On 23 July 2009, a catastrophic debris flows were triggered by heavy rainfall in Xiangshui gully, Kangding county, southwestern China. This debris flow originating shortly after a rainstorm with an intensity of 28 mm ...On 23 July 2009, a catastrophic debris flows were triggered by heavy rainfall in Xiangshui gully, Kangding county, southwestern China. This debris flow originating shortly after a rainstorm with an intensity of 28 mm per hour transported a total volume of more than 480×103 m3 debris, depositing the poorly sorted sediment including boulders up to 2-3 m in diameter both onto an existing debris fans and into the river. 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. A comparison with adjacent rain-gage records indicates that debris flows in this setting can be produced in response to as little as 17 mm/hour or 3.5 mm/10-minute of rainfall intensity with relatively lower amount of cumulative antecedent rainfall. The field measurement and the interpretation of the Worldview image indicate that abundant landslides occurred on steep slopes within areas underlain by highly weathered granite. Using empirical equations that combine flow depth and channel slope, the mean velocity and discharge of the debris flow were estimated to be 9.2 m/s and 2150 m3/s, respectively. The results contribute to a better understanding of the conditions leading to catastrophic debris flows.展开更多
Radionuclide dating techniques characterized by137Cs and210Pbex have recently been applied in the study of lake sediments around the world.In this study,a chronological series of sediment cores was established based o...Radionuclide dating techniques characterized by137Cs and210Pbex have recently been applied in the study of lake sediments around the world.In this study,a chronological series of sediment cores was established based on137Cs and210Pbex analyses along with the evaluation of sediment properties,such as particle size distribution,total organic carbon(TOC),carbonate content,and acid-insoluble residue,to study sediment accumulation rates,sediment sources,and responses to human activities in the Jiuzhaigou National Nature Reserve in southwestern China.In terms of the particle size distribution of sediments,silt content was the highest,and clay and sand contents were relatively low.The sediments displayed high TOC contents because of the significant amounts of vegetation grown in the lakes.The carbonate content was also high due to the overall geological background of carbonates in Jiuzhaigou.Carbonate content tended to decline from top to bottom in the sediment cores,whereas the acid-insoluble residue tended to increase.These results suggested that the depth variation of the environmental parameters of the sediments in two lakes in Jiuzhaigou would correspond to each other.The results indicated that the sediment rate of Jiuzhaigou was generally high with strong siltation,indicating that serious soil loss was induced by intensive human activities in the basin over the past decades.The increases in the mass accumulation rate,contents of acid-insoluble residue,and mean particle size during the periods of 1840–1900s,late 1930s–early 1950s,1966–1978,and2003–2006 revealed the occurrence of severe soil and water loss as a result of extensive agricultural expansion,large-scale deforestation,and road construction in Jiuzhaigou.The deposition rate and the properties of lacustrine sediments could reflect the significant impact of human activities on lake sedimentation during Jiuzhaigou′s history.展开更多
基金supported by Chengdu Hydroelectric Investigation & Design Institute, the Ministry of Science and Technology of China (Grant No. 2011CB409903)the Research Fund of the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Grant No. 119-000022-18 and SKLGP2009Z2004)
文摘On 23 July 2009, a catastrophic debris flows were triggered by heavy rainfall in Xiangshui gully, Kangding county, southwestern China. This debris flow originating shortly after a rainstorm with an intensity of 28 mm per hour transported a total volume of more than 480×103 m3 debris, depositing the poorly sorted sediment including boulders up to 2-3 m in diameter both onto an existing debris fans and into the river. 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. A comparison with adjacent rain-gage records indicates that debris flows in this setting can be produced in response to as little as 17 mm/hour or 3.5 mm/10-minute of rainfall intensity with relatively lower amount of cumulative antecedent rainfall. The field measurement and the interpretation of the Worldview image indicate that abundant landslides occurred on steep slopes within areas underlain by highly weathered granite. Using empirical equations that combine flow depth and channel slope, the mean velocity and discharge of the debris flow were estimated to be 9.2 m/s and 2150 m3/s, respectively. The results contribute to a better understanding of the conditions leading to catastrophic debris flows.
基金Under the auspices of Programme of Introducing Talents of Discipline to Universities(the 111 Project)(No.B08037)National Key Technology R&D Program of China(No.2012BAC06B02)
文摘Radionuclide dating techniques characterized by137Cs and210Pbex have recently been applied in the study of lake sediments around the world.In this study,a chronological series of sediment cores was established based on137Cs and210Pbex analyses along with the evaluation of sediment properties,such as particle size distribution,total organic carbon(TOC),carbonate content,and acid-insoluble residue,to study sediment accumulation rates,sediment sources,and responses to human activities in the Jiuzhaigou National Nature Reserve in southwestern China.In terms of the particle size distribution of sediments,silt content was the highest,and clay and sand contents were relatively low.The sediments displayed high TOC contents because of the significant amounts of vegetation grown in the lakes.The carbonate content was also high due to the overall geological background of carbonates in Jiuzhaigou.Carbonate content tended to decline from top to bottom in the sediment cores,whereas the acid-insoluble residue tended to increase.These results suggested that the depth variation of the environmental parameters of the sediments in two lakes in Jiuzhaigou would correspond to each other.The results indicated that the sediment rate of Jiuzhaigou was generally high with strong siltation,indicating that serious soil loss was induced by intensive human activities in the basin over the past decades.The increases in the mass accumulation rate,contents of acid-insoluble residue,and mean particle size during the periods of 1840–1900s,late 1930s–early 1950s,1966–1978,and2003–2006 revealed the occurrence of severe soil and water loss as a result of extensive agricultural expansion,large-scale deforestation,and road construction in Jiuzhaigou.The deposition rate and the properties of lacustrine sediments could reflect the significant impact of human activities on lake sedimentation during Jiuzhaigou′s history.
