Revealing the transformation of spatial structure of greater Cairo : insights from satellite imagery and geospatial metrics

Greater Cairo (GC) is the seventh-largest metropolitan city globally. In recent decades, GC has witnessed massive urban expansion, which has yet to be empirically measured or characterized. This research seeks to explore the patterns of urban growth and changes in urban form in GC from 1973 to 2021 using remote sensing and geospatial metrics. Six Landsat images in 1973, 1984, 1992, 2003, 2013, and 2021 were used to explore urban growth in GC. Urban Land Density Function (ULDF), Landscape Expansion Index (LEI), and Fractal Dimension Index (FDI), were utilized to analyze various aspects of urban expansion. Additionally, the ratio of Land Consumption Rate (LCR) to Population Growth Rate (PGR) was calculated to assess the correlation between urban expansion and population changes. Our results reveal a substantial addition of 203 thousand hectares of urban areas over the last half-century. The ULDF highlights GC's transformation from a condensed to a scattered urban landscape, particularly with the establishment of the New Administrative Capital in the vicinity. Edge expansion emerged as the principal type of urban growth throughout the research duration. The consistent increase in FDI from 1.44 in 1973 to 1.75 in 2021 signifies the fragmentation of the urban landscape. Moreover, the progressive rise in LCR from 0.023 in 1984 to 0.050 ​ha per person in 2021 suggests a steady expansion of low-density urban areas. Notably, the LCR-to-PGR ratio escalated from 0.878 in 1984 to 2.428 in 2021, indicating that urban expansion surpassed population growth. These results will help further understand the characteristics of GC's urban expansion and may offer a scientific foundation for policymakers to reconsider the current horizontal expansion policy in GC.