The FIRE project: a multidisciplinary approach to provide innovative probabilistic scenarios of shallow landslides over burned areas

Italy is one of the European countries most affected by wildfires and landslides.

To date, the research on wildfires is mainly addressed to evaluate best solutions for prevention, control, and mitigation. Nevertheless, not enough attention was given so far to study effects of wildfires in view of the analysis of the related geohazards.

In urban environments, the cascading effect of wildfires on landslides represents a clear example of multi-hazard. In this regard, wildfires can be regarded as a preparatory process for landslides triggering, as they significantly modify the local conditions of slopes for a not negligible time window.

In the FIRE (wildFire-related-landslide scenarIos for territorial planning and Risk managemEnt) project, funded by “Sapienza” University of Rome, a multidisciplinary research team experienced, since 2022, an innovative approach to derive quantitative scenarios of expected shallow landslides over burned areas, by evaluating the effectiveness of wildfires in preparing instabilities, also in view of defining best practices for fire extinguishing and land management plans with respect to the potential damage caused by fires at short- and long-term.

Two case studies have been selected in Italy:  Mt. Epomeo at Ischia Island (Naples) and Camaldoli hill (City of Naples). These two sites suffered in the last decades a large number of wildfires, and, in the case of Camaldoli hill, consequential shallow landslides.

Since the project activity began, two severe wildfires struck Ischia and Camaldoli, on August 2023 and June 2024, respectively.

The physical, hydraulic, and mechanical properties of soil covers potentially unstable have been defined through field surveying, in situ determinations and laboratory geotechnical tests, performed on unburned and burned samples as well as in different seasons, from May 2023 to June 2024.

For the Ischia case study, simulations of multiple wildfire propagation scenarios were carried out, originating from the most probable ignition points. These scenarios incorporated spatially explicit fuel load distributions and seasonally varying meteorological conditions. The simulations were executed using a computational model rigorously calibrated with empirical data from the 2023 Ischia wildfire, ensuring scenario-specific precision. To further support the modelling of risk scenarios, a close survey of vegetation was conducted and then critically compared to data derived from official thematic cartography and the most recent systematic botanical studies available. This enabled an updated and detailed understanding of the identification and distribution of dominant plant species composing the habitats within the Ischian landscape system, whose dedicated documentary study on the morphology and development of root systems allowed for the construction of root profiles to be associated with the recognised plant communities.

Finally, after a specific parametrisation of the physical and mechanical properties of the burned and unburned soil covers characterised by different plant associations, for each scenario of wildfire propagation, the PARSIFAL approach was applied to obtain scenarios of shallow landslides by considering both rainfall and seismic triggers in a probabilistically-defined framework.

The abovementioned activities are here reported, together with some preliminary results of the FIRE project while further steps will allow a statistically-based analysis through data-to-model informed Artificial Neural Networks.