Lahars in Java: Initiations, Dynamics, Hazard Assessment And Deposition Processes

Lahar has been applied as a general term for rapidly flowing, high-concentration, poorly sorted sediment-laden mixtures of rock debris and water (other than normal streamflow) from a volcano. Lahars are one of the most destructive phenomena associated with composite volcanoes, which are dominant in Java Island. Resulting deposits of lahar are poorly sorted, massive, made up of clasts (chiefly of volcanic composition), that generally include a mud-poor matrix. The aim of this research is threefold: to discuss the initiation of lahars occurrences, their dynamics, to assess the hazard and to analyse the deposition. Lahars are either a direct result of eruptive activity or not temporally related to eruptions. Syn-eruptive lahars may result from the transformation on pyroclastic flows or debris avalanches which transform to aqueous flows (e.g. at Papandayan in November 2002); They may be also generated through lake outburst or breaching (e.g. at Kelut in 1909 or 1966), and through removal of pyroclastic debris by subsequent heavy rainstorms. Post-eruptive lahar occurs during several years after an eruption. At Merapi, lahars are commonly rain-triggered by rainfalls having an average intensity of about 40 mm in 2 hours. Most occur during the rainy season from November to April. Non-eruptive lahars are flows generated without eruptive activity, particularly in the case of a debris avalanche or a lake outburst (e.g., Kelut). A lahar may include one or more discrete flow processes and encompass a variety of rheological flow types and flow transformations. As such, lahars encompass a continuum between debris flows and hyperconcentrated flows, as observed at Merapi, Kelut and Semeru volcanoes. Debris flows, with water contents ranging from 10 to no more than about 25% weight, are non-newtonian fluids that move as fairly coherent masses in what is thought to be predominantly laminar fashion. However, the relative importance of laminar versus turbulent regime is still debatable. Hyperconcentrated streamflows contain 25- to about 40%-weight-water; these flows possess some yield stress, but they are characteristically turbulent. Hazard-zone maps for lahar were produced for most of the the Javanese volcanoes, but these maps are on too small-scale to meet modern zoning requirements. More recently, a few large-scale maps (1/10,000 and 1/2,000-scale) and risk assessments have been completed for a few critical river systems at Merapi.

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Modelling erosion and deposition in geophysical granular mass flows

Europhysics news ◽

10.1051/epn/2021106 ◽

2021 ◽

Vol 52 (1) ◽

pp. 29-32

Author(s):

Sylvain Viroulet ◽

Chris Johnson ◽

Nico Gray

Keyword(s):

Debris Flows ◽

Large Scale ◽

Laboratory Experiments ◽

Pyroclastic Flows ◽

Small Scale ◽

Snow Avalanches ◽

Erosion And Deposition ◽

Granular Rheology ◽

Scale Models ◽

Mass Flows

During hazardous geophysical mass flows, such as rock or snow avalanches, debris flows and volcanic pyroclastic flows, a continuous exchange of material can occur between the slide and the bed. The net balance between erosion and deposition of particles can drastically influence the behaviour of these flows. Recent advances in describing the non-monotonic effective basal friction and the internal granular rheology in depth averaged theories have enabled small scale laboratory experiments (see fig. 1) to be quantitatively reproduced and can also be implemented in large scale models to improve hazard mitigation.

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On turbulent separation in the flow past a bluff body

Journal of Fluid Mechanics ◽

10.1017/s0022112092002118 ◽

1992 ◽

Vol 241 ◽

pp. 443-467 ◽

Cited By ~ 24

Author(s):

A. Neish ◽

F. T. Smith

Keyword(s):

Large Scale ◽

Bluff Body ◽

Separated Flow ◽

Small Scale ◽

Supporting Evidence ◽

Turbulent Regime ◽

Trailing Edge ◽

Flow Past ◽

Starting Point ◽

Turbulence Factor

The basic model problem of separation as predicted by the time-mean boundary-layer equations is studied, with the Cebeci-Smith model for turbulent stresses. The changes between laminar and turbulent flow are investigated by means of a turbulence ‘factor’ which increases from zero for laminar flow to unity for the fully turbulent regime. With an attached-flow starting point, a small increase in the turbulence factor above zero is found to drive the separation singularity towards the trailing edge or rear stagnation point for flow past a circular cylinder, according to both computations and analysis. A separated-flow starting point is found to produce analogous behaviour for the separation point. These findings lead to the suggestion that large-scale separation need not occur at all in the fully turbulent regime at sufficiently high Reynolds number; instead, separation is of small scale, confined near the trailing edge. Comments on the generality of this suggestion are presented, along with some supporting evidence from other computations. Further, the small scale involved theoretically has values which seem reasonable in practical terms.

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A review of the classification of landslides of the flow type

Environmental and Engineering Geoscience ◽

10.2113/gseegeosci.7.3.221 ◽

2001 ◽

Vol 7 (3) ◽

pp. 221-238 ◽

Cited By ~ 600

Author(s):

Oldrich Hungr ◽

S. G. Evans ◽

M. J. Bovis ◽

J. N. Hutchinson

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Large Scale ◽

Debris Avalanche ◽

Basic Material ◽

Morphological Aspects ◽

Flow Slides ◽

Size Limits ◽

Plastic Clays ◽

Earth Flows

Abstract As a result of the widespread use of the landslide classifications of Varnes (1978), and Hutchinson (1988), certain terms describing common types of flow-like mass movements have become entrenched in the language of engineering geology. Example terms include debris flow, debris avalanche and mudslide. Here, more precise definitions of the terms are proposed, which would allow the terms to be retained with their original meanings while making their application less ambiguous. A new division of landslide materials is proposed, based on genetic and morphological aspects rather than arbitrary grain-size limits. The basic material groups include sorted materials: gravel, sand, silt, and clay, unsorted materials: debris, earth and mud, peat and rock. Definitions are proposed for relatively slow non-liquefied sand or gravel flows, extremely rapid sand, silt or debris flow slides accompanied by liquefaction, clay flow slides involving extra-sensitive clays, peat flows, slow to rapid earth flows in nonsensitive plastic clays, debris flows which occur in steep established channels or gullies, mud flows considered as cohesive debris flows, debris floods involving massive sediment transport at limited discharges, debris avalanches which occur on open hill slopes and rock avalanches formed by large scale failures of bedrock.

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Transition from geostrophic flows to inertia-gravity waves in the spectrum of a differentially heated rotating annulus experiment.

10.5194/egusphere-egu2020-9374 ◽

2020 ◽

Author(s):

Costanza Rodda ◽

Uwe Harlander

Keyword(s):

Gravity Waves ◽

Large Scale ◽

Small Scale ◽

Turbulent Regime ◽

Weakly Nonlinear ◽

Geostrophic Flows ◽

Balanced Flow ◽

Energy And Momentum ◽

Open Question ◽

Inertia Gravity Waves

Inertia-gravity waves (IGWs) are known to play an essential role in the terrestrial atmospheric dynamics as they can lead to energy and momentum flux when they propagate upwards. An open question is to which extent nearly linear IGWs contribute to the total energy and to flattening of the energy spectrum observed at the mesoscale. In this work, we present an experimental investigation of the energy distribution between the large-scale balanced flow and the small-scale imbalanced flow. Weakly nonlinear IGWs emitted from baroclinic jets are observed in the differentially heated rotating annulus experiment. Similar to the atmospheric spectra, the experimental kinetic energy spectra reveal the typical subdivision into two distinct regimes with slopes k-3 for the large scales and k-5/3 for smaller scales. By separating the spectra into a vortex and wave part, it emerges that at the largest scales in the mesoscale range the gravity waves observed in the experiment cause a flattening of the spectra and provide most of the energy. At smaller scales, our data analysis suggests a transition towards a turbulent regime with a forward energy cascade up to where dissipation by diffusive processes occurs.

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Transition from Geostrophic Flows to Inertia–Gravity Waves in the Spectrum of a Differentially Heated Rotating Annulus Experiment

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-20-0033.1 ◽

2020 ◽

Vol 77 (8) ◽

pp. 2793-2806

Author(s):

Costanza Rodda ◽

Uwe Harlander

Keyword(s):

Gravity Waves ◽

Large Scale ◽

Small Scale ◽

Turbulent Regime ◽

Weakly Nonlinear ◽

Geostrophic Flows ◽

Balanced Flow ◽

Energy And Momentum ◽

Open Question ◽

Inertia Gravity Waves

Abstract Inertia–gravity waves (IGWs) play an essential role in the terrestrial atmospheric dynamics as they can lead to energy and momentum flux when propagating upward. An open question is to what extent IGWs contribute to the total energy and to the flattening of the energy spectrum observed at the mesoscale. In this work, we present an experimental investigation of the energy distribution between the large-scale balanced flow and the small-scale imbalanced flow. Weakly nonlinear IGWs emitted from baroclinic jets are observed in the differentially heated rotating annulus experiment. Similar to the atmospheric spectra, the experimental kinetic energy spectra reveal the typical subdivision into two distinct regimes with slopes k−3 for the large scales and k−5/3 for the small scales. By separating the spectra into the vortex and wave components, it emerges that at the large-scale end of the mesoscale the gravity waves observed in the experiment cause a flattening of the spectra and provide most of the energy. At smaller scales, our data analysis suggests a transition toward a turbulent regime with a forward energy cascade up to where dissipation by diffusive processes occurs.

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Large Sediment Movement Caused by the Catastrophic Ohya-Kuzure Landslide

Journal of Disaster Research ◽

10.20965/jdr.2010.p0257 ◽

2010 ◽

Vol 5 (3) ◽

pp. 257-263 ◽

Cited By ~ 10

Author(s):

Satoshi Tsuchiya ◽

◽

Fumitoshi Imaizumi ◽

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Strong Earthquake ◽

Large Scale ◽

Upstream Region ◽

Small Scale ◽

Hydraulic Pressure ◽

Sediment Volume ◽

Video Images ◽

Main River

The Ohya-kuzure landslide, one of three largest catastrophic landslides in Japan, is assumed to have been triggered by a strong earthquake and a large-scale debris terrace in a channel downstream from landslide. We verified the time of the landslide’s occurrence, its volume, and the amount of sediment supplied to the main river downstream. The landslide’s occurrence in 1707 was confirmed by historical documents and earthquake records of sediment disasters. The landslide’s size was estimated to be 94 million m3, from the geomorphic change in the debris terrace. Moreover, it was presumed that 33% of the sediment accumulating as a debris terrace (29 million m3) was eroded, and that a sediment volume of 17 million m3 was supplied to the upstream region of the main river. Small-scale debris flows have been triggered recently in the source head of the landslide during heavy annual rainfalls. In 2006, a debris flow in Ichinosawa tributary with the most vigorous debris production and transport in the landslide was recorded during a typhoon. Hydrographs of the debris flow quantified by ultrasonic sensor and hydraulic pressure sensor supplemented video images.

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GCOM-C (SHIKISAI) Second-generation Global Imager infrared observation of active volcanoes: Case studies from the Asia-Pacific region

10.21203/rs.3.rs-27525/v1 ◽

2020 ◽

Author(s):

Takayuki Kaneko ◽

Atsushi Yasuda ◽

Kenji Takasaki ◽

Shun Nakano ◽

Toshitsugu Fujii ◽

...

Keyword(s):

Case Studies ◽

Large Scale ◽

Second Generation ◽

Lava Dome ◽

Global Climate ◽

Thermal Anomaly ◽

Pyroclastic Flows ◽

Asia Pacific ◽

Small Scale ◽

Infrared Observation

Abstract The GCOM-C (SHIKISAI) satellite was developed to understand the mechanisms of global climate change. The Second-generation Global Imager (SGLI) onboard GCOM-C is an optical sensor observing wavelengths from 380 nm to 12.0 µm in 19 bands. One of the notable features is that the resolution of the 1.63-, 10.8-, and 12.0-µm bands is 250 m, with an observation frequency of 2–3 days. To investigate the effective use and potential of the 250-m resolution of these SGLI bands in the study of eruptive activities, we analyzed four practical cases. As an example of large-scale effusive activity, we studied the 2018 Kilauea eruption. By analyzing the series of 10.8-µm band images using cumulative thermal anomaly maps, we could observe that the lava effused on the lower East Rift Zone, initially flowed down the southern slope to the sea, and then moved eastward. As an example of lava dome growth and generation of associated pyroclastic flows, the activity at Sheveluch between December 2018 and December 2019 was analyzed. The 1.63- and 10.8-µm bands were shown to be suitable for observing growth of the lava dome and occurrence of pyroclastic flows, respectively. We found that the pyroclastic flows occurred during periods of rapid lava dome expansion. For the study of an active crater lake, the activity of Ijen during 2019 was analyzed. The lake temperature was found to rise rapidly in mid-May and reach 38 °C in mid-June. We also analyzed the intermittent activities of small-scale Vulcanian eruptions at Sakurajima in 2019. The 1.63-µm band was useful for detecting activities that are associated with Vulcanian eruptions. Analytical results for these case studies demonstrated that the GCOM-C SGLI images are beneficial for observing various aspects of volcanic activity, and their real-time use may contribute to reducing eruption-related disasters.

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Glacial tectonic and flow structures in glaciogenic deposits: a cautionary note

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-1985-34-01 ◽

1985 ◽

Vol 34 ◽

pp. 3-11

Author(s):

C. P. Gravenor

Keyword(s):

Debris Flows ◽

Large Scale ◽

Flow Structures ◽

Small Scale ◽

Cautionary Note ◽

Glacial Deposits ◽

Contact Processes ◽

Flow Processes ◽

Scale Structures ◽

Small Scale Structures

Large scale displacement and deformation of bedrock and associated glacial deposits can be produced by both glacial tectonics and debris flows. Large scale deformation of glacial deposits not associated with displacement of underlying strata can be produced by both glacial tectonics and ice-contact processes. Smaller scale structures such as boudins, stringers of sand and silt and laminated diamictons can be produced by both glacial tectonics and flow processes. Examples of both large and small scale structures produced by flow are presented to emphasize the need for adequate criteria to determine the origin of these structures.

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A new infrared volcano monitoring using GCOM-C (SHIKISAI) satellite: Applications to the Asia-Pacific region

10.21203/rs.3.rs-27525/v2 ◽

2020 ◽

Author(s):

Takayuki Kaneko ◽

Atsushi Yasuda ◽

Kenji Takasaki ◽

Shun Nakano ◽

Toshitsugu Fujii ◽

...

Keyword(s):

Large Scale ◽

Lava Dome ◽

Global Climate ◽

Thermal Anomaly ◽

Pyroclastic Flows ◽

Asia Pacific ◽

Small Scale ◽

Effusive Activity ◽

Lake Temperature ◽

Satellite Applications

Abstract The GCOM-C (SHIKISAI) satellite was developed to understand the mechanisms of global climate change. The Second-generation Global Imager (SGLI) onboard GCOM-C is an optical sensor observing wavelengths from 380 nm to 12.0 μm in 19 bands. One of the notable features is that the resolution of the 1.63-, 10.8-, and 12.0-µm bands is 250 m, with an observation frequency of 2-3 days. To investigate the effective use and potential of the 250-m resolution of these SGLI bands in the study of eruptive activities, we analyzed four practical cases. As an example of large-scale effusive activity, we studied the 2018 Kilauea eruption. By analyzing the series of 10.8-μm band images using cumulative thermal anomaly maps, we could observe that the lava effused on the lower East Rift Zone, initially flowed down the southern slope to the sea, and then moved eastward. As an example of lava dome growth and generation of associated pyroclastic flows, the activity at Sheveluch between December 2018 and December 2019 was analyzed. The 1.63- and 10.8-µm bands were shown to be suitable for observing growth of the lava dome and occurrence of pyroclastic flows, respectively. We found that the pyroclastic flows occurred during periods of rapid lava dome expansion. For the study of an active crater lake, the activity of Ijen during 2019 was analyzed. The lake temperature was found to rise rapidly in mid-May and reach 38 °C in mid-June. We also analyzed the intermittent activities of small-scale Vulcanian eruptions at Sakurajima in 2019. The 1.63-µm band was useful for detecting activities that are associated with Vulcanian eruptions. Analytical results for these case studies demonstrated that the GCOM-C SGLI images are beneficial for observing various aspects of volcanic activity, and their real-time use may contribute to reducing eruption-related disasters.

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Small-Scale Science to Large-Scale Profession

Contemporary Psychology ◽

10.1037/002246 ◽

2000 ◽

Vol 45 (4) ◽

pp. 396-398

Author(s):

Roger Smith

Keyword(s):

Large Scale ◽

Small Scale

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