Evaluation and Optimization of Refuge Green Space in the Central Area of Tianjin for Geological Disasters

Refuge Green Space (RGS) plays roles in both rapid evacuation and short-term resettlement in response to sudden natural hazards, especially geological disasters. As a result, its evaluation and location optimization are crucial for the development of sustainable cities. In this study, the Three-Step Floating Catchment Area Method (3SFCA) and Moran’s I index were used as measurement models. The rapid evacuation and short-term resettlement capacity of RGS were evaluated by calculating accessibility with 5, 10, 15 and 30 min of walking. The purpose of this study was to quantitatively evaluate the supply capacity of RGS in the central area of Tianjin and to provide recommendations for future additions to RGS. The results show that over 80% of the research area exhibited relatively poor service capacity within a 5–10 min walking distance, while less than 20% exhibited relatively good service capacity. Within a 15–30 min walking distance, approximately 60% of the study area was not well served by the RGS, while approximately 40% was well served. In conclusion, the layout of RGS in the central area of Tianjin exhibits unevenness and polarization of phenomena, and the supply of different categories of RGS varies widely. There is an insufficient supply of Emergency Sheltered Green Space and Temporary Sheltered Green Space, and that which is available is difficult to reach within 5–10 min. The coverage capacity of Disaster Prevention Park Space is relatively good, essentially covering the entire study area within a 15–30 min walking distance; however, the service capacity is average. Based on these conclusions, areas in which the RGS supply was weak were identified, and future potential RGS additions were identified in conjunction with the Green Space System Plan.