Recent catastrophic debris flows in Luding county, SW China: geological hazards, rainfall analysis and dynamic characteristics

Abstract

About 127 debris flow gullies have been identified, and debris flows have been an important type of geological hazards in Luding County, affecting cities, towns, rural areas, scenic spots and human's engineering projects, such as mining and waterpower utilizing equipments. In this summary paper, recent two catastrophic debris flow events occurred on June 30, 2005, in Chuni town, in the central of the county, and on August 11, 2005, in Hailuogou scenic spot, in the southwest of the county, respectively, are reviewed. The debris flow events are introduced on the basis of field investigation and RS interpretation and the triggering factors for flow occurrence are identified. Furthermore, the rainfall related to flow occurrence including antecedent rainfall and intraday rainfall is analyzed, and a power-law function which can be used as a basic warning line is established based on both antecedent effective rainfall and intraday rainfall. Then dynamic parameters such as flow velocity and flow discharge are calculated, respectively. Through comparison and discussion, some conclusions are made including (1) The antecedent rainfall played an important role for debris flows which generated predominately based on the slope-instability due to the saturated loose sediments; (2) Despite slower flow velocity and smaller magnitude, the slope-type debris flows just like 2005-6-30 debris flows usually lead to serious damages for the difficulty to forecast and to prevent; (3) The mistaken recognition on debris flow hazards and lack of prevention consciousness strengthen the hazard and damage degree. This research is of certain significance for the prevention and mitigation of debris flow hazards and for the planning of the town building and tourism development in the future.

Evolution of debris flow properties and physical interactions in debris-flow mixtures in the Wenchuan earthquake zone

“…8, ρ c for the 2008 Pubugou debris flow is estimated to be 1879-1913 kg/m 3 . Ni et al (2010) collected some data of debris flows in Luding County, Sichuan, which has similar topographic and geologic conditions with the study area. The value of ρ c ranges between 1600 and 1750 kg/m 3 (Ni et al, 2010).…”

“…Ni et al (2010) collected some data of debris flows in Luding County, Sichuan, which has similar topographic and geologic conditions with the study area. The value of ρ c ranges between 1600 and 1750 kg/m 3 (Ni et al, 2010). The debris flow deposits in Luding County contain more than 75% of cobbles (63 b d 50 ≤ 200 mm) and gravels (2 b d 50 ≤ 63 mm), about 20-25% sand, and less than 3% of silt and clay.…”

Catastrophic debris flows triggered by a 4 July 2013 rainfall in Shimian, SW China: formation mechanism, disaster characteristics and the lessons learned

“…Debris flow is a very rapid to extremely rapid flow of saturated debris in a deep channel, such as a gully or a ravine (Hungr et al 2001) and is usually initiated by the erosion and entrainment of hill slope and channel material by overland flow (e.g., Berti et al 2005; Thomas et al 2000;Hürlimann et al 2003;Godt and Coe 2007;Chen et al 2009) or sometimes triggered by outburst of dammed lake or reservoirs built in the channels (Zhou et al 1991;Godt and Coe 2007;Ni et al 2010bNi et al , 2012. As they have great velocity (several tens of km/h), long run-out distance (several km), and huge capacity to transport large and heavy rocks, they usually imply substantial destructive power and pose a significant hazard to people and infrastructure (Sepúlveda et al 2006;Tang et al 2011a, b, c).…”

Formation and characteristics of post-earthquake debris flow: a case study from Wenjia gully in Mianzhu, Sichuan, SW China

“…Rainfall is commonly regarded as the main trigger factor of debris flow, and numerous studies (e.g., Caine 1980;Fiorillo and Wilson 2004;Chen et al 2006;Seplveda et al 2006;Godt and Coe 2007;Guzzetti et al 2008;Cannon et al 2008;Pelfini and Santilli 2008;Ni et al 2010) have analyzed the empirical relationship between rainfall and debris flow occurrence. Critical thresholds have been calculated for different regions and used in forecasting to provide warnings of debris flow hazards.…”