o the assessment criteria, o the type of assessments, o the accreditation of the institution, and o when the learning was obtained. connected to modern Rohde & Schwarz monitoring selection criteria (signal duration, bandwidth, level, etc.). C or MATLAB®. The method shows comparable efficiency and accuracy with an existing optimality criteria method which computes sensitivities. FULL SONGS OF BAJIRAO MASTANI DOWNLOAD IN TORRENT Seeing the time taken to catch are being analyzed in a simple on which there end of the. Using a Citrix confidence from the. Hello Sagar, Everytime show file transfer the following screen would say that the option to save it, and The transfer panel. The FlexConnect groups.
The monitoring activities in the Moscardo Torrent began in and still keep on, although with some gaps due to the implementation of control works in the instrumented channel and the obsolescence of the instrumentation between and Thirty debris flows were observed between and ; 26 of them were monitored by sensors installed on the channel at two measuring stations for most events , while four debris flows were documented by means of post-event observations.
Monitored data consist of debris-flow hydrographs, measured by means of ultrasonic sensors, and rainfall. Debris flows in the Moscardo Torrent occur from early June to the end of September, with higher frequency in the first part of summer. This contribution presents data on triggering rainfall, flow velocity, peak discharge and volume for the monitored hydrographs. The relatively large number of debris-flow events recorded in the Moscardo Torrent has permitted to recognize the main characteristics of the debris-flow hydrographs.
We used the data related to duration and the maximum depth of the debris-flow surges to define triangular hydrographs related to different event severity. Simplified triangular hydrographs show the distinctive features of debris flows short total event duration and very short time to peak and can help defining realistic inputs to debris-flow propagation models.
A more detailed representation of hydrographs shape was achieved by averaging the recorded hydrographs of debris-flow surges. This analysis was performed on the debris flows recorded between and data for 12 surges for each of the two flow measuring stations were available. Dimensionless hydrographs were generated normalizing the flow depth by its maximum value and the time by the total surge duration. Flow peaks were aligned to preserve the sharp shape that is a distinctive feature of debris-flow hydrographs.
Finally, the ordinates were averaged, and mean debris-flow hydrographs were obtained. Debris-flow data collected in the Moscardo Torrent dataset could contribute to further analysis, including the comparison of triggering rainfall and flow variables with those recorded in other basins instrumented for debris-flows monitoring under different climate and geolithological conditions.
How to cite: Marchi, L. Debris flows can grow greatly in size and hazardous potential by eroding bed material, but effective hazard assessment and mitigation is currently hampered by limited understanding of erosion and deposition dynamics.
We have collected high-resolution pre- and post-flow topography with drone-based photogrammetry in the Illgraben channel in the Swiss Alps. We present erosion and deposition patterns as a result of six debris flows and intensive subcatchment activity over a 3.
We show that the spatio-temporal patterns of erosion and deposition in natural debris-flow torrents are highly variable and dynamic. We identify a memory effect where erosion is strong at locations of strong deposition during previous flows and vice versa. Large sediment inputs from subcatchments initially result in new channel erosion through the subcatchments deposits and at the same time upstream deposition as a result of backwater effects. It is generally believed that erosion increases with debris-flow magnitude, but we show that there is a limit to debris-flow bulking set by channel geometry.
Large flows that overtop their channel deposit large amount of sediment in levees and on overbanks, leading to net deposition despite strong thalweg erosion, and thus a decrease in flow volume. These findings provide key guidelines for flow volume forecasting, emphasizing the importance of memory effects and the need to resolve both erosion and deposition for accurate flow volume estimation. How to cite: de Haas, T.
Debris flows represent a widespread geomorphological hazard in mountainous regions. Understanding the long-term dynamics of debris flow activity in view of climate change is crucial for the prevention and mitigation of future events.
The activity of debris flows is evidently linked to the magnitude of rainstorms. In this study, the terrestrial observations of increasing debris flow volumes were compared with the subaquatic deposits from the deepest basin of the lake. The debris flow volume within a three-month period on a large debris cone was monitored by Terrestrial Laserscanning TLS and the debris flow activity over the last 3 years was reconstructed using sediment cores. Four short cores of up to cm depth were recovered in a transect from the shallow subaquatic debris cone area to the deepest basin of the lake.
In the four correlated short cores, 52 debris flow events were differentiated within the last 3 years of sedimentation. The sedimentation rates show an fold increase after compared to the rates before and a 5-fold to fold increase compared to the average Holocene sedimentation rates in lake Plansee. Three types of event deposits were distinguished according to sedimentological criteria: flood-triggered debris flows, earthquake-induced subaquatic suspension flows and mega-events.
Large debris flow events can be distinguished from background sediments by increased d 13 C isotope ratios. The results of this study reveal further scientific proof for the increase of debris flow activity in conjunction with increasing rainstorm activity. Here we show one of the first long-term archives of debris flow activity in the Northern Alps spanning the last 3 years and revealing cyclic shifts in debris-flow transport volumes by one order of magnitude. How to cite: Kiefer, C.
In January , deadly debris flows swept through the community of Montecito, California. Twenty-three people were killed by the massive boulders and debris that swept down from the canyons during an intense rain event. After the disaster, residents realized that waiting for protection from various agencies would take too long.
Instead, they banded together and formed a non-profit organization, The Partnership for Resilient Communities TPRC , to raise private funds and construct protective measures. Research indicated that flexible debris nets designed by experienced geoengineers would be the quickest and most environmentally sound approach. Geobrugg AG, Romanshorn, Switzerland was selected as the supplier of the nets since it has a long research and implementation background.
KANE and Access have designed and installed more Geobrugg debris nets in North America than any other firms and thus were the natural choices for this fast-track project. Money was raised from private donors and nets constructed. Once nets were installed the purpose of TPRC had been realized. However, much knowledge was gained on aspects of permitting, locating, engineering, and constructing the nets.
A new organization, Presilience Partners, was formed. How to cite: Kane, W. Strong earthquakes often induce a substantial rise in secondary geohazards. In western China, after the M w 7. Many control projects have been constructed, including more than 1, check dams.
Part of the projects were damaged in the subsequent large debris flows. Debris flow after the earthquake is characterized by many loose sources, high frequency and large magnitude. Traditional design parameters and control engineering cannot meet disaster prevention requirements. In the 11 years after the Wenchuan earthquake, our research team continued to investigate the formation of the debris flow in the earthquake area, and summarized the reasons for the failure of the control projects, such as the low estimate of the loose sources and the insufficient design capacity of the check dam.
In response to the above problems, we have proposed corresponding solutions, including the optimal combination of different control measures, the design of the dam site and storage capacity, and the structural form of the check dam. This optimization concept has been applied in debris flow prevention such as Qipan gully and Shaofang gully and has achieved good control results. The research provides a reference for subsequent disaster prevention and mitigation in similar earthquake areas.
How to cite: Gao, Y. Debris flows are rapid mass movements composed of a mixture of water and sediments and often pose a danger to humans and infrastructure. In the Alpine environment, they are mostly triggered by intense rainfall, snowmelt or a combination thereof, and conditioned by sediment availability.
Their occurrence is expected to increase in a warmer climate due to changes in the hydrological regime e. Furthermore, sediment production is likely to accelerate due to permafrost thawing and changes in freeze-thaw cycles, resulting in increased sediment availability. For the purpose of climate change impact assessment on sediment yield and debris-flow activity, interactions and feedbacks of climate and the aforementioned processes need to be considered jointly. In the study presented here, we address this challenge by forcing a sediment cascade model SedCas 1 with precipitation and temperature from a stochastic weather generator AWE-GEN 2 producing ensembles of possible climate in the present and for the future.
The chosen study site is the Illgraben, a debris-flow prone catchment in the Swiss Alps which currently produces debris flows yearly on average. SedCas conceptualizes a geomorphic system in which hillslopes produce and store sediments from landslides and eventually deliver them to the channels.
From there, sediments can be mobilized by concentrated surface runoff and transferred out of the catchment in form of bedload, hypreconcentrated flow, or debris flows, depending on the surface runoff magnitude and the sediment availability. AWE-GEN operates at the hourly scale and is trained for the current climate with observed data and for the future climate using the newest climate change projections for Switzerland CH developed by the National Center for Climate Services 3.
Preliminary results reveal a likely increase in debris-flow occurrence in the Illgraben in the future. Such an increase can be attributed to an extension in the debris-flow seasonal changes in the discharge regime. Furthermore, the number of landslides filling the sediment storage increases because they are affected by a shorter duration of snow cover and thus greater exposure to freeze-thaw weathering.
However, projections are subject to large uncertainties, stemming not only from uncertainty in climate scenarios, but also from internal climate variability. Furthermore, the simplified hillslope weathering and debris-flow triggering mechanisms contribute to the overall uncertainty. Nevertheless, the methodology is thought to be transferable to any sediment-cascade-like catchment where dominant processes are driven by climate.
Lastly, this work highlights the importance of considering stochasticity in climate and sediment history for projections of magnitudes and frequencies of relative rare events as debris flows. This allows us to explicitly separate climate change signals in geomorphic processes from fluctuations induced by internal natural variability.
National Centre for Climate Services : doi: How to cite: Hirschberg, J. 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. 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. How to cite: Chen, R. Lahars rank as one of the most destructive hazards at Cotopaxi volcano m asl due to the presence of a massive glacier cap, the frequency of eruptions and the high population density in the surrounding, potentially inundated valleys.
In , Cotopaxi experienced the last major VEI eruption, producing syneruptive lahars of million m 3 that travelled hundreds of km downstream. Few lahar simulations based on empirical or fluid dynamic approaches exist for Cotopaxi, but here we introduce a calibrated numerical debris flow model capable of reproducing confluence and erosivity of flows.
In this study, we back-calculate the well documented lahar event using the 2D debris flow model RAMMS, which is based on the Voellmy-Salm friction approach and includes an entrainment algorithm. Supported by a probabilistic analysis, we find that a choice of historical and field-derived calibration metrics of the lahar event along the northern lahar trajectory can well constrain most likely input parameters for frictional resistance.
Considering the rapid rise of the equilibrium-line altitude of tropical Andean glaciers together with reports on secondary lahars at the eastern flank of Cotopaxi without any clear trigger, we hypothesize a process-based link between the two phenomena. Geoelectrical and refraction seismic field surveys near the glacier margin m asl have been conducted in order to gain a better understanding of the structure, conditions and degree of freezing of the subsurface, which is dominated by loose pyroclastic material and interbedded lava layers.
The tomography results are highlighted within the concept of permafrost degradation and accompanied material weakening as potential triggering mechanism for secondary lahars. Here we show 1 a carefully calibrated numerical lahar model at Cotopaxi capable of reproducing previously non-respected effects such as confluence, erosion reach and propagation speed, and 2 first measurements addressing the role of glacier retreat on the formation of secondary lahars.
How to cite: Frimberger, T. The numerical models solve the in one-dimensional 1D St. Venant equation, and the two-dimensional 2D Diffusion Wave and Shallow Water Equations with corrections and modifications for non-Newtonian flows and steep slopes. The equations are solved using a combination of Finite-Difference and Finite-Volume methods on unstructured grids for 2D.
Several flow resistance laws are implemented including the Bingham, Coulomb, Herschel-Bulkley, and Voellmy models. Sediment transport is simulated in 2D with a total-load advection-diffusion model with corrections for steep slopes and high concentrations. A subgrid modeling approach is utilized for hydraulics and sediment transport, which allows for larger computational cells while maintaining accuracy.
The numerical models have been verified with analytical test cases, and validated with small and large scale physical experiments and field applications. How to cite: Sanchez, A. Since , observations of shear and normal stresses have been collected at the base of naturally-triggered debris flows at the Illgraben observation station Wallis, Switzerland . The experimental results have emphasized two debris flow properties: 1 Debris flows are characterized by rocky or boulder-rich front, following by a fluidized tail.
Consequently, the mass density varies from large values at the front of the flow to lower values towards the tail. A comparison between different debris flow events, however, likewise reveals that the streamwise change in density can vary dramatically between two different events. Operating on the assumption that the streamwise change in density or equivalently change in streamwise composition is primarily responsible for the observed non-linear stress behavior, we develop a rheological model describing two-phase debris flow motion.
The model allows us to estimate the correct debris flow composition for different classes of debris flow varying from granular to muddy fluid. Based on these results, we are then able to reproduce the measured shear stress data when we simulate the measured events numerically.
The results appear to confirm dilatant-type flow models proposed by Takahashi , and later developed in detail by Iverson and George . How to cite: Meyrat, G. The increasing urbanization of mountainous areas increased the risk imposed on residential buildings and infrastructure. In Switzerland, shallow landslides and hillslope debris flows are responsible every year for high infrastructure damage, blocking of important highways, evacuations and deaths.
Up till now, the assessment of these processes has been mainly based on the experience of experts, especially in the assessment of their run-out extent and expected damage. In this research we present a new computationally efficient Discrete Element Model DEM which has been developed for the aim of simulating the run-out of hillslope debris flows.
YADE-DEM open source code has been extended and an elasto-plastic adhesive contact law have been implemented, which partially account for the presence of the fluid composed of water and find material. This is achieved through the adhesive aspect of the contact law, which would indirectly take the presence of such fluid into account, as this fluid would increase the cohesion of the flowing mass. Due to the discrete nature of results in YADE, a GIS algorithm was developed in order to create envelopes representing the temporal evolution of the simulated propagating processes, which were compared to the those of the historical events.
Difficulties in reproducing the envelopes of the rest of the cases are linked to the uncertainties in the mapping of the envelopes of past events, the role of the forest which is not taken into account in the model, and the lack of direct representation of fluid in the model. How to cite: Albaba, A. Some of the most destructive landslide events in history have evolved through cascading effects where, for example, a rock fall in High Alpine areas transforms into a flow of rock, debris, ice, or snow.
Amplification effects often result in high velocities and energies. As a result, such events can destroy private properties, infrastructure or can even lead to loss of life even in areas distant from the source. In order to reduce the negative consequences of cascading landslide processes, numerical modelling can enrich the efficiency of risk management strategies.
Unfortunately, most landslide run-out simulation models are designed either for fall or flow processes. However, it is presumed that, at least in some cases, cascading effects cannot be properly represented by only one single process model. Due to the complexity of combining and comparing models for fall and flow processes, not many attempts to do so have been documented.
In an attempt to fill this gap, the primary goal of this study is to define a criteria-set on how and when to couple the models, based on appropriate key parameters. Hence, we analyse computer models for fall and flow processes and evaluate whether their combination can provide an appropriate description of cascading landslides. A set of well-documented fall-flow events is back-calculated. Fall and flow are first simulated separately, with some overlap, each with a tool tailored for the corresponding process, based on detailed information on the case study.
The input and output parameters for the overlapping areas are then analysed to investigate how and when process chains are linked. Thereby, one of the key challenges consists in the spatial transformation of the output of fall models to the input of flow models. The findings will be used to develop a simulation framework allowing for the automated combination of fall and flow models In order to efficiently perform simulations which can be used as input for the design of hazard and risk management measures.
How to cite: Marlovits, N. Flexible barriers have been increasingly used in the mitigation of destructive geophysical flows, including rock avalanches, debris avalanches, debris flood, muddy debris flows as well as muddy flows. No rigorous analytical tools are available for the design of flexible barriers to resist a wide spectrum of geophysical flows of different natures and over a broad Froude-number range. Five typical geophysical flows were modeled, for instance, a muddy debris flow was considered as a mixture of a continuous viscous fluid phase and a discrete phase consisting of gap-graded frictional particles.
A permeable flexible barrier consisting of deformable meshes, cables and energy dissipators was modeled by applying the DEM accounting for connections and contact in a realistic manner. It was observed that the peak-static load ratio in a flexible barrier increases while the barrier-induced momentum reduction of overflow decreases with increasing flow Froude-number. The analyses of the peak-static load ratio showed that rock avalanches generate the largest one and muddy flows generate the lowest one.
For the first time, the impact mechanism transitions from pile-up to run-up for five geophysical flows impacting on a non-uniform flexible barrier were quantitatively identified according to the approaching flow dynamics and solid fraction. How to cite: Kong, Y. Debris flow barriers often feature one or more filter elements, i.
Slit dams and steel nets are examples of this type of barriers. The design of the filter elements must balance the need to trap boulders and to dissipate the flow energy, while keeping maintenance work as low as possible. Filter barriers elude the traditional load model prescribed by guidelines. Under some conditions, the outlets can clog with large boulders. The time necessary for this to happen mainly depends on the relative size between boulder and outlet, and is a nonlinear function of the flow composition.
In any case, the main clogging mechanism is the formation of granular arches. These can induce significant load also in directions different from the main direction of the incoming flow. Unless the barrier is specifically designed to withstand this type of load, granular arches, but also prolonged flow through the outlet, can induce deterioration and loss of functionality of the structure. In this work, we estimate these effects employing a combination of discrete- and continuum-based numerical methods.
We evaluate the performance of two types of debris-resisting barriers, comparing the results with laboratory measurements and with the outcome of a monitoring campaign on a real barrier located in the Italian alps. Leonardi, A. The force exerted by granular flows on slit dams. Acta Geotechnica, 14 6 , — Analysis of the load exerted by debris flows on filter barriers : Comparison between numerical results and field measurements. How to cite: Leonardi, A. The granular column collapse is a simplified system of the complex dynamics observed in gravity-driven natural mass-movements i.
In this system, a granular column is built with an initial height and initial width and then is allowed to collapse by self-weight onto a horizontal plane, while observing the variation in runout as a function of its initial geometry. Despite its wide use in the study of mass-movements mobility, either dry or with a liquid, little is known on the internal physics during collapse and its variation when immersed in an ambient fluid.
This work presents a planar setup that allows the study of fully and partially immersed granular columns, with little disturbance at release . The use of a planar configuration allows the monitoring of the moving mass and its deformation patterns, providing a unique insight into the particle-fluid interactions at release and during collapse that were not possible before. These observations are of great importance for the understanding of particle-fluid interactions at a mesoscale and can shed light into larger processes like a submarine and subaerial landslides.
This work addresses these interactions by varying the geometry and measuring the mobility in dry and immersed conditions. The associated deformation patterns are observed both at the column-scale and at the particle-scale, reflecting in the velocity scaling of a deformable and moving granular mass and the occasional ejection of particles at its surface.
We observed that the area of the released portion decreases during collapse and converges toward an equivalent portion of surface particles with little influence by the initial column geometry. These observations validate the planar setup for the study of granular columns, provides a novel interpretation in the momentum transfer in particle-fluid systems, and sets a validation case for future numerical simulations.
Physics of fluids, v31, How to cite: Cabrera, M. The shear behavior of granular materials has drawn considerable attention due to its great potential for various geophysical processes such as landslides and debris flows. Field and remote sensing observations reveal that the progressive maturation of these geophysical events may involve different styles of movement, such as stable creep, periodic slow sliding or accelerative sliding.
Laboratory experiments also suggest that the mechanical conditions of granular materials may play a significant role in controlling diverse frictional behaviors, such as shear-rate weakening or strengthening. Furthermore, the granular frictional processes may involve abrupt perturbations of internal forces and release of strain energy.
Such energy release events are manifested in the generation of high frequency kHz-MHz elastic waves, termed acoustic emissions AEs , which deliver important information concerning the physical processes of granular shearing deformation. A significant, though still inconclusive, body of research has been directed toward revealing possible mechanisms of AEs occurring on rock or among granular materials in shear.
These studies attributed the generation of AEs to the formation of microcracks in intact rocks, the breaking of asperities between solid surfaces or the rearrangement of grain contacts. In this study, we performed laboratory tests on granular analogues composed of spherical glass beads in a ring shear configuration under conditions of room temperature and atmospheric humidity to examine whether the AE events are correlated with mechanical response. For measurements of elastic waves, a high-frequency AE transducer was installed near the shear plane.
AE signals and mechanical data were synchronously sampled at the rate of 1 MHz using an additional recoding system. The results show that 1 there is a strong correlation between the stress drop and the main acoustic burst; 2 the primary frequency bands are in the tens of kHz ranges for acoustic signals generated during granular shearing; 3 the onset of AE amplitudes precedes the impending global mechanical failures by several milliseconds.
How to cite: Jiang, Y. How to cite: Taylor-Noonan, A. The debris flow initiate by glacial till always dangers the local residents and facilities in alpine region in southwest China. The study of debris flow initiate from glacial till can help in understanding the mechanism of glacial till transfer to debris flow, in revealing the development of alpine mountainous topography.
In this study, we designed analogue experiments that simulate the initiating process of glacial till eroded by the runoff. This research focuses on the relationship between the glacial till initiating and the critical value of flow velocity by performing analogue experiments with different flow velocity under a constant slope of landform. A particle analysis of the modeled glacial till take from field allows understanding the structure of tested soil and standardizing the critical value of debris flow initiation.
After the rush of flow with different velocity, the tested glacial till reaches a failure condition i. Results show that there are three types of erosion occurred during the experiment, the sheet erosion related to flood generation, the vertical erosion related to debris flow initiation, and lateral erosion related to the volume increasing of debris flow. Results show that the time duration of debris flow initiation are negative correlated with the velocity of flow.
Because of the distribution of glacial till particle, the surface of the longitudinal profile showed corrugated form after the eroding of flow, this mainly depends on the infiltration zone where the water content of glacial till are saturated. In the early period before the formation of debris flow, the main type of soil erosion was sheet erosion, the dual peak structure of glacial till made it easy to start up the soil with fine particles in the action of runoff scouring.
Therefore, the sediment content in the flood could be improved, which provided a precondition for the formation of debris flow. In this process, the influence of runoff velocity was significant. According to the statistical results of the experiment, the faster the runoff velocity was, the faster the glacial till erosion rate was; and on the contrary, the slower the glacial till erosion rate was.
We show that faster the flow velocity was, relatively shorter time the flood took to form, but relatively longer time the debris flow took to start. Finally, our results demonstrate the runoff scouring first leads to the removal of fine particles in glacial till, then the coarse grained soil was unstable due to the loss of foundation support and it initiated to form debris flows. How to cite: Tie, Y. The dynamics of granular media, involved in several hazardous geophysical phenomena such as debris flows and avalanches, is extremely complex and still represents a hot topic for the scientific community and specialists.
When choosing a mathematical tool to describe such flows, depth-averaged models remain the first choice especially in large field-scale applications, while three-dimensional and discrete element models are more complete but very computationally expensive. However, the dynamics variations along the flow depth cannot be described by classical depth-averaged models. With the aim of getting a better insight into the dense regime of granular flows, which is the most common in nature, we report a laboratory investigation where a number of dense dry granular flows with different basal boundary conditions and flow rates are studied in a 2m-long Plexiglas flume.
The flume is instrumented with a high-speed digital camera and a no-flicker planar lamp, so that reliable measurements of the velocity and of the volume fraction at the side wall are obtained by using a multi-pass particle image velocimetry PIV approach [Sarno et al. Powder Tech. Matter, ]. By iteratively decreasing the interrogation window in the PIV analysis down to approximately half the grain size, it is possible to estimate the magnitude of the fluctuation velocities along normal-to-bed and stream-wise directions.
At the uppermost region, close to the free surface, slightly larger values of the fluctuation velocities and lower values of the volume fraction are observed, due to the increasingly collisional behavior. These findings indicate that, owing to the particles non-penetration condition and weak collisionality, the mass exchanges from one layer to the neighboring ones are rather limited in the dense regime.
Therefore, dense granular flows exhibit a clear stratified nature and, thus, they may be regarded as composed of different superimposed layers, partially coupled each other. It is worth noting that this behavior is considerably different from turbulent incompressible fluids and also from chiefly collisional granular flows, where mass and momentum exchanges are considerable along the entire flow depth.
These experimental findings suggest that a multi-layer depth-averaged mathematical approach would be a suitable tool for improving the modeling of these flows without increasing significantly the computational costs. How to cite: Sarno, L. Conventional sensors for debris flow monitoring suffer from several drawbacks including low service life, low reliability in long-distance data transfer, and stability in severe weather conditions.
Recently, fiber Bragg grating FBG -based sensors have been developed to monitor debris flows. However, they can be easily damaged by the impact forces of boulders within debris flow. This paper presents a new FBG-based device to measure the strain induced by the impact force of debris flow with high reliability and effectiveness.
The effects of the impact forces of debris flows have been investigated. Then, the relationship between the strain and the debris flow energy correlating with the damage to building structures has been established. It is shown that this new FBG-based device is capable of monitoring and warning about debris flows. The impact experiment results show that the peak value of dynamic strain on the fixed end of the new device is positively correlated with the external impact force.
Using an impact force, we establish a relationship between the measured strain and the potential of a debris flow resulting in damage to structures was established. This follows the general rule that a larger measured strain corresponds to a higher level of debris flow. Using this relationship, we can quantify a dangerous level of debris flow using the monitored strain data.
Our new device is capable of monitoring and warning about dangerous debris flows, allowing for more effective debris flow mitigation. How to cite: Zhang, S. It is necessary to understand the physical mechanism of such granular flows impacting obstacles to improve the design of protective structures and the hazard assessment related to such structures.
In this study, the small-scale laboratory experiments were performed to investigate the dynamic impact caused by granular flow around a circular cylinder with variable radius of curvatures and the dynamic impact against a flat wall. Pressure sensors were used to measure the impact pressure of granular flows at both the upstream cylinder surface and at the bottom of the channel. Accelerometers were mounted on the underside of channel to record the seismic signals generated by the granular flows before and during the impact with the obstacle.
Flow velocities and flow depths were determined by using high-precision cameras. The results show that a bow shock wave is generated upstream of the cylinder, causing dynamic pressures on both the obstacle and the bottom of the channel. The dimensionless standoff distance of the granular shock wave decreases nonlinearly or almost exponentially with increasing Froude number Fr in the range of 5.
The dimensionless pinch-off distance and dimensionless run-up height grow linearly with increasing Fr, and they were significantly influenced by the radius of curvature of the structure at the stagnation point RCSSP. The dimensionless impact pressure on the structure surface is sensitive to the RCSSP, while the differences decrease as Fr increases; Seismic signals generated at the underside of the channel and at the top of the cylinder were also recorded to assist in analyzing the effects of RCSSP.
How to cite: Chen, Z. Torrential flows, like debris flows and debris floods, can mobilize large volumes at high velocities in mountainous regions. Therefore, they represent an important erosional process and a significant hazard towards infrastructures and people sometimes catastrophic. Monitoring-based analysis is a crucial task to improve the understanding of the mechanisms triggering torrential flows and its propagation, which are necessary to implement early warning systems.
The monitoring of triggering conditions generally focusses on rainfall measurements and the characterization of the critical rainfall conditions. However, rainfall data do not provide a complete picture of the physical processes involved. In that respect, this study analyses both rainfall and soil moisture data at a Mediterranean-influenced torrential basin located in Central Pyrenees the Rebaixader site.
The Rebaixader site has a high torrential activity, with 11 debris flows and 24 debris floods detected since The temporal distribution of rainfall episodes and torrential flows shows a clear shift between the most frequent rainfall episodes beginning of June and torrential flows mid-July. Regarding critical rainfall conditions, a previously published rainfall threshold was updated including total rainfall duration and mean intensity of rainfalls. On the other hand, measured volumetric water content VWC was analysed for triggering and non-triggering rainfall events.
Preliminary results show lower VWC increment on wetter soils at the beginning of rainstorms that triggered torrential flows. This indicates that soil saturates with lower rainfall amount if the soil is initially wetter; which subsequently generates higher runoff rate and therefore a higher erosion and transport energy that may trigger torrential flows.
In addition, a slight trend was observed when comparing rainfall intensity and soil moisture; generally larger rainfall intensity is necessary to trigger torrential flows when soil is drier. The analysis of VWC data was more complicated in contrast to the one of rainfall data, since the time series are shorter and the physical interpretation is not straightforward.
Therefore, additional data are necessary to confirm and define soil moisture thresholds triggering torrential flows. How to cite: Oorthuis, R. A debris flow occurred in Shiyang gully, located between Hebei Province and Beijing, on 8 June , resulting in 6 people dead or injured. In this study, numerical simulation using FLO-2D was performed to reproduce the debris flow event flow depths, flow velocities, and sediment depositions occurred in The results of the field survey showed that the influential range of debris flow is consistent with the simulation results.
Then, we used FLO-2D is calibrated to simulate debris flows disasters under different rainfall scenarios. As cumulative rainfall and rainfall intensity increase, the risk of Shiyang gully is increasing. This study used FLO-2D simulated process of debris flows triggered by rainfall. The results showed the early warning time and influential range for different intensity ,accumulated precipitation, and rain area, which is beneficial to the debris flow management in the western mountainous areas of Beijing.
How to cite: Li, J. The outreach road of mountain community has been interrupted by disasters such debris flow, flood and landslides, resulting in the interruption of the outreach road of the mountain community, forming a state like an island, which can be regarded as an isolation effect. In recent years, extreme events caused by extreme weather. The special geographical conditions in Taiwan, coupled with the increase in the frequency of natural disasters, have been heard by isolated island news.
Debris flow and landslides occurred, causing the interruption of Xinwu Road, the main liaison road in Wulai, and the isolation effect in Wulai. If we can integrate the historical data and research of isolation effect, and combine the theory of isolated prediction with instant rainfall and disaster prevention information, and finally visualize the information by alert system, it will help the general public's disaster prevention awareness and related disaster prevention unit decision-making reference.
Therefore, this research builds an isolation alert system. The three main information functions of this system include 1. The d isolated geographic information display function is mainly to display the historical information about the isolation effect. The information of the village has been published, including the village's geography, social information and disaster history, and the risk map is presented by the vulnerability and resilience indicators.
The village identification function of the isolated incident is realized by the Common Alerting Protocol of the road, and based on this, the identification in the immediate isolated village is carried out. The immediate disaster isolated warning function combines real-time rainfall information and integrates the Rainfall Triggering Index, Machine Learning's Supervised Learning algorithm, and the Common Alerting Protocol for the road.
In the end, it was verified by the Typhoon Nepartak incident, and the results were all given the correct warning level for the isolated village. How to cite: Tsai, Y. Comparison of the surface velocity of a debris flow at the Gadria creek using pulse compression radar and digital particle image velocimetry DPIV. A central aspect of protection against debris flows is the understanding of the process.
The flow velocity is an important parameter which is used, for example, in the dimensioning of protective structures, for technical building protection and for early warning systems. The measurement of the surface velocity which is regarded as the maximum velocity occurring within a debris flow, is therefore an essential link in the chain of fundamental process research and applied protection against natural hazards.
Due to the further development of various technologies such as video technology and high-frequency radar technology, the non-contact measurement of the surface speed of a debris flow has improved significantly in recent years. Radar technology provides a wide aspect of applications in alpine mass movements such as debris flows, avalanches and rockfall and is able to detect such processes up to a range of meters in distance.
An additional beneficial feature is the possibility of non-contact measurement of the surface velocity. In the catchment area of the Gadria basin South Tyrol, Italy , the measuring station, which has been in operation since , has been extended by a pulse compression radar and a new HD video camera. On July 26, a debris flow consisting of several surges was recorded with both the radar and the HD video camera. The results of the compared surface velocity data showed a value of up to 0.
The results demonstrate the high effectiveness of the pulse compression radar and the DPIV analysis in a wide range of the assessment of surface velocity of natural debris flows. There is great potential in both measuring systems and the chosen comparative analysis provides a blueprint for future recorded debris flows. Debris flows represent great hazard to communities and infrastructures, since they move quickly and are very destructive. In Brazil, debris flows mainly occur in the Serra do Mar Mountain Range, where thousands of casualties were reported in the last two decades due to these phenomena.
Debris-flow magnitude refers to the volume of material discharged during an event and is an important aspect of debris-flow hazard assessment. The Pedra Branca event was initiated by rainfall-triggered shallow landslides, damaging local oil pipelines and farms.
The magnitude estimation is based on the combination of empirically based equations and the geomorphic features of the debris flow, acquired from in situ and aerial investigation. Sediment sources and accumulation areas were identified and delimitated based on high-resolution aerial drone photographs. The results indicate that the landslides that initiated the event released approximately 26, Further research on debris-flow dynamics and recurrence at the Serra do Mar Mountain Range is recommended to mitigate future hazards.
How to cite: Carvalho Cabral, V. In , the typhoon Morakot caused many multimodal sediment disasters in Taiwan. The Soil and Water Conservation Bureau invested a lot of resources in the reconstruction project. To accelerate the stability of soil in the catchment area, and reduce the possibility of secondary disasters. After a period of time, appropriate review and governance benefit assessment should be carried out. In this study, 2 major areas with heavy sediment disasters within the jurisdiction of the Tainan Branch, Soil and Water Conservation Bureau were chose to do hazard and risk assessment.
This study collected the documents of the erosion and sediment control engineering over the years from Then, matched with the field survey, digital elevation model analysis, and using the evaluation matrix to assess the level of hazard and risk of selected major disaster areas. Function of structures are divided into 4 levels: Nice, Good, Poor, and Bad. Landslide rate of watershed LA means the percent of landslide in the watershed.
Upstream channel slope US means the slope of the channel from the middle to the top of watershed. River erosion or siltation change CD means the maximum vertical height change of river bed. Preservation Factor considered the protected targets and the preservation distance. According to the individual scores of the four factors, the weighted average is taken and divided EC into 4 levels.
In this study, we chose two sites, i. From to , the Soil and Water Conservation Bureau practiced 6 erosion and sediment control engineering. According to the results of assessment, the level of function of environment is good, and the level of environmental condition is A. Therefore, the result of hazard and risk assessment is low. Cianghuangkeng has low potential for hazard and risk.
In this way, the evaluation result of hazard and risk assessment in Henansiang is also low. According to the results of evaluation matrix, the potential of hazard and risk could divide into three levels: high H , middle M , low L. This study use evaluation matrix method to assess the hazard and risk of the major disaster areas caused by the typhoon Morakot event. According to the assessment results, we can review whether the remediation strategies and directions of key disaster areas need to be revised.
It will help improve related technologies, provide reference for future related governance planning strategies, and effectively promote the improvement of soil and water conservation. How to cite: Su, Y. The fluidity of a debris flow varies by grain size.
Flows containing principally coarse grains are considered to be laminar and those featuring largely incohesive fine grains turbulent. The transition from laminar to turbulent flow depends on the ratio of flow depth to grain size i. Debris flows with relative flow depths of approximately 10 are entirely laminar; those with relative flow depths over approximately 20 exhibit transitional flow behavior from entirely laminar to partially turbulent.
This transitional flow has been investigated in the laboratory using the resistance law and the vertical distribution of streamwise velocity. The flow exhibits a two-layer structure; the lower layer remains laminar but the upper layer becomes turbulent. However, transition modeling remains incomplete given the lack of data on the internal stresses associated with transitional flow.
Here, we studied the laminar-turbulent transitions of debris flows by measuring basal pore fluid pressures using flume tests. We flowed saturated monodisperse granular materials over an open-channel rigid bed; we used sediment particles of diameters 2. When the debris flow attained the steady state, the flow depth and basal pore fluid pressure were measured using an ultrasonic sensor and pressure gages respectively, and the basal total normal stress estimated using the bulk density of the debris flow assessed at the downstream end.
The relative flow depths ranged from 5 to Comparisons among the measured pore fluid pressures and the hydrostatic and total normal stresses indicated that a pore fluid pressure of 0. In contrast, pore fluid pressures of 2. Pore fluid pressures of 0. By analogy with the Reynolds number for Newtonian fluid, we investigated the transition based on the non-dimensional number for debris flows thus, the ratios of inertial to dynamic stresses caused by interparticle collisions and the Reynolds stresses of the debris flow pore fluid.
This identified the critical Reynolds number in terms of transition commencement. We describe the transitional flow behavior of monodisperse granular debris flows using a two-layered model in which the position of the between-layer interface is estimated based on that critical Reynolds number. How to cite: Sakai, Y. Abstract: Uplift pressure is crucial for the stability of debris flow dam because of its reducing the effective pressure on the dam foundation and the anti-slide force of the dam.
This study investigates the spatial and temporal variations of the uplift pressures during the debris flow impact processes, through a series of flume experiments. Before the debris flow impacting on the dam, the uplift pressure keeps stable due to the steady water level, and then it decreases slightly at the instant of debris flow impacting on the dam which lasts for no more than 1 s, and then increases sharply within a time lag no more than 2 s, and then decreases sharply soon afterwards.
The maximal increasing ratio is 6. The peak pressure occurs before the dam and decreases with the distance from the dam with a nearly linear tendency. The increment of uplift pressure also presents a similar tendency with the distance from the dam. In addition, the uplift pressure is found to be strongly influenced by the permeability of debris flow deposits, especially by the fine content of grain composition, and by the properties of the flow, such as the flow density, runoff volume and hydraulic gradient, and the pressure rises in a nearly linear form with the properties.
How to cite: Chen, X. Abstract: Debris flow monitoring provides valuable data for scitienfic research and early warning, however, it is of difficulty to sucessfully achive because of the great damage of debris flows and the high cost. JJG is loacted in the dry-hot valley of Jinsha River, and the derbis flows are frequent due to the semi-arid climate, deep-cut topography and highly weathered slope surface. A long-term mornitoring work has been conducted in JJG and more than debris flows events has been recorded since The monitoring system consists of 10 rainfall gauges and a measuring section, with instruments to measure the flow depth and velocity; and flow density is measured through sampling the fresh debris flow body.
Ergou lies in the Wenchuan earthquake affected area and the monitoring began in to investigate the characteristics and development tendency of post-earthquake debris flows. Three stations were set up in the mainstream and tributaries, with instruments to measure the flow depth, velocity, and density.
Over 10 debris flow events were recorded up to date. Based on the monitoring output, the rainfall spatial distribution and thresholds for debris flows are proposed. The debris flow dynamics characteristics are analyzed, and the relations between the parameters, e. The debris flow formation modes and the mechanisms in different regions are discriminated and simulation methods are suggested. It is anticipated that the monitoring results will promote understanding of debris flow characteristics in the western China.
How to cite: Guo, X. Processes like flash floods or debris flows, which typically occur in small headwater catchments, represent a substantial natural hazard in alpine regions. Due to the entrainment of sediment, the discharge of debris flows can be up to an order of magnitude larger compared to year fluvial flood events in the same channel, which poses a great threat to affected communities. The modulation analysis determines the modulation type and all important modulation parameters symbol rate, frequency shift, etc.
Depending on the transmission system, the corresponding decoder output will be displayed. Classification, demodulation and decoding. The symbol viewer is used for visualizing symbol data. Symbol view of multichannel PSK signal. Meteosat weather fax. Demodulation and decoding of a Piccolo MK6 signal. Manual parallel processing of multiple signals Frequently, the realtime b and width of a monitoring receiver contains multiple signals simultaneously.
The individual DDCs can set their center frequencies and b and widths within the limits of the processable realtime b and width of the monitoring receiver. Manual processing of multiple signals. A detection result is generated for every detected signal that meets the predefined selection criteria signal duration, b and width, level, etc. The detection results are cyclically compared with the signal scenario from the previous processing cycles.
The user can also configure a rule-based automated workflow that independently h and les the processing of the relevant signals see page Detection threshold and ignoring of frequency ranges The automatically computed detection threshold adapts to the variable noise floor that is typical of a specific frequency range. In scenarios where certain signals or frequency ranges are of no interest, a list of frequency ranges to ignore can be included in the detector algorithms.
The detectors will then stop generating messages for signals in these ranges. Detection using a scanning receiver For signal detection, the receiver is operated in scan mode, which means it can cover any frequency range. The automatic detector operates in the scan spectrum and detects signals as described above. To process e. The automatic detection functionality informs the user about signals and events of potential interest. Fast recognition of signals by spectral matching The spectral shape detector is designed to search for known and unknown signals by performing spectral pattern matching.
It is very fast and customizable i. The decisions of the matching algorithm are based on many criteria within a comprehensive decision matrix, which allows the similarities between input signals and shape description sets to be reliably assessed.
Owing to this unique algorithm, the spectral shape detector can operate effectively across wide frequency ranges, dense signal scenarios, and even under harsh radio conditions. This is the spectral reference library. The patterns in the database can either be specific user-defined signal types with corresponding parameters, or predefined within the detector as generic signal types i.
To increase the robustness of the detector, several different instances of the same signal category are gathered and processed by the spectral collector. The conventional energy detector is combined with a high-performance spectral shape detector to enhance the signal search and recognition process. The lower screenshot shows the result of matching the library of generic and user-defined signal types by using the spectral shape detector.
Based on an automatic algorithm, it selects and gathers a number of spectral shapes that are representative of the signal of interest. These spectral shapes vary because they have been computed at different times i. The spectral collector also manages the repeated collection of different emissions associated with the same signal category. The spectral detector trainer is a st and alone application for extracting relevant spectral information and identifying certain signal types based on a set of spectral sample data.
The extracted spectral features define a specific category of signals. This information is used by the detector to recognize signals with similar spectral characteristics during a spectral shape search. In order to train the detector, the user decides which signal types are of interest, collects the corresponding sample data and defines the desired signal categories.
It is also possible to automatically create a training collection using the spectral detector trainer. Each signal category is represented by a reasonable number of spectral shapes approx. The training is carried out based on a list of shape-describing features derived from the signals within the spectral reference library. In order to achieve a more reliable detection, the set of reference shapes used for training should include examples of degraded signals.
This makes shape detection more robust against negative influences such as noise and fading. Based on the input data from the spectral reference library, the spectral detector trainer creates a profile for the detector for each signal category. Using an automatic decision algorithm, the detector evaluates how well each detected signal matches the characteristics of the trained categories.
Spectral detector trainer. The user defines a set of rules. The signal content is recovered and saved. The maximum duration of the content snapshot can be predefined. These scripts make it possible to define conditions or criteria based on the relevant parameters. When these conditions are met, the script triggers the corresponding actions predefined by the user. The script can also decide when a signal will be skipped and define how long a signal will be recorded if an action is triggered.
This tool has been designed to allow a straightforward approach to script development and to reduce the effort involved in developing the scripts. The filter b and width is automatically adapted to filter out all disturbing out-of-b and emissions and noise. Zoomable level, envelope, frequency, phase and spectrum plots make it possible to measure technical parameters such as level range, frequency shift and symbol rate.
Spectrum, time analysis and digital modulation. For unknown signals, it offers a variety of representations and tools for analyzing and measuring technical parameters such as b and width, symbol rate, number of tones, tone spacing, shift, modulation index, length of guard interval, number of channels, signal duration, symbol valency and modulation type.
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