Abstract
On 8 August 2017, a runoff-generated debris flow occurred in the Puge County, Sichuan Province of southwestern China and caused huge property damage and casualties (25 people died and 5 people were injured). Emergency field investigations found that paddy fields, dry land, residential buildings and roads suffered different degrees of impact from the debris flow. This paper reveals the formation process of the debris flow by analyzing the characteristics of rainfall precipitation and sediment supply conditions in the study area and it approaches the practical application of hazard prevention and mitigation constructions. Doppler weather radar analysis indicates that a very high intensity rainfall occurred in the middle and upper zones of the basin, illustrating the importance of enhancing rainfall monitoring in high-altitude areas. The abundant supply of deposits in gully channels is among the significant causes of a transformation from mountain floods to large-scale debris flows. It was also found that the two culverts played an important role in the movement affecting the processes of debris flows which has substantially aggravated the destructive outcome. The excessive supply of solid material and local blockage with outburst along a gully must receive significant attention for the prediction of future debris flows, hazard prevention and mitigation measures.
Highlights
Debris flows have been posed a great threat to human beings, infrastructure and residences in mountainous areas
They occur in the mountainous areas of Southwest China when they are hit by heavy rainfall that can cause abundant runoff that is able to entrain large quantities of debris
Diagrammaticsketches sketchesofof different sorts of flow: (a) normal surface runoff, mountain different sorts of flow: (a) normal surface runoff, mountain flood flood or small-scale debris flow passing through the(b) culvert; (b) a large-scale passing or small-scale debris flow passing through the culvert; a large-scale debris flow debris passingflow through the culvert a special a large-scaleof debris flow passing through the culvert with the throughand the(c) culvert andcircumstance (c) a special of circumstance a large-scale debris flow passing through participation of aparticipation great stone block
Summary
Debris flows have been posed a great threat to human beings, infrastructure (e.g., roads, tunnels, bridges) and residences in mountainous areas. The movement process of runoff-generated debris flow is usually accompanied with the entrainment of a large quantity of debris material They occur in the mountainous areas of Southwest China when they are hit by heavy rainfall that can cause abundant runoff that is able to entrain large quantities of debris. The runout area and deposition depth depend on the debris over the past years due to the increase of (1) extreme rainfall [35], (2) the melting of glaciers [36].
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