Multiple debris flow surges monitored directly by DFLP system at Kamikamihori Creek

2021 ◽  
Author(s):  
Takahiro Itoh ◽  
Takahiko Nagayama ◽  
Satoru Matsuda ◽  
Takahisa Mizuyama
Keyword(s):  
Debris Flow ◽  
Volcanic Activity ◽  
Debris Flows ◽  
Sediment Concentration ◽  
Relative Mass ◽  
Geophysical Research ◽  
Monitoring Method ◽  
Flow Measurements ◽  
Flow Monitoring ◽  
Sediment Particles

<p>The monitoring method for direct debris flow measurements using loadcells and so on, that were preliminary developed by WSL in Switzerland (McArdell et al., 2007), was firstly installed in Sakura-jima Island in Japan, where volcanic activity was severe, and many debris flows took place due to deposition of falling ash after eruptions. Debris Flow measurements with Loadcells and Pressure sensors (DFLP) system was installed referring to the method by WSL, and debris flow characteristics such as specific weight and volumetric sediment concentration have been obtained (e.g., Osaka et al., 2014).</p><p> In Japan, as well as in Sakura-jima island, attempts for debris flow monitoring were also carried out at KamiKamihori Creek since 1970s (e.g., Okuda et al., 1980), and there were a lot of debris flow events due to heavy rainfall. KamiKamihori Creek is at western side of Mt. Yake, where volcanic activity was severe at those time. The DFLP system was modified and installed there in November in 2014, because there were a lot of sediment deposition and debris flows took place though volcanic activity has been inactive. Present research could report the following results.  </p><p>(1) Multiple debris floe over five surges were monitored using DFLP system installed in 2014 during 15 minutes in debris flow events on August 29th, 2019. Rainfall intensity for 10 minutes was 12 mm and accumulated depth was 56 mm just before those events. Antecedent time before those events was 4.5 hours.</p><p>(2) The DFLP system measured multiple debris flow surges in events on August 29th, 2019, and sediment concentration was calculated temporary and continuously. Time-averaged sediment concentration and relative mass density are calculated as 0.470 and 1.73, respectively, under flow discharge obtained by images analysis of CCTV video camera. Equilibrium sediment concentration of coarse sediment particles is estimated 0.160 for bed slope of 0.141 (8 degrees) and calculated value using the DFLP system is over than the equilibrium value because of mud phase due to fine sediment particles.</p><p> </p><p>References</p><p>McArdell B.W., Bartelt P., Kowalski J. (2007). Field observations of basal forces and fluid pore pressure in a debris flow, Geophysical Research Letters, Vo. 34, L07406.</p><p>Okuda, S., Suwa, H., Okunishi, K., Yokoyama, K., and Nakano, M. (1980). Observation of the motion of debris flow and its geomorphological effects, Zeitschrift fur Geomorphology, Suppl.-Bd.35, pp. 142–163.</p><p>Osaka T., Utsunomiya R., Tagata S., Itoh T., Mizuyama T. (2014). Debris Flow Monitoring using Load Cells in Sakurajima Island, Proceedings of the Interpraevent 2014 in the Pacific Rim (edited by Fujita, M. et al.), Nov. 25-28, Nara, Japan, 2014, O-14.pdf in DVD.</p>

scholarly journals Applications of simulation technique on debris-flow hazard zone delineation: a case study in Hualien County, Taiwan

2010 ◽  
Vol 10 (3) ◽  
pp. 535-545 ◽  
Author(s):  
S. M. Hsu ◽  
L. B. Chiou ◽  
G. F. Lin ◽  
C. H. Chao ◽  
H. Y. Wen ◽  
...  
Keyword(s):  
Debris Flow ◽  
Yield Stress ◽  
Empirical Model ◽  
Water Conservation ◽  
Debris Flows ◽  
Sediment Concentration ◽  
Hazard Zone ◽  
Debris Flow Hazard ◽  
Debris Flow Disaster ◽  
Soil And Water

Abstract. Debris flows pose severe hazards to communities in mountainous areas, often resulting in the loss of life and property. Helping debris-flow-prone communities delineate potential hazard zones provides local authorities with useful information for developing emergency plans and disaster management policies. In 2003, the Soil and Water Conservation Bureau of Taiwan proposed an empirical model to delineate hazard zones for all creeks (1420 in total) with potential of debris flows and utilized the model to help establish a hazard prevention system. However, the model does not fully consider hydrologic and physiographical conditions for a given creek in simulation. The objective of this study is to propose new approaches that can improve hazard zone delineation accuracy and simulate hazard zones in response to different rainfall intensity. In this study, a two-dimensional commercial model FLO-2D, physically based and taking into account the momentum and energy conservation of flow, was used to simulate debris-flow inundated areas. Sensitivity analysis with the model was conducted to determine the main influence parameters which affect debris flow simulation. Results indicate that the roughness coefficient, yield stress and volumetric sediment concentration dominate the computed results. To improve accuracy of the model, the study examined the performance of the rainfall-runoff model of FLO-2D as compared with that of the HSPF (Hydrological Simulation Program Fortran) model, and then the proper values of the significant parameters were evaluated through the calibration process. Results reveal that the HSPF model has a better performance than the FLO-2D model at peak flow and flow recession period, and the volumetric sediment concentration and yield stress can be estimated by the channel slope. The validation of the model for simulating debris-flow hazard zones has been confirmed by a comparison of field evidence from historical debris-flow disaster data. The model can successfully replicate the influence zone of the debris-flow disaster event with an acceptable error and demonstrate a better result than the empirical model adopted by the Soil and Water Conservation Bureau of Taiwan.

Debris flow monitoring in China

2020 ◽  
Author(s):  
Xiaojun Guo
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Characteristics ◽  
Western China ◽  
Flow Density ◽  
Flow Depth ◽  
Jinsha River ◽  
Flow Monitoring ◽  
Jiangjia Gully ◽  
Set Up

<p><strong>Abstract: </strong>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. This report introduces monitoring systems in two debris flow watersheds in western China, the Jiangjia gully (JJG) in Yunnan Province and the Ergou valley in Sichuan Province. 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 500 debris flows events has been recorded since 1965. 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 2013 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.</p><p>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.g. density, velocity, discharge and grain compositions are presented. 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.</p><p><strong>Keywords:</strong> Debris flow, monitoring, rainfall, discharge, formation. </p>

scholarly journals Study on debris flow risk monitoring and Early Warning in Nujiang Prefecture, Yunnan Province, China

2021 ◽  
Vol 906 (1) ◽  
pp. 012003
Author(s):  
Qianrui Huang ◽  
Shuran Yang ◽  
Xianfeng Cheng ◽  
Yungang Xiang
Keyword(s):  
Debris Flow ◽  
Early Warning ◽  
Yunnan Province ◽  
Local Economic Development ◽  
Research Field ◽  
Monitoring Method ◽  
Flow Monitoring ◽  
Geological Disasters ◽  
Geological Disaster ◽  
Monitoring And Early Warning

Abstract Debris flow is the mainly the geological disasters in Nujiang Prefecture, while precipitation is the trigger of it, how to implement debris flow forecast based on precipitation monitoring data or forecast data is a hot issue in current debris flow disaster research field. Because of the special geomorphology in Nujiang Prefecture, due to the influence of human activities, geological disasters occur frequently, severely affect the local economic development. As a demonstration area of geological disaster monitoring and early warning in Yunnan Province, to build a well-developed geological disaster warning system, it is very important to spread it to other parts of Yunnan province. Based on the analysis of the current situation of geological disasters in Nujiang Prefecture, adopt appropriate monitoring method and calculation method to select the primary sites for debris flow monitoring and early warning in the Nu River basin for research.

scholarly journals Analysis of different water-sediment flow processes in a mountain torrent

2004 ◽  
Vol 4 (5/6) ◽  
pp. 783-791 ◽  
Author(s):  
M. Arattano ◽  
L. Franzi
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rheological Behaviour ◽  
Field Observations ◽  
Flow Monitoring ◽  
Water Flows ◽  
Field Investigations ◽  
Load Transport ◽  
Bed Load Transport ◽  
Sediment Flow

Abstract. Sediment – water flows occurring in mountain torrents may show a variety of regimes, ranging from water flows with transport of individual particles to massive transport of debris, as it occurs in case of debris flows. Sometimes it is possible, by means of accurate field investigations, to identify the kind of processes that took place in a torrent after the occurrence of an event. However this procedure cannot give indications regarding the development of the process in time. In fact, because of the frequent presence of different surges within the same event, the rheological characteristics of an event can be detected only when some recorded hydrographs or videos are available. For the same reason, since the rheological behaviour of the flow changes according to the solid concentration, the analysis of the materials deposited on the debris fan cannot directly give any information on the particular types of flow that took place: a possible alternation in time of different water sediment surges with different concentrations may have occurred, during the same event. The installation of ultrasonic gauges or videocameras along the torrent might give more information on this issue. To this regard, the analysis of a flow event which occurred in 2002 in the Moscardo torrent watershed, instrumented for debris flow monitoring, has been undertaken, studying the hydrographs recorded at two different ultrasonic gauges placed at a known distance along the torrent. An empirical flow resistance law has been applied analysing the values assumed by its parameters after calibration. The application of this law actually spans from debris flow and immature debris flow to bed load transport. Only field observations and surveys, together with ultrasonic data, may allow to clearly discriminate which type of flow really occurred. The analysis confirms that different water sediment surges alternated in time while the mathematical simulation of the flow compared with field observations revealed that the dynamic behaviour of the flow was different from that of previous debris flow events and might reflect, among the different types of possible rheological behaviors, a dilatant-type behavior typical of stony debris flows.

scholarly journals Basal interstitial water pressure in laboratory debris flows over a rigid bed in an open channel

2012 ◽  
Vol 12 (8) ◽  
pp. 2499-2505 ◽  
Author(s):  
N. Hotta
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Interstitial Water ◽  
Water Pressure ◽  
Pressure Gauge ◽  
Sediment Concentration ◽  
High Temporal Resolution ◽  
Essential Information ◽  
Linear Behavior ◽  
Before And After

Abstract. Measuring the interstitial water pressure of debris flows under various conditions gives essential information on the flow stress structure. This study measured the basal interstitial water pressure during debris flow routing experiments in a laboratory flume. Because a sensitive pressure gauge is required to measure the interstitial water pressure in shallow laboratory debris flows, a differential gas pressure gauge with an attached diaphragm was used. Although this system required calibration before and after each experiment, it showed a linear behavior and a sufficiently high temporal resolution for measuring the interstitial water pressure of debris flows. The values of the interstitial water pressure were low. However, an excess of pressure beyond the hydrostatic pressure was observed with increasing sediment particle size. The measured excess pressure corresponded to the theoretical excess interstitial water pressure, derived as a Reynolds stress in the interstitial water of boulder debris flows. Turbulence was thought to induce a strong shear in the interstitial space of sediment particles. The interstitial water pressure in boulder debris flows should be affected by the fine sediment concentration and the phase transition from laminar to turbulent debris flow; this should be the subject of future studies.

scholarly journals Acoustic module of the Acquabona (Italy) debris flow monitoring system

2005 ◽  
Vol 5 (2) ◽  
pp. 211-215 ◽  
Author(s):  
A. Galgaro ◽  
P. R. Tecca ◽  
R. Genevois ◽  
A. M. Deganutti
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Regression Line ◽  
Front Velocity ◽  
Peak Discharge ◽  
Physical Parameters ◽  
Flow Depth ◽  
Ground Vibrations ◽  
Mountain Areas ◽  
Flow Monitoring

Abstract. Monitoring of debris flows aimed to the assessment of their physical parameters is very important both for theoretical and practical purposes. Peak discharge and total volume of debris flows are crucial for designing effective countermeasures in many populated mountain areas where losses of lives and property damage could be avoided. This study quantifies the relationship between flow depth, acoustic amplitude of debris flow induced ground vibrations and front velocity in the experimental catchment of Acquabona, Eastern Dolomites, Italy. The analysis of data brought about the results described in the following. Debris flow depth and amplitude of the flow-induced ground vibrations show a good positive correlation. Estimation of both mean front velocity and peak discharge can be simply obtained monitoring the ground vibrations, through geophones installed close to the flow channel; the total volume of debris flow can be so directly estimated from the integral of the ground vibrations using a regression line. The application of acoustic technique to debris flow monitoring seems to be of the outmost relevance in risk reduction policies and in the correct management of the territory. Moreover this estimation is possible in other catchments producing debris flows of similar characteristics by means of their acoustic characterisation through quick and simple field tests (Standard Penetration Tests and seismic refraction surveys).

scholarly journals A debris-flow monitoring devices and methods bibliography

2005 ◽  
Vol 5 (6) ◽  
pp. 971-977 ◽  
Author(s):  
Y. Itakura ◽  
H. Inaba ◽  
T. Sawada
Keyword(s):  
Debris Flow ◽  
Integrated System ◽  
Hazard Map ◽  
Flow Measurements ◽  
Control Structures ◽  
Flow Monitoring ◽  
Future Developments ◽  
Discharge Estimation ◽  
Monitoring Devices ◽  
Proximity Sensing

Abstract. Debris-flow monitoring has two functions, warning and modeling. The warning function includes the following parameters: occurrence prediction and detection, proximity sensing, and discharge-estimation. The parameters obtained from debris-flow measurements can deduce a numerical model for creating a hazard map and designing various types of control structures to mitigate the hazards. Many devices and methods of monitoring are tabulated here for comparative study. Some of them are in operation. Advanced comparative studies lead to an improvement in debris-flow monitoring, an integrated system that can be applied to any torrent, and a breakthrough in future developments.

scholarly journals Exploiting LSPIV to assess debris flow velocities in the field

2017 ◽  
Author(s):  
Joshua I. Theule ◽  
Stefano Crema ◽  
Lorenzo Marchi ◽  
Marco Cavalli ◽  
Francesco Comiti
Keyword(s):  
Debris Flow ◽  
Sediment Trap ◽  
Debris Flows ◽  
Large Scale ◽  
Sediment Concentration ◽  
Surface Velocity ◽  
Preliminary Treatment ◽  
Flow Surface ◽  
Image Velocimetry ◽  
Scale Particle

Abstract. The assessment of flow velocity has a central role in quantitative analysis of debris flows, both for the characterization of the phenomenology of these processes, and for the assessment of related hazards. Large scale particle image velocimetry (LSPIV) can contribute to the assessment of surface velocity of debris flows, provided that the specific features of these processes (e.g. fast stage variations and particles up to boulder size on the flow surface) are taken into account. Three debris flow events, each of them consisting of several surges featuring different sediment concentration, flow stage and velocity, have been analyzed at the inlet of a sediment trap in a stream of the eastern Italian Alps (Gadria Creek). Free softwares have been employed for preliminary treatment (ortho-rectification and format conversion) of video-recorded images as well as for LSPIV application. Results show that LSPIV velocities are consistent with manual measurements on the ortho-rectified imagery and with front velocity measured from the hydrographs in a channel reach approximately 70 m upstream of the sediment trap. Horizontal turbulence, computed as the standard deviation of the flow directions at a given cross-section for a given surge, proved to be correlated with surface velocity and with visually estimated sediment concentration. The study demonstrates the effectiveness of LSPIV in the assessment of surface velocity of debris flows, and permit to identify the most crucial aspects for improving the accuracy of debris flows velocity measurements.

A two-phase dilatant debris flow model based on full scale shear stress and pore pressure measurements

2020 ◽  
Author(s):  
Guillaume Meyrat
Keyword(s):  
Shear Stress ◽  
Debris Flow ◽  
Pore Pressure ◽  
Debris Flows ◽  
Flow Model ◽  
Fluid Composition ◽  
Geophysical Research ◽  
Two Phase ◽  
Non Linear ◽  
Fluid Pore Pressure

<p>Since 2004, observations of shear and normal stresses have been collected at the base of naturally-triggered debris flows at the Illgraben observation station (Wallis, Switzerland) [1].   Because flow height and the normal force are simultaneously measured, and limited observations of basal fluid pore pressure are available, it is possible to investigate how the solid/fluid contents of the flow influence the measured shear stress.  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. (2) The relationship between the measured shear and normal tress is highly non-linear. </p><p>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 underlying idea behind the model is that the granular content of the flow can dilate, changing the solid/fluid composition of the flow, and thereby alter the bulk flow density. 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 [2], and later developed in detail by Iverson and George [3]. The model is used to back-calculate recent debris flow events that occurred near Davos Switzerland in 2018/2019.</p><p> </p><p> </p><p> </p><p>REFERENCES</p><ol><li>McArdell, B.W., Bartelt, P. and Kowalski, J. (2007): Field observations of basal forces and fluid pore pressure in a debris flow, Geophysical Research Letters, Vol. 34, No. L07406.</li> </ol><p> </p><ol><li>Takahashi, T. (2007): Debris flows: mechanics, prediction and countermeasures, Taylor and Francis / Balkema, 448pp.</li> </ol><p> </p><ol><li>George, D. L., & Iverson, R. M. (2011). A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure. Italian journal of engineering geology and Environment, 43, 415-424.</li> </ol>

scholarly journals Analysis of the ground vibration produced by debris flows and other torrential processes at the Rebaixader monitoring site (Central Pyrenees, Spain)

2013 ◽  
Vol 1 (4) ◽  
pp. 4389-4423 ◽  
Author(s):  
C. Abancó ◽  
M. Hürlimann ◽  
J. Moya
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Ground Vibration ◽  
Monitoring Site ◽  
Site Specific ◽  
Flow Monitoring ◽  
Vibration Sensors ◽  
Specific Factors ◽  
Flow Detection ◽  
Central Pyrenees

Abstract. The use of ground vibration sensors for debris-flow monitoring has increased in the last two decades. However, the correct interpretation of the seismic signals produced by debris flows still presents many uncertainties. In the Rebaixader monitoring site (Central Pyrenees, Spain) two different ground vibration stations with different characteristics in terms of recording systems and site-specific factors have been compared. The shape of the time series has been recognised as one of the key parameters to identify events and to distinguish between different types of torrential processes. The results show that the site-specific factors strongly influence on the ground vibration registered at each geophone. The attenuation of the signal with the distance has been identified as linear to exponential. In addition, the assembly of the geophones to the terrain also has an important effect on the amplification of the signal. All these results highlight that the definition of ground vibration thresholds for debris-flow detection or warning purposes is a difficult task which is clearly influenced by site-specific conditions of the geophones.

Sign in / Sign up

Export Citation Format

Share Document