Changes of surface recovery at coseismic landslides and their driving factors in the Wenchuan earthquake-affected area

Abstract

A major earthquake can trigger numerous landslides, which exert severe impacts on regional vegetation coverage. In some years following an earthquake, rainstorms can easily reactivate coseismic deposits and unstable hillslopes. Vegetation can improve the post-seismic slope instability by the root reinforcement effect, and it is significant to investigate the changes of surface recovery at coseismic landslides for a long-term assessment of post-earthquake geohazards. However, due to limited earth observations, it remains elusive that how long the surface vegetation of coseismic landslides caused by the 2008 Wenchuan earthquake will recover to the pre-earthquake level. We studied the long-term evolution of surface recovery in coseismic landslide-affected areas using multi-temporal Landsat images from 2000 to 2020. We calculated the vegetation recovery rates in different periods, which were used to quantify the rate of vegetation regrowth and landslide activity intensity. We found that 71.34% of the affected areas have been properly revegetated, and the area percentage of landslides in high activity, middle activity, low activity and dormant were 17.6%, 12.4%, 17.7% and 52.3%, respectively in 2020. To examine the factors controlling the surface recovery at coseismic landslides, we further analyzed the relationships between landslide recovery and eighteen influencing factors, and we found that elevation, peak ground acceleration, rainfall, lithology and gully density are the key factors that control landslide surface recovery over all others. Overall the trend of surface recovery at coseismic landslides suggests that the impact of the Wenchuan earthquake on the activities of shallow landslides almost ceases within 17 years in the Wenchuan earthquake-affected areas.