Multi-level And Multi-dimensional Characterization, Multi-strategy And Multi-scale Spatial Regression Of Urban Sprawl

Background:Urban sprawl is characteristical in the world and it is the product of urban development at certain stage. It represents a degree as a noun and a process as a verb. It encompasses both the the spatial expansion and dispersion of urban areas. The concept of "Sprawl" is coined in American, followed by a mass of research achievements in European cities and cities in the developing countries. In China, sprawl is land-oriented and the magnitude of urban built-up land sprawl is greater than the sprawl of population. In the process of promoting urbanization in the past several decades, we follow an extensive expansion pattern in which attention has been paid on the quantitative growth rather than qualitative improvement. This resulted in great loss of cultivated land, serious deteriation of terrestrial, aquatic and atomospheric environement and has formulated a great threat for a balanced development of eco-environment. In the mean time, the land oriented urban sprawl would lead to unbalanced socio-economic development, which would be detrimental for the urban sustainability. Therefore, in the context of promoting urbanization, the unified urban and rural development, advocating intensive urban land use and sustainable urban development, stimulated by the project of monitoring national geographical environment, the research on urban sprawl from theory to practice, from static to dynamic, from measurement to modeling and from temporal to spatial extension would be of great value.Materials and methods:The study area we choose is Wuhan metropolitan area-the mega-city in central China in the past twenty years. Methodogies implemented include bibliometric, literature review, spatial anlaysis and modeling as well as the integration and extension of remote sensing and geographical information system. Specifically, based on the results produced by the bibliometric techniques, we analyze the current studies on urban sprawl, major problems, conceptions, characteristics and techniques mainly applied quantitatively and qualitatively. Chapter3introduces our research area and includes data description. Chapter4undertakes multi-dimensional characterization of urban sprawl, including composition, configuration, density, gradient, proximity, accessibility and dynamics at multi-levels-parcel, district and metropolitan area. The degree of urban sprawl is assessed from population, socio-economic development, transportation and land use with25indicators in chapter5. Chapter6embodies monitoring and multi-strategy modeling of urban sprawl in different scenarios with the integration of remote sensing, geographic information and spatial statistics. The multi-scale platform is proposed, characteristical, density and proximity variables are selected as factors and spatial modeling at different scales are compared and analyzed in Chapter7. The last chapter summarizes the major contributions, novel ideas and puts forward recommendations.Results and discussions:Based on the integration and application of aformentional methodologies, results and discussions are made accordingly.(1) Urban sprawl is a regional phenonmenon and there are distinctive differences among American cities, European cities and cities in developing countries in terms of urban sprawl. Research on urban sprawl is multi-disciplinary and concerns with land use, eco-environment, human health, modeling and technical applications. The basic paradigm for urban sprawl is "Cause-Characteristic-Impact" and these three dimensions can be analyzed independently or comprehensively.(2) Urban sprawl is the process of spatial expansion and dispersion with the characteristics of complexity, neutrality and space-time features. In China, socio-economic development and related institutions and policies are the major driving force of urban sprawl. Taking different forms of sprawl, there are great differences in the spatial pattern of urban areas. Both negative and positive impacts exist in urban sprawl and the negative impacts are more obvious in land use, eco-environment and living quality.(3) Taking Wuhan as a case study, the multi-level and multi-dimensional measurement has indicated that industrial sites and built-up land for special use have taken a more random and scattered distribution. Parcels and districts around central districts present a higher fragmentation with greater change in land use and more obvious sprawl. These changes are accomplished through the delieantion of development zones and Jianchengqu. Furthermore, we identify parcels and districts with significant change in landscape pattern from1996to2006and advices are proposed in response.(4) Taking Wuhan as a case study, the multi-factor assessment integrated with spatial analysis technique has revealed that population sprawl index increases in a linear pattern, land use sprawl index grows in an exponential pattern and fluctuations exist in socio-economic sprawl index and transportation sprawl index. Furthermore, lower spatial autocorrelation is identified in road density and higher spatial concentration exists in built-up land. The integrated urban sprawl index increases gradually before2004and grows fast after that.(5) We monitor and modeling urban sprawl in Wuhan from1995to2010with the integration of remote sensing, geographical information system, and spatial statistics. The results show that during the past15years, built-up land has expanded greatly, the spatial distribution has been more concentrated, and however, dispersion has appeared in urban clusters. The gravity centroid migration is closely related to the contruction of development zones in Wuhan. Meanwhile, spatial regression techniques prduce better result than the empirical statistical techniques and have shown superioty not only in fitting, but also in exploring the spatio-temporal correlation.(6) We undertake multi-scale spatial regression through grid filtering in Wuhan central districts. The results reveal that built-up land percentage and its factors all present higher spatial autocorrelation. R2in the regression has risen with scale increasing which indicates the spatial heterogeneity at different scales. At each scale, spatial error model produces better result than the mixed regressive-autoregresive model and spatial models are superior to classifical statistical models significantly.Summerization and recommendations:Based on the voluminous literature review, we implement the characterization and modeling of urban sprawl in a multi-level, multi-dimensional, multi-factor, multi-scenario and multi-scale manner. Theoretically, we analyze the concept and charaterics of urban sprawl and elucidate its research situation and trend. Empirically, we take Wuhan as a case study to illustrate the measurement and modeling of urban sprawl quantitatively and qualitatively. Methodologically, spatio-temporal features are taken into account in urban sprawl and comprehensive and innovative experiments are designed accordingly. Technically, remote sensing, geographical information system, spatial statistics are integrated and applied in the whole process. The results provide reference for land use planning and urban planning, in addition, methodogies in our research can be applied to other cases as well. In the future, several recommendations can be made in comparison of urban sprawl in China and cities worldwide, theorectical accumulation of urban sprawl in China, measurement of urban sprawl through a bottom-up approach, spatio-temporal modeling of urban sprawl and the extended integration of remote sensing, geographical information system and spatial analysis techqnies.