The Roya is a 60 km-long semi-alluvial riverbed, with alpine/mountain influence upstream and Mediterranean influence downstream. It is characterized by steep and narrow gorges (mean slope: 3.2%) on long reaches, and a local wandering pattern when the narrow valley floodplain allows it (mean active width: 40 m). Sediment load on the catchment (area: 660 km2) comes from steep hillslopes mainly constituted of limestones, marls and flyschs, very sensitive to erosion. As in Mediterranean streams, hydrology is characterized by an acute contrast between low flows (mean daily flow: 12 m3/s; Q2 = 100 m3/s) and floods (max. known in 2019: 1130 m3/s). Because of its narrow floodplain and steep hillslopes, the Roya riverbed is mostly embanked. Despite several hydropower infrastructures, it is renowned because of its endemic trout population. We began a bedload monitoring in 2016, in order to assess 1/ sediment fluxes in a mountain Mediterranean stream and 2/ the link between hydrology and morphosedimentary evolutions of trout spawning areas, that displayed intriguing interannual spatial stability. An exceptional rainfall occurred on Oct. 2nd, 2020 on the Mediterranean Riviera region (max. 663 mm in 24h, return period ≥ 1000 years; CEREMA, 2021). With a maximum flow assessed between 1100 and 1800 m3/s (return period: between 100 and > 500-years; DDTM 06, ONF-RTM 06 & Inrae, 2022), the Roya experienced exceptional active width widening (W × 2.4, Melun et al., 2022) that generated human fatalities and huge infrastructure damage (approx. 1 billion euros worth). Based on bedload fluxes monitoring (RFID tracking and geophone) before, during and after the Oct. 2020 flood, this study contributes 1/ to define travel distances in a Mediterranean mountain stream, including a ~200-year flood, 2/ to understand the spatial and temporal dynamics of trout spawning areas and 3/ to develop a prospective conceptual model of sediment connectivity in the Roya catchment and stress few essential guidelines for the reconstruction of the valley. Fig.1. Roya Oct. 2020 flood kinetics from seismic analysis and rain/discharge simulation. References CEREMA (2021). RETEX technique ALEX - Inondations des 2 et 3 octobre 2020 - Expertise hydrologique – Rapport d’étape. Technical report (in French, hydrological expertise). DDTM 06, ONF-RTM 06, Inrae (2022). Retour d’expérience technique de la crue du 2 octobre 2020 dans la vallée de la Roya - Volet torrentiel. Technical report (in French, torrential expertise). https://drive.google.com/drive/folders/1nzwplHXasGfr4FF5W8hFpQkrPEMmCK1E?usp=sharing Melun G., Liébault F., Piton G., Chapuis M. and Passy P. (2022). Major floods of the Vésubie and Roya Rivers (Alps, France) in October 2020: hydrogeomorphological caracterisation and management perspectives. IS Rivers Conference, 4-8 July 2022, Lyon, France. https://www.graie.org/graie/graiedoc/doc_telech/isrivers2022/A5/A5_ISRivers22%20(3).pdf