Risk assessment of simultaneous debris flows in mountain townships

Many mountain towns in China are located on the joint alluvial fans of multiple and adjacent past debris flows, making them vulnerable to large, multiple, and simultaneous debris flows during heavy rainfall. Without emergency management planning, such flows, often appearing with interconnecting and chain-reaction processes, can lead to extensive loss of life and property. In the Wenchuan earthquake-affected area, such disasters are common. We analyzed the compound effects of simultaneous debris flow events, and proposed three quantitative methods of debris risk assessment based on kinetic energy, flow depth, and inundation depth. Validated using a field study of actual debris flow disasters, these analyses are useful in determining the type, quantity, distribution, economic worth, and susceptibility of hazard-affected objects in a region. Subsequently, we established a method to determine the vulnerability of different hazard-affected objects, particularly concerning the susceptibility indexes of buildings or structures. By analyzing the elements underlying hazard formation conditions, damage potential, and the socio-economic conditions of mountain townships, we proposed a systematic and quantitative method for risk analysis of mountain townships. Finally, the proposed method was applied to a case study of Qingping Township, which was affected by 21 simultaneous debris flows triggered by a 50-year return period precipitation event. The proposed method analyzed the superposition and chain-reaction effects of disasters and divided the affected area of the township into three risk zones. The analysis indicated that the calculated risk zones coincide with the actual distribution and severity of damage in the debris flow event, which suggests that the risk assessment is consistent with results from the actual disaster.

[1]  M. Bisson,et al.  A rapid method to assess fire-related debris flow hazard in the Mediterranean region: An example from Sicily (southern Italy) , 2005 .

[2]  M. Jakob,et al.  Debris-flow Hazards and Related Phenomena , 2005 .

[3]  Gabi Hufschmidt,et al.  A comparative analysis of several vulnerability concepts , 2011 .

[4]  Sven Fuchs,et al.  Spatial scan statistics in vulnerability assessment: an application to mountain hazards , 2012, Natural Hazards.

[5]  Andreas Kääb,et al.  Regional-scale GIS-models for assessment of hazards from glacier lake outbursts: evaluation and application in the Swiss Alps , 2003 .

[6]  Zhou Xiao-jun.  Characteristics and Countermeasures of Debris Flow in Wenchuan Area After the Earthquake , 2010 .

[7]  Zhang Yu,et al.  Model and method of debris flow risk zoning based on momentum analysis , 2008, Wuhan University Journal of Natural Sciences.

[8]  Maria Laura Mastellone,et al.  Basic principles of multi-risk assessment: a case study in Italy , 2012, Natural Hazards.

[9]  Calculation of the debris flow concentration based on clay content , 2004 .

[10]  T. Glade,et al.  Improvement of vulnerability curves using data from extreme events: debris flow event in South Tyrol , 2012, Natural Hazards.

[11]  P. Julien,et al.  Two‐Dimensional Water Flood and Mudflow Simulation , 1993 .

[12]  Adrienne Grêt-Regamey,et al.  Spatially explicit avalanche risk assessment linking Bayesian networks to a GIS , 2006 .

[13]  Xiaoqing Chen,et al.  The Wenchuan Earthquake (May 12, 2008), Sichuan Province, China, and resulting geohazards , 2011 .

[14]  Thomas Glade,et al.  Vulnerabilitätskonzepte in Sozial- und Naturwissenschaften , 2006 .

[15]  Francesco Gentile,et al.  Debris-flow risk analysis in south Gargano watersheds (Southern-Italy) , 2008 .

[16]  Dieter Rickenmann,et al.  Empirical Relationships for Debris Flows , 1999 .

[17]  Alberto Lamberti,et al.  ASSESSMENT OF RISK DUE TO DEBRIS FLOW EVENTS , 2003 .

[18]  Marcel Hürlimann,et al.  Detailed debris flow hazard assessment in Andorra: A multidisciplinary approach , 2006 .

[19]  T. Glade,et al.  From single- to multi-hazard risk analyses: a concept addressing emerging challenges , 2010 .

[20]  Robert K. Mark,et al.  Statistical and Simulation Models for Mapping Debris-Flow Hazard , 1995 .

[21]  P. Cui,et al.  Characteristic rainfall for warning of debris flows , 2010 .

[22]  John A. Michael,et al.  Predicting the probability and volume of postwildfire debris flows in the intermountain western United States , 2010 .

[23]  B. Pradhan.  Remote sensing and GIS-based landslide hazard analysis and cross-validation using multivariate logistic regression model on three test areas in Malaysia , 2010 .

[24]  A. Valente,et al.  Coastal hazard assessment and mapping in Northern Campania, Italy , 2008 .

[25]  Irasema Alcántara-Ayala,et al.  Geomorphological Hazards and Disaster Prevention , 2014 .

[26]  T. Glade,et al.  Physical vulnerability assessment for alpine hazards: state of the art and future needs , 2011 .

[27]  Songdong Shao,et al.  Particle Model for Alluvial Fan Formation , 1997 .

[28]  Xu Qiang,et al.  THE 13 AUGUST 2010 CATASTROPHIC DEBRIS FLOWS IN SICHUAN PROVINCE:CHARACTERISTICS,GENETIC MECHANISM AND SUGGESTIONS , 2010 .

[29]  J. Hübl,et al.  Towards an empirical vulnerability function for use in debris flow risk assessment , 2007 .

[30]  B. Calvo,et al.  A real-world application of Monte Carlo procedure for debris flow risk assessment , 2009, Comput. Geosci..

[31]  J. Pedraza,et al.  Hazard Zoning for Landslides Connected to Torrential Floods in the Jerte Valley (Spain) by using GIS Techniques , 2003 .

[32]  Yu Yang,et al.  Prediction of debris-flow danger area by combining hydrological and inundation simulation methods , 2011 .

[33]  Resumen Autores,et al.  Problems and challenges in analyzing multiple territorial risks. Methodological proposals for multi-hazard mapping , 2010 .

[34]  Sven Fuchs,et al.  A quantitative vulnerability function for fluvial sediment transport , 2011 .

[35]  Y. You,et al.  Identification of potential sites of debris flows in the upper Min River drainage, following environmental changes caused by the Wenchuan earthquake , 2010 .