Lahars Research Articles

Integrating X-MP radar data to estimate rainfall induced debris flow in the Merapi volcanic area

Abstract After the 2010 eruption, more than 50 volcanic debris flow (lahar) events occurred during the rainy season of 2010–2011 at Mount Merapi, Indonesia. The lahars occurred following rainfall of severe intensity in the upstream area, where remaining volcanic material was deposited. Estimation of rainfall-induced lahars at Mt. Merapi is difficult and uncertain because the upstream area is dangerous and inaccessible. On 17 February 2016, a lahar occurred in the upstream region of the Gendol River on the southeastern flank of Mt. Merapi after a maximum rainfall intensity of 69 mm/h was monitored on the peak of Mt. Merapi by X-band multi-parameter (X-MP) radar. In this study, rainfall intensity estimates from X-MP radar were applied to generate boundary discharge of a numerical model of debris flow at the catchment scale. The numerical simulation was able to estimate volcanic debris flow occurrence and magnitude. The reliability of radar-rainfall data and the effects of the sabo dam on reducing the impacts of lahar disaster were also examined. The numerical lahar simulation showed relevant results that were comparable to the real condition. The closed type sabo dam caused more than 50% lahar sediment decrement and a flow delay time of 40 min. However, the sediment accumulation has caused increasing flow velocity and higher erosion rate in the 2D area. This study demonstrated the effectiveness of remote monitoring of rainfall combined with numerical debris flow modeling for applied practical use in disaster management.

D31-01 浅間山天明火山泥流の流下範囲と噴出箇所について (2)

D31-01 浅間山天明火山泥流の流下範囲と噴出箇所について (2)

E12-10 浅間山天明火山泥流の流下範囲と噴出箇所について (1)

E12-10 浅間山天明火山泥流の流下範囲と噴出箇所について (1)

富士山の地質と地下水流動

Mt. Fuji, at 3,776m, is a stratovolcano located on the Pacific coast of central Japan. It started to form at ca. 100,000 yr. B.P. and continued eruptions ejected huge quantities of basaltic lavas and volcanic ashes. Its activities are divided into two stages: before and after ca. 11,000 yr. B.P. The old stage, or the Ko-Fuji stage, is characterized by frequent volcanic mudflows and ashes, and the new stage, or the Shin-Fuji stage, is characterized by continuous effusions of enormous basaltic lava flows at its initial phase. Basaltic lava flows ejected at the initial phase of the Shin-Fuji stage flew extended to cover most of the foot of the volcano. There are many springs at the foot of Mt. Fuji. Among these, large springs such as the Kakidagawa and Wakuike are located at the termini of the lava flows of the Shin-Fuji stage. Groundwater recharged at the upper parts of Mt. Fuji flows down the flanks under confined conditions through clincker zones formed above and below the massive central cores of basaltic lava flows. At the termini of the lava flows, confined groundwater gushes out of the clinker zones under pressure, forming many large springs. Hydrologic studies indicate that the total recharge to these confined aquifers in Mt. Fuji is ca. 4,700,000 m3/day.

The cultural politics of mining and natural disaster in Indonesia: by fire and sword.

Natural disasters are inevitably the outcome of cultural agonisms. The cultural politics of natural disasters are shaped by competing claims and conceptions of 'nature'. Recent disasters in Indonesia are directly linked to these contending conceptions and the ways in which different social groups imagine risk and reward. The Sidoarjo volcanic mudflow of 2006 represents a volatile and violent exemplar of contending cultural and economic claims. Like other disasters in Indonesia and elsewhere in the developing world, this 'natural' disaster is characterised by differing conceptions of 'nature' as cultural tradition, divine force, and natural resource. A new extractive project in East Java is exhibiting similar economic and cultural agonisms, particularly around the notion of development, environment, self-determination, and tradition. This paper examines the 'disputes over meaning' associated with natural disasters in contemporary societies, and the ways in which they are related to human culture, social organisation, and hierarchical systems of violence.

Disaster map of the Taisho volcanic mudflow informing the arrival time and the level of damage after the eruption of Mt. Tokachi in 1926

Disaster map of the Taisho volcanic mudflow informing the arrival time and the level of damage after the eruption of Mt. Tokachi in 1926

Disaster risk reduction and resettlement efforts at San Vicente (Chichontepec) Volcano, El Salvador: toward understanding social and geophysical vulnerability

Despite a long history of volcanic debris flows on the northern flank of San Vicente Volcano, El Salvador, authorities and communities were ill-prepared for the lahars that occurred on Nov. 7–8, 2009. More than 250 people were killed by lahars resulting from shallow landslides, not to mention millions of dollars (US) in damage to houses, agriculture, and infrastructure. After the disaster, significant aid was invested in the region to reduce risk in future disasters. This case study uses the ethnographic tools of qualitative interviews, participant observation, and review of institutional documents to analyze two particular aspects of disaster risk reduction strategies in the town of Verapaz: 1) relocation of at-risk residents led by the Ministry of Housing and Urban Development, and 2) hazard monitoring and emergency management training programs led by Civil Protection, the University of El Salvador, and NGOs. The relocation effort, while effective at reducing physical vulnerability to debris flows, failed to incorporate livelihood, social networks, and cultural ties to homes in their project design and implementation. Since diverse livelihoods are keys to survival, and tightly-knit social networks help families share responsibilities and withstand shocks during hardships, many families returned to the high-risk area or opted not to relocate. Others have adapted using unanticipated strategies to benefit from the resettlement effort. On the other hand, the emergency management training and education programs valued local input, knowledge, and action, which has helped increase awareness and improved the overall capacity to manage emergencies through wide, local participation. The different approaches used in the two risk reduction initiatives reveal important lessons regarding the importance of community participation. Challenges derive from narrow understandings of vulnerability on the part of disaster risk reduction experts, who neglected to consider and understand kin networks and residence patterns that help maintain diverse livelihoods, as well as ensure safety and security. As demonstrated in the 2011 Tropical Depression 12E, effective public engagement and empowerment helped bridge the knowledge, awareness, and preparedness gaps that existed prior to the 2009 disaster.

An experimental research on snowmelt with hot sediment supply for elucidation of snowmelt-type volcanic mudflow initiation processes

An experimental research on snowmelt with hot sediment supply for elucidation of snowmelt-type volcanic mudflow initiation processes

English

Repeated observations of forest development using permanent plots can map pathways and rates of primary succession at the individual plant, the plot and the community level. This study re-measures the trees in 34 100 m2 plots that were first sampled in 1987 to document recent and to predict continued forest development for a mixed-conifer forest established on a volcanic mudflow formed at a 2000-m elevation in Lassen Volcanic National Park (LVNP) in 1915. In 1987 and 2008, trees ≥ 0.11-m tall were identified to species level, and measured for height (m) and basal area (m2). The most abundant species in both 1987 and 2008 were Pinus contorta, Abies magnifica and Pinus monticola, and there was no statistically significant difference in species composition despite a 20% increase in tree densities. From 1987 to 2008, the mean (± SE) proportional rates of increase for the number of trees per plot, the mean heights of trees and the total basal area per plot were, respectively, 0.009 ± 0.002 y-1, 0.023 ± 0.002 y-1, and 0.055 ± 0.004 y-1. Despite these increases, canopy closure has not occurred for most of the forest. This lack of closure, in conjunction with the continuing similarity of relative species abundances, suggests that abiotic factors such as snow damage and drought and not biotic interactions such as competition may still be the major limitation to tree growth and forest development. Projecting the current rates of basal area growth for the next 10 to 20 years suggests rapid forest development that includes canopy closure. In expectation of these rapid changes, data on tree positions within plots were collected to allow the fates of individual trees to be monitored and determined.    Key words: Pinus contorta, conifers, primary succession, volcanism, mudflow. &nbsp

Catastrophic emplacement of the gigantic Markagunt gravity slide, southwest Utah (USA): Implications for hazards associated with sector collapse of volcanic fields

The newly recognized Markagunt gravity slide (MGS) represents gravitationally induced, catastrophic collapse, ca. 21–22 Ma, of the southwest sector of the Oligocene to Miocene Marysvale volcanic field in southwest Utah (USA). The ∼90-km-long slide mass consists of ∼1700–2000 km 3 of andesitic volcanic mudflow breccias and subordinate lava flows, sandstones, and intertongued regional ash-flow tuffs. The MGS extends over an area of >3400 km 2 and advanced >30 km to the south over the Miocene land surface. The low-angle basal slip surface is in Eocene–Oligocene Brian Head Formation, a weak, clay-rich, tuffaceous sedimentary unit at the base of the volcanic section. The presence of a basal zone of cataclastic and sheared breccia with associated clastic dikes, and pseudotachylyte along secondary shear planes, provides strong evidence of catastrophic emplacement. The uniformity of directional indicators, stratigraphy, and overall geometry of the MGS suggests that it represents a single-emplacement event coeval with late-stage magmatic doming of the volcanic field. The MGS thus represents one of the largest subaerial volcanic landslides on Earth, and along with the comparable Heart Mountain gravity slide in northwest Wyoming, constitutes a class of catastrophic collapse hazard not widely recognized within modern volcanic fields.

Paleoindian sites from the Basin of Mexico: Evidence from stratigraphy, tephrochronology and dating

We present new data on the stratigraphy, dating and tephrochonology at the most important Paleoindian sites in the Basin of Mexico. These include: a) Peñon Woman III, with the oldest directly radiocarbon dated human remains (10,755 ± 75 BP); b) Tlapacoya, with two human crania dated to just over 10 ka BP; c) Tocuila, an important mammoth site with incorporation of fossils and suggested bone tools within the Upper Toluca Pumice (UTP) lahar (volcanic mudflow). The Tocuila site also includes potential evidence for a layer associated with the Younger Dryas meteorite airburst, with charcoal, iron microspherules, micro-tektites (melted glass) and volcanic ash, dated to 10,800 ± 50 BP and d) the Santa Isabel Iztapan mammoths I and II with lithics of Scottsbluff, Lerma and Angostura types and obsidian prismatic blades but lacking the characteristic fluted Clovis type points normally associated with mammoth kills and butchering and dated after the Pumice with Andesite (PWA) layer between 14,500 BP and 10,900 BP, before the Younger Dryas interval. These results show that these lithic traditions in Central Mexico are older than in the Great Plains of USA. Several tephra markers are recognised in the sites that help to constrain the stratigraphy and dating of the archaeological sequences. However tephra reworking in marginal lake sites is present and has been carefully considered, especially for the PWA tephra.

Tocuila Mammoths, Basin of Mexico: Late Pleistocene–Early Holocene stratigraphy and the geological context of the bone accumulation

We report new stratigraphic, tephrochronology and dating results from the Tocuila Mammoth site in the Basin of Mexico. At the site there is evidence for a thin meteorite airburst layer dated between 10,878 and 10,707 cal BC at the onset of the Younger Dryas (YD) cool period. The Upper Toluca Pumice (UTP) tephra marker, caused by a Plinian eruption of the Nevado de Toluca volcano, dated from 10,666 to 10,612 cal BC, is above that layer. The eruption must have caused widespread environmental disruption in the region with evidence of extensive reworking and channelling by the Lake Texcoco shoreline and contributed to the widespread death and/or extinction of megafaunal populations, as suggested by earlier authors, but the new work reinforces the view that both catastrophic events must have caused large environmental disruption in a short time period of around two hundred years. There is no evidence for megafauna (mammoths, sabre toothed cats, camels, bison, glyptodonts) after the UTP volcanic event and subsequent lahars in the Basin of Mexico. At Tocuila, although there are some in situ tephra markers in nearshore lake sediments, such as the Great Basaltic Ash (GBA) and the UTP Ash, there is evidence of much reworking of several tephra populations in various combinations. The mammoth bone accumulation is reworked in a lahar sequence (volcanic mudflow) derived from several source sediments but associated with the major UTP Plinian eruption. Paleoindian populations were also present in the Basin of Mexico during the YD period, where several Paleoindian skeletons were found associated with the UTP ash deposits, e.g. Metro Man, Chimalhuacan Man and Tlapacoya Man.

MUDFLOW DISTURBANCE IN LATEST MIOCENE FORESTS IN LEWIS COUNTY, WASHINGTON

ABSTRACT The lower part of the Wilkes Formation (uppermost Miocene) exposed along lower Salmon Creek in Lewis County, Washington, consists of volcaniclastic-dominated deposits. The section contains a stacked series of volcanic runout mudstone beds overlain by more distal runout mudstone beds, interlayered with carbonaceous mudstone and lignite-woodmat beds that are in turn overlain by poorly sorted volcaniclastic mudstone and sandstone. The section contains a record of forested lowlands inundated by volcanic mudflows, followed sequentially by rising water level associated first with deposition in swamp and lake-margin environments and later by deposition in a lake environment. The lakebed sediments contain common siderite concretions of varied form, including coprolite-shaped concretions that are confined to lakebed deposits. The volcanic mudflow deposits are similar to deposits of mudflows-lahars of modern Cascades stratovolcanoes. Two volcanic ash fall beds contained within lignites in the middle of the...

Pyroclastic density current volume estimation after the 2010 Merapi volcano eruption using X-band SAR

Pyroclastic density current deposits remobilized by water during periods of heavy rainfall trigger lahars (volcanic mudflows) that affect inhabited areas at considerable distance from volcanoes, even years after an eruption. Here we present an innovative approach to detect and estimate the thickness and volume of pyroclastic density current (PDC) deposits as well as erosional versus depositional environments. We use SAR interferometry to compare an airborne digital surface model (DSM) acquired in 2004 to a post eruption 2010 DSM created using COSMO-SkyMed satellite data to estimate the volume of 2010 Merapi eruption PDC deposits along the Gendol river (Kali Gendol, KG). Results show PDC thicknesses of up to 75m in canyons and a volume of about 40×106m3, mainly along KG, and at distances of up to 16km from the volcano summit. This volume estimate corresponds mainly to the 2010 pyroclastic deposits along the KG — material that is potentially available to produce lahars. Our volume estimate is approximately twice that estimated by field studies, a difference we consider acceptable given the uncertainties involved in both satellite- and field-based methods. Our technique can be used to rapidly evaluate volumes of PDC deposits at active volcanoes, in remote settings and where continuous activity may prevent field observations.

Combining criteria for delineating lahar- and flash-flood-prone hazard and risk zones for the city of Arequipa, Peru

Abstract. Arequipa, the second largest city in Peru, is exposed to many natural hazards, most notably earthquakes, volcanic eruptions, landslides, lahars (volcanic debris flows), and flash floods. Of these, lahars and flash floods, triggered by occasional torrential rainfall, pose the most frequently occurring hazards that can affect the city and its environs, in particular the areas containing low-income neighbourhoods. This paper presents and discusses criteria for delineating areas prone to flash flood and lahar hazards, which are localized along the usually dry (except for the rainy season) ravines and channels of the Río Chili and its tributaries that dissect the city. Our risk-evaluation study is based mostly on field surveys and mapping, but we also took into account quality and structural integrity of buildings, available socio-economic data, and information gained from interviews with risk-managers officials. In our evaluation of the vulnerability of various parts of the city, in addition to geological and physical parameters, we also took into account selected socio-economic parameters, such as the educational and poverty level of the population, unemployment figures, and population density. In addition, we utilized a criterion of the "isolation factor", based on distances to access emergency resources (hospitals, shelters or safety areas, and water) in each city block. By combining the hazard, vulnerability and exposure criteria, we produced detailed risk-zone maps at the city-block scale, covering the whole city of Arequipa and adjacent suburbs. Not surprisingly, these maps show that the areas at high risk coincide with blocks or districts with populations at low socio-economic levels. Inhabitants at greatest risk are the poor recent immigrants from rural areas who live in unauthorized settlements in the outskirts of the city in the upper parts of the valleys. Such settlements are highly exposed to natural hazards and have little access to vital resources. Our study provides good rationale for the risk zoning of the city, which in turn may be used as an educational tool for better understanding the potential effects of natural hazards and the exposure of the population residing in and around Arequipa. We hope that our work and the risk-zonation maps will provide the impetus and basis for risk-management authorities of the Municipality and the regional government of Arequipa to enforce existing regulations in building in hazardous zones and to adopt an effective long-term strategy to reduce risks from lahar, flash flood, and other natural hazards.

Kali Code: From Merapi to Sustainable Society

Kali Code is one of the important river for Daerah Istimewa Yogyakarta (DIY) Province and Yogyakarta people. Its main function is to let through the volcanic mudflow from Merapi eruption. However, substantially, the Kali Code value and function is not limited to those values but it has the social, political, cultural, and economical as well. These values are important to the DIY, Yogyakarta people and also the outsiders. The Kampung Code people through their daily lives actualize Kali Code value in various social activities. Through this interpretation, Kali Code is one of important element of Kampung Code people in achieving the sustainable society. As the findings have shown, the value interpretation of Kali Code has became one of the basis in better society building in Kali Code river bank settlement, especially Kampung Code.

Depositional history of diamictites from the Late Paleoproterozoic Dalma Formation (E India)

The Paleoproterozoic Dalma Formation, situated on the Singhbhum craton in eastern India, consists almost entirely of mafic to ultramafic rocks that were deposited by effusive volcanic activity and as pyroclastic deposits. The main focus of the present study, however, is on diamictites, consisting – like both other rock types – exclusively of chlorite and actinolitic hornblende, that are intercalated with these volcanic rocks. These diamictites are interpreted as mass-flow deposits. The textures and mineralogical composition of the diamictites suggests a volcanic origin of the material; most probably they are reworked pyroclastic deposits with the same mineralogy as the Dalma lavas. On this basis, it is concluded that the diamictites represent the deposits of one or more volcanic mudflows. They must have formed of material that had already travelled over a considerable distance in the form of grain-by-grain transport, as indicated by the presence of both rounded and distinctly broken clasts, and by the relatively small size of the clasts. Both the grain-by-grain and the mass transport must have occurred following pathways that were covered all over with volcanic material of mafic composition. This transport must have taken place under terrestrial conditions, as no marine or lacustrine clasts or matrix is included. The results of the study suggest that the diamictites within the Dalma Formation cannot be seen as a possible equivalent of Paleoproterozoic glacigenic sediments such as known from Australia and South Africa.

Experimental study on the factors leading to unique hydrograph of snowmelt-type volcanic mudflow caused by covering of pyroclastic materials

Experimental study on the factors leading to unique hydrograph of snowmelt-type volcanic mudflow caused by covering of pyroclastic materials

An application-driven approach to terrain model construction

Terrain is a surface phenomenon that is measured, modelled, and mapped. However, it is continuously variable and must be simulated by points or mathematical equations that are inherently approximations. The error induced by digitally represented terrain can propagate to surface derivatives and geographical information science (GIS) applications where topography is considered. This can lead to uncertainty in model predictions and the use of data that are unfit for the application to which they are intended. This article outlines the problem of uncertainty in terrain representation and demonstrates the consequences for volcanic mudflow modelling. The response of a simple least-cost single flow algorithm to input parameters was investigated in order to assess output variation from the different sources of input variation. Elevation error was modelled with a probability density function (PDF) and propagated through stochastic simulation (Monte Carlo). Such combined uncertainty and sensitivity analyses enabled a qualitative judgement of the relative significance of elevation error on the flow model prediction. Different methods for terrain model construction were considered and show that supplementing global positioning system (GPS) measurements with information from field notes and reconnaissance photographs greatly improved the model performance and reduced the uncertainty. It is concluded that in terms of validity of model results, there is no substitute for constructing an elevation model that is informed by the terrain.

Hydraulic, physical and rheological characteristics of rain‐triggered lahars at Semeru volcano, Indonesia

AbstractLahars (volcanic debris flows) have been responsible for 40% of all volcanic fatalities over the past century. Mount Semeru (East Java, Indonesia) is a persistently active composite volcano that threatens approximately one million people with its lahars and pyroclastic flows. Despite their regularity, the behaviour and the propagation of these rain‐triggered lahars are poorly understood. In situ samples were taken from lahars in motion at two sites in the Curah Lengkong River, on the southeast flank of Semeru, providing estimates of the particle concentration, grain size spectrum, grain density and composition. This enables us to identify flow sediment from three categories of lahars: (a) hyperconcentrated flow, (b) non‐cohesive, clast‐ and matrix‐supported debris flow, and (c) muddy flood. To understand hyperconcentrated flow sediment transport processes, it is more appropriate to sample the active flows than the post‐event lahar deposits because in situ sampling retains the full spectrum of the grain‐size distribution. Rheometrical tests on materials sampled from moving hyperconcentrated flows were carried out using a laboratory vane rheometer. Despite technical difficulties, results obtained on the <63, <180, and <400 µm fractions of the sampled sediment, suggest a purely frictional behaviour. Importantly, and contrary to previous experiments conducted with monodisperse suspensions, our results do not show any transition towards a viscous behaviour for high shear rates. These data provide important constraints for future physical and numerical modelling of lahar flows. Copyright © 2010 John Wiley & Sons, Ltd.