Effect of Micropiles on Clean Sand Liquefaction Risk Based on CPT and SPT

Liquefaction is a hazardous seismic-based phenomenon, which causes an abrupt decrease in soil strength properties and can result in the massive destruction of the built environment. This research presents a novel approach to reduce the risk of soil liquefaction using jet-grouted micropiles in clean sands. The saturated soil profile of the study project mainly contains clean sands, which are suitable to more reliably employ simplified soil liquefaction analyses. The grouting is conducted using 420 micropiles to increase the existing soil properties. The effect of jet grouting on reducing the potential of liquefaction is assessed using the results of the cone penetration test (CPT) and the standard penetration test (SPT), which were conducted before and after jet grouting by implementing micropiles in the project sites. According to three CPT-based liquefaction analyses, the Juang method predicts the most effective improvement range of the factor of safety in the clean sand. The Boulanger and Idriss, and Eurocode methods show comparable evaluations. Results of the SPT-based analyses show the most considerable increase of the factor of safety following the Boulanger and Idriss, and NCEER approaches in the SP soil. CPT- and SPT-based analyses confirm the effectiveness of jet grouting by micropiles on enhancing soil properties and reducing the risk of liquefaction

The SWADE model for landslide dating in time series of optical satellite imagery

Landslides are destructive natural hazards that cause substantial loss of life and impact on natural and built environments. Landslide frequencies are important inputs for hazard assessments. However, dating landslides in remote areas is often challenging. We propose a novel landslide dating technique based on Segmented WAvelet-DEnoising and stepwise linear fitting (SWADE), using the Landsat archive (1985–2017). SWADE employs the principle that vegetation is often removed by landsliding in vegetated areas, causing a temporal decrease in normalized difference vegetation index (NDVI). The applicability of SWADE and two previously published methods for landslide dating, harmonic modelling and LandTrendr, are evaluated using 66 known landslides in the Buckinghorse River area, northeastern British Columbia, Canada. SWADE identifies sudden changes of NDVI values in the time series and this may result in one or more probable landslide occurrence dates. The most-probable date range identified by SWADE detects 52% of the landslides within a maximum error of 1 year, and 62% of the landslides within a maximum error of 2 years. Comparatively, these numbers increase to 68% and 80% when including the two most-probable landslide date ranges, respectively. Harmonic modelling detects 79% of the landslides with a maximum error of 1 year, and 82% of the landslides with a maximum error of 2 years, but requires expert judgement and a well-developed seasonal vegetation cycle in contrast to SWADE. LandTrendr, originally developed for mapping deforestation, only detects 42% of landslides within a maximum error of 2 years. SWADE provides a promising fully automatic method for landslide dating, which can contribute to constructing landslide frequency-magnitude distributions in remote areas

Less extreme and earlier outbursts of ice-dammed lakes since 1900

Episodic failures of ice-dammed lakes have produced some of the largest floods in history, with disastrous consequences for communities in high mountains1–7. Yet, estimating changes in the activity of ice-dam failures through time remains controversial because of inconsistent regional flood databases. Here, by collating 1,569 ice-dam failures in six major mountain regions, we systematically assess trends in peak discharge, volume, annual timing and source elevation between 1900 and 2021. We show that extreme peak flows and volumes (10 per cent highest) have declined by about an order of magnitude over this period in five of the six regions, whereas median flood discharges have fallen less or have remained unchanged. Ice-dam floods worldwide today originate at higher elevations and happen about six weeks earlier in the year than in 1900. Individual ice-dammed lakes with repeated outbursts show similar negative trends in magnitude and earlier occurrence, although with only moderate correlation to glacier thinning8. We anticipate that ice dams will continue to fail in the near future, even as glaciers thin and recede. Yet widespread deglaciation, projected for nearly all regions by the end of the twenty-first century9, may bring most outburst activity to a halt

Resource Selection of Free-ranging Horses Influenced by Fire in Northern Canada

Free-ranging or feral horses (Equus ferus caballus) were important to the livelihood of First Nations and indigenous communities in Canada. The early inhabitants of the boreal region of British Columbia (BC) capitalized on naturally occurring wildfires and anthropogenic burning to provide forage for free-ranging horses and manage habitat for wildlife. This form of pyric herbivory, or grazing driven by fi re via the attraction to the palatable vegetation in recently burned areas, is an evolutionary disturbance process that occurs globally. However, its application to manage forage availability for free-ranging horses has not been studied in northern Canada. Across Canada, there are varying levels of governance for feral and free-ranging horses depending on the provincial jurisdiction and associated legislation. The BC Range Act (Act) allows range tenure holders to free-range horses that they own for commercial operations on Crown land. Big-game guide outfitters as range tenure holders are provided grazing licences or grazing permits under the Act with an approved range use plan. Guide outfitters and other range tenure holders have incorporated fi re ecology as part of their rangeland management in mountainous portions of the boreal forest of northeastern BC to promote mosaics of vegetation height and species composition across the landscape to meet nutritional requirements of their free-ranging horses. Using resource selection function models, we evaluated the influence of pyric herbivory on boreal vegetation and use by horse herds occupying 4 distinct landscapes. We found that horses preferentially selected recently burned areas and areas that burned more frequently when they were available. We also found that horses avoided steep slopes and forest cover types. Fire and the ecological processes associated with it, including pyric herbivory, are important considerations when managing boreal rangelands in northeastern BC. Because historical fi re regimes of the boreal region of Canada differ from the arid regions of the United States inhabited by feral horses, the role of pyric herbivory in altering horse distributions in the United States is limited

The 28 November 2020 landslide, tsunami, and outburst flood – a hazard cascade associated with rapid deglaciation at Elliot Creek, British Columbia, Canada

We describe and model the evolution of a recent landslide, tsunami, outburst flood, and sediment plume in the southern Coast Mountains, British Columbia, Canada. On November 28, 2020, about 18 million m3 of rock descended 1,000 m from a steep valley wall and traveled across the toe of a glacier before entering a 0.6 km2 glacier lake and producing >100-m high run-up. Water overtopped the lake outlet and scoured a 10-km long channel before depositing debris on a 2-km2 fan below the lake outlet. Floodwater, organic debris, and fine sediment entered a fjord where it produced a 60+km long sediment plume and altered turbidity, water temperature, and water chemistry for weeks. The outburst flood destroyed forest and salmon spawning habitat. Physically based models of the landslide, tsunami, and flood provide real-time simulations of the event and can improve understanding of similar hazard cascades and the risk they pose

High Mountain Areas

The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high-mountain regions, which are home to roughly 10% of the global population. Widespread cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s Fifth Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in the cryosphere are not assessed in this chapter. Polar mountains are included in Chapter 3, except those in Alaska and adjacent Yukon, Iceland, and Scandinavia, which are included in this chapter

A cautionary note for rock avalanche field investigation – recent sequential and overlapping landslides in British Columbia

Large rock avalanches on glaciers are an annual occurrence in the mountains of western North America. Following an event, landslide investigators may strive to quickly arrive on site to assess the deposit. Satellite remote sensing imagery demonstrates that caution is warranted for on- site field assessments. We combine Landsat, Sentinel-1(radar), Sentinel-2 and Planet imagery to reconstruct the events of four recent double overlapping rock avalanche deposits in British Columbia. In our examples substantial precursory rock avalanches are closely followed (days - months) and buried by much larger landslides. We suggest that landslide investigators exercise caution when assessing fresh rock avalanches avalanche deposits in the field.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Over 16,000 Years of Fire Frequency Determined from AMS Radiocarbon Dating of Soil Charcoal in an Alluvial Fan at Bear Flat, Northeastern British Columbia

We present results of radiocarbon dating of charcoal from paleosols and buried charcoal horizons in a unique sequence, which potentially records the last 36,000 yr, from a fan at Bear Flat, British Columbia (BC) (56 degrees 16'51"N, 121 degrees 13'39"W). Evidence for forest-fire charcoal is found over the last 13,500 +/110 14C yr before present (BP) or 16,250 +/700 cal BP. The study area is located east of the Rocky Mountains in an area that was ice-free at least 13,970 +/170 14C yr BP (17,450-16,150 cal BP) ago. The latest evidence of fire is during the Medieval Warm Period (MWP). The charcoal ages show a periodicity in large fires on a millennial scale through the Holocene—an average of 4 fires per thousand years. Higher fire frequencies are observed between 2200 to 2800 cal BP, ~5500 and ~6000 cal BP, ~7500 to 8200 cal BP, and 9000 to 10,000 cal BP. These intervals also appear to be times of above-average aggradation of the fan. We conclude that fire frequency is related to large-scale climatic events on a millennial time scale.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Temporal variability of diverse mountain permafrost slope movements derived from multi-year daily GPS data, Mattertal, Switzerland

In this study, high resolution surface measurements of diverse slope movements are compared to environmental factors such as ground surface temperature (GST) and snow cover, in order to reveal and compare velocity fluctuations caused by changing environmental conditions. The data cover 2 years (2011–2013) of Global Positioning System (GPS) and GST measurements at 18 locations on various slope movement types within an alpine study site in permafrost (Mattertal, Switzerland). Velocities have been estimated based on accurate daily GPS solutions. The mean annual velocities (MAV) observed at all GPS stations varied between 0.006 and 6.3 ma−1. MAV were higher in the period 2013 compared to 2012 at all stations. The acceleration in 2013 was accompanied by a longer duration of the snow cover and zero curtain and slightly lower GST. The amplitude (0–600 %) and the timing of the intra-annual variability were generally similar in both periods. At most stations, an annual cycle in the movement signal was observed, with a phase lag of 1–4 months to GST. Maximum velocity typically occurred in late summer and autumn, and minimum velocity in late winter and beginning of spring. The onset of acceleration always started in spring during the snowmelt period. At two stations located on steep rock glacier tongues, overprinted on the annual cycle, short-term peaks of velocity increase, occurred during the snowmelt period, indicating a strong influence of meltwater