Visualization and spatial analysis of socio-environmental externalities of urban underground space use: Part 2 negative externalities

Abstract

This paper presents the second part of the two-piece work for the visualization and spatial analysis of socio-environmental externalities of UUS uses. Since the positive socio-environmental externalities of urban underground space (UUS) use have been articulated in Part 1, this Part 2 paper will be devoted to evaluate the negative aspects of UUS development, i.e., the potential threats posed by UUS use to urban sustainability, which requires methodologically distinctive datasets and analyzing approaches compared with Part 1. Findings from this paper will enable a thorough picture of UUS’s role in urban development, both quantitatively and geographically. Consistent with Part 1, Part 2 presented in this paper also builds on the service replacement cost method (SRCM) framework, under which the compromised services of underground assets, namely geothermal energy, groundwater, geomaterials, historical heritage, space continuum and underground organisms, are identified as the monetarized negative externalities derived from UUS uses. The visualization process requires multi-sourced spatial data such as UUS planning data, construction approach data and geological data. Valuation results of the case study showed that the annual average of the aggregated socio-environmental costs of planned UUS uses amounted to approximately 3.2% of the external benefits. Among the calculated items, geothermal energy losses were proved to be the major source of negative socio-environmental externalities in terms of both quantity and spatial distribution. This study facilitates a holistic cost benefit analysis that incorporates socio-environmental benefits, socio-environmental costs and construction costs. Results of the case study proved that most of the planned UUS uses could yield positive net benefits, hence contributing to urban sustainability.