The research on the evaluation framework and application of urban three-dimensional (aboveground and underground) regeneration sensitivity——Taking Kunshan Old City in China as an example

Abstract

Urban regeneration (UR) is a strategic approach to urban transformation. Currently, most cities in China are moving into an era of land stock usage, emphasizing the optimal use of existing land resources. Consequently, the strategic optimization of 3D spatial resources, both aboveground and underground, has progressively emerged as a highly effective pathway for UR. However, most prior studies lack a forward-looking arrangement and guidance for the operational method regarding the scope of regeneration and sequencing from a 3D perspective. This has resulted in urban three-dimensional regeneration (UTDR), which has not yet been widely utilized for scaled planning research and practice systems. Hence, we introduced the innovative concept of UTDR sensitivity and proposed a systematic evaluation technique to identify priority areas for effectively revitalizing urban aboveground and underground spaces while realizing phased UTDR based on sensitivity levels in an organized way. Specifically, we dismantled the source of sensitivity, with UR motivation, spatial carrying pressure, and three-dimensional construction potential as the three key sub-systems. Then, we extracted and selected quantitative indicators through the combined use of social network analysis and correlation; we determined the weight allocation of the indicators using the random forest model. We explored the spatial patterns of UTDR-sensitive districts and intervention-related priorities based on importance-performance analysis and coupled coordination models. In addition, our framework helped reveal the degree of influence of driving indicators for different systems on the spatial characteristics of UTDR sensitivity. Using ArcGIS, we visualized the agglomeration-based features and rules for differentiation regarding the results of quantitative spatial analysis based on a case study in Kunshan, China. We identified (1) 76 key units of UTDR-sensitive districts, mainly distributed in the central and southwestern parts of the research area, which faced the severe challenge of growing human-land conflicts; and (2) three planning intervention-related priorities. Thirty units were at the level of high sensitivity, requiring priority-based interventions to alleviate the contradiction between the insufficient supply and the significant demand for urban space through UTDR actions. The classification of spatial units and zoning (based on the evaluation of the sensitivity difference) is important for objectively selecting the possibility and priorities of UTDR. The assessment outcomes are crucial for the refined development of UTDR and for promoting the scientific implementation of regeneration planning.