scholarly journals Debris flows in the central sector of the northern slopes of the Main Caucasus Ridge: peculiarities of the current situation

2016 ◽  
Vol 50 (1) ◽  
pp. 143-154 ◽  
Author(s):  
E. V. Zaporozhchenko
Keyword(s):  
Debris Flow ◽  
21St Century ◽  
Debris Flows ◽  
Meteorological Data ◽  
Current Situation ◽  
Modern Trend ◽  
Mountainous Areas ◽  
Single Model ◽  
Rock Falls ◽  
Flow Processes

This paper provides examples of real events of debris flows in the 21st century. The analysis of the debris flows reveals that there is a variety of manifestation of debris flow processes and triggering factors. It also demonstrates the lack of prospects for the modern trend of creating a single model for forecasting the occurrence, development, impacts and parameters of debris flows that would be equally suitable for other phenomena of gravitational nature such as avalanches, landslides or rock falls. Moreover, it shows that the monitoring is unrepresentative, which is unacceptable, and demonstrates the often lack of hydro-meteorological data on mountainous areas.

scholarly journals 2D Runout Modelling of Hillslope Debris Flows, Based on Well-Documented Events in Switzerland

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 70 ◽  
Author(s):  
Florian Zimmermann ◽  
Brian W. McArdell ◽  
Christian Rickli ◽  
Christian Scheidl
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Mass Movement ◽  
Clay Content ◽  
Systematic Evaluation ◽  
Mountain Areas ◽  
Flow Processes ◽  
Friction Parameters ◽  
Cohesive Interaction ◽  
Hillslope Debris Flow

In mountain areas, mass movements, such as hillslope debris flows, pose a serious threat to people and infrastructure, although size and runout distances are often smaller than those of debris avalanches or in-channel-based processes like debris floods or debris flows. Hillslope debris-flow events can be regarded as a unique process that generally can be observed at steep slopes. The delimitation of endangered areas and the implementation of protective measures are therefore an important instrument within the framework of a risk analysis, especially in the densely populated area of the alpine region. Here, two-dimensional runout prediction methods are helpful tools in estimating possible travel lengths and affected areas. However, not many studies focus on 2D runout estimations specifically for hillslope debris-flow processes. Based on data from 19 well-documented hillslope debris-flow events in Switzerland, we performed a systematic evaluation of runout simulations conducted with the software Rapid Mass Movement Simulation: Debris Flow (RAMMS DF)—a program originally developed for runout estimation of debris flows and snow avalanches. RAMMS offers the possibility to use a conventional Voellmy-type shear stress approach to describe the flow resistance as well as to consider cohesive interaction as it occurs in the core of dense flows with low shear rates, like we also expect for hillslope debris-flow processes. The results of our study show a correlation between the back-calculated dry Coulomb friction parameters and the percentage of clay content of the mobilised soils. Considering cohesive interaction, the performance of all simulations was improved in terms of reducing the overestimation of the observed deposition areas. However, the results also indicate that the parameter which accounts for cohesive interaction can neither be related to soil physical properties nor to different saturation conditions.

scholarly journals Debris Flow Damage Assessment by Considering Debris Flow Direction and Direction Angle of Structure in South Korea

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 328 ◽  
Author(s):  
Dong Nam ◽  
Man-Il Kim ◽  
Dong Kang ◽  
Byung Kim
Keyword(s):  
South Korea ◽  
Debris Flow ◽  
Debris Flows ◽  
Impact Force ◽  
Mountainous Areas ◽  
Mountainous Regions ◽  
Impact Forces ◽  
The Impact

Recently, human and property damages have often occurred due to various reasons—such as landslides, debris flow, and other sediment-related disasters—which are also caused by regional torrential rain resulting from climate change and reckless development of mountainous areas. Debris flows mainly occur in mountainous areas near urban living communities and often cause direct damages. In general, debris flows containing soil, rock fragments, and driftwood temporarily travel down to lower parts along with a mountain torrent. However, debris flows are also often reported to stream down from the point where a slope failure or a landslide occurs in a mountain directly to its lower parts. The impact of those debris flows is one of the main factors that cause serious damage to structures. To mitigate such damage of debris flows, a quantitative assessment of the impact force is thus required. Moreover, technologies to evaluate disaster prevention facilities and structures at disaster-prone regions are needed. This study developed two models to quantitatively analyze the damages caused by debris flows on structures: Type-1 model for calculating the impact force, which reflected the flow characteristics of debris flows and the Type-2 model, which calculated the impact force based on the topographical characteristics of mountainous regions. Using RAMMS a debris flow runoff model, the impact forces assessed through Type-1 and Type-2 models were compared to check reliability. Using the assessed impact forces, the damage ratio of the structures was calculated and the amount of damage caused by debris flows on the structures was ultimately assessed. The results showed that the Type-1 model overestimated the impact force by 10% and the Type-2 model by 4% for Mt. Umyeon in Seoul, compared to the RAMMS model. In addition, the Type-1 model overestimated the impact force by 3% and Type-2 by 2% for Mt. Majeok in Chuncheon, South Korea.

scholarly journals Effects of Y-type spillway lateral contraction ratios on debris flow patterns and scour features behind a check dam

2016 ◽  
Author(s):  
Huayong Chen ◽  
Jinfeng Liu ◽  
Wanyu Zhao
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Patterns ◽  
Check Dam ◽  
Mountainous Areas ◽  
Dimensionless Analysis ◽  
Lateral Contraction ◽  
Contraction Ratio ◽  
New Type ◽  
Good Agreement

Abstract. Debris flows often cause devastating damage to property and can injure or kill residents in mountainous areas. The construction of check dams in debris flow valleys is considered a useful strategy for mitigating the damages downstream. In this paper, a new type of spillway structure with lateral contraction was proposed to distribute debris flows after the check dam storage filled up. Four different lateral contraction ratios of the spillway were considered in experiments that investigated debris flow patterns, scour characteristics, and energy dissipation rates when debris flows passed through the spillway. The results indicated that lateral contraction considerably influenced the extension of debris flow nappes. The drop length of the nappe at η = 0.7 (η means lateral contraction ratio) was approximately 1.4 times larger than at η = 0.4. The collision, friction, and mixing forces between the debris flow nappes and debris flows in downstream plunge pools dissipated much of the debris flow kinetic energy, ranging from 42.03 % to 78.08 % at different contraction ratios. Additionally, based on a dimensionless analysis, an empirical model was proposed to predict the maximum scour depth behind the check dam. It indicated that the results calculated by the model exhibited good agreement with the experimental results.

scholarly journals Recent changes in rainfall characteristics and their influence on thresholds for debris flow triggering in the Dolomitic area of Cortina d'Ampezzo, north-eastern Italian Alps

2010 ◽  
Vol 10 (3) ◽  
pp. 571-580 ◽  
Author(s):  
M. Floris ◽  
A. D'Alpaos ◽  
C. Squarzoni ◽  
R. Genevois ◽  
M. Marani
Keyword(s):  
Debris Flow ◽  
Short Duration ◽  
High Intensity ◽  
Debris Flows ◽  
Meteorological Data ◽  
Rain Gauge ◽  
Annual Rainfall ◽  
Interarrival Time ◽  
Italian Alps ◽  
Rainfall Events

Abstract. In this paper, we examine variations in climate characteristics near the area of Cortina d'Ampezzo (Dolomites, Eastern Italian Alps), with particular reference to the possible implications for debris-flow occurrence. The study area is prone to debris-flow release in response to summer high-intensity short-duration rainfalls and, therefore, it is of the utmost importance to investigate the potential increase in debris-flow triggering rainfall events. The critical rainfall threshold is agreed to be a crucial triggering factor for debris-flows. Data from a monitoring system, placed in a catchment near Cortina (Acquabona), show that debris-flows were triggered by rainfalls with peak rainfall intensities ranging from 4.9 to 17.4 mm/10 min. The analyses of meteorological data, collected from 1921 to 1994 at several stations in the study area, show a negative trend of annual rainfall, a considerable variation in the monthly rainfall distribution, and an increase in the temperature range, possibly related to global climate changes. Moreover, high-intensity and short-duration rainfall events, derived from data collected from 1990 and 2008, show an increase in exceptional rainfall events. The results obtained in a peak-over-threshold framework, applied to the rainfall data measured at the Faloria rain gauge station from 1990 to 2008, clearly show that the interarrival time of over-threshold events computed for different threshold values decreased in the last decade. This suggests that local climatic changes might produce an increase in the frequency of rainfall events, potentially triggering debris flows in the study area.

BARSEM DEBRIS FLOW DISASTER IN THE PAMIRS IN 2015 AND ITS ANALOGUES IN THE CENTRAL CAUCASUS

2019 ◽  
Vol XIII (1/2019) ◽  
pp. 26-36
Author(s):  
MIKHAIL DOKUKIN ◽  
SERGEY CHERNOMORETS ◽  
ELENA SAVERNYUK ◽  
EDUARD ZAPOROZHCHENKO ◽  
RUSLAN BOBOV ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Large Scale ◽  
River Valley ◽  
Mountain Areas ◽  
Form Analysis ◽  
Flow Processes ◽  
Central Caucasus ◽  
Left Tributary ◽  
Debris Flow Disaster

we characterize specific features of formation and consequences of the debris flow disaster occurred on the Barsemdara River in the Gunt River valley (Barsem village, Gorno-Badakhshan Autonomous Region, Tajikistan) on July 16–24, 2015. The paper presents the data on debris flow events with similar formation mechanism that took place in the following river valleys: Adyr-Su in 1940, 1983 and 2011, Tyutyun-Su in 1953, Khaznidon in 1975 et al. A common feature of the considered debris flows is the confinedness of debris flow site to special glacial accumulation forms — moraine pedestals containing a large amount of buried ice. Due to large-scale and long-term debris flow processes moraine pedestals take the shape of gullies. The largest example of considered landform is the debris flow gully (1 km-length) situated in the upper reaches of the Tyutyun-Su River in the Cherek Balkarskiy River basin (Central Caucasus). Similar debris flow processes were also observed in other mountain areas (Zaas River valley (Switzerland) in 1987, valley of the Ishkoman River left tributary (Pakistan) in 2018). Volumes of debris flow material carried out from moraine pedestals reach 1–5 million m3. In 2015 part of the Barsem village territory became covered with debris flow deposits and a dam was formed on the Gunt River above which is the Barsemkul dammed lake now. Places of possible debris flows such as Barsem disasters can be determined on the basis of glacial accumulation form analysis and identification of moraine pedestals in which the debris flow incisions are not yet developed.

Chapter 5 Debris flows

2020 ◽  
Vol 29 (1) ◽  
pp. 163-185 ◽  
Author(s):  
M. G. Winter
Keyword(s):  
Debris Flow ◽  
Fast Moving ◽  
Debris Flows ◽  
Educational Opportunities ◽  
Mountainous Areas ◽  
Remote Communities ◽  
Strategic Approach ◽  
Hazard And Risk ◽  
The Uk ◽  
Debris Flow Hazard

AbstractFast-moving, rainfall-induced debris-flow events are relatively common in the mountainous areas of the UK. Their impacts are largely, although by no means exclusively, economic and social. They often sever (or delay) access to and from relatively remote communities for services and markets for goods; employment, health and educational opportunities; and social activities. Specific forms of economic impact are described and their extent is defined by the vulnerability shadow. The mechanisms of rainfall-induced, fast-moving debris flows are considered to bridge between slow mass movements and flood phenomena. The occurrence of debris flows is largely restricted to mountainous areas and a series of case studies from Scotland is briefly described. Hazard and risk assessment are briefly considered and a strategic approach to risk reduction is described. The latter allows a clear focus on that overall goal before concentrating on the desired outcomes and the generic approach to achieving those outcomes. The effects of climate change on debris-flow hazard and risk are also considered and it is concluded that, in Scotland, increases in debris-flow frequency and/or magnitude are most likely and that increases in the risks associated with debris flows are also likely.

scholarly journals Assessment and Analysis of a Rainfall–Time-Lagging Water-Related Disaster in Mountainous Areas

2021 ◽  
Vol 9 ◽  
Author(s):  
Xu-Feng Yan ◽  
Hui Xu ◽  
Heng Lu ◽  
Jia-Wen Zhou ◽  
Xie-Kang Wang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Global Climate ◽  
Integrated Analysis ◽  
Small Scale ◽  
Mountainous Areas ◽  
Triggering Mechanism ◽  
Water Release ◽  
Field Evidence

Both global climate change and human activities are continuously impacting the abruptness and frequency of water-related natural disasters such as flash floods, debris flows, and landslides in mountainous areas, greatly threatening the safety of lives and properties. A recent rainfall-induced debris flow event happened on July 6, 2020 in the Chenghuangmiao Gully, in Sichuan Province, China, resulting in severe damage to buildings at the outlet. An integrated analysis of the consequence and triggering mechanism of this debris flow event was conducted with hydrologic information, topographic details, vegetation regimes, and drone aerial imagery. The result shows that the entire runout of the debris flow differs from that of common ones (debris flow and rainfall were highly related and synchronized), which happened 4 h after the stop of the rainfall. The hysteretic feature increases the difficulty of the prediction and warning of the debris flow due to lack of a responsible triggering mechanism. The hillslope surface is well covered by vegetation, hindering regular observation and cleaning up of long-term deposited wood and sediment debris. This effect increases the crypticity and abruptness of potential debris flows. With field evidence and analysis, it is speculated that long-term accumulative processes of dead wood sand sediment deposition formed a small-scale debris dam, and the continuous water release from the watershed led to dam breaching, subsequently triggering the initiation of the debris flow. Multiple steps distributing along the gully of an average slope of 15.65° contributed to the amplification of the debris flow once the breach of the upstream wood and sediment dam occurred. Along the gully, small-scale landslide scars can be observed, possibly amplifying the scale of the debris flow and disaster impact. This debris event gives a lesson of necessary demands of predicting and managing the risks of a low-frequency debris flow non-synchronized with rainfall events.

scholarly journals Effects of <i>Y</i>-type spillway lateral contraction ratios on debris-flowpatterns and scour features downriver of a check dam

2016 ◽  
Vol 16 (11) ◽  
pp. 2433-2442 ◽  
Author(s):  
Huayong Chen ◽  
Jinfeng Liu ◽  
Wanyu Zhao
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Scour Depth ◽  
Check Dam ◽  
Mountainous Areas ◽  
Dimensionless Analysis ◽  
Lateral Contraction ◽  
Contraction Ratio ◽  
New Type ◽  
Good Agreement

Abstract. Debris flows often cause devastating damage to property and can injure or kill residents in mountainous areas. The construction of check dams in debris-flow valleys is considered a useful strategy for mitigating the damages downstream. In this paper, a new type of spillway structure with lateral contraction was proposed to distribute debris flows after the check dam storage filled up. Four different lateral contraction ratios of the spillway were considered in experiments that investigated debris-flow patterns, scour characteristics, and energy dissipation rates when debris flows passed through the spillway. The results indicated that lateral contraction considerably influenced the extension of debris-flow nappes. The drop length of the nappe at η  =  0.7 (η means lateral contraction ratio) was approximately 1.4 times larger than at η  =  0.4. The collision, friction, and mixing forces between the debris-flow nappes and debris flows in downstream plunge pools dissipated much of the debris-flow kinetic energy, ranging from 42.03 to 78.08 % at different contraction ratios. Additionally, based on a dimensionless analysis, an empirical model was proposed to predict the maximum scour depth downriver of a check dam. It indicated that the results calculated by the model exhibited good agreement with the experimental results.

Development of slope-type debris flows regarding frequencies and magnitudes based on aerial images since 1947 in Horlachtal, Austria

2021 ◽  
Author(s):  
Jakob Rom ◽  
Florian Haas ◽  
Tobias Heckmann ◽  
Moritz Altmann ◽  
Fabian Fleischer ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Data Availability ◽  
Aerial Images ◽  
Flow Process ◽  
Small Catchment ◽  
Highly Active ◽  
Time Period ◽  
Flow Processes ◽  
The Subject

&lt;p&gt;The future development of debris flow processes regarding frequency and magnitude in terms of climate change is currently the subject of intensive research. One reason for this is that datasets that extend over decades are often incomplete and biased towards high magnitude events based on the poor data availability in text records, for example.&lt;/p&gt;&lt;p&gt;Within this study, we investigate the development of slope-type debris flows in Horlachtal, a small catchment (~ 55 km&amp;#178;) within the Stubai Alps, Austria. Here, aerial images are available from 2018 back to 1947, which enables the creation of orthoimages. These allow a detailed mapping of debris flow processes even with smaller magnitudes. The resulting large dataset of debris flow process zones from 1947 to 2018 (10 time steps) can give some hints about the development of the frequencies of slope-type debris flows for the last 71 years. Due to their high spatial resolution and accuracy, two LiDAR datasets from 2006 and 2017 were used to calculate the volumes of debris flow deposits and thus the magnitude of debris flows within this time. Using a volume-area relationship on the base of the LiDAR data, we are able to estimate the volumes of debris flow deposits even for the older time steps, which can give an idea of changes in the magnitude of debris flow deposits for the last 71 years.&lt;/p&gt;&lt;p&gt;The results show a highly active time period between 1990 and 2010 as well as a high number of debris flows between 1953 and 1974. An increasing trend in numbers per year and volume per year is recognizable, but some uncertainties remain due to mapping issues, which include resolution of aerial images, shadow effects, snow cover etc.&lt;/p&gt;

scholarly journals Rainfall threshold calculation for debris flow early warning in areas with scarcity of data

2018 ◽  
Vol 18 (5) ◽  
pp. 1395-1409 ◽  
Author(s):  
Hua-Li Pan ◽  
Yuan-Jun Jiang ◽  
Jun Wang ◽  
Guo-Qiang Ou
Keyword(s):  
Debris Flow ◽  
Wenchuan Earthquake ◽  
Early Warning ◽  
Debris Flows ◽  
Early Warning Systems ◽  
Rainfall Threshold ◽  
Warning Systems ◽  
Mountainous Areas ◽  
Rainfall Thresholds ◽  
Initiation Mechanism

Abstract. Debris flows are natural disasters that frequently occur in mountainous areas, usually accompanied by serious loss of lives and properties. One of the most commonly used approaches to mitigate the risk associated with debris flows is the implementation of early warning systems based on well-calibrated rainfall thresholds. However, many mountainous areas have little data regarding rainfall and hazards, especially in debris-flow-forming regions. Therefore, the traditional statistical analysis method that determines the empirical relationship between rainstorms and debris flow events cannot be effectively used to calculate reliable rainfall thresholds in these areas. After the severe Wenchuan earthquake, there were plenty of deposits deposited in the gullies, which resulted in several debris flow events. The triggering rainfall threshold has decreased obviously. To get a reliable and accurate rainfall threshold and improve the accuracy of debris flow early warning, this paper developed a quantitative method, which is suitable for debris flow triggering mechanisms in meizoseismal areas, to identify rainfall threshold for debris flow early warning in areas with a scarcity of data based on the initiation mechanism of hydraulic-driven debris flow. First, we studied the characteristics of the study area, including meteorology, hydrology, topography and physical characteristics of the loose solid materials. Then, the rainfall threshold was calculated by the initiation mechanism of the hydraulic debris flow. The comparison with other models and with alternate configurations demonstrates that the proposed rainfall threshold curve is a function of the antecedent precipitation index (API) and 1 h rainfall. To test the proposed method, we selected the Guojuanyan gully, a typical debris flow valley that during the 2008–2013 period experienced several debris flow events, located in the meizoseismal areas of the Wenchuan earthquake, as a case study. The comparison with other threshold models and configurations shows that the selected approach is the most promising starting point for further studies on debris flow early warning systems in areas with a scarcity of data.

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