Process of a rock avalanche-debris flow in the southeast Tibetan Plateau

On 22 March 2021, a rock avalanche-debris flow (RADF) event occurred in the southeast Tibetan Plateau. To analyze its characteristics and dynamic process, multisource remote sensing data, seismic signals, and multiphase model simulations were used to evaluate the cascading effect. Results indicated that the event was triggered by a rock avalanche at 6000 m a.s.l., the total volume of which (50 × 10 6 m 3 ) consisted of 20% ice and 80% rock. The initial avalanche evolved into a debris flow with a maximum flow height of 200 m and a maximum flow velocity of 60 m/s. The main material source was sediment left following a landslide in 2018. A notable finding of the model simulation was that ice meltwater from the initial avalanche was not the main cause of the evolution of the ice-rock avalanche into debris flow. The mass flow entered the water-rich channel and carried saturated sediments, and then its scale was enlarged several times. Furthermore, the glacier landscape changed dramatically following the 2021 RADF event, and subsequent intense mass wasting was greater than the erosion attributable to the initial avalanche.