About
In short
Accelerated sea-level rise (SLR) seriously threatens coastal areas globally. Sand nourishments – the addition of sand to increase the beach volume – are potentially a key method to sustainably adapt to accelerated SLR and keep the low-lying hinterland protected against coastal flooding.
The SOURCE project will deliver the scientific knowledge, models and design tools to develop and evaluate nourishment strategies in a multi-stakeholder co-creation process. These carefully planned sand nourishments will create the required and desired resilient and dynamic multifunctional coastal landscapes of the future.
Illustration by: Joost Fluitsma
Problem analysis
The nearshore zone, in particular the beach-dune system, is important for flood risk management, acts as a reservoir for fresh water and holds high economic, recreational and natural values.
Coastal areas attract people to live, work and recreate. Coastal ecosystems are also home to a wide range of flora and fauna species that directly and indirectly contribute to important ecosystem services such as carbon dioxide absorption and dune development.
The inevitable effects of global climate change, accelerated sea-level rise (SLR) in particular, seriously threaten low-lying coastal areas. Without serious human interventions, SLR will increase coastal erosion, endangering beach-dune systems and putting coastal communities at risk.
At the same time, socio-economic developments, such as population growth, call for more space for recreation and increased fresh water supply. This puts even more pressure on the beach-dune area.
Additionally, natural coastal habitats are threatened to be lost or deteriorated in their quality by anthropogenic structures or actions, preventing the landward transgression of those habitats that would otherwise naturally occur in response to SLR; coastal squeeze.
Coastal sand nourishments – the addition of sand to increase the beach volume – are potentially a key method to sustainably adapt to accelerated SLR and keep the low-lying hinterland protected against coastal flooding.
Many challenges arise regarding large-scale nourishment strategy. Where should we construct the nourishments and where will the nourished sand go? What types of nourishments are most effective? What will be the long-term effects on the coastal ecosystem? Will dunes be able to grow with SLR to maintain their flood protection function? And what are the socio-economic impacts?
Aim & objectives
The main research question of the SOURCE project is:
How can we co-create multifunctional sand nourishment strategies for a resilient dynamic coast with high socio-economic and natural values?
Illustration by: Joost Fluitsma
We aim to develop the scientific knowledge, models and design tools to develop and evaluate nourishment strategies in a multi-stakeholder co-creation process. This will be accomplished by a combination of fundamental coastal ecosystem understanding, reliable predictive modeling of nourishment impacts, quantification of both the non-monetized and monetized social costs and benefits, and an integral design and evaluation process.
The following objectives address the overall research question and form the basis for the Work packages (WPs):
Societal impact
Accelerated sea-level rise (SLR) seriously threatens coastal areas globally. SLR will narrow the beach and cause increased erosion.
At the same time, continuous socio-economic developments such as urbanization cause increasing pressure on coastal land use. Without adaptation through coastline management a so-called coastal squeeze will occur with a narrowed beach and dune system.
This endangers these systems and puts coastal communities at risk of flooding. The coastal ecosystem’s response to SLR combined with human interventions will shape the future of our sandy coasts.
Coastal sand nourishments – the addition of sand to increase the beach volume – are potentially a key method to sustainably adapt to accelerated SLR and keep the low-lying hinterland protected against coastal flooding.
Carefully designed and planned sand nourishments now will create the required and desired resilient and dynamic multifunctional coastal landscapes of the future. Next to flood protection, such coasts offer high natural values with a large biodiversity, recreational functions as well as fresh water supply.
To achieve this, coastal managers, stakeholders, researchers and industry need to collaborate in close harmony.
This is expressed in the expected societal impact of the SOURCE project:
Co-created multifunctional sand nourishment strategies for a resilient dynamic Dutch coastal flood defense with high socio-economic and natural values.
This societal impact comprises three elements:
Paradigm-shift: coastal sand nourishments are not just valued as a means to hold the line, but also to create climate buffers that are multifunctional landscapes, supporting socio-economic and natural values; from dynamic preservation to dynamic development
Co-creation of multifunctional sand nourishment strategies in collaboration with coastal managers, stakeholders, researchers and industry
Resilient dynamic coastal landscapes, including their socio-economic and natural functions, through co-created sand nourishment strategies
Scientific impact
The scientific breakthroughs we hope to achieve within SOURCE are:
Quantification of coastal sediment pathways linking the scale of individual nourishments (1-10 km, 1-10 years) to the scale of a complete coastal system (10-500 km, 10-100 years)
Monitoring has shown that a long-term sand nourishment strategy increases the volume of sand within an entire coastal zone (Brand et al., 2022). Despite these observations, it is poorly understood how nourished sand finds its way through the coastal zone and therefore how design variables (e.g. size, placement location) affect sediment transport fluxes, grain-size distribution, morphological response and, ultimately, habitats outside of the direct placement area (De Schipper et al., 2020). This knowledge is key to deciding where, how much and how often to add increased volumes of sand to the Dutch coast to adapt to accelerating SLR, and to quantify the long-term cumulative effects of recurrent nourishments for the coastal ecosystem and other coastal functions.
This breakthrough will be realized by capitalizing on existing long-term (50+ years) datasets and satellite imagery of the Dutch coast, and collection of novel field data from the dedicated SOURCE Living Lab coastal nourishments.
Insight into long-term ecological effects of sand nourishments and methods to mitigate the negative impacts or even increase ecological values by smart coastal landscape design
Despite the adaptations of coastal species to a dynamic environment, recovery times of both community composition and ecosystem functioning after a major reset by coastal nourishments can be substantial, yet these are still poorly understood (Peterson et al., 2006). While it may seem reasonable to assume recovery after nourishment will follow similar trajectories as after severe storms, increases in nourishment volume and frequency in response to SLR will enhance dynamics and alter beach-use that may modify recovery speed (Witmer & Roelke, 2014). This could push trajectories into unexpected directions, because sediment composition and morphodynamics will change (Herman et al., 2021). How these changes cascade into altered food availability for higher trophic levels, such as fish and birds (Peterson et al., 2006), or into changes in beach-dune development remains unknown (De Schipper et al., 2020). This is especially true for nourishments with non-native sediments.
Besides affecting existing macrobenthic communities, an increase in nourishment volume also offers opportunities for strengthening adjacent marine and terrestrial habitats or even create novel habitats by re-arranging environmental conditions in new configurations, as shown for macrobenthic communities (Van Egmond et al., 2018). Understanding how the macrobenthic and plant communities (abundance, biomass, species composition and ecosystem functioning) react to variables such as location, frequency, thickness and grain-size is key to understanding the operating space for eco-friendly coastal nourishment design.
In order to achieve this, we will synthesize existing data to link community-composition and recovery traits to habitat characteristics. We will test and refine these relationships at the Living Lab site. In a final step we will use the information on habitat development and community composition to assess the ecological impact of alternative coastal landscaping, both below and above the water line. The knowledge can be used to design and implement nourishment strategies to develop a healthy, resilient and sustainable sandy coast world-wide.
Improved understanding of the behavior of non-native sediments for coastal nourishments
Coastal nourishments are preferably carried out with similar to native sands from a nearby borrow site. Currently, there is sufficient nourishment sand of this kind available in the North Sea, but these reserves may run out if the accelerated SLR calls for larger nourishment volumes. In that case, we will have to use coarser or finer sands, or even sediments with another mineralogical composition. Moreover, nearby-located non-native sediment may be more attractive because of shorter shipping distances, reducing costs and carbon footprint. This pressure on sand availability is even more urgent in the many countries with smaller nearby supplies than The Netherlands.
Using coarser grained sand may increase the nourishment lifetime, effectively reducing the maintenance requirement. However, it may also result in a steeper beach, which can have a negative impact on swimmer safety as was the case for the 2007 Hoek van Holland beach nourishment. Conversely, finer sand can stimulate dune growth through wind- blown transport, but parts will also be quickly, and often permanently, transported offshore by waves (De Schipper et al., 2020). Next to these morphodynamic effects, non-native nourishment sand may alter the grain-size distribution patterns in the coastal zone, in some cases even beyond the placement area. This can have ecological consequences, as benthic communities depend on the bed sediment composition. So far, we know little of the grain-size effect on nourishment morphodynamics, and the underlying sediment sorting processes (Broekema et al., 2016). The most important question to be tackled is the ultimate destination of nourished sediment, which is essential for the environmental impact of future strategies.
This scientific impact will be realized by a unique combination of field observations at the SOURCE Living Lab site and controlled lab experiments. This improved understanding to use other sediments for coastal nourishments will open up new avenues and methods for flood protection worldwide.
Capability to reliably predict the morphological development and impact of coastal nourishments
Nourishment design is largely based on empirical knowledge, because process-based models have great difficulty in predicting the morphological evolution and impacts of nourishments. This applies in particular to the cross-shore reshaping, as the underlying wave-driven sand transport processes are complex and not well understood (Van der Werf et al., in prep). We do not know how the nourished sand spreads in the on- and offshore directions, and hence we cannot predict how the shoreline and dunes benefit (Huisman et al., 2018). This is problematic, as the existing empirical knowledge is not sufficient to design and evaluate new coastal nourishment strategies to adapt to an accelerated SLR. Uncertain coastal nourishment benefits also make it hard to build a solid multi-stakeholder business case.
In order to achieve this, SOURCE will adopt a triple model approach to bridge the gap between the small, intra-wave sand grain scale (sub-millimeters, sub-seconds) relevant to sand transport, and the large-scale morphodynamics of the complete Dutch coast (100s of kms, decades). The complementary models will be developed using new and existing data and insights, especially from the Living Lab nourishment sites. These process-based numerical models will secure the morphodynamic knowledge developed within SOURCE and allow it to be used for other (international) sandy shore cases.
Interactive gaming environment that enables collaboratively exploring and experimenting with nourishment strategies to foster shared understanding
Enhancing multifunctional coastal landscapes requires developing sand nourishment strategies that integrate flood safety with socio-economic and natural values. To facilitate a stakeholder-driven exploration of such landscapes, the Sand Nourishment Game will be developed within SOURCE. Serious games have proven to be an effective means to support policy-making in environmental management by offering an interactive environment that integrates a system’s technical-physical (e.g. coastal erosion and sea-level rise) and socio-political complexity (e.g. sectoral interests and responsibilities) (Mayer, 2009; Den Haan & Van der Voort, 2018).
The Sand Nourishment Game will offer stakeholders a sense of safety to collaboratively explore and experiment with sand nourishment strategies under current and possible future conditions. The game will include realistic visualizations of our coastline, now and in the future, and indicators of coastal ecosystem services (flood protection included), allowing stakeholders to discuss and assess the value of the co-created landscapes. Co-designing and applying the Sand Nourishment Game will offer two main scientific contributions. Firstly, it will advance our knowledge on using games as interventions (Rodela et al., 2019) in multi-stakeholder decision-making by researching to what extent the game enables stakeholders to co-develop and assess sand nourishment strategies and facilitates social learning. Secondly, from an interaction design perspective, it will further explore how tangible components (e.g. physical game board) can be beneficially combined with digital information (e.g. immersive visualizations) to facilitate multi-stakeholder collaboration and learning (see Den Haan et al., 2020).
Quantification of the social costs and benefits, including spatial quality concepts, to assess different coastal sand nourishment strategies
A key challenge is the integration of different functions of the coastal zone, to which people attach a plurality of values. Firstly, the coastal landscape has different meanings and values to different stakeholders. Secondly, coastal sand nourishments are expected to have both positive and negative impacts on societal values (Horstman et al., 2009), and these impacts change over time and space through dynamic coastal processes. To what extent and for which stakeholders sand nourishment creates value and spatial quality is poorly understood.
SOURCE tackles this problem through a mixed methods approach, in order to address this plurality. We will not only provide new knowledge on valuation of sand nourishments and coastal ecosystems, but also advance the valuation of dynamic coastal systems in general.
Firstly, we use the concept of spatial quality, which we will assess through qualitative and participatory methods. It remains unknown how different sand nourishment strategies contribute to the quality of coastal landscapes, how the spatial quality is perceived by different stakeholders, and how this perception affects the support for future multifunctional coastal nourishment strategies. Co-designed strategies can transparently be ranked and compared using the spatial quality concept. The concept of spatial quality is employed to investigate the non-monetary user value, experiential value and future value of sand nourishment strategies, aiming specifically at often overlooked stakeholders such as inhabitants of coastal towns and coastal business owners.
Secondly, we will use monetary valuation methods to express values for future sand nourishment options in monetary terms, and develop and test a valuation and cost-benefit analysis method that can be transferred to other coastal countries. While costs can be relatively well estimated based on existing projects and expert input, the societal benefits, such as recreational values, lower flood risks and especially ecosystem services values (related to the change in natural quality), are often non-marketed (Turner & Schaafsma, 2015). Therefore, they are hard to assess in monetary terms, with the risk of being ignored in decision making. SOURCE will address the dynamics of the coastal sand nourishment strategies in the monetary assessment by asking households for their perceived values of such dynamic landscapes, which will feed into a social cost-benefit analysis.
Integral approach to co-design multifunctional coastal sand nourishments strategies to enable resilient dynamic coastal landscapes
The Dutch coastal sand nourishment strategy is based on the ‘holding-the-line’ paradigm, in which the 1990 coastline position and the sand volume in the coastal zone should be maintained. This so-called dynamic preservation supports the strategic goals to sustainably maintain flood protection levels and preserve values and functions of the dune areas.
Sea-level rise and socio-economic developments call for the creation of climate buffers that are multifunctional landscapes, supporting various values and functions; a paradigm shift from dynamic preservation to dynamic development. This requires all coastal functions to inform the nourishment strategy from the start. By comparing different sand nourishment strategies and their effect on the wide range of coastal functions, effective and socially-accepted nourishment strategies can be identified. Moreover, stakeholders and decision-makers will be closely involved in the design and implementation of multifunctional coastline management.
Taking a co-design approach to develop multifunctional coastal sand nourishment strategies is not yet common. Therefore, new knowledge is needed to implement this approach. SOURCE will provide key new insights in the effectiveness of different co-design and co-creation activities to realize an integral approach that is both created and supported by a large stakeholder group from science, policy, industry and society (the quadruple-helix model). With this integrative framework, SOURCE aims to identify the synergies and trade-offs between the socio-economic and ecological objectives of large-scale coastal sand nourishment strategies.
Approach
The SOURCE project has the following transdisciplinary structure:
Two dedicated, innovative nourishments along the Dutch coast are our Living Labs (WP 1). One will be realized at the beginning of the project such that the monitoring data, together with other data-sets, can feed into WP 2 that is focused on improved understanding and modeling of the coastal ecosystem.
The other Living Lab nourishment will be co-designed during the SOURCE project, and the lessons learned are especially input to the socio-economic WP 3 and the integrative WP 4.
WP 2 includes understanding of nourishment morpodynamics and sediment pathways (WP 2.1), investigation of ecological effects and the opportunities for coastal landscaping (WP 2.2), exploration of the possibilities of using alternative non-native nourishment
material (WP 2.3) and quantification and prediction of nourishment impacts on coastal state indicators (WP 2.4).
These new insights into the coastal ecosystem will find their way to – and are informed by – the stakeholders through an interactive sand nourishment game that will be built in WP 3.1. This will lead to an improved insight in stakeholder needs and perspectives that will be input to a methodology to determine the spatial quality (WP 3.2) and social costs and benefits (WP 3.3) of sand nourishment strategies.
All comes together in WP 4: the co-creation of sand nourishments strategies that enable a resilient multifunctional Dutch coastal flood defense with high socio-economic and natural values.
Our expected innovations: