Spatio-temporal distribution evolution and factors controlling landslides in Beichua County after Wenchuan earthquake

The earthquake triggered numerous secondary geological disasters, mainly landslides, which can have considerable impact on the environment as well as people's lives in the affected region. In this research, to obtain clear understanding of the restoration level and the evolution of landslides after an earthquake as massive as the Wenchuan earthquake, Beichuan County of Sichuan Province was considered an example, and the development characteristics and the evolution of post-earthquake landslides in the affected area were studied. Using ALOS, GF-1, and ZY-3 remote sensing images and GIS technology, the development of landslides in Beichuan County over a period of 13 years (2007–2019), comprising the period before and after the Wenchuan earthquake, was analysed. The main inducing factors of landslides before and after the disaster were discussed from many aspects. After the Wenchuan earthquake, the number and the area affected by landslides in Beichuan County drastically increased. Five years after the earthquake, there was rapid recovery in the development of landslides; however, it has not fully returned to the state before the earthquake yet. Many landslides have also occurred in medium- and high-altitude areas and medium- and high-slope areas. However, as time goes on, the high-risk areas of landslides began to migrate slowly to areas with lower altitude and gentle slope. Before the earthquake, river erosion was the main cause of landslides in the study area. After the earthquake, landslides were concentrated in the southeast and central parts of this area—places with strong earthquake intensities—which was attributed to seismogenic faults. With the recovery of landslide development, river erosion became the main contributing factor again. The findings of this research can provide insights to aid disaster prevention in the Wenchuan earthquake-stricken area and the spatio-temporal evolution of landslide disaster development in earthquake-stricken areas.