|BwN Building Blocks||BwN Toolbox||Pilots and cases||BwN Knowledge|
This section contains Building Block descriptions, grouped in Design Themes, that are based on knowledge generated within the BwN projects. The term Building Block refers to the notion that in general any conceptual Building with Nature design consists of a number of elements that each have specific design or procedural considerations. The information in the Building Blocks pages should facilitate some rough design estimates that can serve as guidance for area selection and design. Based on experience from previous projects, they should also help to come up with rough estimates of construction cost. Where appropriate references to relevant project cases and tools are made.
Some Building Blocks provide practical guidance on how to structure project development organisations and procedures in order to practically and effectively allow BwN integration within a project.
Shore nourishment or beach nourishment — also referred to as replenishment — is a maintenance measure by which sediment from outside the area is added to a (usually eroding) shore. A wider beach or a higher foreshore can reduce dune erosion or storm damage to coastal structures by dissipating energy across the surf zone. Shore nourishment is typically part of a larger coastal maintenance strategy. It is usually a repetitive process, since it does not remove the physical forces that cause erosion: it just mitigates their effects. Regular beach nourishment, i.e. placing a relatively small amount of sand at the moment it is needed in line along the shore or on the beach, has the disadvantage of frequently disturbing the coastal ecosystem. To avoid this disturbance and at the same time make new room for environmental processes, different types of beach nourishment are proposed, in which the sand volume is not just placed in line along the beach or the foreshore.
We consider two types of nourishment here:
- Feeder beaches: large concentrated sand deposits on the foreshore, intended to gradually feed the adjacent shore via the natural forces working on it.
- Perched beaches: an artificial beach fill, extending from the shoreline down into the foreshore, where a submerged stable sill or dam is placed to support the lower part of the profile: the profile is intended to provide a dynamically stable, sustainable and ecologically attractive protection.
This building block covers the spatially concentrated placement of (relatively) large sand volumes for coastal development. Such nourishments are placed at a specific location with the aim to gradually feed the surrounding coast. Wind, waves and currents will spread the sediments along the coast, which is a typical example of 'building with nature'. Such a nourishment will contribute to the coastal safety in the long-term while creating more opportunities for nature and recreation.
An emerged concentrated nourishment along a sandy shore, whereby part of the nourishment is dry, provides more space for recreation, water sporting and beach lovers. In addition, new dunes and vegetation could develop increasing nature value. In case of an unprotected nourishment, the shape and bathymetry of the nourishment will however change continuously under the forcing of tide, wind and waves (see Sandy Shores under Environments). This requires an adaptive management strategy to anticipate on unforeseen developments. The Sand Engine Delfland is a good example of an integrated solution providing safety against flooding while facilitating nature development and recreation.
On steep, eroding beaches, the use of a perched beach may be useful to reduce sand losses or to reduce the sand volume required for nourishment. A perched beach is at the seaward side supported by an underwater sill or breakwater. Landward from this sill, where nourishment may be applied, a dynamic equilibrium profile will develop. If nourishment is applied, the use of an underwater sill can reduce the volume of material needed as compared to a situation where no sill is in place. When a submerged breakwater is applied and the hydrodynamic energy behind the structure is reduced, erosion may also be reduced.
The perched beach concept provides several opportunities to enhance biodiversity. In the lee of the structure, the reduced hydrodynamic energy may yield suitable conditions for sea grass meadows, for instance. The structure itself may provide hard substrate for coral establishment, oyster reefs etc. Mangroves may cover the breakwater if it is (partly) emerged.
For offshore locations where large volumes of sand are extracted, for reclamation purposes or for coastal nourishment, important choices are between a large shallow or a smaller deep pit and between leaving behind a flat seabed and a bed with relief after the extraction. If the pit is chosen too shallow the area may become very large, if it is made too deep the lower water layers may become anoxic. Research has shown that a seabed with large-scale bedforms (sandwaves) comes with more biomass and a higher biodiversity than one without bedforms. Intelligent scheduling of the mining operation makes it possible to leave a bed with sandwave-like features behind without significant negative effects on the project’s schedule or economics.
The Building Block Ecological landscaping of seabed provides guidance on this issue based on a large-scale experiment in the North Sea.
The expected worldwide increase the demand of marine sand extraction due to economic growth and urbanisation and the long-term threats of climate change call for innovative approaches for sand extraction activities. Marine sand extraction traditionally focuses on minimizing environmental impact and quick recovery of seabed sediment composition and benthic assemblages. With largescale extraction, this conservative approach can lead to constraining mitigation measures. Moreover, the potential of ecological development, cost reduction and a more efficient use of scarce space are not recognized.
Ecological landscaping of sand extraction sites involves the realisation of seabed level gradients and other morphological features in newly dredged sites. The overall aim is to make the sand extraction site attractive for a variety of macrozoobenthic species that in turn attract demersal fish, mammals and birds. This is done by creating different bedforms and/or combinations of sediment characteristics which provides ideal settlement and habitat circumstances for a larger variety of species. Due to this landscaping, the re-colonization of the mined pit is presumably faster and results in a higher biodiversity than in a traditionally dredged sand extraction site.
Ecosystem engineers are organisms (plants or animals) whose presence or activity alters its physical surroundings or changes the flow of resources, thereby creating or modifying habitats and influencing all associated species (Jones et al. 1994, 1997). Many ecosystems are greatly affected by ecosystem engineering species. Given the highly physical nature of the estuarine and coastal environment, organisms that affect the physical structure of these ecosystems can have significant influences on functions and services (e.g., Barbier et al. 2011). A diversity of organisms physically engineer estuarine and coastal ecosystems, including salt marshes, willow tidal forests, mangroves, seagrass beds, coral reefs and bivalve reefs, kelps.
There is growing recognition that the ecosystem engineering concept can contribute to ecological applications such as restoration and ecosystem management (Byers, Cuddington et al. 2006; Crain and Bertness, 2006). In recent years the interest in using them in coastal defense has grown. Especially the ecosystem engineering properties of reducing wave energy and trapping sediments make species such as reef building bivalves, mangroves and salt marsh plants interesting target species. All these species have in common that they can alter an otherwise bare soft sediment environment into a complex, three-dimensional structure. These structures influence abiotic conditions and interact with kinetic energy and materials within the abiotic environment, e.g. alter tidal flows, attenuate wave action and trap sediments. As a consequence, the abiotic change induced by an ecosystem engineer will cause biological change. The challenge is to determine how, when, where, and which organisms engineer habitats with important outcomes for ecosystem and community processes.
It is believed that the use of ecosystem engineers in coastal management can contribute to a more sustainable, cost-effective way of protecting our coasts, especially in the light of climate change and sea level rise. Secondly, there is also a need for methods of coastal protection that incorporates the natural dynamics and processes of the ecosystem, allowing a more resilient and robust future coastline (Day, Psuty et al. 2000). Only in this way many ecosystem services coastal habitats in general and ecosystem engineers in particular provide can be safeguarded.
Ecosystem engineers can be used to stabilize and protect shorelines and intertidal habitats against erosion and to minimize wave attack on the coast (e.g. Borsje et al. 2011). Furthermore. ecosystem engineers can induce positive facilitation cascades in which a certain engineer (e.g. an oyster reef) can have positive effects on the growing and survival conditions of another ecosystem engineer (e.g. sea grass). Also ecosystem engineers possibly can help to extend sustainability (i.e. lifetime) of sand nourishment sites by reducing erosion of the nourished sediment. By creating the right preconditions for settlement and growth a specific ecosystem engineer can develop and persist over time. The additional advantage is that several of these structural ecosystem engineers that inhabit intertidal habitats can grow to keep up with sea level rise (e.g. salt marshes).
The following Building Blocks can be consulted for more information:
- Habitat requirements for shellfish
- Habitat requirements for mangroves
- Habitat requirements for corals
- Habitat requirements for seagrass
- Habitat requirements for salt marshes
Much of present-day coastal infrastructure offers perspectives not only to protect the coast, but also to create suitable habitats for certain ecosystems. This can be beneficial, as natural ecosystems can contribute significantly to coastal protection and provide other services. Moreover, most ecosystems, as opposed to traditional hard structures, are able to adapt to (relative) sea-level rise.
‘Ecosystem engineers’, i.e. species that influence their own habitat, form complex structures in the subtidal and intertidal zone and can provide sustainable shoreline or shoal edge protection. Next to shellfish as described herein, other ecosystem engineers are corals, mangroves,saltmarshes and seagrass. To successfully include ecosystem engineers in coastal protection, certain requirements have to be met for establishment and sustainable growth. Examples are requirements on hydrodynamic conditions, water quality, soil characteristics, light availability, etc., but also biological preconditions (e.g. connectivity to other or similar ecosystems). Parts of these requirements can be engineered or fostered through human intervention, while others cannot. This building block describes the habitat requirements for shellfish reefs, based on research, application and knowledge on the Pacific Oyster.
The majority of present-day coastal infrastructures can be redesigned to ensure not only coastal protection, but also to create suitable habitats for certain ecosystems. This can be beneficial, as many natural ecosystems can contribute significantly to coastal protection. Moreover, most ecosystems, as opposed to traditional hard structures, are able to adapt to (relative) sea-level rise.
‘Ecosystem engineers’, i.e. species that influence their own habitat, form complex structures in the subtidal and intertidal zone and can provide sustainable shoreline or shoal edge protection. In addition to the mangroves described herein, other ecosystem engineers are corals, salt marshes, seagrass and shellfish. To successfully include ecosystem engineers in coastal protection, certain requirements have to be met for the species to establish and grow sustainably. Requirements may concern hydrodynamics, soil characteristics, morphology, etc., but also biological preconditions (e.g. connectivity to other or similar ecosystems). Parts of these requirements can be engineered or fostered through human intervention, but others cannot. This building block describes the habitat requirements for mangrove forests.
The majority of present-day coastal infrastructure can be redesigned to ensure not only coastal protection but also to create suitable habitats for certain ecosystems. This can be beneficial, as many natural ecosystems can contribute significantly to coastal protection. Moreover, most ecosystems, as opposed to traditional hard structures, are able to adapt to (relative) sea-level rise.
‘Ecosystem engineers’, i.e. species that influence their own habitat, form complex structures in the subtidal and intertidal zone and can provide sustainable shoreline or shoal edge protection. Next to coral as described here, otherecosystem engineers are mangroves, salt marshes, seagrass and shellfish. To successfully include ecosystem engineers in coastal protection, certain requirements have to be met for establishment and sustainable growth. Examples are requirements on hydrodynamic conditions, water quality, soil characteristics, light availability, etc., but also biological preconditions (e.g. connectivity to other or similar ecosystems). Parts of these requirements can be engineered or fostered through human intervention, while others cannot. This building block describes the habitat requirements for coral reefs.
Many coastal defence systems can be redesigned in such a way that they not only ensure coastal protection, but also create suitable habitats for certain ecosystems. This can be beneficial, as those ecosystems can contribute to coastal protection, are able to adapt to changing environmental conditions such as (relative) sea-level rise and provide a variety of other services.
‘Ecosystem engineers’, i.e. species that influence their own habitat, form complex structures in the subtidal and intertidal zone and can provide sustainable shoreline or shoal edge protection. Apart from seagrass as described below, other such ecosystem engineers are corals, mangroves, salt marshes and shellfish. To successfully include ecosystem engineers in coastal protection, certain habitat requirements have to be met for establishment and sustainable growth, such as hydrodynamic conditions, water quality, soil characteristics and light availability, but also biological preconditions (e.g. connectivity to other or similar ecosystems). Part of these requirements can be engineered or fostered through human intervention, but others cannot. This building block describes the habitat requirements for seagrass meadows.
Coastal Zonation Strategies
Part of the solutions for reducing flood risk and creating a sustainable resilient coast could be found inland. Although many of these areas are intensively used and leave little room for ecosystem restoration, there are areas that show potential to integrate wetland development into a coastal zone. In many subsided areas behind the dikes, for instance, artificial drainage draws up saline groundwater, whence the yield of agriculture becomes marginal and drainage becomes too expensive. Moreover, in the province of Zeeland, the Netherlands, the successive stages of land reclamation have resulted in areas bounded by a primary dike and an older secondary dike. In these so called “Inlagen” or coastal buffer zones, profitable agriculture has become unfeasible. By connecting these inland areas with the water system outside the primary dikes, a broader coastal zone with a low salinity gradient is created, which can take over part of the ecological functions of a natural coastal zone. Depending on the other functions in the area (e.g. housing, recreation, aquaculture), the connection with the outside water can consist of pipes, dikes that are spilled over during storms, or openings in the outer dike. The new areas can be combined with other functions such as housing, recreation or aquaculture.
Coastal zonation strategies elaborated here are:
Managed realignments use existing landscape elements to incorporate into a coastal zone. However, here the primary dyke is cut through or removed. Therefore, the newly created coastal zone becomes part of the water system and can influence the hydrodynamics of the system, most often during high water.
Coastal buffer zones use existing landscape elements to incorporate into a coastal zone. The primary dike stays in place, but is adapted to create habitats in inland areas. The secondary dike has to be reinforced to secure safety.
Inland shores are primarily applicable along freshwater lakes to create an inland freshwater buffer that is connected to the adjacent lake. The area that is created can host functions such as living and recreation. The primary dyke maintains its function, and siphons are constructed to create the connection.
Controlled inundation of land by setting back sea defences is an increasingly used method for coastal protection and anticipation to climate change. In the United Kingdom this so-called “managed realignment” is applied widely and considered a cost-effective and sustainable response to loss of biodiversity and sea level rise. It is also applied in other countries such as the United States, Germany and Belgium.
By re-inundating land the coastline is placed backwards and new intertidal area is created. The area is enclosed by a secondary dike on the landside to ensure safety of the hinterland. The goal is to create the right circumstances for succession of saltmarsh vegetation. Once saltmarshes develop the vegetation will enhance sedimentation and the area will become higher and is able to grow with sea level rise. Saltmarshes can reduce wave energy and improve the stability of the dike.
Managed Realignment can be applied to many different situations that fall within the scope of coastal and flood management. Succes is also dependend on local boundary conditions. It is important to be clear on the aim and purpose of the proposed project at the beginning. Without this it may be difficult later to determine the success/failure of the scheme in meeting its objectives. It is also important at the outset of a project to identify any potential opportunities and/or constraints. Managed Realignment presents the opportunity for a variety of benefits, though such opportunities may also have associated constraints.
An “inlaag” is a predominantly salt/brackish zone along the coast between two dikes. Historically these areas arose when people built a spare inner dike parallel to the coastal defence when there was a threat of dike failure. The principle of a coastal buffer zone is interesting from a coastal protection point of view and elaborated here. Because of the presence of a secondary dike, the primary coastal defence can suffice with lower safety standards as for example reduced height. Limited overflow during extreme high water conditions is acceptable because the secondary dike will stop the water from inundating the land behind the secondary dike. This is interesting from a cost and dike maintenance point of view. The area between the dike is not suitable for high quality land use as housing, but can serve as nature and recreation area and also has potential for aquaculture.
An inland shore is an area for water storage connected to a nearby lake or river in which ecosystem services are optimized for multiple land use, thereby creating new economic opportunities. Large water level fluctuations are taken into account in advance and optimizing sustainability is a red line in the whole concept. Inland shores are connected to the lake or river through inlets in the dike. Connections to the regional water system are optional but advisable. Inland shores can store and release water if needed, allowing the area to function as a climate buffer. In addition, the design takes into account the possibility to function as a helophyte filter to allow improvement of water quality which is considered to be essential for proper functioning. Additional functions (e.g. recreation, fishing, aquaculture, floating infrastructure for living and working, sustainable energy production by sun, wind and water, floating agriculture, nature development) can be added depending on the desires of stakeholders.
Low-lying delta areas often use dikes and other hard coastal defence structures to protect the land against flooding, and harbour structures such as piers, docks and jetties for transport purposes. On top of their primary function, these structures are often used by a variety of plants and animals for growing, reproduction, nursery and feeding.
Coastal defences can be improved in this respect by adapting traditional coastal engineering structures to this ecosystem function. This may even have a positive effect on the structure itself: extra dike stability and wave damping may be provided by deliberate introduction of vegetation such as saltmarsh, reeds, shrubs or trees. Eco-friendly revetments can contribute to the ecological value of a dike and – depending on their location and design, dikes may also host a range of other functions such as living, meadow-land and recreation.
Several pilot experiments have been initiated along the Dutch coast. Also outside the Netherlands, projects for ecologically enriched seawalls are being developed. Based on the outcome of these experiments, the various designs are being improved continuously. Here we consider the following types of structure enrichment:
- Soft Eco-Levee: Replacing the traditional 'hard-cover' design, the Soft Eco-Levee is in essence a safe dike constructed entirely of sediments. Added stability and wave dampening may be provided by deliberate introduction of vegetation such as saltmarsh vegetation, reeds, shrubs or trees.
- Rich revetments and foreshores: This concept aims to create highly variable habitats in the intertidal and subtidal zone of structures, utilizes a variety of different materials, gradients and shapes.
- Biodiverse hard substrates: The intertidal region of a seawall represents a very stressful habitat. Biodiverse hard substrates applies complex concrete tiles attached to seawalls can enhance their biodiversity.
Foreshores in freshwater environments can consist of freshwater wetlands or floodplains. A shallow foreshore or floodplain can contribute in different ways to the strength, the stability and the flood protection capacity of a dike. Under certain conditions the dike’s crest can even be made lower than in a traditional design due to the wave-attenuating effect of the foreshore. This may be enhanced by introducing vegetation such as reeds, shrubs or trees. Additionally, the foreshore can increase levee stability and increase the seepage length. In the absence of a natural foreshore, a gradually sloping foreshore levee can be constructed. Main characteristics of this levee are the gradual slope, in comparison with the steep slopes of natural levees, and the different vegetation zones on this slope that play a role in reducing flood risk. The habitats that can develop on the slope of this levee provide services to the adjacent ecosystem and opportunities for recreation and landscaping. If the adjacent water contains enough sediment to be trapped by the vegetation, the combination of sediment trapping and vegetation-induced soil formation enables the foreshore to adapt to a slowly increasing water level.
Traditionally revetments are designed to provide a safety. This leads to large scale monotonous application of materials and shapes that are not optimized for habitat diversity. The Rich Revetment concept aims to create highly variable habitats in the intertidal and subtidal zone of dikes and foreshores while maintaining safety levels. This approach utilizes a variety of different materials, gradients and shapes to create differences in height, hiding places in a variation of environments with different exposure levels to current and waves. In some designs water is stored in tidal pools. Other designs create highly structured surfaces to provide shelter and attachment opportunities for many species of animals and plants. These solutions are suitable for engineers involved in dike (re)construction and maintenance project or other water related infrastructure such as harbours, quays and piers.
Management of fine sediments
The health and abundance of life in aquatic environments directly depends on a number of parameters such as nutrient availability and light penetration. Indirectly, many other factors affect the health of an aquatic ecosystem. One of the most important factors is turbidity, which can, amongst others, alter the conditions for light penetration. The degree of turbidity is determined by the amount of matter that is available and that becomes suspended into the water column. This matter consists of natural living organisms (e.g. algae), dead organic matter and fine sediments. Fines sediments can be released into the environment due to human activities, and therefore projects should include adequate assessments and smart management of fine sediments.
The release, re-suspension and dispersal of fine sediments can be caused by natural processes, such as waves and currents, but also directly and indirectly by anthropogenic influences like navigation, fishery (trawling), dredging, and the construction of marine structures. Assessing the overall environmental impact of a project on turbidity requires the following approach:
- Ecological reconnaissance: what are the most sensitive receptors in the ecosystem and what level of turbidity-induced stress can they take? This might imply establishing a turbidity threshold for the sensitive receptors in the area.
- Physical prediction: how much turbidity will be created by the scheduled activities? Will the increase in turbidity remain below the thresholds?
- Compliance monitoring: what turbidity values are measured during the project execution? Do turbidity levels develop as predicted?
- Feedback on research: is the impact of the actual turbidity on the sensitive receptors as predicted? Does this lead to new insights that can be of use to the present and/or future projects?
Understand the system
Efforts to control and/or mitigate ecological effects of sediment-induced turbidity start with understanding the site-specific processes around the release and dispersal of fine sediments, and by being able to assess and foresee the negative and in some case positive impacts.
Potential measures to positively influence these processes may range from sediment source release reduction to catching or filtering suspended material from the water column.
The following Building Blocks provide guidance for fine sediment management:
- Smart handling of fine sediments: understanding the physical behaviour of fine sediments and how this insight can be used for sustainable project development.
- Assessment of dredging-induced turbidity: assessing the expected release and dispersion of fine sediment from dredging/construction activities.
- Adaptive management and adaptive monitoring of dredging-induced turbidity.
Fine sediment contributes to changes in bed level and bed composition, water transparency and water quality. All these are important parameters for BwN design. Sometimes fine sediment deposits are a welcome or even essential part of the system, for example on tidal flats and in marshes because they provide suitable conditions for certain species and hence may favour biodiversity. Sometimes such deposits are unwelcome, for example on tourist beaches or in harbours and access channels requiring maintenance dredging.
Sediment plume modelling and monitoring has an increasingly important role in the environmental impact assessment of dredging and disposal works. Sediment plume assessments are generally based on complex, time-consuming numerical modelling. Little is known on source terms and spatial / temporal variation of the character of source terms in combination with the complex hydrodynamic conditions.
The objective of this building block is to provide background information / a guideline when assessing, modelling and monitoring sediment plumes and source terms.
Compared with traditional projects, ‘Building with nature’ initiatives apply a more integral perspective by definition. ‘Building with nature’ initiatives take among others scale interactions into account and seek for integration of multiple stakes and sectors. ‘Building with nature’ thus by definition touches upon multiple societal agenda’s, stakes and vested interests. For support and societal acceptance, a larger array of stakeholders needs to be involved. Achieving broad acceptance of the building with nature concept is complex and potentially time-consuming, although in later project stages broad acceptance may well help to regain the time lost.
Furthermore ‘Building with nature’ design has also to be navigated through multiple applicable sector regulations and procedures, which often takes a capable hand, nature regulation often aim for conservation of eco-systems and less at developing eco-systems.
A necessary condition to achieve support and feasibility is that all parties involved are able and willing to stand for the joint goal, and to accept the consequences and uncertainties associated with the BwN-approach. And, finally, project arrangements, normally determining the business side of a project, shall be such that one can deal with the nature-dimension of this approach.
The following building blocks provide guidance on:
- Strategic spatial planning: how to frame the initial stages of a building with nature approach within the larger context of international, national or regional development?
- Governance assessment and scoping: how to embed the building with nature approach in the part of society involved in and touched upon by the project?
- Innovative Contracting for BwN: on the formats for contractual arrangements, during procurement and during implementation, that provide for the amount of flexibility enabling building with nature approaches.
This Building Block describes the importance of governance assessment and scoping in BwN. Scoping and decision-making processes are essential parts of a BwN project. The feasibility of a BwN-approach depends on the connection with society and decision makers, effectively to anchor BwN. It is important for proponents of a BwN-approach to involve important actors and not to overlook regulations. The strategic question how to connect a design process to society should be integral part of every BwN-project. There is no single strategy that guarantees success in all cases. A good participatory process is custom-made and timing is essential. A general rule of thumb is that participating early in preparatory activities often offers the best opportunities to effectively promote BwN-principles and alternatives. The governance context often provides important triggers or indicates potential stumbling-blocks that need to be addressed before any Building with Nature idea can be realized in practice.
Realization within project boundaries represents the most concrete perspective on BwN. The definition of the project boundaries is of crucial importance since this defines the domain in which procurement and contracts have to be organized. So grip is needed on how project boundaries are changed by BwN and procurement and contract need to be organized accordingly.
Adaptive management (AM) is a structured, iterative process of robust decision making in the face of uncertainty, with the aim to reduce uncertainty over time via system monitoring. In this way, decision making simultaneously meets one or more management objectives and, either passively or actively, accrues information needed to improve future management. Adaptive management is a tool which should be used not only to change a system, but also to learn about the system as is (Holling 1978). Because adaptive management is based on a learning process, it improves management outcomes in the long run. The challenge of the adaptive management approach lies in finding the correct balance between gaining knowledge to improve management in the future and achieving the best short term outcome based on current knowledge (Allan & Stankey 2009). (from wikipedia)
As building with nature, by definition, carries a large amount of uncertainty, it is practically impossible to manage a BwN project in a classical manner: not all development can fully be predicted and consequently a range of management options shall be available. Depending on close monitoring of actual developments, one has to decide which project- or process-intervention to apply. The Building Block Adaptive monitoring and execution of dredging operations provides guidance on how to apply this principle at ‘dredging with nature projects’.
The Guide to Adaptive Monitoring and Execution of Dredging Operations provides guidelines and key steps to stakeholders to set-up and implement an adaptive monitoring and management framework for the design of monitoring schemes, indicator selection, evaluation procedures, and reporting. The elements of the framework are built up in such a way that it allows both the adaptive execution of dredging works in vulnerable environments and the generation of new environmental impact knowledge that is needed to further lower the environmental impact of future dredging projects.