scholarly journals Distinguishing between debris flows and floods from field evidence in small watersheds

Fact Sheet ◽  
2005 ◽  
Author(s):  
Thomas C. Pierson
Keyword(s):  
Debris Flows ◽  
Small Watersheds ◽  
Field Evidence

scholarly journals Earthquake-induced debris flows at Popocatépetl Volcano, Mexico

2021 ◽  
Vol 9 (3) ◽  
pp. 393-412
Author(s):  
Velio Coviello ◽  
Lucia Capra ◽  
Gianluca Norini ◽  
Norma Dávila ◽  
Dolors Ferrés ◽  
...  
Keyword(s):  
Debris Flows ◽  
Active Volcano ◽  
Horizontal Stress ◽  
Structural Features ◽  
Joint Effect ◽  
Volcanic Edifice ◽  
Field Evidence ◽  
Intraslab Earthquake ◽  
Popocatépetl Volcano ◽  
Popocatepetl Volcano

Abstract. The 2017 Mw 7.1 Puebla–Morelos intraslab earthquake (depth: 57 km) severely hit Popocatépetl Volcano, located ∼ 70 km north of the epicenter. The seismic shaking triggered shallow landslides on the volcanic edifice, mobilizing slope material saturated by the 3 d antecedent rainfall. We produced a landslide map based on a semi-automatic classification of a 50 cm resolution optical image acquired 2 months after the earthquake. We identified hundreds of soil slips and three large debris flows for a total affected area of 3.8 km2. Landslide distribution appears controlled by the joint effect of slope material properties and topographic amplification. In most cases, the sliding surfaces correspond with discontinuities between pumice-fall and massive ash-fall deposits from late Holocene eruptions. The largest landslides occurred on the slopes of aligned ENE–WSW-trending ravines, on opposite sides of the volcano, roughly parallel to the regional maximum horizontal stress and to volcano-tectonic structural features. This suggests transient reactivation of local faults and extensional fractures as one of the mechanisms that weakened the volcanic edifice and promoted the largest slope failures. The material involved in the larger landslides transformed into three large debris flows due to liquefaction. These debris flows mobilized a total volume of about 106 m3 of material also including large wood, were highly viscous, and propagated up to 7.7 km from the initiation areas. We reconstructed this mass wasting cascade by means of field evidence, samples from both landslide scarps and deposits, and analysis of remotely sensed and rainfall data. Although subduction-related earthquakes are known to produce a smaller number of landslides than shallow crustal earthquakes, the processes described here show how an unusual intraslab earthquake can produce an exceptional impact on an active volcano. This scenario, not related to the magmatic activity of the volcano, should be considered in multi-hazard risk assessment at Popocatépetl and other active volcanoes located along volcanic arcs.

Magnetic and pebble fabrics of glaciomarine diamictons in the Champlain Sea, Ontario, Canada

1985 ◽  
Vol 22 (3) ◽  
pp. 422-434 ◽  
Author(s):  
C. P. Gravenor
Keyword(s):  
Debris Flows ◽  
Magnetic Particles ◽  
Magnetic Fabric ◽  
Dual Approach ◽  
The Third ◽  
Magnetic Fabrics ◽  
Field Evidence ◽  
The Matrix

Glaciomarine diamicton(ite)s that contain articulated unbroken shell remains are usually assumed to have been deposited by the settling out of suspended mud with additions of coarse clasts derived from the melting of debris-laden floating ice. However, little is known about the magnetic and pebble fabrics of these composite sediments, and the purpose of this study is to describe and interpret the magnetic and pebble fabrics of fossiliferous glaciomarine diamictons found at three locations in the Champlain Sea, Ontario.At two of the three sites examined it is found that the long axes of the prolate and blade-shaped pebbles do not show well defined alignments, but they are not randomly distributed in either the horizontal or vertical planes. This observation and an analysis of the alignment of the magnetic particles in the matrix of the diamictons show that the diamictons have undergone syn- or post-depositional movement and fall into the category of glaciogenic subaquatic debris flows. At the third site the diamictons are stratified, and the magnetic fabric and field evidence show that post-depositional movement was caused by loading of sand layers into underlying muds.The results suggest that magnetic fabrics can be useful in interpreting pebble fabrics and that the dual approach may help to differentiate various types of glaciomarine diamicton(ite)s.

scholarly journals Comparison of spatial modelling and field evidence of glacier/permafrost relations in an Alpine permafrost environment

2000 ◽  
Vol 31 ◽  
pp. 269-274 ◽  
Author(s):  
Christof Kneisel ◽  
Wilfried Haeberli ◽  
Roland Baumhauer
Keyword(s):  
Debris Flows ◽  
Field Measurements ◽  
Spatial Modelling ◽  
Swiss Alps ◽  
Ground Ice ◽  
Glacier Forefield ◽  
Geomorphological Mapping ◽  
Field Evidence ◽  
Winter Snow ◽  
Permafrost Environment

AbstractAccording to geographic information system-based modelling, the Muragl glacier forefield situated in the St Moritz area, eastern Swiss Alps, lies in a potential permafrost area. As an attempt to verify spatial modelling, BTS (bottom temperature of the winter snow cover) measurements, geoelectrical soundings and geomorphological mapping were carried out in order to investigate the present-day permafrost and ground-ice distribution in this forefield. Recent geomorphodynamic processes in the steep upper slopes of the cirque include small debris flows and several slides related to the occurrence of ground ice. The occurrence of fluted moraines and a well-developed push moraine provides geomorphological evidence for a complex thermal regime of the former Muragl glacier, with cold marginal parts frozen to the bed, and warm-based ice in more central parts where fluted moraines could develop. Details of the inferred glacier/permafrost interaction are difficult to interpret. The results of field measurements (BTS and geoelectrical soundings) in the recently deglaciated forefield indicate the local occurrence of permafrost in the forefield and in the push moraine. In most parts of the forefield, permafrost may be assumed to be a former subglacial occurrence. However, new permafrost formation in the recently deglaciated forefield cannot be excluded.

scholarly journals Assessment and Analysis of a Rainfall–Time-Lagging Water-Related Disaster in Mountainous Areas

2021 ◽  
Vol 9 ◽  
Author(s):  
Xu-Feng Yan ◽  
Hui Xu ◽  
Heng Lu ◽  
Jia-Wen Zhou ◽  
Xie-Kang Wang ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Global Climate ◽  
Integrated Analysis ◽  
Small Scale ◽  
Mountainous Areas ◽  
Triggering Mechanism ◽  
Water Release ◽  
Field Evidence

Both global climate change and human activities are continuously impacting the abruptness and frequency of water-related natural disasters such as flash floods, debris flows, and landslides in mountainous areas, greatly threatening the safety of lives and properties. A recent rainfall-induced debris flow event happened on July 6, 2020 in the Chenghuangmiao Gully, in Sichuan Province, China, resulting in severe damage to buildings at the outlet. An integrated analysis of the consequence and triggering mechanism of this debris flow event was conducted with hydrologic information, topographic details, vegetation regimes, and drone aerial imagery. The result shows that the entire runout of the debris flow differs from that of common ones (debris flow and rainfall were highly related and synchronized), which happened 4 h after the stop of the rainfall. The hysteretic feature increases the difficulty of the prediction and warning of the debris flow due to lack of a responsible triggering mechanism. The hillslope surface is well covered by vegetation, hindering regular observation and cleaning up of long-term deposited wood and sediment debris. This effect increases the crypticity and abruptness of potential debris flows. With field evidence and analysis, it is speculated that long-term accumulative processes of dead wood sand sediment deposition formed a small-scale debris dam, and the continuous water release from the watershed led to dam breaching, subsequently triggering the initiation of the debris flow. Multiple steps distributing along the gully of an average slope of 15.65° contributed to the amplification of the debris flow once the breach of the upstream wood and sediment dam occurred. Along the gully, small-scale landslide scars can be observed, possibly amplifying the scale of the debris flow and disaster impact. This debris event gives a lesson of necessary demands of predicting and managing the risks of a low-frequency debris flow non-synchronized with rainfall events.

Susceptibility Forecast of Geo-Hazard under the Conditions of Earthquake and Rainfall

2013 ◽  
Vol 353-356 ◽  
pp. 1219-1222
Author(s):  
Shu Jun Tian ◽  
Ji Ming Kong
Keyword(s):  
High Risk ◽  
Wenchuan Earthquake ◽  
Debris Flows ◽  
Influence Factors ◽  
Field Investigation ◽  
Forecast System ◽  
Seismic Fault ◽  
Small Watersheds ◽  
Loose Deposits ◽  
Risk Grade

Large amount of loose deposits and potential geo-hazards were formed by Wenchuan earthquake, which would be transformed into collapses, landslide and debris flows under the condition of rainfall or aftershock. The paper divides influence factors into triggering factors and background factors, and constitutes susceptibility forecast system for geo-hazard based on factors in parallel or series. The background system contains stratum, distance to river, relief, slope and aspect of slope. And the triggering system includes distance to seismic fault and rainfall. The paper applies and verifies the system to forecast the susceptibility of geo-hazard in study area, and the result shows that 52 small watersheds are in extremely high and high states accounting for 37.68% in 138 small watersheds. According to the statistics of 23 geo-hazards from field investigation, 13 geo-hazards are in extremely high risk grade of susceptibility and 10 geo-hazards are in high risk grade of susceptibility, which shows that the result of susceptibility forecast of geo-hazard is reasonable.

scholarly journals Field evidence suggests that the Palaeoproterozoic Gowganda Formation in Canada is non-glacial in origin

Geologos ◽  
2021 ◽  
Vol 27 (2) ◽  
pp. 73-91
Author(s):  
Mats O. Molén
Keyword(s):  
Recent Work ◽  
Debris Flows ◽  
Gravity Flow ◽  
Geological Evidence ◽  
Field Evidence ◽  
Gravity Flows ◽  
Geological Features

Abstract During more than a century since its original identification, the Gowganda Formation in Ontario (Canada) has gradually been reinterpreted from representing mainly subglacial tillites to secondary gravity flow and glaciomarine deposits. The main pieces of geological evidence advanced in favour of glaciation in recent articles are outsized clasts that have been interpreted as dropstones and patches of diamictites in a single small-sized area at Cobalt which is still interpreted as displaying subglacial basal tillites. The present research considers field evidence in the Gowganda Formation in the light of more recent work on gravity flows linked to tectonics. Detailed studies have demonstrated that the clasts which are interpreted to be dropstones rarely penetrate laminae and are commonly draped by sediments the appearance of which is similar to lonestones in gravity flows. The “subglacial area” at Cobalt displays evidence of tectonics and gravity flows, which can be traced from the underlying bedrock, and then further in the overlying sequence of diamictites and rhythmites. The sum of geological features displays appearances at odds with a primary glaciogenic origin, and there is no unequivocal evidence present of glaciation. The data indicate deposition by non-glaciogenic gravity flows, including cohesive debris flows for the more compact units, probably triggered by tectonic displacements.

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