Earth Surface Processes and Landforms最新文献

Understanding and predicting bankfull stage is essential for geomorphic analysis, hydraulic modelling and river corridor management, especially regarding floods and connectivity. This study evaluates traditional geomorphic and hydrologic methods and introduces a machine learning (ML) approach to predict bankfull stage along the upper Apalachicola River, Florida, United States. First, we integrated LiDAR point cloud data with a 2010 hydrographic survey through a triangular irregular network (TIN) following coordinate transformation, producing a 1.5-m resolution digital elevation model (DEM) that captures riverbed elevation. After extracting cross-sections, we applied two geomorphic methods, Width-to-Depth Ratio (WDR) and Hydraulic Mean Depth (HMD), and three (1.1-, 1.5-, 2.0-year) hydrologic return intervals to 344 cross-sections to determine bankfull stage and assessed their agreement with visual and field-verified bankfull elevations. A refined HMD method using shape ratio (Rs) and slope inflection corrections improved geomorphic estimates in 131 cross-sections. Bankfull estimates based on return intervals exhibited substantially lower reliability relative to geomorphic methods, with associated confidence levels falling below 70%. This reduced performance is attributable to stage-based spatial averaging and limited sensitivity to local topographic variability. By contrast, the geomorphic methods (WDR and HMD) achieved confidence levels exceeding 95%, underscoring their stronger agreement and robustness. To improve accuracy, we developed ML models: Random Forest (RF), Gradient Boosting (GB) and Ensemble model trained on cross-sectional elevation profiles and engineered features such as cross-sectional area, top width, maximum depth, symmetry, etc. The GB model outperformed all others (R² = 0.94, MSE = 0.21), with feature importance analysis revealing that elevation at the top bank as well as channel area, top width and maximum depth dominated predictions. While this study advances the integration of ML into fluvial systems and provides a replicable framework for large rivers with limited hydrologic data, we recommend that multiple ML models be evaluated across individual reaches to account for the unique geomorphic and hydraulic characteristics of each river reach.

Sediment transport is a key process that strongly influences river morphology but remains difficult to measure and understand, especially during floods in mountainous regions. The paper aims to detect and interpret changes in bedload transport regimes during high-magnitude flood events in an Alpine braided reach (La Séveraisse, French Alps) using continuous seismic monitoring. For the seven investigated floods identified over the 5 years of record, we observe a consistent break in the scaling relationship between the low-frequency seismic power and the high-frequency seismic power, suggesting a change in bedload transport regime linked to sediment mobility. Using time-lapse cameras and hydrological conditions, we find this breakpoint is associated with significant morphological changes occurring at Shields stress ratios approaching a critical value of 2. Based on these results and existing literature, we suggest the break in seismic power corresponds to a transition in bedload regime associated with the disruption of the bed armour layer and particle dynamics being highly influenced by grain–grain interactions. This study demonstrates that changes in sediment transport regime can be accurately identified from seismic observations near rivers, furthering our understanding of the links between sediment transport and channel morphology dynamics.

Desert pavements are a global phenomenon in arid environments, representing one of the most extensive geomorphological and geoecological features on Earth. To a large extent, they determine the interplay of key processes governing current and past landscape dynamics including landform evolution, surface runoff, soil water dynamics, weathering and soil formation, microbial processes, dust deposition and entrainment into the atmosphere. Hence, desert pavements and their future trajectories of change have a strong local to global impact on coupled Earth system components. However, knowledge of the comprehensive role that desert pavements play in the Earth surface–atmosphere system is still limited, and a profound interdisciplinary understanding of their evolution, spatial extent, microbiological processes, and inherent environmental feedback mechanisms is lacking. This article provides an overview of the current state of knowledge of desert pavements as an important Earth system component and offers an interdisciplinary perspective on the key processes interacting within desert pavements, which improves our understanding of the role and importance of desert pavements within the Earth system.

Boulder fields are low-angle, open-work clast accumulations and are among the most distinctive geomorphic expressions of long-term periglacial processes. Although boulder fields are widely used as indicators of past periglacial environments, uncertainty remains regarding the specific climatic conditions and processes responsible for their formation. The Hickory Run Boulder Field (HRBF) in Carbon County, Pennsylvania (41°03′02” N, 75°38′44” W), located ~2 km south of the Last Glacial Maximum margin, is the largest and most striking feature of its kind in the eastern USA, covering approximately 6.5 ha. The dominant hypothesis suggests allochthonous formation, whereby frost wedging of scarp-like bedrock source outcrops and slow downslope movement of weathered material over impermeable permafrost resulted in HRBF's development. However, direct quantitative analyses of this hypothesis remain sparse, and the geological history of HRBF is incompletely resolved. This study presents a sedimentological investigation evaluating the allochthonous hypothesis through a combination of relative weathering indices (clast volume, sphericity, flatness and rebound hardness) and clast macrofabric analysis. Field data were collected from 22 sites along two subparallel transects, including locations in both the major and minor boulder fields. Statistical analyses, including polynomial regression of relative weathering indices and eigenvalue-based macrofabric assessments, reveal dynamic spatial trends in clast weathering and orientation. Results indicate systematic increases in clast weathering with distance from a local bedrock outcrop and non-random macrofabric orientations consistent with mass movement. These findings confirm that HRBF represents a time-transgressive surface formed under periglacial conditions, with flow-like integration of clasts from bordering upslope areas. The study provides quantitative evidence supporting emplacement by periglacial mass movement, reinforcing the utility of HRBF in paleoclimatic reconstructions of the Appalachian Highlands.

Excessive fine sediment (particles <2 mm) in riverbeds negatively impacts river ecology. Riverbed fine sediment measurements are therefore critical in research, monitoring and management seeking to protect, maintain or restore riverine ecosystems. However, there is no single, widely adopted method and limited evidence-based guidance about how to choose between numerous available field techniques to achieve accurate, repeatable and consistent results. We therefore compared the intercorrelations of six commonly employed fine sediment methods across 29 sites (constituting 667 independent observations): the original resuspension method and two alternative turbidity derivatives (turbidity tube and turbidimeter), Wolman pebble counts, McNeil sampling and visual estimations at reach and patch scales. Performance evaluation focused on issues of practical significance, including comparisons of fines content between surface and subsurface measures, local substrate composition, spatial scale of application (reach and patch) and sample replication. Most methods yielded estimates of fines that were strongly correlated with each other, but these differed depending on local substrate composition, suggesting that different methods are better applied to certain substrate types. Differences between reach fine sediment estimates were typically larger as the proportion of fine sediment increased, whilst the converse was true for patch-scale measures. On average, surface measures do not provide reliable information about subsurface fines content. We also found that an inexpensive, rapid version of the resuspension method utilising a turbidity tube performs as well as costlier alternatives, providing a valuable means of estimating fines in most riverine environments. The spatial scale of sampling (reach or patch) and the number of replications made a significant difference to the estimates obtained using visual observations. We make pragmatic recommendations, providing a significant step forward in standardising fine sediment measurement in riverbeds. Practitioners and researchers should select methods that suit local substrate conditions, while recognising that their choices will influence the results obtained.

Forest blowdown, or the widespread felling and snapping of trees due to high wind speeds, can substantially increase the amount of downed large wood (LW) on the landscape. Despite high recruitment potential, few studies have investigated the influence of blowdown on in-channel LW volumes and the subsequent capacity for sediment and water storage. In June 2021, a frontal storm caused widespread blowdown across parts of southeastern Australia, creating an opportunity to better understand interactions between landscape morphology, blowdown intensity, large wood recruitment and in-channel hydrogeomorphic changes. Blowdown area and density (trees per unit area) were mapped remotely across the Wombat State Forest (WSF), Victoria and paired with field-based measurements of in-channel LW and associated sediment and water storage in the Lerdederg River and tributaries. Study reaches were characterized by a range of hillslope gradients, aspects, blowdown intensity and channel and floodplain widths. Eleven percent of the treed area of the WSF was blown down by the June 2021 storm, with winds that exceeded 100 km/hr from a non-typical direction. The blowdown event was the dominant source of in-channel LW, delivering 88% of the volume. LW volumes were more strongly influenced by valley morphology, particularly valley bottom width, than blowdown characteristics (affected area or downed wood density). Most LW (85% by volume) accumulated in porous jams, and about 33% of LW stored sediment and/or water, with storage more likely behind pieces that touched the channel bed. Substantial amounts of LW still remained on the floodplain or spanned above the channel, suggesting that LW loads attributed to the June 2021 storm could continue to increase as overbank flows and wood decay continue to recruit wood into the active channel. Catastrophic blowdown like the June 2021 storm could exert significant control on the wood regime and morphology of forested, headwater channels, particularly as extreme wind events are expected to increase in magnitude and severity in the future.

This study developed a thermosensitive shear zone material composed of paraffin-quartz sand-clay composites. By constructing artificial shear zones with this material and selectively activating embedded electric heating plates to generate localized shear strength reduction, experimental simulations of both retrogressive and translational landslides are achieved. The results demonstrate that the mechanical parameters of this material exhibit temperature-dependent degradation: cohesion (c) follows a negative exponential decay with temperature increase, while the internal friction angle (φ) decreases linearly. The thermally induced shear strength reduction progressively diminishes the anti-sliding capacity of slip surfaces, ultimately triggering gravity-driven landslide deformation and failure. During testing, tensile cracks initiated at the slope rear edge, with internal deformations dominated by extensional mechanisms. PIV displacement monitoring revealed steep displacement gradient transitions spatially coinciding with tensile crack development. For translational landslides, earth pressure variations in shallow, mid-depth and deep zones displayed synchronized reduction patterns throughout deformation. In contrast, retrogressive landslides exhibited distinct phase differences in earth pressure evolution across depth zones, with the frontal slope's traction effect on the rear being substantially weaker than that of the central part. This research establishes an innovative methodology for simulating landslide disasters through controlled internal weakening of shear zones, which may provide new insights into failure mechanisms and prediction techniques driven by shear strength deterioration.

Foreland basins are elongate depressions that develop around the flanks of collisional mountain ranges. Rivers are key agents that shape their landscape geomorphology and evolution. Their upstream headwater areas are geomorphologically dynamic locations prone to drainage network reorganisations via headward erosion by the foreland axial river. They are complex areas to investigate due to geological complexity, the absence of fluvial deposits and long timescales over which drainage evolution occurs. In this study, we examined the Zadorra River, a headwater tributary to the Ebro River that preserves a diverse number of different geomorphological features that record long-term drainage evolution. Four key sectors with different surface configurations and topographic characteristics were identified. We have used surfaces (erosional, depositional and composite) in combination with topographic metrics (longitudinal profiles, hypsometry and drainage divide analysis) to understand the patterns and timing of fluvial incision linked to incision wave propagation and headwater drainage integration by the Mediterranean draining Ebro River. The study describes the drainage evolution of the Ebro headwaters, beginning with the transformation of internally drained basins into east- and south-directed tributaries. The paleo-Arakil River, closer to the advancing Ebro headwaters and Mediterranean divide, was integrated first through headward erosion, while the more distant proto-Zadorra River was integrated later. This spatial and temporal shift focused subsequent drainage evolution on the proto-Zadorra, whose northward erosion captured and beheaded the paleo-Arakil, forming the modern Zadorra-Ebro and Arakil-Ebro tributaries. Geological evidence and fluvial terraces indicate this headwater drainage integration spanned from the Miocene to the Quaternary and will continue northward in the future. The study highlights the geological and geomorphological complexity of foreland basin headwater regions and their interplay for drainage expansion and integration.

Active potential landslides pose substantial threats to lives and property in alpine-canyon terrain worldwide. Identifying landslide-prone areas and assessing the failure likelihood of potential landslides are crucial for risk mitigation. However, uncertainties from incomplete inventories and variable data quality limit the reliability and practical application of landslide hazard assessments. This study proposes a novel metric method to assess potential landslide hazard in alpine-canyon regions by integrating the advanced observation capability of remote sensing techniques and reliability of geomorphic surveying. A comprehensive inventory of potential landslides was established via multi-temporal interferometric synthetic aperture radar (InSAR) mapping of the eastern Qinghai–Tibet Plateau, with landslide types classified based on their material compositions and movement characteristics. The observed time-series displacements and geomorphological deformation features indicate the progressive creep behaviour of landslide movement, reflecting the different hazard levels of potential landslides across their multiple stages of development. The dynamic trends of most potential landslides are characterised by seasonal accelerating creep and geomorphic movement features that range from localised to intense deformation. The hazard assessment demonstrates that 23.7% of potential landslides have reached or exceeded the high hazard level, with most of these having large and deep characteristics, and closely related to active fault zones in the study area. Internal geological conditions and fluctuating precipitation commonly elevate the landslide hazard level in critical regions. This integrated analysis of the dynamic evolution of potential landslides and geomorphic deformation features improves hazard prediction for landslides in mountainous regions undergoing long-term creep.

To understand the relationship between variable flood flow and channel width of the Jamuna River, we developed a five-decade-long, nearly annual temporal resolution delineation of channel width from analysis of satellite imagery and compared this with a daily discharge time series. We show narrow channel conditions in the 1970s and early 1980s, rapid widening in the late 1980s through early 1990s, and a period of channel narrowing since about 2010 that corresponds to decadal-scale shifts in the hydroclimate. We identify the maximum 91-day average discharge for the single previous season's monsoon flood, the average of which is approximately the long-term geomorphically effective discharge for the river, as a strong control over channel width. This empirically determined relation closely fits a hydraulic geometry prediction of active channel width for the discharge divided into three to five principal anabranches. We also show that the inherited width (the width from 1 year previous) and the intensity of revetments explain some variability in the observed channel width. This analysis outlines a compelling alternative hypothesis to the dominant narrative that Jamuna River widening was a response to the Great Assam Earthquake sediment wave. These findings have major implications for ongoing efforts to understand and manage morphodynamically active rivers around the world: they suggest researchers and managers in such environments must consider the potential effects of variable hydroclimate on channel morphology over annual to decadal timescales. Of course, they are also especially relevant to the management of the Jamuna River, where these findings suggest efforts to reclaim land and return the channel to narrower widths observed in the 1970s, a period of notably low flood flows, may increase flood risk by increasing exposure of densely settled areas to channel migration and related embankment-failure flood hazards in wetter hydroclimate periods resulting from natural variability or climate change.