Characteristics Of Urban Expansion Research Articles

Rapid urban expansion and potential disaster risk on the Qinghai-Tibetan Plateau in the 21st century

ContextCities are still expanding in many parts of the world in the 21st century, especially in developing regions, where socioeconomic transition has triggered urbanization. The Qinghai-Tibetan Plateau, characterized by its high elevation, developing economy, and fragile environment, has undergone rapid urbanization in the past twenty years, potentially heightening the region’s risk of geological and hydrometeorological disasters.ObjectivesThis article examines the process of urbanization on the Qinghai-Tibetan Plateau in order to better understand the relationship between urban expansion and population change and to explore whether geological and hydrometeorological disasters threaten urban expansion.MethodsWe created a high-resolution urban built-up boundary dataset from 2000 to 2020 based on remote sensing and GIS. By examining the spatio-temporal pattern of urban expansion and its population dynamics from 2000 to 2020 in 15 cities across the Qinghai-Tibetan Plateau, we quantified the urban expansion characteristics and explored the rising geological and hydrometeorological disaster risks urban areas face.ResultsThe Qinghai-Tibetan Plateau has experienced rapid and uneven urbanization in the past 20 years. The total expansion rate was over 252% – 1.48 and 2.81 times higher than that of China and the world, respectively. Urban expansion exceeded population growth in most cities throughout the whole period. The urban built-up areas and population of the Qinghai-Tibetan Plateau tended to concentrate in the Yellow River-Huangshui River Valley of Qinghai Province and the Yarlung Zangbo River and its two tributaries of Tibet. High-density urban built-up areas and population distribution were exposed to geological and hydrometeorological disasters. The urban boundary dataset produced in this study has better accuracy than the other five existing datasets, for the given area and time range.ConclusionsThis study will not only provide a scientific reference for urban development research and future urban planning on the Qinghai-Tibetan Plateau at the regional scale, but will also contribute to research on the urbanization process of the plateau and mountainous regions on a global scale, raising awareness of geological and hydrometeorological disaster risk prevention in these areas worldwide

Characteristics of urban expansion in megacities and its impact on water-related ecosystem services: A comparative study of Chengdu and Wuhan, China

The megacity expansion that continues to occur in developing countries is an unavoidable trend at this stage, yet there exists a dearth of knowledge regarding the comprehensive impacts of urban expansion on water-related ecosystem services (WESs) within these areas. Taking Chengdu and Wuhan, two megacities in the upper and middle Yangtze River Economic Belt in China as the study area, this study first compare the magnitude, rate, spatial divergence, and the mode of urban expansion; then evaluate its impact on three typical types of WESs, i.e., water yield (WY), water purification (WP), and habitat quality (HQ) using spatial econometric models and bivariate Moran’s I. The research findings show that Chengdu’s suburbs tend to experience edge-based expansion along rivers, while Wuhan’s city center also spreads outward in edge-based from the river junctions of the Yangtze and Han rivers. Urban expansion negatively impacts all three types of WESs, and its effect in Chengdu is greater than in Wuhan. WY in the suburbs of Wuhan is severely impacted by urban expansion, while WP in the suburbs of Chengdu is as well. HQ in Chengdu’s city center suffers the largest negative impact. The study also reveals a spatial spillover effect of urban expansion, with extensive negative externalities on all WESs in the city centers of both cities and positive externalities on WY and WP in the southwestern suburbs of Chengdu. Based on these results, we suggest that megacities in developing countries should focus on protecting HQ in the city center and limiting cross-regional edge-based expansion in suburbs. Attention should be paid to the water-ecological protection of the suburb rivers. City managers should consider ecological zoning geared toward the conservation of WESs to address the adverse impacts of expansion.

Spatio-Temporal Evolution of Urban Expansion along Suburban Railway Lines in Megacities Based on Multi-Source Data: A Case Study of Beijing, China

Suburban railways in megacities exert a pivotal role in propelling urbanization and shaping urban agglomeration. However, previous study endeavors have overlooked the transformations occurring in urban expansion along suburban railways, with a particular dearth of attention on the spatio-temporal evolution of landscape ecology and urban function. Therefore, this study employs the megacity of Beijing as an example. It utilizes remote sensing and point-of-interest (POI) data spanning from 2008 to 2022 to construct an indicator system from two essential dimensions: urban form and function. We explored the spatio-temporal characteristics of alterations in urban expansion within the gradient buffer zone adjacent to the suburban railway network in Beijing. The results showed that: (1) The rates of urban expansion were highest in 2008–2013 and lowest in 2013–2018; moreover, suburban railways had the greatest impact on the built-up area within 2–4 km along the route, and the impact gradually decreased beyond 4 km. (2) The direction of urban expansion shifted northward in the direction of latitude and eastward in the direction of longitude from 2008 to 2022, with the shift in latitude being more distinct. (3) The number of urban functions gradually increased from 2008 to 2018, but the number of medical services suddenly increased and the number of other urban functions decreased from 2018 to 2022; in addition, urban functions other than scenic spots were mainly distributed in the main urban areas, with very few clusters distributed near stations. (4) The landscape shape index became more irregular and fragmented from the center along the route to the edge of the buffer zone from 2008 to 2013, and the degree of fragmentation was highest in the 2–4 km buffer zone. In summary, this paper analyzes the spatio-temporal characteristics of urban expansion along suburban railways through four indexes, namely expansion rate, expansion direction, urban function, and landscape shape, and the results of this study are of great significance to the development and planning of suburban railways in megacities.

The mechanism of revoking counties or county-level cities to municipal districts and its effect on urban expansion in Chinese cities

Revoking counties or county-level cities to municipal districts (chexianshequ) is an important means for local governments to optimize spatial governance and promote regional integration. However, the impact of chexianshequ policy on urban expansion and the corresponding mechanism have not been well documented. In this study, we used the urban expansion rate (UER) to depict urban expansion characteristics and adopted a spatial difference-in-differences and mediation effect model to explore the impact and mechanism of chexianshequ policy on the UER. The results showed that the UER of cities implementing chexianshequ policy was 13.455 km2/year faster than that of those without the policy. Taking the implementation time of chexianshequ policy as the dividing point, the UER was 6.951 km2/year faster. In general, the chexianshequ policy accelerated the UER by 19.3% under the control of other factors affecting urban expansion. Moreover, we find that chexianshequ policy exerts a positive effect on the UER, mainly by increasing the proportion of non-agricultural industries, the rural transfer population, improving infrastructure construction, and expanding investment in fixed assets. However, it is particularly noteworthy that chexianshequ policy negatively impacts the UER by increasing the degree of government intervention and expanding the market scale. These findings provide a better understanding of urban expansion that will benefit urban planning and management in effectively controlling unplanned urban expansion.

Spatiotemporal coupling analysis of land urbanization and carbon emissions: A case study of Zhejiang Province, China

AbstractUrban expansion is one of the most important drivers of carbon emissions. It not only causes the invasion of terrestrial carbon sinks but also aggravates carbon emissions through social and economic activities. Because the effect of urban expansion on carbon emissions varies at different stages of urban development, spatiotemporal analysis of the dynamic relationship between urban expansion and carbon emissions is critical for low‐carbon urban planning. By combining nighttime light remote sensing and panel data, this study explored the spatiotemporal coupling characteristics of urban expansion and carbon emissions in a case study of Zhejiang in China. Spatial overlap analysis was used to measure the consistency of the spatial movement trajectories, and the coupling coordination degree model was used to dynamically investigate the interaction between urban land expansion and carbon emission increase. In this way, the dynamic coupling is represented from both a temporal and spatial perspective. The results showed that both the carbon emission and urban expansion growth rates first increased and then decreased, and their spatial coupling became increasingly close. Significantly, the coordinated development level between carbon emissions and urban expansion presented an inverted U‐shaped curve, which is consistent with the Kuznets curve theory. Overall, our research revealed the regularity of carbon emissions associated with land urbanization, which can help policymakers and urban planners to achieve sustainable land management.

15-min Cities: the Potential of a Medium-Sized Polycentric Latin American City.

Urban sustainability and sustainable mobility have become the central focus of sustainable development initiatives. The city of 15 models seeks to ensure that urban development is sustainable. This paper evaluates the current state of mobility and the use of sustainable transport in the specific context of the city of Antofagasta, which, due to its characteristics of urban expansion and its mining activity, has been considered an international reference case. In particular, we study how the current urban structure shapes the city's travel patterns and identify opportunities for public policy actions to focus their investment and urban intervention efforts on the essential aspects that make it possible to achieve 15- or 20-min territories. The results reveal the need for urban development initiatives to focus on improving the supply of goods and services in areas with low installed capacity, promoting the culture of micro-neighbourhoods, and encouraging cycling. In particular, only 10% of trips, for all purposes and all modes of transport, are completed in less than 15min. And about 58% of trips, for all purposes and all modes, are completed in less than 30min. In the marginal effects of the multinomial logit model, a one-unit increase in travel time increases the probability of choosing to travel by public transport by 63% and decreases the probability of walking by 41%.

Urban expansion induced loss of natural vegetation cover and ecosystem service values: A scenario-based study in the siliguri municipal corporation (Gateway of North-East India)

Several cities in the world have been subjected to urban sprawl. For instance, in India, this process is responsible for environmental degradation. The case of Siliguri Municipal Corporation (SMC) is a good example. Therefore, a proper investigation of the urban expansion characteristics of SMC is required to provide a basis for sustainable urban environmental management. This study analysed the changes in land use and land cover (LULC), future scenarios prediction, and ecosystem services values (ESVs) estimation loss. LULC analysis showed that the built-up area increased from 17.26 sq. km to 36.98 sq. km between 2001 and 2015. As a result, the ESVs from natural vegetation decreased by 9.18 million US$/hectare/year during the same period. The urban growth prediction model was generated based using the Multi-Layer Perceptron Neural Network and Markov Chain. Four scenarios were designed to predict future LULC. The model has predicted a maximum urban expansion (66.46 sq. km) in the business-as-usual scenario. The lowest urban expansion (58.81 sq. km) was identified in the planning scenario. The lowest vegetation degradation was observed in the planning scenario. This study highlights the need for an urgent sustainable urban management plan.

Analysis of Spatiotemporal Interaction Characteristics and Decoupling Effects of Urban Expansion in the Central Plains Urban Agglomeration

In recent years, the rapid improvement in the urbanization level of the Central Plains urban agglomeration is bound to bring about significant changes in urban land expansion and economic development. However, at present, there is little attention paid to the research on the spatiotemporal interaction characteristics of urban expansion and the interaction between urban expansion and economic development in this region, and existing research lacks a geographical analysis perspective. This study uses spatial autocorrelation, hot spot analysis, LISA time path, and standard deviation ellipse models to analyze the spatiotemporal interaction characteristics of urban expansion in the Central Plains urban agglomeration from 1990 to 2020, and it uses bilateral spatial autocorrelation and decoupling models to analyze the spatial correlation and decoupling effects of urban expansion and economic development. The results show that (1) the urban built-up area of the Central Plains urban agglomeration as a whole is growing in a “J” shape, and the expansion rate has increased rapidly in the past 10 years. (2) The spatial expansion of the city is mainly in the direction of “northwest–southeast”; the directionality has been gradually strengthened in the past 10 years, mainly in the direction of several prefecture-level cities under the jurisdiction of Anhui Province, and the spatial center of gravity of the city has shifted significantly to the south. (3) The spatial agglomeration characteristics of urban expansion in the Central Plains urban agglomeration are not obvious; local hot spots are concentrated in Jiaozuo and its surrounding areas, and urban expansion has local spatial structural instability. (4) During the 2005–2020 period, the risk of uncoordinated urban expansion and economic growth in the Central Plains urban agglomeration increased. This study is of great significance for the rational control of regional development, providing empirical reference for the formulation of the development planning of the Central Plains urban agglomeration, as well as providing a reference for research ideas and methods related to urbanization.

Spatiotemporal Analysis of Urban Expansion in the Mountainous Hindu Kush Himalayas Region

As a major human activity, urbanization exerts a strong impact on the fragile ecosystem in the Hindu Kush Himalayas (HKH) region. To maintain sustainable development, reliable data on urban land change are required to assess the impact of urbanization. Here, the reliability evaluation of four global fine-resolution impervious surface area (ISA) products: global annual impervious area (GAIA), global annual urban dynamics (GAUD), global impervious surface area (GISA), and global urban expansion (GUE) was carried out. The characteristics of urban expansion for five representative cities including Kabul, Lhasa, Lijiang, Thimphu, and Xining were remarkably different. Based on the results of incremental analysis and the spatial difference of the ISA, it was found that the GAIA dataset at a 30-m spatial resolution could provide better ISA information than the others in characterizing urban expansion in the mountainous region. Subsequently, the changes in the urban area were analyzed using the GAIA dataset from 1993 to 2018. In general, human settlements had grown, with the transformation of small villages into larger towns and some towns into major cities. Urban expansion would continuously intensify the contradictions between human activity and sustainability and exert a more significant impact on the fragile ecosystem in the HKH region. More attention should be paid to the impact of urbanization on the fragile mountainous ecosystem.

Spatiotemporal Evolution of West Africa’s Urban Landscape Characteristics Applying Harmonized DMSP-OLS and NPP-VIIRS Nighttime Light (NTL) Data

Investigating urban expansion patterns aids in the management of urbanization and in ameliorating the socioeconomic and environmental issues associated with economic transformation and sustainable development. Applying Harmonized Defense Meteorological Satellite Program-Operational Line-scan System (DMSP-OLS) and the Suomi National Polar-Orbiting Partnership-Visible Infrared Imagery Radiometer Suite (NPP-VIIRS) Nighttime Light (NTL) data, this paper investigated the characteristics of urban landscape in West Africa. Using the harmonized NTL data, spatial comparison and empirical threshold methods were employed to detect urban changes from 1993 to 2018. We examined the rate of urban change and calculated the direction of the urban expansion of West Africa using the center-of-gravity method for urban areas. In addition, we used the landscape expansion index method to assess the processes and stages of urban growth in West Africa. The accuracy of urban area extraction based on NTL data were R 2 = 0.8314 in 2000, R 2 = 0.8809 in 2006, R 2 = 0.9051 in 2012 for the DMSP-OLS and the simulated NPP-VIIRS was R 2 = 0.8426 in 2018, by using Google Earth images as validation. The results indicated that there was a high rate and acceleration of urban landscapes in West Africa, with rates of 0.016 0, 0.017 3, 0.018 9, and 0.068 6, and accelerations of 0.31, 0.42, 0.54, and 0.90 for the periods of 1998-2003, 2003-2008, 2008-2013, and 2013-2018, respectively. The expansion direction of urban agglomeration in West Africa during 1993-2018 was mainly from the coast to inland. However, cities located in the Sahel Region of Africa and in the middle zone expanded from north to south. Finally, the results showed that the urban landscape of West Africa was mainly in a scattered and disordered 'diffusion' process, whereas only a few cities located in coastal areas experiencing the process of 'coalescence' according to urban growth phase theory. This study provides urban planners with relevant insights for the urban expansion characteristics of West Africa.

Integrating Gaussian Mixture Dual-Clustering and DBSCAN for Exploring Heterogeneous Characteristics of Urban Spatial Agglomeration Areas

Exploring the heterogeneous characteristics of the urban expansion process is essential for understanding the dynamics of the urban spatial structure. Many studies focused on depicting the spatio-temporal characteristics based on urban expansion patches. However, measuring heterogeneous characteristics of urban expansion from agglomeration areas comprising the expanded urban construction land patches have not been adequately explored. This study presents a novel approach and two improved indices for characterizing the heterogeneity of urban spatial agglomeration areas during urban expansion. Firstly, we proposed a Gaussian mixture model considering multiple constrains and density-based spatial clustering of applications with noise (DBSCAN) integration method to identify and extract the urban agglomeration areas automatically. Secondly, the gradient analysis and the compact index using the inverse “S” function are introduced to explore the spatio-temporal characteristics from a macrocosmic perspective. Finally, the compactness index (NCI) and normalized dispersion index (NDIS) are improved based on agglomeration area data. The microcosmic heterogeneous characteristics are measured by these two improved indices and the positional offset characteristics indices (POCIS). The method was implemented in the urban area of Changsha, Hunan Province, China in 2005, 2010, and 2015. The results show that (1) compared to that in the Changsha City Master Plan (2003–2020), the recognition rate was higher in the agglomeration areas than others. (2) The overall expansion trend in Changsha transitioned toward decentralization, making Changsha a polycentric city. (3) The agglomeration of urban expansion in the east-west direction became compact; that in the north-south direction became looser; most clusters expanded to the west and a new sub-center would appear. The proposed method can effectively characterize their heterogeneity, which can provide valuable references for urban planning and policymaking.

Spatial-temporal Characteristics of Urban Expansion in Shenyang from 2001 to 2014

With the rapid improvement of the urbanization process in Shenyang, the urban construction land expands greatly, which makes the urban morphological characteristics change rapidly. In order to guide the city to develop in a more reasonable, healthy, and orderly direction, this article analyses the evolution of urban morphology in Shenyang. By selecting three different periods of satellite remote sensing images in 2001, 2006 and 2014. With the help of Remote Sensing manual interpretation method, the construction land data of the three years in the city are extracted. According to the fractal theory, the laws of urban development morphology are analysed, and the characteristics of urban morphological evolution are summarized. Results show that: 1) the area of urban built-up areas increased by 3.7 times from 2001 to 2014, with an average annual growth rate of 21%. The expansion direction is southwest and northeast. The main reason lies in the development and construction of the southwest side of the Yuhong District and the Shenbei New District.; 2) By analysing the quantitative indexes such as expansion intensity index, compactness index, boundary dimension index and shape index, it is found that the urban expansion of Shenyang is characterized by stages, and the expansion speed in 2006-2014 is significantly lower than that in 2001-2006. This phenomenon indicates that the internal structure of the city has stabilized and it has begun to focus on intensive development; 3) Shenyang has gradually formed a "one-axis, one-belt" urban spatial pattern, focusing on the coordinated and unified development of multiple centres.

Spatial impact of urban expansion on lake surface water temperature based on the perspective of watershed scale

As an important ecological environmental factor, the lake water surface temperature (LSWT) has an important impact on the ecological diversity of lakes and watersheds. With the acceleration of urbanization in China, the impact of urban expansion on LSWT can not be ignored. In this study, we introduced the spatial influence(G) equation, selected MOD11A2, impervious surface (IS), digital elevation model (DEM) and Landsat series remote sensing images as data sources, and took six lakes with rapid urban expansion in China as the empirical research object to explore the variation characteristics of urban expansion and LSWT in six lake watersheds and the spatial influence of urban expansion on LSWT. Finally, the following conclusions can be drawn: The results show that 1) The IS in the six watersheds all experienced significant expansion, with an increase of 1.80–3.91 times. 2) From the annual average LSWT from 2001 to 2018, only Poyang Lake’s LSWT-night shows a cooling trend, while other lakes, whether LSWT-day or LSWT-night, show a warming trend. 3) G is used to comprehensively consider the area change of IS in the watershed, the influence of distance and the change of lake area, which can quantify the impact of IS on LSWT, so as to further explain and describe the spatial influence process and characteristics of IS expansion on LSWT.

Characterizing the Patterns and Trends of Urban Growth in Saudi Arabia’s 13 Capital Cities Using a Landsat Time Series

Development and a growing population in Saudi Arabia have led to a substantial increase in the size of its urban areas. This sustained development has increased policymakers’ need for reliable data and analysis regarding the patterns and trends of urban expansion throughout the country. Although previous studies on urban growth in Saudi cities exist, there has been no comprehensive research that focused on all 13 regional capitals within the country. Our study addressed this gap by producing a new annual long-term dataset of 30 m spatial resolution that covered 35 years (1985–2019) and maintained a high overall accuracy of annual classifications across the study period, ranging between 93 and 98%. Utilizing the continuous change detection and classification (CCDC) algorithm and all available Landsat data, we classified Landsat pixels into urban and non-urban classes with an annual frequency and quantified urban land cover change over these 35 years. We implemented a stratified random sampling design to assess the accuracy of the annual classifications and the multi-temporal urban change. The results revealed that Saudi capitals experienced massive urban growth, from 1305.28 ± 348.71 km2 in 1985 to 2704.94 ± 554.04 km2 in 2019 (±values represent the 95% confidence intervals). In addition to the high accuracy of the annual classifications, the overall accuracy of the multi-temporal urban change map was also high and reached 91%. The urban expansion patterns varied from city to city and from year to year. Most capital cities showed clear growth patterns of edge development, that is, a continuous expansion of built-up lands radiating from existing urban areas. This study provides distinct insights into the urban expansion characteristics of each city in Saudi Arabia and a synoptic view of the country as a whole over the past four decades. Our results provided a dataset that can be used as the foundation for future socioeconomic and environmental studies.

Exploration of urbanization characteristics and their effect on the urban thermal environment in Chengdu, China

As rapid urbanization has drastically and widely altered the Earth's surface, urbanization has become an important contributor to changes in land surface temperature (LST) and the urban thermal environment, which has increasingly become a focus of urban ecologists and environmentalists. The present study used one of the fastest-growing cities in Southwest China, Chengdu city, as an example to explore the urbanization pattern and its effects on surface urban heat islands (SUHIs). To analyze the temporal and spatial characteristics of urban expansion, land use or land cover (LULC) images were classified using a support vector machine (SVM) classifier from Landsat images in 2004–2018, with an overall accuracy of 0.94 and kappa coefficient of 0.90. According to the spatiotemporal LULC changes, Chengdu city expanded at a rapid pace from 80.43 km2/a to 210.50 km2/a in 2004–2018, with an increasing reliance on vegetation area conversion. Spatially imbalanced expansion also occurred. The gravity center moved toward the southeast overall, and peripheral circle districts were the main force of Chengdu's urban expansion compared to the slow-expanding core districts. An allometric model was used to analyze the urbanization pattern, and the results indicated that expansion in Chengdu city was far in excess of its corresponding population growth. The SUHI effect in Chengdu mostly deteriorated over time, and SUHI deterioration closely correlated with the urban expansion area rate and expansion intensity. Therefore, excess urbanization at the expense of vegetation decrease damages the urban ecological environment and accelerates SUHI effects, which threaten habitat health and living comfort.

Characterizing urban growth in Vientiane from 2000 to 2019 using time-series optical and SAR-based estimates of urban land

While annual urban growth rates are declining in many highly urbanized regions of the world, Southeast Asia (SEA) is experiencing an accelerated urbanization process in small and medium-sized cities (SMCs), to which little attention has been paid. High-precision urban land information is a prerequisite for analyzing urban expansion characteristics for SMCs. However, accurately extracting urban land information for SMCs in SEA has remained challenging, considering the lower urban land density, higher vegetation cover, and complex landscape mosaic. This study systematically analyzed the capacities of a set of statistical indicators of time-series optical and synthetic aperture radar (SAR) images in impervious surface extraction. Then, an automatic urban land mapping method was developed by integrating time-series optical and SAR statistical indicators to map urban land area at a finer spatial resolution. The method was applied to Vientiane, Laos, as a case to explore the characteristics of the rapid urbanization process over 2000–2019 and problems related to sustainable urban development. Our results show the statistical indicators of SWIR1, SWIR2, VV, and VH can distinguish urban land from bare soil and cropland, and statistical indicators of NDVI can separate urban land from seasonal vegetated land. The overall accuracies of our products on Vientiane exceeded 95%, and the kappa coefficient was close to 0.90. The study found that the city was experiencing accelerated urban growth, and the urban land area increased from 25.93 km2 in 2000 to 37.23 km2 in 2010 and 62.12 km2 in 2019. Spatially, the urbanization patterns of Vientiane showed a certain degree of sprawl, especially in the suburbs. Rapid urban sprawl poses a significant threat to the urban environment and sustainable development.

Optimization of differentiated regional land development patterns based on urban expansion simulation—A case in China

AbstractThe advancing global urbanization puts great pressure on the society and ecosystem, especially in developing countries. Reasonable land‐use policies adapted to local conditions are the key issues to prevent disordered urban expansion. Multi‐scenario simulation provides a new perspective for differentiated policy formulation based on regional heterogeneity. Regarding the Shaanxi Province, a rapid urbanized area with high spatial heterogeneity in western China, as the study case, we tracked its past land‐use changes and predicted the characteristics of urban expansion using the Future Urban‐Regional Environment Simulation model. We found that (1) during the past 35 years, built‐up land evidently increased accompanied by the loss of cropland, grassland, and unused land. (2) The urban expansion mainly will occur in the areas with flat terrain under three scenarios. (3) The urban expansion will transit into the “requiring land from mountains” pattern in the future, which means that it will gradually spread to areas with higher slopes. (4) Differentiated and optimal development patterns are proposed for different subregions by accounting the loss of ecosystem service in the procedure of urban expansion. This research can help local governments formulate differentiated future macro control of territorial spatial planning to optimize subregional land development.

The Spatiotemporal Characteristics and Rationality of Emerging Megacity Urban Expansion: A Case Study of Zhengzhou in Central China

Studies on urban expansion in megacities are essential for managing urban sprawl to promote high-quality development. In this study, we have selected the emerging megacity of Zhengzhou as the research area, used the spatial analysis method to quantify the spatiotemporal characteristics of urban expansion from 1990 to 2020, and evaluated the rationality of urban expansion on the basis of the elasticity index and a comparison with other megacities. Results demonstrated that 1) Zhengzhou experienced great urban expansion from 1990 to 2020 and showed a trend of “steady–fast–slow,” with steady expansion from 1990 to 2000, fast expansion from 2000 to 2010, and slow expansion after 2010; 2) Zhengzhou’s urban expansion has obvious imbalance and spatial disorder, mainly concentrated in the urban central area, and is characterized by sprawl or a leap in space; 3) the occupation of cultivated land by urban expansion in Zhengzhou has gradually decreased, but the occupation of ecological land such as water areas has increased significantly, which may lead to a series of negative ecological effects; 4) Zhengzhou’s urban expansion was inefficient, while the utilization intensity and economic benefits of Zhengzhou’s urban construction land have improved, but relatively lower than those of other megacities in China. The findings have important reference that is significant for promoting the sustainable urban expansion of megacities and achieving sustainable regional development.

Spatio-temporal evolution of urban built-up areas and analysis of driving factors —A comparison of typical cities in north and south China

Urban expansion is an important manifestation of urbanisation. Based on the impervious surface aggregation density (ISAD) method, this study extracts the urban built-up areas (UBA) range of 12 major cities in the north and south of China from 1995 to 2015. Comprehensive use of the urban centre of gravity, fractal dimension, compactness, urban spatial morphological expansion mode, urban expansion speed, and other indicators was applied to explore the spatio-temporal evolution characteristics of urban expansion. The statistical method GeoDectector (GD) was used to analyse the impact of economic, transportation, natural environment, and social factors on urban expansion. Results show that the 12 cities were shown to have different expansion characteristics and spatio-temporal evolution characteristics. Most northern cities had single-core expansion, while most southern cities had multi-core expansion. Most of the spatial forms of cities tended to be discretized, and the urban expansion process of southern cities was obviously more rapid than that of northern cities. GeoDectector revealed that urban expansion in both the north and south was mainly related to population and economy. Social factors explain the expansion of southern cities, and while the intensity was stronger than that of the northern cities, the natural factors were opposite, and the traffic factors were not significantly different. This analysis confirms the differences in economic development between the north and south of China and provides a scientific reference for the formulation of national-scale urban development policies. In the context of global urbanisation, the results from this study will provide a Chinese sample for understanding the temporal and spatial characteristics of urban expansion, which can serve as a good reference value for other countries and regions worldwide, especially for urbanisation research in developing countries.

基于夜间灯光数据的甘青宁城市扩展及其建成区植被变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 基于夜间灯光数据的甘青宁城市扩展及其建成区植被变化特征 DOI: 10.5846/stxb202005141227 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 甘肃农业大学大学生创新创业计划项目（202102045）；国家自然科学基金青年项目（41907406）；甘肃农业大学科技创新基金（GAU-KYQD-2018-23） Characteristics of urban expansion and vegetation change in built-up areas of Gan-Qing-Ning based on nighttime light data Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:开展针对黄河上游甘青宁地区城市建成区空间发展模式及其植被变化特征的研究，可为构建科学合理的城市发展体系、维护区域生态安全屏障提供重要的参考依据。以DMSP/OLS和统计数据为基础，运用统计数据比较法提取了甘青宁地区21座地级市（州）的城市建成区边界，并从城市空间扩展特征、扩展速度、动态度、紧凑度和重心迁移5个方面对城市扩展特征进行分析；在此基础上，引入SPOT/VEGETATION NDVI数据，以年均NDVI作为表征城市建成区植被状况的指标，从NDVI总和、均值、比值及其变化量、年际变化率及其变化百分率和稳定性5个方面对研究区2002-2013年城市建成区的植被变化进行研究。结果表明：1）采用统计数据比较法提取获得的研究区城市建成区精度较高，误差率在6.7%以内；2）城市用地围绕河西走廊及黄河上游地区形成不连续的"几"字型空间形态，并具有点状、线状和面状3种不同的分布模式；3）城市扩展年均速及动态度大体呈上升趋势，且2010-2013年的城市扩展速度（4.53 km2/a）是2006-2010年的2倍；4）除酒泉、海西、白银、天水、石嘴山和兰州外，其他城市建成区紧凑度指数均较高；5）城市重心在第一（2002-2006）和第二阶段（2006-2010）均向北发生迁移，在第三阶段（2010-2013）则向南发生迁移；6）城市建成区NDVI总和随建成区面积的增加呈上升趋势；7）城市建成区植被整体呈向好趋势，从NDVI均值看，2002-2006年植被状况变差，而2006-2013年又有所改善，且NDVI均值分布具有明显的空间差异，中西部地区普遍小于东部；从NDVI年际变化率和变化百分率来看，各城市建成区均大于外围背景区；8）城市建成区植被状况普遍较背景区差，且2002-2013年近4/7的城市建成区NDVI比值及其变化量均呈下降趋势；9）城市建成区植被稳定性普遍较差，半数以上城市的变异系数在12年间均有不同程度的增加。 Abstract:Carrying out research on the spatial development pattern and vegetation change characteristics of urban built-up areas in the Gan-Qing-Ning region on the upper reaches of the Yellow River can provide an important reference for building a scientific and reasonable urban development system and maintaining regional ecological security barriers. Based on DMSP/OLS and statistical data, this paper extracted the urban built-up area boundaries of 21 prefecture-level cities (prefectures) in Gan-Qing-Ning region by using statistical data comparison method, and analyzed the urban expansion characteristics from five aspects:urban spatial expansion characteristics, expansion speed, dynamic degree, compactness and center of gravity transfer. On this basis, the SPOT/VEGETATION NDVI (Normalized Difference Vegetation Index) data was introduced, and the annual average NDVI was used as an indicator to represent the vegetation status in urban built-up areas. The vegetation change of urban built-up areas in the study area from 2002 to 2013 was studied from five aspects:sum, mean, ratio and its change amount, interannual change rate, percentage and stability of NDVI. The results showed that:1) As one of the effective methods to extract urban built-up area, the statistical data comparison method had high accuracy in our study area, and the error rate was within 6.7%. 2) The urban land formed a discontinuous spatial pattern of "几" around the Hexi Corridor and the upper reaches of the Yellow River, and had three different distribution patterns:point, line and plane. 3) The annual average rate and dynamic degree of urban expansion showed an upward trend, and the rate of urban expansion during 2010-2013 (4.53 km2/a) was twice as high as that during 2006-2010. 4) Except for Jiuquan, Haixi, Baiyin, Tianshui, Shizuishan and Lanzhou, the compactness index of other urban build-up areas was relatively high. 5) In the first stage (2002-2006) and the second stage (2006-2010), the center of gravity shifted northward, and in the third stage (2010-2013), the center of gravity shifted southward. 6) The total NDVI of urban built-up area increased with the increase of built-up area. 7) The vegetation in urban built-up areas showed a positive trend on the whole. From the perspective of the mean NDVI, the vegetation condition got worse from 2002 to 2006, and improved from 2006 to 2013. Moreover, the mean NDVI distribution showed obvious spatial differences, and the central and western regions were generally smaller than the eastern ones. From the perspective of the interannual variation rate and percentage of NDVI, the built-up area of each city was larger than the peripheral background area. 8) The vegetation status in urban built-up areas was generally worse than that in background areas, and the NDVI ratio and its variation in nearly 4/7 urban built-up areas showed a downward trend from 2002 to 2013. 9) Vegetation stability in urban built-up areas was poor, and the variation coefficients of more than half of the cities increased to varying degrees in the past 12 years. 参考文献 相似文献 引证文献