Flood risk assessment of the Abu Simbel temple complex (Egypt) based on high-resolution spaceborne stereo imagery

Abstract

The ancient Egyptian Abu Simbel temple complex, located on the western bank of the Lake Nasser reservoir behind the Aswan High Dam, is increasingly vulnerable to natural and anthropogenic processes. Flooding by the rising waters of the reservoir is among the main factors that threaten this ancient structure. With the present construction of a series of large dams from the 2nd through 5th Nile River cataracts in Sudan as well as the building of Africa's largest hydroelectric dam, the Grand Ethiopian Renaissance Dam, there is growing concern about the safety of the structure. Accordingly, there is a dire need for the development of a novel tool to enable detailed and systematic monitoring of potential hazards that the ancient temple complex may face in the future. Therefore, in order to quantify the possible inundation of the temple complex and to locate potential segments at risk of flooding, stereo pair imagery from the Pleiades-1A satellite sensor were used to build a very high-resolution 2-meter digital elevation model (DEM). Using the derived DEM, a number of reservoir water level rise scenarios were simulated using GIS. The results showed that with a slight increase of the reservoir's water level from 175 m to 177 m ASL, only 4.9% of Abu Simbel peninsula would be inundated. Such flooded area would increase to more than 13% with a water rise of 181 m ASL. A hypothetical high water rise event of 185 m and 189 m ASL, as a result of potential catastrophic damage to the upstream neighboring dams, would submerge nearly one third (30.3%) and half (~53.7%) of the peninsula, respectively. In particular, the eastern portions of the Smaller Temple and the causeway of the Great Temple would be most severely impacted by the flooding. A new user-friendly Google Earth Engine tool, “Satellite Observations for Archaeological Preservation” (SOAP), was also developed to easily and dynamically display the flooding simulation results to in-country stakeholders and policy makers. The innovative approach used for this study is highly adaptable and with only a few minor modifications can be used for assessing vulnerability of similar archaeological sites to reservoir flooding worldwide.