Urban sprawl impact assessment on the agricultural land in Egypt using remote sensing and GIS: a case study, Qalubiya Governorate

Urban sprawl is one of the main problems that threaten the limited highly fertile land in the Nile Delta of Egypt. In this research, satellite images of Landsat Thematic Mapper (TM) 1992, Landsat Enhanced Thematic Mapper (ETM+) 2001 and Egypt Sat-1 2009 have been used to study the urban sprawl and its impact on agricultural land in Qalubiya Governorate. Maximum likelihood supervised classification and post-classification change detection techniques were applied for monitoring the urban sprawl in this study area. Ground truth collected during several field trips conducted in 2009 and a topographic map from 1992 were used to assess the accuracy of the classification results. Using ancillary data, visual interpretation and expert knowledge of this area through GIS further refined the classification results. Post-classification change detection technique was used to produce change image through cross-tabulation. Combining the soil and land capability maps, on one hand, and the urban thematic layers, on the other hand, using GIS, made it possible to point out the risk of urban expansion on the expense of the highly capability class. During the (1992–2009) period, the high capable soils (Class I) decreased from 683.2 km² to 618.5 km². The moderate capable soils decreased from 100.5 km² to 93.8 km² whereas the marginally capable soils decreased from 209.1 km² to 198.3 km², during the same period. The urban encroachment over the non-capable soils was very limited during the 1992–2001 period. The pattern of urban sprawl changed during the 2001–2009 period whereas most of the urban expansion was on the expense of the non-capable soils.