Evolution of debris flow activities in the epicentral area, 10 years after the 2008 Wenchuan earthquake

Abstract

The occurrence of debris flows after the earthquake not only damaged infrastructure but also caused large numbers of casualties. Analyzing the evolution of debris flows after the Wenchuan earthquake is significant for understanding the long-term impacts of the earthquake on the subsequent debris flow activities. This study made a continuous track of mass movements of loose deposits in all debris flow gullies from 2008 to 2018 along Provincial Road 303 (PR303) after the Wenchuan earthquake according to remote sensing images interpretation and field investigations. Four aspects, i.e. vegetation recovery, source materials, runout characteristics, and human activities were analysed to describe the evolution laws based on the 10-year inventory of debris flows. The loose deposits on the hillslope were found to be gradually transported into channels. A declining trend of mass transport rate from 2010 (24.5%) to 2018 (6.5%) was found. The occurrence frequency, magnitude, and mobility of debris flows were found to decrease. Recovery of vegetation made the loose deposits stable, whereas human activities of excavation of debris flows deposits promoted the occurrence of landslides. Three stages were divided for debris flows activities: the active period (2010–2014), the unstable period (2014–2017), and the recession period (after 2017). The decreasing trend of debris flows in the future is predicted.