Abstract:

Flash floods have been responsible for some of the most catastrophic events globally. The extensive range of effects and the varying severity of impacts present significant challenges in accurately understanding the damage caused by a flood event, thereby hindering our capacity to predict future consequences. When evaluating flood impacts and their severity, most existing approaches rely on qualitative descriptions (e.g., major, catastrophic, etc.) or examine the impacts from a single perspective or discipline, such as economic losses. In this study, the Flash Flood Impact Severity Scale (FFISS) is employed to evaluate, map, and categorize the impacts of two flash floods that occurred in the Lilas River in Greece in 2009 and 2020. The goal of this application is to analyze the varying severity levels and how one flood event can influence the impacts of a subsequent event. The methodology involved extensive fieldwork, including the collection of ground-based and aerial observations using UAV technology to document the impacts. These observations were subsequently georeferenced, followed by applying the Flash Flood Impact Severity Scale (FFISS) and creating detailed maps to assess and evaluate the severity of impacts associated with the two flood events. The results indicate that, despite the higher water levels during the second flood, areas previously affected show lower severity values. This reduction is attributed to the community’s gradual adaptation, improvements in infrastructure, and significant local widening of the river channel. Conversely, newly flooded areas during the second event exhibit high severity levels. Overall, applying the FFISS reveals spatial patterns of impact severity, offering insights into the local nature of floods while suggesting a potential reduction in overall risk during the post-flood period.

https://doi.org/10.5194/egusphere-egu25-13306,