Climate change poses enormous challenges for cities. Extra green spaces on rooftops can provide some relief. A technology developed at EOC helps detect green rooftops and those that can be potentially vegetated. Green rooftop mapping has now been nominated for a “Blue Compass” award by the Federal Environment Agency as a contribution to climate protection and adaptation to climate change.
Of the 111 applications received, the EOC project has turned out to be one of 15 finalists. Three winners will be selected by end of May 2018. The jury is comprised of the Federal Environment Agency along with the Federal Ministry of the Environment, the newspaper DIE ZEIT, Harz University of Applied Sciences, the Verband kommunaler Unternehmen (an association of companies concerned with socially responsible economic activities), the Independent Institute for Environmental Issues, and the Deutsche Umweltstiftung (a foundation supporting environmental initiatives). In addition, one of the nominated projects can be selected to receive the Public Choice Award: until 9 May anyone interested can participate in the internet election via the “Tatenbank” on the Federal Environment Agency website.
Because of their concentration of population, infrastructure and value, large cities are especially susceptible to the effects of extreme weather events (heat waves, storms, floods), which could increase in intensity in future. Moreover, urban conglomerations and the steady growth of built-up areas themselves directly influence the climate.
In order to reduce negative effects and create buffer capacity for predicted climate change, public decision makers need to come up with a dual strategy of measures to protect the climate as well as adapt to the impact of climate change. Conserving and expanding green areas plays an important role. However, there is little space available in densely built-up areas to lay out new parks and greenbelts. So, where can more green areas be created?
Identification of suitable roofs
One possibility is rooftops. But first of all, how many vegetated roofs already exist in German towns and cities? How are they distributed and where can additional roof surfaces be planted with vegetation? It is essential to have answers to such questions, but most cities and communities lack the corresponding data or numbers.
In order to close this knowledge gap, the Deutsche Dachgärtner Verband (an association of German rooftop gardeners) and the German Aerospace Center (DLR) in Oberpfaffenhofen have developed a tool to identify vegetated areas already present on rooftops and assess areas that potentially could be used for that purpose on existing buildings. To accomplish this, high-resolution, false-colour infrared images—in other words aerial and satellite images in which vegetation appears bright red—are combined with survey data on the building inventory (building outlines, 3D city models). This groundwork provides a basis for quickly and efficiently evaluating entire cities with the help of digital image analysis methodologies.
What began in 2013 as a research project financed by the German Federal Environmental Foundation (DBU) could in the meantime be successfully implemented in the cities of Karlsruhe, Stuttgart, Nürtingen, Munich, Nuremberg and Frankfurt. In addition, a cooperating partner from Münster, EFTAS Fernerkundung Technologietransfer GmbH, has a licencing agreement to offer together with the rooftop gardeners association green rooftop mapping and potentials-assessment services based on the developed methodology.
The results of the green-roof inventory show that the analysed cities already have a large number of green rooftops. At the same there is a large potential for vegetation on additional rooftops. Visualizations of existing and potential green rooftops make it easier for municipal decision-makers to efficiently use their available resources to stimulate more planting of green rooftops. The data collected also contribute to improving city climate models, planning drainage, and biodiversity concepts.
Already in 2015 the green roof project was honoured at the 4th International Green Roof Congress in Istanbul with a “Green Roof Leadership Award” in the category “Green Roof Pioneers”. The project could also be presented in 2016 during the “Week of the Environment” at Bellevue Palace Park in Berlin, in front of the impressive backdrop of the official residence of Germany’s president.
For the future, the DLR scientists participating in the project hope that their approach will help to sequester greenhouse gases and air pollutants on green rooftops as well as reduce the urban heat island effect and the burden on the sewer system through the storage and evaporation of rainwater. In addition, suitably designed green rooftops can be places for people to relax, and they can enhance living conditions. They also improve the energy balance of buildings and support aspects of the protection of endangered species and biodiversity. The purposeful expansion of green infrastructure on the roofs of public buildings is therefore regarded by many cities as an important component of modern city planning. In the federal government’s white paper on urban greening there is even a separate chapter on the greening of buildings.