High-resolution topographic surveying is traditionally associated with high capital and logistical costs, so that data acquisition is often passed on to specialist third party organizations. The high costs of data collection are, for many applications in the earth sciences, exacerbated by the remoteness and inaccessibility of many field sites, rendering cheaper, more portable surveying platforms (i.e. terrestrial laser scanning or GPS) impractical. This paper outlines a revolutionary, low-cost, userfriendly photogrammetric technique for obtaining high-resolution datasets at a range of scales, termed 'Structure-from-Motion' (SfM). Traditional softcopy photogrammetric methods require the 3-D location and pose of the camera(s), or the 3-D location of ground control points to be known to facilitate scene triangulation and reconstruction. In contrast, the SfM method solves the camera pose and scene geometry simultaneously and automatically, using a highly redundant bundle adjustment based on matching features in multiple overlapping, offset images. A comprehensive introduction to the technique is presented, followed by an outline of the methods used to create high-resolution Digital Elevation Models (DEMs) from extensive photosets obtained using a consumer-grade digital camera. As an initial appraisal of the technique, an SfM-derived DEM is compared directly with a similar model obtained using Terrestrial Laser Scanning. This intercomparison reveals that decimetre-scale vertical accuracy can be achieved using SfM even for sites with complex topography and a range of land-covers. Example applications of SfM are presented for three contrasting landforms across a range of scales including; an exposed rocky coastal cliff; a breached moraine-dam complex; and a glaciallysculpted bedrock ridge. The SfM technique represents a major advancement in the field of photogrammetry for geoscience applications. Our results and experiences indicate SfM is an inexpensive, effective, and flexible approach to capturing complex topography.

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Westoby, M. J., Glasser, N. F., Brasington, J., Hambrey, M. J., Quincey, D. J., Reynolds, J. M. (2014). Modelling outburst floods from moraine-dammed glacial lakes. Earth-Science Reviews, 134, 137-159 Embargoed: 3.4.15In response to climatic change, the size and number of moraine-dammed supraglacial and proglacial lake systems have increased dramatically in recent decades. Given an appropriate trigger, the natural moraine dams that impound these proglacial lakes are breached, producing catastrophic Glacial Lake Outburst Floods (GLOFs). These floods are highly complex phenomena, with flood characteristics controlled, in the first instance, by the style of breach formation. Downstream, GLOFs typically exhibit transient, often non-Newtonian fluid dynamics as a result of high rates of sediment entrainment from the dam structure and channel boundaries. Combined, these characteristics introduce numerous modelling challenges. In this review, the historical, contemporary and emerging approaches available to model the individual stages, or components, of a GLOF event are introduced and discussed. A number of methods exist to model the stages of a GLOF event. Dam-breach models can be categorised as being empirical, analytical or numerical in nature, with each method having significant advantages and shortcomings. Empirical relationships that produce estimates of peak discharge and time to peak are straightforward to implement, but the applicability of these models is often limited by the nature of the case study data from which they are derived. Furthermore, empirical models neglect the inclusion of basic hydraulic principles that describe the mechanics of breach formation. Analytical or parametric models simulate breach development using simplified versions of the physically based equations that describe breach enlargement, whilst complex, physically-based codes represent the state-of-the-art in numerical dam-breach modelling. To date, few of the latter have been applied to investigate the moraine-dam failure problem. Despite significant advances in the physical complexity and availability of higher-order hydrodynamic solvers, the majority of published accounts that have attempted to reconstruct or predict GLOF characteristics have been limited, often by necessity, to the use of relatively simplistic models. This is in part attributable to the unavailability of terrain models of many high-mountain catchments at the fine spatial resolutions required for the effective application of numerically-sophisticated codes, and their proprietary (and often cost-prohibitive) nature. However, advanced models are experiencing increasing use in the glacial hazards literature. In particular, the suitability of emerging mesh-free, particle-based methods for simulating dam-breach and GLOF routing may represent a solution to many of the challenges associated with modelling this complex phenomenon. Sources of uncertainty in the GLOF modelling chain have been identified by various workers. However, to date their significance for the robustnes...

Severe acute respiratory virus syndrome 2 (SARS-CoV-2) has led to a worldwide pandemic. Early studies in solid organ transplant (SOT) recipients suggested a wide variety of presentations, however, there remains a paucity of robust data in this population. We conducted a systematic review and meta-analysis of SOT recipients with SARS-CoV-2 infection from January 1 st t October 9 th , 2020. Pooled incidence of symptoms, treatments and outcomes were assessed. Two hundred and fifteen studies were included for systematic review and 60 for meta-analysis. We identified 2,772 unique SOT recipients including 1,500 kidney, 505 liver, 141 heart and 97 lung. Most common presenting symptoms were fever and cough in 70.2% and 63.8% respectively. Majority (81%) required hospital admission. Immunosuppressive medications, especially antimetabolites, were decreased in 76.2%. Hydroxychloroquine and interleukin six antagonists were administered in59.5% and 14.9% respectively, while only few patients received remdesivir and convalescent plasma. Intensive care unit admission was 29% from amongst hospitalized patients. Only few studies reported secondary infections. Overall mortality was 18.6%. Our analysis shows a high incidence of hospital admission in SOT recipients with SARS-CoV-2 infection. As management of SARS-CoV-2 continues to evolve, long-term outcomes among SOT recipients should be assessed in future studies.

Abstract. Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity – rather unexpectedly – have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.

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