Morphological variation of the Nile River first and second reaches using RS/GIS techniques

Abstract

The Nile River morphology has changed in the last century, due to the geological, topographical and climatological conditions, as well as due to the human impacts. The main focus of the present study is to detect the surface morphological changes in the first and second Nile River reaches (south of Egypt). For this purpose, several Landsat images acquired at different dates are utilized and analysed based on Remote Sensing (RS) and GIS techniques. Different satellite-derived indices including Normalized Difference Water Index (NDWI), Water Ratio Index (WRI) and Automated Water Extraction Index (AWEI) are applied to generate the (land-water) maps from Landsat data and to create the maps of changes in order to detect the changes in the water surface areas. The results indicated high performance of NDWI in generating the (land-water) maps and creating the maps of changes in both studied reaches of Nile River. For the first reach, NDWI has the highest overall accuracy (about 99.23%) and the lowest absolute error when applied for surface change detection. For the second reach, the NDWI index gave an overall accuracy of 99.13% which indicate the effectiveness and superiority of this index in detecting the surface morphological changes. Moreover, the results for the first reach of the Nile River showed a slightly change in the water surface area during the period 1984–2011. The Nile River in the considered reach lost about 2.3% of its surface area. Meanwhile, the results for the second reach indicated an intense decreasing in the water surface area in the period 1984–2010 (about 13% of the water area in the year 1984), and the utmost of this decreasing occurred over the period from the year 2005 to the year 2010 (about 8.3%).