Objective Green open space serves as a main carrier for daily leisure and entertainment of urban residents, and is closely related to the construction of urban livable environment and the improvement of residents’ quality of life. However, in mountain cities with unique urban texture and spatial pattern due to the restriction of such factors as landform and construction conditions, the walking system is closely integrated with the undulating terrain, posing many challenges to the planning and construction of green open space. For mountain cities, the walking accessibility is relatively limited, the actual walking accessibility of green open space is inferior to the theoretical accessibility, and the traditional methods for accessibility measurement may not take effect, resulting in the lack of green open space in the real life of residents. In view of this, it is necessary to improve the accuracy of quantitative evaluation of accessibility in mountain cities. In fact, accurately and objectively measuring the walking accessibility of urban green open space and revealing the difference between actual accessibility and theoretical accessibility are the key to optimizing and improving the service capability of green open space in mountainous areas.
Methods Taking Yuzhong District in Chongqing as an example, this research, based on ArcGIS platform and Amap application programming interface (API), develops a new quantitative accessibility evaluation method termed “path tracking method” with reference to the path buffer method proposed by previous scholars. Then the research compares the evaluation results of the path tracking method and the network analysis method to differentially identify the areas with accessibility attenuation, which helps more clearly and accurately reflect the spatial problems under the influence of mountain conditions. After that, the research discusses the gap between the theoretical and practical use of green open space. Specifically, the path tracking method uses python-based self-programmed code to obtain the walking path trajectory data from the green open space entrance to the building entrance in batches, unify the geographical coordinate system and carry out visual analysis, set the buffer range at both sides and end point of the path as 10 meters and 30 meters respectively, and obtain the accessible range of 5, 10 and 15 minutes.
Results The walkability evaluation results of green open space in Yuzhong District show that: 1) The evaluation results of the two methods reflect similar spatial distribution, that is, there exist large-sized service blind areas in the southwest and the periphery of Yuzhong District; 2) comparing the evaluation results of the two methods, it is found that the walkability of green space in Yuzhong District decreases by 43.19%, and the accessibility attenuation areas within the threshold of 5 minutes, 10 minutes and 15 minutes account for 32.12%, 46.49% and 46.30%, respectively; 3) the longer the actual walking distance, the greater the attenuation of accessibility; the attenuation area within the 5 min threshold is mostly located at the entrance of green open space and complex three-dimensional traffic area, and the attenuation area within the 10/15 min threshold is mostly distributed along the terrain or road trend; the insufficient pedestrian permeability of blocks may also lead to the attenuation of accessibility; 4) the accessibility attenuation varies among different research objects, of which 16 objects have an attenuation degree greater than 60%, and Kowloon Bund Park has the largest attenuation degree with an attenuation ratio of 87.71%; 5) in order to further analyze the correlation between mountain spatial characteristics and accessibility attenuation, the green open spaces are divided into five types according to their geographical locations, among which the hilltop, platform-based and riverside wedge-shaped green open spaces have a higher degree of attenuation; 6) factors affecting the accessibility attenuation of green open space in mountain cities include location factors, environmental factors and ontology factors.
Conclusion Finally, based on the above analysis, the research puts forward optimization suggestions for the planning and construction of green open space in mountain cities from the perspective of walking accessibility. These suggestions include increasing the total amount and service efficiency of green open spaces by siting them on the mountain, connecting different vertical levels of green open space through the slow walking system, and guiding residents to visit green open space through the permeability of the interface thereof. This research provides an objective method for evaluating the walkability of green open space in mountain cities, with the evaluation results being more in line with the actual situation compared with other relevant methods, and points out the shortcomings of existing methods and indicators, which has important practical significance for improving the service efficiency of green open space in mountain cities. Meanwhile, the individual subjective factors of residents and the attractiveness of green open space can be further considered in future research, and the evaluation method and influence mechanism of multi-dimensional accessibility can be further explored, so as to provide scientific basis for the evaluation of mountainous urban space and reference for the future planning and construction of mountainous urban space.
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