SLOPE STABILITY ANALYSIS OF MOUNT MEAGER, SOUTH-WESTERN BRITISH COLUMBIA, CANADA

The Mount Meager Volcanic Complex (MMVC) in south-western British Columbia is a potentially active, hydrothermally altered massif comprising a series of steep, glaciated peaks. Climatic conditions and glacial retreat has led to the further weathering, exposure and de-buttressing of steep slopes composed of weak, unconsolidated material. This has resulted in an increased frequency of landslide events over the past few decades, many of which have dammed the rivers bordering the Complex. The breach of these debris dams presents a risk of flooding to the downstream communities. Preliminary mapping showed there are numerous sites around the Complex where future failure could occur. Some of these areas are currently undergoing progressive slope movement and display features to support this such as anti-scarps and tension cracks. The effect of water infiltration on stability was modelled using the Rocscience program Slide 6.0. The main site of focus was Mount Meager in the south- east of the Complex where the most recent landslide took place. Two profiles through Mount Meager were analysed along with one other location in the northern section of the MMVC, where instability had been detected. The lowest Factor of Safety (FOS) for each profile was displayed and an estimate of the volume which could be generated was deduced. A hazard map showing the inundation zones for various volumes of debris flows was created from simulations using LAHARZ. Results showed the massif is unstable, even before infiltration. Varying the amount of infiltration appears to have no significant impact on the FOS annually implying that small changes of any kind could also trigger failure. Further modelling could be done to assess the impact of infiltration over shorter time scales. The Slide models show the volume of material that could be delivered to the Lillooet River Valley to be of the order of 109 m3 which, based on the LAHARZ simulations, would completely inundate the valley and communities downstream. A major hazard of this is that the removal of such a large amount of material has the potential to trigger an explosive eruption of the geothermal system and renew volcanic activity. Although events of this size are infrequent, there is a significant risk to the communities downstream of the complex

A comprehensive volcanic hazard assessment for Mount Meager Volcanic Complex, B.C.

Mount Meager Volcanic Complex located in south-western British Columbia exhibits possible volcanic activity in the form of hydrothermal features such as several hot springs around the base and a fumarole field in the northeast corner of the complex. Operational infrastructure, including a run-of-river hydroelectric project, is present in the vicinity of the volcano and a significant population exists only 60 km downstream. Up until now, no volcanic hazard assessment or accompanying map existed for Mount Meager. Hazard assessments are important tools used to understand, manage and reduce the risks associated with volcanic environments. This thesis investigates the potential primary volcanic hazards associated with a future explosive eruption at Mount Meager. These hazards are identified as lahars, pyroclastic density currents and volcanic ash. With the use of numerical modelling programs, the distribution, timescales, intensity of inundation and other parameters are investigated. Finally, a suite of scenario-based preliminary hazard maps have been produced to visually display these hazards as a communication tool. This information relays hazard information to stakeholders with a vested interest in the potential risks involved with any future explosive volcanic event from Mount Meager

Permafrost molards as an analogue for ejecta-ice interactions at Hale Crater, Mars

When the Hale impact crater penetrated the martian cryosphere 1Ga, landforms indicating post-impact volatile mobilisation were generated. We have found landforms in the ejecta blanket of Hale Crater similar to ‘permafrost molards’ found in periglacial environments on Earth, and probably related to the past or present presence of volatiles at/near the surface. Permafrost molards are conical mounds of debris associated with landslide deposits, resulting from the degradation of blocks of ice-rich material mobilised by a landslide in periglacial terrains. Here we analyse the spatial and topographic distribution of conical mounds around the Hale crater at regional and local scales, and compare them to those of molards on the deposits of the Mount Meager debris avalanche in Canada. Hale Crater's conical mounds are located at the distal boundary of the thickest ejecta blanket, which is the closest to the main crater. We observe a similar spatial arrangement of molards along the distal parts of the terminal lobe of the Mount Meager debris avalanche. We then compare the morphology and morphometrics of the conical mounds on Hale Crater to those of terrestrial molards on the Paatuut and Niiortuut rock avalanches in western Greenland. We find that morphology and setting of conical mounds within Hale Crater ejecta are consistent with the formation pathway of molards on Earth. We infer that they originated from blocks of ice-cemented regolith that were produced by the Hale-crater-forming impact, transported by the ejecta flows, and finally degraded to cones of debris (molards) on loss of the interstitial ice. The similarities in distribution between the ejecta flows of Hale and Mount Meager debris avalanche on Earth suggest that the mounds resulted from the rheological separation of the ejecta flows, with a relatively fluid-poor phase that allowed the volatile-rich blocks to survive transport. This supports the prevailing hypothesis that the Hale impact event penetrated the martian cryosphere, providing important constraints on the rheology of martian ejecta deposits

Landslide Hazard and Climate Change in the Mountain Glacial Environment of Northwest North America

The aim of this thesis was to improve the understanding of the complex interactions between climate change and landslide behavior in the periglacial mountain environment of northwest North America. In particular, this thesis quantified the relationship between climate change (temperature, precipitation, and glacier change) and landslide behavior (magnitude, frequency, and distribution). To achieve this larger aim, four specific research objectives were established: (a) Determine changes in the frequency and distribution of landslides in glacial regions of northwest North America by developing a landslide inventory; (b) Quantify climate change factors, specifically trends in temperature and precipitation; (c) Assess changes in glacier ice area and volume in northwest North America; and (d) Establish a quantitative relationship between climate change, glacier ice loss, and change in landslide hazard. Changes in the frequency and distribution of large (>1Mm3) catastrophic landslides in the mountain glacial environment were determined by developing a regional landslide inventory (Evans and Delaney, Unpublished). The landslide inventory was explored using a magnitude-frequency plot, and results showed that seismically triggered landslides had proportionally fewer large events than non-seismically triggered landslides, highlighting the importance of climate related triggers in large events. Also, the frequency of landslides was determined to be increasing over time, especially at high latitudes (>57 degrees N). Climate change analysis was completed using meteorological station data and trend testing (i.e., Mann-Kendall, Sen’s slope) to develop indices showing temperature and precipitation change. Results show ubiquitous warming (particularly in winter and summer), as well as increasingly dry conditions in Alaska, Yukon, and northern British Columbia, with wetter conditions in central and southern British Columbia. Index results were correlated with landslide mass hypsometrically, showing strong statistical evidence (i.e., Wilcoxon Rank Sum Test) of a connection between increasing temperature and increasing landslide hazard. Precipitation was not correlated with landslide hazard with certainty. Glacier ice loss was assessed using a case study of Mount Meager Volcanic Complex (MMVC), which showed drastic reduction of ice area and volume in response to increased temperature and precipitation. Two major landslides at MMCV (1975/2010) have been found to be triggered by the aforementioned climate factors (increased temperature and precipitation leading to ice loss)

Characterisation and Analysis of Catastrophic Landslides and Related Processes using Digital Topographic Data

This thesis represents a large body of work that seeks to describe, quantify, and simulate the behaviour of large rock slope failures (> 1 Mm³), in the form of landslides and rock avalanches, and their secondary processes, such as landslide-dammed lakes, utilizing remotely sensed data. Remotely sensed data includes aerial photography, high resolution satellite imagery from various platforms (e.g. LANDSAT, ASTER, EO-1, SPOT), and digital topographic elevation models of the Earth’s surface (e.g. SRTM-3, ASTER GDEM2, LiDAR). This thesis focused on regions in northwest North America (British Columbia, Yukon Territory, and Alaska), and on regions in the Himalaya and Pamirs Mountain chains (Tajikistan, Afghanistan, Pakistan, Tibet, and India). These study regions are each highly dynamic landscapes, where the occurrence of rock slope failures per area is higher than non-mountainous regions, and these events are aiding to the shape and profile of the landscapes and surfaces found today. This thesis focuses on: 1) the ability to accurately calculate geometrics (e.g. areas, volumes, runouts, debris depths) for large scale landslides and their associated landslide dammed lakes (e.g. areas, volumes, outbursts), utilizing data from remotely sensed sources; 2) the attempt to successfully simulate the observed dynamics for both landslide emplacement and their resulting debris deposits (DAN-W, DAN3D), and possible outburst flood scenarios (FLO2D); and, 3) attempt to quantify the kinetic and specific energy involved in rock avalanches, and how these energetics relate to fragmentation, as well as the lateral spreading and thinning of debris sheets. The river valleys of the northwest Himalayas (Pakistan and India) and the adjacent Pamirs Mountains of Afghanistan and Tajikistan contain in excess of two hundred known rockslide deposits of unknown age that have interrupted surface drainage and previously dammed major rivers in the region in recent and prehistoric time. Some prehistoric rockslide dams in the northwest Himalayas have impounded massive lakes with volumes in excess of 20 Gm³. The region contains: 1) the highest rockslide dam in the world (the 1911 Usoi rockslide, Tajikistan), which impounds the current largest rockslide-dammed lake (Lake Sarez) on Earth (est. volume 17 Gm³); 2) the largest documented outburst flood (6.5 Gm³) associated with a historical rockslide dam outburst (the 1841 Indus Flood, Pakistan); and, 3) the world’s most recent rockslide-dammed lake emergency, the 2010 Attabad rockslide dam on the Hunza River, in the Upper Indus basin, including the newly created Lake Gojal. By accurately quantifying the volume of an impoundment, and the downstream valley topography (DEM), floodwave scenarios can be created for various breaching situations, allowing for the delineation of downstream inundation areas, or the creation of hazard and risk scenarios. Two methods are used to attempt to quantify the volumes of landslide-dammed lakes: 1) a contour interpolation method, focusing on the creation of contours to represent lake levels in the DEM data; and, 2) a new technique using digitized shorelines and statistical methods to obtain lake elevations on specific dates. A new technique has also been developed to quantify the larger block fragmentation from rock avalanches in the glacial environment, and a credible grain-size curve for the largest blocks can be obtained, aiding in the creation of a more complete grain-size curve for a particular event. The combination of landslides and their associated landslide dammed lakes are an important geomorphic process to study, as these events have a direct relationship to the hazard and risk faced by local communities living and working in these regions. By understanding the emplacement and deposit dynamics of large landslides and/or the outburst flood scenarios from naturally impounded reservoirs, we can attempt to reduce the direct impacts these events have to local communities.4 month

Worldwide Research Trends in Landslide Science

Landslides are generated by natural causes and by human action, causing various geomorphological changes as well as physical and socioeconomic loss of the environment and human life. The study, characterization and implementation of techniques are essential to reduce land vulnerability, different socioeconomic sector susceptibility and actions to guarantee better slope stability with a significant positive impact on society. The aim of this work is the bibliometric analysis of the different types of landslides that the United States Geological Survey (USGS) emphasizes, through the SCOPUS database and the VOSviewer software version 1.6.17, for the analysis of their structure, scientific production, and the close relationship with several scientific fields and its trends. The methodology focuses on: (i) search criteria; (ii) data extraction and cleaning; (iii) generation of graphs and bibliometric mapping; and (iv) analysis of results and possible trends. The study and analysis of landslides are in a period of exponential growth, focusing mainly on techniques and solutions for the stabilization, prevention, and categorization of the most susceptible hillslope sectors. Therefore, this research field has the full collaboration of various authors and places a significant focus on the conceptual evolution of the landslide science