Hydraulic engineering infrastructure is supposed to keep functioning for many years and is likely to interfere with both the natural and the social environment at various scales. Due to its long life-cycle, hydraulic infrastructure is bound to face changing environmental conditions as well as changes in societal views on acceptable solutions. This implies that sustainability and adaptability are/ should be important attributes of the design, the development and operation of hydraulic engineering infrastructure. Sustainability and adaptability are central to the Building with Nature (BwN) approach. Although nature-based design philosophies, such as BwN, have found broad support, a key issue that inhibits a wider mainstream implementation is the lack of a method to objectify BwN concepts. With objectifying, we mean turning the implicit into an explicit engineerable ‘object’, on the one hand, and specifying clear design ‘objectives’, on the other. This paper proposes the “Frame of Reference” approach as a method to systematically transform BwN concepts into functionally specified engineering designs. It aids the rationalisation of BwN concepts and facilitates the transfer of crucial information between project development phases, which benefits the uptake, acceptance and eventually the successful realisation of BwN solutions. It includes an iterative approach that is well suited for assessing status changes of naturally dynamic living building blocks of BwN solutions. The applicability of the approach is shown for a case that has been realised in the Netherlands. Although the example is Dutch, the method, as such, is generically applicable.

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By definition, Building with Nature solutions utilise services provided by the natural system and/or provide new opportunities to that system. As a consequence, such solutions are sensitive to the status of, and interact with the surrounding system. A thorough understanding of the ambient natural system is therefore necessary to meet the required specifications and to realise the potential interactions with that system. In order to be adopted beyond the pilot scale, the potential impact of multiple BwN solutions on the natural and societal systems of a region need to be established. This requires a ‘reality check’ of the effectiveness of multiple, regional-scale applications in terms of social and environmental costs and benefits. Reality checking will help establish the upscaling potential of a certain BwN measure when addressing a larger-scale issue. Conversely, it might reveal to what extent specific smaller-scale measures are suitable in light of larger regional-scale issues. This paper presents a stepwise method to approach a reality check on BwN solutions, based on the Frame of Reference method described in a companion paper (de Vries et al., 2021), and illustrates its use by two example cases. The examples show that a successful pilot project is not always a guarantee of wider applicability and that a broader application may involve dilemmas concerning environment, policy and legislation.

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Ecosystem destruction not only incurs large costs for restoration but also increases hydraulic forces on existing flood defence infrastructure. This realisation has made the inclusion of ecosystems and their services into flood defence schemes a rapidly growing field. However, these new solutions require different design, construction and management methods. A close collaboration between engineers, ecologists and experts in public administration is essential for adequate designs. In addition, a mutual understanding of the basic principles of each other’s field of expertise is paramount. This chapter presents some simple approaches for the integration of ecosystem-based measures into coastal engineering projects, which may be of use to experts from a range of fields. Further, it stresses the importance of ecological processes which determine the persistence and health of coastal ecosystems, a point which is rarely emphasised in coastal engineering. The main aim of this chapter is to highlight the role of ecosystem properties for flood defence to stimulate the coastal engineering community in adopting an ecosystem view. In the near future the hope is that greater awareness of ecosystem processes will lead to more sustainable and climate-robust designs. For this, engineers, ecologists and social scientists involved in coastal defence projects need to develop a common language, share the same design concepts and be willing to share the responsibility for these innovative designs.

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Adaptation planning for flood risk forms a significant part of global climate change response. Engineering responses to higher water levels can be prohibitively costly. Several recent studies emphasize the potential role of ecosystems in flood protection as adaptive risk reduction measures while also contributing to carbon fixation. Here, we use a conceptual model study to illustrate the built-in adaptive capability of ecosystems to reduce a wide range of wave heights, occurring at different water levels, to a narrower range. Our model shows that wave height of waves running through a forested section is independent of initial height or of water level. Although the underlying phenomenon of non-linear wave attenuation within coastal vegetation is well studied, implications of reducing variability in wave heights for design of ecosystem and levee combinations have not yet been properly outlined. Narrowing the range of wave heights by a vegetation field generates an adaptive levee that is robust to a whole range of external conditions rather than only to a maximum wave height. This feature can substantially reduce costs for retrofitting of levees under changing future wave climates. Thereby, in wave prone areas, inclusion of ecosystems into flood defense schemes constitutes an adaptive and safe alternative to only hard engineered flood risk measures.

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Underwater environments in ports are designed for harbour activities solely. However, by simple and cost-effective measures, suitable habitat for underwater flora and fauna can be created. This is expected to have positive effects on higher trophic levels, such as fish, and improve water quality, by enlarging filter feeder biomass. In this study we developed 'pole hulas' and 'pontoon hulas', consisting of hanging ropes of different materials. The pole hulas are made up of many 6. mm thick and 55. cm long strings just above and below the mean low water level (MLWL) around poles. The pontoon hulas resemble raft like structures with 12. mm thick and 150. cm long ropes within the open space of mooring pontoons. The first experimentation with these structures was executed in the polyhaline harbours of the port of Rotterdam. The pole hulas were rapidly colonised by a variety of organisms. Above MLWL a seaweed community dominated on the strings. Below MLWL Mytilus edulis (the Blue mussel) was found to be the dominating species after a few months. In the dense layer of M. edulis on both pole hulas and pontoon hulas many mobile soft-bottom amphipods and young ragworms occurred, which means that colonisation on these structures compensate for biodiversity loss of bottom fauna due to dredging and disturbance by propellers of ships. Settlement of the exotic Crassostrea gigas (Pacific or Japanese oyster) did not occur on the strings of the pole hulas, the ropes of the pontoon hulas and not on the poles with hulas.Wet biomass (including shells) on pole hulas was positively correlated with depth and on average 4.4-11.4 times higher compared to biomass on reference poles. Colonization of the pontoon hula ropes was similar to colonization of the pole hulas below MLWL. Biomass production per rope was density dependent and optimal density of ropes was estimated at 4-8ropesm -2. Biomass (mainly M. edulis) on the ropes of pontoon hulas decreased to a half from the edge to the heart of the hula demonstrating the limitation of food by competition.It was concluded that ecological engineering in the port of Rotterdam with simple structures such as pole and pontoon hulas strongly enhances sessile biological production and biodiversity. This is likely to result in a positive impact on local water quality, and, if applied at larger scales, may have positive influences on the remains of Rhine-Meuse estuary.@en

Traditionally, protection of the coastal area from flooding is approached from an engineering perspective. This approach has often resulted in negative or unforeseen impacts on local ecology and is even known to impact surrounding ecosystems on larger scales. In this paper, the utilization of ecosystem engineering species for achieving civil-engineering objectives or the facilitation of multiple use of limited space in coastal protection is focused upon, either by using ecosystem engineering species that trap sediment and damp waves (oyster beds, mussel beds, willow floodplains and marram grass), or by adjusting hard substrates to enhance ecological functioning. Translating desired coastal protection functionality into designs that make use of the capability of appropriate ecosystem engineering species is, however, hampered by lack of a generic framework to decide which ecosystem engineering species or what type of hard-substrate adaptations may be used where and when. In this paper we review successful implementation of ecosystem engineering species in coastal protection for a sandy shore and propose a framework to select the appropriate measures based on the spatial and temporal scale of coastal protection, resulting in a dynamic interaction between engineering and ecology. Modeling and monitoring the bio-physical interactions is needed, as it allows to upscale successful implementations and predict otherwise unforeseen impacts.

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