scholarly journals Uncertainty analysis of the estimation of stony debris flow rainfall threshold: the application to the Backward Dynamical Approach

2020 ◽  
Author(s):  
Marta Martinengo ◽  
Daniel Zugliani ◽  
Giorgio Rosatti
Keyword(s):  
Debris Flow ◽  
Uncertainty Analysis ◽  
Flow Characteristics ◽  
Warning System ◽  
Rainfall Threshold ◽  
Rainfall Condition ◽  
Dynamical Approach ◽  
Critical Issues ◽  
Frequentist Method ◽  
The Impact

Abstract. Rainfall thresholds, namely rainfall intensity-duration conditions beyond which the probability of debris flow occurrence is considered significant, can be used as a forecasting tool in debris-flow early warning system. Many uncertainties may affect the thresholds calibration and, in turn, the reliability and effectiveness of this tool. The purpose of this study is to assess the uncertainty in the determination of the rainfall threshold for stony debris flow based on the Back Dynamical Approach (BDA) (Rosatti et al., 2019), an innovative method to estimate the rainfall duration and averaged intensity strictly related to measured debris flow. The uncertainty analysis has been computed performing two Monte Carlo cascade simulations: (i) to assess the variability in the estimate of rainfall conditions due to the uncertainty of some of the BDA parameters and (ii) to quantify the impact of this variability on the threshold parameters, obtained by using the frequentist method. Then, the deviation between these analysis outcomes and the values obtained in Rosatti et al. (2019) has been examined. The results highlight that the variability in the rainfall condition estimate is strongly related to the debris flow characteristics and the hyetograph shape. Depending on these features, the spreading of the obtained distributions can take both low and high values. Instead, the threshold parameters are characterised by a low statistical spreading. Finally, the consistency between the outcome of this study and the results obtained in Rosatti et al. (2019) has been proved and the critical issues related to the rainfall condition estimation have been discussed.

scholarly journals Uncertainty analysis of a rainfall threshold estimate for stony debris flow based on the backward dynamical approach

2021 ◽  
Vol 21 (6) ◽  
pp. 1769-1784
Author(s):  
Marta Martinengo ◽  
Daniel Zugliani ◽  
Giorgio Rosatti
Keyword(s):  
Debris Flow ◽  
Uncertainty Analysis ◽  
Rainfall Threshold ◽  
Threshold Estimate ◽  
Event Duration ◽  
Dynamical Approach ◽  
Innovative Method ◽  
The Impact ◽  
Low Dispersion

Abstract. A rainfall threshold is a function of some rainfall quantities that provides the conditions beyond which the probability of debris-flow occurrence is considered significant. Many uncertainties may affect the thresholds calibration and, consequently, its robustness. This study aims to assess the uncertainty in the estimate of a rainfall threshold for stony debris flow based on the backward dynamical approach, an innovative method to compute the rainfall duration and averaged intensity strictly related to a measured debris flow. The uncertainty analysis is computed by performing two Monte Carlo cascade simulations: (i) to assess the variability in the event characteristics estimate due to the uncertainty in the backward dynamical approach parameters and data and (ii) to quantify the impact of this variability on the threshold calibration. The application of this procedure to a case study highlights that the variability in the event characteristics can be both low and high. Instead, the threshold coefficients have a low dispersion showing good robustness of the threshold estimate. Moreover, the results suggest that some event features are correlated with the variability of the rainfall event duration and intensity. The proposed method is suitable to analyse the uncertainty of other threshold calibration approaches.

scholarly journals Experimental Study of the Debris Flow Slurry Impact and Distribution

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Haixin Zhao ◽  
Lingkan Yao ◽  
Yong You ◽  
Baoliang Wang ◽  
Cong Zhang
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Impact Force ◽  
Influence Factors ◽  
Flume Experiment ◽  
Middle Point ◽  
Laboratory Flume ◽  
Critical Issues ◽  
Maximum Impact Force ◽  
The Impact

In this study, we present a new method to calculate debris flow slurry impact and its distribution, which are critical issues for designing countermeasures against debris flows. There is no unified formula at present, and we usually design preventive engineering according to the uniform distribution of the maximum impact force. For conducting a laboratory flume experiment, we arrange sensors at different positions on a dam and analyze the differences on debris flow slurry impact against various densities, channel slopes, and dam front angles. Results show that the force of debris flow on the dam distributes unevenly, and that the impact force is large in the middle and decreases gradually to the both sides. We systematically analyze the influence factors for the calculation of the maximum impact force in the middle point and give the quantitative law of decay from the middle to the sides. We propose a method to calculate the distribution of the debris flow impact force on the whole section and provide a case to illustrate this method.

scholarly journals Load model for designing flexible steel barriers for debris flow mitigation

2019 ◽  
Vol 56 (6) ◽  
pp. 893-910 ◽  
Author(s):  
Corinna Wendeler ◽  
Axel Volkwein ◽  
Brian W. McArdell ◽  
Perry Bartelt
Keyword(s):  
Debris Flow ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Field Tests ◽  
Load Model ◽  
Dynamic Part ◽  
Pass Through ◽  
Run Up ◽  
Water Saturated ◽  
The Impact

Light-weight flexible steel net barriers catch coarse debris, but let some of the fine material and water pass through the net. They are difficult to design so that they can withstand the impact pressures of both boulder-laden granular and water-saturated debris flows. Using results from laboratory and full-scale field tests, a debris flow load model has been developed for flexible barriers in torrent channels. The model accounts for the forces of initial impact as well as the filling process discretized stepwise over time (barriers in the field and laboratory fill continuously). Laboratory tests with fast debris flow front velocities revealed a run-up behaviour that was not observed in the field (“pile-up”). The load model divides the flow forces into a hydrostatic component and a dynamic part depending on a pressure coefficient, the flow velocity, and the density of the flow. This dynamic part, which is more complex to quantify, accounts for the wide-ranging debris flow characteristics from watery and muddy debris floods to granular friction-dominated mass flows.

X-MP Radar for Developing a Lahar Rainfall Threshold for the Merapi Volcano Using a Bayesian Approach

2019 ◽  
Vol 14 (5) ◽  
pp. 811-828 ◽  
Author(s):  
Ratih Indri Hapsari ◽  
Satoru Oishi ◽  
Magfira Syarifuddin ◽  
Rosa Andrie Asmara ◽  
Djoko Legono ◽  
...  
Keyword(s):  
Debris Flow ◽  
Warning System ◽  
Rainfall Threshold ◽  
Bayesian Probability ◽  
Good Representation ◽  
Merapi Volcano ◽  
Track Record ◽  
Long Duration ◽  
Short Term Prediction ◽  
Critical Lines

Lahar flow is recognized as among the worst secondary hazards from volcanic disaster. Intense rainfall with long duration is frequently associated with lahar flow. In this study, estimation of a rainfall threshold likely to trigger lahar flow is presented in the first part. The second part discusses its implementation by assessing the growth of observed and predicted rainfall, including the uncertainties. The study area is Merapi Volcano, one of the most active volcanoes in Indonesia, including rivers on the flank of Mount Merapi that are vulnerable to debris flow. The rainfall indices needed to describe the conditions that generate lahars or not were determined empirically by evaluating the hourly and working rainfall using X-band multiparameter (X-MP) weather radar. Using past records of lahar flow, the threshold lines separating rainfall that triggers lahars or not were analyzed for the Putih, Gendol, Pabelan, and Krasak Rivers. The performance of several critical lines was evaluated using Bayesian probability based on skill rates from a contingency matrix. The study shows that the line intercept of the critical lines after a significant eruption in 2010 was higher than those lines developed before 2010, indicating that the rivers are currently at lesser risk. Good representation was shown by the thresholds verified with actual rainfall progression and lahar event information on February 17, 2016, at the Gendol and Pabelan Rivers. These rainfall critical lines were the basis for judging the debris flow occurrence by analyzing the track record of predicted rainfall progression. The uncertainty of rainfall short-term prediction from the extrapolation model was evaluated by perturbing the advection vector of rain echo motion. This ensemble forecast product could provide a plausible range of prediction possibility as assistance in gaining the confidence with which a lahar could be predicted. The scheme presented herein could serve as a useful tool for a lahar early warning system in the area of the Merapi Volcano.

Food Safety Security: A new Concept for Enhancing Food Safety Measures

2012 ◽  
Vol 82 (3) ◽  
pp. 216-222 ◽  
Author(s):  
Venkatesh Iyengar ◽  
Ibrahim Elmadfa
Keyword(s):  
Food Safety ◽  
Hazard Analysis ◽  
Warning System ◽  
Shared Responsibility ◽  
Fine Tuning ◽  
Strategic Action ◽  
Surveillance Network ◽  
Measurement Systems ◽  
Critical Control Points ◽  
The Impact

The food safety security (FSS) concept is perceived as an early warning system for minimizing food safety (FS) breaches, and it functions in conjunction with existing FS measures. Essentially, the function of FS and FSS measures can be visualized in two parts: (i) the FS preventive measures as actions taken at the stem level, and (ii) the FSS interventions as actions taken at the root level, to enhance the impact of the implemented safety steps. In practice, along with FS, FSS also draws its support from (i) legislative directives and regulatory measures for enforcing verifiable, timely, and effective compliance; (ii) measurement systems in place for sustained quality assurance; and (iii) shared responsibility to ensure cohesion among all the stakeholders namely, policy makers, regulators, food producers, processors and distributors, and consumers. However, the functional framework of FSS differs from that of FS by way of: (i) retooling the vulnerable segments of the preventive features of existing FS measures; (ii) fine-tuning response systems to efficiently preempt the FS breaches; (iii) building a long-term nutrient and toxicant surveillance network based on validated measurement systems functioning in real time; (iv) focusing on crisp, clear, and correct communication that resonates among all the stakeholders; and (v) developing inter-disciplinary human resources to meet ever-increasing FS challenges. Important determinants of FSS include: (i) strengthening international dialogue for refining regulatory reforms and addressing emerging risks; (ii) developing innovative and strategic action points for intervention {in addition to Hazard Analysis and Critical Control Points (HACCP) procedures]; and (iii) introducing additional science-based tools such as metrology-based measurement systems.

Article Review: The Impact of Fun and Enjoyment on Adult Learning

2019 ◽  
Vol 1 (2) ◽  
pp. 96
Author(s):  
Laily Yahya
Keyword(s):  
Adult Learners ◽  
Adult Learning ◽  
Teaching And Learning ◽  
Educational Programme ◽  
Continuous Quality ◽  
Teachers Beliefs ◽  
Critical Issues ◽  
Affective Experiences ◽  
The Impact

The article review of ‘The Impact of Fun and Enjoyment on Adult Learning’ (Lucardie, 2014) opens doors to the kaleidoscope of fun and enjoyment amongst adult learners. The essence of this review is an informative snapshot on the critical issues of how fun and joy have impacted adult learning through a qualitative research drawing upon traditions of phenomenology. It aims to explore the affective experiences of fun and enjoyment. This article review attempts to highlight an insightful assessment of the ideas and the arguments that are being discussed by the author. The different interpretation of this concept draws out contrasting elements between learners and teachers’ beliefs. A twist to this review is a reflective stance procured to address central issues emerging in the article related to the Malaysian context. It is through the lens of the reader, Continuous Quality Improvement (CQI):4R is proposed. This refers to the process of continuously improving the quality of teaching and learning of an educational programme. This review concludes with the framing of CQI:4R to illustrate reflect, revisit, realign and reconstruct processes that could possibly navigate the architectural landscape of the Malaysian Teacher Education.

An improved de Laval nozzle experiment

2021 ◽  
pp. 030641902110341
Author(s):  
Nicholas Goodman ◽  
Brian J Leege ◽  
Peter E Johnson
Keyword(s):  
Data Acquisition ◽  
Laval Nozzle ◽  
Flow Characteristics ◽  
Data Acquisition System ◽  
Isentropic Flow ◽  
Hands On ◽  
De Laval Nozzle ◽  
Physical Phenomena ◽  
The Impact ◽  
The Relationship

Exposing students to hands-on experiments has been a common approach to illustrating complex physical phenomena that have been otherwise modelled solely mathematically. Compressible, isentropic flow in a duct is an example of such a phenomenon, and it is often demonstrated via a de Laval nozzle experiment. We have improved an existing converging/diverging nozzle experiment so that students can modify the location of the normal shock that develops in the diverging portion to better understand the relationship between the shock and the pressure. We have also improved the data acquisition system for this experiment and explained how visualisation of the standing shock is now possible. The results of the updated system demonstrate that the accuracy of the isentropic flow characteristics has not been lost. Through pre- and post-laboratory quizzes, we show the impact on student learning as well.

Exploring the impact of introducing a physical model into statistical methods on the evaluation of regional scale debris flow susceptibility

2021 ◽  
Vol 106 (1) ◽  
pp. 881-912
Author(s):  
Jingbo Sun ◽  
Shengwu Qin ◽  
Shuangshuang Qiao ◽  
Yang Chen ◽  
Gang Su ◽  
...  
Keyword(s):  
Debris Flow ◽  
Physical Model ◽  
Statistical Methods ◽  
Regional Scale ◽  
The Impact ◽  
Debris Flow Susceptibility

The flow characteristics around bridge piers under the impact of a ship

2020 ◽  
Vol 32 (6) ◽  
pp. 1165-1177
Author(s):  
Yan-fen Geng ◽  
Hua-qiang Guo ◽  
Xing Ke
Keyword(s):  
Flow Characteristics ◽  
Bridge Piers ◽  
The Impact

scholarly journals Virus Transmission Risk in Urban Rail Systems: Microscopic Simulation-Based Analysis of Spatio-Temporal Characteristics

2021 ◽  
pp. 036119812110101
Author(s):  
Jiali Zhou ◽  
Haris N. Koutsopoulos
Keyword(s):  
Public Transportation ◽  
Virus Transmission ◽  
Flow Characteristics ◽  
Transportation Systems ◽  
Transmission Risk ◽  
Microscopic Simulation ◽  
Spatial And Temporal Patterns ◽  
Subway System ◽  
Public Transportation Systems ◽  
The Impact

The transmission risk of airborne diseases in public transportation systems is a concern. This paper proposes a modified Wells-Riley model for risk analysis in public transportation systems to capture the passenger flow characteristics, including spatial and temporal patterns, in the number of boarding and alighting passengers, and in number of infectors. The model is used to assess overall risk as a function of origin–destination flows, actual operations, and factors such as mask-wearing and ventilation. The model is integrated with a microscopic simulation model of subway operations (SimMETRO). Using actual data from a subway system, a case study explores the impact of different factors on transmission risk, including mask-wearing, ventilation rates, infectiousness levels of disease, and carrier rates. In general, mask-wearing and ventilation are effective under various demand levels, infectiousness levels, and carrier rates. Mask-wearing is more effective in mitigating risks. Impacts from operations and service frequency are also evaluated, emphasizing the importance of maintaining reliable, frequent operations in lowering transmission risks. Risk spatial patterns are also explored, highlighting locations of higher risk.

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