Obsolete Stadt - Raumpotenziale für eine gemeinwohlorientierte, klimagerechte und koproduktive Stadtentwicklungspraxis in wachsenden Großstädten

Overview of the Project and Its Origins

The initiative “Obsolete Stadt – Raumpotenziale für eine gemeinwohlorientierte, klimagerechte und koproduktive Stadtentwicklungspraxis in wachsenden Großstädten” is a research project funded by the Robert Bosch Stiftung (2020‑2023). It is coordinated by the Institute of Urban Planning at the University of Kassel (Prof. Stefan Rettich, Dipl‑Ing. Sabine Tastel) together with the Helmholtz Centre for Environmental Research (UFZ, M.Sc. Anika Schmidt) and the Social Urban Design competence centre at Hochschule Niederrhein (Prof. Nicolas Beucker, B.A. Clemens Brück). The research team also includes specialists from various disciplines, reflecting a transdisciplinary approach to urban transformation.

Scope and Geographic Focus

The study investigates urban obsolescence in large German cities, primarily Hamburg and Hannover. It maps and analyses buildings and land parcels that are becoming underused due to megatrends such as digitalisation, the traffic transition, and changing religiosity. The research identifies 24 prospective “potential spaces” in Hamburg where obsolete structures could be repurposed for climate‑friendly, community‑oriented development.

Methodology and Data Sources

Content was extracted verbatim from a 44.3 MB report and supplemented with GIS‑based inventories, georeferenced data, and expert interviews. The team created a taxonomy of obsolete building types (e.g., big‑box retail, office blocks, parking facilities, churches, cemeteries) and assessed their transformation potential using three categories: functional retention, adaptive reuse, or demolition. Quantitative forecasts estimate reductions such as a 10 % decrease in motorised individual traffic in Hamburg by 2030, translating into roughly 73 ha of freed parking space.

Key Quantitative Findings

• Projected decline of bank branches by 42 % and retail floor space by up to 13 % by 2030.
• Anticipated reduction of parking areas by 10 % (≈ 73 ha) and tank stations by 33 % due to electric‑vehicle uptake.
• In Stellingen, 75 obsolete sites were catalogued, covering 2.5 ha of mixed‑use potential and 2.5 ha of green‑infrastructure opportunities.
• A single tank station may be rendered redundant in three of six existing locations, based on expert assessment.

Case Study: Stellingen Potential Space

Stellingen, located in the Eimsbüttel district, exemplifies a heterogeneous urban area where obsolete functions cluster along the Kieler Straße, the northern industrial zone “Kamerbalken,” the local cemetery and church, and peripheral low‑rise commercial estates. The research outlines two contrasting transformation scenarios: (1) a “fast” model preserving the street as a logistics corridor with mixed‑use high‑rise buildings, and (2) a “tamed” model converting the street into a pedestrian‑friendly, climate‑responsive boulevard with dense residential and public‑space interventions.

Planning Instruments and Legal Framework

The report recommends leveraging existing German planning law, especially the BauGB (building code), to implement change. Instruments include accelerated B‑plan procedures (§ 13a BauGB), voluntary and compulsory land consolidation (§ 8‑10a BauGB), and the use of special provisions such as § 176a BauGB for inner‑city development. For more radical interventions, the study suggests applying the urban renewal and transformation provisions (§ 136‑164b BauGB) and amending the “building obligation” (§ 176 BauGB) to incorporate climate‑adaptation goals.

Stakeholder Engagement and Governance

The project identified eleven core communal instruments to foster participation, transparency, and informal planning, ranging from long‑term public debates and co‑creation workshops to “Letters of Intent” and citizen‑led reallabs. A “Gemeinwohlkompass” (common‑good compass) was developed to align transformation goals with local values, ensuring that future land‑use decisions balance social, ecological, and economic objectives.

Outlook and Recommendations for Sustainable Housing

The authors conclude that urban obsolescence offers a substantial reservoir for sustainable housing in growing metropolises. By repurposing underused commercial and infrastructural sites, cities can create affordable, climate‑resilient dwellings while preserving cultural heritage. The study calls for municipalities to adopt a proactive stance, integrating the identified potential spaces into housing strategies, employing the suggested planning tools, and maintaining continuous stakeholder dialogue to achieve a just and climate‑compatible urban future.