Declining geohazard activity with vegetation recovery during first ten years after the 2008 Wenchuan earthquake

Abstract

Understanding the evolution of post-seismic geohazards with vegetation recovery is of great significance for long-term geohazard risk assessment. The Wenchuan earthquake in 2008 triggered numerous landslides and severely damaged the vegetation in the earthquake-stricken region. Between 2008 and 2017, we evaluated the vegetation recovery process, the evolution of rain-induced landslides and debris flows, and the relationship between them by analyzing satellite images and conducting detailed field investigations. Shortly after the earthquake, numerous landslides and debris flows were triggered by rainstorms and the vegetation was severely damaged near the epicenter. In the first 5 years (2008–2013) the vegetation recovered quickly but was not well rehabilitated. Rain-induced landslides and debris flows occurred actively but exhibited a clear declining trend in both frequency and magnitude. After 2013, the vegetation gradually recovered to the pre-seismic normal level in terms of quantity, but with higher variability and isolated spots to be further rehabilitated. Over this period, rain-induced geohazards mainly occurred in the catchments where the level of vegetation recovery was uneven, with occasional bare deposits. Therefore, a close relation is observed between declining rain-induced geohazards and the recovery of vegetation, in both time and space. The findings provide important information for post-seismic infrastructure re-construction and disaster risk reduction in future mountain earthquake events.