Dynamic hazard assessment of debris flow based on TRIGRS and flow-R coupled models

摘要

Evaluating the hazards of debris flows is necessary for risk assessment. The May 12, 2008 earthquake in Wenchuan County, China caused many landslides and loose slopes. Under continuous or heavy rainfall, the landslides and loose slopes are easily destabilized and provide huge amounts of material source for debris flows, significantly increasing the hazard level of associated disasters. Moreover, the hazard of debris flows is not always constant, but variable over time because of the changes in influencing factors (e.g., geomorphology, rainfall conditions, and earthquakes). This study proposes a coupled model based on the TRIGRS (Transient Rainfall Infiltration and Grid based Regional Slope-stability Model) and Flow-R (Flow path assessment of gravitational hazards at a Regional scale) models for a dynamic hazard assessment of debris flows applied in a small watershed, Bayi Gully. This coupled model considers the impact of the actual rainfall process, potential debris sources on slope surfaces, and existing loose sources in the debris flow channel. The results indicate that (1) the hazard assessment by the coupled model is superior to that by the static Flow-R model; (2) the spatial distribution of landslides, debris flow sources, debris flow hazard areas, hazard probability, and debris flow energy vary with rainfall duration; and (3) the debris flow hazard area is strongly affected by topographic and geomorphic factors. Thus, the coupled model provides a powerful and robust tool for the hazard assessment and disaster prevention and mitigation of debris flows.