Search Results (155)

The Middle Triassic Tredian Formation of the Salt Range, Pakistan, consists of sandstones with interbedded shale in the lower part and minor dolomite in the upper part. Conventional grain-size analysis has been widely used as a sedimentological tool to elucidate depositional environments and the mode of transportation of detrital sediments. This study presents the first integrated application of a Decision Tree Classifier (a machine learning model) with field and petrographic evidence to interpret grain-size statistics for the analysis of depositional environments of the Tredian Formation in the Salt Range, Pakistan. Stratigraphic sections of the Tredian Formation were measured and sampled in the Nammal Gorge and Zaluch Nala in the Salt Range for detailed sedimentological and grain-size analyses. The lower part of the Tredian Formation (Landa Member) consists of interbedded sandstone and shale (LF-1) characterized by large-scale slumps, parallel lamination, ripple marks, and cross-bedding. The LF-1 is overlain by the Katkhiara Member, which is dominated by thick sandstone (LF-2) with planar and trough cross-bedding and contains dolomite beds (LF-3) in the upper part. Grain-size statistics show that the sandstones are fine-to-medium-grained, well-to-very-well-sorted, near-symmetrical, and very platykurtic. Machine learning-based bivariate plots suggest that most of the samples are grouped, with some showing scattered trends. The Linear Discriminant Function (LDF) analysis indicates that the Tredian Formation was deposited in fluvial–deltaic to shallow marine environments with sand reworking and redistribution under aeolian/beach settings. The Decision Tree Classifier Model (DTCM) predicted fluvial to shallow marine depositional environments for the Tredian Formation and shows strong agreement with field-based lithofacies interpretation, demonstrating its reliability as a predictive tool. Thus, the present study demonstrates that integrating grain-size-based machine learning and statistical analysis with traditional sedimentology provides valuable insights into depositional settings and enhances the reliability of interpretations of ancient sedimentary environments. Full article

Today’s fluvioscape of the Hessische Ried (Upper Rhine Graben) is the consequence of human intervention on the natural drainage system that has transformed a large floodplain into an intensively used cultural landscape. Already, the Romans carried out river regulation and water management to guarantee the transportation of material and troops, securing the territory of the Roman Empire. To secure the so-called Rhein-Limes, burgi (fortlets) were constructed along small tributaries of the River Rhine under Valentinian I. (364–375). The burgus at Trebur-Astheim represents such a military site. It is located at the Schwarzbach/Landgraben fluvial system, which was actively used as a waterway and connected important military sites such as the castra “Auf Esch” (Groß-Gerau) with the River Rhine and, thus, with the provincial capital Mogontiacum (Mainz). Using a combination of magnetic gradiometry, frequency domain electromagnetic induction (FDEMI), electrical resistivity tomography (ERT), direct push-sensing (DP), and sediment coring, we were able to detect a 15 m wide and 2.5 m deep Roman canal between the burgus at Trebur-Astheim and the River Rhine, opening the Hessische Ried hinterland to wider trade routes. Radiocarbon dating further reveals that after a final re-excavation, the channel started to silt up in the 7th/8th century AD and finally fell out of use. This last period of use may be associated with the activities of the Carolingian Königspfalz (royal palace) Trebur. Our study shows that the fluvioscape of the Hessische Ried dates back to Roman times and that the canal at Trebur-Astheim is one of the few navigable canals known to have existed north of the Alps during the Roman period and the Early Middle Ages. Full article

The interaction of emergent vegetation and three-dimensional (3D) bedforms is essential for understanding turbulent flow dynamics in curved channels. A laboratory investigation can help to collect required data under controlled conditions. Experiments were conducted in a 9.5 m-long, 0.9 m-wide recirculating flume incorporating a 90° bend and a sculpted 3D pool bedform. Artificial rigid vegetation, designed to replicate the hydraulic behavior of natural emergent plants, was installed along both sidewalls. Instantaneous three-dimensional velocities were recorded using an acoustic Doppler velocimeter (ADV) across multiple cross-sections under both bare-bed and vegetated conditions. The results reveal that emergent vegetation markedly increases flow resistance, distorts mean velocity distributions, and suppresses the classical logarithmic velocity profile, particularly within the bend and pool regions. The combined presence of vegetation and the 3D pool bedform amplified turbulence intensity, elevated Reynolds shear stresses, and redistributed turbulent kinetic energy (TKE), which increased by up to sevenfold from the bend entrance to its exit. In vegetated pool sections, Reynolds stresses were approximately 12% greater than under bare-bed conditions, underscoring the synergistic effects of vegetation drag, secondary circulation, and flow separation in producing anisotropic turbulence. These findings highlight the importance of incorporating vegetation–bedform interactions in fluvial modeling frameworks, with significant implications for sediment transport prediction, channel stability evaluation, river restoration, and aquatic habitat design. Full article

Mid-channel bars are fundamental fluvial geomorphic units that regulate sediment transport, channel stability, and riparian ecosystems, and their spatiotemporal evolution provides critical insights for sustainable river management. This study examines the structural reorganization and migration dynamics of mid-channel bars along the mainstem of the transboundary Yalu River using multi-temporal Sentinel-2 imagery acquired in 2019, 2022, and 2024. An automated extraction framework combining a dense atrous U-Net (DA-UNet) with multispectral indices was developed to robustly identify mid-channel bars under complex water–land transition conditions. Based on the extracted results, changes in bar number, area, size composition, morphological characteristics, and centroid migration were systematically analyzed. The results reveal a pronounced reorganization of mid-channel bars systems over the study period: although the number of bars increased from 111 to 136, the total area decreased from 168.97 km² to 165.00 km², indicating a transition from a “few-large” to a “many-small” configuration. Size-based analysis further shows an increase in small and medium bars, while large bars remained relatively stable, leading to a more differentiated multi-scale structure. These findings highlight the effectiveness of integrating multi-temporal remote sensing and deep learning for long-term monitoring of geomorphic dynamics and provide scientific evidence to support sustainable river regulation and transboundary watershed management. Full article

Understanding landform evolution is essential for assessing how terrain responds to geomorphic drivers such as weathering, fluvial erosion, hillslope processes, and tectonic uplift. This is particularly important in applications such as constructed post-mining landform rehabilitation, where predicting long-term erosional stability is vital for sustainable closure planning. In addition to long-term average erosion rates, the spatial patterns of gullies, rills, and channels are critical for assessing landform stability. This review examines Digital Elevation Model (DEM)—driven, process-based Landform Evolution Models (LEMs), with a primary focus on SIBERIA, CAESAR-Lisflood, and SSSPAM, which are widely used to evaluate the erosional behaviour of constructed post-mining landforms, each with distinct characteristics. These models are systematically compared in terms of input requirements, process representations, parameterisation, and predictive capabilities. Recent advances in high-spatial resolution DEMs (e.g., LiDAR, SRTM), along with digital soil and rainfall databases and satellite-derived vegetation indices, have improved the parameterisation of erosion, hydrological, and sediment-transport processes of the LEMs. A brief comparative case study is presented to demonstrate how these LEMs simulate 1000-year erosional behaviour along a linear hillslope. This review synthesises the current capabilities and limitations of DEM-driven LEMs, providing guidance for researchers, land managers, and practitioners in selecting appropriate models to support sustainable post-mining landform management, as well as outlining potential future advancements. Full article

Tributary-to-mainstem discontinuities (TMDs) are understudied, but are likely common in river networks, arising from abrupt transitions in stream order and dominant ecological factors. We present a conceptual model of aquatic macroinvertebrate (AMI) TMD directionality and relative magnitude by contrasting the impacts of hydrography, geochemistry, and sediment transport on tributary-related channel-floor precipitate cementation and the mainstream embeddedness (burial) of channel-floor substrata in fine sediment. We test that model using AMI assemblage density/m², species richness/sample, and diversity data from 24 tributaries confluent with the regulated Colorado River in Grand Canyon through pairwise and multivariate analyses of long-term discharge records and substrate and water-quality data in three habitats: tributaries, their confluences, and adjacent mainstream habitats. Mean AMI density decreased 2.7-fold from low to high cementation, 6.1-fold from low-to-high embeddedness, and 136.0-fold across combined gradients. We also analyzed pre-dam aquatic insect literature, finding that TMDs were naturally common in Glen Canyon upstream but were more strongly tributary-positive (discontinuity magnitude, D_mag = 0.62 in pre-dam Glen Canyon) compared to tributaries in the post-dam Grand Canyon (D_mag = 0.31). We conclude that, depending on D_mag directionality, tributary confluences can function as hotspots or barriers to AMI assemblage development. Our results demonstrate that TMDs are and were common in the contemporary regulated and natural unregulated Colorado River corridor, and we expand the concept of biotic discontinuity to improve understanding of fluvial ecosystem ecology and constraints on river and dam management. Full article

Sediment transport in alluvial channels is strongly controlled by the grain-size distribution of bed and suspended materials. This, in turn, influences river morphology by modifying the cross-sectional area and course of the channel. Statistical parameters such as mean, standard deviation, skewness, and kurtosis provide quantitative indicators of the energy conditions that control sediment transport and deposition. This study examines the depositional characteristics of sediments in the Ganga River in Varanasi City, India, employing a novel combination of linear discriminant function (LDF) and sediment transport index (STI). The LDF results reveal distinct depositional environments: Y₁ and Y₂ values indicate deposition in a low-energy fluvial environment similar to beaches, Y₃ values suggest shallow marine settings, and Y₄ values point to mixed deltaic and turbid current depositional environments. Additionally, CM diagrams show rolling and suspension as the dominant sediment transport mechanisms. Shear stress analysis combined with STI highlights significant depositional features, with minimal erosion observed throughout the study area. The study provides an operational framework for mapping erosion-deposition patterns on alluvial point bars that are transferable to other sand-bed rivers worldwide where detailed hydraulic data are limited but detailed grain-size and DEM information are available. Full article

This study provides a seasonal and cross-shore characterization of sediments along the Ferrara coastal area (Italy). Four sites (Goro, Volano, Estensi, and Spina) were investigated through an integrated approach including textural and geochemical analyses. Surface sediments were sampled seasonally from summer 2023 to summer 2024 and analyzed to determine granulometry, major oxides composition, carbonate content, and potentially toxic element (PTE) contents. Results revealed that both grain-size and geochemistry vary seasonally and along the cross-shore profile, reflecting the combined effects of hydrodynamic forcing, sediment transport, and fluvial inputs. Elevated contents of Ce, Cr, La, V, and Zr were detected at various sites, seasons, and geomorphological zones. In some cases, the environmental quality indices applied allowed the sediments to be classified as polluted. Furthermore, some exceedances of the legal limits for Cr and V contents were observed at Goro and Volano. These pollution levels are attributable to the presence of PTE-bearing minerals originating from the source basins (geogenic sources). Overall, the results highlight the interplay between hydrodynamics and sediment provenance, emphasizing the dominance of geogenic contributions along the northern Adriatic coast, providing updated geochemical data for future monitoring and environmental management of coastal systems. Full article

The wandering reach of the Yellow River has long been a pivotal area of research due to its drastic fluctuations in water-sediment dynamics, frequent shifts in the main channel, and complex river regime evolution. Studies on the main-channel morphological evolution in this reach have focused on the analysis of parameters related to the overall oscillation or have only analyzed a certain reach within the wandering reach, with a lack of detailed studies based on the different characteristics of each area. Therefore, taking the Xiaolangdi Reservoir–Gaocun reach as the research area, by constructing a two-dimensional water-sediment dynamic model, the erosion–deposition characteristics of different sub-reaches and the morphological evolution characteristics of key cross-sections were quantified and analyzed. Based on measured hydrological, sediment, and topographic data, the temporal and spatial changes in the bankfull area and fluvial facies coefficient of typical sections before and after the construction of Xiaolangdi Reservoir were analyzed. By interpreting remote sensing images, the spatio-temporal variation characteristics of the migration distance and bending coefficient of different reaches before and after the construction of Xiaolangdi Reservoir were calculated, and the key factors influencing the evolution of river morphology parameters were identified. The results showed that after the Xiaolangdi Reservoir operation, the overall erosion of the Huayuankou–Jiahetan reach is greater than the deposition, and the erosion is more obvious in dry years. The river course direction and control engineering play a significant role in controlling the morphological evolution of the main channel during the process, causing the R2 reach to significantly swing to the north bank and the R3 reach to the south bank. When the sediment transport coefficient values were between 0 and 0.005 kg.s.m⁻⁶, water-sediment had a positive effect on shaping and evolving the main-channel morphology. The long-term low-sand discharge of Xiaolangdi Reservoir and the continuous improvement of river regulation projects are the main reasons for the above changes. The results can provide support for controlling the evolution of the main channel and improving river regulation projects. Full article

This study investigates the morphometric and anthropogenic controls governing the occurrence and spatial distribution of tributary–junction fans (TJFs) along the Chaudière River, Québec, Canada. Using GIS-based morphometric analysis, field validation, and multivariate statistics (PCA, CART, LDA), 142 tributary watersheds were analyzed, of which 41 display fan-shaped depositional features. Basin relief, drainage density, contributing area, and slope–area coupling emerge as the dominant predictors of TJF development, delineating an intermediate energy domain where sediment supply and transport capacity become balanced enough to allow partial geomorphic coupling at confluence nodes. CART analysis identified approximate slope and area thresholds (slope < 9°, area > 20 km²; 66% accuracy), while LDA achieved 76%, indicating that morphometry provides useful but incomplete predictive power. These moderate performances reflect the additional influence of event-scale hydrological forcing and unquantified Quaternary substrate heterogeneity typical of postglacial terrain. Beyond morphometry, anthropogenic disturbance exerts a secondary but context-dependent influence, with moderately disturbed watersheds (10–50% altered) showing higher frequencies of fans than both highly engineered (>50%) and minimally disturbed (<10%). This pattern suggests that land-use modification can locally reinforce or offset morphometric predisposition by altering sediment-routing pathways. Overall, TJFs function as localized sediment-storage buffers that may be periodically reactivated during high-magnitude floods. The combined effects of basin geometry, land-use pressures, and hydroclimatic variability explain their spatial distribution. The study provides an indicative, process-informed framework for evaluating sediment connectivity and depositional thresholds in cold-region fluvial systems, with implications for geomorphic interpretation and hazard management. Full article

Microplastic pollution in riverine ecosystems poses critical environmental challenges, yet current modeling approaches inadequately capture the spatial heterogeneity and topological complexity of fluvial systems. This study develops an innovative spatiotemporal graph convolutional network (ST-GCN) framework that integrates hydrological connectivity, flow parameters, and microplastic characteristics for simultaneous migration pathway identification and pollution source tracing. This model constructs multi-scale graph representations encoding system structure and transport dynamics, implements spatial-temporal convolution layers with adaptive attention mechanisms, and employs a backpropagation-based algorithm for inverse source identification. Validation using 18 months of field observations from 45 monitoring nodes across a 127 km river reach demonstrates 87.3% pathway prediction accuracy and 94.3% source localization accuracy (R² = 0.841, p < 0.001), representing substantial improvements over conventional advection–diffusion models. The framework successfully identified three pollution sources during a real contamination incident within 6 h of detection, enabling rapid regulatory intervention. This research advances environmental modeling by demonstrating that graph neural networks effectively capture transport processes in networked hydrological systems, providing practical tools for watershed management and evidence-based pollution control decision-making. Full article

Salinization in the western Songnen Plain has limited regional ecology and land use for decades, with its primary cause closely tied to sediment transport. To elucidate sediment evolution and its role in soil salinization, a borehole from saline-alkali land in Taonan County, west of the Songnen Plain, was investigated within an AMS¹⁴C, OSL, and ESR dating framework. Grain size analysis, end-member modeling, and major-element geochemistry revealed four transport components—fluvial, aeolian, glacio-fluvial, and lacustrine. Five provenance stages from the late Early Pleistocene to the Early Holocene were found: (1) distal weathered volcanic rock transport with minor fluvial–alluvial input; (2) proximal alluvial–proluvial transport; (3) ice meltwater and wind-driven transport; (4) predominantly wind transport; and (5) renewed fluvial–proluvial transport. These shifts correspond to regional paleoclimate fluctuations driven by global ice volume cycles, which control sediment supply, hydrology, and consequently salt accumulation in warm humid periods and upward salt migration in cold dry periods. The findings of this study demonstrate that Pleistocene glacial–interglacial climate cycles are the dominant driver of sediment transport and salinization dynamics on the western Songnen Plain. Full article

The mineralogical, geochemical, and statistical characteristics of recent fluvial deposits from the Brahmaputra–Jamuna River, Bangladesh, were examined to determine their provenance, transport dynamics, and depositional environment. Sediments were analyzed using X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WD-XRF), field emission scanning electron microscopy (FE-SEM), and electron probe microanalysis (EPMA). Grain size analysis revealed a predominance of medium-to-fine sand (mean grain size 1.77–3.43 ϕ), with moderately well-sorted textures (sorting: 0.33–0.77 ϕ), mesokurtic to leptokurtic distributions, and skewness values ranging from −0.21 to +0.30. Mineralogical results show a high quartz content with minor feldspar, mica, zircon, rutile, and iron-bearing minerals. Geochemical data indicates high SiO₂ (63.39%–70.94%) and Al₂O₃ (12.25%–14.20%) concentrations and calculated chemical index of alteration (CIA) values ranging from 60.90 to 66.82. The microstructural study revealed angular to sub-angular grains with conchoidal fractures and stepped microcracks, indicating brittle deformation under high-energy conditions, which is consistent with short transport distances, limited sedimentary recycling, and a derivation from mechanically weathered source rocks. Multivariate analyses (PCA and K-means clustering) of grain size parameters reveal two distinct sedimentary regimes, namely Cluster 1 as finer-grained (2.36 ϕ), poorly sorted sediments, and Cluster 2 as coarser (2.98 ϕ), well-sorted deposits. Discriminant function values (Y₂: 78.82–119.12; Y₃: −6.01 to −2.56; V₁: 1.457–2.442; V₂: 1.409–2.323) highlight shallow water, fluvial/deltaic aspects, and turbidite depositional environments. These findings advance the understanding of sedimentary dynamics within large, braided river basins and support future investigations into the sustainable management of fluvial depositional environments. Full article

The Late Holocene flood history of the Cauvery River floodplain in the Poompuhar region was reconstructed using a multiproxy sedimentological approach applied to three trench cores. Lithostratigraphy, loss on ignition (LOI), magnetic susceptibility (MS), sand–silt–clay textural analysis, granulometric statistics (Folk and Ward), Passega CM diagrams, and grain angularity provide complementary evidence to differentiate high-energy flood deposits from background slackwater sediments. Grain-size processing and statistical analyses were carried out in R using the G2Sd package, ensuring reproducible quantification of mean size, sorting, skewness, kurtosis, and transport signatures. We identified 10 discrete high-energy event beds. These layers are characterised by >80% sand content, low LOI (<3.5%), and low frequency-dependent MS (χfd% < 2%), confirming rapid, mineral-dominated deposition. A tentative chronology, projected from the regional aggradation rate, suggests two major flood clusters: a maximum-magnitude event at ~3.2 ka and a synchronous cluster at ~1.6–1.8 ka. These events chronologically align with the documented phases of channel avulsion in the adjacent Palar River Basin, supporting the existence of a synchronised Late Holocene climato-tectonic regime across coastal Tamil Nadu. This hydrological evidence supports the hypothesis that recurrent high-magnitude flooding triggered catastrophic channel avulsion of the Cauvery distributary, leading to the fluvial abandonment and decline of the ancient port city of Poompuhar. Securing an absolute chronology requires advanced K-feldspar post-IR IRSL dating to overcome quartz saturation issues in fluvial deposits. Full article

Particle shape analysis is essential in sedimentological research, as it offers vital insights into the sedimentary environment and transport history. However, little is known about the particle shape variation across different sand fractions, as well as the differences between particle shape data based on volume and number weighting. In this study, we investigate the grain shape variation of different sand-sized particles (fine, medium, and coarse sand fractions) in aeolian dune (11 samples) and lake beach (12 samples) environments around Poyang Lake, China, using dynamic image analysis (DIA). The shape data results based on both volume-weighted and number-weighted methods reveal significant differences in shape parameters (circularity, symmetry, aspect ratio, and convexity) among different sand fractions, especially between coarse and fine sand. This highlights the critical need for size-fractionated analysis when employing particle shape as an environmental discriminant. By integrating 86 sets of published particle shape data from different depositional environments, we found that volume-weighted shape data has limited ability to differentiate beach and dune sands, although it distinguished the fluvial, desert dune, and coastal beach sand well. In contrast, number-weighted shape data effectively distinguished the beach and dune sands, as fine sand particles are typically transported in suspension during fluvial processes and in saltation during aeolian processes. This demonstrates the role of integrating both volume-weighted and number-weighted shape data in future studies to accurately distinguish sedimentary environments. Full article