Azioni sul documento

Topic 1 - Debris-flow Occurrence and Initiation

Vai su di un livello
Topic 1 - Debris-flow Occurrence and Initiation
Glacial lake outburst floods (GLOFs) may cause floods of great magnitudes, loss of life, properties and sediment disaster in the downstream river reaches. About 80% of GLOFs (based on 20 cases with known failure mechanisms) were initiated by displacement waves from ice avalanches that collapsed into the lakes from hanging or calving glaciers and rock avalanches. Therefore, an integrated model is essential for the i) prediction of waves generated by ice/rock avalanche, ii) prediction of outflow hydrograph
Topic 1 - Debris-flow Occurrence and Initiation
The study area is the Bonnard glacier which lies in the Anniviers Valley, Valais, Switzerland. Two glacial torrents originate from a source area that is composed of 60% of creeping permafrost which supplies loose material. Heavy rainfall events trigger debris flows on the steep slopes of the lower permafrost complex. Three scarps are visible, two of them from the last event in 2008. In scar n°1 the permafrost plays a key role in triggering debris flow by loading the streambed with unstable materials and cr
Topic 1 - Debris-flow Occurrence and Initiation
In recent years an increase in the prevalence of debris flows has been observed in various regions of the world. These events, which have caused a significant amount of damage to cities, infrastructure and ecosystems; emphasize the importance of developing early warning systems to alert residents of the danger in advance. A model to determine the probability of occurrence of a debris flow through the development of a geographic information system that combines a digital elevation model and a distributed hy
Topic 1 - Debris-flow Occurrence and Initiation
In the August of 2009, Typhoon Morakot brought heavy rainfall and caused several landslides, floods and debris flows in central and southern Taiwan. This work presents the critical rainfall conditions for the initiation of debris flows in the Chen-Yu-Lan watershed of central Taiwan during the action of Typhoon Morakot, where had many severe debris–flows events during the actions of Typhoon Herb in 1996 and Typhoon Toraji in 2001. Thirty-seven debris flow events induced by the heavy rainfalls brought by Ty
Topic 1 - Debris-flow Occurrence and Initiation
Occurrence of debris flows has received little attention in the Pyrenees, probably due to the small risk shown by most of the debris-flow prone sites in this mountain range. Nevertheless, the event of Biescas (which occurred in August 1996 and that caused 87 casualties) demonstrates the existence of high risk spots in the region. Historical data on debris flow occurrence are usually scarce or lacking in the Pyrenees, as in many mountain ranges. This makes difficult the determination of their frequency. Den
Topic 1 - Debris-flow Occurrence and Initiation
In spite of a general agreement on present climate trends, actual impacts on terrestrial systems are still very debated. Evidence is mounting that climate change is affecting the stability of slopes, although the full extent, time, and magnitude of the response remain uncertain, in part because climate is only one of the factors contributing to slope instability. Moreover, at the regional and local scale climate change patterns can be very different. Mountain environment seems to respond promptly to climate
Topic 1 - Debris-flow Occurrence and Initiation
Debris flows in Campania begin as soil slides within the pyroclastic mantle that blankets the steep local hill slopes, which are, in turn, composed largely of carbonate bedrock. The historical pattern appears to be that clusters of debris avalanche-flows occur after intense rainstorms that follow an accumulation of a certain amount of pre-storm seasonal rainfall. Soil moisture appears to show a seasonal pattern of summer drying and winter wetting that is typical for the Mediterranean climate of the region
Topic 1 - Debris-flow Occurrence and Initiation
For the effective protection of the population of the town of Kvareli in Georgia from debris flow formed on the Duruji River, the critical places on the river-bed of Duruji, where overflow of debris flow is possible, were identified. Erosion coefficients of mountain slopes with debris flowing into the basin of Duruji River, which establishes links between the class of erosion and degree of damage of a slope, were explored. Maximum charges on debris flow of river Duruji in different provisions were establis
Topic 1 - Debris-flow Occurrence and Initiation
Landslides affecting on 5-6 May 1998 the towns of Sarno, Quindici, Siano and Bracigliano in Southern Italy represent a case history of great significance both from a scientific and technical point of view. The casualties, the huge economic damage and the severe destruction attracted great attention on the part of the scientific community. Following the landslides, both the national and international scientific community and technicians have given rise to numerous studies in order to provide suitable element
Topic 1 - Debris-flow Occurrence and Initiation
Debris flows are widespread in many steep slopes in northeastern of Tehran province, Iran. The slopes in that region are mostly covered by a relatively thick mantle of weathered debris. Parent rocks mainly consist of vitric tuff and tuffaceous limestone of middle Eocene age. Several factors such as geomorphology, structural geology, tectonics and weathering as well as construction works trigger instability of slop in that area. Among various factors on the formation of debris-flow material, tectonics and we
Topic 1 - Debris-flow Occurrence and Initiation
Generally, debris flow occurs in response to heavy rainfall. The way in which debris flow occurs may be influenced by the conditions of the stream bed deposit, such as its shape, gradient and deformation. In past studies, a hydraulic experiment conducted to analyze debris flow occurrence used a steep flume and uniform gradient, and then some water was supplied to saturate the stream bed deposit before the debris flow was occurred. But in a natural torrent, the riverbed gradient becomes gentler downstream, t
Topic 1 - Debris-flow Occurrence and Initiation
Landslides are one of the most important processes supplying debris fl ow materials into channels. We need to predict the timing, location, and volume of landslides for better estimation of the occurrence of debris fl ows. However, a number of soil parameters (e.g., the angle of internal friction, cohesion, and porosity), which have signifi cant spatial variability, are needed to predict landslide occurrence. Therefore, it is important to make clear the contribution of these parameters to overall slope stab
Topic 1 - Debris-flow Occurrence and Initiation
We attempt to find the unified theory for the prediction of the initiation of debris-flow by using homogenization theory. In this study, we show the leading order solution, which is the first step of this derivation of unified theory. The derivation started in the microscopic scale in the soil. The representative elementary volume (REV) in the soil is set to be one order larger than the scale of porosity. Solids in the REV are assumed to be rigid and adhesion-less. The liquid velocity in the porosity is sl
Topic 1 - Debris-flow Occurrence and Initiation
Rock slope instabilities are implicitly linked to the supply of sediment and debris recharging channels prone to debris flow. Hence, the incorporation of bedrock structure and terrain morphology can be relevant in the analysis of sediment budget and debris flow hazard assessment. Here, the mode of debris production of the Manival catchment (northern French Alps) is documented by the study of its morphostructural aspects extracted from high resolution DEM. Terrain implication in the process of debris supply
Topic 1 - Debris-flow Occurrence and Initiation
Debris flow (DF) phenomena is at the top of the list of dangerous natural hazards in the mountains areas all over the world. Among factors resulting in a DF triggering, meteorological conditions are considered to be the most relevant. The general objective of this study was to identify meteorological parameters controlling the triggering of DF in one part of the French Alps over the last 50 years. Major factors are quite well explored at the global scale or contrariwise in very precise territory in partic
Topic 1 - Debris-flow Occurrence and Initiation
Records derived from trees growing in temperate regions can provide annually resolved data on past debris-flow activity that span several centuries. They therefore allow identification and accurate dating of events prior to instrumental records or missing in historical archives. As a result, dendrogeomorphic methods have repeatedly been used over the last decades to reconstruct debris-flow frequencies in mountain regions of Europe or North America. While these studies furnished valuable data on the minimum
Topic 1 - Debris-flow Occurrence and Initiation
In Taiwan, large and often catastrophic typhoons and earthquakes are both factors to trigger serious landslides in mountains. The presences of large amounts of sediments due to the landslides increase the occurrence of debris flow. Base on post-event data, the threshold of debris flow occurrence decreases soon after an earthquake indicating a fast recovery. A relationship of debris flow occurrence from Egashira (1997) is applied, which shows fine sediment plays an important role with debris-flow development
Topic 1 - Debris-flow Occurrence and Initiation
To assess the spatial pattern of landslide susceptibility, we linked a simple hydrological model and an infinite slope stability model to predict the spatial pattern of critical steady-state rainfall required to cause slope instability. We studied a headwater in the Aratani River basin, western Japan. To clarify soil depth spatial patterns, we measured soil depth on the hillslope by using knocking pole tests. We compared two widely used procedures for determining local slope angle and upslope contributing a
Topic 1 - Debris-flow Occurrence and Initiation
In recent years in Korea, Typhoon Rusa (2002), Typhoon Maemi (2003), and the localized extreme rainfall followed by Typhoon Ewiniar in 2006 devastated residential areas, roads, and agricultural lands in Gangwon province where 90% of the area is in mountainous regions. Most of the economic losses and casualties were concentrated in the area near the mountain valleys and creeks due to the floods and debris flows. In this study, DATABASE, which includes a total 153 debris flow events in the Gangwon area, was
Topic 1 - Debris-flow Occurrence and Initiation
A great amount of mountain hazards were triggered by the Wenchuan earthquake, such as rock falls, avalanches, landslides, debris flows and dammed lakes. Heavy rain on 24th September 2008 initiated debris flows in Weijia Gully of Beichuan County, which resulted in serious damage to infrastructures and lifelines. In this paper, the debris flow was investigated and analyzed. The results show that solid loose materials, microtopography and rainfall are the main reason for the event. The total loose mass generat
Topic 1 - Debris-flow Occurrence and Initiation
Natural hazards occur more frequently due to ongoing global climate change, which has increased the impact of precipitation. Debris flows and their relative activities have also changed over the past 39 years at Jiangjia Gully, a typical debris flow valley with high-frequency debris flows located in the Yunnan Province of China. This paper concentrates on the responses of sediment transportation induced by debris flows at Jiangjia Gully to rainfall change, using statistical analysis of the observation data
Statistics