Relationship between the accumulation of sediment storage and debris-flow characteristics in a debris-flow initiation zone, Ohya landslide body, Japan

Imaizumi, Fumitoshi; Hayakawa, Yuichi S.; Hotta, Norifumi; Tsunetaka, Haruka; Ohsaka, Okihiro; Tsuchiya, Satoshi

doi:10.5194/nhess-17-1923-2017

Cited by 27 publications

(24 citation statements)

References 62 publications

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“…Channel deposits in the Osawa failure had a thickness of up to 10 m in some periods and were also characterized by a high infiltration rate. The ratio of the thickness of the saturated layer to the entire thickness of the deposits is a factor controlling the movement of cohesionless deposits in steep channels because the ratio determines the balance between shear stress and shear strength (Imaizumi et al, 2016(Imaizumi et al, , 2017. A large water supply is needed for the movement of thick deposits.…”

Section: Discussionmentioning

confidence: 99%

“…The time period used to separate different rainfall events (inter-event time definition, IETD) affects the magnitude and accuracy of the rainfall threshold triggering landslides and debris flows (Bezak et al, 2016;Hong et al, 2018). The IETD in previous studies generally ranged from 6 to 24 h; it is affected by catchment size and the available datasets (Guzzetti et al, 2007(Guzzetti et al, , 2008Bezak et al, 2016;Imaizumi et al, 2017). In this study, we compared rainfall thresholds for three different inter-event times (6, 12, and 24 h) to obtain the appropriate IETD in the Osawa failure.…”

Section: Rainfall Monitoringmentioning

confidence: 99%

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Temporal changes in the debris flow threshold under the effects of ground freezing and sediment storage on Mt. Fuji

Imaizumi

Ikeda

Yamamoto³

et al. 2021

Earth Surf. Dynam.

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Abstract. Debris flows are one of the most destructive sediment transport processes in mountainous areas because of their large volume, high velocity, and kinematic energy. Debris flow activity varies over time and is affected by changes in hydrogeomorphic processes in the initiation zone. To clarify temporal changes in debris flow activities in cold regions, the rainfall threshold for the debris flow occurrence was evaluated in Osawa failure at a high elevation on Mt. Fuji, Japan. We conducted field monitoring of the ground temperature near a debris flow initiation zone to estimate the presence or absence of seasonally frozen ground during historical rainfall events. The effects of ground freezing and the accumulation of channel deposits on the rainfall threshold for debris flow occurrence were analyzed using rainfall records and annual changes in the volume of channel deposits since 1969. Statistical analyses showed that the intensity–duration threshold during frozen periods was clearly lower than that during unfrozen periods. A comparison of maximum hourly rainfall intensity and total rainfall also showed that debris flows during frozen periods were triggered by a smaller magnitude of rainfall than during unfrozen periods. Decreases in the infiltration rate due to the formation of frozen ground likely facilitated the generation of overland flow, triggering debris flows. The results suggest that the occurrence of frozen ground and the sediment storage volume need to be monitored and estimated for better debris flow disaster mitigation in cold regions.

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Section: Discussionmentioning

confidence: 99%

Section: Rainfall Monitoringmentioning

confidence: 99%

Temporal changes in the debris flow threshold under the effects of ground freezing and sediment storage on Mt. Fuji

Imaizumi

Ikeda

Yamamoto³

et al. 2021

Earth Surf. Dynam.

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“…Laboratory testing confirms the runoff triggering mechanism at headwater basins (Gregoretti 2000;Tognacca et al 2000;Hu et al 2016;Lanzoni et al 2017). In the Dolomite Alps, DF magnitude depends on sediment availability and the volume of water delivered via convective precipitation (Marchi and D'Agostino 2004;Imaizumi et al 2017). The routing of DFs in the region around Cortina d'Ampezzo is generally contained by incised channels, which end on fans in the valley bottom.…”

Section: Study Areamentioning

confidence: 99%

Observations of the atmospheric electric field preceding intense rainfall events in the Dolomite Alps near Cortina d’Ampezzo, Italy

Bernard

Underwood

Berti

et al. 2019

Meteorol Atmos Phys

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Debris flow events, generated by surface runoff, occur with great frequency in the Dolomites (Northeastern Italian Alps) during the summer season. Summer thunderstorms, which are common in the region, can quickly generate runoff at the base of rocky cliffs, which then entrains and propagates downstream the underlying unconsolidated material. In the past, the main atmospheric feature considered in evaluating the initiation of debris flow events was rainfall. Observations led to the development of rainfall intensity-duration thresholds for sediment mobilization, which compared incoming severe rainfalls with the potential for triggering debris flows. This study works toward the examination of another characteristic of the atmosphere, the atmospheric electric field. In particular, the behavior of the electric field prior to convective rainfall is investigated as an indicator of rainfall intensities capable of triggering debris flows, in a basin near Cortina d'Ampezzo (Italy). Results suggest that prior to bursts of intense rainfall, the electric field derivative frequency distribution exhibits a recurrent pattern roughly half the time. When it occurs, the amplitude of derivative frequency distribution intersects the zero axis twice before rainfall reaches maximum intensity. A regression model is designed which considers the amplitude maximum and the difference in time between the crossings of the zero axis. The validation of this model suggests a mild relationship between electric field and rainfall intensity in an alpine environment.

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“…High-resolution remote sensing technologies have been applied to the investigation of the transport of debris in steep channels and processes occurring on alluvial fans. Multi-temporal laser scanning datasets have been used to investigate changes in channel topography after debris-flows (Scheidl et al, 2008;Oppikofer, 2009;Berger et al, 2011b;Blasone et al, 2014;Imaizumi et al, 2017Imaizumi et al, , 2019Morino et al, 2018). In almost all studies using remote sensing, the methodology of performing change detection has been primarily restricted to digital elevation model (DEM) of difference (DoD).…”

Section: Introductionmentioning

confidence: 99%

Debris-Flow Channel Headwater Dynamics: Examining Channel Recharge Cycles With Terrestrial Laser Scanning

et al. 2022

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Debris-flows present a natural hazard to the safe operation of linear infrastructure in mountainous environments. The most significant contributor to debris-flow occurrence is a supply of readily erodible material, often created by rockfalls and other shallow landslides. The spatial distribution and total volume of storage are also critical factors, controlling the initiation location, predominant flow type, and termination location of debris-flow surges. Therefore, there is a need to be able to systematically incorporate debris recharge processes and timeframes into the monitoring and characterization of debris-flow hazards. In this work, the authors present the results of 7 years of terrestrial laser scanning (TLS) captured at the White Canyon. The White Canyon represents an analog to large scale, steep catchments to investigate the role of sediment supply on debris-flow processes. The TLS dataset was collected at monthly to quarterly intervals, providing a basis for analysis of debris transfer processes occurring on the study slope. A rockfall database of over 72,000 events was generated from 52 change detection analyses and is linked to catchment recharge and transfer processes. The results indicate that the 17 channels analyzed in the White Canyon do not directly match the conceptual models proposed from the supply theory. The channels display a variety of behaviors when exposed to the same climate signature. The temporal data acquisition rate was found to have a significant influence on the dynamics of movement that can be interpreted from TLS change detection analysis. The work highlights the need for higher frequency monitoring and the integration of climate data into the analysis, in order to better understand these dynamic processes.

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Relationship between the accumulation of sediment storage and debris-flow characteristics in a debris-flow initiation zone, Ohya landslide body, Japan

Cited by 27 publications

References 62 publications

Temporal changes in the debris flow threshold under the effects of ground freezing and sediment storage on Mt. Fuji

Temporal changes in the debris flow threshold under the effects of ground freezing and sediment storage on Mt. Fuji

Observations of the atmospheric electric field preceding intense rainfall events in the Dolomite Alps near Cortina d’Ampezzo, Italy

Debris-Flow Channel Headwater Dynamics: Examining Channel Recharge Cycles With Terrestrial Laser Scanning

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