Monitoring Urban Clusters Expansion in the Middle Reaches of the Yangtze River, China, Using Time-Series Nighttime Light Images

Yanhong Zou,Kuanda Yang,Yanhua Xie,Qihao Weng,Geng Liu,Haiquan Peng

doi:10.3390/rs9101007

Abstract

The urban clusters in the Middle Reaches of the Yangtze River (MRYR) in China include the Chang-Zhu-Tan urban agglomeration, the Wuhan metropolitan area, and the Poyang Lake urban agglomeration. While previous studies of urban expansion in China focused mainly on the coastal regions, this study aimed to investigate urban expansion patterns and factors in the MRYR, which are crucial for urban development in Central China. A neighborhood statistics analysis (NSA) method and a local-optimized threshold method were used to detect urban changes during 1992–2011 from the time-series Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) nighttime light (NTL) images. The evolution of urban expansion intensity and landscape metrics were analyzed at multiple spatial scales, including the whole region, urban agglomeration, and city scales. Finally, the expanded STochastic Impacts by Regression on Population, Affluence, and Technology (STIRPAT) model was built to explore the factors that controlled NTL intensity. The results revealed that urban areas extracted from the NTL data were consistent with those extracted from the Landsat Thematic Mapper data, with an overall accuracy of 81.74% and a Kappa of 0.40. A relatively slow urbanization pace was observed from 1992 to 2002 in the MRYR region, which then accelerated in the period of 2002 to 2007 and then slowed down between 2007 and 2011. Additionally, urban expansion exhibited a radial pattern. The results further indicated that major factors controlling NTL intensity were gross domestic product, followed by total investment in fixed assets, tertiary industry, urban construction area, non-agricultural population, and industrial output in the city clusters. The study provides important insights for further studies on the urbanization processes in the MRYR region.

Highlights

Urbanization is a complex process involving rural–urban shift, urban expansion, and land use change [1,2,3,4,5,6]
Landsat Thematic Mapper (TM) data have been widely used to extract the urban area in previous studies, and because of its higher resolution than nighttime light (NTL) images (30 m vs. 1 km), it has been used for assessing NTL-derived urban extents [32,50]
We mapped the expansion of urban clusters in the Middle Reaches of the Yangtze River (MRYR) by using time-series NTL images

Summary

Introduction

Urbanization is a complex process involving rural–urban shift, urban expansion, and land use change [1,2,3,4,5,6]. High and medium spatial resolution remotely sensed images, such as those captured by Landsat Thematic Mapper (TM) and IKONOS, have been exploited in a variety of studies to characterize urbanization patterns and processes [19,20,21]. Such studies were cost-intensive given their limited geographic coverage and requiring a large amount of time and human resources to extract urban information for a large region. Acquiring urban expansion information spanning multiple years for large city clusters using high to medium remote sensing data and socioeconomic statistical data is difficult

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