Paraglacial Cirque Headwall Instability - Regional Scale Assessment Of Preconditioning Factors

2020 ◽  
Author(s):  
Andreas Ewald ◽  
Jan-Christoph Otto
Keyword(s):  
Rock Mass ◽  
Rock Slope ◽  
Regional Scale ◽  
Regional Analysis ◽  
Slope Instability ◽  
Geotechnical Data ◽  
Systematic Assessment ◽  
Slope Inclination ◽  
First Results ◽  
Elevation Model

<p>Cirques are characteristic landforms in high alpine environments with flat cirque floors flanked by steep headwalls. From a rock-mechanical perspective, rock walls are assumed to adjust over time according to their internal rock mass strength, which is determined by a number of factors including e. g. intact rock strength and fracture system characteristics. However, temperatures permanently below freezing as well as glacier coverage keep cirque headwalls stabilised so that slope inclination can evolve during glaciation that is far beyond strength equilibrium. When cirque headwalls deglaciate, the relative importance of rock mass properties increases drastically as they precondition rock slope instability. Cataclinal headwalls, where major fracture sets dip out of the slope, are rated as unstable and usually respond rapidly to glacier retreat. Anaclinal headwalls with in-dipping fracture sets in contrast respond delayed and probably less drastically. To date, a systematic assessment of the predisposition of cirque headwalls for rock slope instability following deglaciation is lacking. We aim to tackle this lacking by a systematic regional analysis of predisposition factors using GIS tools.</p><p> </p><p>For the central Hohe Tauern Range, Austria, regional datasets are available for the most important preconditioning factors including topography (digital elevation model), geology (digital geological map), glacier extent (digital glacier inventory), and permafrost distribution (PERMAKART 3.0). We combined geomorphometric analyses with geotechnical data to locate and evaluate the sensitivity of glacier headwalls to rock slope instability using GIS and object-based analysis techniques.</p><p> </p><p>Our results show that a vast majority of the headwalls identified can be divided by a significant convexity in the slope profile curvature into a larger, upper and a lower, steeper headwall section (> 60°). The lower limit of the steeper section is marked by a significant concavity in the slope profile curvature, which is commonly known as the schrundline. Assuming that the convex transition between steeper and flatter headwall section constitutes the upper limit of enhanced headwall retreat e. g. by periglacial weathering inside the bergschrund, we further address this headwall section as the schrundwall.</p><p> </p><p>Geotechnical data (foliation dip and direction) has been digitalised and interpolated in a yet oversimplified manner, to distinguish  headwalls into cataclinal, anaclinal and orthoclinal slopes. Slope inclination and foliation dip has been interrelated to identify e. g. particularly sensitive overdip slopes. First results show that anaclinal and orthoclinal as well as cataclinal headwalls are quite common features in the study area. However, overdip slopes with steeply (30°-60°) outdipping foliation are almost exclusively found in schrundwall sections.</p><p> </p><p>The persistence of steep overdip schrundwalls may be related to permafrost occurrence, which is subject to further analysis. Our approach, applied to modeled subglacial topography, may be of great value to anticipate future paraglacial instabilities in glacier headwalls.</p>

scholarly journals Assessment of Slope Instability and Risk Analysis of Road Cut Slopes in Lashotor Pass, Iran

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Mohammad Hossein Taherynia ◽  
Mojtaba Mohammadi ◽  
Rasoul Ajalloeian
Keyword(s):  
Rock Mass ◽  
Risk Analysis ◽  
Rock Slope ◽  
Classification Systems ◽  
Slope Instability ◽  
Rock Slope Stability ◽  
Rock Slopes ◽  
The Stability ◽  
Cut Slopes ◽  
Road Cut Slopes

Assessment of the stability of natural and artificial rock slopes is an important topic in the rock mechanics sciences. One of the most widely used methods for this purpose is the classification of the slope rock mass. In the recent decades, several rock slope classification systems are presented by many researchers. Each one of these rock mass classification systems uses different parameters and rating systems. These differences are due to the diversity of affecting parameters and the degree of influence on the rock slope stability. Another important point in rock slope stability is appraisal hazard and risk analysis. In the risk analysis, the degree of danger of rock slope instability is determined. The Lashotor pass is located in the Shiraz-Isfahan highway in Iran. Field surveys indicate that there are high potentialities of instability in the road cut slopes of the Lashotor pass. In the current paper, the stability of the rock slopes in the Lashotor pass is studied comprehensively with different classification methods. For risk analyses, we estimated dangerous area by use of the RocFall software. Furthermore, the dangers of falling rocks for the vehicles passing the Lashotor pass are estimated according to rockfall hazard rating system.

scholarly journals Observation of the rock slope thermal regime, coupled with crack meter stability monitoring

2021 ◽  
Author(s):  
Ondřej Racek ◽  
Jan Blahůt ◽  
Filip Hartvich
Keyword(s):  
Rock Mass ◽  
Monitoring System ◽  
Rock Slope ◽  
Global Radiation ◽  
Environmental Parameters ◽  
Radiation Balance ◽  
Rock Types ◽  
Novel Approach ◽  
First Results

Abstract. This article describes an innovative, complex and affordable monitoring system designed for joint observation of environmental parameters, rock block dilatations and temperature distribution inside the rock mass with a newly designed 3-meter borehole temperature sensor. Global radiation balance data are provided by pyranometers. The system introduces a novel approach for internal rock mass temperature measurement, which is crucial for the assessment of the changes in the stress field inside the rock slope influencing its stability. The innovative approach uses an almost identical monitoring system at different sites allowing easy setup, modularity and comparison of results. The components of the monitoring system are cheap, off-the-shelf and easy to replace. Using this newly designed system, we are currently monitoring three different sites, where the potential rock fall may endanger society assets below. The first results show differences between instrumented sites, although data time-series are relatively short. Temperature run inside the rock mass differs for each site significantly. This is very likely caused by different aspects of the rock slopes and different rock types. By further monitoring and data processing, using advanced modelling approaches, we expect to explain the differences among the sites, the influence of rock type, aspect and environmental variables on the long-term slope stability.

scholarly journals Unraveling spatial and temporal heterogeneities of very slow rock-slope deformations with targeted DInSAR analyses

2021 ◽  
Author(s):  
Federico Franzosi ◽  
Chiara Crippa ◽  
Mattia Zonca ◽  
Andrea Manconi ◽  
Giovanni B. Crosta ◽  
...  
Keyword(s):  
Rock Slope ◽  
Regional Scale ◽  
Temporal Trends ◽  
Structural Data ◽  
Local Scale ◽  
Slope Deformation ◽  
Slope Instability ◽  
Gps Data ◽  
Multi Temporal

<p>Spaceborne radar interferometry is a powerful tool to characterize landslide activity. However, its application to very slow rock slope deformations (displacement rates < 5 cm/yr) in alpine environments remains challenging due to low signal-to-noise ratio, severe atmospheric and snow cover effects, and heterogeneous deformation patterns related to complex landslide mechanisms in space and time.</p><p>In this study we combine available SqueeSAR<sup>TM</sup> data (Sentinel 1A/B ascending and descending, 2015-2017), ad hoc multi-temporal baseline DInSAR processing (2016-2019), GPS data (2015 to 2019) and detailed field mapping to unravel the kinematics, internal segmentation and style of activity of the Mt. Mater deep-seated gravitational slope deformation (DSGSD) in Valle Spluga (Italy). The high relief slope (1500-3000 m.a.s.l.) is made of dominant micaschist and paragneiss of the Stella-Timun complex (Suretta nappe) and ranges in inclination between 33° (< 2500 m a.s.l.) and 25° (> 2500 m a.s.l.). At 2900 m a.s.l. the slope is cut by a sharp triangular headscarp with a vertical downthrow of about 40 m, moving downslope, shallower arcuate scarps mark the transition to two nested large landslides, affecting the slope between 2400 m a.s.l. and 1550 m a.s.l; with highly deformed toes.</p><p>Through 2DInSAR decomposition, we highlight the global translational kinematics of the DSGSD. However, regional scale processed PSI data result unsuitable to capture the spatial complexity of the phenomenon at the local scale. To obtain a spatially-distributed characterization of the DSGSD displacement patterns, we process several multi-temporal interferograms and retrieve unwrapped phase and displacement maps according to a process-oriented, targeted approach based on variable temporal baselines (from 24-days to 1-year). In this context: a) 1-year interferograms provide a picture of long-term background DSGSD displacement signals; b) seasonal interferograms highlight displacement trends suggesting a complex response of different slope sectors to hydrological input; c) 24 days interferograms outline a triangular shaped active sector extending between 2500 m a.s.l. and the main DSGSD headscarp, corresponding to the movement of extensive debris cover and overlying periglacial features.</p><p>Our analyses clearly outline a composite slope instability and a strong spatial heterogeneity with different nested sectors possibly undergoing different evolutionary trends towards failure. The combined analysis of seasonal interferograms and GPS data further confirm a sensitivity of the different slope sectors to hydrological forcing modulated by snowmelt and rainfalls. The herein results outline the potential of a targeted use of DInSAR, carefully constrained by field geological and morpho-structural data, for the detailed investigation of a complex very slow rock slope deformation successfully unravelling its mechanisms, temporal trends of activity and forcing factors. Ground-truthing by means of GPS data further prove that, in the context of very slow rock deformations, PSI data are useful for a first-order characterization of slope activity and kinematics, but often fail to capture local scale spatial segmentation, temporal trends and associated mechanisms.</p><p>Our approach prove to be effective in providing key information for the definition of possible evolutive scenarios for risk analysis and mitigation of a widespread, yet challenging class of slope instabilities.</p>

scholarly journals A New Approach for Identification of Potential Rockfall Source Areas Controlled by Rock Mass Strength at a Regional Scale

2021 ◽  
Vol 13 (5) ◽  
pp. 938
Author(s):  
Xueliang Wang ◽  
Haiyang Liu ◽  
Juanjuan Sun
Keyword(s):  
Rock Mass ◽  
Digital Elevation Model ◽  
Regional Scale ◽  
Slope Angle ◽  
New Approach ◽  
Rock Mass Strength ◽  
Source Areas ◽  
Space Partition ◽  
Digital Elevation ◽  
Elevation Model

The identification of rockfall source areas is a fundamental work for rockfall disaster prevention and mitigation. Based on the Culmann model, a pair of important indicators to estimate the state of slope stability is the relief and slope angles. Considering the limit of field survey and the increasing requirements for identification over a large area, a new approach using the relief–slope angle relationship to identify rockfall source areas controlled by rock mass strength at a regional scale is proposed in this paper. Using data from helicopter-based remote sensing imagery, a digital elevation model of 10 m resolution, and field work, historical rockfalls in the Wolong study area of Tibet where frequent rockfalls occur are identified. A clear inverse relationship between the relief and slope angles of historical rockfalls enables us to calculate the rock mass strength of the landscape scale by the Culmann model and the relief–slope angle relationship curve. Other parameters used in our proposed approach are calculated by ArcGIS and statistic tools. By applying our approach, the potential rockfall source areas in the study are identified and further zoned into three susceptibility classes that could be used as a reference for a regional rockfall susceptibility study. Using the space partition of historical rockfall inventory, our prediction result is validated. Most of the rockfall source areas (i.e., 71.92%) identified in the validation area are occupied by historical rockfalls, which proves the good prediction of our approach. The dominant uncertainty in this paper is derived from the process of calculating rock mass strength, defining the specific area for searching potential rockfall source areas, and the resolution of the digital elevation model.

2020 hurricane impact assessment for the northern Gulf of Mexico: Hurricane Sally and Hurricane Zeta

Shore & Beach ◽  
2021 ◽  
pp. 56-64
Author(s):  
S. McGill ◽  
C. Sylvester ◽  
L. Dunkin ◽  
E. Eisemann ◽  
J. Wozencraft
Keyword(s):  
Change Detection ◽  
Gulf Coast ◽  
Regional Scale ◽  
Shoreline Change ◽  
Airborne Lidar ◽  
Digital Elevation ◽  
The Status ◽  
Northern Gulf Coast ◽  
Elevation Model ◽  
Beach Volume

Regional-scale shoreline and beach volume changes are quantified using the Joint Airborne Lidar Bathymetry Technical Center of Expertise’s digital elevation model products in a change detection framework following the passage of the two landfalling hurricanes, Hurricanes Sally and Zeta, along the northern Gulf Coast in late fall 2020. Results derived from this work include elevation change raster products and a standard set of beach volume and shoreline change metrics. The rapid turn-around and delivery of data products to include volume and shoreline change assessments provide valuable information about the status of the coastline and identification of areas of significant erosion or other impacts, such as breaching near Perdido Key, FL, from Hurricane Sally’s impact. These advanced change detection products help inform sediment budget development and support decisions related to regional sediment management and coastal storm risk management.

scholarly journals Drivers of Change in National Disaster Governance under the Hyogo Framework for Action

2020 ◽  
Vol 8 (4) ◽  
pp. 256-269 ◽  
Author(s):  
Maximilian S. T. Wanner
Keyword(s):  
Natural Hazard ◽  
National Level ◽  
Development Aid ◽  
Small Scale ◽  
Substantial Variation ◽  
Drivers Of Change ◽  
Governance Capacity ◽  
Systematic Assessment ◽  
First Results ◽  
National Disaster

Many suggestions have been made on what motivates countries to expand their measures for disaster risk reduction (DRR), including the frequency and severity of natural hazards, accountability mechanisms, and governance capacity. Despite the fact that theoretical arguments have been developed and evidence collected from small-scale case studies, few studies have attempted to explain the substantial variation in the adoption of DRR measures across countries. This study combines available data on DRR measures, natural hazard events, governance, and socioeconomic characteristics to provide a systematic assessment of the changes that have occurred in the state of DRR at the national level. In line with theoretical explanations, there are indeed associations between several measures of frequency and severity and the development of DRR status. Additionally, voice and accountability mechanisms, as well as development aid, might facilitate positive change. Although these first results of a global comparative study on change in DRR have to be taken cautiously, it is a step forward to understanding the drivers of change at the national level.

scholarly journals Chasing a hidden fracture using seismic refraction tomography: case study Preonzo, Switzerland

2020 ◽  
Author(s):  
Mauro Häusler ◽  
Franziska Glüer ◽  
Jan Burjánek ◽  
Donat Fäh
Keyword(s):  
Rock Mass ◽  
Seismic Refraction ◽  
Slope Instability ◽  
Mode Analysis ◽  
Mode Shapes ◽  
Small Aperture ◽  
Higher Modes ◽  
Refraction Tomography ◽  
Tension Cracks ◽  
Unstable Rock

<p>The Preonzo rock slope instability in southern Switzerland partly collapsed in 2012, releasing a volume of ~210’000 m3 and leaving behind an unstable rock mass of about 140’000 m3. Shortly after the collapse, a small-aperture seismic array measurement was performed on the remaining unstable volume. The analysis of these data showed a fundamental resonance frequency of about 3.5 Hz and strong wavefield amplifications with factors of more than 30 in direction perpendicular to open tension cracks. Normal mode analysis by frequency domain decomposition using the fundamental and several higher modes allowed for mapping the fracture network of the instability.<br>However, the observed amplification factors and mode shapes could not be explained solely by the open tension cracks visible at the surface. Strong amplifications, especially at frequencies of higher modes, were observed on the uphill part of the rear fracture, which was supposed to be outside the presumed unstable area. The zone where amplifications rapidly decreased in the uphill direction coincides roughly with a geomorphological lineament in the field, interpreted as an additional, but hidden, rear fracture. <br>We performed active seismic refraction tomography across this lineament and discovered distinct low velocity anomalies in the transition zone from high to low amplifications, supporting the interpretation of an additional fracture. Considering this new finding, the volume of the unstable rock mass increases by about 40 %. </p>

Why the future of rock mass classification systems requires revisiting their empirical past

2021 ◽  
pp. qjegh2021-039
Author(s):  
Beverly Yang ◽  
Amichai Mitelman ◽  
Davide Elmo ◽  
Doug Stead
Keyword(s):  
Rock Mass ◽  
Rock Mass Classification ◽  
Classification Systems ◽  
Empirical Knowledge ◽  
Rock Engineering ◽  
Geotechnical Data ◽  
Use Of Technology ◽  
Data Collection Process ◽  
Engineering Problems ◽  
Mass Classification

Despite recent efforts, digitisation in rock engineering still suffers from the difficulty in standardising and statistically analysing databases that are created by a process of quantification of qualitative assessments. Indeed, neither digitisation nor digitalisation have to date been used to drive changes to the principles upon which, for example, the geotechnical data collection process is founded, some of which have not changed in several decades. There is an empirical knowledge gap which cannot be bridged by the use of technology alone. In this context, this paper presents the results of what the authors call a rediscovery of rock mass classification systems, and a critical review of their definitions and limitations in helping engineers to integrate these methods and digital acquisition systems. This discussion has significant implications for the use of technology as a tool to directly determine rock mass classification ratings and for the application of machine learning to address rock engineering problems.

scholarly journals Aveiro Canyon Head (Portugal) Submarine Slope Instability Assessment

2020 ◽  
Vol 10 (24) ◽  
pp. 9038
Author(s):  
Nuno Lapa ◽  
Fernando M. F. S. Marques ◽  
Aurora Rodrigues
Keyword(s):  
Marine Environment ◽  
Regional Scale ◽  
Slope Angle ◽  
Area Under The Curve ◽  
Roc Curves ◽  
Information Value ◽  
Slope Instability ◽  
Landslide Inventory ◽  
Spatial And Temporal Variability ◽  
Sedimentary Dynamics

Mass wasting events are the main processes of sedimentary dynamics that affect the marine environment and which, due to their spatial and temporal variability, are difficult to study and evaluate. Affecting the marine floor, between the coastline and the abyssal plain, these processes are triggered by multiple causes, having different magnitudes and causing drastic changes and impacts on the marine environment and human activities. In this paper, the submarine landslide susceptibility affecting the upper course of the Aveiro canyon (West Iberian Margin) is addressed using statistical models which are based on the statistical relations between a landslide inventory and the landslide predisposing factors bathymetry, sediment cover, slope angle, aspect and curvature. The statistical methods were the widely proven bivariate information value (IV) and the multivariate logistic regression (LR). The model results were validated against the landslide inventory using receiver operating characteristic (ROC) curves and the corresponding area under the curve (AUC), which provided satisfactory results, with IV AUC = 0.79 and LR AUC = 0.83, in spite of the limitations of the databases used in this study. The results obtained suggest that these methods may be useful for the preliminary assessment of sea floor slope instability at a regional scale of analysis, enabling the selection of sites to be studied with much more detailed and expensive methods.

scholarly journals Evaluation of the Vertical Accuracy of Open Global DEMs over Steep Terrain Regions Using ICESat Data: A Case Study over Hunan Province, China

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4865 ◽  
Author(s):  
Zhiwei Liu ◽  
Jianjun Zhu ◽  
Haiqiang Fu ◽  
Cui Zhou ◽  
Tingying Zuo
Keyword(s):  
Land Cover ◽  
Regional Scale ◽  
Morphological Characteristics ◽  
Hunan Province ◽  
South Central ◽  
Vertical Accuracy ◽  
Dem Accuracy ◽  
Elevation Model ◽  
Terrain Elevation

The global digital elevation model (DEM) is important for various scientific applications. With the recently released TanDEM-X 90-m DEM and AW3D30 version 2.2, the open global or near-global coverage DEM datasets have been further expanded. However, the quality of these DEMs has not yet been fully characterized, especially in the application for regional scale studies. In this study, we assess the quality of five freely available global DEM datasets (SRTM-1 DEM, SRTM-3 DEM, ASTER GDEM2, AW3D30 DEM and TanDEM-X 90-m DEM) and one 30-m resampled TanDEM-X DEM (hereafter called TDX30) over the south-central Chinese province of Hunan. Then, the newly-released high precision ICESat-2 (Ice, Cloud, and land Elevation Satellite-2) altimetry points are introduced to evaluate the accuracy of these DEMs. Results show that the SRTM1 DEM offers the best quality with a Root Mean Square Error (RMSE) of 8.0 m, and ASTER GDEM2 has the worst quality with the RMSE of 10.1 m. We also compared the vertical accuracies of these DEMs with respect to different terrain morphological characteristics (e.g., elevation, slope and aspect) and land cover types. It reveals that the DEM accuracy decreases when the terrain elevation and slope value increase, whereas no relationship was found between DEM error and terrain aspect. Furthermore, the results show that the accuracy increases as the land cover type changes from vegetated to non-vegetated. Overall, the SRTM1 DEM, with high spatial resolution and high vertical accuracy, is currently the most promising dataset among these DEMs and it could, therefore, be utilized for the studies and applications requiring accurate DEMs.

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