Emergency response to the reactivated Aniangzhai landslide resulting from a rainstorm-triggered debris flow, Sichuan Province, China

On June 17, 2020, an unexpected rainstorm struck the Meilong valley, which is located in Danba County, Sichuan Province, China. The cumulative rainfall of this short-duration event reached 38.1–42.4 mm and triggered the Meilong debris flow. The Meilong debris flow rushed into the valley and forced the Xiaojinchuan (XJC) River to flow along the foot of the ancient Aniangzhai (ANZ) landslide. Intense erosion reactivated the ancient ANZ landslide, producing a reactivated area of 0.62 km2. Subsequently, emergency investigation and monitoring were conducted to monitor its deformation because unstable landslide conditions could pose a serious threat to the safety of lives and property downstream. Emergency monitoring over 20 days (June 23, 2020–July 12, 2020) indicated that the reactivated deposit decelerated and entered the constant deformation state; careful attention should be paid to this reactivated deposit.