The evolution process of Wenchuan earthquake-landslide-debris flow geohazard chain

Since the Wenchuan Ms 8.0 earthquake which occurred on May 12, 2008, the geohazards in the earthquake-stricken region have assumed obvious "post-earthquake effect" characteristics. The great earthquake caused a large amount of rock falls and landslides on the mountain ridges and watershed slopes, and the landslide masses were scattered on the upper-middle part of the mountains. Under intense rainfall, a lot of loose deposits were brought together along the steep gully, and their movement was accelerated to form a devastating high-position debris flow, thus constituting a typical earthquake-landslide-debris flow chain. Based on a brief summarization of the co-earthquake geohazards in the Wenchuan earthquake area, this paper has discussed six types of geohazards during the rain season after the Wenchuan earthquake as well as their appearance styles. The evolution process of earthquake-landslide-debris flow disaster chain can be divided into four stages, i.e., nurtured stage, co-earthquake landslides stage, post earthquake landslide-debris flow development stage, and high debris flow evolution stage. The discrimination indexes of high debris flows are put forward, and their distribution features, motive changing trend and corresponding control countermeasures are discussed.