The delta strategy for Rijnmond-Drechtsteden has been designed to extend through approximately 2070. And after that? Commissioned by the IABR, PosadMaxwan, De Urbanisten, and H+N+S conducted a design study to map out the long-term prospects for water safety in relation to socio-spatial-economic developments. The study assumes a temperature increase of 2.5 degrees and a sea-level rise of up to two meters.
If there is one place where the clash between our globalized economy and planetary boundaries will play out in all its administrative complexity, it is the Rijnmond-Drechtsteden region, where the major rivers flow into the sea alongside the sprawling port complex. That port complex accounts for about 3.2 percent of the Dutch GDP; tens of thousands of ocean-going and inland waterway vessels pass through it each year. Water flows into this area from four directions: the sea, the rivers, the air (precipitation), and the ground (seepage).
The consequences extend beyond sea-level rise and water safety issues. They also include extreme high and low tides, salinization, increasing drought, and threats to freshwater availability, as well as clustered downpours during the “wrong” season. Environmental and water safety issues are so intertwined with the region’s socio-spatial-economic functioning that they can be distinguished but not separated.
Adaptation measures will eventually require far-reaching spatial adjustments with significant economic, social, and ecological impacts, particularly in urbanized areas outside the dikes and in the port complex.
Two Future Strategies
The spectrum of approaches to long-term adaptation to sea-level rise reveals that “Protect-Closed” versus “Protect-Open” is the first key decision point: an open or a closed estuary. A spatial translation has been developed for both approaches, resulting in two future strategies: “Polder,” developed by De Urbanisten, and “Estuarien,” developed by H+N+S Landscape Architects.
Polder
The polder strategy offers clear-cut flood protection in line with the Dutch tradition of hydraulic engineering, but ultimately implies parting ways with the open harbor. The harbor complex will undergo a radical reorganization, while the areas outside the dikes in Rotterdam and Dordrecht will become safe, and attractive opportunities for waterfront urbanization will emerge.
Estuarine
The estuarine strategy keeps the harbor connection open and relies on natural processes of gradual expansion. It is an ultra-long-term perspective that buys time and space to achieve safety at a lower cost. From an urban perspective, it requires locally tailored solutions; from an ecological perspective, the estuarine approach provides nature that ultimately protects us.
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Assessment Framework
Based on future scenarios, PosadMaxwan developed an assessment framework to evaluate both strategies in terms of their spatial, economic, and social implications, and to identify opportunities and risks. The scenario model is structured around three axes: the scale of governance (global versus regional), the direction of economic development (growth versus decline), and the degree of social responsibility (high versus low). Together, these axes generate eight future scenarios—none of which is inherently more likely than the others—that serve as a framework for evaluating the two water safety strategies.
The implications were assessed across seven themes: ports and logistics, population and cities, energy transition and the circular economy, landscape and nature, agriculture and horticulture, freshwater demand, and investments in water safety. For each scenario and theme, an assessment was made of the direction, magnitude, and feasibility of the impact, summarized through three lenses: spatial, economic, and social. The assessment framework makes the complexity of the implications manageable for policymakers; however, it does not provide a judgment as to which strategy is “better.”
The picture that emerges is more nuanced than the “open or closed” choice suggests. The closed polder strategy is more straightforward in terms of governance and investment, but concentrates an enormous impact over a short period and is not sustainable in the very long term. The open estuarine strategy requires long-term, coherent governance and investment across a much broader front, with greater adaptation, but it also buys considerably more time. Both strategies require continuity and safeguards: political, financial, and social. This raises the question of whether such safeguards can be enshrined in a way that transcends the political cycle.
Global Context
Parallel to the water safety challenge, a second urgent issue is emerging: the economic and geopolitical position of the Netherlands. The Rijnmond-Drechtsteden region operates in a global context where those who aren’t at the table end up on the menu. Large-scale investment in innovation is necessary—and it must be structured so that the benefits remain here and do not go elsewhere. This directly affects national sovereignty, quality of life, and, consequently, social cohesion. This interest, too, demands continuity and long-term investment.
The big question is how to reconcile the water safety challenge with the economic challenge. Both require decades of consistency in policy and funding; both transcend the political issues of the day. The answer begins with a new national narrative that connects these challenges. That narrative cannot wait. The choices that will make it possible demand our attention now.
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Adaptation Pathway Map
The regional adaptation pathway map further elaborates on the interconnections, identifies decision points and tipping points, and takes into account social preconditions as well as economic and port-related challenges. Unlike typical adaptation pathway maps, which are limited to water-related interventions, this map also provides insight into the broader social and economic complexities.
The polder strategy concentrates extensive infrastructure projects into a relatively short period. The estuarine strategy develops more gradually but requires a much more extensive social transition and societal acceptance. Switching from an open to a closed system is technically possible but abrupt and disruptive; the reverse is not realistic in practice. This makes the sequence of decisions itself a strategic choice.
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The Rhine-Mouth/Drechtsteden Delta Program
The research results serve as a building block for the policy preparation of the recommendation that the Administrative Regional Consultation Body will submit to the Delta Commissioner regarding the revision of the current Preferred Strategy of the Rhine-Mund-Drechtsteden Delta Program (DPRD).
The three preliminary studies make it clear that strategic decisions regarding water safety, land-use planning, and port organization are closely interrelated and have far-reaching implications. At the same time, no irreversible decisions need to be made during this DPRD policy period.
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