## 3 Results
### Halabiyeh Dam  
In the case of the Halabiyeh dam, the integrated use of Sentinel-2 and COSMO-SkyMed imagery allowed us to detect at least five new archaeological sites across the whole prospective reservoir area (cyan polygons in Figure 3). The identification of the new potential sites was based on four variables and features, some of which were already known from the previous literature like shape and color, while others less explored, especially by non-landscape archaeologists, including unexpected irregularities of some elements of the territory, such as roads or water channels or the location of anomalies along abandoned meanders of the river (Figure 6A-L). The grayish to brownish colors detected through Sentinel-2 false-colored infrared imagery represented the primary element for distinguishing potential archaeological sites (Figure 6A,C). In this regard, a key role is played by seasonality. Indeed, we found that the humid season enhances site visibility thanks to the reflection of the near-infrared band by healthy vegetation and crops surrounding sites. COSMO-SkyMed imagery (Figure 6B,D) also showed a darker spectral band in the area of the sites. Figure 5: Timeline of GERD dam construction and filling process as inferred by combining Google Earth imagery and CBERS 4 data, the latter being sourced under the Creative Commons Attribution License from [79]. Figure 6: Site detection across the prospective reservoir region of Halabiyeh dam 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 data (displayed as SAR radar backscatter). Examples of: tells detected based on color and circular shape compared to (**A**) surrounding vegetated and (**B**) elongated crops, and (**C**,**D**) on different radar backscatter pattern; ancient features such as meanders during (**E**,**F**) humid and (**G**,**H**) dry seasons; (**I–L**) modern features such as channels and roads in proximity to tells. COSMO-SkyMed Products ©ASI, Italian Space Agency, 2021. All rights reserved. Contains Copernicus Sentinel-2 data, 2018–2019. Shape is the second variable considered. The distinctive pseudo-circular shape of the majority of the archaeological mounds in the Near East is best appreciated during humid periods as confirmed by both Sentinel-2 (when the near-infrared signal \"is more vivid\", meaning during highly vegetative periods, Figure 6A) and COSMO-SkyMed imagery (in this case, processed as normalized backscatter images only and not as a derived product such as Digital Elevation Model like in [71]) (Figure 6B). In such agricultural landscapes, the irregular shape of the mound emerging during the humid season is even more pronounced by the regular shape of the cultivated fields located all around. SAR and optical images (Figure 6C,D) taken during the dry seasons are less effective and can only act as a feedback tool. Ancient landscape features may also help to detect potential archaeological sites. In our case, we targeted the abandoned meanders of the Euphrates located close to the main river stream (Figure 6E-H). The 75% of the documented sites are in fact placed along or close to its banks. As a result, at least two new potential sites have been identified along abandoned meanders and the current river banks. In this case, Sentinel-2 satellite imagery collected during more humid periods (Figure 6E) allowed us to more easily detect the potential sites. The other Sentinel-2 and COSMO-SkyMed images, taken during both humid and dry periods, did not allow to immediately detect the potential site, but they helped to support the remote sensing analysis by confirming the boundary of the potential site (Figure 6F) or the position of the abandoned river banks (Figure 6G,H). In the latter case, this was possible because the terrain was drier and less flooded, and thus the radar backscatter signal from the meander bottom was higher and delineated a clear spatial pattern with regard to the surrounding landscape (Figure 6H).