## 4 Results  
### Application of the FFISS in the Study Area  
According to the FFISS, comprehensive recording and mapping of the impacts of the 2009 Lilas River floods were conducted across several affected areas. These included the Vassiliko, Agios Nikolaos, Lefkadi, Afrati, and Filla residential areas, as well as along critical transportation routes such as the Afrati-Pissonas and Pissonas-Pournos roads, extending to Mistros. It was observed that the phenomena affecting the study area varied across impact categories. The built environment, and more specifically, the transportation network, suffered varying levels of impact severity in the affected areas. Observations included the inundation of the road network, rendering the roads incapable of serving transportation needs. More severe damage was noted, such as asphalt surface deterioration and scouring of embankments along the road network. Additionally, structural damages were recorded, ranging from partial bridge collapses that compromised their functionality to complete bridge failures, leading to the isolation of entire communities during a critically evolving situation (Figure 8). Different impact severity categories were observed in the built environment, particularly at the building level. Gardens, yards, and pilots, as well as ground floors and basements in residential and commercial buildings, were flooded in most of the inundated areas, disrupting the daily lives of residents. Structural damages, including total collapses of residential fences, were also recorded. Finally, even more severe damages were observed, such as structural failures in houses leading to partial collapses, highlighting the immediate need for search efforts for rescue and evacuation (Figure 9). Figure 8: Different flash flood impact severity classes in terms of transportation. **(a,b)** Inundation of the road surface in Vassiliko village (**a**) and Afrati settlement (**b**) (Class I). **(c,d)** Damages to the asphalt surface and leveesouredoured on the Afrati—Pissonas road (**c**) and in the Afrati settlement (**d**) (Class V). **(e–g**)** Bridges suffered from structural damages and partial collapses in Vassiliko (**e**), Filla (**f**) and Afrati (**g**) (Class VII). (**h**) Bridge suffered from complete collapse in the settlement of Mistros (Class VIII). Regarding the different impact severity categories in relation to mobile objects, they included very light and small items transported to the beach, flower pots carried away from residential yards, and large trash bins swept away by floodwaters. The severity level of the impacts increased when cars and even large trucks were swept away during the flood and carried into the sea. This posed an extremely dangerous risk of trapping drivers if they were in motion at the time (Figure 10). Figure 10: Different flash flood impact severity classes in terms of mobile objects. (**a**) Very light and small objects were transported at the beach of Agios Nikolaos (Class I). (**b**) Flower pots transported by floodwaters at Agios Nikolaos beach (Class II). (**c**) Large trash bins carried away by floodwaters at Agios Nikolaos beach (Class III). (**d–f**), Cars were carried away during the flood in Vassiliko (Class IV). (**g**,**h**) Large trucks transported by floodwaters in Afrati (Class VIII). Figure 9: Different flash flood impact severity classes in terms of buildings. (**a**,**b**) Garden and pilotis flooded in Lefkadi beach (Class I). (**c**) Yard walls and fences suffered from structural damages, including total collapse, in Vassiliko (Class IV). (**d**) House suffered from structural damages, including failure of supporting elements, in Vassiliko (Class VI). Finally, the different impact severity categories observed in the natural environment of the study area are related to low vegetation that was uprooted and transported to the riverbed, bridges, roads, residential fences, and other areas, as well as higher-ground plants affected by the flood. The severity level increased with trees, both smaller and larger than 3 m, being uprooted.