Permeability of the city – Physical barriers of and in urban green spaces in the city of Halle, Germany

Abstract

Urban green spaces (UGS) provide important ecosystem services in cities as they support human health and wellbeing with fresh and cool air, beauty and space for physical activities. To benefit from the positive effects, citizens need access to UGS. Multi-layered barriers can restrict accessibility to green–blue infrastructure (GBI) and accompanying benefits. This study aims to quantify and visualize physical barriers to public and semi-public UGS in the city of Halle, Germany, focusing on three spatial dimensions regarding UGS. For each dimension, three indicator classes are defined as proxies for varying aspects of accessibility: inside, boundary, and outside. A barrier index was calculated for all public and semi-public UGS of the city that cumulated the ratings of each indicator class. The aggregation of all ratings for all three dimensions creates a final barrier index that illustrates all physical barriers of, to and within UGS. We can show to which degree UGS accessibility might be restricted in Halle. As the results show, inside barriers exhibit the highest barrier index indicating that accessibility is most restricted on this dimension of UGS throughout the city. Comparatively low barrier indices in the inner city indicate the best accessibility to UGS in the five districts. Moreover, semi-public UGS like gardens or cemeteries show higher levels of physical barriers than public ones. Linking the barrier index to current urban planning and examining how the indicators defined in this study are addressed in planning documents concerning the improvement of accessibility can be a useful tool for spatially identifying potential planning measures that can reduce physical UGS barriers.