Dyke upgrades and nature go hand in hand

The Flood Protection Programme (HWBP) is facing the challenge of upgrading 1,500 kilometres of dykes in the Netherlands within thirty years. Nature conservation and development are increasingly part of these upgrade operations. ‘Instead of restraining nature, we can use it to give us a hand,’ says Jorg Willems, Team Manager of Engineering, Knowledge & Innovation at HWBP. 

How has the role of nature in dyke upgrades expanded over the course of the years at the Flood Protection Programme?

‘There is an established history of using nature to work for us. A striking example is the 1980s Stork plan for the river area. Another is the change in the approach for the protection of the sandy coast, where we let the dynamic and natural processes work for us; the development of the Sand Motor and the ‘wandering’ dunes, for example. There was of course also the Room for the River programme at the start of the century. The river area is once again a focal point, as it represents a large part of our agenda in the Flood Protection Programme. There seems to be a renewed interest in combining flood risk management and nature development.’

What do you need to think about when you combine nature development and dyke upgrades?

‘Close-cropped grass is no longer the only option for vegetation on the dyke. You can add more variety. Water authorities are developing flower-rich dykes and introducing adaptive ways of cutting the grass instead of just letting sheep graze on the dyke.’

Deltares helps us to develop knowledge that doesn’t exist yet

Jorg Willems - Team Manager of Technology, Knowledge & Innovation at HWBP

What innovations are there for these nature-based solutions?

‘In the Wadden Sea – and possibly in other places – there are experiments with the natural reclamation of sediment. This approach raises the level of the area, protecting it better against sea level rise. In the Ems-Dollard area, sediment is dug up and used to strengthen the surrounding dykes. Studies are also being conducted to see how woods and soft wood can protect dykes against the action of the waves. These are wonderful ideas, but you have to assess them carefully because a nature-based solution can have an impact on water discharge or influx.’

Things have to be safe…

‘Certainly, and we do a lot of research on that: how safe are those nature-based solutions, and how does that relate to the safety standards in place? Together with several water authorities, Rijkswaterstaat, universities, and Deltares, we are looking at whether dykes will be just as strong as when they were covered with natural vegetation – or potentially even stronger. And perhaps this can be done in ways that are faster and cheaper. Instead of restraining nature, we can get it to give us a hand.’

Deltares involvement

Deltares is involved in the HWBP Dykes and Nature innovation project – a symbiosis. Operations in this project are led by the Drents Overijssels Delta water authority. A range of partners are looking at how flood risk management and nature (development) can go hand in hand and benefit from each other during dyke upgrade operations. For example, we are working in a Community of Practice with water authorities, nature organisations, and other parties and developing applicable knowledge about areas such as nature-based solutions for dyke upgrade projects.

What role does Deltares play and what do you expect from them?

‘Deltares has a range of roles, both in support for nature-based solutions and in the flood protection programme as a whole. They are knowledge carriers; they have a good overview of all the available knowledge, and a large network in the Netherlands and internationally. They are also knowledge developers, helping us to develop knowledge that is not yet available. Deltares also plays a role in setting the agenda, and they can advise us about where flood risk management and climate change are headed. That helps us to include the long-term effects in our projects. For example they helped our knowledge and innovation agenda, introducing more structure that looked towards the future. That is incredibly helpful, as we use the agenda to make an annual assessment of the innovation projects we want to finance and initiate. I see our cooperation as a co-production; that means you see new ideas and insights emerging with one another.’

What are the main challenges for the Flood Protection Programme?

‘We have to set and maintain the pace of dyke upgrades because the challenge is a daunting one: 1,500 kilometres of dyke by 2050. A large part of what needs to be done now is located in the river area and the Wadden Sea coast. These are primarily Natura 2000 areas. But we feel that the current nature and environmental legislation in these Natura 2000 areas does not stimulate nature-based solutions. It is very much aimed at preservation, whereas we would like to see dyke upgrades include more nature preservation and development. It is difficult to align this restrictive approach with the need to develop nature during dyke upgrade operations. It seems as if nature and flood risk management are seen as conflicting interests whereas this doesn’t have to be the case at all in practice. I think there are still a lot of opportunities that aren’t being exploited, and I would like to see better alignment in the future between what we envision, and between legislation and implementation. Nobody benefits if we damage our fragile natural environment. Natural and safe dykes must be our aim. I hope we can get the freedom we need to turn things around.’

What are your own feelings when you walk across a natural dyke?

‘Dykes have more and more functions; in addition to flood risk management, there is room for leisure activities, biodiversity, and experiencing nature. A dyke upgrade programme is quite an intervention in the landscape, with excavations and large machines at work. It’s a fantastic sight when you return a few years later and see that nature in the area has been restored. I have high expectations for the dyke upgrade projects that are currently in progress, such as the Meandering Meuse where dyke upgrades and local area development go hand in hand. Or the Zuiderzeeland water authority’s IJsselmeer Dykes project, where they are planning to create a shallow foreland in front of the dyke for natural development. Keep an eye on these projects and go visit them in a few years to see for yourself what has been developed there.’

Mangroves as part of coastal protection strategies for West Africa

Mangrove forests are found on sheltered tropical and subtropical coasts. The mangroves are home to multiple ecosystem services, critical to keeping coastal communities safe. They dampen waves and retain sediment. Deltares has worked on a project for the World Bank, studying the impact of mangroves as protection against erosion and coastal flooding in the West African coastal countries of Ghana and Guinea. Integrating mangroves into flood risk management strategies or climate change adaptation is relatively new. It requires sound impact studies beforehand, but also collaboration between different disciplines.  

Joshua Adotey (Africa Centre of Excellence / University of Cape Coast): “It is important to understand the social dynamics of the community as nature-based solutions are being designed to alleviate the challenge of perennial flooding and coastal erosion”. 

More information

Stephanie Janssen

Researcher resilience & planning