A residential quarter is taking shape on the southern edge of Ellwangen that is designed to hold rainwater in a largely closed cycle for up to five years.
About 2,000 people are to live on the site of the former Reinhardt barracks in the Baden-Württemberg town. Ellwangen is applying the sponge-city principle to the entire quarter. Such a district absorbs rainfall, stores it and releases it slowly through evaporation, seepage or reuse.
"An innovative sponge-city concept was developed for Ellwangen Süd, so effective that the result is the first sponge city with no rainwater run-off," Michael Bader of the town's strategic urban development unit told the newspaper Schwäbische Zeitung. As far as is known, he said, no equally far-reaching scheme exists in the state, in Germany or in Europe.
The route the water takes is deliberately visible in the design. Rainfall first collects on green roofs, on paved surfaces and on green space. Shallow channels and sunken beds line the streets and water the trees planted in them. Roof water runs into private cisterns and is used for irrigation or to flush toilets.
That also lowers the flood risk. The planners consider a once-in-a-century flood all but ruled out for the site. Should the storage capacity fall short in extreme rain, water drains into the river Jagst at ten litres per second. Bader offers the flash flood at Braunsbach on 29 May 2016 as a comparison. There, some 150 cubic metres of water per second tore through the Orlacher Bach stream.
Drought summers, water shortages and the resulting limits on water abstraction were taken into account as well. "This strong sponge effect was achieved without any additional land," Bader said.
The project is already organised. The town council set up a municipal development company and awarded project management to Kommunalentwicklung GmbH (KE), a subsidiary of LBBW Immobilien, the newspaper Schwäbische Post reports. KE has moved into offices at Reinhardtstrasse 15. It previously developed the Französisches Viertel in Tübingen and the Hubberg district in Würzburg, both also on former military land.
The land itself is being released step by step. The town agreed with the state that the reception centre for refugees on the site would close at the end of 2025. Mayor Michael Dambacher told Schwäbische Post that developing a building area of this size exceeds what the town administration can handle alongside the expansion of the commercial estate and the 2026 state garden show.
Whether the concept also works financially will be decided when the plots are sold. KE's specialists expect good prospects, because the housing market has dried up. Potential builders approach him constantly, Dambacher said, "including companies from the region that need housing for their staff".