Identification of potential rockfall source areas at a regional scale using a DEM-based geomorphometric analysis

Abstract. The availability of high resolution Digital Elevation Models (DEM) at a regional scale enables the analysis of topography with high levels of detail. Hence, a DEM-based geomorphometric approach becomes more accurate for detecting potential rockfall sources. Potential rockfall source areas are identified according to the slope angle distribution deduced from high resolution DEM crossed with other information extracted from geological and topographic maps in GIS format. The slope angle distribution can be decomposed in several Gaussian distributions that can be considered as characteristic of morphological units: rock cliffs, steep slopes, footslopes and plains. A terrain is considered as potential rockfall sources when their slope angles lie over an angle threshold, which is defined where the Gaussian distribution of the morphological unit "Rock cliffs" become dominant over the one of "Steep slopes". In addition to this analysis, the cliff outcrops indicated by the topographic maps were added. They contain however "flat areas", so that only the slope angles values above the mode of the Gaussian distribution of the morphological unit "Steep slopes" were considered. An application of this method is presented over the entire Canton of Vaud (3200 km2), Switzerland. The results were compared with rockfall sources observed on the field and orthophotos analysis in order to validate the method. Finally, the influence of the cell size of the DEM is inspected by applying the methodology over six different DEM resolutions.

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Rockfall hazard and risk assessments along roads at a regional scale: example in Swiss Alps

Natural Hazards and Earth System Science ◽

10.5194/nhess-12-615-2012 ◽

2012 ◽

Vol 12 (3) ◽

pp. 615-629 ◽

Cited By ~ 70

Author(s):

C. Michoud ◽

M.-H. Derron ◽

P. Horton ◽

M. Jaboyedoff ◽

F.-J. Baillifard ◽

...

Keyword(s):

Rock Mass ◽

Regional Scale ◽

Slope Angle ◽

Swiss Alps ◽

Cumulative Distribution ◽

Angle Distribution ◽

Source Areas ◽

Hazard And Risk ◽

Mass Failure ◽

Rock Mass Failure

Abstract. Unlike fragmental rockfall runout assessments, there are only few robust methods to quantify rock-mass-failure susceptibilities at regional scale. A detailed slope angle analysis of recent Digital Elevation Models (DEM) can be used to detect potential rockfall source areas, thanks to the Slope Angle Distribution procedure. However, this method does not provide any information on block-release frequencies inside identified areas. The present paper adds to the Slope Angle Distribution of cliffs unit its normalized cumulative distribution function. This improvement is assimilated to a quantitative weighting of slope angles, introducing rock-mass-failure susceptibilities inside rockfall source areas previously detected. Then rockfall runout assessment is performed using the GIS- and process-based software Flow-R, providing relative frequencies for runout. Thus, taking into consideration both susceptibility results, this approach can be used to establish, after calibration, hazard and risk maps at regional scale. As an example, a risk analysis of vehicle traffic exposed to rockfalls is performed along the main roads of the Swiss alpine valley of Bagnes.

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

Remote Sensing ◽

10.3390/rs13050938 ◽

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.

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Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100077268 ◽

1983 ◽

Vol 41 ◽

pp. 738-739

Author(s):

W. H. Wu ◽

R. M. Glaeser

Keyword(s):

Electron Microscopy ◽

Surface Layer ◽

Structural Analysis ◽

High Resolution ◽

Low Dose ◽

High Resolution Electron Microscopy ◽

Optical Diffraction ◽

Surface Layer Protein ◽

Morphological Unit ◽

Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

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Probabilistic identification of rockfall source areas at regional scale in El Hierro (Canary Islands, Spain)

Geomorphology ◽

10.1016/j.geomorph.2021.107661 ◽

2021 ◽

Vol 381 ◽

pp. 107661

Author(s):

Mauro Rossi ◽

Roberto Sarro ◽

Paola Reichenbach ◽

Rosa María Mateos

Keyword(s):

Canary Islands ◽

Regional Scale ◽

Source Areas ◽

El Hierro

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Application of high resolution airborne geophysics to epithermal gold exploration in Northeast Queensland and Coromandel, New Zealand

Exploration Geophysics ◽

10.1071/eg989099 ◽

1989 ◽

Vol 20 (2) ◽

pp. 99 ◽

Cited By ~ 1

Author(s):

S.S. Webster ◽

R.W. Henley

Keyword(s):

High Resolution ◽

Regional Scale ◽

Cost Effective ◽

Gold Deposits ◽

Ore Deposits ◽

Magnetic Data ◽

Mapping Technique ◽

Epithermal Gold ◽

Airborne Geophysics ◽

Airborne Geophysical Data

High resolution airborne geophysical data over broad areas have been found to optimize exploration for epithermal gold deposits in differing geological environments.Genetic exploration models may be tested in favourable sites by the recognition of geophysical signatures. These signatures reflect structural, lithological and alteration patterns arising from controls on ore deposits and can be applied at regional or detailed scales, using the same data set.At regional scale (e.g. 1:100,000) the magnetic data reflect the regional tectonics and divide the area into domains for the application of appropriate genetic models. At prospect scale (e.g. 1:25,000) the radiometric data allow the extrapolation of poorly outcropping geology to provide a cost-effective mapping technique. The magnetic data can be used to supplement this interpretation or can be used to target deeper sources for direct investigation by drilling.

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Technical Note: Preliminary estimation of rockfall runout zones

Natural Hazards and Earth System Science ◽

10.5194/nhess-11-819-2011 ◽

2011 ◽

Vol 11 (3) ◽

pp. 819-828 ◽

Cited By ~ 59

Author(s):

M. Jaboyedoff ◽

V. Labiouse

Keyword(s):

Slope Angle ◽

Digital Terrain Model ◽

Grid Cell ◽

Technical Note ◽

Field Observations ◽

Source Areas ◽

Terrain Model ◽

Digital Terrain ◽

Energy Line ◽

Potential Source

Abstract. Rockfall propagation areas can be determined using a simple geometric rule known as shadow angle or energy line method based on a simple Coulomb frictional model implemented in the CONEFALL computer program. Runout zones are estimated from a digital terrain model (DTM) and a grid file containing the cells representing rockfall potential source areas. The cells of the DTM that are lowest in altitude and located within a cone centered on a rockfall source cell belong to the potential propagation area associated with that grid cell. In addition, the CONEFALL method allows estimation of mean and maximum velocities and energies of blocks in the rockfall propagation areas. Previous studies indicate that the slope angle cone ranges from 27° to 37° depending on the assumptions made, i.e. slope morphology, probability of reaching a point, maximum run-out, field observations. Different solutions based on previous work and an example of an actual rockfall event are presented here.

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Upgrade of existing algorithms for creating contour lines on topographic maps of the karst surface

Abstracts of the ICA ◽

10.5194/ica-abs-2-19-2020 ◽

2020 ◽

Vol 2 ◽

pp. 1-2

Author(s):

Neža Ema Komel ◽

Klemen Kozmus Trajkovski ◽

Dušan Petrovič

Keyword(s):

Topographic Maps ◽

Topographic Map ◽

Basic Algorithm ◽

Commercial Software ◽

Karst Terrain ◽

Aerial Photos ◽

Contour Lines ◽

Elevation Model ◽

Future Work ◽

Steep Slopes

Abstract. Today, many software tools enable the production of contour lines from relief models, but the results of modelling complex karst relief are often inadequate. Reasons for this may be limited quality and resolution of relief models, limitations of algorithms for calculating contours, or limitations of algorithms for smoothing and displaying additional symbols that further describe relief, such as slope lines, steep slopes and smaller objects that cannot be effectively displayed with contours, etc.We will present research in the field of improving existing algorithms in rugged karst terrain. As a target result, the presentation of relief on the existing national topographic maps in Slovenia, which were made by manual photogrammetric survey of aerial photos stereo pairs, were used. Slovenian elevation model DMR1 (1 m density) is used as a source for the creation of contour lines in various commercial software packages, and by comparing the results with a relief presentation on a topographic map, we selected the most appropriate basic algorithm. This one is further upgraded mainly by enabling automatic selection of auxiliary contour lines in the area, presentation of individual smaller relief objects with appropriate point or linear symbols, addition of slope lines on contours and indications in the middle of depressions and displacement of contour lines in order to better depict the terrain morphology.The results were tested in four different areas in Slovenia. Figure 1 shows the contour lines for a testing area near village Opatje Selo near Slovenia-Italy border, which were made by the best commercial software. The results of the algorithm are shown in Figure 2. The comparison between the results of the algorithm and the national topographic maps in the chosen scale gave promising results. In future work, we are planning to extend the algorithm so that it will be able to provide modelling of different terrains in the region.

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Central Mediterranean Sea forecast: effects of high-resolution atmospheric forcings

Ocean Science Discussions ◽

10.5194/osd-3-637-2006 ◽

2006 ◽

Vol 3 (3) ◽

pp. 637-669 ◽

Cited By ~ 8

Author(s):

S. Natale ◽

R. Sorgente ◽

S. Gaberšek ◽

A. Ribotti ◽

A. Olita

Keyword(s):

High Resolution ◽

Ocean Circulation ◽

Regional Scale ◽

Circulation Model ◽

Surface Current ◽

Ocean Model ◽

Central Mediterranean ◽

Resolution Model ◽

Atmospheric Forcings ◽

Very High

Abstract. Ocean forecasts over the Central Mediterranean, produced by a near real time regional scale system, have been evaluated in order to assess their predictability. The ocean circulation model has been forced at the surface by a medium, high or very high resolution atmospheric forcing. The simulated ocean parameters have been compared with satellite data and they were found to be generally in good agreement. High and very high resolution atmospheric forcings have been able to form noticeable, although short-lived, surface current structures, due to their ability to detect transient atmospheric disturbances. The existence of the current structures has not been directly assessed due to lack of measurements. The ocean model in the slave mode was not able to develop dynamics different from the driving coarse resolution model which provides the boundary conditions.

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Simple rules to minimize exposure to coseismic landslide hazard

10.5194/nhess-2018-271 ◽

2018 ◽

Author(s):

David G. Milledge ◽

Alexander L. Densmore ◽

Dino Bellugi ◽

Nick J. Rosser ◽

Jack Watt ◽

...

Keyword(s):

Landslide Hazard ◽

Complex Relationship ◽

Site Specific ◽

Local Slope ◽

Maximum Angle ◽

Simple Rules ◽

Other Information ◽

Coseismic Landslide ◽

Hazard Area ◽

Steep Slopes

Abstract. Landslides constitute a hazard to life and infrastructure, and their risk is mitigated primarily by reducing exposure. This requires information on landslide hazard at a scale that can enable informed decisions about how to respond to that hazard. Such information is often unavailable to, or not easily interpreted by, those who might need it most (e.g., householders, local government, and NGOs). To address this shortcoming, we develop simple rules to identify landslide hazard that are understandable, communicable, and memorable, and that require no prior knowledge, skills, or equipment to evaluate. We examine rules based on two common metrics of landslide hazard, local slope and upslope contributing area as a proxy for hillslope location, and we introduce and test two new metrics: the maximum angle to the skyline and the hazard area, defined as the upslope area with slope > 39° that reaches a location without passing over a slope of 10°) channels with many steep (> 39°) areas that are upslope. Because local slope alone is a skilful predictor of landslide hazard, we can formulate a third rule as minimise local slope, especially on steep slopes and even at the expense of increasing upslope contributing area, but not at the expense of increasing skyline angle or hazard area. Upslope contributing area, by contrast, has a weaker and more complex relationship to hazard than the other predictors. Our simple rules complement, but do not replace, detailed site-specific investigation; they can be used for initial estimation of landslide hazard or guide decision-making in the absence of any other information.

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