Rainfall thresholds for possible landslide initiation in wildfire-affected areas of western Greece

In August 2007, western Greece suffered one of the most devastating wildfires that has ever happened on a European level. During the 4-year period post-fire, a series of shallow landslides triggered by rainfall occurred in fire-affected areas mainly covered by Neogene sediments (marls and sandstones), causing severe economic damage. Relationships between observed landslide events and associated rainfalls were established in order to define the type of situation favorable to landslide triggering and possible critical thresholds in the rain characteristics. In order to compare the rainfall amount for the possible landslide initiation during both pre-fire and post-fire conditions, rainfall thresholds for possible landslide initiation in the unburned slopes were also proposed using a landslide inventory derived from historical archives and past rainfall data. The results suggest that the critical event rainfall ( E ) and the rainfall intensity ( I ) for landslide activity initiation is 20–30 % lower in post-fire than in pre-fire conditions.