Eco-engineering in the Soft interventions with a solid impact 2 | Rijkswaterstaat and Deltares Contents

4 | Background and cooperation

5 | Foreword and introduction

7 | Reader’s guide

10 | Building with nature in saltwater 10 | 01 Sand Engine 14 | 02 Oyster reef 16 | 03 Oesterdam

18 | Building with nature in freshwater 18 | 04 Noordwaard 20 | 05 Reed marshes 22 | 06 Foreshore levee 24 | 07 Marsh restoration 28 | 08 Soft Sand Engine

30 | Building for nature in saltwater 30 | 09 Eco-concrete 32 | 10 Tidal pools 36 | 11 Hanging structures

40 | Afterword

42 | Colophon

t Seals on a concrete jetty block covered with algae

Soft interventions with a solid impact | 03 Background and cooperation

At Rijkswaterstaat Eco-engineering is an emerging discipline in regular projects, and part of several knowledge management and innovation management activities, including the eco-engineering flood protection programme. As a major player in the field of water management Rijkswaterstaat is in a position to innovate and to create new ideas and applications by pooling knowledge together with other parties including citizens, companies, authorities and research institutes.

Rijkswaterstaat is responsible for the main waterways, water systems and road networks in the Netherlands. It faces numerous challenges posed by extreme weather conditions, an ageing infrastructure, new technologies and shrinking budgets. Rijkswaterstaat set up an innovation programme to cope with these challenges. The parties in this programme that work on eco-engineering also work on the Building with Nature innovation programme. The programme is being implemented by the business community and consists of several sub-programmes that focus on flood protection. In order to implement the programme, the parties formed a foundation called EcoShape to carry out the eco-engineering work.

Deltares has extensive expertise in eco-engineering and is involved in both innovation programmes as a knowledge partner. The Eco-engineering and Building with Nature programmes both examine how functions of ecosystems with of infrastructure can be integrated in a sustainable, climate-robust and cost-efficient manner. The parties are committed to finding solutions for hydraulic engineering infrastructure development that address the needs and wishes of all involved. Potential innovations and improvements are carefully tested in the field, enabling the parties to determine whether an idea actually delivers improvements.

4 | Rijkswaterstaat and Deltares A reciprocal relationship

In eco-engineering projects we let nature contribute to flood protection. We use the services that ecosystems provide to achieve this, such as plants that dissipate wave energy and oysters that stabilize sediment. We thus create more natural flood defences that meet the strict demands of flood protection in what one might call a soft intervention with a solid impact.

When eco-engineering concepts are and nature enhance each other in all applied, natural processes and organisms eco-engineering projects. This reciprocal support the realization and functioning of relationship has numerous advantages. the hydraulic infrastructure (‘building with New natural solutions emerge as the sea nature’). The opposite often works well level rises and other water levels gradually too, when infrastructural works are change, which could yield huge savings on adapted in such a way that they benefit the maintenance and strengthening of nature (‘building for nature’). Dunes are an flood defences. More costs can be cut example of ‘building with nature’. They because most ecosytem services provide provide flood protection by forming a several services simultaneously. Dunes, for buffer between the land and the sea, example, contribute to coastal protection, which can be optimized through optimal recreation and water purification. management strategies. Without dunes, Moreover, eco-engineering solutions a solid structure would have to protect the appeal more to tourism users than hard land from the sea, such as dikes or dams. structures. And finally, licences are often Building for nature entails creating a pool issued more quickly than usual when the in the toe of a dike for juvenile fish and design takes nature and recreation into shrimp, for example. Hydraulic engineering account. These added values make u

Soft interventions with a solid impact | 5 ‘Eco-engineering, natural hydraulic engineering and building with nature: it can be done, and it works!’

eco-engineering a cost-effective option. in the meantime, and the first applications In 2009 Rijkswaterstaat, EcoShape and already have been – or still are being – Deltares launched the first eco-engineering implemented in the field. The parties are pilots, which are described in the booklet also working on new eco-engineering published by Rijkswaterstaat in 2009 projects. Eleven of these are described in entitled Harde werken met zachte trekken this short book. They are inspiring examples (‘Solid interventions with soft impact’). of why the time is right for the large-scale The pilot phase has largely been completed application of eco-engineering. •

6 | Rijkswaterstaat and Deltares Reader’s guide

The eco-engineering projects mentioned in this booklet can be applied in different ways. The table below contains short descriptions, an overview of the different ecosystem services and the status of each project. An application is a functional and permanent structure. A pilot project, by contrast, is temporary in nature.

Building with nature in saltwater

Project name Status Description Ecosystem service Extra services Result Sand Engine Application Concentrated Flood protection Recreation, nature Sand is spread rapidly mega-nourishment and biodiversity along coast, new dune resulting in less development and disturbance of more recreational use benthic fauna Oyster reef Application Construction of Flood protection Nature and Clear increase of an oyster reef to biodiversity, silt due to reef counter erosion nursery/fishery and establishment of new oysters Oesterdam Application, Ecologically designed Flood protection Natura 2000, Results not implemented nourishment nature and available yet in 2012 and oyster reefs biodiversity

Soft interventions with a solid impact | 7 Building with nature in freshwater

Project name Status Description Ecosystem service Extra services Result Noordwaard Application under Developing a Flood protection Recreation, Result not construction, wave-attenuating nature and available yet implementation willow foreshore biodiversity between 2011–2015 for a dike Foreshore levee Pilot project Building reed Flood protection Water quality, nature The reed marshes marshes to and biodiversity, have a wave- dissipate wave nursery/fishery damping effect; energy and trap their floating ability sediment has to increase Shoreline dike Design phase Constructing a Flood protection Water quality, Result not soft dike with recreation, Natura available yet marsh zones 2000, nature and biodiversity Marsh restoration Stakeholder Temporary land Flood protection Nature and Result not participation reclamation to turn biodiversity, available yet open water into nursery/fishery, marsh again food, recreation Soft Sand Engine Pilot project, Allow forelands to Flood protection Nature and Result not implemented in grow along with biodiversity, available yet 2011–2012 changing water levels recreation by promoting the transport of sand

Building for nature in saltwater

Project name Status Description Ecosystem service Extra services Result Eco-concrete Application Construction of Natura 2000 Water quality, Quicker micro and macro nursery/fishery, establishment structures to existing nature and of algae, concrete slabs to biodiversity mussels promote the and periwinkles establishment of benthic organisms Tidal pools Application Construction of small Nature and Nursery/fishery, Increased pools at the base of biodiversity recreation, biodiversity dikes to promote Natura 2000 by a factor the establishment of of three organisms Hanging Pilot project Use rope to hang Nature and Water quality, Purifying effect structures completed structures to biodiversity nursery/fishery, and significant increase the flood protection increase adhesion surface of biomass for shellfish

8 | Rijkswaterstaat and Deltares Explanation of the ecosystem services used

Flood protection The eco-engineering solution creates additional protection against flooding by dissipating wave energy, capturing sediment, stopping erosion increasing seepage length and stabilizing flood defences. Water quality The solution promotes water quality, because plants and filter feeders – such as mussels and oysters – remove organic material, silt, nutrients and toxic materials from the water. Natura 2000 The application makes it easier to achieve the Natura 2000 objectives, for example because it creates a larger living environment or increases the availability of food for Natura 2000 species. Nature and biodiversity The application promotes the natural value and biodiversity of the area. Food An ecosystem that is part of the solution provides food for humans, such as mussels, shrimp and edible plants and fruits. Nursery/fishery The application provides sheltered places where juvenile fish and shellfish can develop, or it promotes the growth of food for fish. Recreation The structures that are built offer a pleasant environment for recreational purposes or provide new opportunities for recreational activities.

Soft interventions with a solid impact | 9 Building with nature in saltwater

Sand Engine

The beaches and dunes of the sandy Implementation Dutch coast protect the hinterland Between March 2011 and November 2011, from flooding. Sand nourishment a hook-shaped peninsula was created along allows natural processes to maintain the coast at Ter Heijde – the Sand Engine. this sandy coast and ‘dynamically’ keep The peninsula juts out one kilometre into it in place. The sand for nourishment is the sea, and when completed it was two dredged from deep waters (below the kilometres wide.01 The total surface area was 20-metre depth contours). Water and initially more than 100 hectares. In total, wind distribute this sand naturally 21.5 million m3 of sand was deposited, along the beach and across the dunes. 2.5 million m3 of which was placed on opposite sides of the peninsula as an Every four or five years, supplementary underwater nourishment to prevent sand is deposited along the narrow coast short-term erosion. The Sand Engine is a between Hoek van and The Hague fairly even ‘shoal’, containing a small lake – known as the Delfland Coast. On average, about eight to ten hectares large and two between 300,000 m3 and 500,000 m3 of metres deep. The lake introduces more sand is deposited every year on the beach variation in bedforms and water levels, or in the shallow water near this part of which enables nature to develop better. the coast. The faster the sea level rises, The Sand Engine’s key higher points are a the more sand needs to be deposited. spine about five metres above mean sea Frequent nourishment is unfavourable level around the lake, a slightly higher for the benthic organisms because it point seven metres above sea level and a traps them under the sand. spine that is four metres above mean sea It takes three to five years for the benthic level straight across the Sand Engine community to fully recover. Mega- (pointing in a north–south direction). nourishment – an excess of sand that These parts remain dry when water levels are is gradually spread by the tide, waves high, but they are significantly lower than the and wind – is an alternative to frequent dunes in Solleveld, an adjacent nature area. nourishment. This kind of nourishment needs to be repeated much less often Results and spreads the sand across the contours Six months after it was created, the of the coast as naturally as possible. peninsula had already begun to gradually This enables us to preserve our natural change shape, and the hook is expected to coastal defence of beaches and dunes, eventually join the beach. The resulting and creates more space for nature and shape will resemble a bell, which over the recreation. In 2011, the Delfland Coast years will gradually spread to the north and Sand Engine pilot experiment was to the south. As a result, the beach will launched to examine the effectiveness widen and create new dunes. The sand will of mega-nourishment. be blown away from the beach and into u

10 | Rijkswaterstaat and Deltares Building with nature in saltwater

Sand Engine

ecosystem service flood protection, recreation, nature and biodiversity

specification • replenish coastal defence’s supply of sand • preserve coastline • dredge and deposit sand less frequently • more recreational options • ecological potential

system saltwater with pockets of freshwater

organisms benthic fauna, fish, birds, seals

location Delfland Coast, at Ter Heijde

status application p Jumbo hopper dredger duration 2011-2021

Soft interventions with a solid impact |11 the dunes, raising them. Part of the sand water in the dunes, the flora and fauna of will vanish in deep water. An extensive the dunes and underwater banks, as well as monitoring programme will determine recreation and nature conservation. whether the Sand Engine creates fewer disturbances than the original sand Costs and benefits nourishments and whether it improves the The Sand Engine cost €70 million. Basically protection of coastal nature and recreation mega-nourishment is not more cost-effective areas. The monitoring programme will than regular small-scale nourishment in terms enable involved parties to expand their of its primary function (coastal management knowledge and nourish the coast more for flood protection). Indeed, the latter is effectively in the future. The researchers quicker to yield a return on the investment. will focus on the wind, waves and the tide, Mega-nourishment creates added value the distribution of sand, the groundwater mainly for recreation and nature, and level, the geochemistry, the quality of the potentially also for drinking water supplies.

12 | Rijkswaterstaat and Deltares Other applications References If the principle of mega-nourishments • Mulder, J.P.M and Stive, M.J.F. Zandmotor: works, then it can be widely applied along Building with nature. Paper III-21, Deltares. the Dutch coast and probably abroad as well. • Tonnon, P.K., Van der Valk, L. Holzhauer, H., Baptist, M.J., Wijsman, J.W.M., Partners Vertegaal, C.T.M and Arens, S.M. (2011) Rijkswaterstaat, Province of South-Holland, Uitvoeringsprogramma Monitoring en Delfland District Water Control Board, Evaluatie Zand Motor. Deltares/Imares. Borough of Hoek van Holland, Municipality • DHV (2010) Monitoring- en evaluatieplan of The Hague, Zuid Hollands Landschap, Zandmotor. Report no. C6158.01.00. Municipality of Westland, Deltares, • Projectbureau Pilot Zandmotor (2010) EcoShape, Dutch Lifeguard Association, De zandmotor: van zand naar land. Dunea, WWF, Delfland Coast Project Office, • Provinice of South Holland (2009) Van Oord and Boskalis. De zandmotor van zand naar land. •

Soft interventions with a solid impact | 13 Building with nature in saltwater

Oyster reef

Since the construction of the Eastern stabilizing function. Nature conservation storm surge barrier, there has been organizations are using similar techniques on tidal flat erosion in the a major scale to restore oyster reefs in the estuary. Nearly 10% of the intertidal zone has United States. disappeared in the past 20 years. If no In the Netherlands this technique was used measures are taken, the tidal flats could on a larger scale in 2010 to build three large vanish from the Eastern Scheldt by 2075. artificial02 oyster reefs in two different places in This would not only adversely affect the the Eastern Scheldt. The boxes in these reefs fauna, such as seals and many birds, but had an area of six by two metres and were also the flood defences. The absence of tidal 30 centimetres high. Together, the two reefs flats would result in higher and longer are 10 by 200 metres large. waves in the deeper, more expansive open water, which would put more pressure on Results the flood defences. Initial results show that new oysters are quick to attach themselves to the gabions. Moreover, Erosion is usually reduced by means of solid the amount of silt behind the reef is increa- constructions, such as rubble or concrete dikes sing. This coincides with the results from pilot and embankments. Natural elements, such as studies on mussel beds, which show that the reef-forming shellfish can also fulfil the bed affects the composition of sediments. function of these solid constructions. This impact can be felt hundreds of metres The advantage of a natural reef is that it can away from the mussel bed. Simulations grow and thus maintains itself. So natural performed in the lab also show that the beds reefs can counter the erosion of the intertidal dissipate wave energy in shallow water. zones in the Eastern Scheldt and help trap sediment, which contributes to the Costs and benefits preservation of the intertidal flats. If the design were to be optimized, then an oyster reef could potentially be cheaper than Implementation rubble mounds. Money could almost certainly The first oyster reef was built in 2007. Living be saved on maintenance costs and oyster reefs oysters were collected and put back in the could limit the number of sand nourishments water along the edge of an intertidal flat. in the Eastern Scheldt. In addition to a The area turned out to be too dynamic, potential reduction in cost, the oyster reef however, and the oysters vanished following would provide the following benefits: a storm. In 2009, a small reef, was built, 48 m3 • Protect the hinterland against erosion by in size, using a steel-wire ungalvanized box dissipating wave energy. (a gabion) filled with dead oyster shells. • Increase the volume of land outside the The idea was that the steel frame would dikes by trapping sediment. corrode and the ‘organic bio-builders’ – in this • Cultivate oysters for (human) consumption. case the oysters – would take over the • Improve the landscape using natural structures.

14 | Rijkswaterstaat and Deltares Building with nature in saltwater

Oyster reef ecosystem service flood protection, nature and biodiversity, nursery/fishery

specification • dissipate wave energy • reduce erosion • trap sediment in and behind the reef

system saltwater/intertidal zone or subtidal Partners organisms oysters or mussels (reef-shaped shellfish) Rijkswaterstaat, EcoShape, Deltares, Imares, NIOZ, Radboud University Nijmegen.

location Eastern Scheldt References status application • Van Maldegem, D.C. and Van Pagee, J.A. (2005) Zandhonger Oosterschelde – een duration 2006-2012 verkenning naar mogelijke maatregelen. Working document, RIKZ. Report no. RIKZ/ZDA/2005.802w. • De Vries, M.B., Bouma, T., Van Katwijk, Other applications M., Borsje, B. and Van Wesenbeeck, B.K. In freshwater systems, floating reed marshes (2007) Biobouwers van de Kust. or freshwater mussels can be used to trap and Rapport haalbaarheidsstudie.WL | Delft stabilize sediment. Hydraulics. •

Soft interventions with a solid impact | 15 Building with nature in saltwater

Oesterdam

The Oesterdam is located in the eastern The sand nourishment will be subjected to part of the Eastern Scheldt. erosion, so periodic maintenance will be This dam separates the freshwater body necessary. -Zoommeer from the saltwater of the Eastern Scheldt. The dam also Implementation creates a non-tidal navigation route Rijkswaterstaat and the Scheldestromen between and the . District03 Water Board began reinforcing the The building of the Eastern Scheldt Oesterdam in 2012. They now are also storm surge barrier and the Oesterdam conducting a pilot experiment in which the diminished the tide in the Eastern area immediately in front of the Oesterdam Scheldt: less water runs into and out of is raised with sand for two kilometres. the Eastern Scheldt. The channels are Measures – for example, the use of artificial responding to the decreasing amount of oyster reefs – are being taken to slow down water by filling themselves with sediment the erosion process. In total, approximately from the tidal flats – ‘sand hunger’ – 600,000 m3 of sand will be deposited. which is reducing the surface area of the Putting this sand at a slight incline at the intertidal zone. Due to the erosion of the right height is creating an intertidal zone tidal flats in the intertidal zone, there is with a considerable surface area that less wave dampening larger continuous is dissipating wave energy and hence areas of water, and therefore increasing decreasing the pressure on the dikes. pressure on the dikes. Moreover, the Moreover, this area is a valuable habitat decreasing size of the intertidal area is for all kinds of organisms, including unfavourable for birds, which forage on foraging birds. the tidal flats. Results Countering erosion means searching for The Oesterdam Safety Buffer pilot project is ways of redistributing the sand in the system, already being conducted and is set to end in in a way that is consistent with other 2013. objectives, such as dike reinforcement. A pilot project was launched with this idea Costs and benefits in mind in order to reinforce the Calculations show that reinforcing the Oesterdam in the Eastern Scheldt, where a Oesterdam through sand nourishment is large volume of sand dredged from the cheaper than reinforcing it with rubble. channels will be deposited in front of the Although the management and dam. This will ease the wave pressure on maintenance of the foreshore could initially the dam and reduce dike erosion. In the cost more, in the long term the balance is long term, this could save on maintenance expected to be positive. Other benefits of costs for the dam. Moreover, the mud flat the nourishment of the foreland are: in front of the dam – an important • Preservation of the tidal flats in front of foraging area for birds – will remain intact. the Oesterdam.

16 | Rijkswaterstaat and Deltares Building with nature in saltwater

Oesterdam

ecosystem service flood protection, Natura 2000, nature and biodiversity

specification • dissipate wave energy • raise tidal flats • create living and foraging area for benthic fauna, fish and birds

system saltwater Other applications A sandy foreshore can strengthen flood organisms benthic fauna, defences if the incline at the bottom is not fish, birds too steep for the defence and not completely muddy. The exact type of foreshore depends location Eastern Scheldt, on the abiotic conditions at the site in Oesterdam question.

status application Partners Rijkswaterstaat Zeeland, Zeeweringen Project duration 2012-2013 Office, Province of Zeeland, Climate Buffer Coalition, Deltares, Imares, Ecoshape.

• Redistributing the sand is consistent with References the strategy of mitigating the impact of • Natuurmonumenten, Rijkswaterstaat sand hunger in the Eastern Scheldt. That Zeeland, Province of Zeeland (2011) Oyster is important for long-term protection, Dam Safety Buffer implementation plan. nature and recreation. • De Bel, M., Schomaker, A.H.H.M. and Van • Adding sand makes it possible to anticipate Herpen, F.C.J. (2011) Meerwaarde levende changing hydraulic demands on the protec- waterbouw. Een maatschappelijke tion of the embankment in a flexible way. kostprijsanalyse. Royal Haskoning. •

Soft interventions with a solid impact | 17 Building with nature in freshwater

Noordwaard

Reversing land reclamation in Noordwaard is with stone constructions. This will save on one of the measures proposed by the Room construction and maintenance costs. The for River programme. To be able to divert Rivierenland District Water Board is taking the more river water when levels are high, the design into its own hands and is thus polder is becoming part of the Nieuwe responsible for maintaining the willow Merwede flood plain. As a result, twice a year, foreshore as well. Several scenarios for the best when there is high river runoff, the polder possible04 management were explored and is temporarily flooded. A new dike needs calculations were made with the help of to be built to protect Fort Steurgat, which is models. Findings suggest that it is best to trim located in Noordwaard. the trees every two or three years to keep the willow foreshore sufficiently thick and healthy. The initial idea was to build a ‘traditional’ dike, Half of the trees should be trimmed at a time so 5.5 metres above NAP (mean sea level) and that the wave-attenuating function of the lined with stones on the riverside. Inhabitants wooded foreshore remains intact after of Fort Steurgat, however, were strongly trimming. The dike itself is low maintenance opposed because the high dike would restrict and only needs to be mowed. their views and tarnish the Dutch Waterline (Hollandse Waterlinie), which the fort is part of. Results The solution was a partly natural defence. In 2012 the parties developed a method for A foreshore with willows was built in front of testing this new dike concept, and the dike to dissipate wave energy so that the subsequently agreed on management and dike does not need to be raised. Research monitoring protocols. The water board will shows that a strip of willows 100 metres wide evaluate the project in a later round of can reduce the size of one metre-high waves by testing. Based on model calculations, the 80%. As a result the dike can remain lower and parties expect the wave height to be reduced be lined with clay instead of stones. Inhabitants by 80%, as a result of which the dike can and administrators have responded positively remain one metre below the original to this innovative solution. design. This has not been incorporated yet in an assessment programme, which will Implementation eventually evaluate the extent to which the The wave-attenuating flood defence is a willows reduce wave energy. combination of a dike (4.8 metres above NAP) and a willow foreshore about one hundred Costs and benefits metres wide. The willow foreshore will consist The construction costs of the wave-attenuating of Salix alba and Salix viminalis, species that thrive dike are apparently €1,550 per metre less than in high groundwater levels and can withstand they are with a traditional dike; for example, waves. Approximately four trees will be planted the incline does not need to be clad in stone. per square metre. The dike will be strengthened by lining it with clay. Thanks to the willows, According to calculations, the management it will not be necessary to strengthen the dike and maintenance costs are two euros per metre

18 | Rijkswaterstaat and Deltares Building with nature in freshwater

Noordwaard ecosystem service flood protection, recreation, nature and biodiversity

specification • dissipate wave energy • restore the historic landscape • increase biodiversity • trap silt

system freshwater Other applications • A wave-attenuating willow foreshore is organisms willows useful in river areas when the height of the waves affects the height of the dikes. location Noordwaard • If the dike lining is insufficient or if there is a risk of internal erosion, a good solution is status application a foreshore on a clay platform. • Other sturdy marginal plants can be used duration 2011-2015 instead of willows. Tidal marshes and mangroves provide similar ecosystem services in saltwater and tropical environments.

more per year. The wave-attenuating dike Partners provides the following benefits to society: Rijkswaterstaat, Room for River programme, • Protects Fort Steurgat at high tide. Deltares, Noordwaard Project Office, • Fits in better with the landscape because the Rivierenland District Water Board. dike can remain lower and does not need to be cemented. The inhabitants of Fort References Steurgat will still have an unobstructed view. • Borsje, B., Van Wesenbeeck, B.K., Dekker, F., • The foreshore improves the landscape and Paalvast, P., Bouma, T.J., Van Katwijk, M. has cultural values (ancient tradition in and De Vries, M.B. (2011) How ecological marshy areas). engineering can serve in coastal defense • The foreshore creates a new habitat for flora strategies. Ecological engineering 37: 113-122. and fauna where land and water meet. • Bureau Noordwaard (2008) Inrichtingsplan • The willows create a reservoir for the storage Ontpoldering Noordwaard.

of the greenhouse gas CO2. • De Vries, M.B. and Dekker, F. (2009) Ontwerp • The trimmed willow shoots could be used to groene golfremmende dijk Fort Steurgat bij make fascine mattresses or as a biofuel. Werkendam. Deltares. •

Soft interventions with a solid impact | 19 Building with nature in freshwater

Reed marshes

Many water bodies in the Netherlands, Almost 50,000 rhizomes were braided in including major lakes, are bounded by between the layers of willow. The idea was for dikes. The by nature gradual transitions the mats to become overgrown with reed and between land and water, which have great simultaneously trap silt. Then the mats would natural value, are thus replaced by harsh, sink, after which the reed, rooted in water, steep transitions. Few riverbank plants can would create a zone with vegetation at the spontaneously take root along the steep base of05 the dike. incline or in the deep water. As a result, dikes are directly exposed to waves and Results currents and require relatively high Reed already began to grow three weeks after maintenance. Floating mats with riverbank the floating mats were deployed. Water birds vegetation could address this problem. also used the island and the shelter created next to the island. The floating willow mats These structures of mats dissipate wave with reed vegetation did indeed dissipate wave energy, thereby reducing dike maintenance. energy. Deltares tested wave attenuation in They also improve the quality of water by a wave basin in a separate experiment. converting nutrients and trapping silt. Moreover, sedimentation was observed Filter-feeding organisms, such as the zebra beneath the mats. After several months, the mussel, can attach themselves to the bottom construction was damaged during a storm, of the mats. The idea is that the mats will which threatened to detach parts of the eventually sink when the reed marsh has construction. The pilot experiment was developed sufficiently. The reed, rooted in the therefore halted prematurely and so only water, survives. It then takes over the some of the research questions were wave-attenuating function of the mats. This answered. The results do indicate, however, principle was tested in a pilot project near the that these floating constructions are Houtrib locks in Markermeer. essentially suitable in multifunctional reed banks, which also dissipate wave energy. Implementation However the design needs to be further The pilot project used mats made of braided optimized. willow shoots. These become quickly overgrown with riverbank plants, such as Costs and benefits reed. And they create protected, shallow Outweighing the costs of the floating reed places at the base of the dike where sediment marshes are the following benefits: can be trapped. Traditionally fascine mats • Dissipate wave energy (thereby reducing were used to stabilize underwater hydraulic dike erosion). The mats are capable of engineering constructions. The mats were dissipating wave energy by 80%, depending placed near the Houtrib locks in Markermeer on the length of the wave and that of the in the summer of 2009. They were 30 by mats. 100 metres large, 40 centimetres thick and • Improve water quality through the weighed as much as 80,000 kilograms. purifying effect of vegetation.

20 | Rijkswaterstaat and Deltares Reed marshes

ecosystem service flood protection, water quality, nature and biodiversity, nursery/fishery Other applications specification • dissipate wave energy • The reed marsh described above can be • capture sediment used in areas along bodies of freshwater • restore gradual transitions whose banks have a gradual incline. More from land to water natural foreshores with a damming function could also be used along small system freshwater bodies of freshwater, such as water storage areas and large streams. organisms reed, water plants, freshwater • Fascine willow mats were still used in 2012 mussels to protect quays and for nature development in Zeeburg in Amsterdam. location Houtrib locks, • Similar ecosystem services could be Markermeer provided at an international level using other types of floating materials or status pilot project vegetation.

duration 2008-2010 Partners Rijkswaterstaat Water Service and Ijsselmeer Area, Deltares, Hoeksewaard Landscape and Van Schaik BV.

• Improve water clarity by trapping sediment. References • Increase the diversity of habitats and species • Van Steeg, P. and Van Wesenbeeck, B.K. (above and underwater). (2011) Large-scale physical modelling of wave • Food source for birds. damping of brushwood mattresses. Deltares. • Restore landscape values (transition • Van Geest, G., Geerling, G. and between land and water). De Vries, M.B. (2010) Pilotstudie drijvende

• Capture the greenhouse gas CO2 in the rietmoeras Houtribsluizen. Rijkswaterstaat marsh. IJsselmeer Area. •

Soft interventions with a solid impact | 21 Building with nature in freshwater

Foreshore levee

Traditionally, dikes that are no longer A foreshore levee is a slightly inclined body of sufficiently safe are widened and raised. soil that is placed against the outside of an The space needed for these changes often existing dike. This creates a gradual shoreline on comes at the expense of housing along the border of land and water, which dissipates the dike, infrastructure or nature areas. wave energy. The foreshore levee is so high and The people living there are often critical wide that it guarantees protection and fulfils the of major landscape interventions. function06 of the existing dike. Therefore the This is particularly true of the dike of latter does not need to be reinforced, and barely the Markermeer between Hoorn and any measures need to be taken inside the Amsterdam. This reinforcement of existing dike. The built-up area is hardly this dike is especially tricky due to an disturbed. The shoreline’s shallow areas and instable, settlement-sensitive sub- inclines also provide a habitat for various plants stratum. An alternative to widening and animals. They are ideal migration zones for and raising such a dike is to build what species such as grass snakes, and provide is called a foreshore levee. nesting areas and shelter for birds. An additional advantage is the positive effect on water quality as the silt settles both in the new shoreline and in the sand pits that were dug for the construction of the foreshore levee. Foreshore levee Implementation ecosystem service flood protection, water quality, recreation, Natura 2000, Different versions of the foreshore levee can nature and biodiversity be implemented: 1 A foreshore levee with a large body of sand specification • dissipate wave energy that remains stable due to the erosion and • capture silt to allow growth sedimentation of material. with rising water level 2 A foreshore levee with sand and reed, in • focus design on Natura 2000 which the reed is protected by a foreshore species defence. The latter is the best ecological alternative. system freshwater It is an interesting option for certain approaches, including one that incorporates organisms shoreline vegetation recreational uses.

location Markermeer Results between Hoorn The foreshore levee was added to the planning and Amsterdam study for the reinforcement of the dike of the Markermeer. This variant was further status design phase elaborated in 2011, so that it can be tested by means of an environmental impact study.

22 | Rijkswaterstaat and Deltares Top: Artist’s impression of the foreshore levee with sand and reed. Bottom: Cross section of the foreshore levee.

A foreshore levee requires intensive • The construction takes place from the monitoring. In particular, settlement, erosion water, thereby avoiding the disturbance and use need to be carefully monitored. and damage inflicted by transport across land and by activity on the existing dikes. Costs and benefits A foreshore levee is likely to be more cost Other applications effective than the usual solution. How much A foreshore levee is a potential alternative more depends on the price of sand and soil. for all places along lakes, where traditional A foreshore levee could cost 30% less at a dike strengthening is needed. unit price of €9 per cubic metre. The savings are mostly gained during construction: the Partners management and maintenance of a Rijkswaterstaat Flood Protection foreshore levee are expected to be more Programme, Director-General Space and expensive. Other benefits include: Water, Province of North Holland, Deltares, • Greater dike stability, reducing the likelihood Arcadis, Haskoning, Hollands of it weakening due to internal erosion. Noorderkwartier District Water Board and • Greater natural value thanks to gradual Ecoshape. transitions from land to water, such as from shallow protected water to reedland, marshy References woodland and higher grassland. These areas • Fiselier, J., Jaarsma, N., Van der Wijngaart, are spawning areas for fish, breeding T., De Vries, M.B., Van de Wal, M., grounds and foraging areas for birds, and Stapel, J. and Baptist, M. (2011) Perspectief ecological corridors. This contributes to the natuurlijke keringen. Ecoshape. objectives set out in the European Water • De Bel, M., Schomaker, A.H.H.M. and Framework Directive and Natura 2000. Van Herpen, F.C.J. (2011) Meerwaarde • Increase the landscape and recreational levende waterbouw. Een maatschappe- values. lijke kostprijsanalyse. Royal Haskoning. •

Soft interventions with a solid impact | 23 Building with nature in freshwater

Marsh restoration

The expansive marsh areas along the coast development of marshes in open water of Louisiana in the United States are areas, which is where most erosion occurs. eroding at breakneck speed. Every year a One potential technique is the temporary marsh area the size of the municipality of creation of an enclosed hydraulic The Hague (75 km2–85 km2) vanishes. The engineering unit by damming the area. erosion has various causes. Since the Water management in this type of units damming of the Mississippi, the river no would07 focus on regenerating marsh longer disposes of sediment along the vegetation and capturing sediment, or on coast, and more and more marshland is developing peat. disappearing underwater. Channels also cut across the marshes in many places. Implementation To create a temporary hydraulic engineering These channels, and the lack of freshwater unit, parts of the open water have to be discharge, give intruding saltwater free surrounded by a dike and drained. Draining rein. Saltwater intrusion in areas that were land promotes the germination of seeds in the originally freshwater kills freshwater soil. As soon as vegetation has established vegetation and causes the development of itself, peat formation has to be set into large open areas. The wind and wave have motion. Soil saturated with water is needed free rein along the edges of these large for this. Peat formation and sedimentation areas of water, thus accelerating erosion. cause the low-lying polder to grow naturally Marshes are economically invaluable to again. How quickly this process occurs under Louisiana. They are the foundation of the specific local conditions is unknown, but in state’s fishery and shellfish industry, one more moderate climates peat forms at a rate the most important economic activities in of seven centimetres per year. Within 10 years the area. Moreover, the marshes are a soft peat deposits should emerge that are thick coastal defence around the most densely enough to float independently. Subsequently populated areas in the state, such as New the water level can slowly be raised again, so Orleans. Without the ring of marshes, it that the peat deposit will float and reach the would be extremely expensive to protect a same height as the floating marshes city like New Orleans from the destructive surrounding it. Then the dike can be broken tidal waves that accompany hurricanes. down in stages, and the marsh can be And finally, marshes also have great reconnected with its environment. Aids such natural value: they attract tourists and are as floating mats made of willow shoots or an important factor in capturing and other natural materials can help fill the holes

storing CO2. more quickly.

There are different techniques for restoring Results marshes, such as raising an area with This special technique may be tested in dredged sediment. However, there are a pilot project near New Orleans. To gain hardly any techniques that encourage the broad support for the idea and the pilot

24 | Rijkswaterstaat and Deltares Marsh restoration

ecosystem service flood protection, nature and biodiversity, nursery/fishery, food, recreation

specification • restore marsh for coastal protection project, the parties involved are working • reduce erosion of marsh intensively with nature conservation • preserve nursery function organizations, the estate manager and authorities on a bottom-up participation system freshwater process. The Jean Lafitte National Historical Park and Reserve chose a location for the organisms marsh vegetation pilot project: a lake no more than one and a half metres deep, where there used to location Yankee Pond, to the south-west be a peat bog enclosed by a dike used for of New Orleans agricultural purposes. As a result of drainage, this peat bog settled, and the land was abandoned. The lake was created when the small dikes burst. The rest of the old dikes can still be seen along the edges of the lake. status stakeholder The pilot project has not started yet, participation because funding for the implementation has not been secured yet. u

Soft interventions with a solid impact | 25 Costs and benefits peat to develop naturally, and the process Restoring the marsh and encouraging its needs to be managed and monitored. development by enclosing it with a dike is The marsh areas are so important for the an affordable option, certainly compared to economy and for hurricane protection, that the ongoing initiatives for the restoration of a cost–benefit analysis would surely show the marsh, which are having limited the restoration and protection of these success. Moreover, this technique can be areas to be a favourable solution. used in large open-water areas. The initial investment is relatively high for Louisiana, Other applications partly because it concerns such a large area. A good example of marsh development In addition it will take years for a layer of through reclamation and an enclosing dike

26 | Rijkswaterstaat and Deltares are the Oostvaardersplassen in the Partners Netherlands. A rich marsh area developed Rijkswaterstaat Water Service, Deltares, here following reclamation. This principle Imares, DHV, EVD, and US Army Corps of can probably be used elsewhere for other Engineers. types of marshland. Further, on a smaller scale, holes in the marsh in Louisiana are References being filled with floating mats. Until now, DHV/IMARES/Deltares (2009) Subsidence these mats have been largely made from reversal through marshland restoration. • artificial materials, but they can be made from natural mate rials that are available locally as well.

Soft interventions with a solid impact | 27 Building with nature in freshwater

Soft Sand Engine

Plans are underway to raise the water Workumerwaard, 25,000 m3 of sand was level of the IJsselmeer and reinforce the deposited, mostly from the IJsselmeer, in the dikes along its shoreline. Raising the form of an elongated sandbank. Waves, dikes means interfering with the area’s currents and – in the winter – floating ice carry landscape and cultural qualities. this sand gradually to the coast. Perpendicular An overgrown area outside the dike, to the coast, a 500-metre-long row of poles a ‘foreland’, could provide a solution was built08 that captures part of the sand and here, because a foreland dissipates wave prevents it from flowing towards the energy and creates a protective buffer for Afsluitdijk. In Workumerwaard, planning and the dike. This reduces dike maintenance monitoring focuses on developing nature, and makes it more solid when water while the emphasis in Oudemirdum is on levels are high, as a result of which the protecting the coastal defence. dike will need to be adapted less often. Results Forelands also function as breeding grounds The Soft Sand Engine at Workumerwaard was for birds, and recreational users can enjoy constructed in 2011. The spreading of sand is the nature outside the breeding season. carefully monitored. Researchers determine The forelands grow along with the rising water the baseline on jet skis equipped with echo level, providing there is a sufficient supply of sounding and Differential GPS. This system sediment. To create or maintain forelands, uses radio stations on the ground to improve sand is deposited in strategic places along the the positioning accuracy of the GPS. Until coast (nourishment). The waves and currents 2013, new soil maps were made twice a year to subsequently spread the sand. The sand will chart sand movements. In addition, a fibre- be moved less quickly here than in open sea, glass cable four kilometres long – resembling as is the case with the Sand Engine on the a snake on the bottom – is charting the Holland coast (see project 1 on page 10). distribution of sand. The turbidity of the water That is why we call this one a soft Sand Engine. and direction of the current are measured, In the summer of 2011 sand was deposited at and the development of vegetation is mapped the Workumerwaard foreland. A pilot project from a helicopter. The researchers monitor is also being prepared along the coast at the ecological impact by periodically taking Oudemirdum. These pilot projects are part of samples of the flora and fauna in a number the Natural Climate Buffers and Building with of fixed areas. Nature (IJsselmeer case study) programmes. Costs and benefits Implementation The costs of this project have not been The first pilot project was conducted in the specified. Compared to alternative interven- Workumerwaard nature reserve in the tions, this Sand Engine is the most province of Friesland, not far to the south environmentally friendly. Reinforcing the of the Afsluitdijk causeway. Along the edge dikes, besides inflicting damage to the of the expansive shallows in front of landscape and cultivation, also leads to the

28 | Rijkswaterstaat and Deltares Soft Sand Engine

ecosystem service flood protection, nature and biodiversity, recreation

specification • dissipate wave energy Other applications • raise the land outside the dike The principle of allowing wave-attenuating • preserve unique freshwater forelands to grow by adding sediment is also habitats applicable in saltwater and along rivers. However, the use of forelands does require system freshwater space between the deep channels and the water defences. organisms pioneer vegetation Partners Province of Fryslân, Wetterskip Fryslân, locati0n IJsselmeer, Workumerwaard, It Fryske Gea, Climate Buffer Coalition, Oudemirdumerklif Responsible Management Foundation IJsselmeer, EcoShape, Deltares, Arcadis status pilot and Alterra.

construction 2011-2012 References • Arcadis (2010) Building with Nature pilot Workumerwaard. MIJ 3.2 Ecodynamic Design. • De Vries, M.B. and De Koning, R. (2009) Klimaatverandering en ruimtelijke loss of shore areas outside the dike. kwaliteit – kansen voor het Friese Directly raising the dike with sand gives kustlandschap. Atelier Fryslan Werkplaats the ecosystems insufficient time to adapt. voor Ruimtelijke kwaliteit. •

Soft interventions with a solid impact | 29 Building for nature in saltwater

Eco-concrete

Much marine life, such as mussels, Results barnacles and seaweed, need a hard surface The use of eco-concrete in sea defences to survive. In the Netherlands, they find this provides the same protection as ‘regular’ surface on hydraulic engineering concrete. A first pilot project with eco- constructions, such as harbour piers and concrete was started in 2008. After two years seawalls. But modern concrete is becoming of monitoring, the pilot project was increasingly smooth and therefore less successfully09 completed, and in principle suitable for these organisms to establish eco-concrete was deemed a success. themselves. The use of special ‘eco- The rough surface of the eco-concrete with a concrete’ during the construction or rough surface became overgrown with algae renovation of hydraulic engineering much more quickly than smooth concrete. structures appears to significantly speed up Within two and a half years, mussels and the process by which these species establish periwinkles barely established themselves on themselves and their diversity. smooth structures but did on eco-concrete slabs with macro-structures such as grooves, This is especially important in areas that recesses and holes, where water lingers longer take Natura 2000 species into account, during ebb tide. The success of the pilot where the rapid return of these species can project led to the large-scale production in speed up work. Eco-concrete is concrete 2011 of concrete blocks with macro-structures with a special texture and geometric shapes for IJmuiden’s harbour piers. that enable organisms such as algae, seaweed, periwinkles and mussels to attach Costs and benefits themselves more easily. These organisms, The production of concrete with special in turn, are a source of food for birds and textures and geometric shapes is expected fish. And mosquito larvae, which live to cost 2% to 3% more than the production among the algae, are a source of food for of traditional ‘smooth’ concrete. However, protected bird species such as the ruddy there are many benefits that outweigh these turnstone and the purple sandpiper. marginally higher costs. The use of eco-concrete encourages various marine Implementation flora and fauna to establish themselves, and Slabs of eco-concrete with different after renovations species appear to return structures, such as horizontal and vertical more quickly. These species are a source of ridges, hollows and holes, were used in the food for birds and therefore marine life. pilot project at Zuiderhavenpier in IJmuiden. Eco-concrete can speed up save money Tests were conducted to assess the impact of on replacement work, which has to take these structures on the speed of colonization these species into account. In addition, and the ultimate biomass of algae, mussels eco-concrete could be used as a mitigating and periwinkles. ‘Eco-Xblocks’ were also measure for negative effects on Natura 2000 used, which are craggy concrete blocks with a objectives. And finally, eco-concrete rough surface that resemble natural rocks. improves water quality because more

30 | Rijkswaterstaat and Deltares Building for nature in saltwater

Eco-concrete

ecosystem service Natura 2000, water quality, nursery/fishery, nature and biodiversity

specification • encourage colonization by algae and larvae • algae and larvae attract fish • increase filtering capacity of water as piers and breakwaters, are constructed or system freshwater/intertidal zone renovated, or when existing structures are raised. organisms algae, seaweed, mosquito larvae, birds (ruddy turnstones • Eco-concrete can be used along rivers and and sandpipers), mussels, lakes when solid structures, such as periwinkles groynes, banks and breakwaters, are constructed or renovated. • Eco-concrete can be used along regional location Zuiderhavenpier water courses when solid defence structures IJmuiden along water storage areas and streams are constructed or renovated. status application Partners construction 2008 and 2011 Rijkswaterstaat Water Service, Rijkswaterstaat Board North Holland, Deltares, BAM-DMC, Microbeton and Ecoconsult.

mussels establish themselves. Mussels filter References water, making it cleaner and clearer. • Van Wesenbeeck, B.K. and De Vries, M.B. (2007) Pakket van eisen Eco-beton. Deltares. Other applications • Paalvast, P. (2011) Pilotstudie Eco-beton • Eco-concrete can be used along the coast Zuiderhavenhoofd IJmuiden, 2008–2010: when hard coastal defence structures, such Een Rijke Dijk project. Ecoconsult. •

Soft interventions with a solid impact | 31 Building for nature in saltwater

Tidal pools

Solid constructions along the coast, Results such as dikes, harbour piers and dams, Monitoring revealed that significantly more are the habitat of various marine species. species are found in the pools than in the Many of them live exclusively in places that rocks around them. Different seaweeds grow are continuously underwater. By making there, and there are also different kinds of simple and inexpensive adjustments to sponges and ascidians. The biodiversity in the solid structures, water in higher parts of the pools are approximately10 three times greater intertidal zone will linger longer. This can than in the standard situation without pools. be a huge boost to biodiversity and biomass Juvenile fish and the common prawn also like and can be used as a mitigating measure for to stay there. To prevent them from falling Natura 2000 objectives. prey to foraging birds during low tide, there have to be sufficient sheltering options, In order to achieve this, small pools can be for example rocks. The pools probably built at the base of dikes. These dikes thus have a positive effect on the surrounding have added value for marine species, without ecosystems as well. endangering the primary function of flood protection. The shape, height, design and Costs and benefits placement of the pools affect which species The toe of a ‘regular’ dike about five metres will eventually establish themselves there. wide costs about €100 per linear metre. In the pilot project the toe of a dike with tidal Implementation pools costs about €400 per linear metre. In 2008, a number of small pools were This higher price is primarily due to the cost developed along the Eastern Scheldt near of making the pools waterproof. This can be Yerseke in the toe of the dike. These pools done less expensively by developing a better were a few metres to 15 metres long and method, or perhaps by including the pools in were filled with different-size rocks. As a their entirety in the assignment. The pools result, good living environments were do not have any management costs. created in these places for various marine The overall conclusion is that the species. A second project followed in 2010 accompanying costs for the construction of between Wemeldinge and Kattendijke, these kinds of small pools are marginal where large pools (15 x 150 metres) were compared to the total costs of constructing built. These pools were lined with concrete or renovating a dike. Various benefits to make them waterproof so that water outweigh the costs: would remain during ebb tide. By filling the • The organisms present in the tidal pools are pools with different kinds of rock, such as a source of food for birds (including species lava rock, there is sufficient substratum for on the Red List) and other marine life. algae and other organisms to attach • ‘Rich’ dikes increase the recreational and themselves, and it simultaneously provides educational value of the area. sheltering opportunities for macrobenthos • Opportunities are being created for nature and juvenile fish. compensation and mitigation.

32 | Rijkswaterstaat and Deltares Tidal pools

ecosystem service nature and biodiversity, nursery/fishery, recreation, Natura 2000

specification • establishment opportunities in the toe of the dike • good measure as mitigation under Natura 2000 • shelter for juvenile fish

system saltwater/base of dike

organisms seaweeds, sponges, sea This principle can be applied to the anemones, crabs, common construction or renovation of solid prawn, juvenile fish hydraulic engineering constructions and is therefore mainly suitable in national location Eastern waterways. Scheldt dike Partners status application Rijkswaterstaat Sea Defence Project Office, Scheldestromen District Water Board, construction 2008 and 2010 Ecoconsult and Deltares.

References • Paalvast, P. (2011) Rijke Berm Oosterschelde monitoring getijden- poelen, 2008–2010: Een Rijke Dijk Other applications project. Ecoconsult. With a ‘rich’ dike, pools are created in solid • De Vries, M.B. et al. (2010) Rijke dijken structures to retain water during low tide. werken in de Oosterschelde. Deltares. As a result, habitats are developed • De Vries, M.B. (2009) Rijke Dijken for various species that live in water. overview. Deltares. •

Soft interventions with a solid impact | 33 p Tidal pool

34 | Rijkswaterstaat and Deltares Soft interventions with a solid impact | 35 Building for nature in saltwater

Hanging structures

Ports are built to accommodate economic Results activities, such as shipping, industry and The pilot project and accompanying transport. You could say that there is monitoring process have been completed. little room for nature in this environment The pilot project revealed that the structures of steel and concrete constructions. worked well and the biomass was increasingly Nevertheless, even here simple measures, rapidly. The nylon ropes were soon colonized such as introducing artificial substrate, by mussels, barnacles and various11 algae and could increase biological productivity and other creatures. Within several months a diversity. single, one and a half metre-long hula rope produced two to three kilos of mussels. On If this substrate is then populated by average, 8.5 times more biomass attaches shellfish that filters the water to gather itself to polehulas than to a regular pole. The food, known as filter feeders, then this can pontoonhulas are larger and provide space for benefit water quality. The effects of several about 350 kilos of mussels. Calculations artificial substrate designs was examined suggest that 35 pontoonhulas per port basin in the Hanging Structures pilot project in would be enough for mussels to clean the the Port of . For that purpose, entire volume of water in the Port of ‘polehulas’– pieces of nylon rope Rotterdam every month. The hula structures resembling Hawaiian skirts – were were removed in 2010. Some pontoonhulas attached to poles. Floating PVC structures were transported to Deltares, where the hulas’ , from which large amounts of rope hung ability to dissipate wave energy was studied in down (pontoonhulas), like an upside- the Delta Basin. Findings showed that hulas down underwater forest, were also placed are effective wave-attenuating structures for in the port. dampening waves in ports.

Implementation Costs and benefits Two types of structures were used for the The construction costs are higher than in pilot project: a traditional design, with no additional 1 Polehulas: approximately 300 nylon three-dimensional structures. The necessary ropes 55 centimetres long with a diameter material, however, is relatively inexpensive. of 6 millimetres. These polehulas were tied The pilot project required more maintenance around five wooden and two metal poles. than expected because the structures became 2 Pontoonhulas: floating constructions much heavier as a result of the unexpectedly made of PVC and nylon nets, from which large amounts of mussels. These costs can be nylon ropes, hang down with a diameter kept down by optimizing the buoyancy. The of 12 millimetres. The size varied with each structures have the following benefits: pontoon (two to three square metres), as • Improved water quality. The mussels’ did the number of ropes (40 to 200) and filtering capacity reduces the amount of their length (20 to 150 centimetres). organic and inorganic material in the water,

36 | Rijkswaterstaat and Deltares Hanging structures

ecosystem service nature and biodiversity, water quality, nursery/fishery, flood protection

specification • filter water by means of mussels • increase biodiversity • provide shelter for fish • reduce wave strength

system freshwater/port • The port structures act as stepping stones organisms mussels, seaweed, ascidians, sponges, eel, mullet to ecologically connect areas. • Reduce growth on poles. • Positive effect on fish stocks, as a result of location Port of Rotterdam shelter. (Scheurhaven and • According to pilot studies, pontoonhulas Pistoolhaven) dissipate wave energy.

status pilot project Other applications • The hula structures from this pilot project construction 2007–2010 are mainly applicable in national waterways. The concept can, if implemented on a smaller scale, also be effectively used in regional waters where the water becomes clearer and more light mussels exist. penetrates through the water. Mussels can • The structures could be used at an also remove toxic substances from the water. international level. Plants such as • Increase biodiversity by constructing a new seagrass and kelp in port structures could habitat. provide similar ecosystem services. u

Soft interventions with a solid impact | 37 • Similar structures can also be designed (2011) Large-scale physical modelling of for freshwater mussels. These can be used wave damping floating mussel structures. in inland harbours, recreational lakes and Deltares. locks. • Paalvast, P. and Van Wesenbeeck, B.K. • Pontoonhulas are also suitable for (2009) Rijke Dijk in de Rotterdamse haven; dissipating wave energy. The structures vrijhangende substraten en could probably be used to protect banks Ecobetonplaten. Deltares. from waves. • Paalvast, P. (2007a) Pakket van eisen voor hangende substraten en ecoplaten in het Partners Rotterdamse havengebied. Ecoconsult. Deltares, Ecoconsult, Port of Rotterdam, • Paalvast, P. (2007b) Pilotstudie Loodswezen, Smit bv and Van Oord. vrijhangende substraten en ecoplaten in het Rotterdamse havengebied. Ecoconsult. References • Paalvast, P., Van Wesenbeeck, B.K., • Borsje, B., Paalvast, P. and Van Wesenbeeck, Van der Velde, G. and De Vries, M.B. B.K. (2012) Rijke Dijk in de Rotterdamse (2012) Creating artificial underwater Haven; een framework voor het opschalen forests with pole and pontoon hulas van pilotstudies. Deltares. in the Rotterdam harbour. Ecological • Van Steeg, P. and Van Wesenbeeck, B.K. engineering 44: 199-209. •

38 | Rijkswaterstaat and Deltares p Overgrown pontoonhula rope

Soft interventions with a solid impact | 39 Applications of eco-engineering: looking ahead

Incorporating ecosystems and their services into flood protection has attracted a great deal of interest in recent years. This short book presents eleven examples of eco-engineering concepts in action.

With help from nature, flood protection community and the knowledge sector to can be guaranteed in a cost-effective way. develop and deliver products and services. Moreover, the designs for these Conversely, businesses and knowledge interventions offer other services as well, institutes need the government to buy such as improving water quality, achieving innovative products and services. nature conservation objectives and It was this notion that prompted the creating a pleasant environment to live Association of Regional Water Authorities, in and use for recreational purposes. Rijkswaterstaat and EcoShape to sign a The surplus of water in the Netherlands covenant on 4 October 2011 to promote the provides many more opportunities for application of eco-engineering principles eco-engineering than described here. and building with nature in flood risk The time is right for us to start building management. Building with nature is also with and for nature on project and a case study within the ‘top sector’ of water landscape scales. Successfully applying at the Ministry of Economic Affairs, eco-engineering concepts depends on Agriculture and Innovation. Thus the good cooperation between government, Dutch government is underscoring the the business community and the importance of this subject. For the knowledge sector: the ‘golden triangle’. structural implementation of eco- The government needs the business engineering solutions in hydraulic

40 | Rijkswaterstaat and Deltares engineering projects, it is important that as Oesterdam Protection Buffer and Sandy – in addition to the scientific basis that has Solution of the Hondsbossche and now been laid – there is process innovation. Pettemer Sea Defences. The government, For example, by adapting asset management, business community and knowledge making uniform the sustainable procurement institutes can apply the knowledge they policy and making a uniform sustainable for have gained both in the Netherlands and flood protection. The parties want to abroad. facilitate the implementation and started to If reading this book has aroused your interest do so by setting up a guideline in 2012 for in one of the solutions, or if you see an the application of eco-engineering. opportunity to use eco-engineering in your Distilling generic principles and rules, field, then please contact: [email protected] however, still requires considerable effort, or [email protected] completely and for now every new project that uses free of obligation so that we can work eco-engineering provides new knowledge together towards a safe and natural world. and insights. Indeed, traditional engineering expertise remains subject to change. In the short term, experience is Rijkswaterstaat being gained in the field during Ecoshape implementation processes in projects such Deltares

Soft interventions with a solid impact |41 Colophon

With the cooperation of

Photography Peter Paalvast, Mindert de Vries, Bregje van Wesenbeeck, Gerben van Geest, Rijkswaterstaat, Hollands Noorderkwartier District Water Board, Natural Climate Buffers Coalition

Text Bureau Landwijzer, Bregje van Wesenbeeck & José Reinders (Deltares), Theo Vulink (Rijkswaterstaat)

English translation Speer (Contactivity)

Editorial board José Reinders, Bregje van Wesenbeeck (Deltares), Sabel Communicatie

Design Sabel Design

Print run 500 copies

Deltares Mindert de Vries, Victor Beumer, Ane Wiersma, Pieter Koen Tonnon, Margriet Roukema, Myra van der Meulen , Jamie Morris

Ecoshape Huib de Vriend

Rijkswaterstaat Pieter de Boer

And many others who directly or indirectly helped to make these concepts and applications a success.

More information If you would like to use these techniques, learn more or exchange ideas on innovative techniques, then please contact: [email protected] or [email protected]

42 | Rijkswaterstaat and Deltares Zachte werken met harde trekken 43 This volume is published by

For more information, please visit www.rijkswaterstaat.nl, [email protected]

October 2013 | cd1013sb095