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Mount Meager is a deeply eroded quaternary volcanic complex located in southwestern British Columbia (BC) and is known for its frequent large landslides. In 2010, the south face of Mount Meager collapsed, generating a long-runout debris avalanche that was one of the largest landslides (50 × 106 m3) in Canadian history. Over the past 14 years, the landslide deposit has been reworked by stream action, delivering large amounts of sediment to Lillooet River, just downstream. In this study, we investigate 10 years of geomorphic evolution of the landslide deposit using orthophotos and digital elevation models (DEMs) generated using Structure from Motion (SfM) photogrammetry on aerial photographs acquired during unmanned aerial vehicle (UAV) and Global Navigation Satellite System (GNSS) surveys. The SfM products were used to produce a series of precise maps that highlight the geomorphological changes along the lower Meager Creek within the runout area of the landslide. Comparison of DEMs produced from 2010, 2012, 2015, and 2019 imagery allowed us to calculate deposit volume changes related to erosion, transport, and redeposition of landslide material. We estimate that about 1.1 × 106 m3 of sediment was eroded from the landslide deposit over the period 2015–2019. About 5.2 × 105 m3 of that sediment was redeposited inside the study area. About 5.8 × 105 m3 of sediment, mainly sand, silt, and clay, were exported from the study area and are being carried by Lillooet River towards Pemberton, 40 km from Mount Meager, and farther downstream. These remobilized sediments likely reduce the Lillooet River channel capacity and thus increase flood hazards to the communities of Pemberton and Mount Currie. Our study indicates a landslide persistence in the landscape, with an estimated 47-year half-life decay, suggesting that higher flood hazard conditions related to increased sediment supply may last longer than previously estimated. This study shows the value of using SfM in tandem with historic aerial photographs, UAV photos, and high-resolution satellite imagery for determining sediment budgets in fluvial systems. [ABSTRACT FROM AUTHOR]

The sediment supplied to a stream channel impacts the morphological trends experienced by that channel, and the long‐term trends are important to understand for many riverine applications. We introduce the term 'net morphological displacement' (NMD) to denote the net channel change revealed by the morphological method over multiple sediment transport events to make the concept more explicit for river management and use it to determine equilibrium or disequilibrium states. This study explores the morphological response of East Creek, a small threshold gravel‐bed channel in the Coast Mountains of British Columbia, Canada, to variations in flow and sediment supply at multiple spatial and temporal scales over 15 years. High‐resolution topographic data (HRTD) of the bed were combined with cross‐sectional surveys of the banks to determine the sediment supply that the channel responded to annually. The level of detection used to remove noise associated with HRTD was calibrated using an independent tracer stone dataset. The net effects from multiple floods caused distributions of bed elevation change to generally follow the log‐normal distribution, and mean depths of erosion and deposition were predominantly similar between morphological units. At the reach scale, the various reaches of East Creek responded differently to the same hydrological events due to the impacts from the varying supply conditions on the NMD. Shorter measurement periods would have resulted in inconclusive information that does not show the long‐term morphological trends of the channel. Determination of these trends can take years or decades, depending on the time and space scales of change, but there is generally a lack of long‐term channel monitoring programmes, notably after river restoration. More long‐term channel monitoring programmes are required to assess restoration projects and ensure their long‐term sustainability. [ABSTRACT FROM AUTHOR]

The article focuses on evidence of the course reversal of the Fraser River in British Columbia, Canada during the Pleistocene Epoch. Geochronological analysis of volcanic dams in the Dog Creek region of the Fraser River suggests a reversal of drainage and sediment transport. Topics include glaciofluvial erosion, the formation of the submarine Nitinat Fan, and uplift of the Coast Mountain range.