Spontaneous initiation of debris flow surges from sedimentary deposits

<p>Spontaneous initiation of debris flow surges from sedimentary deposits</p><p>Wang Baoliang<sup>1 </sup>, Li Yong<sup>2</sup>, Guo Xiaojun<sup>2</sup></p><p>1 Yellow River Engineering Consulting Co., Ltd., Zhengzhou, 450004, China</p><p>2 Key Laboratory of Mountain Hazards and Surface Process / Institute of Mountain Hazards and  Environment, Chinese Academy of Sciences, Chengdu, 610041, China</p><p> </p><p>We report here that a small gully of sedimentary deposit has spontaneously produced a sequence of debris flow surges in great variety of appearances. The event occurred in a tributary gully of 0.16km<sup>2</sup>, without slope failures and rainstorms; the only triggering force was the groundwater at small discharge (0.5L/s). Individual surges originated separately from the sediment in different manners and appeared in a variety of flow regimes and material compositions(Fig.1). We’ve taken a detailed scrutiny on the whole processes, i.e., the surge sequence spontaneously occurring in the stream (Fig.2), and suggested a mechanism for the surge scenario. It is proposed that the sediment is heterogeneously composed of blocks of granular aggregates, featured by the grain size distribution (GSD). With different GSD parameters, sediment blocks have different critical condition of liquefaction or fluidization, which determines the manner of surge initiation (Fig.3). Fine grains are easily to run out with infiltration to form slurry and lubricate the substrate sediment layer, facilitating the mobility of succeeding surges; while coarse grains collapse as Coulomb failure and turn into high concentrated surges. And variation of the substrate granular structure causes on and off of the surges. In summary, it is the randomness of GSD and block of sediment that lead to the variety of surge initiation; and the initiation and motion of tributary surges provides a vivid scenario for intermittent surges in the mainstream channel.</p><p> </p>

APPROACHES TO RISKS ASSESSMENT DURING POTASH-MAGNESIUM AND ROCK SALTS DEPOSITS EXPLOITATION

The key segment which is prepared during hazardous facility safety justification de-velopment is the Assessment of Accident Risk. This article deals with the approaches to the assessment of accidents risks, specific hazards of ore and non-ore mines. The most significant hazards at a mine are rockfalls, rock bursts, ignitions and explosions of flammable gases, fires. Certain types of hazards can be assessed through failure rates, the ventilation system failure, for example, can be calculated on the basis of equipment failure rates, while other types of hazards, the rock bursts, for example, cannot be assessed using the existing (author-ized) methods. It is for that reason that this article reviews a principled approach to the as-sessment of mountain hazards, cites the description of the Factor Method, concerning the potash mines. The methodology cited in the article is the basis for the «Safety technologies» LLC standard «Recommended Practices of Assessment of Accidents Risks at Magnesium Mines» Accident Prevention Company Standard 4.21-2019.

Community-based Mountain Disaster Risk Management during Emergency Evacuation Process: Evidence from China

<p>The frequent occurrences of mountain disasters have posed a huge threat to the safety of life and property of settlement residents, which bring serious challenges to the post-disaster reconstruction and sustainable development of the affected area, especially in countryside resort areas. The countryside resort areas are populated with tourists whose risk perception and risk behaviours against mountain hazards are unpredictable, which has made the evacuation difficult or even worsened the situation when mountain hazards occur. How to evacuate evacuees to safety in mountain disasters is an important issue for disaster emergency management. By far, little attention has been given to emergency evacuation during mountain disasters in China. Based on mountain disaster events from 2008 to 2019, and 1385 households samples that obtained by stratified random sampling and questionnaire survey, this study has proved ‘Public Participation Monitoring and Warning System’ (PPMWS) is an essential tool to reduce related deaths. Furthermore, the roles and interfaces of different stakeholders in emergency evacuation process are discussed for the purpose to find out the unforeseen circumstances and vulnerable spots. The results show that the farmhouse owners and monitoring personnels play the key roles in emergency evacuation process. The evacuation model led by monitoring personnels is summarized and feasible measures to reduce risks and casualties of mountain disasters are proposed and applied in Longmenshan Town, Pengzhou, Sichuan. The results of this study will improve the efficiency of evacuation and provide scientific support for mountain disaster risk management in mountainous area.</p>

Vulnerability curves vs. vulnerability indicators: application of an indicator-based methodology for debris-flow hazards

The assessment of the physical vulnerability of elements at risk as part of the risk analysis is an essential aspect for the development of strategies and structural measures for risk reduction. Understanding, analysing and, if possible, quantifying physical vulnerability is a prerequisite for designing strategies and adopting tools for its reduction. The most common methods for assessing physical vulnerability are vulnerability matrices, vulnerability curves and vulnerability indicators; however, in most of the cases, these methods are used in a conflicting way rather than in combination. The article focuses on two of these methods: vulnerability curves and vulnerability indicators. Vulnerability curves express physical vulnerability as a function of the intensity of the process and the degree of loss, considering, in individual cases only, some structural characteristics of the affected buildings. However, a considerable amount of studies argue that vulnerability assessment should focus on the identification of these variables that influence the vulnerability of an element at risk (vulnerability indicators). In this study, an indicator-based methodology (IBM) for mountain hazards including debris flow (Kappes et al., 2012) is applied to a case study for debris flows in South Tyrol, where in the past a vulnerability curve has been developed. The relatively "new" indicator-based method is being scrutinised and recommendations for its improvement are outlined. The comparison of the two methodological approaches and their results is challenging since both methodological approaches deal with vulnerability in a different way. However, it is still possible to highlight their weaknesses and strengths, show clearly that both methodologies are necessary for the assessment of physical vulnerability and provide a preliminary "holistic methodological framework" for physical vulnerability assessment showing how the two approaches may be used in combination in the future.

Vulnerability curves versus vulnerability indicators: application of an indicator-based methodology for debris-flow hazards

The assessment of the physical vulnerability of elements at risk as part of the risk analysis is a very important aspect for the development of strategies and structural measures for risk reduction. Understanding, analysing and quantifying, if possible, physical vulnerability is a prerequisite for designing strategies and adopting tools for its reduction. The most common methods for assessing physical vulnerability are vulnerability matrices, vulnerability curves and vulnerability indicators, however, in most of the cases these methods are used in a conflicting way rather than in combination. The article focuses on two of these methods: the vulnerability curves and the vulnerability indicators. Vulnerability curves express physical vulnerability as a function of the intensity of the process and the degree of loss. However, a considerable amount of studies argue that vulnerability assessment should focus on the identification of these variables that influence the vulnerability of an element at risk (vulnerability indicators). In this study, an indicator-based vulnerability methodology for mountain hazards including debris flow (2012) is applied in a case study for debris flows in South Tyrol where in the past a vulnerability curve has been developed. The relatively "new" indicator-based method is being scrutinised and recommendations for its improvement are outlined. The comparison of the two methodological approaches and their results highlight their weaknesses and strengths, show clearly that both methodologies are necessary for the assessment of physical vulnerability and emphasise the need for a "holistic methodological framework" for physical vulnerability assessment.