Building with Nature

Transcription

1 DELTARES, JANUARY DOSSIER Building with Nature Interest in building with nature is on the rise worldwide. That is not surprising. In ever more densely-populated coastal, delta and river areas, demand for flood protection is increasing as a result of developments such as sea-level rise and land subsidence. At the same time, the inhabitants of these areas want their living environment to be sustainable. Twinning hydraulic infrastructure and natural landscapes would seem to represent the ideal combination. Even so, building with nature has not yet been applied on a wide scale. In fact, nature is still frequently sacrificed for hard infrastructure. Why is this? What are the obstacles? And above all: how can we make the most of rising enthusiasm for building with nature? PHOTO: CORBIS

2 10 DOSSIER BUILDING WITH NATURE ALLIANCE OF ENGINEERS AND EC Building with nature generates numerous benefits. Even so, hard infrastructure still dominates flood protection. Why? And how can we get away from this reflex approach? BY CARMEN BOERSMA Going against the flow of centuries of experience with building dikes is not easy. People put a lot of trust in hard engineering infrastructure. As a result, introducing an innovative concept to flood protection is far from straightforward, but current conditions seem to favour 'building with nature'. Worldwide, people are migrating to cities in coastal, delta and river areas. It is precisely these areas that are most affected by climate change, land subsidence and sea-level rise. So safety is a major issue. It has to be reconciled with intensive demand for sustainable and habitable places to live. Constantly raising dikes is not an approach that can continue to rely on automatic support, and we need to consider alternative ways of improving flood protection. Underestimated These factors mean that people are now open to the idea of, and even enthusiastic about, using natural landscapes for flood protection. Even so, hard infrastructure still dominates. Bregje van Wesenbeeck, an ecologist specialising in eco-engineering, explains why. Eco-engineering has a lot of benefits. It can cut construction costs, it takes CO2 out of the atmosphere, it makes the surroundings greener and generates extra revenue from things like tourism or water treatment. Even though more and more people throughout the world are starting to understand the benefits and even though interest in the role of ecosystems in flood protection is on the increase, many people still underestimate the benefits that the ecosystem can deliver. As a result, those benefits are not included in the design process for hydraulic infrastructure or in social cost-benefit analysis. In fact, PHOTO: SAM RENTMEESTER nature is often destroyed without thinking about the role it can play in the design. Rich dike To get out of this conundrum, Bregje van Wesenbeeck thinks eco-engineering should be part of the design process and that engineers and ecologists should work together more. Ecologists should be involved from the very outset of the design process for water engineering projects, she argues. Eco-engineering is, generally speaking, an option in all circumstances: urban or nonurban settings, large or small spaces. Even in urban areas where only hard solutions are possible, ecological options are feasible. Take the "rich dike" approach, in which the foot of the dike is shaped so that vegetation can grow on it.

3 DELTARES, JANUARY OLOGISTS HIGHLY PRODUCTIVE admittedly building up fast: we are moving in the right direction but we still need to develop a lot of knowledge. One of the things we don't know enough about is system turning points: when does the foreland erode and when does it accrete? A lot of research is still needed. Natural defences are designed differently but, ultimately, we still want to be able to test them in the same way as traditional infrastructure. So we are working hard on drafting standard rules and guidelines for design, construction and management. Trust in natural defences is not something that develops naturally. Establishing these guidelines will involve a lot of measurements and modelling, and a lot of projects are in progress, both in Europe and elsewhere. Strategic alliances are also being established to boost our knowledge base quickly. Bregje believes that most added value can be generated by synergetic solutions. Traditional engineering techniques such as building clay dikes or dams can be combined with ecosystem conservation or recovery. One example has resulted in the restoration of many kilometres of mangrove forests on the coast of Vietnam, saving millions of dollars every year on the maintenance of the dikes in the hinterland. We are now implementing the same approach in Indonesia: soft measures adapted to the system in order to prevent coastal erosion and bring back mangroves. Challenge Bregje recognises that eco-engineering still faces numerous challenges. The knowledge base is Management Management is also a challenge because it works differently than with hard infrastructure. Nature is dynamic, and it is constantly developing, explains Bregje. To a certain extent, we can predict the dynamics and that can help, for example, when deciding about monitoring frequencies for a particular area. It is essential for management to be tailored in the light of monitoring results. We already have a lot of experience in this area for sandy coastlines and we are now learning more about how to work with other systems. Risk management is also developing: we have picked up very extensive experience in this field working on traditional solutions like dikes and dams. We can also use those methods with more natural dike types. CV Bregje van Wesenbeeck (The Hague, 1976) is an ecologist whose doctorate focused on the dynamic behaviour of salt marshes. As a specialist in eco-engineering, she has worked on projects throughout the world and she plays a pioneering role in this field. She participates in international expert groups and platforms, and publishes regularly on eco-engineering in leading scientific magazines. Bregje has been working for Deltares since 2007

4 12 DOSSIER BUILDING WITH NATURE FROM AMBITION TO PRACTICAL EXECUTION: THREE RECOMMENDATIONS FOR MANAGERS Managers are embracing building with nature. Improving flood protection in combination with the preservation or restoration of ecological values fits in with the trend of increased sustainability in the habitat. But policy declarations have not always been enough to get eco-engineering off the ground. Three suggestions for transforming good intentions into tangible results. ORGANISE THE ADMINISTRATIVE PROCESS Building with nature means combining flood protection with the preservation or restoration of ecological values. Nature and flood protection are two different policy areas that are housed with different administrative institutions. That means that they are managed by different people, with their own policy objectives and separate sources of funding. To get eco-engineering off the ground successfully, the managers of the various policy fields will have to get together and implement joint action. Devising projects that serve multiple goals - protection and nature - is useful in that respect, bringing together regulatory institutions, linking separate flows of funding and therefore facilitating decision-making. COMBINE TECHNOLOGICAL AND ECOLOGICAL EXPERTISE Flood protection is often designed by engineers, who have adopted traditional, hard infrastructure as the guiding principle for many years. If eco-engineering is to succeed, ecologists must be involved in the design process. They are familiar with the ecosystem and can, depending on the local situation, identify opportunities. Ecological expertise is also important in the decision-making process. Standards are already in place for traditional hydraulic infrastructure. Eco-engineering is a relatively new concept, and so levels of robustness and efficacy are more difficult to assess. Ecologists can contribute to the required expertise, and this can enhance levels of support. FURTHER A CULTURAL TRANSFORMATION Eco-engineering is a dynamic and flexible concept in which development is predictable but never entirely certain. Eco-engineering requires constant monitoring and agreements about how to manage this information, and who should take what action, and when. Management has to be organised differently than it would be for hard infrastructure. WHAT IS THE DELTARES ROLE? Eco-engineering requires a different approach to governance than traditional hydraulic infrastructure. Deltares identifies the technological and ecological expertise required during the governance process to make success more probable in both the design and the management phases. Deltares has acted as a consultant on projects in, for example, the Netherlands, Europe and Singapore. For more information: stephanie.janssen@deltares.nl

5 DELTARES, JANUARY Earning models make eco-engineering more successful A lot of hard work is going into the development of a range of earning models for eco-engineering. That will make it possible to decide, for a particular location, what value the concept has, and for whom. This is a good way of generating support but it also makes clear who will be prepared to invest in a concept. BY CARMEN BOERSMA An earning model sounds very businesslike. It is not something we tend to associate with a concept like eco-engineering, where social values like flood protection and ecology predominate. Even so, an earning model for eco-engineering has proved necessary. In some countries, eco-engineering projects got bogged down after enthusiastic starts. Researchers found that ecoengineering is bound to fail in some places unless the local economic impact is taken into account. Mangroves An example is the restoration of mangrove forests, which are disappearing rapidly in many countries. This represents a major setback for the ecological system, but natural coastal protection is also disappearing. As a result, there is considerable enthusiasm worldwide, particularly among environmental organisations, about restoring our mangrove forests and a large number of projects have been launched. However, these projects are unlikely to be successful if they lack the support of the local population. For them, cutting down mangrove forest is a source of income because the prawn and fish ponds that replace the forests, or the associated charcoal production, generate employment. Restoring the forests can threaten their livelihoods. So successful restoration depends on explaining how they can exploit the mangrove forests sustainably and how restoration can be reconciled with making money. Economic viability Maaike van Aalst, a researcher with Deltares: Taking the economic interests of the local population into account makes it more likely that eco-engineering will be successful. That is why it is so important to think in terms of earning models. It allows you to identify the value of the concept, who it helps, and what they can earn from it. Eco-engineering is more likely to be successful when it is also economically viable. That sounds very businesslike but it is actually about defining the social relevance of a project. An earning model also makes it clear which private investors will find the concept appealing, an important aspect now that many governments are tightening the purse strings. This is an interesting tool, particularly for companies who want to make socially responsible investments. It gives them a better picture of the return on their investment. For more information: maaike.vanaalst@deltares.nl

6 14 DOSSIER BUILDING WITH NATURE EXAMPLES OF 'BUILDING WITH NATURE Building with nature comes in many shapes and forms. In principle, it is feasible anywhere: urban or non-urban settings, rivers or coasts, large or small spaces Eco-concrete Modern concrete is becoming much smoother, and so it is much less amenable as a habitat for many marine animals that like hard sub-surfaces. Eco-concrete can be a solution. It has a special texture that allows organisms such as algae, seaweed, periwinkles and mussels to colonise it more easily. A pilot study has shown that ecoconcrete with a rough surface will be covered much more quickly by algae than smooth concrete and that mussels and periwinkles prefer it. On top of the ecological benefits, eco-concrete also makes water cleaner and clearer because the mussel colonies filter the water. 1. Pile hula Concrete columns, which are found in many ports, are very useful for what we have called pile hulas. These are nylon strips that look like Hawaiian skirts when they are attached to columns and piles. In almost no time, they are colonised by mussels, barnacles and a range of algae. A pilot study in Rotterdam harbour showed that an average of 8.5 times more biomass is found on the pile hulas than on ordinary piles. These shellfish also improve water quality because they filter the water to collect food. 2. Pontoon hula This is a variation on the pile hula. It is a floating structure made from PVC that can be used in harbours. Ropes hang down from it that, as with a pile hula, are rapidly colonised by a range of organisms that filter the water and improve water quality. Trials in the Delta Flume at Deltares have shown that the pontoon hulas are also excellent structures for damping reflection waves in harbours. 3. Rich dike Simple and cheap changes to hard structures like dikes, piers and dams can be used to retain water in higherlying parts of intertidal areas, resulting in an enormous boost for local biodiversity. This makes it possible to create pools at the foot of the dike without affecting flood prevention. Birds and other marine animals feed on the organisms in the pools, which also enhance the recreational and educational value of the area.

7 DELTARES, JANUARY PHOTO: DIRK HOL 6. Forebanks River forebanks with vegetation break waves. Fields with willows in front of dikes mitigate wave impacts and so the dike does not need to be as high. Studies have shown that a strip of willows one hundred metres wide can reduce the height of onemetre-high waves by 80%. Dikes protected in this way can be much lower and they can be covered in clay rather than rock. So introducing vegetation to forebanks can prevent expensive dike upgrades and also enhance the natural and recreational value of these areas. PHOTO: RIJKSWATERSTAAT 7. Sand Motor Sand replenishment can be combined with natural forces to maintain a sandy coastline and protect the hinterland from flooding saw the launch of the pilot study the Sand Motor between the Hook of Holland and The Hague. It will look at the efficacy of mega-replenishment. This sustainable approach requires less sand and gives the ecosystem more time (approximately 30 years) to recover. The Sand Motor is a flat sand bank containing a dune lake. The excess sand is gradually distributed by the currents and tides, and the lake provides additional natural diversity. That maintains the natural coastal defences, and provides more openings for nature and recreation. If the mega-replenishment principle works, it can also be used in other locations. 5. Oyster reef Instead of using hard structures like breakwaters made from rock or concrete blocks, we can also introduce natural elements like shellfish that form reefs and mitigate erosion. Three large synthetic oyster reefs were built in 2010 in the Eastern Scheldt. The reefs are nongalvanised steel cages filled with the shells of dead oysters. It has been found that new oysters colonise the reefs quickly and that the amount of sludge behind the reef increases. The iron cage soon rusts away and the oysters then provide the required stability. Laboratory measurements have demonstrated that the structures damp waves in shallow water. Similar techniques have been used in the United States to restore oyster reefs on a large scale. 8. Mangroves Mangrove forests are natural coastal defences and valuable ecosystems. Even so, they are rapidly being lost worldwide, particularly to make room for fish ponds. Traditional hard structures are being built to offset the resulting coastal erosion and to improve coastal protection. However, on muddy terrain, these structures are neither sustainable nor effective because they subside so quickly. As a result, a range of pilot projects have been launched to restore mangrove forests. Coastal erosion can be prevented by, for example, building berm structures from natural materials in front of the coast, catching sediment and restoring the natural conditions in which mangrove forests can grow again, and protecting the coast once again in a natural way. The valuable ecosystem can also recover. WANT TO KNOW MORE? For more applications and cost/benefit analyses, see 'Ecoengineering in the Netherlands. Soft interventions with a solid impact', published by Deltares and Rijkswaterstaat: ecology/

8 16 17 THE MULTIFUNCTIONAL DIKE NOW Buildings Houses are built close to dikes to make the most of space in cities. Foreshore Sheep and cows can graze on the foreshore and there is room for recreation. Dike houses The houses have been built next to the dike because of the access road. So there is limited room to strengthen the dike. The only options are structural measures or the demolition of the houses. Road Roads allow traffic to flow in cities. DIKE FUNCTIONS The primary function of dikes is to prevent flooding. But for centuries, they have also had other functions. Sheep graze on them and they are used for recreational activities. Houses are built alongside them and we also build roads on them. Sea-level rise, increased river discharge, land subsidence and new standards mean that flood protection needs to be improved in many areas. However, upgrading flood defences frequently gives rise to public opposition. Local people fear that the quality of their living environment will be adversely affected. This constitutes a major challenge for local managers.

9 AND IN THE FUTURE Closer to the water The robust upgrading of a dike makes it possible to build closer to the water. Wide foreshore Widening the foreshore creates a more attractive recreational area. There is more room for nature development and facilities for leisure activities are possible. Stronger foreshore The willows growing on the foreshore break the waves and so the dike does not need to be so high. An additional layer on the dike makes it possible to build houses on it. Jack-up houses New and old houses on and beside the strengthened dike can be built on jack-up lines in order to meet the challenges of the future. Should climate change or other standards make it necessary, they can be jacked up to allow the dike to be strengthened. City park Green areas can be planted to replace the road, upgrade natural value and extend recreational opportunities in towns. More green areas are also a good way of counteracting heat stress, and they ensure better drainage of excess rainwater. Road in the dike Building the road in the dike instead of on top of it creates space for a city park. The outer wall of the tunnel is strengthened, and it keeps out the water. CREATIVE USE OF DIKES The answer to this challenge is a more creative approach to the opportunities afforded by dikes. It is precisely when we make our flood defences stronger and wider that we can do much more than the simple, familiar things that we have been doing for centuries. This makes it possible to kill two birds with one stone: flood protection can be improved for the long term and broad public support can be achieved as the quality of the living environment will improve significantly. Car park The tunnel provides access to an underground car park in the dike. DELTARES/DESIGN: FRÉDÉRIK RUYS Innovative, multifunctional dikes can cope with future challenges and they ensure that we make the most of the available space, which is at a premium in delta areas. More space becomes available for recreational and residential purposes, both in urban and rural areas. Dikes are no longer barriers. They become part of the living environment, restoring the links with nature and water that so many local residents wish to see. For more information: ellen.tromp@deltares.nl