Multi-criteria evaluation of superblock sites in Zurich for greening urban neighborhoods
Lischer, P., 2021: Multi-criteria evaluation of superblock sites in Zurich for greening urban neighborhoods.
Lischer, P. 2021: Multi-criteria evaluation of superblock sites in Zurich for greening urban neighborhoods. Master Thesis ETHZ, D-USYS. Supervisors: PD Dr. J. Bolliger (WSL), Dr. Sven Eggimann (EMPA)
Green areas are essential in urban environments and provide a variety of ecosystem services. While urban densi- fication reduces the available urban green areas, mitigation of current environmental challenges such as urban heating would require increased urban green. The implementation of superblocks could present an innovative approach to address the increasing demand for more urban green areas. Originally developed as a neighborhood transformation model to create pedestrian-centric neighborhoods, the implementation of superblocks could also increase the greenness of a city.
This study investigated 127 potential super- and miniblock sites in Zurich (a miniblock is a miniature version of a superblock) for their implementation potential. First, five geospatial datasets of different sources, resolutions, and seasons were compared by characterizing the greenness of the blocks by the NDVI and the woody vegetation height. Second, the super- and miniblock sites were evaluated with a set of eight indicators that address their green composition (Greenness, Green area per inhabitant, Floor-area ratio, Tree coverage, Vegetation height com- plexity) and spatial configuration (Size, Proximity of blocks to public urban green spaces (PUGS), PUGS accessibility for the whole city). For each indicator, the highest and lowest quartile values were categorized with either low or high implementation potential. The categorization allowed inter-block comparisons for the street, block, and city- scale for individual indicators and indicator combinations.
The implementation of superblocks could increase the greenness of neighborhoods in Zurich, and miniblocks com- plement this potential by addressing smaller neighborhoods. The median greenness between the datasets of all super- and miniblocks varied considerably from 18.4 to 65.9 % (block area) and 3.3 to 57.1 % (street area), which underlines the importance of using a dataset that fits the analysis requirements. The Swissimage RS 2013, the vegetation height model, and their composite dataset characterized the green area most accurately. The Senti- nel-2 dataset was found to overestimate the green area, and its resolution of 10 m was too coarse to analyze the greenness of the super-/miniblock street area. This stands in contrast to the Swissimage RS 2019 dataset that underestimated the greenness due to the record date in early spring.
This study could also reveal significant differences between the 127 super- and miniblocks for all evaluated indi- cator metrics. The created indicator maps suggest that most super-/miniblocks with high implementation poten- tial are found towards the city center. However, this does not apply when aiming at increasing the green area per inhabitant for the street area, creating a higher tree coverage, or increasing the PUGS accessibility. A handful of superblocks were identified that have a high implementation potential for the three investigated indicator combi- nations, whereas the potential of others was highly dependent on the combination. The spatially explicit green area characterization of super-/miniblocks with single indicators and indicator combinations can support local de- cision-makers in greening their cities.
Philipp Lischer, plischer(at)gmx.ch