Post-earthquake landsliding and long-term impacts in the Wenchuan earthquake area, China

The Ms 8.0 Wenchuan earthquake on May 12, 2008 triggered tens of thousands of landslides and produced large amounts of loose material. The loose material accumulated in gullies or on slopes provides abundant sources for the consequent debris flows, which will endanger resettled residents and destroy urban reconstruction. During the 5 years following the Wenchuan earthquake event, heavy rainfalls have already induced a great number of debris flows in the earthquake-damaged area, resulting in serious casualties and property losses. The co-seismic landslides and the debris flows induced by rainfalls in the Mianyuan River basin are analyzed using multi-temporal remote sensing images. More than 2000 landslides were triggered and about 4.0 × 108 m3 of loose material was generated in the Mianyuan River basin, and the volume of erodible material is 6.0 × 107-1.6 × 108 m3. There were 1.27 × 107 m3 of bed load sediments and 6.3 × 105 m3 suspended load sediments transported into the river system in the past 5 years. The active mass movements will last for a long period in the Mianyuan River basin.