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<jats:title>Summary</jats:title><jats:p>One‐dimensional models for river bifurcations rely on a nodal point relation that determines the distribution of sediments between the downstream branches. The most widely‐adopted nodal point relation describes the two‐dimensional topographic effects exerted by the bifurcation by introducing two computational cells, located just upstream the bifurcation node, that laterally exchange water and sediments. The results of this approach strongly depend on a dimensionless parameter that represents the ratio between the cell length and the main channel width, whose value needs to be empirically estimated. Previous works proposed calibrating this parameter on the basis of more complete two‐dimensional linear models, which directly solve the momentum and mass conservation equations. This study demonstrates that a full consistency between the one‐dimensional approach and the two‐dimensional models can be directly achieved by adopting different scaling for the bifurcation cell length, which results in a theoretically‐defined and constant dimensionless length parameter. Comparison with experimental observations reveals that this physically‐based scaling yields more accurate predictions of bifurcation stability and discharge asymmetry. This indicates that the proposed method may provide a more reliable and precise estimation of the cell length, potentially improving the performance of one‐dimensional models for bifurcation processes in rivers.</jats:p>

<jats:title>Abstract</jats:title><jats:p>How one individual characterises another successful individual varies widely. At a time when work–life balance and the use of metrics are key concerns within the academic landscape, Early Career Academics (ECAs) are voicing particular worries about the opacity with which we discuss and define success in academia, which influences recruitment and progression in unseen ways. Drawing on the results of a survey of 92 geomorphologists, earth and environmental scientists (96% from Europe or North America) and textual analysis of 54 job advertisements for early career positions at UK institutions spanning 2010–2021, we posit that there is a divergence between the perceptions, expectations and realities of academic success and that this has widened over the last decade. We find limited evidence of gendered differences in how academics define success, in stark contrast to employment and promotion outcomes within universities. We also find notable differences in how individual, more senior academics value publications and grant capture, which is at odds with advice usually given to ECAs. This mismatch is reinforced by the steady rise in the total number of essential job criteria listed on job advertisements for early career positions. Strong applicants are expected to excel in more areas than a decade ago. We put forward a series of recommendations implementable at local levels (e.g., research groups, learned society committees, departments) to help ensure markers of success are defined, valued and implemented in more appropriate and consistent ways. These include: the necessity of establishing clear guidelines for recruitment, promotion and awards, and ensuring these are visible and accessible; greater transparency around the weightings given to different criteria in a job advert; and a call to the community to reflect on how our individual markers of success match our career advice and the decisions taken by hiring or promotion panels we sit on.</jats:p>

<jats:title>Abstract</jats:title><jats:p>River management is founded on predictable self‐organisation between river form and catchment controls in alluvial rivers. However, a substantial proportion of rivers are not fully alluvial. In previously glaciated landscapes, boulder‐rich glacial till influences river channel form and process. Increasing interest in nature‐ and process‐based river restoration requires knowledge of pre‐disturbance natural processes, which does not exist for semi‐ and non‐alluvial rivers in Fennoscandia. We aimed to determine the role of Pleistocene glaciation and subsequent deglaciation versus Holocene fluvial processes in controlling channel form of boulder‐bed rivers in Fennoscandia. We quantified morphological characteristics of northern Swedish boulder‐bed rivers, in which channel morphology was minimally impacted by humans, and used the degree of alluvial signatures to infer fluvial and legacy glacial controls. We conducted surveys of reach‐scale channel geometry, boulder and wood distributions and catchment characteristics for 20 reference reaches (drainage area: 11–114 km<jats:sup>2</jats:sup>). Reaches ranged in slope from 1% to 8% and were extremely diverse in channel geometry. Rivers showed little self‐organisation at the reach scale; no association exists between channel width and channel slope or bed sediment size. Boulders were rarely clustered into bedforms (e.g., step‐pools) typical of boulder‐bed mountain rivers. Drainage area was positively correlated with channel capacity but not channel width, slope or sediment size. Channel boulder density was best predicted by surveys of terrestrial boulders. Consequently, channel geometry, boulder size and the distribution of boulders were primarily controlled by legacy glacial conditioning rather than current fluvial processes, with some alluvial adjustment of smaller particles within the boulder template. Therefore, restoration of semi‐alluvial rivers should take into account local sediment and geomorphic conditions rather than use management principles built for fully alluvial rivers.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Spatial distributions of drumlin fields encode information about ice sheet dynamics. No drumlins formed beneath the most lobate parts of the Laurentide Ice Sheet's southern margin, in South Dakota, Iowa and Illinois, whereas ice lobes to the northeast generally produced drumlins. This pattern may have resulted from northerly ice overriding permafrost. Here we propose a new hypothesis for this pattern by constructing a LiDAR‐based landform map and applying a model of drumlin formation to account for the absence of drumlins beneath the largest of the ice sheet's southern lobes, the Des Moines Lobe. Broad belts of hummocky topography, ice‐walled lake plains, doughnuts and minor moraines, which together cover 90% of the lobe's upland area in Iowa, attest to widespread ice stagnation, as does the lobe's scarcity of eskers. Most stagnation topography is subtle, with insufficient relief to have obscured drumlins that might have formed before stagnation. Minor moraines are crevasse‐squeeze ridges diagnostic of surging, and their ubiquity indicates that during surging, the lobe's soft bed was weak nearly everywhere. End moraines are generally parallel to a minor moraine setup‐glacier, implying that surge‐driven advances were more numerous than indicated by the three major end moraines of the lobe. In the only physically based model of drumlin formation that includes surging, till deposition occurs during surges when effective pressure is uniformly low, whereas drumlins develop during quiescent flow between surges, when basal slip and low‐pressure R‐channels create the spatial gradients in effective pressure necessary to sculpt drumlins by differential erosion. Landforms of the lobe, however, indicate stagnation and down‐wasting during quiescence, without significant basal slip or hydraulic potential gradients necessary for R‐channels. We hypothesize that for the three southernmost lobes of the Laurentide Ice Sheet, surging followed by widespread down‐wasting of stagnant ice prevented drumlin formation, whereas beneath northern lobes it was permitted by climatically‐forced ice advance.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Excess water pressure strongly affects the rheology and flow behaviour of debris flows, and the mechanisms for development and persistence of the pressure can be diverse. Using nine experimental slurries prepared with the sediments collected from the deposit of a large‐magnitude debris flow by modifying maximum grain size and solid concentration, the influence of agitation on excess water pressure is investigated with a cylinder apparatus, consisting of a coaxially mounted bucket and impeller driven by a variable‐speed motor. Agitation proceeding in three dynamic stages raises relative excess water pressure (<jats:italic>R</jats:italic>) by 17%–34% of the peak <jats:italic>R</jats:italic> in the static stage, showing that agitation can significantly increase excess water pressure. The magnitude of the steady <jats:italic>R</jats:italic> increases with the level of agitation, which is measured by impeller speed and slurry temperature, and the steady <jats:italic>R</jats:italic> in a slurry is agitation‐level‐dependent below its potential maximum value. The transfer of particle weight to water in debris flows can occur under zero or very low to extremely low effective stresses. Agitation raises excess water pressure essentially by promoting dispersion of the finest‐grained grains in water and that of progressively larger grains in gradually coarser‐grained slurries. The flow resistance of the tested slurries, characterized by net torque exerted on the impeller by the motor, decreases with increasing liquefaction ratio, demonstrating that agitation enhances debris‐flow mobility by raising excess water pressure. It is of importance to dampen agitation by building proper mitigation measures in remedial practices.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Image collection strategies and ground control points (GCPs) are of particular importance for uncrewed aerial vehicle combined with Structure‐from‐Motion (UAV–SfM) photogrammetry, and the generalization of their effects has proved elusive. This study designed various photogrammetric scenarios to investigate the effects of image collection strategies, ground control quantity, and their interaction on digital elevation model (DEM) errors and their spatial structure in high‐relief terrain. The results of 1.77 × 10<jats:sup>5</jats:sup> UAV–SfM scenarios provide insights for improving UAV–SfM practices. A high image capture angle (20–40°) enhances camera calibration quality decreasing the magnitude and spatial correlation of errors. High camera inclination reduces the sensitivity of mean and standard deviation of error to flying height but not the spatial correlation of error. Including additional data (e.g. supplemented convergent images; images captured at multiple flying heights) has only a minor effect if imagery is highly inclined. GCPs provide more effective constraints than image collection strategies. The mean error and standard error decline quickly with a small number of GCPs and then become stable in all scenarios, but the spatial correlation of error can be further improved with increasing GCPs. However, the effects of GCP quantity do interact with image collection strategies. High camera inclination reduces requirements for GCPs, whilst strategies combining different flying heights and image orientations have little effect on necessary GCP quantity. The distribution of GCPs still affects the errors, but the effect of GCP distribution becomes less important with an increase in the number of GCPs. Finally, we show that UAV–SfM photogrammetric quality assessment should routinely assess the spatial dependence of error using a statistic like Moran's <jats:italic>I</jats:italic>.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Early detection of landslides is important for prevention and mitigation of landslide disasters. Especially, accurately identifying potential landslides along high‐speed railway is becoming a pressing issue for operation safety of high‐speed railway. Here, 161 Sentinel‐1A satellite images from March 2017 to September 2022 were acquired to detect potential landslides along the Lanzhou‐Urumqi high‐speed railway (LUHR) in Qinghai. Results show that rainfall is the main cause for the transition from secondary creep (steady state) to tertiary creep (accelerated) at the Jiujiawan landslide. The hot spot analysis method was used to cluster the average line‐of‐sight deformation velocity along the LUHR, effectively extracting five deformation zones that may pose a threat. Optical satellite image analysis revealed four potential landslides and one unstable slope. Furthermore, the rescaled range analysis documented that the Hurst exponent is greater than 0.8 for all four potential landslide instability points, implying that the identified potential landslide areas are still in motion and may pose a threat to the operation of the LUHR. On this basis, we propose a framework for early identification and monitoring of landslides along the high‐speed railway lines that supports landslide hazard managing with the goal to reduce landslide risk.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Small, circular holes, lined with a thin gypsum veneer, and closely associated with gypsum tumuli (domes), occur at Salar de Pajonales, a salt flat in the northern Andes, Chile. We propose a model in which the formation of the gypsum‐lined holes, and less commonly the formation of the tumuli itself, is controlled by the unique juxtaposition of physiographic, geologic and hydrologic conditions. On a regional scale, Salar de Pajonales is unusual compared to other salars, as it is located close to a large magmatic inflation centre (Lazufre), lies along strike of major regional structural trends, is a large ephemeral lake and contains high salt concentrations. On a basin scale, the lined holes are only present along strike of lineaments that are directly linked to the local stress regime. In turn, these lineaments control the location of degassing and subsequently the formation of the lined holes in the gypsum tumuli and, in part, the tumuli themselves.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Glacial erosion rates on the Iceland landscape throughout the Pleistocene are not well quantified. Ice scour lakes provide an opportunity to investigate glacial erosive activity and relative intensity because they commonly form in areas beneath ice sheets due to intense quarrying. This study evaluates ice scour lake morphology and density as a potential proxy for paleo‐ice flow direction and basal thermal regime for parts of the Iceland Ice Sheet. Using GIS analysis, properties of ice scour lakes are examined in regions that experienced different rates of ice flow during and following the Last Glacial Maximum (LGM), as interpreted from streamlined subglacial landforms. The primary input datasets were topographic, hydrologic and bedrock data. Lake distribution and morphology were quantified for all natural lakes of Iceland (<jats:italic>n</jats:italic> = 30 169), with close examination of three 400 km<jats:sup>2</jats:sup> sub‐regions in Vestfirðir (<jats:italic>n</jats:italic> = 904), Húnaflói (<jats:italic>n</jats:italic> = 69) and Bakkaheiði (<jats:italic>n</jats:italic> = 232). Lake distribution parameters include density, packing and centroid elevation. PolyMorph‐2D was used to quantify lake morphology including orientation, area and elongation ratio. Ice scour lake density, packing and elevation were all greatest on Vestfirðir. The high density and packing of lakes across Vestfirðir suggests unique ice dynamics relative to the other two sub‐regions, and multidirectional flow of lake axes supports the presence of an independent ice cap covering Vestfirðir. Differential intensity of glacial erosion interpreted from regions of high and low lake density on Bakkaheiði supports a proposed ice divide in Northeast Iceland. The orientation of lakes align with the flow directions of proposed LGM ice streams in Northern and Northeast Iceland. Ice scour lakes were most elongate on average on Bakkaheiði, which supports fast ice flow. Improving understanding of former ice sheet basal thermal regime and paleo‐ice flow velocity serves to inform modern controls on ice sheet stability and ice sheet basal processes.</jats:p>

<jats:title>Abstract</jats:title><jats:p>This study assesses the accuracy of the aeolian transport model proposed by van Rijn and Strypsteen in 2020 in predicting sediment transport rates for dune growth, with a focus on the importance of grain‐related shear velocity. A 9‐month dataset of local and regional wind characteristics and dune growth from a new artificial dune with planted marram grass in an environment with minor supply limitations was analysed. The study site is located in Oosteroever, Belgium. The results revealed that utilizing local measured overall shear velocities resulted in significant overprediction of dune volume changes. Incorporating sub‐models for grain‐related bed roughness and shear velocity improved the predictions of dune growth drastically with high statistical results (r<jats:sup>2</jats:sup> = 0.98 and RMSE = 0.64 m<jats:sup>3</jats:sup>/m). The primary driver contributing to dune growth at the study site was due to oblique onshore moderate winds of 10 m/s, as revealed from a frequency‐magnitude analysis. The model could be used with either local wind measurements or regional data transformed to local beach conditions. The study highlights the importance of considering grain‐related shear velocity in future studies to improve the prediction of sand transport rates and enhance our understanding of dune evolution.</jats:p>