Abstract
Different urban growth patterns have various impact degrees on the urban ecosystem and environment. Impervious surface, a typical artificial construction can be used to reflect urban development. Therefore, this study estimated the spatiotemporal dynamics and expansion patterns of impervious surface area (ISA) in the Guangdong-Hong Kong-Macau (GHM) Bay Area since the establishment of the “Pearl River Delta economic zone” in 1994. Landsat time-series images were used to map the distribution of the ISA based on the combinational biophysical composition index (CBCI) and the bidirectional temporal filtering method (BTFM). The results indicated that the ISA in the GHM Bay Area drastically expanded from 569.23 km2 in 1994 to 10,200.53 km2 in 2016. In addition, the aggregation index (AI) value of the high-density area showed a decreasing trend from 1994 to 2004. However, the value of each landscape metric rapidly increased after 2004. Moreover, the mean ratio of the major axis to the minor axis of standard deviational ellipses from 1994 to 2004 was higher than that from 2005 to 2016. The results of landscape metrics and standard deviational ellipses indicated that the ISA growth pattern changed from edge expanding and leapfrogging to infilling and consolidation, with a turning point in 2004. Moreover, the principal sprawl orientation of the ISA was northwest to southeast before 2004. After 2004, the expansion direction of the ISA was less obvious due to the development pattern of infilling and consolidation. The rapid increase of GDP and population are the driving forces of urban expansion. However, topography and ecological protection policies as the limiting factors, which caused the infilling of the inner city and redevelopment of old urban areas.
Highlights
In 2014, 54% of the global population, or 3.9 billion people, lived in urban areas [1].Urban sprawl can lead to various environmental issues, and one of the most prominent ecological changes is caused by the expansion of impervious surfaces [2]
The impervious surface area (ISA) of the Guangdong-Hong Kong-Macau (GHM) Bay Area experienced a drastic expansion from 569.23 km2 in 1994 to 10,200.53 km2 in 2016
Based on the aims of environmental protection and urban sustainable development, this study proposes some options for future urban development: (1) for future urban construction, the low-impact development (LID) approach should be considered during the process of urbanization; (2) the old city districts should be reconstructed to increase the proportion of vegetation and decrease the density of ISA, (3) the new urban core should be established in a suitable area to further mitigate the ISA density
Summary
In 2014, 54% of the global population, or 3.9 billion people, lived in urban areas [1].Urban sprawl can lead to various environmental issues, and one of the most prominent ecological changes is caused by the expansion of impervious surfaces [2]. In the past several years, various methods of remote sensing have been developed to map the distribution of impervious surfaces; these methods include machine learning methods (e.g., regression/decision tree methods, artificial neural networks (ANNs), and regression modeling) [16,17,18], spectral unmixing techniques (e.g., linear spectral mixture analysis (LSMA) methods and normalized spectral mixture analysis (NSMA) methods) [19,20] and object-based methods [21,22,23] These methods have limitations when applied to mapping impervious surfaces across large geographic areas, mainly because this task is a complicated and computationally intensive process [5]
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