Sustainable hydraulic engineering through building with nature
Huib J. de Vriend
, Mark van Koningsveld
*, Stefan G.J. Aarninkhof
, Mindert B. de
, Martin J. Baptist
EcoShape Foundation, Burgemeester de Raadtsingel 69, 3311 JG, Dordrecht, The Netherlands
Delft University of Technology, Faculty of Civil Engineering and Geosciences, P.O. Box 5048, 2600 GA, Delft, The Netherlands
Van Oord Dredging and Marine Contractors B.V., P.O. Box 8574, 3009 AN, Rotterdam, The Netherlands
Royal Boskalis Westminster N.V., PO Box 43, 3350 AA, Papendrecht, The Netherlands
Deltares, P.O. Box 177, 2600 MH, Delft, The Netherlands
HZ University of Applied Sciences, P.O. Box 364, 4380 AJ, Vlissingen, The Netherlands
University of Twente, Water Engineering &Management, P.O. Box 217, 7500 AE, Enschede, The Netherlands
Imares, P.O. Box 167, 1790 AD, Den Burg, The Netherlands
VHL University of Applied Sciences, P.O. Box 1528, 8901 BV, Leeuwarden, The Netherlands
Available online 13 November 2014
Hydraulic engineering infrastructures are of concern to many people and are likely to interfere with the environment. Moreover, they are
supposed to keep on functioning for many years. In times of rapid societal and environmental change this implies that sustainability and
adaptability are important attributes. These are central to Building with Nature (BwN), an innovative approach to hydraulic engineering
infrastructure development and operation. Starting from the natural system and making use of nature's ecosystem services, BwN attempts to meet
society's needs for infrastructural functionality, and to create room for nature development at the same time. By including natural components in
infrastructure designs, ﬂexibility, adaptability to changing environmental conditions and extra functionalities and ecosystem services can be
achieved, often at lower costs on a life-cycle basis than ‘traditional’engineering solutions. The paper shows by a number of examples that this
requires a different way of thinking, acting and interacting.
©2014 International Association for Hydro-environment Engineering and Research, Asia Paciﬁc Division. Published by Elsevier B.V. All rights
Keywords: Building with nature; Sustainability; Infrastructure; Hydraulic engineering; Ecosystem services; Design
Present-day trends in society (urbanization of delta areas,
growing global trade and energy demand, stakeholder-
emancipation, etc.) and in the environment (reducing bio-
diversity, climate change, accelerated relative sea level rise,
etc.) put ever higher demands on engineering infrastructures.
Mono-functional solutions designed without due consideration
of the surrounding system are no longer accepted. Sustain-
ability, multi-functionality and stakeholder involvement are
required instead. This trend equally applies to hydraulic en-
gineering works and the associated water system management.
The design of hydraulic engineering projects is no longer
the exclusive domain of hydraulic engineers. Collaboration
with other disciplines, such as ecology, economy, social sci-
ences and administrative sciences is crucial to come to
acceptable solutions. The specialists involved in such design
projects must learn how to put forward their expertise in much
more complex decision making processes than before: being
right according to the laws of physics no longer guarantees
being heard in such processes. If this reality is ignored, it may
*Corresponding author. Delft University of Technology, Faculty of Civil
Engineering and Geosciences, P.O. Box 5048, 2600 GA, Delft, The
E-mail address: M.vanKoningsveld@tudelft.nl (M. van Koningsveld).
Available online at www.sciencedirect.com
Journal of Hydro-environment Research 9 (2015) 159e171
1570-6443/©2014 International Association for Hydro-environment Engineering and Research, Asia Paciﬁc Division. Published by Elsevier B.V. All rights reserved.
lead to long and costly delays of projects, as stakeholders and
other interested parties are becoming ever more proﬁcient in
using the legal opportunities to oppose developments and have
decisions postponed. In the Netherlands the court-cases that
delayed the realisation of the extension of the Rotterdam
harbour taught an expensive lesson, keeping the investments in
the initiation, planning and design phases of the project
without any return for a long time.
This and other experiences triggered the awareness that
projects should be developed differently, with nature and
stakeholder interests incorporated right from the start. In other
words: from a reactive approach, minimizing and mitigating
the impacts of a set design, to a pro-active one, optimizing on
all functions and ecosystem services. Although in principle
the concept of Building with Nature (BwN) is broader than
hydraulic engineering, we will focus here on water-related
projects. This paper, which is an extension of De Vriend
(2013), discusses the project development steps as they have
been suggested by the BwN innovation programme and il-
lustrates their use by describing a number of hydraulic
engineering projects in which the concept has been tested and
some other examples where successful application is to be
2. The building with nature (BwN) concept
2.1. General principles
Building with Nature (BwN) is about meeting society's
infrastructural demands by starting from the functioning of
the natural and societal systems in which this infrastructure
systems, but also to make optimum use of them and at the
same time create new opportunities for them. This approach
is in line with the need to ﬁnd different ways of operation
and it requires a different way of thinking, acting and
interacting (De Vriend and Van Koningsveld, 2012; De
Vriend et al., 2014).
Thinking does not start from a certain design concept
focussing on the primary function, but rather from the natural
system, its dynamics, functions and services, and from the
vested interests of stakeholders. Within this context, one
seeks optimal solutions for the desired infrastructural
The project development process requires different acting,
because it is more collaborative and extends beyond the de-
livery of the engineering object. The natural components
embedded in the project will take time to develop afterwards,
and one has to make sure they function as expected. Post-
delivery monitoring and projections into the future are an in-
tegral part of the project. This also creates opportunities to
learn a lot more from these projects than from traditional ones
(see also Garel et al., 2014).
BwN project development is a matter of co-creation be-
tween experts from different disciplines, problem owners and
stakeholders (e.g., Temmerman et al., 2013). This requires a
different attitude of all parties involved and different ways of
interaction, in interdisciplinary collaborative settings rather
than each actor taking away his task and executing it in
2.2. Design steps
Project development, albeititeratively, generally goes through
a number of consecutive phases. The BwN innovation pro-
gramme distinguished ‘initiation’, ‘planning and design’,‘con-
struction’and ‘operation and maintenance’. BwN solutions may
be introduced in each project phase in the form of ecologically
preferable and more sustainable approaches. Although there is
room for improvement in any phase, the earlier the approach is
embraced in the project development process, the greater is its
An important starting point for any development should be
the environment at hand. A key characteristic that distin-
guishes a BwN design from other integrated approaches is the
proactive utilization and/or provision of ecosystem services as
part of the engineering solution. The following design steps
were developed, tested and supported by scientiﬁc knowledge
in the BwN innovation programme (De Vriend and Van
Koningsveld, 2012; EcoShape, 2012):
Step 1: Understand the system (including ecosystem ser-
vices, values and interests).
eThe system to be considered depends on the project
objectives. The project objectives are inﬂuenced by
the system (problems, opportunities)
eInformation about the system at hand can/should be
derived from various sources (historic, academic,
eLook for user functions and eco-system services
beyond those relevant for the primary objective
Step 2: Identify realistic alternatives that use and/or pro-
vide ecosystem services.
eTake an inverted perspective and turn traditional
reactive perspectives into proactive ones utilizing
and/or providing ecosystem services
eInvolve academic experts, ﬁeld practitioners, commu-
nity members, business owners, decision makers and
other stakeholders in the formulation of alternatives
Step 3: Evaluate the qualities of each alternative and
preselect an integral solution.
eMore value does not necessarily imply higher con-
eDare to embrace innovative ideas, test them and show
how they work out in practical examples
ePerform a cost-beneﬁt analysis including valuation of
eInvolve stakeholders in the valuation and selection
160 H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
Step 4: Fine-tune the selected solution (practical re-
strictions and the governance context).
eConsider the conditions/restrictions provided by the
eImplementation of solutions requires involvement of
a network of actors and stakeholders
Step 5: Prepare the solution for implementation in the next
eMake essential elements of the solution explicit to
facilitate uptake in the next phase (appropriate level
of detail varies per phase)
ePrepare an appropriate request for proposals, terms of
reference or contract (permitting)
eOrganise required funding (multi-source)
ePrepare risk analysis and contingency plans
Fundamental to the above design steps is a thorough
knowledge of how the natural system functions and a correct
interpretation of the signals to be read from its behaviour. The
latter may indicate in what direction the system is evolving, how
best to integrate the desired infrastructure into it and how to
make use of the ecosystem services available. They may also
provide an early warning of adverse developments, or indicate
an increased sensitivity to natural hazards. Investing in
increased understanding of the natural system and its inherent
variability does not only pay off to the realisation of the project
at hand, but also to the system's overall management.
2.3. Spectrum of applicability
What kind of BwN solution may be applied in a given
situation, be it coastal or riverine, sandy or muddy or
dominated by living components, is governed by the ambient
physical system. Practical experience has shown that four
parameters span up a range of potential applications (see
Fig. 1): bed slope, hydrodynamic energy, salinity and geo-
climatic region (e.g., temperate or tropical).
2.3.1. Flat slopes
In low-slope environments generic BwN solutions can be
completely sediment-based. This is true for both saline and
fresh water systems. Differentiating is possible according to
energy levels. High-energy tidal environments favour designs
that are wide and contain a large volume of sediment (kilo-
metres scale) in order to produce equilibrium shorelines and
slopes, and enough bulk volume to withstand extreme condi-
tions (for example parts of the Dutch coastline with beaches
and dunes). Where these highly energy-exposed systems are
typically low in biomass, the low-energy sheltered environ-
ments, saline or fresh, allow soft solutions with high biomass,
lower width (hundreds of metres) and with tendencies to
accrete cohesive sediment. This often results in a mix of sand
and mud, stabilized by (root systems of) vegetation cover.
2.3.2. Moderate slopes
As the bed slope increases, the width available for a soft
foreshore in the wave impact zone is reduced. To maintain
safety against ﬂooding, for example, hybrid solutions are
required, such as a ‘stable sediment foreshore with hard dike’
combination. Wave reduction on the foreshore enables dikes to
be lower and softer (e.g., grass-clay cover) than traditional
engineering designs. The foreshores in these solutions can
typically be stabilized through vegetation and/or reef-
structures (e.g., a ‘sediment nourishment-wave-reducing
Fig. 1. Range of potential BwN applications along the main axes of given bed slope and hydrodynamic energy. Of course factors like salinity and geo-climatic
region also determine potential solutions.
161H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
ﬂoodplain forest-dike’combination in fresh water, or a sedi-
ment nourishment-stabilizing and wave reducing oyster reef-
mangrove-saltmarsh-dike systems in saline water). The se-
lection of the living components of the application is obvi-
ously dependent on the prevailing geo-climatic system
relevant for the case.
2.3.3. Steep slopes
As the bed slope increases further, hard solutions may
eventually prevail as most suitable solution. It is possible,
however, to introduce ecological enhancements on hard solu-
tions, in order to increase habitat diversity, biodiversity or
productivity of the structures. This could result in interesting
combinations of safety, economic and natural winewin
The following sections describe examples for a number of
distinct environments. We will indicate what role Design Step
1, reading (or not reading) the natural system, has played. For
each environment a distinct example is described, followed by
a brief analysis of the potential for more general application.
3. BwN in riverine environments
3.1. Example: room for the river
Floodplains of lowland rivers are very attractive areas for
development. This explains why in the past centuries, man has
encroached on these rivers and deprived them from large parts
of their ﬂoodplains (Fig. 2). As a consequence of the reduced
storage capacity, ﬂood waves in these rivers become higher
and proceed faster (Fig. 3, showing the same ﬂoodwave in the
Upper Rhine with an old and a recent river geometry), thus
increasing the hydrodynamic load on the ﬂood defences and
reducing the lead time for precautionary measures such as
The traditional response to these trends is to raise and
strengthen the embankments. This is basically a reactive
approach, as it does not remove the cause of the problem, viz.
the lack of storage capacity.
In recent years, governments and managers of various
rivers around the world have recognized this and have started
proactive ﬂoodplain restoration projects, sometimes primarily
driven by the need for ﬂood alleviation, in other cases by the
wish to restore nature or both (for instance, see Room for the
River (2012) for the Dutch Rhine branches, or Mississippi
(2013),orSchneider (2007) for the Danube).
In case of the Rhine and Meuse rivers in the Netherlands,
extensive schemes have been developed to reconnect removed
ﬂoodplain area to the river, thus restoring storage capacity.
Part of the returned ﬂoodplain area was made available to
nature development, provided that this did not unacceptably
reduce the river's ﬂood conveyance capacity. The strategy of
cyclic ﬂoodplain rejuvenation was developed to solve the
dilemma between ﬂood protection and nature rehabilitation
(Baptist et al., 2004).
Clearly, the signals of nature (like in Fig. 3) have been read
and understood in this case. It is also an example of thinking,
acting and interacting differently. Thinking differently,
because this goes against the traditional reactive approach
(acting after a problem has become manifest). Acting differ-
ently, because different measures are taken, such as ﬂoodplain
lowering, side channel excavation and dike displacement. And
interacting differently, because other parties (e.g., Non
Governmental Organisations (NGOs), terrain managers, rec-
reation organisations, inhabitants) are actively involved in
decision making on these projects.
3.2. More general applicability
Flood alleviation and nature restoration are not the only
river issues. Dam building, excessive water offtake, sand
mining and normalisation are activities that profoundly inﬂu-
ence river behaviour and invoke a variety of problems. Im-
mediate effects concern the ﬂow regime and the sediment
transport capacity, but in the longer run the large-scale
morphology is affected. Especially changes of the
Fig. 2. Urban encroachment on the Rhine branches near the city of Arnhem,
NL, between 1830 (top) and 2000 (bottom) (from: Silva et al., 2001). The pink
colour indicates urban area, light green the ﬂood plain and blue the main
channel. (For interpretation of the references to colour in this ﬁgure legend, the
reader is referred to the web version of this article.)
162 H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
longitudinal slope can have severe consequences. The river
may incise, which leads to erosion and groundwater level
drawdown, e.g., downstream of dams. In other cases, the river
bed builds up far above the surrounding area, leading to an
increased ﬂood risk, as has become manifest during the 2010
Indus ﬂood (Fig. 4).
Also, the cross-sectional area and the ﬂood conveyance
capacity can be severely reduced, which further enhances the
ﬂood risk. An example of the latter is the Lower Yellow River
near Huayankou, China (Fig. 5), where a peak discharge of
/s in 1996 gave about the same peak water level as a
peak discharge of 22.300 m
/s in 1958.
In order to deal with these problems, the river has to be read
in terms of ﬂow discharge, sediment transport and (large-
scale) morphological behaviour. Water management has to be
attended with corresponding sediment management in order to
avoid problems as described above. Being part and parcel of
the river bed, the ﬂoodplains also need to be managed care-
fully, as they will play an important role in storing and
conveying ﬂood waters, whereas in the meantime they may
support a valuable ecosystem and/or important economic ac-
tivities such as agriculture.
The managers of the Yellow River have understood this, in
that they noted that heavily sediment-laden ﬂoods tend to
scour the river bed (Fig. 6). After the construction of the
Xiaolangdi Dam, they ﬂush the river from time to time by
creating so-called man-made ﬂoods. Through joint operation
of three consecutive reservoirs, they create a ﬂood wave and at
the same time release large amounts of sediment from the
reservoirs (Fig. 7). The resulting highly concentrated ﬂow
scours the river bed over a large distance, thus restoring the
river's conveyance capacity for natural ﬂoods.
4. BwN in sandy shore environments
4.1. Example: the Delﬂand Sand Engine
Since the 1990s, the Holland coast, an exposed sandy
dune coast bordering the North Sea, is maintained by nour-
ishing it with sand taken from offshore. In principle, this is a
nature-friendly and sustainable way of coastal maintenance,
even in times of sea level rise. Yet, present-day practice is
Fig. 4. Landscape proﬁles across the Indus, Pakistan, and the avulsions during
the 2010 ﬂood (from: Syvitski and Brakenridge, 2013).
Fig. 5. Evolution of depth and cross-sectional area of the Lower Yellow River
at Huayankou Station, China; the stages refer to different regimes of dam
operation (derived from: Ma et al., 2012).
Fig. 6. Cross-section of the Lower Yellow River at Huayankou, China, before
and after the 1973 ﬂood (from: IRTCES, 2005).
Fig. 3. Computed ﬂood wave in the Upper Rhine, Germany, with the river
geometry of 1882/1883 and 1995 respectively (adapted from: ICHR, 1993).
The horizontal axis indicates time in days.
163H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
reactive: whenever the coastline threatens to withdraw
behind a given reference line, a relatively small amount of
sand (up to a few million m
upper shoreface. A typical return period of these nourish-
ments is some ﬁve years. This practice has a few disadvan-
tages. Every nourishment buries part of the marine
ecosystem, the recovery of which takes several years. As a
consequence, ﬁve-yearly nourishments tend to bring the
ecosystem into a more or less permanent state of disturbance
(Baptist et al., 2008). Moreover, nourishing only the upper
part of the shoreface tends to lead to over-steepening of the
coastal proﬁle, hence to more offshore-directed sediment
transport and, in the long run, the necessity to nourish ever
more frequently. Or, otherwise, this over-steepening leads to
an increased susceptibility to coastal erosion when the
nourishments stop (Stive et al., 1991).
In 2011, the Province of Zuid-Holland and Rijkswaterstaat
started an experiment to ﬁnd out whether nourishing a large
amount at once is a better solution. Between February and July
2011, 21.5 million m
of sand was deposited on the shoreface
in front of the Delﬂand coast, between The Hague and Rot-
terdam (Fig. 8). The idea of this mega-nourishment is that in
the coming decades the sand will be distributed by waves,
currents and wind over this 18 km long coastal reach, thus
feeding the lower shoreface, as well as the subaqueous and
subaerial beach and the dune area. Once the nourishment has
been placed, the ecosystem is expected to suffer less than in
the case of repeated small nourishments. The experiment
should provide an answer to the question to what extent the
disadvantage of the earlier investment (the costs of the nour-
ishment) will be outweighed by additional beneﬁts, such as
less harm done to or even new opportunities for the ecosystem,
recreational opportunities (for instance, the Sand Engine has
soon become a favourite site for kite surfers, which brings
proﬁt to the local economy), a wider dune area (i.e. also a
larger freshwater reserve) and a better adaptation of the coastal
defence system to sea level rise.
A recent morphological survey showed that in the two years
since construction about 2 million m
of sand (i.e. some 10%
of the total volume) have moved, of which 0.6 million m
stayed on the Sand Engine, 0.9 million m
in its immediate
vicinity and 0.5 million m
have been transported outside the
survey area, i.e. to the dune area or to deeper water, which
agrees well with earlier model predictions (e.g., Stive et al.,
2013a, b). As coastline processes tend to slow down as they
approach the equilibrium state (in this case a straight coast-
line), these results suggest that a lifetime estimate of 20 years
is probably conservative.
Ecologically speaking, the Sand Engine exhibits interesting
developments (Linnartz, 2013), e.g., juvenile dune formation
and establishment of pilot vegetation, including rare species. It
also turns out to be a favourite resting area for birds and seals,
and the lagoon is full of juvenile ﬁsh. Whether the Sand En-
gine approach is economically attractive remains to be seen.
First calculations (Stive, 2013, private communication) sug-
gest that, even if only the costs of sand reaching the shore are
considered, the economy of scale and the presence of heavy
equipment in the vicinity (building Maasvlakte II, a seaward
extension of Rotterdam harbour) outweigh the effect of dis-
counting the early investment.
Fig. 8. Upper panel: The Delﬂand Sand Engine shortly after placement (July
2011). Lower panel: The Sand Engine has evolved into an almost symmetrical
salient (October 2013). source: https://beeldbank.rws.nl, Rijkswaterstaat/Joop
Fig. 7. Man-made ﬂood generation in the Yellow River at Xiaolangdi, China.
The highly sediment-laden ﬂow scours the river channel over a long distance
164 H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
4.2. More general applicability
The concept and the way of thinking underlying the Sand
Engine are generic for eroding sandy coasts, but its design
cannot simply be copied to other locations. The design should
rather comply with the local situation and the local dynamics.
Moreover, not only sea level rise may be the cause of coastal
erosion, but also a lack of sediment supply, e.g., due to damming
or sand mining in rivers feeding the coast, or interruption of the
longshore drift by engineering structures, or removal of stabi-
lizing vegetation (mangrove). This may lead to different designs
and different ways of construction and operation.
Stable sandy coasts usually exist thanks to a sediment
source, often a river or an eroding cliff. If this source is
reduced, for instance by damming upstream, or by ﬁxation of
the cliff, the coast will tend to erode. One example is the
Yellow River Delta, where the sediment source was ﬁrst ﬁxed
in place by embanking the river, and subsequently reduced by
a dam-induced change of the discharge regime (Fig. 9), fol-
lowed by a coarsening of the bed, both of which bring down
the river sediment transport capacity. As a consequence, the
past rapid build-out of the delta ﬁrst concentrated around one
location (the ﬁxed river mouth) and later dropped dramati-
cally, came to a standstill and even turned into erosion (e.g.,
NASA, 2013). Other parts of the delta coast were cut off from
their sediment source and eroded rapidly, in some places over
a large distance (kilometres). Coastal nourishment and ﬁxation
by vegetation may be an option here, but this requires thor-
ough reading of the system, i.e. consideration of the local
situation, with very ﬁne and easily erodible sediment and a
high groundwater salinity.
Other examples of dramatic coastal erosion can be found on
tropical mud coasts where the natural mangrove protection has
been removed, for instance in order to build ﬁsh ponds in the
coastal zone. Fig. 10 shows an example of the north coast of
Java near Demak, Indonesia, where heavy erosion started after
the ﬁsh ponds, which covered the entire coastal zone, had been
abandoned. Given the many ecosystem services provided by
mangrove forests, their restoration seems attractive here. Many
failures of mangrove replantation schemes (e.g., Primavera
and Esteban (2008); Lewis III (2009)), however, have shown
that this is nowhere near a trivial task. For the replanted sys-
tem to survive it is crucial to have the right combination of
coastal morphology (with a concave downward proﬁle), wave
conditions, tidal motion, fresh groundwater availability, sedi-
ment supply and plant species (Winterwerp et al., 2013). This
is another example of the necessity to read the local natural
system, as it is now and as it has been in the past, and to adapt
the design accordingly.
5. BwN in lake shore environments
5.1. Example: Lake IJssel Shore nourishment
In 2008, a State Committee advised the Netherlands gov-
ernment on ﬂood safety and freshwater availability under a
Fig. 10. Coastal degradation between 2003 and 2013 near Demak, Indonesia
(courtesy: J.C. Winterwerp).
Fig. 9. Evolution of the annual runoff (upper panel: after Grafton et al., 2013)
and sediment discharge (lower panel: after Wang et al., 2011) at Lijin Hy-
drological Station, Lower Yellow River, China. The dashed lines represent the
linear trend through the available data points.
165H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
scenario of accelerated sea level rise (Delta Committee, 2008).
Part of this advice concerned the Lake IJssel, the inland
freshwater lake that was created by closing off the Zuiderzee
in 1932. The Committee advised to gradually raise the lake
level along with the rising sea level, so that one could keep on
discharging surplus water by free outﬂow. Although in the
meantime this idea has been abandoned in favour of increased
pumping capacity, the suggestion has raised the awareness of
terrain managers of the former coastal saltmarshes, now
valuable freshwater wetlands that protect the dikes behind
them against wave attack. They realized that these wetlands
require maintenance, in order to be ready for stronger varia-
tions of the lake level, to combat ongoing subsidence and to
enable the vegetation to rejuvenate.
Although southwesterly winds have a considerable fetch
here and local waves and water level set-up can be signiﬁcant,
the lake shores can be categorized as low-dynamic. This
means that nourishing these shores would lead to a slow
supply of sediment to the coastline, exactly what is needed to
maintain these wetlands without destroying their vegetation.
In 2011, and 2012, respectively, small-scale shoreface
nourishments were performed at two locations (Wor-
kumerwaard and Oudemirdumerklif) on the northwesterly
shore of the lake. Figs. 11 and 12 show the development of the
Workumerwaard nourishment, which involved some
of sand. Although after the ﬁrst year the nourished
sand has hardly reached the shoreline, morphodynamic ac-
tivity is clearly present, as the original hump has dispersed into
a number of sand waves which are in line with the natural bed
topography. Recent visual observations suggest that the sand is
moving northward, along with the net longshore drift, and is
trapped in the lee of the pole screen.
At this location, reading nature boiled down to (1) realizing
that the wetlands had to remain in open connection with the
lake in order to keep their unique character, (2) concluding
that the wetland vegetation had reached a climax stage and
would need rejuvenation in order to restore diversity and vi-
tality, (3) interpreting the natural sand waves on the sub-
aqueous shore as a signal of morphodynamic activity that
might bring nourished sediment onshore, and (4) realizing that
the prevailing longshore drift will tend to carry the sand
further north, so that a sediment retaining structure is needed.
Thinking differently means here the recognition that the
wetlands are not only valuable from an ecological and recre-
ational point of view, but also have the capability -when
properly managed-to keep the dikes behind them from being
strengthened. People acted differently here because they
decided not to strengthen the dike (and probably let the wet-
lands get drowned) or build a protection levee along the shore
(and probably destroy the wetlands'character), but to opt for
slow sand nourishment. And they interacted differently
because this project was developed by experts from various
disciplines, together with a variety of stakeholders and the
local administration. At another location, Hindeloopen, this
stakeholder involvement even led to a drastic change of plans,
to the effect that for the time being no nourishment will be
made, at all.
5.2. More general applicability
The example above concerns an existing, more or less
natural foreshore. Such features are not always available in
lakes. Lakes in soft sediment environments like deltas tend to
expand in the direction of the prevailing winds. As this process
continues, they become more susceptible to wind-induced
water level variations, especially at the eroding end. Also,
ﬂoods in adjacent rivers may cause ﬂood problems. Tai Lake,
near Shanghai in China, for instance, lies close to the Yangtze
River and well below typical ﬂood levels in that river (Gong
and Lin, 2009).
This shows that ﬂood protection is an issue for the riparian
areas of such delta lakes. If the water from the lake has to be
kept out, dike building is an obvious way to achieve this. If the
subsoil is soft, however, like in the case of a dike built on peat,
the soil's carrying capacity may limit the dike height. Also,
subsoils with sandy streaks, e.g., remainders of old streams
and creeks, may give rise to piping, i.e. the formation of
Fig. 12. Bed topography after 1 year; warmer colours represent higher bed
levels (courtesy: A. Wiersma); note the pole screen screen is not shown in this
picture. (For interpretation of the references to colour in this ﬁgure legend, the
reader is referred to the web version of this article.)
Fig. 11. Design of the Workumerwaard nourishment experiment (grey rect-
angle: nourishment footprint; brown line: sand retaining pole screen); the
primary ﬂood defence, a dike, lies outside the photo to the right.
166 H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
sediment conveying seepage channels which undermine the
dike (e.g., De Vries et al., 2010).
The height of a traditional dike is determined to a signiﬁ-
cant extent by wave overtopping restrictions, the width by
geomechanical stability requirements and the need to extend
the seepage length in order to prevent piping. As an alternative
to dike raising, one may consider designs that reduce the wave
attack and increase the stability and the seepage length in
another way. Depending on the local situation, a shallow
vegetated foreshore may be such an alternative (Fig. 13).
Both the shallowness of the foreshore and the vegetation on
top of it attenuate incoming waves before they reach the dike.
A clayey substrate hampers seepage, hence increases the
effective seepage length. Such foreshores can carry valuable
ecosystems that provide a large number of additional services,
such as water puriﬁcation (e.g., helophyte ﬁlters), breeding,
feeding and resting grounds for a variety of species (among
which migratory birds), carbon sequestration and biomass
production. It forms an alongshore connection between eco-
systems that were separated before and it provides space for a
variety of recreation activities.
This, too, is not a panacea. If excessive rainfall is the main
cause of ﬂooding, for instance, effective drainage is more
important than keeping the water out. And if severe algal
blooms occur (see Fig. 14) it is better to eliminate the sources
of eutrophication than to try and remove the nutrients once
they are in the system. This illustrates, once again, the
importance of reading and understanding the local
6. BwN in estuarine environments
6.1. Example: Eastern Scheldt oyster reefs
Bio-architects or ecosystem engineers are species that
modify their habitat, to their own beneﬁt and that of other
species (e.g., Bouma et al., 2009). Oysters and coral are ex-
amples, they build reefs that provide habitat to a wide range of
others species. Apart from this effect on their own habitat and
that of other species, the activities of bio-architects may have
other positive effects, such as sediment trapping and coastal
protection. This makes these species interesting from a BwN
point of view. In temperate climate zones, oyster reefs may be
used to prevent erosion and saltmarshes to trap sediment and
attenuate waves. In a tropical climate, mangrove forests, sea-
grass meadows and coral reefs, often in combination, may help
stabilizing and protecting coasts.
A set of experiments with oyster reefs for the protection of
eroding intertidal shoals was performed in the Eastern Scheldt,
the Netherlands. These shoals are consistently losing sediment
to the gullies after the construction of a storm surge barrier in
the mouth of the estuary and a number of auxiliary works have
reduced the tidal amplitude by about 20% and the tidal prism
in the mouth by some 25% (e.g., Eelkema, 2013). This loss of
intertidal area, together with the ﬂattening of the shoals by
wave action, is detrimental to the populations of residential
and migratory shorebirds or waders, which use this area for
feeding and resting.
One way to interrupt the sediment transport from the shoals
into the gullies would be to create oyster reefs on the shoal
edges. This raises the question how to establish live oyster
reefs at the right locations. Since oyster shells are the perfect
substrate to settle on for juvenile oysters (spat), gabions (iron
wire cages) ﬁlled with oyster shells (Fig. 15) were placed on
the shoal edges at various locations, ﬁrst in small patches, later
on in larger strips (typically 10 m wide and a few hundreds of
metres long). After a few years (Fig. 16) we can conclude that
this approach can work, provided that the locations of the
gabions be carefully selected (Ysebaert et al., 2012).
Fig. 14. Some lakes have severe water quality problems, such as algal blooms
(photo from Tai Lake, China).
Fig. 13. Artist impression of a lacustrine shallow foreshore in front of a
traditional dike; the dark brown material is clayey, in order to prevent seepage;
the light brown material is sandy, as a buffer against erosion (courtesy: Bureau
167H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
In this case, the natural processes were carefully analysed
and interpreted. The reduction of the tidal motion has weak-
ened the hydrodynamic forces building up the shoals and has
given room to the erosive action of locally generated waves.
This explains why the shoals tend to be ‘shaved’off almost
horizontally. The sediment eroded from the tops of the ﬂats
ends up in the nearest deeper water, so on the subtidal banks of
the gullies. This means that there are no mechanisms to carry
this sediment further away, and that if one would manage to
keep the sediment on top of the shoals it would probably stay
there. This explains why oyster reefs on the shoal edges may
help. The ecosystem was also read carefully: oyster spat
settling preferentially on oyster shells, oyster reefs being more
resistant than mussel banks, for instance, because oysters glue
their shells together and mussels use byssus threads to connect
to each other. Environmental conditions necessary for a live
oyster reef to establish and survive (wave exposure, nutrient
ﬂows, risk of sand burial, risk of macroalgae preventing spat
settlement, ect.) were also carefully considered.
Here, too, thinking, acting and interacting were unusual.
Even though blocking shoal erosion may be considered as an
end-of-pipe measure (the real causes of the erosion are not
removed), using biological elements to achieve an engineering
goal, viz. erosion prevention, is a change in thinking.
Moreover, if the reefs are viable in the long run, they will also
be able to adapt themselves to a changing sea level. This is a
capability beyond what traditional engineering structures can
deliver. The design constitutes a different way of acting. The
placement of the gabions is hardly intrusive (no digging,
mostly indigenous components). The ironwire gabions will
corrode quickly in this aggressive environment, so after some
time the system relies on the ability of the oyster reef to
sustain and rejuvenate itself. This is different from traditional
engineering, with its focus on durable structures.
Finally, different experts (apart from technicians also
physicists, ecologists and social scientists) and different
stakeholders (apart from Rijkswaterstaat also NGOs, ﬁsher-
men, etc.) were involved in the decision making process.
Moreover, coastal defence experts keenly followed the ex-
periments, because of the potential positive effects on the
wave-attenuating and dike-stabilizing function of shallow
6.2. More general applicability
Intertidal areas are found in estuaries around the world and
usually they are of great value, environmentally, but also from
an economic point of view (ﬂood protection, land reclamation,
aquaculture, etc.). Many of these estuaries, however, suffer
from a reduced sediment supply, due to river damming, sand
mining and excessive water offtake from the river that de-
bouches through the estuary. The Yangtze River, with its many
thousands of dams (Yang et al., 2011), is just one example, but
there are many others. Many estuaries also have been deprived
from their inter- and supra-tidal storage area, with severe
consequences, not only for extreme surge levels and ﬂood
risks (Temmerman et al., 2013), but also for suspended sedi-
ment import and environmental quality (Winterwerp et al.,
2013). Before the sediment supply to the Yangtze Estuary
was drastically reduced, the islands and shoals in the Yangtze
Estuary would build out rapidly, enabling consecutive recla-
mations of large pieces of land to meet the urgent need for
space in this part of China (Fig. 17).
At present, the shoals in the estuary tend to erode. An early
indicator of this tendency is the cross-shore proﬁle, which has
Fig. 16. Successful oyster reef after one year (courtesy: T. Ysebaert).
Fig. 17. Consecutive reclamations of accreted marsh on East Chongming Is-
land, Yangtze Estuary, China.
Fig. 15. Placement of gabions with oyster shells (courtesy: T. Ysebaert).
168 H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
turned in recent years from concave upward to convex upward
(Yang et al., 2011); also see Fig. 18. A dense and vital vege-
tation canope (in this case a combination of endemic Scirpus
and imported Spartina) can slow down this process (Yang
et al., 2008), but cannot remove the principal cause, viz. the
lack of sediment supply from upstream. Whether ecosystem-
engineers like oysters or mussels can provide a solution here
remains to be seen, given the intense ﬁsheries activity in this
area. Moreover, the need for space creates pressure from so-
ciety to reclaim more land, be it not at East Chongming Island,
then in other parts of the estuary, and be it not above Mean Sea
Level (MSL), then below it (cf. Chen et al., 2008). The latter
requires dike construction below MSL, which is bound to
aggravate erosion in front of the dike. Clearly, not only the
natural system needs to be read to ﬁnd an adequate solution,
but also the socio-economic system.
7. Dredging-induced turbidity
Dredging, instrumental to many hydraulic engineering
works, often leads to environmental concerns because of the
turbidity it induces. This may harm valuable ecosystems, such
as coral reefs in tropical areas, or shellﬁsh reefs in moderate
climate zones. So far, regulations used to focus on the sedi-
ment ﬂux released from the dredging equipment, rather than
on the actual impact on the ecosystem. BwN proposes to
reverse the order, starting from the ecosystem's vulnerability
and working one's way back to the dredger. This enables
optimization of the dredging operation.
A useful tool to assess ecosystem vulnerability are species
response trajectories for the key species (Fig. 19), describing
the abundance of a species as a function of stress level and
exposure duration. Given a certain ecosystem and the hydro-
dynamic and sedimentologic conditions in its surroundings,
one can work out the maximum allowable sediment release at
every location and every point in time using a sediment
dispersion model. Fig. 20 shows a screen shot of a dredging
support tool in which this has been implemented. The green
dots indicate locations where exposure to turbidity is pre-
dicted to remain below predeﬁned threshold levels. The tools
supports planning the dredging operation such that this is
8.1. Translation to practice
The above examples are just a selection of applications and
application potential of the BwN-principles and design steps.
Together they cover the range of applications outlined in
Section 2. Many more examples are described by Waterman
(2008), on the EcoShape website http://www.ecoshape.nl,in
the BwN-booklet (De Vriend and Van Koningsveld, 2012) and
in the BwN-design guideline (EcoShape, 2012). For new in-
sights acquired from experiments and pilot projects to be used
Fig. 19. Species response trajectory for tropical seagrass (source: EcoShape,
Fig. 18. Cross-shore proﬁle evolution at East Chongming Island, China (from:
Yang et al., 2011).
Fig. 20. Screenshot of a dredging support system applied to a dredging
operation near Singapore.
169H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
in practice, translation to practical usability is crucial. This
goes far beyond writing papers in scientiﬁc or professional
journals or presenting material at conferences and workshops.
It requires a complete reworking of the material into guide-
lines for practical use, user-friendly tools, tutorials, low-
threshold access to data and models, examples of earlier
projects, ready-to-use building blocks, etc.
In the Dutch BwN innovation program (2008e2012) a sig-
niﬁcant part of the effort was spent to this reworking activity. It
has led to a wiki-like environment, accessible via the EcoShape-
website mentioned above, which includes all these elements and
contains a wealth of information. Based on feedback from users
and continued input from ongoing and new projects and ex-
periments, this wiki is to be improved further.
8.2. Dissemination and outreach
The concept underlying BwN has been taken up by various
other organisations. In the United Kingdom (UK), managed
realignment, i.e. realignment of ﬂood defences in such a way
that there is more room for ﬂood water storage and at the same
time for nature, is basically a form of building with nature
(e.g., Garbutt et al., 2006). The World Association for
Waterborne Transport Infrastructure (PIANC) supports a
similar movement named ‘Working with Nature’(see PIANC,
2013). The US Army Corps of Engineers (USACE) promotes
the use of dredged material to create room for nature areas in
the coastal zone: ‘Engineering with Nature’(Bridges et al.,
2008). Also in Belgium, there are plans for extensive multi-
functional ‘soft engineering’in front of the North Sea coast
of Flanders (see Vlaamse Baaien, 2013). Finally, the European
Commission (EC) has included the concept in its Green
Infrastructure Strategy (see European Commission, 2013).
Yet, mainstreaming the approach in practical hydraulic
engineering projects still meets several obstacles. Some of
these have to do with conservatism and risk-aversion, but
others are associated with the economic point of view and the
prevailing legislation. When considering only the short-term
economics of adding sand to the backbeach and the dune
area, the Delﬂand Sand Engine may be economically subop-
timal, as nourishing small amounts whenever necessary may
well be cheaper. But from a longer-term and multi-functional
perspective, mega-nourishments may just as well be
economically attractive. Moreover, BwN requires investing
time and money into knowing how the natural system
-including the ecosystem- functions, an investment that pays
off later, but possibly not as directly as a traditional hard en-
If, like in the European Union (EU), legislation forces all
government-funded infrastructural projects to be internation-
ally tendered, innovative pre-competitive experiments and
pilot projects tend to be out-competed by traditional ap-
proaches of which the uncertainties are perceived to be less.
Another example of the effect of prevailing rules concerns the
assessment of the ﬂood defence systems in the Netherlands,
which excludes shallow foreshores. This renders shallow-
foreshore solutions for ﬂood defences useless.
The existing experiments, pilot projects and showcases
show that the BwN approach works, provided that one thinks,
acts and interacts accordingly. Knowing the natural biotic and
abiotic environment in which an infrastructural functionality is
to be realized, as well as knowing how the relevant social
system functions, is a necessity for this approach to be suc-
cessful. This applies in Europe, as well as in other countries
around the world, as shown by the examples in Asia and the
United States of America (USA). Initiatives in different
countries and international organisations are merging into an
international movement, but mainstreaming the approach in
hydraulic engineering practice still meets a number of obsta-
cles. They need to be overcome in the next few years in order
to have this approach broadly implemented.
Except for Room for the River, the examples described
herein were part of the 2008e2012 BwN innovation pro-
gramme, which was funded jointly by the partners of the
EcoShape consortium, the Netherlands government, the Eu-
ropean Fund for Regional Development and the Municipality
of Dordrecht. The authors are indebted to the many colleagues
who have realized these projects.
Baptist, M.J., Penning, W.E., Duel, H., Smits, A.J.M., Geerling, G.W., Van der
Lee, G.E.M., Van Alphen, J.S.L., 2004. Assessment of the effects of cyclic
ﬂoodplain rejuvenation on ﬂood levels and biodiversity along the rhine
river. River Res. Appl. 20 (3), 285e297. http://dx.doi.org/10.1002/rra.778.
Baptist, M.J., Tamis, J.E., Borsje, B.W., Van der Werf, J.J., 2008. Review of the
Geomorphological, Benthic Ecological and Biogeomorphological Effects of
Nourishments on the Shoreface and Surf Zone of the Dutch Coast, p. 68.
Technical Report. Wageningen IMARES C113/8, Deltares Z4582.50.
Bouma, T.J., Olenin, S., Reise, K., Ysebaert, T., 2009. Ecosystem engineering
and biodiversity in coastal sediments: posing hypotheses. Helgol. Mar.
Res. 63 (1), 95e106. http://dx.doi.org/10.1007/s10152-009-0146-y.
Bridges, T.S., Ells, S., Hayes, D., Mount, D., Nadeau, S.C., Palermo, M.R.,
Patmont, C., Schroeder, P., 2008. The Four Rs of Environmental Dredging:
Resuspension, Release, Residual, and Risk. Technical Report. US Army
Corps of Engineers.
Chen, J.Y., Cheng, H.Q., Da, Z.J., Eisma, D., 2008. Harmonious development
between utilization and protection of tidal ﬂat and wetland ea case study
in the Shanghai area. China Ocean. Eng. 22 (4), 649e662.
De Vriend, H.J., 2013. Building with Nature: towards sustainable hydraulic
engineering. In: Proceedings 2013 IAHR World Congress, Chengdu,
China, ISBN 978-789414-588-8. Invited paper A12217.
De Vriend, H.J., Van Koningsveld, M., 2012. Building with Nature: Thinking,
Acting and Interacting Differently. In: EcoShape, Building with Nature.
Dordrecht, the Netherlands. http://ecoshape.nl/ﬁles/paginas/ECOSHAPE_
De Vriend, H.J., Van Koningsveld, M., Aarninkhof, S.G.J., 2014. ‘Building
with Nature’: the new Dutch approach to coastal and river works. Proc.
ICE eCiv. Eng. 167 (1), 18e24. http://dx.doi.org/10.1680/cien.13.00003.
De Vries, G., Koelewijn, A., Hopman, V., 2010. IJkdijk full scale Under-
seepage erosion (Piping) test: evaluation of innovative sensor technology.
Scour Eros. 649e657. http://dx.doi.org/10.1061/41147(392)63.
Delta Committee, 2008. Working Together with Water; a Living Land Builds
for its Future. Hollandia Printing, The Hague, p. 134. Technical Report.
170 H.J. de Vriend et al. / Journal of Hydro-environment Research 9 (2015) 159e171
Delta Committee. URL. http://www.deltacommissie.com/doc/deltareport_
EcoShape, 2012. The Building with Nature Design Guideline. http://ecoshape.
nl/en_GB/wiki-guideline.html (last visited January 11, 2014).
Eelkema, M., 2013. Eastern Scheldt Inlet Morphodynamics (Ph.D thesis).
Delft University of Technology, ISBN 978-90-9027347-1, p. 145.
European Commission, 2013. Green infrastructure Strategy. http://ec.europa.
eu/environment/nature/ecosystems/ (last visited January 11, 2014).
Garbutt, R.A., Reading, C.J., Wolters, M., Gray, A.J., Rothery, P., 2006.
Monitoring the development of intertidal habitats on former agricultural
land after the managed realignment of coastal defences at Tollesbury,
Essex, UK. Mar. Pollut. Bull. 53 (1e4), 155e164.
Garel, E., Camba Rey, C., Ferreira, O., Van Koningsveld, M., 2014. Appli-
cability of the “Frame of Reference”approach for environmental moni-
toring of offshore renewable energy projects. J. Environ. Manag. 141 (1),
Gong, Z., Lin, Z., 2009. Strategy of ﬂood control in Taihu Basin. In: Advances
in Water Resources and Hydraulic Engineering. Springer Berlin Heidel-
berg, pp. 1011e1016. http://dx.doi.org/10.1007/978-3-540-89465-0_177.
Grafton, R.Q., Pittock, J., Davis, R., Williams, J., Fu, G., Warburton, M.,
Udall, B., McKenzie, R., Yu, X., Che, N., Connell, D., Jiang, Q.,
Kompas, T., Lynch, A., Norris, R., Possingham, H., Quiggin, J., 2013.
Global insights into water resources, climate change and governance. Nat.
Clim. Change 3, 315e321. http://dx.doi.org/10.1038/nclimate1746.
ICHR, 1993. The Rhine under the Inﬂuence of Man - River Engineering
Works, Shipping, Water Management. Technical Report. International
Commission for the Hydrology of the Rhine, ISBN 90-70980-17-7, p. 260.
IRTCES, 2005. Case Study on the Yellow River Sedimentation. Technical
Report. International Research and Training Center on Erosion and Sedi-
mentation, Beijing, China, p. 132. http://www.irtces.org/isi/isi_document/
Lewis III, R.R., 2009. Editorial: knowledge overload, wisdom underload. Ecol.
Eng. 35 (3), 341e342. http://dx.doi.org/10.1016/j.ecoleng.2008.10.006.
Linnartz, L., 2013. The Second Year Sand Engine: Nature Development on a
Dynamic Piece of the Netherlands. Technical Report. ARK Natuur-
ontwikkeling, p. 33. http://www.dezandmotor.nl/uploads/2013/10/het-
tweede-jaar-zandmotor-een-verslag.pdf (in Dutch).
Ma, Y., Huang, H., Nanson, G.C., Li, Y., Yao, W., 2012. Channel adjustments
in response to the operation of large dams: the upper reach of the lower
yellow river. Geomorphology 147e148, 35e48. http://dx.doi.org/10.1016/
Mississippi, 2013. The Nature Conservancy. http://www.nature.org/
ﬂoodplain-restoration-in-mississippi-river-basin.xml (last visited January
NASA, 2013. Earth Observatory. http://earthobservatory.nasa.gov/Features/
WorldOfChange/yellow_river.php (last visited January 11, 2014).
PIANC, 2013. Working with nature. http://www.pianc.org/workingwithnature.
php (last visited January 11, 2014).
Primavera, J.H., Esteban, J.M.A., 2008. A review of mangrove rehabilitation in
the Philippines: successes, failures and future prospects. Wetl. Ecol.
Manag. 16 (5), 345e358. http://dx.doi.org/10.1007/s11273-008-9101-y.
Room for the River, 2012. Room for the River Programme. http://www.
programme/ (last visited January 11, 2014).
Schneider, T., 2007. The Danube restoration project between Neuburg und
(last visited January 11, 2014).
Silva, W., Klijn, F., Dijkman, J., 2001. Room for the Rhine Branches in The
Netherlands: what the Research Has Taught Us, ISBN 9036953855, p. 16.
Technical Report. Rijkswaterstaat/WLdDelft Hydraulics, report RIZA-
2001.031/WL eR 3294.
Stive, M.J.F., De Schipper, M., Ranasinghe, R., Van Thiel de Vries, J.S.M.,
2013a. The Sand Engine: a solution for the Dutch Delta in the 21st cen-
tury?. In: Proceedings 2013 IAHR World Congress, Chengdu, China, ISBN
Stive, M.J.F., De Schipper, M.A., Luijendijk, A.P., Aarninkhof, S.G.J., Van
Gelder-Maas, C., Van Thiel de Vries, J.S.M., De Vries, S., Henriquez, M.,
Marx, S., Rana, 2013b. A new alternative to saving our beaches from sea-
level rise: the sand engine. J. Coast. Res. 29 (5), 1001e1008. http://
Stive, M.J.F., Nicholls, R.J., De Vriend, H.J., 1991. Sea level rise and shore
nourishment: a discussion. Coast. Eng. 16 (1), 147e163. http://dx.doi.org/
Syvitski, J.P.M., Brakenridge, G.R., 2013. Causation and avoidance of cata-
strophic ﬂooding along the Indus River, Pakistan. GSA Today 23 (1),
Temmerman, S., Meire, P., Bouma, T., Herman, P., Ysebaert, T., De
Vriend, H.J., 2013. Ecosystem-based coastal defence in the face of global
change. Nature 504, 79e83. http://dx.doi.org/10.1038/nature12859.
Vlaamse Baaien, 2013. Vlaamse Baaien. http://www.vlaamsebaaien.com/
ﬂanders-bays-2100 (last visited January 11, 2014).
Wang, H., Saito, Y., Zhang, Y., Bi, N., Sun, X., Yang, Z., 2011. Recent changes
of sediment ﬂux to the western paciﬁc ocean from major rivers in east and
southeast asia. Earth-Science Rev. 108, 80e100.
Waterman, R.E., 2008. Integrated Coastal Policy via Building with Nature.
Opmeer Drukkerij, Den Haag, ISBN 978-90-805222-3-7, p. 449.
Winterwerp, J.C., Erftemeijer, P.L.A., Suryadiputra, N., Van Eijk, P.,
Zhang, L., 2013. Deﬁning eco-morphodynamic requirements for rehabil-
itating eroding mangrove-mud coasts. Wetlands 33 (3), 515e526. http://
Yang, S.L., Li, H., Ysebaert, T.J., Bouma, T.J., Zhang, W.X., Li, P., Li, M.,
Ding, P.X., 2008. Spatial and temporal variations in sediment grain size in
tidal wetlands, yangtze delta: on the role of physical and biotic controls.
Estuar. Coast. Shelf Sci. 77 (4), 657e671. http://dx.doi.org/10.1016/
Yang, S.L., Milliman, J.D., Li, P., Xu, K., 2011. 50,000 dams later: erosion of
the yangtze river and its delta. Glob. Planet. Change 75 (1e2), 14e20.
Ysebaert, T., Walles, B., Dorsch, C., Dijkstra, J., Troost, K., Volp, N., van
Prooijen, B., de Vries, M.B., Herman, P., Hibma, A., 2012. Ecodynamic
solutions for the protection of intertidal habitats: the use of oyster reefs. J.
Shellﬁsh Res. 31, 362.
BwN: Building with Nature;
EC: European Commission;
EU: European Union;
MSL: Mean Sea Level;
NGOs: Non Governmental Organisations;
PIANC: World Association for Waterborne Transport Infrastructure;
UK: United Kingdom;
USA: United States of America;
USACE: US Army Corps of Engineers.
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