## 3 Results
### Grand Ethiopian Renaissance Dam (GERD)  
The analysis of the GERD area provided interesting evidence for both the PCARA and the PFRAP phases. The traditional villages located mainly along the banks of the Nile and in numerous tributaries were the main cultural heritage target of our research survey. These villages are not only a fundamental example of the vanishing heritage of the region, but also a proof of the substantial continuity with historical settlements, in particular with regard to the architectural technique and materials culture of the local population (see also [81] for the correlation of the archaeological and ethnographic evidence available). We particularly focused on the peculiar circular-shaped wooden dwellings (Figure 8). In this regard, Sentinel-2 false-colored infrared imagery, taken during the humid season, provided significant results. Thanks to both the light bluish color which distinguishes non/low vegetative areas from the reddish to pinkish highly vegetative zones, and their distinctive pattern characterized by single scattered dots indicating the single dwellings, we were able to detect several villages (Figure 8A). As a feedback process, we compared the Sentinel-2 imagery with Google Earth VHR optical imagery taken before the dam construction (zooms in Figure 8F). This step confirmed that the bluish dots visible from Sentinel-2 correspond to the single or at least few neighborhood dwellings. These places may be considered as a starting point for both archaeologists and ethnographers for conducting their research. Figure 7: Amplitude change detection map generated by comparing COSMO-SkyMed Enhanced Spotlight (14 January 2012 vs. 2 May 2021) images over the area where the Halabiyeh dam was planned to be constructed. COSMO-SkyMed® Products ©ASI, Italian Space Agency, 2012, 2021. COSMO-SkyMed radar imagery instead played a key role in monitoring the impoundment of the dam and, consequently, assessing the current situation of residual risk for local heritage and villages. In fact, while the Google Earth time-lapse of the GERD dam construction suggested a first filling-up test at the end of 2019 (Figure 5), the quantitative radar backscatter change detection analysis showed a clear pattern of flooding already in 2016, upstream of the dam, all along the river course (Figure 9A,B). At that time, it appears that waters had not reached and flooded the sites yet (Figure 9B). These data integrate recent Sentinel-1 image acquisitions, which documented the first filling of the dam starting from 8 July 2020, while the second filling started in mid-June 2021 [79; 80]. From an archaeological point of view, this condition had an impact on an area potentially rich in sites. As already stressed by [PERSON] et al. [79], \"there are numerous studies, which suggest that there is a lack of planning for the filling process of the GERD reservoir\". Therefore, in absence of information about the next stages of the dam life cycle, the detailed monitoring conducted by [PERSON] et al. [79], integrated with the new data analyzed in this paper based on both archive and newly acquired COSMO-SkyMed images, provided the most up-to-date and  
Figure 8: Site detection across the region when (**A**–**D**,**F**) the terrain was not yet submerged under the reservoir of GERD dam and (**E**) after the most recent impoundment and subsequent inundation based on the combination of Sentinel-2 (displayed as false-colored composites, R: Band 8—NIR; G: Band 4—red; B: Band 3—green) and COSMO-SkyMed StripMap HIMAGE data (displayed as SAR radar backscatter). COSMO-SkyMed® Products ©ASI, Italian Space Agency, 2016–2021. All rights reserved. Contains Copernicus Sentinel-2 data, 2016–2021. contextual framework for a proper planning of rescue archaeology activities both in term of time and areas that were yet to be flooded. Moreover, COSMO-SkyMed images taken in the course of 2021 confirm that the impoundment has officially started and at least two filling phases can be documented.