| Remarkable urbanization in China represents perhaps the greatest humanresettlement experiment in history and is acknowledged as an event with a profound impact on global human civilization and development.Since economic reform in China and the opening up of the country to the world,land finance promotes land urbanization while the household registration system(Hukou system)represses population urbanization,resulting in population urbanization lagging behind land urbanization.The unsustainable land-centered urbanization has led directly to the phenomenon of residential vacancies in China.In recent years,massive and increasing vacant residences have extremely adverse effects on society,the economy,and the environment.That goes against people-oriented urbanization and hinders the healthy development of urbanization in China.Understanding spatiotemporal dynamics and driving forces of residential vacancy are of vital importance when alleviating residential vacancies.Many studies counted the vacant housing area or evaluated the vacancy possibilities or degrees of various cities in China.Further,some studies suggested some socio-economic factors,housing market factors,and physical environmental factors affecting residential vacancies,as well as the categories of cities with massive vacant residences primarily based on the characteristics of the entire city.Although existing studies have given us new insights into residential vacancy,challenges still remain.(1)Ignoring the regional characteristics and spatial heterogeneity of residential vacancies at the local scales within the city,the spatiotemporal dynamics of vacant residences at granular levels are difficult to describe.(2)Ignoring the facilities and services(FASs)that are closely related to residents and must be considered in residential issues,the relationships between residential vacancies and the residential neighborhood service environmental factors are rarely examined.(3)Ignoring the complexity and diversity within a city as well as obscuring the heterogeneity and fluidity of vacant housing,the variability in and mixture of residential vacancies have not been sufficiently explored at granular levels.Against this background,this study aims to refine sensing residential vacancies using municipal infrastructure and service data(specifically,municipal water consumption data)and address three unique and challenging questions:(1)How can we identify residential vacancies at the household level using municipal water consumption data?(2)How can we quantitatively examine the influence of the driving forces of the residential neighborhood service environment on the residential vacancies?(3)How can we identify the various categories of residential vacancies at the household level municipal water consumption data,and measure the diversity of vacant residences at the building level?In addition to advancing our understanding of the residential vacancies embedded in the urbanization of China,answering these questions sheds light on policy implications for the mitigation of residential vacancies and further helps urban managers and planners ensure the sustainability of people-oriented urbanization.Corresponding to the three questions,there are three specific studies and main findings:(1)Delineating spatiotemporal dynamics of residential vacancy at the household level.This study proposed the residential vacancy identification framework via municipal water consumption data.First,a residential vacancy identification method(RVIM)is proposed using residential water consumption data to recognize the occupied/vacant state of each residence at any time and establish residential state time series.Second,spatiotemporal distribution analysis methods were employed to understand the spatiotemporal characteristics of the residences and vacant residences.The framework was applied in Changshu city,China,and the results revealed a concentric circular spatial structure(i.e.the declining city center,prospering inner city,near suburb,and far suburb)and dual characteristics(i.e.both stagnant recession and prosperous expansion)for residences,as well as a binary structure(i.e.center and periphery)of vacant residences.The results also indicated that new residential forms were shaped by replacement or accretion,such as the declining city center and the rising subcenter.Compared with understanding the degree/area of vacancy of the entire city,the framework can grasp the spatial expansion and internal transformation of the vacant residences within a city.They send a strong signal to decision-makers regarding areas in need of improvement,such as the declining city center,the areas with higher kernel density scores of residential vacancy.Precisely identify the problematic areas is the basis for devising customized mitigation policies.(2)Exploring service environmental driving forces of residential vacancy at the household level.This study proposed the service environmental driving forces of the residential vacancy analysis framework via municipal water consumption data.First,based on defining the multisized neighborhoods,multisized neighborhood service factors(NSFs)representing various characteristics of the FASs within the residential environment were extracted for each residence.Second,the relationships between residential vacancies and NSFs were examined by random forest.The framework was applied in Changshu city,China,and the effective relationship analysis(OOB error of 0.086,overall MSE and Med AE of 0.125 and 0.242,respectively,70% of residential spatial absolute error less than 2 months)revealed business(BUS),industry(IND),and life service(LIF)(or government and public service(GOV))are the three most important FASs.The results also indicated that the diversity of the FASs has the highest impact on residential vacancies.As the degree of enrichment of the FASs approximates 1 or the percentage/diversity of the FASs increase,the residential vacancy length decreases.The contributions of areal percentage and diversity have significant scale(specifically size of the neighborhood)dependence.The framework pays attention to the residential neighborhood service environment and can provide local decision-makers with recommendations for mitigating residential vacancies in the problematic areas by optimizing the arrangement of facilities and services.One of the key measures that can be taken is to enhance the FAS diversity within the small-sized neighborhoods of residences.It is also important is to ensure that residential neighborhoods are not excessively rich or poor in FASs compared to the entire city.Last but not least,it is recommended to allocate specific functional areas(e.g.,a technology park)within large-sized neighborhoods of residences.(3)Revealing variability in and mixtures among residential vacancies at granular levels.This study proposed the variability in and mixtures among residential vacancies analysis framework via municipal water consumption data(specifically,residential state time series).The framework includes three distinct components.First,the Doc2 Vec algorithm is employed to convert the vacant residence corpus derived from the residential state time series into vectorized document representations,and then the K-means++ algorithm is used to categorize the vacant residences on the basis of the obtained vacant residence vectors.Second,the differences in the vacancy patterns among the various categories of vacant residences at the household level are explored.Third,the mixture of vacant residences at the building level is measured using the entropy index;therefore,both the spatial distributions of and temporal evolutions in the mixtures of vacant residences are identified.This framework was applied to the city of Changshu,China,and four categories of vacant residences at the household level were identified: seasonally vacant residences,long-term vacant residences,newly built residences,and occasionally vacant residences.The first category is closely related to tourism and seasonal industries,while the last three exhibit a Matthew effect.In addition to revealing significant and intensifying spatial clustering and three patterns of changes in vacancy mixtures(i.e.,emergence,disappearance,and increases or decreases),the results identify particular types of vacant residences at the building level(e.g.,extremely low-entropy long-term multihousehold buildings).In the absence of any prior knowledge,the framework can suggest that the local decision-makers should concentrate their limited resources on specific types of vacant residences,e.g.long-term vacant residences and seasonally vacant residences in this study.For instance,to mitigate long-term vacant residences,several recommendations for improving the neighborhoods in which such residences are found(e.g.,enhancing the diversity of facilities and services)were made.This is critically important for maximizing government interventions and investments through customized policies. |
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