## 5 Discussion
### Use of UAVs in Impact Assessment  
#### 5.3.1 Advantages of the Use of UAVs  
One key benefit of UAVs is their ability to store detailed terrain data, allowing our research to revisit and analyze the study area virtually at any time. This offered us flexibility in planning both the data collection and the analysis, particularly for areas that were hazardous or difficult to access, such as along the riverbed from the Vassiliko bridge to Afrati and downstream of Pissonas. Moreover, the data produced by the UAV ensured the preservation of observations, preventing their loss due to disruptions in terrain features (e.g., post-event cleanup activities), thereby safeguarding critical information [29; 30]. Moreover, the rapid deployment and data collection capabilities of UAVs make them particularly useful for post-flood assessments. Following the flood event, access to the affected areas was severely restricted due to infrastructure damage, debris, or hazardous conditions, rendering traditional assessment methods at that time time-consuming and costly. In contrast, the use of UAVs allowed us to mobilize quickly, within a few hours, providing real-time data to support the emergency response efforts. Equipped with high-resolution cameras and sensors, the UAVs provided us with aerial imagery and data with remarkable speed and accuracy [31; 32; 33]. This included capturing the extent of the flooding, infrastructure damage, terrain alterations, and the condition of critical facilities such as roads, utilities, and bridges. This rapid data collection can assist authorities in making timely decisions, prioritizing actions, and allocating resources more effectively [34; 35; 36]. The UAV also offered us an advantage over satellites, as it allowed us to overcome challenges such as cloud cover or limitations in satellite revisit capabilities while delivering superior resolution, even with the consumer-grade equipment we used [29]. Additionally, floods often affect remote or hard-to-reach areas, making the application of traditional assessment methods challenging, as was the case in certain parts of our study area. UAVs excel in such scenarios, as they can access areas that are hazardous or impractical for human responders to reach, whether navigating rugged terrain, flooded regions, or areas with insufficient infrastructure. Thus, our UAV provided a safe and effective means of collecting critical data [37]. Equipped with an advanced imaging system, the DJI Mavic 2 could produce high-resolution aerial imagery and accurate maps, which were essential for understanding the flood's impacts and identifying priority areas for intervention. This ability to access inaccessible areas significantly enhanced the comprehensiveness of the situational assessments [38; 39; 40]. Another advantage is that UAVs are equipped with advanced imaging systems capable of producing high-resolution aerial data, making them essential tools for post-flood assessments. Their ability to capture images with high resolution provided us with exceptional detail, which was critical for evaluating the flood damage and landscape changes. Such high-quality imagery allowed us to perform detailed analyses of the affected area, including identifying infrastructure damage, assessing the condition of buildings, and evaluating the impacts on natural features such as vegetation and water bodies [41]. Moreover, the high resolution provides qualitative insights into the role of geological formations and vegetation in the observed phenomena [25; 29]. With the data points spaced just a few centimetersapart, the products generated by the UAV provided us with an unmatched level of detail, enhancing the practicality, reducing the need for extensive personnel, and minimizing the time requirements. This was particularly valuable for surveying hazardous locations such as near the bridges of Vassiliko, Filla, and Afrati, as well as inaccessible areas along the riverbed from Vassiliko to Afrati, where traditional handheld instruments could have exposed us to significant risks [36].