Monitoring, modelling and managing urban growth in Alexandria, Egypt using remote sensing and GIS

Abstract

Alexandria is the second largest urban governorate in Egypt and has seen significant urban growth in its modern and contemporary history. This study investigates the urban growth phenomenon in Alexandria, Egypt using the integration of remote sensing and GIS. The study has revealed some significant findings that can help in understanding the current and future trends of urban growth in Alexandria. For demographic analysis, growth rates dropped off between 1976 and 1996. In the same manner, Alexandria's population decreased from 6.33% of total country in 1976 to 5.6% in 1996. Family size and crowding rates are declining as well. Moreover, the role of internal migration has changed and the city sends out more population than it receives. In addition, there is a clear decline in population density in the city's core, while city fringes have witnessed increases in their density. For physical expansion, Alexandria experienced a long history of deterioration from the end of the Roman era until the French expedition's departure in the beginning of the 19`" century. Alexandria began to revive again from the first half of the 19`n century during Mohamed Ali era up to date. The city expanded in all available directions. Therefore, the side effects of urban growth commenced to develop in some parts such as informal housing on the cultivated land in the east and southeast of the city. The urban physical expansion and change were detected using Landsat satellite images. The satellite images of years 1984 and 1993 were first georeferenced, achieving a very small RMSE that provided high accuracy data for satellite image analysis. Then, the images were classified using a tailored classification scheme with accuracy of 93.82% and 95.27% for 1984 and 1993 images respectively. This high accuracy enabled detecting land use/cover changes with high confidence using a postclassification comparison method. One of the most important findings here is the loss of cultivated land in favour of urban expansion. If the current loss rates continued, 75% of green lands would be lost by year 2191. These hazardous rates call for an urban growth management policy that can preserve such valuable resources to achieve sustainable urban development. The starting point of any management programme will be based on the modelling of the future growth. Modelling techniques can help in defining the scenarios of urban growth. In this study, the SLEUTH urban growth model was applied to predict future urban expansion in Alexandria until the year 2055. The application of this model in Alexandria of Egypt with its different environmental characteristics is the first application outside USA and Europe. The results revealed that future urban growth would continue in the edges of the current urban extent, which means the cultivated lands in the east and the southeast of the city will continue to lose more day by day from their area. To deal with this crisis, there is a serious need for a comprehensive urban growth management programme that based on the best practices in similar situations. Good urban governance, public participation, using GIS and remote sensing, and decentralisation (among others) are found to be the most important principles for such programme.