scholarly journals EDDA 2.0: integrated simulation of debris flow initiation and dynamics, considering two initiation mechanisms

2017 ◽  
Author(s):  
Ping Shen ◽  
Limin Zhang ◽  
Hongxin Chen ◽  
Ruilin Fan
Keyword(s):  
Risk Assessment ◽  
Debris Flow ◽  
Debris Flows ◽  
Flow Analysis ◽  
Model Performance ◽  
Integrated Model ◽  
Field Application ◽  
Surface Erosion ◽  
Integrated Simulation ◽  
Debris Flow Initiation

Abstract. Climate change results in more frequent rainstorms and more rain-induced debris flows in mountainous areas. The prediction of likely hazard zones is important for debris flow risk assessment and management. Existing numerical methods for debris flow analysis often require the input of hydrographs at prescribed initiation locations, ignoring the initiation process and leading to large uncertainties in debris flow initiation locations, times and volumes when applied to regional debris flow analysis. The evolution of the flowing mixture in time and space is hardly addressed either. This paper presents a new integrated numerical model, EDDA 2.0, to simulate the whole process of debris-flow initiation, motion, entrainment, deposition and property changes. Two physical initiation mechanisms are modeled: transformation from slope failures and surface erosion. Three numerical tests and field application to a catastrophic debris flow event are conducted to verify the model components and evaluate the model performance. The results indicate that the integrated model is capable of simulating the initiation and subsequent flowing process of rain-induced debris flows, as well as the physical evolution of the flowing mixture. The integrated model provides a powerful tool for analyzing multi-hazard processes, hazard interactions and regional debris-flow risk assessment in the future.

scholarly journals EDDA 2.0: integrated simulation of debris flow initiation and dynamics considering two initiation mechanisms

2018 ◽  
Vol 11 (7) ◽  
pp. 2841-2856 ◽  
Author(s):  
Ping Shen ◽  
Limin Zhang ◽  
Hongxin Chen ◽  
Ruilin Fan
Keyword(s):  
Risk Assessment ◽  
Debris Flow ◽  
Debris Flows ◽  
Flow Analysis ◽  
Model Performance ◽  
Integrated Model ◽  
Field Application ◽  
Surface Erosion ◽  
Integrated Simulation ◽  
Debris Flow Initiation

Abstract. Climate change is resulting in more frequent rainstorms and more rain-induced debris flows in mountainous areas. The prediction of likely hazard zones is important for debris flow risk assessment and management. Existing numerical methods for debris flow analysis often require the input of hydrographs at prescribed initiation locations, ignoring the initiation process and leading to large uncertainties in debris flow initiation locations, times, and volumes when applied to regional debris flow analysis. The evolution of the flowing mixture in time and space is also barely addressed. This paper presents a new integrated numerical model, EDDA 2.0, to simulate the whole process of debris flow initiation, motion, entrainment, deposition, and property changes. Two physical initiation mechanisms are modelled: transformation from slope failures and surface erosion. Three numerical tests and field application to a catastrophic debris flow event are conducted to verify the model components and evaluate the model performance. The results indicate that the integrated model is capable of simulating the initiation and subsequent flowing process of rain-induced debris flows, as well as the physical evolution of the flowing mixture. The integrated model provides a powerful tool for analysing multi-hazard processes, hazard interactions, and regional debris flow risk assessment in the future.

scholarly journals The temporally varying roles of rainfall, snowmelt and soil moisture for debris flow initiation in a snow-dominated system

2018 ◽  
Vol 22 (6) ◽  
pp. 3493-3513 ◽  
Author(s):  
Karin Mostbauer ◽  
Roland Kaitna ◽  
David Prenner ◽  
Markus Hrachowitz
Keyword(s):  
Soil Moisture ◽  
Debris Flow ◽  
High Intensity ◽  
Debris Flows ◽  
Regional Scale ◽  
Early Summer ◽  
Temporal Separation ◽  
Antecedent Soil Moisture ◽  
Trigger Mechanisms ◽  
Debris Flow Initiation

Abstract. Debris flows represent frequent hazards in mountain regions. Though significant effort has been made to predict such events, the trigger conditions as well as the hydrologic disposition of a watershed at the time of debris flow occurrence are not well understood. Traditional intensity-duration threshold techniques to establish trigger conditions generally do not account for distinct influences of rainfall, snowmelt, and antecedent moisture. To improve our knowledge on the connection between debris flow initiation and the hydrologic system at a regional scale, this study explores the use of a semi-distributed conceptual rainfall–runoff model, linking different system variables such as soil moisture, snowmelt, or runoff with documented debris flow events in the inner Pitztal watershed, Austria. The model was run on a daily basis between 1953 and 2012. Analysing a range of modelled system state and flux variables at days on which debris flows occurred, three distinct dominant trigger mechanisms could be clearly identified. While the results suggest that for 68 % (17 out of 25) of the observed debris flow events during the study period high-intensity rainfall was the dominant trigger, snowmelt was identified as the dominant trigger for 24 % (6 out of 25) of the observed debris flow events. In addition, 8 % (2 out of 25) of the debris flow events could be attributed to the combined effects of low-intensity, long-lasting rainfall and transient storage of this water, causing elevated antecedent soil moisture conditions. The results also suggest a relatively clear temporal separation between the distinct trigger mechanisms, with high-intensity rainfall as a trigger being limited to mid- and late summer. The dominant trigger in late spring/early summer is snowmelt. Based on the discrimination between different modelled system states and fluxes and, more specifically, their temporally varying importance relative to each other, this exploratory study demonstrates that already the use of a relatively simple hydrological model can prove useful to gain some more insight into the importance of distinct debris flow trigger mechanisms. This highlights in particular the relevance of snowmelt contributions and the switch between mechanisms during early to mid-summer in snow-dominated systems.

Debris flow initiation from ravel-filled channel bed failure following wildfire in a bedrock landscape with limited sediment supply

2021 ◽  
Author(s):  
Marisa C. Palucis ◽  
Thomas P. Ulizio ◽  
Michael P. Lamb
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Sediment Supply ◽  
Moderate Intensity ◽  
Sandy Sediment ◽  
Channel Network ◽  
Sediment Yields ◽  
First Order ◽  
Dry Ravel ◽  
Debris Flow Initiation

Steep, rocky landscapes often produce large sediment yields and debris flows following wildfire. Debris flows can initiate from landsliding or rilling in soil-mantled portions of the landscape, but there have been few direct observations of debris flow initiation in steep, rocky portions of the landscape that lack a thick, continuous soil mantle. We monitored a steep, first-order catchment that burned in the San Gabriel Mountains, California, USA. Following fire, but prior to rainfall, much of the hillslope soil mantle was removed by dry ravel, exposing bedrock and depositing ∼0.5 m of sandy sediment in the channel network. During a one-year recurrence rainstorm, debris flows initiated in the channel network, evacuating the accumulated dry ravel and underlying cobble bed, and scouring the channel to bedrock. The channel abuts a plowed terrace, which allowed a complete sediment budget, confirming that ∼95% of sediment deposited in a debris flow fan matched that evacuated from the channel, with a minor rainfall-driven hillslope contribution. Subsequent larger storms produced debris flows in higher-order channels but not in the first-order channel because of a sediment supply limitation. These observations are consistent with a model for post-fire ravel routing in steep, rocky landscapes where sediment was sourced by incineration of vegetation dams—following ∼30 years of hillslope soil production since the last fire—and transported downslope by dry processes, leading to a hillslope sediment-supply limitation and infilling of low-order channels with relatively fine sediment. Our observations of debris flow initiation are consistent with failure of the channel bed alluvium due to grain size reduction from dry ravel deposits that allowed high Shields numbers and mass failure even for moderate intensity rainstorms.

scholarly journals Risk assessment of debris flow based on group decision making – A case study of Luanchuan County, Henan Province, China

2018 ◽  
Vol 175 ◽  
pp. 04025
Author(s):  
Pengyu Chen ◽  
Ying Kong
Keyword(s):  
Risk Assessment ◽  
Decision Making ◽  
Debris Flow ◽  
Group Decision Making ◽  
Debris Flows ◽  
Large Scale ◽  
Group Decision ◽  
Henan Province ◽  
Comprehensive Assessment ◽  
Material Sources

Luanchuan County, located in the mountains of Western Henan Province, is characterized by poor geological environment and abundant material sources and rainfalls. Debris flows have occurred many times in this county, and in some gully debris flows exhibit a large scale, requiring risk assessment. In the multi-factor comprehensive assessment methods for debris flow risk, it is really important to determine the weight of each factor since this affects the reliability of the assessment results. Given that the subjective weighting method can accurately reflect the importance of each factor, in order to improve the reliability of subjective weighting, the group decision making method is used to determine the weight of each factor. Group decision making is realized using the analytic hierarchy process and the data fusion algorithm. In this method, the expert combination weight is determined; on this basis, a model for comprehensive assessment of debris flow risk is established by the linear weighted sum method, and risk assessment is performed for gullies with medium to large-scale debris flows in the study area. The assessment results show that all debris flow gullies face minor to moderate risks. For gullies with high risk degree, it is suggested to timely clear material sources in channels and construct or reinforce retaining dams in order to prevent re-occurrence of debris flows.

scholarly journals Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

2016 ◽  
Vol 16 (2) ◽  
pp. 509-528 ◽  
Author(s):  
S. Jeffrey Underwood ◽  
Michael D. Schultz ◽  
Metteo Berti ◽  
Carlo Gregoretti ◽  
Alessandro Simoni ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Lightning Flash ◽  
Synoptic Scale ◽  
Convective Rainfall ◽  
Spatial And Temporal Scales ◽  
Circulation Patterns ◽  
Unconsolidated Material ◽  
Northeastern Italy ◽  
Debris Flow Initiation

Abstract. The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydro-geologic events. In the past, debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to these mass-wasting events has been limited to recording rainfall and developing intensity thresholds for debris mobilization. This study aims to expand the examination of atmospheric processes that preceded both locally intense convective rainfall (LICR) and debris flows in the Dolomite region. 500 hPa pressure level plots of geopotential heights were constructed for a period of 3 days prior to debris flow events to gain insight into the synoptic-scale processes which provide an environment conducive to LICR in the Dolomites. Cloud-to-ground (CG) lightning flash data recorded at the meso-scale were incorporated to assess the convective environment proximal to debris flow source regions. Twelve events were analyzed and from this analysis three common synoptic-scale circulation patterns were identified. Evaluation of CG flashes at smaller spatial and temporal scales illustrated that convective processes vary in their production of CF flashes (total number) and the spatial distribution of flashes can also be quite different between events over longer periods. During the 60 min interval immediately preceding debris flow a majority of cases exhibited spatial and temporal colocation of LICR and CG flashes. Also a number of CG flash parameters were found to be significantly correlated to rainfall intensity prior to debris flow initiation.

scholarly journals Hydrometeorological Triggering of Periglacial Debris Flows Using a Bayesian Approach: A Case Study of the Hailuogou Gully Region, China

2021 ◽  
Author(s):  
Zheng Wang ◽  
Ningsheng Chen ◽  
Guisheng Hu ◽  
Yong Zhang ◽  
Genxu Wang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
High Elevation ◽  
Tibet Plateau ◽  
Hydrological Characteristics ◽  
Effects Of Temperature ◽  
Qinghai Tibet Plateau ◽  
Hydrometeorological Conditions ◽  
Debris Flow Initiation

Abstract Mount Gonggais located in the east of the Qinghai–Tibet Plateau; many debris flows have occurred in small basins with a small glacier cover or snow cover in this area. The hydrometeorological conditions that caused debris flows in this region are complex, making forecasting and early warning difficult. Previous studies for these small-glacial-covered basins have primarily considered rainfall as the only inducing factor of debris flows, and often the effects of temperature are neglected. Thus, we carried out a probabilistic analysis of variables derived from hydrometeorological factors for the Mount Gongga region, Sichuan, China, where debris flows were recorded on 14 days between 1988 and 2019. By analyzing hydrological characteristics when debris flows occurred, three distinct dominant trigger types could be identified. The results show that 7 (50%) of the observed debris flow events during the study period, high-intensity rainfall was the dominant trigger, snowmelt by high temperature was identified as the dominant trigger for 2 (14%). Furthermore, 5 (36%) debris flow events could be attributed to the combined effects of long-lasting (or short-medium) rainfall and sustained higher temperatures. We find that the differences between the trigger types are statistically significant, and a susceptibility prediction differentiating between trigger types can outperform simple rainfall-only situations. This study contributes to an improved understanding of the hydrometeorological impact on debris flow initiation in high elevation watersheds.

scholarly journals Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

2015 ◽  
Vol 3 (9) ◽  
pp. 5717-5775
Author(s):  
S. J. Underwood ◽  
M. D. Schultz ◽  
M. Berti ◽  
C. Gregoretti ◽  
A. Simoni ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Lightning Flash ◽  
Synoptic Scale ◽  
Convective Rainfall ◽  
Spatial And Temporal Scales ◽  
Circulation Patterns ◽  
Unconsolidated Material ◽  
Northeastern Italy ◽  
Debris Flow Initiation

Abstract. The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydrogeologic events. In the past debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to these mass wasting events has been limited to recording rainfall and developing intensity thresholds for debris mobilization. This study aims to expand the examination of atmospheric processes that preceded both locally intense convective rainfall (LICR) and debris flows in the Dolomite region. 500 hPa pressure level plots of geopotential heights were constructed for a period of three days prior to debris flow events to gain insight into the synoptic scale processes which provide an environment conducive to LICR in the Dolomites. Cloud-to-ground (CG) lightning flash data recorded at the meso-scale were incorporated to assess the convective environment proximal to debris flow source regions. Twelve events were analyzed and from this analysis three common synoptic scale circulation patterns were identified. Evaluation of CG flashes at smaller spatial and temporal scales illustrated that convective processes vary in their production of CG flashes (total number) and the spatial distribution of flashes can also be quite different between events over longer periods. During the 60 min interval immediately preceding debris flow a majority of cases exhibited spatial and temporal collocation of LICR and CG flashes. Also a number of CG flash parameters were found to be significantly correlated to rainfall intensity prior to debris flow initiation.

Debris-Flow Risk Assessment

2016 ◽  
Author(s):  
Matthias Jakob ◽  
Kris Holm ◽  
Scott McDougall
Keyword(s):  
Risk Assessment ◽  
Debris Flow ◽  
Debris Flows ◽  
Numerical Models ◽  
Risk Tolerance ◽  
Nuclear Industry ◽  
Decision Makers ◽  
Economic Losses ◽  
Landslide Risk ◽  
Frequency Magnitude

Debris flows are one of the most destructive landslide processes worldwide, given their ubiquity in mountainous areas occupied by human settlement or industrial facilities around the world. Given the episodic nature of debris flows, these hazards are often un- or under-recognized. Three fundamental components of debris-flow risk assessments include frequency-magnitude analysis, numerical scenario modeling, and consequence analysis to estimate the severity of damage and loss. Recent advances in frequency-magnitude analysis take advantage of developments in methods to estimate the age of deposits and size of past and potential future events. Notwithstanding, creating reliable frequency-magnitude relationships is often challenged by practical limitations to investigate and statistically analyze past debris-flow events that are often discontinuous, as well as temporally and spatially censored. To estimate flow runout and destructive potential, several models are used worldwide. Simple empirical models have been developed based on statistical geometric correlations, and two-dimensional and three-dimensional numerical models are commercially available. Quantitative risk assessment (QRA) methods for assessing public safety were developed for the nuclear industry in the 1970s and have been applied to landslide risk in Hong Kong starting in 1998. Debris-flow risk analyses estimate the likelihood of a variety of consequences. Quantitative approaches involve prediction of the annual probability of loss of life to individuals or groups and estimates of annualized economic losses. Recent progress in quantitative debris-flow risk analyses include improved methods to characterize elements at risk within a GIS environment and estimates of their vulnerability to impact. Improvements have also been made in how these risks are communicated to decision makers and stakeholders, including graphic display on conventional and interactive online maps. Substantial limitations remain, including the practical impossibility of estimating every direct and indirect risk associated with debris flows and a shortage of data to estimate vulnerabilities to debris-flow impact. Despite these limitations, quantitative debris-flow risk assessment is becoming a preferred framework for decision makers in some jurisdictions, to compare risks to defined risk tolerance thresholds, support decisions to reduce risk, and quantify the residual risk remaining following implementation of risk reduction measures.

scholarly journals Hydrometeorological threshold conditions for debris flow initiation in Norway

2012 ◽  
Vol 12 (10) ◽  
pp. 3059-3073 ◽  
Author(s):  
N. K. Meyer ◽  
A. V. Dyrrdal ◽  
R. Frauenfelder ◽  
B. Etzelmüller ◽  
F. Nadim
Keyword(s):  
Debris Flow ◽  
Water Supply ◽  
Debris Flows ◽  
Absolute Threshold ◽  
Exceedance Probability ◽  
Snow Melt ◽  
The West ◽  
Extreme Precipitation Events ◽  
The Absolute ◽  
Debris Flow Initiation

Abstract. Debris flows, triggered by extreme precipitation events and rapid snow melt, cause considerable damage to the Norwegian infrastructure every year. To define intensity-duration (ID) thresholds for debris flow initiation critical water supply conditions arising from intensive rainfall or snow melt were assessed on the basis of daily hydro-meteorological information for 502 documented debris flow events. Two threshold types were computed: one based on absolute ID relationships and one using ID relationships normalized by the local precipitation day normal (PDN). For each threshold type, minimum, medium and maximum threshold values were defined by fitting power law curves along the 10th, 50th and 90th percentiles of the data population. Depending on the duration of the event, the absolute threshold intensities needed for debris flow initiation vary between 15 and 107 mm day−1. Since the PDN changes locally, the normalized thresholds show spatial variations. Depending on location, duration and threshold level, the normalized threshold intensities vary between 6 and 250 mm day−1. The thresholds obtained were used for a frequency analysis of over-threshold events giving an estimation of the exceedance probability and thus potential for debris flow events in different parts of Norway. The absolute thresholds are most often exceeded along the west coast, while the normalized thresholds are most frequently exceeded on the west-facing slopes of the Norwegian mountain ranges. The minimum thresholds derived in this study are in the range of other thresholds obtained for regions with a climate comparable to Norway. Statistics reveal that the normalized threshold is more reliable than the absolute threshold as the former shows no spatial clustering of debris flows related to water supply events captured by the threshold.

Towards real-time global assessment of post-fire debris flow hazards with remotely sensed data

2021 ◽  
Author(s):  
Elijah Orland ◽  
Dalia Kirschbaum ◽  
Thomas Stanley
Keyword(s):  
Remote Sensing ◽  
Debris Flow ◽  
Real Time ◽  
Debris Flows ◽  
Remotely Sensed Data ◽  
Model Framework ◽  
Burned Areas ◽  
Early Results ◽  
Fire Debris ◽  
Debris Flow Initiation

<p>As the risk of wildfires increases worldwide, burned steeplands are vulnerable to the secondary hazard of widespread sediment mobilization through debris flows. Following an initial burn, sediment and soil previously restrained by vegetation are no longer consolidated, allowing for easy mobilization into channels and along steep hillslopes through runoff.  Sufficiently powerful rainfall incorporates entrained material into turbulent flows and serves as the primary trigger for debris flow initiation. There is thus an ongoing need to establish the relationship between rainfall and debris flow initiation based on a variety of spatiotemporal preconditions. Previous work establishes regional and local thresholds to constrain the effect of rainfall in recently burned areas, but no empirical or numerical solution has worldwide application. Building from regionally-based efforts in the U.S., this work considers how remote sensing data can be applied to better approximate the post-fire debris flow hazards worldwide using freely available global datasets and software. Our work assesses the utility of remote sensing resources for analyzing burn characteristics, topography, rainfall intensity/duration, and, thus, debris flow initiation. Early results show that global observations are sufficient to delineate background rainfall rates from storms likely to cause debris flows across a variety of burn severity and topographic conditions. However, the dearth of publicly-available post-fire debris flow inventories globally limit the ability to test how the model framework performs within different climatologic and morphologic areas. This work will present preliminary analysis over the Western United States and demonstrate the feasibility of a global, near-real time model to provide situational awareness of potential hazards within recently burned areas worldwide. Future work will also consider how global or regional precipitation forecasts may increase the lead time for improved early warning of these hazards.</p>

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