The Effectiveness of Post-Wildfire Slope Stabilization Measures: A Case Study in Oliveira Do Hospital

The wildfires of the 15th of October 2017 consumed more than 190,000 hectares in central Portugal. Oliveira do Hospital stands out among the most battered regions, where 43,191 hectares of forest were lost. In the aftermath of this natural disaster, several interventions aiming at stabilizing unstable slopes were conducted in different regions of the council, namely along the road which connects Penalva de Alva to Oliveira do Hospital. These works consisted of temporary barriers along the upstream slope of the road. Due to three consecutive storms in 2019, several slope instability phenomena were recorded near the study area. Despite some minor surface landslides, almost all the instability events affected slopes that had not been intervened after the 2017 wildfires. The stabilized slopes showed a better response due to the non-degradation of the mechanical characteristics of the soils and the roots system. The conclusions are then discussed concerning the behaviour of volcanic soils and the potential effects of wildfires on slopes in regions having these materials.