Fitness Assessment On Urban Carrying System In A Big Data Context

With the rapid growth of urban population and the disordered expansion of urban space,sustainable urban development in China is facing severe challenges,as well as a series of residential and environmental problems such as housing shortage,environmental pollution,and traffic congestion.Under the circumstances,the government has continuously strengthened the basic binding effect of urban carrying capacity(UCC)on urban expansion,spatial development,and structural adjustment in policy-making.However,due to the knowledge gap in the carrying mechanism and assessment methodologies,existing studies frequently simplify high-dimensional spatial issues and micro-experience issues as quantitative issues and macro-statistics issues,which has resulted in a mismatch between UCC assessment and practical management.Driven by the development of information technology,big data has attracted extensive attention from academics and the government.The new data types,analytical thinking,and methodology in big data era provide new opportunities for innovations in UCC researches.In this study,starting with inner action mechanism,the concept of fitness was introduced based on the conceptual model of urban carrying system,focusing on the carrying status of elements under spatial subdivision.Based on multi-sourced data(such as traffic congestion data,path planning data,and street view data)and a series of technologies(such as GIS technology and machine learning technology),the present research has separately conducted the fitness assessment from quantitative perspective at sub-district level and from spatial efficiency perspective at block level.To be specific,the former concentrated on the quantification of supply and demand relationship,while the latter could be further divided into two aspects,that is,spatial structure(accessibility of service facilities)and spatial quality(perception of spatial environment),focusing on the spatial perception of urban population at a micro scale.By the identification of restrictive factors and major governance areas,this research attempts to provide a scientific basis for urban delicacy management.Taking the sub-districts within the Shanghai outer ring road as study area,this study found that:(1)At the sub-district level,the fitness assessment was conducted on the supply and demand scale of carrying elements from four dimensions,that is,housing space,municipal facilities,public service and ecological environment.In terms of housing space,old urban areas showed a clear mismatch between supply and demand;the housing space was relatively crowded and cramped due to the presence of massive old lanes and alleys.In terms of municipal facilities,severe traffic congestion could be observed around the important travel destinations within the inner ring road and Hongqiao Sub-district during peak hours.In terms of public services,urban pension services and community health care,especially the former,were in short supply overall.In terms of ecological environment,the supply-demand contradiction of urban parks was prominent,especially in highly populated old urban areas,which reflected the encroachment of urban parks and other public open spaces by intense land development under land resource restraints.In consideration of the scope,degree of unfitness and weight of indexes,urban pension,urban parks and community health care were the cardinal restrictive elements of the study area.(2)To explore facility accessibility,the spatial efficiency assessment of fitness was conducted from the perspective of spatial structure.In general,the study area had good access to different kinds of public service facilities,especially blocks within the inner ring road.Owing to the land resource restraints,there were differences in the strategies of public service facility planning adopted by different areas.Taking urban parks as an example,the areas within the inner ring road and other highly populated areas were generally distributed with small-sized parks or green spaces,emphasizing facility accessibility and service coverage;in contrast,the areas along and beyond the outer ring road were mainly distributed with large and medium-sized parks or green spaces,focusing on large-scale supply but with insufficient service coverage.(3)To explore urban environmental perception,the spatial efficiency assessment was conducted from the perspective of space environment quality.In terms of safety perception,blocks with low perceptual score are mainly located outside the outer ring road and around the Bund.Blocks with low safety score around the Bund were induced by the presence of old neighbourhoods,narrow streets,and underground tunnels in the central area of Shanghai.Meanwhile,blocks with high depressing score were mainly located within the inner ring road because of the tall and dense buildings.The study area had a high level of vital perception in general.The low vitality blocks are mainly located in the peripheral areas.Traces of human activity,such as pedestrians,vehicles,and buildings,were important criteria for models in measuring vitality perception.The high aesthetic perception scores were scattered in the study area,largely depending on streetscape and greening construction in different areas.According to the analysis of landscape elements,street green visibility is an important factor influencing aesthetic perception.(4)Starting with spatial management efficiency goals,we overlaid facility accessibility and environmental perception with block population,and identified areas in need of further planning efforts.In the near term,blocks under high governance pressure in terms of accessibility mainly included the Yangbei units,the Youyijiayuan units,the Sitang units,and so forth,where educational,cultural,and sports facilities,and green space should be supplied.Within the outer ring road,the public service accessibility in Xingfuxiaozhen,Xinjinqiao,and Baiyelu units also should be improved.In light of urban master planning,the major areas in need of long-term governance in terms of facility accessibility were mainly distributed in old urban areas,especially the areas along the inner ring road in Puxi and those along the Huangpu River in Pudong.The major areas in need of urban spatial environment governance were mainly distributed within the inner ring road,surrounding the Bund;they formed continuous areas in Huangpu,Jing'an and Hongkou.Besides the scattering of inhabitants and the control of development intensity in central areas,the pivotal issues in future spatial environment governance also include the design of streetscape,the increase of green and open spaces,and the renewal of old lanes and alleys while protecting historic and cultural scenes.(5)Different kinds of big data have shown the advantages of fine resolution,low cost and wide coverage in the new data environment,which could make a fine description of urban environment and human activities at the micro scale.It enriches and supplements the research on UCC assessment,and strengthens of the ability to analyse complex urban system.With regard to this paper,the research methods and findings could offer powerful support for the fine-scale UCC zoning,the assessment and management of community life circle planning and the identification of urban regeneration units.