Melo, RaquelZêzere, JoséOliveira, SérgioCezar, LucasCastro, EmanuelVieira, Gonçalo2024-04-032024-04-032024Melo, R., Zêzere, J.L., Oliveira, S.C., Cezar, L., Castro, E., & Vieira, G. (2024) Post-fire debris flow hazard in the Zêzere glacial valley and Manteigas village (Estrela UNESCO Global Geopark, Portugal). In: X.M. Pellicer, A.S. Aytaç, A. Amorfini, & S. Delaby (eds), Geohazards in European Geoparks (pp. 54-57). Akademisyen Kitabevi9786253997137http://hdl.handle.net/10451/63927A debris flow is a mixture of water and sediments that flows down channelized steep slopes, posing a potential hazard in mountainous regions due to high velocities (from very rapid to extremely rapid), high impact forces and extended run-out distances. The initiation of debris flows is generally attributed to the critical combination of three factors: steep slopes, unconsolidated sediments and water. Heavy rainfall, which can mobilize sediments ranging from millimetres to several meters in size, is the most common triggering factor. In areas recently affected by wildfires, debris flows are frequently initiated by surface erosion along with the entrainment of loose material. The consequences of fires include vegetation consumption, ash deposition, modifications in soil and rock properties and the emergence of water-repellent soils. Therefore, the lack of vegetation, as well as the reduction in infiltration rates on a burned watershed, can increase susceptibility to debris flows, as the amount of rainfall required for their triggering may be lower compared to areas unaffected by recent wildfires. For this same reason, debris flows can occur in areas lacking historical precedent activity. A global survey conducted across UNESCO Global Geoparks (UGGp) has revealed that slope instabilities, where debris flows are included, stand as the predominant geophysical hazard, impacting 70 % of the analysed UGGp (Fassoulas et al., 2018). On the other hand, wildfires emerged as the second most prevalent hazard after floods, affecting 46 % of these UGGp.engPost-fire debris flowsZêzere glacial valleySerra da EstrelaUNESCO Global Geoparksbook part10.37609/akya.1159