Case study on debris-flow hazard mitigation at a world natural heritage site, Jiuzhaigou Valley, Western China

The Jiuzhaigou earthquake on 8 August 2017, led to a significant increase in the amount of loose, solid material, which has been a rich source of debris-flow activity. In this paper, a comprehensive debris-flow prevention and control system consisting of stabilization, blocking, and deposition structures is proposed based on the topographic features of the debris-flow gullies in the Jiuzhaigou Valley. Taking the Xiajijie Lake gully as a case study, the history and formation of debris-flow disasters were analysed. This study proposes the main principles of debris-flow prevention and control as well as implementation measures, consisting of lateral diversion and deposition at the outlet of the gully. In addition, several environmental mitigation measures are proposed. Galvanized wire gabions can be placed in front of trees to lessen the debris-flow impact force, and bushes can be planted in front of deposition retaining walls to increase their aesthetic value. Alternatively, steel structures can be constructed on deposition retaining walls and filled with nutrient soil, and grass can be planted in these structures for an enhanced aesthetic appeal.