A Look Behind The Scenes At The Dike Of The Future

With its theme of 'Seeds of Change', the Water Conference in New York is inviting the world to think about innovative water management solutions. As always, the Netherlands continues to develop smart and sustainable dike reinforcement solutions with the goal of making the dikes seamlessly blend in with their surroundings. One example of this is the 'Strong Lekdijk' project, devised by the De Stichtse Rijnlanden Water Board as part of the national High Water Protection Programme. Read on to discover how an innovative partnership can achieve the transition to emission-free dike reinforcement while simultaneously enriching the natural environment and creating new opportunities for recreation.

Anyone who gets a chance to take a closer look at the work in progress on the Lekdijk is in for a series of surprises. In one powerful motion, the mid-sized crawler excavator of innovation partner and contractor Mourik Infra, bites into the floodplain, removing a substantial chunk of earth. This will later be used to reinforce the first few kilometres of the Salmsteke subproject. The first surprise is that this impressive machinery is powered entirely by hydrogen. A little further along, a section of recycled plastic dam wall rises out of the sand. This is excellent news for nearby residents, as the amount of vibration and other disruption caused by this material, is much lower than when heavy steel dam walls are used.

High Water Protection Programme

These are shining examples of the innovative solutions that are currently being used to reinforce a section of the 55-kilometre Lekdijk. One of the oldest dikes in the Netherlands, the Lekdijk protects over a million people from the water, including the residents of Utrecht and Amsterdam. Safeguarding these flood defences is the core task of the 'Strong Lekdijk' project. While the Lekdijk is already a strong and extremely reliable dike, this project is vital to ensure it remains this way, far into the future.

With stricter legal requirements in place, based on the latest dike-safety knowledge, over 1500 kilometres of dike have now been strengthened, all over the country. The water boards and Rijkswaterstaat (the Directorate-General for Public Works and Water Management) are executing these duties via the High Water Protection Programme, which is also the principal source of funding for the 'Strong Lekdijk' project.

Program Director Leon Nieuwland of the De Stichtse Rijnlanden Water Board (left) and Reinoud van Oosten, Managing Director of Netherlands RPS. In the background, you can see the first contours of the recreational areas in the floodplains.

Challenges

Every single country in the world faces challenges concerning water, be it flooding, extreme drought or access to clean drinking water. "For this reason, it is vital that the UN's Water Conference brings these themes to the attention of the world and encourages countries to take action," says Reinoud van Oosten, Managing Director of Netherlands RPS. Having commissioned and directed the contracting firm Mourik Infra, we have been very active on the 'Strong Lekdijk' project in the areas of dike reinforcement, natural and recreational floodplains and conditioning research.

Program Director Leon Nieuwland of the De Stichtse Rijnlanden Water Board, the body responsible for water management in the region, agrees. He reminds us of the most recent flooding in the Netherlands, Belgium and Germany, which claimed a number of lives. Calculations by the UK-based aid organisation Christian Aid showed that it was the second most expensive natural disaster in the world in 2021. "We have also observed major subsidence, that affects CO2 emissions but also has consequences for water safety. It will also affect groundwater: how are we going to ensure sufficient drinking water as well as ensuring the agricultural sector has the water it needs? These are serious challenges that are currently facing us."

Multiple goals

Van Oosten also mentions the lack of available space to take effective anticipatory measures with regard to climate change. However, at the same time our population density is increasing and other factors are also putting pressure on any available space. "As a result, it is even more important that we work together intensively and wisely, in order to achieve multiple goals via the same project."

"By doing so, we think carefully about the existing water system, the spatial planning and the properties of the ground," adds Nieuwland.

The Lekdijk project will have to answer all of these challenges. The goal is to seamlessly integrate the first section of the dike reinforcement (the Salmsteke subproject) into the landscape and the surrounding area. "This reconstruction must develop both the natural environment and recreation facilities, as well as honouring the culture and history of the dike," explains Nieuwland. On this project, this will be completed at an early stage by collaborating with regional partners such as Rijkswaterstaat, which is responsible for the river and floodplains.

Van Oosten: "We will achieve the best possible solution by working together on an integrated design for the dike reinforcement and redevelopment of the floodplains. In this way, we will redesign the floodplains to introduce a side channel, natural grasslands and swamps, a swimming pool, a new boat ramp and catering facilities. We will also make the area more accessible for walking."

Hard work is being done to exploit recreational uses (photo: Mourik Infra)

Voyage of discovery

While this may sound great, it will be difficult to pull this off with limited space available, and the residents that live nearby wouldn’t exactly be happy about more land claims. "It's a voyage of discovery," says Nieuwland. "From the beginning, you must emphatically seek their involvement from the very start of the design and execution phases. It's also vital to immediately get around the table with all chain partners involved, such as energy companies, grid managers, contractors and engineering firms."

During this project, the water board will also strive to achieve complete emission-free dike reinforcement by 2029. In order to run as tight a ship as possible, the De Stichtse Rijnlanden Water Board decided to divide the project up into six sub-projects. During the planning, development and execution phases, it will also break from tradition, as the Water Board issues instructions and the contractor carries them out.

With this type of partnership, you are purchasing something that is not yet readily available on the market. Therefore, a process of development will first be required. In the case of the Lekdijk, this means innovative dike technology, developed at the pilot level but not yet applied on a large scale.
One example of such technologies is the Prolock Delta Filter Screen.

These plastic dam walls allow seepage water through, but at the same time prevent the sand under the dike from being washed away (piping), to ensure stability. The vertical installation means the screens take up very little space and it limits the impact on the surrounding area. The operating principle of this solution holds firm, regardless of the river water level or rises in the sea level. This makes it more resistant to climate change, peaks in floods and any other changes in the future.

Building with nature

This partnership is also devising highly inventive solutions to create natural barriers against the water. Examples of such barriers include podzol ground a type of soil group, which has excellent protective qualities thanks to their almost impenetrable structure. In the Netherlands, such grounds are mainly found in sandier landscapes.

The partnership has developed a new natural product named SoSEAL, which artificially mimics the characteristics of podzols. SoSEAL is made of broken-down plant residues and a salt solution containing aluminium ions, which converts the natural organic matter into minuscule flakes.Therefore, the ground no longer needs to be dug to protect against seepage water and piping, which in turn means the dike will remain fully intact.

"The principle of 'building with nature' is immensely powerful," says Nieuwland proudly. "This should predominantly be done by learning from the local history of the region. How did the subsoil form thousands of years ago? How did people deal with river channels in those days? You can then add innovative applications to the existing landscape.

Van Oosten indicates an area further along with a channel, where reeds are being cultivated as well as adding rockfill. "The reeds will be given the opportunity to grow and develop for two years, at which point they will be strong enough to prevent erosion and provide natural dike protection," he explains. This solution will have a positive effect on biodiversity.

The reeds will also help reduce pressure on the dike, as they move the entry point for piping further away from it. In addition, the contractor Mourik Infra will implement a bentonite mat, also known as a Geo Clay Liner, into the floodplain. Bentonite mats enable the use of soil that is native to the region but is less erosion-resistant. As a result, no more clay needs to be purchased and transported from other regions, which substantially boosts energy efficiency.

Examples of the recycled plastic Prolock Delta Filter Screens that allow seepage water through as well as preventing the sand under the dike from being washed away (piping) to ensure stability is maintained.

Emission-free dike reinforcement

Speaking of sustainability, it's also important to note that the transition to emission-free methods cannot happen overnight. The innovation partnership is stimulating innovation, to strive for fully emission-free dike reinforcement. So what exactly can the partnership do in order to achieve this?

Van Oosten says, "The first step is to use smarter calculations to keep a close eye on exactly what you need, in order to cut out unnecessary work. You can also use a soil-based design to examine exactly what you can do with the resources already available in the area. For example, at RPS's geotechnical laboratory, we analysed the erosion-resistant properties of the clay produced from digging the channel in the floodplain.
The next steps are then all about smart design, application and emission-free execution whenever possible.

13,500 cubic metres of earth

For this final step, you need contractors with the determination to innovate and invest. One such contractor is construction company Mourik Infra. In addition to co-developing the plastic dam wall, their in-house development team also converted a crawler excavator to function entirely on hydrogen power. This excavator can be operated for at least eight hours per day.

The use of emission-free material, such as this hydrogen-powered excavator belonging to Mourik Infra, has reduced CO2 emissions by 93% compared to traditional fossil-fuel based methods (photo: Mourik Infra)

Within the 'Strong Lekdijk' project, contractors have the opportunity to develop innovative solutions and trail them practically. The investment required for this innovation can be written off over the six-year course of the project. And Mourik Infra is not our only contractor that is consciously focusing on the environment. Innovation partner Van Oord is also bringing its electric hydraulic excavator to the party.

After one year, the project has proved that this strategy is taking us in the right direction. The reuse of more than 13,500 cubic metres of soil to reinforce the dike has removed the need for 675 lorry journeys. The use of emission-free material has reduced CO2 emissions by 93% compared to traditional fossil-fuel based methods. "Of course, our ultimate goal is 100% reduction but thanks to programmes like this, we will undoubtedly continue to develop." says Nieuwland.

Investing in relationships

Van Oosten says that this clearly proves the power of the innovation partnership. "As all parties -engineering firm, water board and contractors- are tackling this subproject together as part of an integrated strategy, we are able to capitalise on these opportunities to eliminate emissions. When all stakeholders share responsibility for the solutions and results, everyone is capable of so much more. For example, we have shown that it is even possible to create a design that will lower the water level by 3mm. This may not seem like much, but it really does make a difference."

A successful innovation partnership requires deep collaboration and it is vital to be transparent about and vigilant for any differences of opinion, and raise these issues. According to Nieuwland, understanding one another requires investment upfront. "All interests, even uncomfortable ones, must be clearly stated. Only then can one understand why people make the decisions they make, which enables them to take action. By developing and embedding knowledge together, the partnership becomes more sustainable. It may take some time and effort at first, but ultimately this will pay for itself."

Safe environment

According to Van Oosten, innovation necessarily involves the realisation that not everything will work. For this reason, social innovation is at least as important as product innovation. The key is to create a safe environment in which transparency is nurtured and everyone can progress together. "You have to strive for a business culture, where everyone encourages each other to keep going despite any setbacks and to address each other's behaviour. That's what leadership is all about."

"Every day, our programme manager hammers home that making the innovation partnership work is a choice that we all make," adds Nieuwland. At that moment, in one powerful motion, the excavator takes a final mouthful of earth out of the floodplain. Whatever happens, this crane driver certainly won't let the side down.