Urban infill development potential in Germany: comparing survey and GIS data

Abstract

Limiting land take is an important sustainability target. To this end, infill development is a primary strategy. To implement this strategy, policy-makers need a reliable knowledge base on infill development potential (IDP), such as brownfields, vacant lots and underused lots. This study presents the results of the first comprehensive national survey of IDP in Germany. Almost 12% of German municipalities were contacted by questionnaire. In contrast to previous studies, this study also takes into account smaller towns and small-scale vacant lots, which would otherwise lead to a considerable underestimation. Additionally, a feasibility study shows how IDPs can be identified using a geospatial approach. Here, a procedure is presented that allows the identification of IDPs and the differentiation between vacant and underused lots by analysing urban morphology using nationwide and commonly available geospatial base data. The results provide a good basis for an initial inventory. However, to obtain more accurate results, additional specific data would be required, the accessibility of which is currently limited. With the development of an improved spatial data infrastructure combined with Open Data initiatives, geographical information system (GIS)-based procedures for the automated detection and monitoring of IDPs could become more important in future. POLICY RELEVANCE If the objectives of land policy, especially the avoidance of urban sprawl, are to be chieved, then the more efficient use of already developed land is essential. At the strategic level of policy development, knowledge of land suitable for infill development is as necessary as knowledge of the land take. Currently, regular standardised questionnaire surveying is the effective method for analysing infill development potential (IDP) and its development on a large scale. Geospatial approaches can help to identify potentials, especially on vacant and underused lots. Thus, they have a considerable potential to serve as heuristic tools for local practitioners seeking to begin reflecting on infill development options. Policy-makers and planners should recognise this potential and develop it further in cooperation with the scientific community. However, decision-makers are not spared from weighing the appropriate density in the respective context—and this has not become easier under the impact of the current COVID-19 pandemic.