Stand on the dike at Reiherstieg and look south across Wilhelmsburg, and you see an island in the middle of a reinvention. To the west, tower cranes mark the latest phase of a housing development designed to float during extreme floods. To the east, a stretch of parkland that was car parks and wasteland five years ago is now a network of shallow basins, rain gardens and permeable paths—a "sponge park" engineered to absorb the kind of downpour that would overwhelm conventional drains. Between them, on the rooftop of a former IBA exhibition building, rows of salad greens grow in hydroponic troughs fed by rainwater collected from the building itself.
Wilhelmsburg is Hamburg's largest Elbe island and, historically, one of its poorest districts. The catastrophic storm surge of February 1962, which killed 315 people in the city—most of them here—defined the island for decades. But since the International Building Exhibition (IBA) in 2013, Wilhelmsburg has been quietly transformed into what urban planners now call a living laboratory for climate adaptation.
Building for water, not against it
The traditional response to flood risk in northern Germany has been to build higher dikes and stronger barriers. Wilhelmsburg still relies on those—the dike line was raised and reinforced after 1962 and again in the 2000s. But the newer approach treats water as something to be managed rather than excluded.
The sponge-park concept, piloted in the Inselpark area in 2022, is a good example. During normal weather, the park looks like any other urban green space: lawns, trees, a playground, a skate area. During heavy rain, engineered depressions fill gradually, holding water that would otherwise surge into storm drains and, eventually, into the Elbe. The water infiltrates the soil over 24 to 48 hours, recharging groundwater and filtering out pollutants in the process.
"We designed the park so that people use it every day without thinking about flood management. That's the whole idea of sponge design—it works in the background until you need it, and when you need it, it works very well." — Dr. Anke Peters, landscape architect and lead planner for the Inselpark retrofit, HafenCity University
The numbers are encouraging. During the heavy rainfall event of August 2024—47 millimetres in three hours—the Inselpark area recorded no surface flooding, while adjacent streets served by conventional drainage saw temporary ponding up to 15 centimetres deep. The city's environment agency estimates that the sponge infrastructure reduced peak runoff into the municipal drainage system by 35 percent across the affected area.
Rooftop farming: more than a demonstration
On the roof of the IBA Dock, a floating exhibition hall moored in Müggenburger Zollhafen, an urban farm has been operating since 2023. It is modest in scale—roughly 400 square metres of growing space—but ambitious in intent. The farm grows leafy greens, herbs and microgreens using a closed-loop hydroponic system. Nutrients come from composted food waste collected from restaurants in the district. Water comes from filtered rainfall. Energy comes from the building's own solar panels.
The farm sells its produce to four restaurants in Wilhelmsburg and at a small weekly stand near the S-Bahn station. It is not commercially profitable—the operators describe it as "cost-neutral with volunteer labour"—but profitability is not the primary objective. The point is to demonstrate that rooftop food production in Hamburg's climate is technically feasible, and to generate data on yields, energy inputs and water use that can inform larger-scale projects.
Housing that expects to flood
Perhaps the most striking element of Wilhelmsburg's transformation is the new housing along the Spreehafen canal. Three residential buildings completed in 2024 were designed with what architects call "wet-proofing" at ground level. The ground floors are built with waterproof concrete, sealed electrical systems and no permanent fixtures below the projected flood line. In an extreme event, residents move furniture upstairs, the ground floor floods, and when the water recedes the space is cleaned and reoccupied without structural damage.
It is a pragmatic approach, born from the recognition that no dike system can guarantee absolute protection as sea levels rise and storm surges intensify. Rather than pretending the water will never come, these buildings accept that it might and plan accordingly.
The social dimension
Wilhelmsburg's climate projects have not been without tension. Long-time residents—many from immigrant communities who moved to the island when rents were low—have watched property values climb since the IBA. The concern is familiar from every urban renewal story: that the benefits of green investment accrue to newcomers while existing residents are priced out.
The district council has pushed for rent controls on publicly funded housing and for local hiring requirements on construction projects. Community gardens established during the IBA era have been protected from development by long-term lease agreements. But displacement pressure is real, and advocates argue that climate adaptation planning must include social equity metrics alongside environmental ones.
A model for other cities
Delegations from Rotterdam, Copenhagen, Gothenburg and several German cities have visited Wilhelmsburg in the past two years. What draws them is not any single technology but the integration: flood management, energy, food production, housing design and public space woven together in a single district, at a scale large enough to generate meaningful data.
Hamburg's environment agency is currently compiling the first comprehensive performance report on the district's climate-adaptation infrastructure, expected for release in late 2025. The hope is that the data will move the conversation from "interesting pilot" to "replicable model"—and that Wilhelmsburg, the island once defined by catastrophe, will be remembered instead for showing other cities what resilience can look like.