Expansion Of Urban Agglomerations Research Articles

Quantitative spatiotemporal evolution of large urban agglomeration expansion based on 1995–2020 nighttime light and spectral data

The spatial distribution of urban agglomerations is an essential component of urban agglomeration development planning. To obtain information regarding the expansion of urban agglomerations over large spatiotemporal scales and long periods, this research quantitatively assess the spatiotemporal evolution of the large urban agglomerations in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) from 1995 to 2020 based on the multisource nighttime light and various spectral data. The results showed that, from 1995 to 2020, (i) the GBA expanded in a “northwest-southeast” pattern and showed a trend of slow expansion and then rapid expansion; (ii) the longest migration of the centroids of the cities in the GBA occurred in Foshan City (9965.22 m), which migrated at an angle of 37.88°to the west by north; the shortest migration distance of the centroid occurred in Macao (779.65 m), where it migrated at an angle of 33.96°to the south by the east; (iii) the GBA expanded in a “circle radiation” pattern, and the subcentre cities have more significant development potentia; (iv) the distribution of “hot and cold spots” of urban expansion in GBA remained stable; and (v) the aggregated autocorrelation of expansion in the GBA was not statistically significant but underwent continuous “decentralisation”. Compared with previous studies, our work rapidly and accurately extracted the spatiotemporal evolution of GBA urban expansion from 1995 to 2020 at a spatial resolution of 30 m, which can effectively supplemented current socioeconomic statistics data lacking geospatial information, and detailedly discussed the geospatial displacements of the geographic elements for all cities to assess the differentiated information and agglomeration effects in the inner areas of large urban agglomeration. The results can provide valuable datasets, vital technical support and decision-making references for constructing sustainable development strategies in GBA and other large-scale urban agglomerations.

Regional integration policies and urban green innovation: Fresh evidence from urban agglomeration expansion

Climate change is a non-traditional security crisis affecting the global economy and diplomatic progress. In order to curtail carbon emissions and alleviate the perils of climate change at their roots, urban green innovation (UGI) has emerged as a pivotal technological solution. Using the expansion of the Yangtze River Delta urban agglomeration in China as a case study, this paper develops a quasi-experimental model to analyze the effects of regional integration policies on UGI. The main findings are: (1) Regional integration policies significantly enhance UGI and their impact is more pronounced with the expansion of urban agglomerations; (2) Regional integration policies contribute to the advancement of exploitative green innovation while tending to diminish exploratory green innovation; (3) The green innovation effects (GIEs) created by the expansion of regional integration policies are largely influenced by governmental mechanisms on environmental governance as well as residents’ green preferences. Based on these findings, recommendations are put forward to promote UGI from the perspective of policy implementation.

Analysis of Spatiotemporal Changes in the Gravitational Structure of Urban Agglomerations in Northern and Southern Xinjiang Based on a Gravitational Model

The urban agglomeration plays a significant role in enhancing integrated regional development. Nevertheless, the expansion of urban agglomerations has demonstrated a lackluster ability to attract cities. Presently, finding solutions to stabilize the existing urban strength and effectively extend attraction to neighboring cities has become a crucial matter. This study adopts the enhanced comprehensive attraction model, fracture point model, and radiation radius model to examine the level of city attraction, intensity of radiation, and range of radiation in the northern and southern Xinjiang city clusters between 2010 and 2020. Based on the analysis, the following conclusions are drawn: (1) the comprehensive strength and city attraction of cities in the northern Xinjiang region is higher than that of the southern Xinjiang region; (2) the intensity of spatial connection between cities in the northern and southern Xinjiang regions is gradually increasing, and the intensity of spatial connection of cities in the northern Xinjiang region is significantly greater than that in the southern Xinjiang region. The intensity of spatial connection between cities in the northern and southern Xinjiang regions is significantly greater than that in the southern Xinjiang region; (3) the central role of the central cities in the northern and southern Xinjiang regions is weakening, the development of cities in the region is gradually becoming unified and coordinated, and regional integration is gradually being strengthened. This study reveals the similarities and differences in urban development in the north and south of Xinjiang and provides important theoretical reference value for regional urban development.

Rewilding in megacities: from concept to implementation

The expansion of urban agglomerations and the accompanying increase in the severity of environmental problems require special attention to ensure a comfortable urban environment. One of the ways to solve this problem is to create an ecological framework in the megacity, formed by quasi-natural biocenoses, created within the application of the concept of rewilding. This article reviews the main current trends and approaches to the implementation of rewilding; discusses positive and negative environmental effects of the transformation of urban ecosystems within rewilding; presents an analytical review of available techniques and options for rewilding in various megacities around the world.

The Challenges of Building Sustainable Cities in Cameroon: Health Issues Associated with a Rapid Urban Population Increase in Buea Municipality.

Rapid urbanization compounded by urban poverty is one of the main challenges facing many Sub-Saharan African countries. The Buea municipality is the 10th largest city in Cameroon and equally faces such problems brought about by unplanned development in the past four decades. In 2020, the population growth rate in Buea rose to 42% compared to 5.6% in 2005, especially in the peri-urban areas. This resulted in direct and indirect pressures on available resources. Since 2019, Buea has been hosting close to 100,000 Internally Displaced Persons (IDPs) fleeing from the conflict between the defense and security forces and the separatist groups operating in the South West and North West Regions. Consequently, this expansion of urban agglomerations in Buea brings about challenges for the urbanites whose standard of living within the urban space is affected. This article seeks to qualitatively examine how this rapid urbanization has contributed to this recurrence of cholera outbreak since 2019 and the effects on the healthcare system and measures that are in place to mitigate this outbreak. In addressing these issues, the study administered in-depth phone Interviews with medical practitioners at Buea Regional Hospital, which is the main Cholera Treatment Centre in Buea. It also conducted in-depth phone interviews with public health experts at the South West Regional Delegation of Public Health and Buea Council personnel incharge of hygiene and sanitation. The study also made use of direct observation of the researcher on the field during sensitization campaigns in the affected communities in Buea. Base on the results the influx of IDPs have stress the already existing sanitation and shortage/rationing of water in the town. The study also found out that governance and cultural issues are equally associated to the problem of recurrence of the cholera disease in Buea Municipality.

Spatiotemporal Changes in The Urban Landscape Pattern and Driving Forces of LUCC Characteristics in The Urban Agglomeration on The Northern Slope of The Tianshan Mountains from 1995 to 2018

Analyses of landscape patterns, analyses of land-use/land-cover evolution characteristics, and a driving force analysis during the expansion of urban agglomerations can assist urban agglomerations in solving ecological and environmental problems; moreover, these tools can provide a reference for urban land-use structure optimization and urban landscape planning. In this study, the rapid urbanization and urban agglomeration of small- and medium-sized cities were evaluated; specifically, the urban agglomeration of the northern slopes of the Tianshan Mountains (UANSTM) was assessed. Using multi-period (1995, 2000, 2005, 2010, 2015, 2018) land-use data and statistical yearbook data, we calculated the landscape index and comprehensive land-use degree index using the Moran index and geographic probe methods. We studied the expansion patterns and spatial distribution patterns of urban land and quantitatively explored the influence mechanisms of natural and socioeconomic factors on the degree of land use to clarify the characteristics and driving forces of land-use evolution. The results show the following: the area of urban land continued to increase between 1995 and 2018; the dominance of the landscape indexes within each time period changed with urban development; and intra-urban landscape heterogeneity is gradually increasing. In terms of the spatial and temporal distribution of the degree of land use, the expansion of urban agglomeration is centered on the city of Urumqi, spreading towards the cities of Changji and Shihezi; the rest of the counties and cities are fast urban-expansion zones. Under the influence of multiple source factors, the expansion of the UANSTM depends on the distribution of oases, which is mainly influenced by the distribution of vegetation and the density of the river network and can only rely on the ecological carrying capacity of oases for production and life. The results of the study can provide a basis for decision-making processes surrounding the future layout of the UANSTM ecological environment.

Urban Expansion and Vegetation Cover Change in and Around Jimma Town Since 1990

Urbanization is the renovation of rural society into an urban society as a result of socio-economic and political growth leading to foundation and expansion of urban agglomerations along with changing land use patterns. The main aims of this study was Investigating the extent of vegetation loss through urban expansion in and around Jimma Town over a 30 period of 6 years interval by using Geographic Information System (GIS) and Remote Sensing (RS) techniques. To achieve this objectives, Data was obtained from earth explorer (USGS) 6 years interval from1990 to 2020 of the study area. Downloaded image were extracted and each layer stacked together using the digital image-processing software ENVI 5.2. The Processed images were classified using supervised classification Algorithms into 5 hierarchical classes; Built-up area, Vegetation, Agricultural land, Grass land, and wetlands based on a modified classification scheme. Change analysis was also undertaken by applying post-classification change detection procedures. Accuracy of the image classification was assessed using error matrix, overall accuracy and kappa coefficient. The change analysis result revealed that the LULC have shown both positive and negative significant changes. Built-up were the top LULC that experienced positive change; whereas grass land, vegetation, agricultural land and wetlands have substantially declined. An important implication of the observed changes is that rapid urban expansion, compounded by poor urban planning is leading to enormous losses of key ecosystems such as wetlands and natural vegetation. The consequence of this rapid ecological degradation could potentially impact ecological functioning and environmental sustainability in and around Jimma city. Therefore, critical system thinking is required to address these complex problems in the study area and areas of rapid urbanization elsewhere in the country. Keywords : Image classification, Land use/cover, Remote sensing, GIS, Change detection DOI: 10.7176/JEES/11-16-02 Publication date: June 30 th 2021

Analysis on the causes of water contaminated by toxic and harmful substances in the Yangtze River Delta

In recent years, with the rapid development of economy in the Yangtze River Delta, the water pollution are becoming more and more serious. The expansion of urban agglomeration also makes water pollution show significant regional and complex nature. This paper takes water quality of the Yangtze River Delta as an example, the toxic and harmful substances such as ammonia nitrogen, petroleum, volatile phenol and cyanide discharged from waste water were analysed, which has led to increasing attention being paid to the phenomenon of water contaminated by toxic and harmful substances. The causes of water pollution in the Yangtze River Delta are considered to solve the problem of subsequent pollution control. In conclusion, this paper analyzed the causes of water pollution in this area from the angles of geographical environment, legal system, economic development model and so on, and expected to provide the basis for water pollution control.

The long breadth of cities: revisiting worldwide urbanization patterns, 1950–2030

ABSTRACT A comparative analysis of population dynamics worldwide contributes to profile distinctive demographic and economic trajectories of urban growth, discriminating processes of settlement concentration or dispersion under sequential cycles of urbanization. However, a wide-ranging characterization of urban cycles based on demographic dynamics worldwide is still missing. The present work is aimed at filling such a gap analysing long-term changes (1950–2030) in annual population growth rate of 1691 urban agglomerations with more than 300,000 inhabitants in 74 world countries. Results of this study indicate that metropolitan growth worldwide was associated with largely variable rates of population growth, highly positive before 2000 and progressively reducing over recent decades. Despite important differences at continental (and country) scale, demographic expansion of urban agglomerations showed two contrasting phases with a break point in the 1980s denoting a progressive reduction in spatial heterogeneity of population growth rates and a moderate slowdown in demographic dynamics. Intensity of urban expansion and spatial heterogeneity in population growth rates across metropolitan agglomerations evidences a trade-off between fast and slow demographic dynamics. These findings can be better understood to support theories of sequential city growth, making a suitable contribution to policy making, especially in countries where urban population is expanding more rapidly.

Large-area assessment of impervious surface based on integrated analysis of single-date Landsat-7 images and geospatial vector data

Driven by a constantly accelerating increase of urban population in recent decades urban sprawl has become one of the most dynamic processes in the context of global land use transformations. The expansion of urban agglomerations is closely associated with a substantial increase of impervious surface. In Europe, methods for an accurate, fast and cost-effective mapping and assessment of impervious surface on a state-wide or national scale have not been established so far. This study presents an approach for estimating the impervious surface based on a combined analysis of single-date Landsat images and road network and railway vector data using Support Vector Machines and functionalities of geographic information processing. The modeling aims at the provision of data on the impervious surface for the total of residential, industrial and transportation-related areas. The derived information is provided for the administrative units of communities. The output of the procedure is a vector data file providing the ‘percent impervious surface of built-up areas’ (PIS B) and the ‘percent impervious surface of the total of built-up and transportation-related areas’ (PIS BT) for the administrative units of communities. The developed method is tested for a study area covering almost one third of the German territory. The results prove the suitability of the approach for a widely automated and area-wide mapping of impervious surfaces. Using reference data sets of three cities (Leipzig, Ludwigshafen, Passau) we realized a mean absolute error of 19.8% and an average error of 6.4% for the percent impervious surface modeled on the basis of the Landsat images. The final product resulting from a combination of the imperviousness raster derived from the satellite images with the transportation-related vector information showed a mean difference of 1% to 4% compared to corresponding reference data and results of previous studies. For the year 2000 our research shows that 45.3% of the area occupied by settlements and transport infrastructure in the German federal state of Bavaria, 44.6% in the state of Baden-Württemberg and 42.6% in the state of Saxony was covered by impervious surface.

Modeling the runoff process in urban areas

In recent years, concern about the physical environment and its management has grown rapidly. This is reflected in the increasing attention given to the planning process. The growth and expansion of urban agglomerations represent a typical aggregation of some of man's activities having a marked environmental impact, such as air pollution, noise pollution, etc. Perhaps most vital among the different aspects of impact remains the water pollution. Urban hydrology studies portions of the hydrologic cycle, as modified by the presence of urban environments. Urbanization accounts for an increase in the total amount of runoff due to the increase of imperviousness of the drainage basins, thus aggravating the situation in flood‐prone areas. Equally important, the quality of the runoff waters is a concern, and more specifically its pollution effect on the receiving bodies of water, rivers, lakes, and groundwater recharge. The important recent research effort on the various aspects of these problems can be traced in ...