Search Results (3,953)

Aeolian sand bodies unrelated either to coastal barrier systems of Holocene or earlier age or to modern beaches have been identified along the central New South Wales coast of southeast Australia. Some of these deposits cap headlands or are located above high sea-cliffs. Others lie below modern sea-levels, whilst one substantial dune field extends 12 km inland. Many of these have previously been interpreted as Early Holocene cliff-top dunes, the product of the migration of beach sands up aeolian sand ramps at the foot of the sea-cliffs of the region and onto the cliff tops. The rising sea-levels of the Middle Holocene eroded the ramps and cut off the supply of sand to the dunes, allowing them to stabilise. But re-investigation shows that these dune fields accumulated at times of low Quaternary sea-levels, with a particle-size distribution suggestive of an inland rather than a coastal origin. We therefore propose an alternative model for the accumulation of these features. At times of low sea-level, sediments exposed on the inner shelf were reworked onto the adjacent coast by onshore winds, where they accumulated in locations unconnected to the modern or the earlier Holocene coastal aeolian sedimentary regime. This model challenges the conventional story that the dominant glacial maximum winds across southeastern Australia were from the west (and thus offshore). This pattern of sediment accumulation and its associated wind regime may have been more stable (continuing for over 30 000 years) and more long-lived (repeated through at least the last two glacial cycles) than has previously been believed. Although the cliff-top dune model has been widely applied, we question its suitability in its type location and suggest a more cautious approach to its application elsewhere. We argue that the products of the landward aeolian reworking of sediment exposed on the continental shelf have been overlooked, despite their potential for the preservation of long-term environmental records. Full article

The present work focuses on the investigation of the turbulent Reynolds number effect on the characteristics of an open-channel flow with sediment transport, by employing the micropolar model. The micropolar model is essentially a Eulerian non-Newtonian model that has already been proven to correctly describe the secondary phase of turbulent wall-bounded flows. The current under investigation geometry, open channel, comprises an ideal candidate to further test the characteristics of the micropolar model as many environmental flows contain a secondary phase. Such flows are of great engineering and physics interest for applications such as sedimentation transport and debris flow. Direct Numerical Simulations (DNSs) have been carried out on an open channel for three different turbulent Reynolds numbers. The simulated results are compared against previous DNS data of similar flows. The micropolar model is capable of describing the same problem but in a Eulerian frame, thus significantly simplifying the computational cost and complexity. Full article

Sediment deposition in water diversion channels threatens the operational safety and water supply reliability of large-scale inter-basin water transfer projects. This study investigates the deposition patterns and sediment reduction strategies for the diversion channel of the Shigu Water Source Project, a key intake hub of the Central Yunnan Water Diversion Project on the Jinsha River. A one-dimensional total-load sediment mathematical model (HELIU-2) was used to simulate deposition volume, particle size distribution, and sediment concentration at the pumping station intake under eight design scenarios spanning high-, medium-, and low-sediment years. Results show that over 95% of the deposited sediment in front of the pumping station is finer than 0.05 mm. Dredging reduces the deposition thickness at the pump intake by 13–25% in high-sediment years, significantly enhancing sediment trapping efficiency and reducing both average and maximum sediment concentrations. Longer diversion channels increase total deposition by 9–13% but reduce intake sediment concentration by 2–5% and decrease local deposition thickness by 27–42%, especially in high-sediment years. These findings provide quantitative support for optimizing desilting basin layout, channel length design, and dredging schedules. The proposed modeling framework and mitigation strategies may provide a reference for other large-scale water diversion systems facing similar sedimentation challenges. Full article

Introduction: The tub gurnard (Trigla lyra) is a demersal species of commercial interest whose long-term distributional dynamics remain poorly understood. Understanding spatial and temporal changes is essential for fisheries management and for assessing biogeographic shifts. Objective: To characterise the spatio-temporal distribution and persistence of T. lyra across Galician and Cantabrian Sea waters over a 33-year period (1993–2025) and to identify environmental and fishing drivers associated with observed changes. Methodology: We analysed data from the DEMERSALES bottom trawl survey series (1993–2025), for which the sampling design remained consistent throughout. Species distribution was modelled using a delta–GAM framework (presence–absence and positive values), complemented by a presence-only GAM fitted to Vessel Monitoring System (VMS) data; because these data were only available for 2009–2023, this model was restricted to that period for biological coherence. Environmental predictors included bathymetry, slope, sediment composition (organic matter, mud, fine and coarse sand), bottom temperature, and salinity. Spatial structure was assessed using aggregation curves, occupied area, centre of gravity, a Space Selectivity Index, and an Index of Persistence. Results: The occupied area increased from 45 to 963 km² (+2040%), accompanied by a sustained decline in the Space Selectivity Index and a westward shift of the distributional centroid (~20 km), indicating progressive range broadening. The frequency of occurrence rose from 4.5% in 1993 to 87.7% in 2025, reflecting a marked increase in spatial occupancy and encounter probability. Abundance increased sharply after 2015 (+47%), consistent with strong positive year effects in the GAM. Higher occurrence and densities were associated with muddy substrates, intermediate to high organic content, and depths of 100–300 m, matching the stable aggregation cores found along the shelf break. A reduction in trawling effort (−38% in mean intensity, −17% in swept area over 14 years) likely facilitated these trends. Conclusions: T. lyra expanded its distribution and shifted westward between 1993 and 2025, with persistent aggregation cores on the shelf break. No significant effect of temperature was found, suggesting that climate warming is not the primary driver; the expansion appears most plausibly to have been favoured by the decline in fishing pressure. Full article

Seagrass meadows are important blue carbon habitats, but their patchy distribution in intertidal zones makes accurate UAV mapping difficult under shallow water cover and complex sediment backgrounds. This study developed a fine-grained semantic segmentation framework with explainability analysis to improve intertidal seagrass extraction from high-resolution UAV visible and multispectral imagery. Exposed seagrass (ESG) and shallow-submerged seagrass (SSG) were mapped separately to represent two observable intertidal states. Visible bands, multispectral bands, and vegetation indices were used as model inputs. U-Net and DeepLabV3+ served as baseline models, while UPerNet-ConvNeXtV2-Tiny was tested under the same settings. Kernel SHAP and permutation importance were used to assess feature contributions. UPerNet-ConvNeXtV2-Tiny achieved the best performance, with an overall accuracy (ACC), mean Intersection over Union (mIoU), and F1 score of 97.45%, 94.63%, and 97.23%, respectively. It outperformed the baseline models in suppressing background interference, preserving patch morphology, and reducing omission errors in weak response and boundary areas, while demonstrating better cross-scenario applicability in independent test areas. Explainability analysis showed that model discrimination was mainly associated with red and green-related features, especially RGB-R, MS-R, MS-G, RGB-G, and NGRDI. ESG and SSG showed different feature dependence patterns, indicating that high-resolution UAV imagery can support accurate seagrass mapping and reveal spectral differences between intertidal seagrass states. These findings provide a practical framework for UAV-based intertidal seagrass mapping and monitoring and offer guidance for feature selection and model explainability analysis. Full article

Deep-water gravity flow deposits constitute a critical frontier in global hydrocarbon exploration, and characterizing flows controlled by complex topography remains a significant challenge. Focusing on the Cretaceous Pointe Indienne Formation in the Lower Congo Basin, West Africa, this study systematically investigates the depositional characteristics, flow types, vertical sedimentary sequences, and depositional models of lacustrine gravity flows, based on newly acquired drill core data, analytical test results, and three-dimensional seismic interpretation from the study area. Three major gravity flow types are identified in this study: sandy debris flows, muddy debris flows and turbidity currents. Meanwhile, we highlight the critical roles of slide–slump deposits and contour currents in deep-water depositional evolution, which further clarifies the sedimentary characteristics, vertical facies association patterns and spatial distribution of the Pointe Indienne Formation. Based on these results, we construct a stepped-slope depositional model for lacustrine rift basins. This “stepped-slope-controlled gravity flow” model describes the evolution of sediment transport from high-density, block-based processes (slides/debris flows) to low-density turbulent processes (turbidity currents). Beyond explaining the geological features of sub-salt gravity flow deposits in the Lower Congo Basin, this model improves the accuracy of predicting deep-water gravity flow sand body distribution in lacustrine basins with analogous structural and topographic settings, providing robust geological and theoretical support for hydrocarbon exploration in similar regions. Full article

Introduction: Establishing baseline descriptions of inorganic elements in the early life stages of sharks and in their respective nursery areas is essential for assessing anthropogenic impacts and supporting conservation strategies. Objectives: This study presents the first baseline of plasma trace element concentrations (Al, Zn, As, Cu, Cr, Cd, Co, Mn, Ti, Ni, Hg, Pb) for four juvenile shark species (Carcharhinus limbatus, Paragaleus pectoralis, Rhizoprionodon acutus, and Sphyrna lewini) from Sal Rei Bay, Boa Vista Island, Cabo Verde—the first multi-species shark nursery area described in Atlantic Africa. Methodology: Seawater and sediment samples were collected from eight sites and analyzed along with plasma samples using total reflection X-ray fluorescence spectroscopy (TXRF). Sediment granulometry and pollution indices, including the enrichment factor (EF), ecological risk index (RI), and metal pollution index (MPI), were used to characterize habitat contamination. Data were analyzed using statistical models to explore spatial and element-specific patterns. Results: Overall, environmental contamination was low, with slight increases in Cd, Co, and Hg at sites 1 and 2, near the fishing port, and at site 5, likely reflecting natural transport, sediment redistribution, and enhanced nearshore deposition. Juvenile sharks exhibited generally low plasma trace element concentrations, although species-specific elemental signatures were evident: elevated levels of Al and Cu in C. limbatus, Zn in S. lewini, and As in R. acutus and P. pectoralis. Conclusions: These findings establish critical baseline reference values for trace elements in juvenile sharks from a key Atlantic nursery area. The results provide an essential framework for future biomonitoring efforts and contribute to the management and conservation of Cabo Verdean shark nursery habitats. Full article

Post-fire rehabilitation structures are widely used in Mediterranean burned landscapes to reduce runoff and sediment transfer, yet their ecological associations with early vegetation recovery remain insufficiently documented. This observational study assessed vascular plant composition, species richness, vegetation cover, plant density, aboveground biomass, and soil properties across log barriers, wattles, and log dams in the burned landscape of Ancient Olympia, western Greece. The study area belongs to the humid climatic class of the United Nations Environment Programme (UNEP) aridity framework based on the Thornthwaite aridity index, providing a comparatively wetter Mediterranean post-fire context. Paired depositional and eroded microsites in operationally restored post-fire areas were monitored in 2022 and 2023. The sampling design comprised nine plots and 18 microsites (n = 9 plots, 18 microsites). Generalized estimating equations (GEE), change-score models, principal component analysis (PCA) and permutational multivariate analysis of variance (PERMANOVA) were performed to examine associations of monitoring year, microsite condition and rehabilitation structure type with soil and vegetation patterns. A total of 27 vascular plant species belonging to 16 families were recorded. The average vegetation cover increased from 39.17 ± 21.44% in 2022 to 75.11 ± 12.90% in 2023. Model-based marginal estimates with 95% confidence intervals indicated a large positive increase in vegetation cover over this period. Further, rapid early recovery was indicated by large increases in species richness, plant density and biomass. Depositional microsites were associated with stronger recovery signals than eroded ones, characterized by a larger increase in vegetation cover, density, biomass and species richness. Among rehabilitation structures, log dams showed the highest cumulative floristic richness and a broader observed floristic spectrum, although the species-level contingency analysis provided only marginal evidence for structure-associated differences in floristic composition. Changes in selected soil properties including total nitrogen (total N), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), pH, electrical conductivity (EC), and exchangeable calcium (Ca), magnesium (Mg), and potassium (K), were detected between 2022 and 2023; the multivariate soil pattern was driven primarily by mineral nitrogen, pH, and EC. These findings suggest that, under operational post-fire restoration conditions, rehabilitation structures are associated not only with erosion-control functions but also with microsite differentiation that may shape early plant establishment and biodiversity recovery in Mediterranean burned landscapes. Full article

A novel wide-neck classifier (WNC) was designed to address the problem that thickeners cannot achieve classification prior to flocculation in a single unit. Using the computational fluid dynamics-discrete phase method and PIV experimental method, the reliability of the model was validated. We studied the motion characteristics of different particles within the novelty-designed WNC. The primary forces acting on coal slime particles in the composite force field were gravity, drag force, pressure gradient force, and virtual mass force. Drag force dominated the classification and sedimentation processes. In contrast, gravity, pressure gradient, and virtual mass forces promoted downward sedimentation but hindered upward overflow. The classification of slime particles in WNC was divided into initial classification after tangential feeding and centrifugal classification in a cone. Both simulation and experimental results demonstrate that, under consistent feed conditions, mineral density significantly affected the distribution of particles at the classification underflow and classification overflow. Among the three minerals, kaolinite has the highest classification effect, followed by quartz, while coal has the lowest classification effect. Full article

The Tomarrazón-Camarones Basin (La Guajira, Colombia) is characterized by frequent, widespread flooding and, anthropogenically, by intense instream sediment mining. Mapping flood hazard is hence essential to develop effective flood management plans, and a knowledge of the water regime (duration curves) is also essential to estimate sediment transport and carry out sediment budgets to inform on the impacts and sustainability of the mining activity. However, neither water levels nor discharges are monitored by official gauging stations, and only a few rainfall gauging stations are available in the area, with daily records often affected by data gaps. Therefore, a first challenge is to reconstruct discharge time series by an affordable effort, scaled to the financial-labour resources available in that challenging context. This paper presents an integrated approach that combines satellite-derived rainfall data with ground observations. A semi-distributed hydrological model (HEC-HMS, SCS-CN method) is used to reconstruct the full flow-rate time series once calibrated and validated with data derived from automatic sensors and field measurements. The model is fed with hourly data derived from daily data at ground gauging stations temporally downscaled by adopting the spatially distributed hourly rainfall patterns obtained from satellite records. Before that, observed water levels in three stations equipped with water level sensors were translated into discharge time series using analytical relationships based on field-measured geometric and physical characteristics. Then, these event-based hydrographs were used to calibrate and validate the model. Results show good agreement with observations, with R² = 0.981 and a relative RMSE of 40% for overall hydrograph reproduction, and R² = 0.87 for peak flow estimation, supporting a reasonable confidence in the approach. The calibrated model is then applied to long-term datasets (1973–2024) to retrieve duration curves and return periods of peak discharges. Full article

This study evaluates the ecological impacts of seawater desalination discharge on coastal marine ecosystems through a sequential analytical framework linking systematic literature synthesis, field-monitoring evidence, spatial analysis, and predictive ecological modeling. The novelty of the study lies in combining multi-regional evidence from Mediterranean coastal zones, Persian Gulf waters, and Pacific coastal environments with threshold-based ecological risk assessment, thereby linking discharge-related environmental stressors with biological responses and ecosystem-function alterations. The systematic review first retained 750 studies published between 2004 and 2024 for qualitative synthesis. On this basis, 59 high-quality references with sufficient numerical information were selected for the main quantitative meta-analysis, while field-monitoring data were used to support the interpretation of distance-based discharge gradients. Spatial interpolation and hierarchical modeling were then applied to evaluate exposure–response patterns and ecological threshold behavior. The results showed that desalination facilities generated measurable ecological impacts mainly within 50–200 m of discharge points, with a critical transition distance of approximately 127 m where hypersaline conditions, typically 1.5–2.0 times ambient seawater levels, were associated with marked changes in marine community structure. Benthic assemblages showed taxon-specific responses, with mollusks and echinoderms exhibiting greater sensitivity than polychaetes and small crustaceans. Marine vegetation declined strongly under combined salinity, thermal, and chemical stress, while phosphonate-based antiscalants accumulated in filter-feeding organisms and produced bioaccumulation factors up to 42.1 times ambient levels. Ecosystem-function indicators, including microbial community composition and sediment organic matter processing, remained altered up to 300 m from discharge points, indicating that functional impacts may extend beyond the primary hypersaline plume. The predictive modeling framework further demonstrated that ecological risk decreased nonlinearly with distance and varied according to discharge intensity, local hydrodynamics, and biological sensitivity. These findings indicate that conventional uniform buffer-based assessment may underestimate the ecological footprint of desalination discharge. Sustainable desalination management should therefore adopt site-specific monitoring, species-sensitive protection thresholds, improved brine-management technologies, and adaptive mitigation strategies based on real-time environmental feedback. Full article

Coastal Louisiana continues to experience rapid wetland loss, increasing the exposure of marsh-creation containment dikes to storm-driven waves, erosion, and sediment loss. This study evaluated offshore-to-nearshore wave transformation, erosion risk reduction, wave runup, and hydrodynamic loading at a representative marsh-creation site in Plaquemines Parish, Louisiana. A 25-year return-period offshore wave condition was derived from long-term Wave Information Study hindcast data and propagated using the SWAN spectral wave model. Two idealized foreshore conditions were examined: a bare-bed case and a marsh-roughened shallow water case represented through enhanced bottom friction. Web Soil Survey data were used to characterize the local soil context of the containment-dike zone. The results show strong wave attenuation across the inner shelf and marsh platform. Relative to the bare-bed case, marsh roughness reduced dike toe significant wave height by 16.1–27.4% and decreased the Hs²-based erosion exposure proxy by 29.6–47.4% across three still-water levels. These reductions produced 15.4–26.4% lower 2% exceedance runup and 28.5–45.8% lower quasi-hydrostatic loading on the containment dike. The results indicate that marsh-induced dissipation can help reduce erosion potential and support sustainable coastal restoration infrastructure management. Full article

Coastal zones are dynamic interfaces where land, ocean, and atmosphere interact, making them sensitive indicators of environmental change. However, quantifying shoreline movement across long distances and over multi-year timescales remains challenging using traditional ground-based methods alone. We conducted an analysis of environmental factors and shoreline dynamics along a 58 km stretch of the arid Cabo Pulmo shoreline in Mexico from 2020 to 2026 using the CoastSat tool. The landscape is characterized by a diverse array of geographical features, including sandy beaches, granite cliffs, estuarine systems, and various anthropogenic structures. Results indicated a sea-level rise of 2 mm/year over the last 27 years, which is consistent with the reported range for the Pacific (1.8 to 3.8 mm/year). Notably, we observed an increasing trend of Category 4 and 5 hurricanes in the Mexican Pacific, with an average of 1 additional hurricane per decade (1950–2023). A total of 457 Sentinel-2 satellite images were used for automated analysis using the CoastSat platform, all of which were acquired under tidal conditions not exceeding 1 m. Our findings indicate that the granite cliffs show no detectable horizontal changes in the satellite images; however, their minimal vertical erosion contributes sediment to adjacent beaches. The most significant shoreline erosion was observed north of a marina breakwater, measuring −19.7 m, attributed to the disruption of littoral transport toward the southeast. In contrast, sandy beaches located in front of streams and estuaries—characterized by a lack of infrastructure (houses and breakwaters) and gentle slopes of 2° to 4°—demonstrated positive accretion of up to 5.9 m. According to the autoregressive distributed lag model, wave energy and hurricane-driven wind gusts are the primary agents of shoreline retreat, displacing sediment seaward to the continental shelf. Sea level rise exacerbates this retreat, while rainfall plays a minor but contributing role by transporting sediment during hurricanes in this arid region. This study highlights the effectiveness of CoastSat as a neural network-based tool for analyzing shoreline changes; however, we faced certain limitations, such as the absence of in situ beach profiles due to restricted access. Full article

This study established a refined, distributed SWAT modeling framework that integrates elevation-band and snowmelt modules to reconstruct the alpine hydrological and sediment cycles of the Koshi River Basin (KRB) over the period 1990–2024, with climate scenarios constructed using the delta change approach. The KRB, a major transboundary watershed traversing China, Nepal, and India, was selected owing to its critical hydro-climatic role under the destabilizing “Asian Water Tower”; it generates substantial sediment yield, hosts the densest concentration of hydropower potential within the Ganges system, and spans an extreme vertical gradient from Mount Everest to the southern alluvial plains. Results reveal accelerated warming at a rate of 0.21 °C per decade and an overall warming–wetting trend, punctuated by an abrupt interdecadal shift around 2015. Precipitation dominated interannual streamflow variability, with enhanced rainfall triggering basin-wide sediment surges that overwhelmed the natural buffering capacity of the land surface. Conversely, rising temperatures intensified actual evapotranspiration, markedly depleting soil water and reducing total water yield and monsoon runoff, although sustained snow and glacier melt effectively elevated the dry-season low-flow baseline. The integrated climate forcing reshaped the disparity between hydrological extremes, imposing severe seasonal eco-hydrological stress that manifested as a pre-monsoon deficit in terrestrial green water and acute summer sediment outbursts for aquatic habitats. Furthermore, the flood regime exhibited an altered distribution, with mid-to-high frequency floods enhanced while low-frequency extreme flood peaks declined. The hydro-sedimentological regime consequently exhibits pronounced nonlinear responses to climate change, providing a critical, threshold-based scientific foundation for adaptive transboundary water resource management. Full article

The Santiago River is a highly anthropogenically impaired lotic system globally, yet the mechanisms governing its contaminant transport remain poorly understood under static monitoring paradigms. This study evaluates how hydrological forcing dictates the mobilization and bioavailability of trace metals by integrating a 15-year public hydrochemical database from 10 monitoring nodes with SAR-derived discharge estimates and thermodynamic metal modeling (PHREEQC). To validate the structural integrity of the mass load estimates against hydrometric uncertainties, a deterministic boundary-sensitivity analysis was conducted. Results empirically refute the classical dilution paradigm, introducing the “Anthropogenic Pulse” to describe the non-linear acceleration of pollutant export during high-flow events (discharge Q surging from 36.62 to 286.13 m³/s). While climate-driven parameters follow seasonal cycles, industrial stressors (COD, Pb, Cd) remain in a chronic steady state, decoupling from volumetric dilution. Based on coupled × CQ × C (discharge × concentration) estimates, this dynamic induces a synchronized flushing of toxic burdens, exporting monthly peak loads exceeding 51,000 kg of Zinc, 6500 kg of Lead, and 3100 kg of Cadmium. Thermodynamic simulations reveal that this hydrological flushing functions as a chemical activator; the seasonal dilution of natural Alkalinity and Hardness suppresses the river’s theoretical buffered pH (from 8.5 to 7.0), maintaining metals in their uncomplexed free-ion states (Me²⁺). Modeling indicates that nearly 90% of the exported Cadmium remains in this highly labile, toxic form due to a dual coupling with both river Discharge (r_s = 0.87) and pH (r_s = 0.79). The identification of stochastic arsenic peaks 100 times above regulatory limits at Paso de Guadalupe (RS-08) underscores the failure of concentration-based monitoring. Our findings suggest that restoration strategies should shift toward mass-loading-based regulatory frameworks and targeted sediment management at critical nodes to mitigate the chronic export of bioavailable industrial waste. Full article