Emperor Naruhito visits Deltares: water as the foundation of Dutch-Japanese cooperation

The visit highlighted the role of the Dutch water sector in international cooperation and innovation. Hosted by Deltares, the Dutch applied research institute for water and the subsurface and a long-standing member of the Netherlands Water Partnership (NWP), the programme focused on how Dutch and Japanese organisations are working together to address shared water challenges. Opening the programme, Karremans pointed to 425 years of bilateral relations, now spanning fields from agriculture to high tech. Water management has been central to the relationship for over a century, he noted, with Dutch engineers such as Johannis de Rijke contributing to waterworks in Tokyo, Nagoya, Osaka and Kobe.

Deltares: where knowledge meets practice

Annemieke Nijhof, managing director of Deltares, introduced the institute as an independent research organisation with strong ties to the Dutch Government. The institute brings together experimental facilities, digital modelling and almost a century of knowledge to address pressures such as sea level rise, extreme rainfall, drought and energy transition. Their role, she argued, depends on a systems perspective that integrates knowledge across disciplines, government and industry.

The Dutch water sector's collaborative approach

This systems perspective reflects a broader feature of the Dutch water sector: close collaboration between government bodies, knowledge institutes and businesses, often described as the ‘golden triangle’. NGOs and civil society organisations are often part of this collaboration as well. This structure allows policy, research, and practical application to develop side by side, turning innovations into solutions that can be applied nationally and internationally.

This collaborative model is widely recognised as a strength of the Dutch water sector and forms the basis for many international partnerships facilitated through organisations such as NWP.

The visit to Deltares offered several illustrations of this model in practice. Bianca Peters, director of Partners and Clients at Deltares, presented three examples of how such collaboration creates impact at scale and helps address shared global challenges.

The first was Singapore’s Long Island project: a proposed 800-hectare land reclamation and coastal protection scheme being developed through collaboration between Singaporean and Dutch experts to strengthen flood resilience, enhance water security and adapt to sea level rise. The second was the Worldwide Storm Surge Barrier Network, now twenty years old. It connects operators of barriers such as the Thames Barrier and the Eastern Scheldt barrier with private companies and knowledge institutes such as Deltares, enabling them to learn from each other's experiences.

The third was JCAR ATRACE (Adaptive Transboundary Risk Assessment for Cross-border Extreme Events), a five-year programme on cross-border flood and drought management. It was launched in November 2023 by the Dutch Ministry of Infrastructure and Water Management and Deltares, following the severe 2021 flooding in Germany, Belgium and the Netherlands. Coordinated by Deltares, the programme brings together at least eight knowledge institutes from those countries and Luxembourg.

Peters pointed to recurring factors behind successful collaboration: shared responsibility, trust, a safe space for exchanging knowledge, and professionals genuinely engaged with a shared challenge. 

Learning from each other’s deltas

The Netherlands and Japan, both densely populated and shaped by water, increasingly draw on each other’s approaches as new pressures complicate traditional flood management. Deltares scientific director and TU Delft professor Bregje van Wesenbeeck noted during the programme that climate change and biodiversity loss are forcing both countries to revisit older, holistic approaches to managing water. Effective solutions, she said, tend to combine lessons from the past with an eye on the future.

Japan offers a long-standing example of this thinking. Centuries-old levee systems there were deliberately left open in places, letting floodwater spread into farmland rather than holding it back entirely. Coastal pine forests, known as Matsubara, were planted to soften the force of wind and waves. The Netherlands has been moving in a similar direction for two decades: since 2006, the Room for the River programme has created floodplains and retention areas instead of raising embankments further, giving rivers more space rather than holding them back. According to Van Wesenbeeck, both countries stand to learn from these older ways of giving nature room, as they face today's climate challenges.

Joint research with Japan

That mutual learning also takes a more practical form. One example is a joint research effort in Hokkaido, established in 2019 with Dutch and Japanese partners including Deltares, HKV, TU Delft and Rijkswaterstaat. The collaboration was prompted by shared experience with extreme events: three consecutive typhoons struck Hokkaido in 2016, while the Netherlands faced unprecedented flooding of its own in 2021. Researchers assess flood risk through a series of linked steps , from rainfall and river discharge to the failure probability of flood defences. The analysis draws on both Japan's River Basin Disaster Resilience framework and Dutch multi-layer safety principles. Delft-FEWS, an open-source flood forecasting platform developed by Deltares and used in more than seventy countries, is now being introduced into this research.

The visit also included a tour of several of Deltares' testing facilities. Here too, collaboration stood out as the common thread. The Eastern Scheldt storm surge barrier, tested at the Delta Flume on behalf of Rijkswaterstaat, is part of a broader knowledge network — the Worldwide Storm Surge Barrier Network mentioned earlier — through which operators around the world share experience. At the Atlantic Basin, Deltares' wave and current facility, researchers study how turbine foundations respond to waves, tides and currents under storm conditions. Floating wind, suited to deep waters such as those found off Japan, is a particular focus, and Deltares recently joined the Moonshot initiative of the Japanese Floating Offshore Wind Research Association.

A shared way forward

The lesson from the visit may be less about specific technologies than about how both countries think about water. As Van Wesenbeeck put it, the next challenge may lie less in additional engineering and more in restoring public trust in working with natural processes.That shift, the visit suggested, is one best made together.

The visit illustrated how the Dutch golden triangle continues to function in practice: government, knowledge institutes and businesses developing solutions together, tested at full scale and exchanged with partners such as Japan. As the challenges facing delta regions worldwide continue to grow, that model remains as relevant as ever.