## 3 Landslides in Cephalonia Island
### Types of Landslides and Induced Phenomena  
Cephalonia Island was heavily impacted by Medicare Ianos. Ianos was the most damaging natural hazard event for Cephalonia island, since the earthquakes of 2014 that caused building damages, widespread landslides, rockfalls and liquefaction over the island [38; 39; 40; 41]. Severe rainfall at Cephalonia peaked at 759 mm (17-18 September 2020) during the passing of Medicare Ianos from the Ionian Sea islands [12]. In particular, the highest severity of the Medicare-induced phenomena was reported at the northern-central part of the island towards Erissos peninsula, between Sami and Fiskardo. Debris flows and landslides occurred in several locations across the island (Figures 10 and 11). Often the debris flows covered wide areas (\(\sim\)40-70 m in width), while typically the average size  
Figure 10: Lithological map of Cephalonia Island with observed landslides and related phenomena following Medicare Ianos. Modified from [35; 37].  
of debris blocks reached 20-50 cm (Figure 11d). Moreover, the earth flows were often associated with road embankment failures (Figure 11c). The latter was also observed in cases of severe riverbank erosion/scour. The road network of the island was damaged and/or obstructed in several locations due to landslides, while a critical simple-span reinforced concrete bridge near the village of Agkonas collapsed due to scour of the west pier foundation by extensive gully flooding and debris (Figure 11e), heavily impacting the transportation network of the island.  
Debris flows appeared to be the most common feature of the effect of Medicare Ianos across Cephalonia. Debris, collected or still in place, was present along gullies and riverbeds, across the island. Most notably, Assos village, situated in the north-west of the island, was severely impacted by a major debris flow, as it was covered by approximately 1.5 m of earth/debris material (Figure 11b). The source of the debris was traced to the hills east of the village, where significant surface erosion and ground cracking were observed. At places, eroded zones reached several meters in width. Eroded limestone boulders and residual soil material were present along the entire path of the flow. UAS-enabled mapping of the entire area indicates the change along the sea-shore due to material deposition (Figure 12). An initial, rough, estimation of the debris flow volume is 20,000 m\({}^{3}\).  
Figure 11: Characteristic damages in Cephalonia Island following Medicare Ianos: (**a**) Riverbank erosion, (**b**) debris flow within a rural community, (**c**) road embankment failure, (**d**) extensive debris flow, and (**e**) bridge collapse.  
Similar to Assos, just outside of the village of Fiskardo (Figure 13), which is situated at the northern part of Erissos peninsula, a debris flow was documented. The debris flow had a lesser extent than the one that occurred in Assos, but was still significant, with the flow reaching a run-out distance of approximately 400 m. Significant erosion features were observed near the source of the debris flow. Eroded zones reached, at places, a depth of 2 m. The debris flow is also visible in Sentinel-2 satellite imagery, as shown in the pre-and-post-event images (Figure 13). Moreover, several rotational landslides were identified along the steep central coastline, particularly near Myrtos beach. Sentinel-2 pre-and-post event images of landslides and debris flows near Myrtos beach, and the collapsed bridge at Agkonas village are shown in Figure 14.  
Figure 12: UAS-enabled mapping of Assos village debris flow and surrounding area (3D model can be viewed at: [[https://skfb.ly/6](https://skfb.ly/6) WyTT]([https://skfb.ly/6](https://skfb.ly/6) WyTT) (accessed on 2 July 2022)): (**a**) orthophotomap and (**b**) digital surface model (surveyed on 30 September 2020).  
Figure 13: (**Left**): Sentinel-2 multi-temporal composite (Band 4) Fiskardo, Cephalonia. (**Right**): Sentinel-2 true color composite (Bands 4-3-2). Red colors mark the location of debris flows upstream of Fiskardo.