Abstract. The Jinsha River, which has carved a 2–4 km deep gorge,
is one of the largest SE Asian rivers. Two successive landslide-lake
outburst floods (LLFs) occurred after the 2018 Baige landslides along the
river. Using Sentinel-2 images, we examined the LLF impacts on downstream
river channels and adjacent hillslopes over a 100 km distance. The floods
increased the width of the active river channel by 54 %. Subsequently,
major landslides persisted for 15 months in at least nine locations for
displacements >2 m. Among them, three moving hillslopes
∼80 km downstream from the Baige landslides slumped more
than 10 m 1 year after the floods. Extensive undercuts by floods probably
removed hillslope buttresses and triggered a deformation response,
suggesting strong and dynamic channel–hillslope coupling. Our findings
indicate that infrequent catastrophic outburst flooding plays an important
role in landscape evolution. Persistent post-flood hillslope movement should
be considered in disaster mitigation in high-relief mountainous regions.