scholarly journals Dimensionless Assessment Method of Landslide Dam Formation Caused by Tributary Debris Flow Events

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Kun-Ting Chen ◽  
Xiao-Qing Chen ◽  
Gui-Sheng Hu ◽  
Yu-Shu Kuo ◽  
Yan-Rong Huang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Water Depth ◽  
Debris Flows ◽  
Landslide Dam ◽  
Assessment Method ◽  
Main Stream ◽  
Deposition Thickness ◽  
The Relationship ◽  
Prepared Response

In this study, we develop a dimensionless assessment method to evaluate landslide dam formation by considering the relationship between the run-out distance of a tributary debris flow and the width of the main stream, deposition thickness of the tributary debris flow, and the water depth of the main stream. Based on the theory of debris flow run-out distance and fan formation, landslide dam formation may result from a tributary debris flow as a result of two concurrent formation processes: (1) the run-out distance of the tributary debris flow must be greater than the width of the main stream, and (2) the minimum deposition thickness of the tributary debris flow must be higher than the in situ water depth of the main stream. At the confluence, one of four types of depositional scenarios may result: (1) the tributary debris flow enters into the main stream and forms a landslide dam; (2) the tributary debris flow enters into the main stream but overflow occurs, thus preventing complete blockage of the main stream; (3) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment remains partially above the water elevation of the main stream; or (4) the tributary debris flow enters into the main stream, does not reach the far bank, and sediment is fully submerged in the main stream. This method was applied to the analysis of 11 tributary debris flow events during Typhoon Morakot, and the results indicate that the dimensionless assessment method can be used to estimate potential areas of landslide dam formation caused by tributary debris flows. Based on this method, government authorities can determine potential areas of landslide dam formation caused by debris flows and mitigate possible disasters accordingly through a properly prepared response plan, especially for early identification.

scholarly journals An Assessment Method for Debris Flow Dam Formation in Taiwan

2018 ◽  
Vol 22 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Kun-Ting Chen ◽  
Chia-Hsing Lin ◽  
Xiao-Qing Chen ◽  
Gui-Sheng Hu ◽  
Xiao-Jun Guo ◽  
...  
Keyword(s):  
Debris Flow ◽  
Water Depth ◽  
Debris Flows ◽  
Assessment Method ◽  
Property Damage ◽  
Dam Failures ◽  
Downstream Area ◽  
Large Floods

Debris flows in tributaries rush into and block the main branches of rivers and often result in serious hazards. Dam failures cause large floods in the downstream area and can lead to fatalities and property damage. This study proposes an assessment method to evaluate the formation of a debris flow dam, which includes two conditions: (1) the sediment transported by the debris flow must reach across the river; and (2) the thickness of the deposit by the debris flow must be higher than the in situ water depth. This methodology was used to study the case of a debris flow dam caused by debris flow across the Er River in Taiwan, which blocked the Chishan River and led to the formation of the Namasha debris flow dam. This methodology can also be applied to identify the formation of debris flow dams.

scholarly journals Propagation Characteristics of Debris Flows Considering Entrainment Effect

2018 ◽  
Vol 7 (3.34) ◽  
pp. 122
Author(s):  
Seokil Jeong ◽  
Junseon Lee ◽  
Chang Geun Song ◽  
Seung Oh Lee
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Behavior ◽  
Prediction Method ◽  
Heavy Rain ◽  
Accurate Analysis ◽  
Propagation Length ◽  
2D Simulation ◽  
Entrainment Effect ◽  
The Relationship

Background/Objectives: Due to the extreme climate and the localized heavy rain, the frequency of debris flow has been increasing. Therefore, there is a growing expectation for accurate numerical analysis.Methods/Statistical analysis: We present a prediction method that can calculate the propagation length of the debris flow. This analysis indicates the relationship between the potential energy and the propagation length of the debris flow. To study the behavior of the debris flow accurately, the change in the momentum force must be considered; otherwise the calculation accuracy of the debris flow behavior is inevitably low.Findings: Entrainment is a common behavior in a debris flow that leads to changes in the momentum force. Here, we analyzed the change in the momentum force using a 2D simulation model that included entrainment. The results show how the debris flow behaves with changes in the momentum force. When entrainment is considered, the propagation length tends to be underestimated. With detailed information, the uncertainty in the prediction accuracy can be reduced.Improvements/Applications: If studies on the material properties of debris flow would be added, it will be possible to carry out various and accurate analysis of the debris flow  

scholarly journals The importance of erosion for debris flow runout modelling from applications to the Swiss Alps

2015 ◽  
Vol 3 (4) ◽  
pp. 2379-2417 ◽  
Author(s):  
F. Frank ◽  
B. W. McArdell ◽  
C. Huggel ◽  
A. Vieli
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Data ◽  
Hazard Analysis ◽  
Maximum Shear Stress ◽  
Swiss Alps ◽  
Erosion Model ◽  
Practical Applications ◽  
Bed Erosion ◽  
The Relationship

Abstract. This study describes an investigation of channel-bed erosion of sediment by debris flows. An erosion model, developed using field data from debris flows at the Illgraben catchment, Switzerland, was incorporated into the existing RAMMS debris-flow model, which solves the 2-D shallow-water equations for granular flows. In the erosion model, the relationship between maximum shear stress and measured erosion is used to determine the maximum potential erosion depth. Additionally, the maximum rate of erosion, measured at the same field site, is used to constrain the erosion rate. The model predicts plausible erosion values in comparison with field data from highly erosive debris flow events at the Spreitgraben torrent channel, Switzerland in 2010, without any adjustment to the coefficients in the erosion model. We find that by including channel erosion in runout models a more realistic flow pattern is produced than in simulations where entrainment is not included. In detail, simulations without channel bed erosion show more lateral outflow from the channel where it has not been observed in the field. Therefore the erosion model may be especially useful for practical applications such as hazard analysis and mapping, as well as scientific case studies of erosive debris flows.

scholarly journals Measurements of Velocity Profiles in Natural Debris Flows: A View behind the Muddy Curtain

2020 ◽  
Vol 27 (1) ◽  
pp. 87-94
Author(s):  
Georg Nagl ◽  
Johannes Hübl ◽  
Roland Kaitna
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Model Development ◽  
Fluid Pressure ◽  
Velocity Profiles ◽  
Flow Parameters ◽  
Internal Deformation ◽  
Debris Flow Hazard ◽  
Real Scale

ABSTRACT The internal deformation behavior of natural debris flows is of interest for model development and model testing for debris-flow hazard mitigation. Up to now, only a few attempts have been made to measure velocity profiles in natural debris flows due to the low predictability and high destructive power of these flows. In this contribution, we present recent advances to measure in-situ velocity profiles together with flow parameters like flow height, basal normal stress, and pore fluid pressure. This was accomplished by constructing a fin-shaped monitoring barrier with an array of paired conductivity sensors in the middle of Gadria Creek, Italy. We present results from two natural debris-flow events. Compared to the first event on July 10, 2017, the second event on August 19, 2017, was visually more liquid. Both debris flows exhibited significant longitudinal changes of flow properties like flow height and density. The liquefaction ratios reached values up to unity in some sections of the flows. Velocity profiles for the July event were mostly concave-up, while the profiles for the more liquid event in August were linear to convex. These measurements provide new insights into the dynamics of real-scale debris flows.

Feasibility of Using Sentinel-3 in Estimating Lake Nasser Water Depths

2021 ◽  
Author(s):  
Marwa Khairy ◽  
Hickmat Hossen ◽  
Mohamed Elsahabi ◽  
Shenouda Ghaly ◽  
Andrea Scozzari ◽  
...  
Keyword(s):  
Water Level ◽  
Water Depth ◽  
Water Body ◽  
Optical Data ◽  
Inland Water ◽  
Depth Data ◽  
Nasser Lake ◽  
Inland Water Body ◽  
The Relationship

<p><strong>Abstract</strong>  After the construction of the Grand Ethiopian Renaissance Dam (GERD), Nasser Lake (NL)became one of the most challenging hot spots at both local and global level. It is one of the biggest manmade reservoirs in the world and the most important in Egypt. It is created  in the southern part of the Nile River in Upper Egypt after the construction of Aswan High Dam (AHD). The water level in NL might fluctuate between 160 to 182 m above the mean sea level. Monitoring NL  water depth is an expensive and time-consuming activity. This work investigates the possibility to use information from the Sentinel missions to estimate the depth of NL as an inland water body, in the frame of estimating storage variations from satellite measurements. In this preliminary study, we investigated the relationship between the radiance /reflectance of optical imagery from two instruments SLSTR and OLCI instruments hosted by the Sentinel-3A platform and in situ water depth data using the Lyzenga equation. The results  indictaed  that there was a reasonable correlation between Sentinel-3 optical data and in situ water depth data. Also, Heron's formula was used to estimate water storage variations of NL with limited in situ data. In addition, equations governing the relationship between water level and both surface area and water volume were worked out. This study is in the framework of a bilateral project between ASRT of Egypt and CNR of Italy which is still running.</p><p> </p><p><strong>Keywords</strong>: Sentinel, SLSTR, OLCI, Inland water body, Nasser Lake, Egypt, Water Depth, GERD, AHD, Egypt</p>

scholarly journals Experimental study on the rheological behaviour of debris flow

2010 ◽  
Vol 10 (12) ◽  
pp. 2507-2514 ◽  
Author(s):  
A. Scotto di Santolo ◽  
A. M. Pellegrino ◽  
A. Evangelista
Keyword(s):  
Debris Flow ◽  
Yield Stress ◽  
Debris Flows ◽  
Soil Mechanics ◽  
Rheological Behaviour ◽  
Simple Relation ◽  
Campania Region ◽  
Failure Behaviour ◽  
Fluid Behaviour

Abstract. A model able to describe all the processes involved in a debris flow can be very complex owing to the sudden changing of the material that turns from solid into liquid state. The two phases of the phenomenon are analysed separately referring to soil mechanics procedures with regard to the trigger phase, and to an equivalent fluid for the post-failure phase. The present paper is devoted to show the experimental results carried out to evaluate the behaviour assumed by a pyroclastic-derived soil during the flow. A traditional fluid tool has been utilized: a standard rotational rheometer equipped with two different geometries. The soils tested belong to deposits that cover the slopes of the Campania region, Italy, often affected by debris flows. The influence of solid concentration Cv and grain size distribution was tested: the soils were destructurated, sieved and mixed with water starting from the in situ porosity. All material mixtures showed a non-Newtonian fluid behaviour with a yield stress τy that increases with a solid volumetric concentration and decreases for an increase of sand fraction. The experimental data were fitted with standard model for fluids. A simple relation between Cv and τy was obtained. The yield stress seems to be a key parameter for describing and predicting the post-failure behaviour of debris flows. These results suggest that in the field a small change in solid fraction, due to rainfall, will cause a slight decrease of the static yield stress, readily inducing a rapid flow which will stop only when the dynamic yield stress is reached, namely on a much smoother slope. This can explain the in situ observed post-failure behaviour of debris flows, which are able to flow over very long distances even on smooth slopes.

scholarly journals Testing seismic amplitude source location for fast debris-flow detection at Illgraben, Switzerland

2017 ◽  
Vol 17 (6) ◽  
pp. 939-955 ◽  
Author(s):  
Fabian Walter ◽  
Arnaud Burtin ◽  
Brian W. McArdell ◽  
Niels Hovius ◽  
Bianca Weder ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Seismic Velocity ◽  
Data Communication ◽  
Ground Vibration ◽  
Source Location ◽  
Detection Methods ◽  
Processing Scheme ◽  
Seismic Amplitude

Abstract. Heavy precipitation can mobilize tens to hundreds of thousands of cubic meters of sediment in steep Alpine torrents in a short time. The resulting debris flows (mixtures of water, sediment and boulders) move downstream with velocities of several meters per second and have a high destruction potential. Warning protocols for affected communities rely on raising awareness about the debris-flow threat, precipitation monitoring and rapid detection methods. The latter, in particular, is a challenge because debris-flow-prone torrents have their catchments in steep and inaccessible terrain, where instrumentation is difficult to install and maintain. Here we test amplitude source location (ASL) as a processing scheme for seismic network data for early warning purposes. We use debris-flow and noise seismograms from the Illgraben catchment, Switzerland, a torrent system which produces several debris-flow events per year. Automatic in situ detection is currently based on geophones mounted on concrete check dams and radar stage sensors suspended above the channel. The ASL approach has the advantage that it uses seismometers, which can be installed at more accessible locations where a stable connection to mobile phone networks is available for data communication. Our ASL processing uses time-averaged ground vibration amplitudes to estimate the location of the debris-flow front. Applied to continuous data streams, inversion of the seismic amplitude decay throughout the network is robust and efficient, requires no manual identification of seismic phase arrivals and eliminates the need for a local seismic velocity model. We apply the ASL technique to a small debris-flow event on 19 July 2011, which was captured with a temporary seismic monitoring network. The processing rapidly detects the debris-flow event half an hour before arrival at the outlet of the torrent and several minutes before detection by the in situ alarm system. An analysis of continuous seismic records furthermore indicates that detectability of Illgraben debris flows of this size is unaffected by changing environmental and anthropogenic seismic noise and that false detections can be greatly reduced with simple processing steps.

Risk Assessment and Control Measure of Debris Flow in Chunyashu Gully of Seismic Disastrous Area of Sichuan Province

2012 ◽  
Vol 446-449 ◽  
pp. 2988-2991
Author(s):  
Ji Hua Chen ◽  
Hui Ge Wu ◽  
Hai Hui Zhou ◽  
Hai Liang Zhang
Keyword(s):  
Risk Assessment ◽  
Debris Flow ◽  
Wenchuan Earthquake ◽  
Debris Flows ◽  
Loose Material ◽  
Control Measure ◽  
Assessment Method ◽  
Sichuan Province ◽  
The Wenchuan Earthquake ◽  
And Control

The terrain of Chunyashu gully in Dujiangyan city of Sichuan province was steep, plenty of loose material increased after the Wenchuan earthquake. Debris flows were triggered in September 2008 and August 2009, and the debris flow was a serious threat to the highway and the residents. Risk of Chunyashu gully debris flow had been analyzed by the latest assessment method, and the result was that the risk degree of this gully was middle. Finally according to the local situation the control measure of interception dam and other advices had been suggested to protect the safety of the residents.

scholarly journals Risk Assessment of Population Loss Posed by Earthquake-Landslide-Debris Flow Disaster Chain: A Case Study in Wenchuan, China

2021 ◽  
Vol 10 (6) ◽  
pp. 363
Author(s):  
Xiang Han ◽  
Yunhe Yin ◽  
Yuming Wu ◽  
Shaohong Wu
Keyword(s):  
Risk Assessment ◽  
Debris Flow ◽  
Debris Flows ◽  
Assessment Method ◽  
Earthquake Intensity ◽  
Population Loss ◽  
Risk Assessment Method ◽  
Disaster Chain ◽  
Debris Flow Disaster ◽  
Landslide Debris

Earthquakes often cause secondary disasters in mountainous areas, forming the typical earthquake-landslide-debris flow disaster chain for a long time that results in a series of losses. It is important to improve the risk assessment method from the perspective of cascading effect of such a disaster chain, by strengthening quantitative research on hazards of the debris flows which are affected by landslide volume and rainstorm intensity. Taking Wenchuan County as an example, the risk assessment method for population loss of the disaster chain is established and the risks are evaluated in this paper. The results show that the population loss risk is 2.59–2.71 people/km2 under the scenarios of the Wenchuan Ms8.0 earthquake and four rainstorm intensities. The impacts of landslide and debris flow after the earthquake were long-term and profound. A comparison of risks caused by each element of the chain revealed that the risk associated with the earthquake accounted for the highest proportion, and landslide and debris flow accounted for 38.82–37.18% and 3.42–7.50%, respectively. As the earthquake intensity increases, the total risk posed by the disaster chain increases significantly. The risk caused by the earthquake is the highest in high earthquake intensity zones; while in the lower-intensity zones, landslides and debris flows pose relatively high risks. The risk assessment results were verified through comparison with actual data, indicating that the simulation results are quite consistent with the existing disaster information and that the risk assessment method based on the earthquake-landslide-debris flow cascade process is significant for future risk estimation.

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