A Case Study of Debris Flow Hazards in the Bayi Gully, Sichuan Province, China

Many debris flow hazards were triggered in Earthquake area after the Wenchuan Earthquake. On 13 Aug.2010, a catastrophic debris flows were triggered by heavy rainfall in Bayi Gully, Dujiangyan county, southwestern china. This debris flows originating shortly after a rainstorm with an intensity of 75 mm/h transported a total volume of more than 116.5×104 m3. Our primary objective for this study was to analyze the characteristics of the triggering rainfall and the debris supply conditions, and to estimate debris flow volume, mean velocity, and discharge. The debris flow destroyed the most downstream dam in the catchment during a heavy rain storm. The debris flow with a peak discharge of 1082 m3/s, a total volume of 1.16 million cubic meter, a density of 1.88g·cm－3 and a yield stress of 6700 Pa caused 2 persons were missing, 1 persons were injured and 140 houses buried. After three rainy seasons, Only 30% sediment of debris deposition was taken away by 4 large-scale debris flow events. New debris flow will be triggered by rainfall in Bayi Gully in the future. It will be a long term work to prevent the debris flows in Bayi Gully.