Floods are amongst the most dangerous natural disasters. After the 2013 flood event in Val d’Aran (Pyrenees), fieldwork and the analysis of historical aerial photographs allowed us to study flood hazard by considering a broad range of processes and timescales. Results show that the long-term entrenchment tendency resulting from the geologic setting determines the short-term flood effects. Improved data arising from these kinds of studies can help decision makers for better flood risk management.