines, bioengineers, vegetation, sand bar, sand nourishments, IJsselmeer coast, experiments


    The Delta Programme of the Netherlands Government is exploring a new national climate adaptation policy concerning flood protection and freshwater supply. This may include a gradual rise of the IJsselmeer lake level, along with the rising sealevel. At the same time, Atelier Fryslân (an initiative of the province to develop ideas to revitalise the Frisian landscape) is looking for possibilities to renew and revitalise the coastal landscape. The Frisian shore of the IJsselmeer is one of the focal points for renewal. These two initiatives opened a window of opportunity for innovations and experiments. In this context, the Building with Nature innovation programme was asked in 2009 by the national government (Ministry of Infrastructure and the Environment) to initiate a pilot study on this part of the Frisian coast.

    Even though the idea of systematic gradual lake level rise is under dispute now, water levels are most likely to fluctuate more in the future and regional parties became aware of the urge to prepare for this. They also realised they had to increase their knowledge about the lake and its shores. Based on a definition study to investigate possibilities, and on discussions between the Ministry and regional actors, the decision was taken to initiate three small-scale shore nourishment (‘sand engine’) experiments.

    View Pilot locations in a larger map

    Project Objectives

    It was decided to explore the application of sand engines at three locations (see figure above), each focusing on different spatial functions. The first pilot, at Workumerwaard, aimed at revitalizing a nature area by inducing new sedimentation. The second, at Hindeloopen, was meant to enhance recreational beaches. And the third, at Oudemirdumerklif, concerns an experimental shallow foreshore to absorb wave energy as an alternative to dike strengthening.

    Although the potential of creating semi-natural floodplains in the IJsselmeer is large, there is not much experience so far. Therefore, the general goal of the three experiments is to gain expertise in creating semi-natural floodplains along shallow lake shores and to fill knowledge gaps concerning sediment dynamics and the role of bioengineers in such low-dynamic areas. The experiments aim to find out whether sand nourishment is a good solution to create a more robust natural zone along the coast and to increase safety levels and natural and recreational values.
    The objective is to gain knowledge and experience on the following processes and issues:

    • The capacity of the system to transport sediment onshore.
    • The contribution of littoral zone vegetation to trap sediment trapping.
    • The adaptive capacity of the wetlands and shores
    • The extent to which eco-dynamic coastal development can contribute to the interests of various sectors (safety, nature and recreation)

    Proposed solution

    Concentrated offshore sand nourishments in a weakly dynamic environment like this will lead to a slow shoreward transport of part of the material, which gradually feeds sand to the shore. Pioneer vegetation (bioengineers) will settle on this newly deposited sediment, reduce erosion and trap new sediment, which helps to reduce the vulnerability of the nature areas outside the dike to flooding. This enables the establishment of a more robust natural system. As the vegetation will also function as a wave attenuator, this measure also contributes to coastal protection. Moreover, a coastline that is robust and diverse gains attractiveness to recreation.

    Governance strategies

    The initiators of the experiments were aware of the challenge of dealing with conflicting interests. Especially the conflict of interest between the Ministry (favouring the policy of the lake level following the rising sea level) and provincial parties (opposing this policy) required careful manoeuvring in the initiation phase of the project.
    Three levels of governance have to be taken into account when it comes to decision-making. First, there is the administrative arena, with the different levels of government – national, provincial and municipal. They all have authority and competences over the area and it takes time to align their different policies. Second, there are the experts from governmental and non-governmental organisations (NGO’s) and from private enterprises. They were brought together in a Community of Practice to discuss the options and to establish where more research was needed. Third, there is the local arena, with residents and other local stakeholders. In the case of Hindeloopen and Oudemirdumerklif this level proved to be very important to address.

    A number of strategies proved helpful to take due account of these three levels. The first one is to keep the options for compromise sufficiently open by avoiding too sharp definitions and too strict appointments too early in the process. By keeping the initial concept open and vague, potential partners had the opportunity to bring their own interests into the design and to avoid early clashes and entrenching about the end result. The second strategy was to produce a short movie (as shown below) with decision makers expressing the importance of a Building with Nature approach for Fryslân. The movie is in Dutch and has Dutch subtitles as well, but it gives an idea of the concept.

    Thirdly, actors in the area of the IJsselmeer were given a free choice to join the process. This is in contrast with most conventional projects, where actors use to be forced to participate as their values and interests are under pressure. Lastly, the pilots were framed as experiments, emphasizing that they were ‘allowed to fail’ without negative consequences for projects owners, experts, actors or stakeholders. This lowered the threshold to participate.


    At the start only the Building with Nature consortium had a budget available, but this was not sufficient to cover the costs of the experiments. Together with the regional project partners a project plan was formulated and applications for subsidy resulted in successful acquisition of a total budget of € 2 million. Financial contributions were received from Building with Nature (see EcoShape), a subsidy from the climate buffer program (see climate buffers) and subsidies from the Province and the Water Board. A project team and a steering committee with local (municipalities), regional (It Fryske Gea, Water Board, province) and national (Rijkswaterstaat, Building with Nature, consultants) representatives was formed to manage the project and monitor expenditures. This broad financing underlines the broad acceptance of the approach. As each financier had specific objectives and wishes, it was decided to consider implementation of sand engines at three different locations: Hindeloopen, Workumerwaard and Oudemirdumerklif. 

    Planning and Design


    Building with Nature was asked to initiate experiments on innovative solutions for the coast and to ease relations between parties with different interests.


    During the pre-feasibility study several workshops and meetings were held with different (governmental) parties involved, in order to affirm interests, to gain a clear picture of the experiments and to reach a statement of intent regarding the lake area. In this phase, negotiations were facilitated by a movie with decision makers expressing the importance of a building with nature approach for Fryslan. This movie showed support and provided informal legitimation from high-ranking authorities for the experiments. It was no longer questioned whether the project would be carried out, discussions rather shifted to how it would optimally succeed.


    In the feasibility phase two studies were conducted: pre-conditions of eco dynamic design (Building with Nature, 2011) and an ecological assessment (Deodatus & de Jong, 2010).

    Pre-conditions of eco dynamic design

    For the experiments to fit into the bio-physical system and to be viable, their ecodynamic designs must satisfy a number of conditions. We will describe several of these below.

    The aquatic vegetation cover was identified for several plant species (Top figure). The density of subaqueous plants is relatively low. Also, the few reed marshes present are less vital than before, which is due to a lack of water level variation, limited maintenance and erosion by currents and waves. Creation of a fluctuating water level and shallow foreshores would help to increase plant growth. Foreshores would provide opportunities to combine safety, recreation and ecological functions.

    In general, the morphology of the lake is in balance; only local fluctuations can be found. A morphological study near Hindeloopen, for instance, indicated a lack of shallow shores and foreshores. These local dynamics are influenced by wind waves the height of which depends on the fetch (i.e. the distance over which the wind hits open water), duration and speed of the wind. Middle figure shows the directionality of the prevailing wind conditions around the IJsselmeer in the form of wind roses.

    Wave dynamics and sediment transport were important inputs to the eco dynamic design. The sediment transport in the present situation was computed with the CROSMOR model in eleven regularly spaced cross sections. This yielded a first non-validated estimate of the sand transport along the coast. Due to the prevailing southwesterly winds (see middle figure) the transport diverges from the westernmost tip of the Frisian shoreline, as shown in bottom figure.

    Ecological assessment

    The entire zone outside the dikes is part of the Natura 2000 (EU policy for protection of specific species and their habitats) area ‘IJsselmeer’. The quality of nature in this region is somewhat on the decline and the aim of the experiment is to see if the sand engine can play a role in renewing and revitalising nature. Therefore, decisions to construct new infrastructure near or in the lake had to align with the obligation to maintain the ecological quality of the lake and its shores. In other words: prevent any harm or damage to species and their habitats. Interventions are subject to strict nature protection regulations and negative impacts on the ecosystem must be avoided, or compensated elsewhere if inevitable. Consequently eco-dynamic design pilots need to be assessed with regard to ecological and water quality effects. Objective of the ecological assessment is to map protected nature areas, to analyse effects and impacts of the envisaged intervention, and to review the findings in the light of the prevailing policies, regulations and legislation concerning nature.

    From this ecological assessment we concluded that the envisaged pilots would have a negligible effect on protected nature if the following conditions were met:

    1. Locations chosen such that Potamogeton and Chara globularis vegetation are affected minimally.
    2. Overgrowing of reed vegetation avoided or prevented.
    3. Minimal disruption of birds by adequate timing of construction activities (Workumerwaard: late October - early November; Hindeloopen: March - October; Oudemirdumerklif: June-July).
    4. Staying as far away as possible from rest places and breeding grounds (>300m) in order to prevent disruption during the breeding season.
    5. Avoid or move basaltic dams during construction works in order to prevent negative effects on the Cottus perifretum.
    6. No electric lights during night time, in order to avoid disruption of pond bats (Myotis dasycneme).
    7. Minimal effects on Cobitis taenia and Cottus perifretum.

    Permits and procedures

    Required permits are related to:

    • The Nature Conservation Act, which provides protection of this area,
    • Flora and Fauna Act, which regulates the protection of plant and animal species,
    • Water permit required when conducting activities near civil engineering structures (e.g. motorway, viaduct, tunnel, bridge, inland waterway, dike)


    Pilot Experiments


    Legal permits (nature protection law, municipal construction and water) for the Workumerwaard experiment were acquired without trouble. In the summer of 2011 the sand engine was constructed Sand Engine Workumerwaard.


    The initiative and planning of the second sand engine experiment in Hindeloopen proved more difficult. The reason why Hindeloopen was selected as a second location was the request of a camping owner, who wanted to improve the conditions of the beach. Another group of recreational entrepreneurs, however, sent a letter to the authorities requesting not to grant permits, as they did not want more sand to be supplied to this already shallow coast. After some discussion it was agreed that Building with Nature would address the problem of the shallow coast, instead of creating a new sand engine.

    Together with local stakeholders a more desired state was discussed. The objective was twofold: broadening the beach and deepening the foreshore. Deepening the foreshore, however, will intensify wave attack and thereby increase erosion. Therefore the solution had to involve three elements:

    • Protection of beach and foreshore;
    • At the inner side of the lagoon the fore shores are locally deepened;
    • Beach replenishment by sediment derived from the deepened area.

    Taking these requirements into account, a lagoon with several islands and floating barriers was proposed to protect the fore shores. The barriers function during storms to protect the beach from wave-induced erosion.

    Despite the potential of this design, there were several constraints to be considered. Currently, the access channel to the harbour of Hindeloopen already needs maintenance in order to keep it at sufficient depth. The lagoon could lead to increased siltation of the channel, which would be unacceptable. Also, mudflat formation and cyanobacteria blooming could potentially increase, making the area inaccessible for swimmers. As this could not be guaranteed not to occur, the experiment was cancelled. Instead, a study on the historic development of the coast and a modelling study will be carried out.

    The aim of the historical study of the coast between Molkwerum and Workum is to put past experiences into perspective and to clarify these from hydrodynamic and morphological system behaviour. This meant to be a basis for constructive discussions with the various regional actors involved in this pilot.

    The aim of the modelling study is to gain insight into several aspects of the recreational quality of the coast, e.g. channel sedimentation problems and their consequences for maintenance dredging and recreation, effects of fluctuating water levels on recreation, nature and dredging. This model will map the system as a whole in a quantitative manner, but only after measurements have been taken to supplement the currently available data. These measurement encompass depth soundings in coastal profiles 500 m into the lake and soil samples to determine the sediment composition. The model will be validated against these data and used to explore the consequences of future interventions.

    Oude Mirdummerklif

    In the Oude Mirdummerklif area, a study was carried out in order to find the best location for the pilot. Discussions with several actors were held to agree on the best place. The pilot aims to provide insight in physical processes and sediment pick-up, transport and deposition. The most important objective, though, is to gain knowledge about concentrated sand nourishments on this type of shores and their capability to attenuate waves. An impression of the design is shown in bottom figure.

    Residents near the Oude Mirdummerklif as well as kite surfers have been informed over the planning and start of the pilot project. During the design and the planning of the pilot objections and suggestions from the residents and the Dutch kite surfing association have been taken into account.

    In January 2013 construction was started on the peninsula In the Oude Mirdummerklif area. Due to bad weather conditions the work took until April 2013, when the peninsula was completed. Monitoring was started immediately by measuring the area, and now nature can start to do her work. Monitoring will continue until 2017. An information sign will be placed on the beach of Oude Mirdummer in July 2013, explaining the pilot and the overall project. The peninsula has been marked with buoys, to guaranty the safety of kite surfers who surf in the adjacent area. A situation sketch of the peninsula is shown in adjacent figure.


    Design, implementation and monitoring of the pilots required knowledge from morphologists, ecologists, monitoring experts, policy makers, governance experts, dredging contractors and others. As the pilots are also important to develop climate adaptation strategies for the IJsselmeer, there was interest from climate scientists, other governments (provinces, municipalities, water boards) and NGOs. The Workumerwaard pilot was realised in collaboration with the Coalition for Natural Climate Buffers, a group of Dutch NGOs working on the use of nature for climate adaptation.

    The exchange of knowledge between these experts is facilitated by a so-called Community of Practice (CoP), a platform to discuss innovative professional practices. Participants represent a wide range of disciplines, but they share the same practice, namely the development of new coastal management strategies. The CoP consists of twenty people from governments, NGOs and the private sector. It meets once every three months during a whole day.


    The first pilot to be realised was the one on the Workumerwaard, considered the easiest to implement because the Workumerwaard is a Natura 2000 area solely owned by It Fryske Gea and without other interests directly at stake. Indirectly, flood safety is an issue, as a loss of these wetlands would expose the dike behind it to more severe wave attack.


    After the protests of local entrepreneurs at Hindeloopen, expert studies were conducted, but these did not lead to easy innovative solutions at the scale of the Hindeloopen beach. A larger-scale analysis of sand transport along the Frisian coast would be a prerequisite for new strategies. Furthermore, the municipality expressed the wish to integrate potential experiments in a Masterplan process for the Hindeloopen and Workum coast. As this Masterplan is encompassing a larger area and goes beyond the means of Building with Nature, the programme management decided to cancel Hindeloopen experiment.

    Oude Mirdummerklif

    In Oudemirdumerklif the project design was refined in order to serve the several functions of the region and its stakeholders. Discussions with local actors have led to an agreement and permits have been acquired. Also, the design is well-received, as it takes the requirements and needs of the various stakeholders into account. Furthermore, in cooperation with the municipality a risk analysis was conducted. If the experiment fails and sediment is transported to other places than foreseen in the plans, it is agreed that the sediment will be removed. The construction of the pilot peninsula has been finished in April 2013. Due to an agreement within the steering committee, it has been made possible to monitor the pilot project up until 2017.

    Operation and Maintenance

    Current status of the experiments

    The Workumerwaard experiment is in place now and monitoring of ecological and morphological effects is taking place. Monitoring of the morphological developments is done by a network of fiberglass cables which measure bed level changes, hence erosion and deposition and, derived from that, sediment transport. To monitor morphological changes, above water yearly LIDAR-base bathymetric maps are made. By means of a jet ski equipped with an echo sounder the lake bed elevation is surveyed. In the area north of the sand bank a grid consisting of a 4 km long zigzagging fibre-optical cable has been constructed. Part of this grid is covered by the sand bank. Using laser technology it is possible to measure the temperature of each meter cable with a time interval of about two hours. Currents, wind and waves will gradually transport the sediment northwards covering parts of the grid. As sediment has a lower heat conductivity than water, the cable covered with sediment will have a different temperature signal than parts of the cable that are not covered at all. Based on this temperature gradient the location and thickness of the sediment layer can be calculated. For more details and figures, see Sand Engine Workummerwaard.

    The following points will have to be monitored during the pilot phase of the Oudemirdummerklif experiment:

    • Morphologic changes (sand transportation): by measuring the lake bottom after each storm period (as well as before and directly after the construction of the peninsula). This can be achieved using a grid, aerial photos and height measurements;
    • Grain size measurements of surface sediment;
    • Measurements during a storm to attain: currents velocity, currents direction and wave conditions;
    • Annual LiDAR flight measurements;
    • Monitor vegetation growth.

    For the Hinderloopen pilot project the initial design work was cancelled in December 2011 due to possible negative effects of the pilot work. In order to solve these problems a model study was requested, to gain insight in the coastal effects of a Building with Nature concept along the Molwerum-Workum coastal area.

    The execution of the model study has been approved to a combination of three consultant bureau’s which have presented a work plan on the 5th of May 2013. The work plan has been examined and adjusted by the waterschap Fryslân, municipality Súdwest Fryslân and the province. The work on the model study has been started in May 2013, and licenses have been applied for to conduct measurements in several protected nature areas, to provide data for the study. During the model study stakeholders will be kept involved in the process and results of the study. The model study will be completed in December 2013.

    Lessons Learned


    1. Use windows of opportunity. The plan to increase the lake water level in the IJsselmeer opened such a window. The situation forced coastal managers to rethink their practices which created opportunities for experimentation. It was fortunate that Atelier Fryslan and Building with Nature had prepared new potential strategies, which could now be introduced.
    2. Take time to reflect. The visit of the community of practice to the pilot site was useful. The CoP functions as a so called ´shadow network´, as its members are not under the scrutiny of their agencies or constituencies and are freer to develop innovative ideas.
    3. Select the right scale. Discussions in Hindeloopen were partly about the choice of scale. The selection of the beach as experiment location did not fit into the larger-scale Masterplan process of the municipality. The intention to negotiate with local stakeholders did not comply with the municipality’s ambition to plan for the whole coast.

    Physical and ecological processes

    1. Forecasting sediment transport, even in a low-dynamic system like this, is complex and requires specific hydro-morphological knowledge and tools.
    2. The hydrodynamics (currents, waves, water levels) in the IJsselmeer determine whether or not sand bars remain in place. At locations with less dynamics, sand nourishments will remain relatively stable and create opportunities for new habitats.
    3. The effects of interventions in the ecosystem and the ensuing changes in bio-physical structures are difficult to predict and come with high levels of uncertainty. Here, experiments are useful to gain understanding of and experience with the processes at different scale levels (local, regional, etc.).
    4. Currently, experiences where ecosystem development and socio-economic development go hand in hand are limited. Knowing better how to make these two complementary is an essential step towards ecodynamic development and design.

    Governance processes

    1. Manage expectations and acquire political support. In the case of the Workumerwaard sand engine experiment, the strategy for voicing and shaping expectations was to avoid unnecessarily precise definitions and representations of the end result, thus leaving room for negotiation and compromising between stakeholders. In the second experiment, this approach no longer worked, as expectations were based on what could be seen in the Workumerwaard. This led to protests and a change of course of the the Hindeloopen experiment.
    2. Political support is important for to get things going. For the BwN-pilots this was mobilised by producing a video in which influential governors expressed their support and expectations. The video was exploited wisely to mobilize others and its impact was striking. The visits of high-ranking officials to the Workumerwaard site also helped to create an image of powerful support.
    3. Experiments located in an environment in which the needs of different local actors can be met are likely to receive a broader support than mono-functional experiments.
    4. Carefully investigate ownership and user rights, stakes, positions and the history of the area. Not investing in scanning actual socio-economic characteristics, actor relations and conflicts in the past is certainly a pitfall to avoid.
    5. Visiting the project area with a community of practice (i.e. experts in the field of ecology, hydraulic engineering, dredging, governance, policy development, etc.) and local stakeholders during the planning phase is very useful. Discussions tend to be constructive and important and may result in several adjustments to design and process.


    1. Explicitly manage financial engineering. The funding of the experiments was a difficult and time-consuming negotiation process, through which the necessary budget had to be acquired from different sources.
    2. Objectives and wishes of financiers were carefully integrated in the design of the experiments. The advantage of this arrangement is that important stakeholders share a sense of ownership of the experiments and are closely involved the implementation.



    • ARCADIS 2010 Building with Nature pilot Workummerwaard. MIJ 3.2- Ecodynamic Design, Deliverable December 2010.
    • De Block, D., (2012) Pilot projects in ecosystem-based adaptation. 19th Annual Conference on Multi-Organisational Partnerships, Alliances and Networks, 2-4 July 2012, Wageningen University.
    • Building with Nature, (2011) Pilot eco-dynamiek Fryske kust (in Dutch).
    • Deodatus, F. de Jong, R., (2010) Voortoets ecodynamische kustontwikkeling Friese IJsselmeer. A&W rapport 1506. Altenburg & Wymenga ecologisch onderzoek, Feanwâlden. (in Dutch)
    • Lulofs, K.R.D., & Smit, M.R.H., (2012). ‘Show that it works’ – lessons learned from facilitating Building with Nature experiments. 19th Annual Conference on Multi-Organisational Partnerships, Alliances and Networks, 2-4 July 2012, Wageningen University.
    • Slobbe, E. van, Block, D. de, Lulofs, K. & Groot, A. (2012). The role of experimentation in governance. Lessons from a Building with Nature experiment. Water Governance(2), 1: pp. 56- 62
    • Van Slobbe E. Lulofs K. (2011) Implementing Building with Nature in Complex Governance Situations. Terra et Aqua 124: 16-24.

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