Assessment of urban growth in Guangzhou using multi-temporal, multi-sensor Landsat data to quantify and map impervious surfaces

Over the past few decades, one of the most important global environmental issues has been the increasing transformation of natural landscape cover to impervious surface (IS) as a result of urbanization. A wide range of urban ecology fields, such as urban hydrology, urban climatology, urban planning, and urban ecosystem monitoring, demand accurate and timely information on land use and land cover in urban areas. As part of one of the fastest growing regions in China, Guangzhou is experiencing rapid urban expansion. We developed a combined method that integrates spectrum normalization, normalized spectral mixture analysis (NSMA), threshold segmentation, and a spatiotemporal modification approach to map the Guangzhou urban extent, through quantification of IS as a continuous variable using Landsat series images. We also developed a method to automatically extract water from Thematic Mapper (TM)/Enhanced Thematic Mapper Plus (ETM+)/Operational Land Imager (OLI) imagery. The results indicated that the integrated approach is accurate, powerful, and effective. The Guangzhou assessment showed that from 1973 to 2013 the amount of urban area with sub-pixel IS larger than or equal to 55% increased from 0.27% to 30.58%, an increase in urban extent of more than 100-fold over 40 years.