Mountain disaster chain induced by the Wenchuan earthquake in the Huoshiguo Gorge

The Wenchuan earthquake triggered the Huoshigou landslide in the upstream part of the Wenjingjiang River. Following the landslide, debris flows, large fluvial deposits, and ecological changes occurred frequently, resulting in a secondary disaster chain. Field investigations combined spot surveys using a GPS and a laser distance meter, remote sensing, and topographic maps studied the processes and characteristics of the secondary disasters. Landscape changes in the Huoshigou Gorge are described in detail. The landslide volume was measured as around 7.21 million m3 with the debris flows transporting 1.25 million m3 of sediment to be deposited downstream. Intense fluvial process on the debris scoured down 0.06 million m3 of sediment from the 0.4 million m3 deposited debric. The volume of secondary disasters decreased along the disaster chain with an attenuation factor of about 1/6. Changes in the macroinvertebrate community in the area affected by the disasters showed that the river ecosystem was greatly disturbed. The flat land with an area of 0.25 km2 created by the landslide gradually stabilized after the disasters and can be used for new villages after simple strengthening.