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Green-gray solutions

The effects of climate change are exacerbating the risks of coastal erosion and flooding. Green, nature-based solutions are emerging as cost-effective ways to mitigate those effects: natural ecosystems grow with their environment, and they provide dynamic solutions with long-term resilience. This contrasts with gray infrastructure, which is typically hard and static.

The optimal solutions for coastal adaptation are likely to combine green and gray and therefore deliver synergies between the two. Integrating natural green designs in traditional gray infrastructure not only improves long-term system resilience but also delivers numerous benefits for people and nature.


Flood risk management
Green elements can cost-effectively protect coastlines and deltas from flooding and erosion. They are more resilient than traditional gray infrastructure and better at coping with future uncertainties such as sea level rise. Nature-based solutions are easily adaptable to changing environmental conditions, and maintenance and repairs therefore can be cost effective.

Nature and economy
Green-gray solutions provide critical habitats for numerous plant and animal species. In addition to the boost for biodiversity and productivity, a healthy ecosystem can also store carbon below the ground for centuries.
Natural infrastructure can absorb pollutants and release oxygen, significantly improving air and water quality. Green-gray solutions also support economies and wellbeing by making the area more attractive for residents and visitors.

The most effective green-gray solutions for coastal protection in urban areas are tailored to the specific local conditions and needs. This may involve factors like the local climate, topography, and hydrology, as well asthe social and economic context. We aim to prioritize solutions that serve multiple functions and therefore maximize the benefits.

It is vital to take long-term adaptive management and maintenance into consideration. A sound scientific approach and close collaboration with stakeholders are the keys to achieving results. Green
solutions are often more dynamic due to their natural characteristics. Continuous monitoring during the design, construction and operational phases will help deliver effective adaptive management strategies.

We have completed a range of green-gray projects around the world: the construction of offshore ecological breakwaters, dikes with integrated foreshores, artificial reefs, sandy foreshores with integrated natural dune systems and wetland restoration.

In the Netherlands, we have worked on pioneering projects, such as the widenedgreen dike in Delfzijl and a sandy reinforcement of the Houtrib dike between Lelystad and Enkhuizen. And in the Noordwaard, where a willow forest was planted in front of the dike to reduce wave impact.

The collaborative approach that Boskalis promotes is essential for the success of green- gray given the involvement of stakeholders with different interests and perspectives. With NGOs, knowledge institutes and
engineering consultants, and public and private stakeholders, we test and research green-gray nature-based solutions for coastal and delta resilience, ecosystem restoration and sustainable port development. We also work with local communities and stakeholders to build the consensus that is vital for long-term success and sustainability. We collaborate with the World Bank and other financial institutions to identify opportunities and maximize the benefits of sustainable investments for people and nature.

We have the skills and resources to design and implement effective and sustainable green-gray coastal infrastructure projects for your project. We can help you with your specific needs and goals by providing project management services, including the oversight of construction activities and close coordination with communities and stakeholders.

Project highlights

Houtribdijk Juni 2021 FF112266

Houtrib dike

Boskalis Nederland Markermeerdijken C3de2cee Acec 4535 B02a Db7ca4c2fdea (66)

Markermeer dikes

The Markermeer dikes are part of the Zuiderzee dikes that have protected the hinterland from the former Zuiderzee and the present Markermeer lake for centuries. The dike reinforcement is necessary because more than 30 kilometers of the dikes no longer meet the standards for water safety, while about 1.2 million people live in the hinterland. The project is part of the national flood protection program.