POP-UP

Climate change forces cities to construct massive underground reservoirs to protect against increasingly frequent cloudbursts. These storage facilities are necessary, yet they often lie unused for 363 days of the year, claiming space and resources without contributing to everyday city life. Meanwhile, urban growth and rising car ownership are intensifying parking shortages, with studies showing that up to 30% of inner-city traffic comes from drivers circling in search of parking.

POP-UP addresses these two challenges in a single move. By stacking water storage, parking, and public space in one footprint, it transforms what would otherwise be a hidden technical installation into an urban asset. Instead of choosing between stormwater protection and liveability, cities can achieve both, while gaining new public spaces and releasing land for development.

Developed as a speculative design and feasibility study, POP-UP was tested in case studies in Copenhagen and New York, investigating how stormwater reservoirs and parking structures could be combined in dense urban areas and help promote green mobility. The analyses demonstrated that the integrated approach is not only more space-efficient but also significantly more cost-effective than building reservoirs, parking, and parks separately.

The design concept is as simple as it is innovative: the parking structure is engineered like a buoyant cork that floats within the stormwater reservoir. On dry days, POP-UP functions like a conventional underground car park, seamlessly integrated into the street. When heavy rain falls, the water reservoir begins to fill, and the parking decks gently rise, breaking through the surface and maintaining safe access.

At full capacity during a 100-year storm, the structure reaches its highest position, secured by docking mechanisms. It becomes both a resilient safeguard and a striking silhouette in the cityscape. In this way, climate adaptation becomes visible and tangible, turning infrastructure into a shared civic experience.

This kinetic quality was central to the design studies carried out with COWI (engineering) and Rambøll (economics), which confirmed the technical feasibility of the floating structure and the economic benefits of land release. By making resilience visible and interactive, POP-UP reframes infrastructure as an urban performance, something the city can experience, not just endure.

Conventional planning treats stormwater storage, parking facilities, and parks as three separate demands on valuable land. POP-UP brings them together, multiplying value in the same footprint. This integrated approach frees up thousands of square meters that can be transformed into housing, commercial opportunities, or much-needed green space.

The result is a solution that is not only climate-resilient but also socially beneficial and financially sound. By reducing traffic congestion, creating space for nature, and enabling healthier communities, POP-UP demonstrates how design can turn challenges into opportunities. The project was presented internationally through the C40 Cities Climate Leadership initiative, highlighting its relevance for cities worldwide that face the twin challenges of flooding and congestion.

From Copenhagen to New York, London, Tokyo, and Rio de Janeiro, the concept shows how necessity can drive innovation, and how adaptation can generate new possibilities for urban life. POP-UP is not only about storage and parking; it is about reclaiming the city as a resilient, flexible, and liveable environment.