Multifunctional Flood Defences

The Organization for Economic Co-operation and Development estimates that by 2070, over 140 million people and € 30,000 billion worth of economic value will need to be protected in the large port and delta cities worldwide. Pressure on land use in these areas is increasing and designing structures and strategies for protection seems possible only when considering multifunctional use. In the meantime, uncertainties about climate change and economic developments present problems in determining a flood protection level. This combined complexity requires technological and institutional innovations.

One of these innovations is the concept of ‘multifunctional flood defences’, as addressed in the Veerman 2008 Commission Report. In its advice to the Dutch government about the future flood protection strategy, this committee proposed to develop integrated and multifunctional solutions at locations where space is scarce.

Multifunctional flood defences are structures that not only protect against flooding from seas, rivers, lakes and other waterways, but also create additional social and economic value. 

Such defences can become relevant when necessary improvements in flood defence systems conflict with urban functions, when on-going urbanisation requires more space, when public funds are under pressure, or when stakeholders pursue previously unthinkable combinations of functions such as a crematorium or parking garage in a dike.

This article focuses on flood protection combined with buildings and objects with a high degree of constructive integration.
• A well-known example of a structurally integrated multifunctional flood defence is the riverfront along the IJssel in Kampen (Figure 1). The flood defence is locally integrated in the houses along the quay. This means that the lower part of the facades of these houses is water retaining. In case of imminent high water, doorways and ventilation grilles can be sealed. In the event of interruptions of the row of houses and on intersecting streets, there are also provisions to offer temporary protection, such as bulkheads and slides.

• A similar example is the Voorstraat in Dordrecht, where the water-retaining walls are situated on the side of the shops facing away from the water (Figure 2). This means that there is a layer of water in the shops during high waters. Due to water-retaining measures, however, that water cannot leave the houses, which ensures that the inner-dike area does not overflow.
• A final example of multi-functionality of a quay wall can be found in Zwijndrecht, where the wall is part of underground car parking (Figure 3). A high degree of integration of functions has been achieved: cars are parked on one side of the wall and the Oude Maas River flows on the other.

Multiple interests

Designing integrated and sustainable multifunctional flood defences is a complex challenge, where different scientific disciplines can provide new insights and solutions. This challenge was picked up by a group of researchers from the Delft University of Technology, University of Twente and Wageningen University, working together in the research programme titled ‘Integrated and sustainable design of multifunctional flood defences’.

The challenges for multi-functionality are the management and maintenance aspects. The responsibility for a multifunctional object is not unambiguous. Dutch district water authorities (the so-called Waterschappen) and the national authority (Rijkswaterstaat) are 100% responsible for flood protection and therefore have different interests than, for example, homeowners or other users of flood defence systems. Secondly, many uncertainties are connected to real estate development, which complicates developing effective long-term strategies for management and maintenance of the structure. Next, from the perspective of integration of flood defences in built-up areas, these structures are often perceived as undesirable or ‘ugly’ objects in the environment. Fourthly, the necessary adjustments to flood defence systems to achieve multi- functionality is complicated by different time scales: the lifespan of functions to be combined often deviates from the lifespan of the flood defence. This requires adaptable and flexible solutions. Finally, stakeholders need to agree on how the reliability of the combined system can be determined. As the physical behaviour of objects in flood defences has not yet been adequately studied, this is a highly relevant challenge.

Cases and tools

In the programme ‘Integrated design of multifunctional flood defences’, various aspects were the subjects of research. From several perspectives, scientific researchers have analysed and developed new or additional knowledge for the following cases: Katwijk aan Zee (structural evaluation and adaptive planning), Zutphen (dike ring reliability), Millingen aan de Rijn (wave overtopping and shearing), the Lekdijk (piping erosion), Vlissingen (flexibility) and Kinderdijk-Schoonhovense Veer (synchronizing and anticipating processes), the Wadden Sea (salt marshes), Rotterdam Feijenoord (adaptive planning) and the Rotterdam Dakpark (structural evaluation, visual design strategies and decision making).

Apart from these Dutch projects, several international cases were the subject of research: Wenduine, Belgium (wave impact on the levee), Great Britain (knowledge transfer), Can Tho, Vietnam (flexible infrastructure), and in the USA, New York (adaptive planning) and a large study in the Houston Galveston Bay in Texas (governance and hydraulic system vision for a ‘Delta Plan’).

In the area of governance, several tools were developed: for complementary decision-making (the ‘Dilemma-cube’), for involvement of stakeholder values in the design phase (‘CIGAS’), and for cooperation between practitioners from different backgrounds (‘Zoden aan de dijk’). (1) 

Flood barriers and developments in urban design

In the Netherlands, various attempts are being made to combine the reinforcement of flood defences with the improvement of spatial quality of the built environment. The need to improve urban quality is a response to the ideas of Modern Movement between 1950 and 1960. Architects like Le Corbusier, Garnier and Giedion argued for larger cities by creating a new balance between large open spaces and voluminous tower buildings. Vast new infrastructures such as wide motorways would improve the accessibility of cities and robust flood defences would protect them from flooding. However, these roads and structures literally and figuratively cut through the relationship between cities and rivers or seas. The result was a separation of functions such as living, working and recreation and the destruction of many old neighbourhoods, which were originally oriented towards the water. As Han Meyer, Professor of Delta Urbanism in Delft, argues, this has led to deterioration in the quality of life in cities worldwide. (2) 

From 1980, a counter-movement arose and developed new spatial concepts to reduce the dominant role of large-scale infrastructures. This led to a new type of waterfront, which was well integrated in the urban context. Good examples are the Oosterdokseiland in Amsterdam and the Kop van Zuid and the Stadshavens in Rotterdam. Combining flood protection with increasing spatial quality became a globally embraced principle for improving the quality of life in cities along rivers and seas. A good example is the Dakpark (roof park) in Rotterdam (Figure 4) where a shopping complex and a flood defence have been successfully combined in one project with a large city park on top.

When designing urban water infrastructures, two design cultures come together: engineering design and spatial design. 

However, these do not automatically connect to each other. Since the 1970s, technical and spatial designers have taken different paths, but the process of design is not efficient when both disciplines start their work separately. Not to mention the radical change in influence of various stakeholders since the ’70s of the last century, which was unmistakably visible at the time in the social resistance to the planned damming of the Oosterschelde and the demolition of levee-houses in Brakel and Sliedrecht along major rivers. Therefore, we studied how engineering and spatial design cultures can be integrated and how stakeholders can be optimally involved in the design process.

Integrating technical and spatial design

Engineering design methods usually distinguish a number of logical steps: analysing the problem, drafting requirements, generating alternatives, verifying these alternatives to the requirements, evaluating the alternatives and selecting the best alternative. These methods work from function to form and are iterative because the different steps can be repeated as more knowledge is gathered. The process is cyclical, in the sense that the process can be repeated at different levels of detail. Such methods are suitable for phasing and organising the design process within a team.

Early methods for spatial design were very similar to engineering methods, but received increasing criticism from the 1970s onwards. Spatial designers confronted the multiple analyses that preceded the creative process and the sequential nature of the technical method. This was seen as inhibiting the development of creative ideas and undoing the learning and experimental character of the design process.

In this light, researcher Mark Voorendt proposed an integrated design method in which engineering and spatial design complement and reinforce each other and several disadvantages of each separate method are overcome. The method consists of a number of steps that require different activities and follow one another, but in a highly iterative process so that the learning nature of the design process is retained.

Most of the analysis and formulating the programme of requirements is done after initial design concepts are developed. This ensures that designers are not limited in their creativity. After the creative process, the necessary verifications are still carried out to guarantee that the resulting design is feasible in terms of space, time, money, constructability and maintainability. The integrated method also provides opportunities for stakeholders to participate in the process.

Stakeholder-inclusive design

The integrated design of multifunctional flood defences has not only ‘hard’ engineering and spatial aspects, but also ‘softer’ social, legal and economic aspects. Technically optimal solutions are not always optimal for local residents or other stakeholders. Designers can be confronted with this when a design enters the mandatory ‘public participation’ phase and some parties turn out to be resisting the proposed design. 

In many design processes, stakeholders are therefore invited to bring in local knowledge and interests in the design phase. Yet, this sounds easier than is often the case in practice. Because, how does one ensure that values and wishes of residents are included in the design from the very beginning and how do you get them to understand the technical aspects of the project?

In response to these questions, researcher Baukje Kothuis, together with colleagues from the Multifunctional Flood Defences (STW) and Multi Actor Systems Research (TU Delft), developed the so-called CIGAS tool (Contested Issues Game Structuring Approach).

This two-day workshop method allows for values and interests of stakeholders to be taken into account in the technical and spatial design of the multifunctional barrier. The method does not strive towards ‘consensus’; on the contrary, it is precisely the different and often divergent interests that are explicitly recognised. However, one step in the more common design process is moved to the very end: the determination of technical and spatial requirements and the final design by professionals. The design process therefore changes in order, in accordance with Voorendt’s method.

First, local residents and other stakeholders bring in all parties that play or should play a role in their eyes and find solutions:
Step 1: ‘Who is worried or has an interest?’ Next, they jointly create a broad systems-overview by answering the following question in
Step 2: ‘Why are these parties concerned or have an interest?’ This step makes visible – for all involved – the large diversity of values that are part of the new flood defence: ecological, spatial, cultural, legal, economic, social, political and ethical. 
Step 3: ‘Design possible outcomes involves’ answers the question: ‘What could this area look like: positively and negatively?’ The participants are allowed to describe and draw alternatives that may far exceed current technological possibilities. They do not have to be politically correct, to satisfy everyone or be feasible in the short term. Even a beach between Hoek van Holland and Harwich, or a glass dike with saunas incorporated, is therefore acceptable. The one limitation is that the outcome must be physically possible, even if it is in the distant future with yet unknown technology. Therefore, ‘In the outcome, the North Sea should be yellow with pink butterflies, because that matches nicely with my swimwear’, is not permissible. The participants take the previously mentioned stakeholders and the values from the system overview into account while creating their ‘utopian’ and ‘dystopian’ outcomes (the ‘dreams’ and ‘nightmares’). At the end of this step they present their results to one another with a brief explanation. 
Step 4: ‘Rank the outcomes’. Participants each represent one of the named stakeholder parties and, from that specific perspective, rank each of the outcomes. This phase invariably brings up a broader understanding of the complexity of the multifunctional flood defence design under discussion and participants come up with questions about further design and processes. The workshop leaders then perform Step 5: ‘Calculate the Pareto Optimum’. The result of these calculations offers input for Step 6: ‘Feedback & Follow-up’. Discussing which (combinations of) outcomes are most likely to support a majority of parties.

The goal in the CIGAS workshop is not to come to one final solution. The optima calculated by this method give the technical and spatial experts the opportunity to make designs that intrinsically include the values and wishes of the stakeholders. This tool also helps to give stakeholders a broader insight into the design-assignment and, from a shared perception of optimal outcomes, a path to commitment for further involvement. Ideally, the stakeholders also test (validate) the subsequent professional designs, to ensure that their values and wishes are correctly interpreted and processed. A final, widely supported, technical and spatial optimal design can then follow.

(1) A comprehensive overview of these case studies, tools and the underlying knowledge developed can be found in the book Integral Design of Multifunctional Flood Defences:Multidisciplinary Approaches and Examples. The book is available digitally (respository.tudelft.nl) and as hard copy (to be requested by mail: b.l.m.kothuis@tudelft.nl) (2) V.J. Meyer (2017), ‘How to support and destroy the public domain of the city’, in Integral design of multifunctional flood defences (Kothuis & Kok)