Speakers
Description
The subsurface is the invisible infrastructure of life, supporting ecosystems by filtering water, cycling nutrients, and sustaining biodiversity. Yet in urban environments, the subsurface is frequently degraded, sealed, and treated as residual space for infrastructure that is inconvenient to accommodate above ground. At the same time, urban soil and subsurface space are increasingly scarce resources subject to competing claims (Debrock, Van Acker & Admiraal, 2023). This reflects a broader challenge of functional differentiation: urban systems are organised into specialised domains—such as energy, water, mobility, spatial planning, housing, and ecology—each with its own responsibilities, expertise, priorities, and institutional arrangements. Such specialisation is deeply rooted in how modern societies organise and manage complexity, but it also fragments responsibilities and can hinder coordinated and resilient responses to increasingly interconnected social, technical, and environmental challenges (Grin, 2020).
Drawing on case studies in the Netherlands and Belgium, this paper investigates how actors navigate functional differentiation in practice and create connections across sectoral and institutional boundaries. We ask:
How can boundary-spanning practices support the transformation towards sustainable use of the urban underground and foster integrative urban planning in contexts characterized by functional differentiation and structural uncertainty?
Conceptually, we connect literature on boundary spanning and boundary work with insights from sustainability transitions on multi-system interactions, transition intermediaries, and system entanglers. Transition research increasingly recognises that sustainability transitions extend beyond the boundaries of individual socio-technical systems and depend on interactions between systems (Rosenbloom, 2020; Kanger et al., 2021; Andersen & Geels, 2023). This shifts attention from transforming individual systems towards breaking unsustainable couplings and creating or strengthening more sustainable ones.
Yet a focus on systems and their interactions risks losing sight of the actors and practices through which these connections are produced (Löhr & Chlebna, 2023). Boundary spanning draws attention to actors and activities that connect otherwise separated organisations, sectors, or knowledge domains (Slob & Duijn, 2014), while boundary work highlights how boundaries how actors create, maintain and reshape boundaries between groups and practices (Zietsma & Lawrence, 2010). These perspectives are complemented by transition concepts such as intermediaries (Kivimaa et al., 2019, Sovacool et al., 2020) and system entanglers (Löhr & Chlebna, 2023), which foreground actors who build networks, develop cross-sectoral competencies and shared visions, and forge technological, institutional, and policy connections across systems. Together, these literatures offer an agency and practice-oriented lens for examining multi-system innovation: how actors create connections across urban systems while navigating functional differentiation and associated uncertainty about changing system needs, interactions and future claims on urban space.
We further develop this perspective by focusing on incumbent actors involved in urban underground planning, and their role in spanning boundaries between differentiated systems. Incumbents are constrained by established institutional arrangements, sectoral responsibilities and ways of working, but may simultaneously possess the resources, expertise, mandates and institutional positions needed to build new connections across systems. This creates a central tension: actors seeking greater integration must work through—and reshape—the very differentiated structures that make integration difficult (Naus et al., 2026).
The empirical analysis draws on well-documented cases of cross-sectoral urban planning in the Netherlands and Belgium, complemented by additional interviews and a focus group discussion to validate and enrich the findings. The cases allow us to trace different pathways through which cross-sectoral collaboration develop over time, including the boundary spanning practices, conditions, critical moments and setbacks that shape these pathways.
The first case concerns the policy exploration Ondergronds Ruimtegebruik in Vlaanderen (“urban underground space use in Flanders”) by the departement of Environment and Spatial Planning Flanders, which examined the opportunities and challenges associated with the sustainable use of urban underground space in the context of increasing urban densification. By bringing together a broad and diverse range of stakeholders, interests, and sectoral perspectives related to the subsurface, the project highlighted the fragmented nature of underground governance and planning in Flanders. The exploration revealed the need for an integrated planning vision for the subsurface, capable of balancing competing sectoral claims, facilitating cross-sectoral coordination, and supporting the development of a shared strategic framework for sustainable urban underground development (Departement Omgeving, 2019).
A second case is the Koppelkansen (“Linking Opportunities”) initiative in Amsterdam, which brought together the municipality, energy grid operator Liander, and water utility Waternet to coordinate infrastructure planning across energy, water, and urban development. Rather than treating infrastructure interventions as separate sectoral projects, actors experimented with integrated design practices, new spaces for collaboration, and adaptations to established institutional arrangements. The case reveals how small but significant wins can be achieved, as well as the frictions, trade-offs and setbacks involved in enabling and sustaining such cross-sectoral transition work (Grin, 2020; Naus et al., 2026; Kemp et al., manuscript in preparation).
The third case examines the research-by-design project Designing from the Cross-Section: The Subsurface as a Building Block for a Future-Proof City (de Boer et al, 2022). The project is relevant due to its mandatory multidisciplinary collaboration between urban designers and subsurface experts, such as engineers and geologists. By mobilising diverse forms of expertise around a common design challenge, the project created opportunities for knowledge integration, collective learning, and the development of shared understandings of above- and below-ground interactions. Key insights from the study include the importance of visualisation in establishing a common language across disciplines, the provision of shared platforms and reliable subsurface data to support knowledge exchange and collective learning. Together, these elements support the crossing of disciplinary, sectoral, and institutional boundaries, fostering more integrated and multidisciplinary approaches to urban underground design.
Through analysis across cases relating to the subsurface, we identify different pathways through which actors connect differentiated systems and deal with uncertainties, focusing on boundary-spanning actors, concepts and practices, as well as the conditions that enable or constrain their development. In doing so, the paper contributes to understanding how multi-system interactions are actively produced and evolve in practice, and how interventions at the intersections of systems may generate wider transformative effects. Empirically, this provides insights into possible pathways through which the urban subsurface can shift from being treated as residual space contested by individual sectors towards being governed as a shared, multifunctional and living space that supports urban resilience.
References
Andersen, A. D., & Geels, F. W. (2023). Multi-system dynamics and the speed of net-zero transitions: Identifying causal processes related to technologies, actors, and institutions. Energy Research & Social Science, 102, 103178. https://doi.org/10.1016/j.erss.2023.103178
Boer, Hans de, Shana Debrock, Marleen Duflos, and F.L. Hooimeijer. 2022. ontwerpen vanuit de doorsnede: de ondergrond als bouwsteen voor de toekomstbestendige stad. Mechelen: Public Space.
Debrock, S., Van Acker, M. & Admiraal, H. (2023). Design recommendations for sustainable urban underground spaces. Tunnelling and Underground Space Technology, 140, 105332, https://doi.org/10.1016/j.tust.2023.105332.
Departement Omgeving. 2019. “Beleidsverkenning: Onder Onze Voeten Ligt Een Wereld Aan Kansen.” Brussel.
Grin, J. (2020). ‘Doing’ system innovations from within the heart of the regime. Journal of Environmental Policy & Planning, 22(5), 682–694. https://doi.org/10.1080/1523908X.2020.1776099
Kanger, L., Schot, J., Sovacool, B. K., van der Vleuten, E., Ghosh, B., Keller, M., Kivimaa, P., Pahker, A. K., & Steinmueller, W. E. (2021). Research frontiers for multi-system dynamics and deep transitions. Environmental Innovation and Societal Transitions, 41, 52–56. https://doi.org/10.1016/j.eist.2021.10.025
Kemp, R., Grin, J., Hordijk, M., Goldschmeding, F., Naus, J., & Vasseur V. (manuscript in preparation) In search of the Wholly Grail. Transition work by incumbents in cross-sectoral projects supported by action research.
Kivimaa, P., Boon, W., Hyysalo, S., & Klerkx, L. (2019). Towards a typology of intermediaries in sustainability transitions: A systematic review and a research agenda. Research Policy, 48(4), 1062–1075. https://doi.org/10.1016/j.respol.2018.10.006
Löhr, M., & Chlebna, C. (2023). Multi-system interactions in hydrogen-based sector coupling projects: System entanglers as key actors. Energy Research & Social Science, 105, 103282. https://doi.org/10.1016/j.erss.2023.103282
Naus, J., Grin, J., & Hordijk, M. (2026). Cross-sectoral transition work at the heart of the regime: Transforming incumbent systems in utility infrastructure planning in Amsterdam. Environmental Innovation and Societal Transitions, 60, 101125. https://doi.org/10.1016/j.eist.2026.101125
Rosenbloom, D. (2020). Engaging with multi-system interactions in sustainability transitions: A comment on the transitions research agenda. Environmental Innovation and Societal Transitions, 34, 336–340. https://doi.org/10.1016/j.eist.2019.10.003
Slob, A.& Duijn, M. (2014). Improving the Connection Between Science and Policy for River Basin Management. In Risk-Informed Management of European River Basins (pp. 347–364).https://doi.org/10.1007/978-3-642-38598-8_13
Sovacool, B. K., Turnheim, B., Martiskainen, M., Brown, D., & Kivimaa, P. (2020). Guides or gatekeepers? Incumbent-oriented transition intermediaries in a low-carbon era. Energy Research & Social Science, 66, 101490. https://doi.org/10.1016/j.erss.2020.101490
Zietsma, C., & Lawrence, T. B. (2010). Institutional work in the transformation of an organizational field: The interplay of boundary work and practice work. Administrative Science Quarterly, 55(2), 189–221. https://doi.org/10.2189/asqu.2010.55.2.189