## 2 Materials and Methods
### Workflow  
The flowchart in Figure 2 is structured in a way that the proposed methodology can be applied to a variety of situations when cultural heritage is threatened by dams, i.e., either planned or already existing. The preferable case is always when the dam is not constructed yet and no damage, either partial or total, has occurred. The satellite-based survey can therefore feed into the PCARA. Unless other types of damage have already altered or affected the exposed heritage, the quality of the surveys mostly depend on the availability of baseline data and the opportunity to collect ad hoc data prior to the beginning of the dam construction. This is even more applicable, when the dam is under construction or being filled in, and some damage may have already been caused. In this case, the overall situation has to be treated in the frame of the second protocol considered in this paper, i.e., the PFAP. Operators are requested to conduct an assessment of the residual risk, i.e., a survey and evaluation of the portion of heritage that has not been damaged yet and may be lost if no mitigation measures or proper rescue operations are undertaken. This constraint can arise especially in absence of sufficient baseline data and archive imagery depicting the situation prior to the dam construction and filling. For the sake of completeness, the flowchart also includes situations when dams are already in operation and the PFADA, according to [PERSON] et al. [31], should be applied. However, this case is beyond the scope of the present paper and is not further developed. Figure 2: Workflow of satellite-based methodology for documentation of cultural heritage threatened by dams before (PCARA) and during (PFRAP) their construction. Notation: * it also includes cases when baseline information are scarce and insufficient, so it is more convenient to run a completely new survey; * in the case of pre-construction assessment of planned dams; § in the case of during-construction assessment; * in the case of damage assessment when the construction is completed and the dam is already in operation; * if applicable, this step could be fully automated or a mixture of the two. How PFADA is developed is intentionally not covered in the present paper. In all PCARA and PFRAP applications, baseline data from previous surveys, past studies or published collections and reports are needed. These data allow for a first inventory of sites to be made and compared with site detections that can be achieved with either archive satellite imagery or newly tasked acquisitions. In such circumstances, the satellite-based surveys provide a means to assess whether the baseline data are still valid and accurately depict the archaeological potential and site distribution, and to make a comparison between the two data sources, e.g., to identify previously unknown locations. In absence of baseline data, the satellite-based analysis is basically the only other option to pursue, especially if field survey is not allowed or feasible due to local difficult logistics, economic reasons and/or security concerns (e.g., COVID-19 pandemic restrictions or conflicts). It is in this specific regard that the proposed method aspires to offer a viable solution for archaeologists aiming to undertake activities of rescue archaeology. When a sufficient number of satellite images is available to document one or more stages of the dam life cycle, new acquisitions may be collected to form pairs with the archive images or create long time series concatenating with past satellite observations. This is beneficial for a variety of purposes. First of all, to assess whether changes have occurred during the overall period of observation or whether the ground in the study area remains unaltered. Secondly, to rely on multiple observations of the same site of potential archaeological interest. If a site is repeatedly identified in different images, it increases the likelihood that the detected feature is of anthropogenic origin.