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

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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Landslides and dam damage resulting from the Jiuzhaigou earthquake (8 August 2017), Sichuan, China

Royal Society Open Science ◽

10.1098/rsos.171418 ◽

2018 ◽

Vol 5 (3) ◽

pp. 171418 ◽

Cited By ~ 12

Author(s):

Bo Zhao ◽

Yun-sheng Wang ◽

Yong-hong Luo ◽

Jia Li ◽

Xin Zhang ◽

...

Keyword(s):

Rock Mass ◽

Failure Modes ◽

Water Pressure ◽

Hanging Wall ◽

Slope Angle ◽

Focal Depth ◽

Slope Aspect ◽

Jiuzhaigou Earthquake ◽

Mass Failure ◽

Rock Mass Failure

At 21.19 on 8 August 2017, an Ms 7.0 earthquake struck the Jiuzhaigou scenic spot in northwestern Sichuan Province, China. The Jiuzhaigou earthquake is a strike-slip earthquake with a focal depth of 20 km at 33.20° N and 103.82° E, and was caused by two concealed faults. According to emergency investigations and remote sensing interpretations, the Jiuzhaigou earthquake triggered 1780 landslides, damaged one dam (Nuorilang Waterfall) and broke one dam (Huohua Lake). The landslides mainly occurred in the Rize Valley and Shuzheng Valley and in Jiuzhai Paradise. The landslides involved hanging wall and back-slope effects, and the slope angle, slope aspect, seismic faults and valley trend were obviously related to the occurrence of the landslides. Specifically, most of the landslides were shallow landslides, rockfalls and rock avalanches and were small in scale. The failure modes of landslides mainly include wedge rock mass failure, residual deposit failure, relaxed rock mass failure and weathered rock mass failure. The initial low stability of the dam coupled with the topographic effect, back-slope effect and excess pore water pressure led to damage to the Nuorilang Waterfall dam.

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

Natural Hazards and Earth System Science ◽

10.5194/nhess-9-1643-2009 ◽

2009 ◽

Vol 9 (5) ◽

pp. 1643-1653 ◽

Cited By ~ 51

Author(s):

A. Loye ◽

M. Jaboyedoff ◽

A. Pedrazzini

Keyword(s):

High Resolution ◽

Gaussian Distribution ◽

Regional Scale ◽

Slope Angle ◽

Topographic Maps ◽

Angle Distribution ◽

Source Areas ◽

Morphological Unit ◽

Other Information ◽

Steep Slopes

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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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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