Search

The Tibetan Plateau (TP) is suffering from a substantial decline in terrestrial water storage (TWS) in exorheic basins, threatening water resources that are critical for ∼2 billion people downstream. TWS changes are commonly estimated using gravity satellites through observations of the total terrestrial mass storage (TMS) change, with an implicit assumption of a negligible contribution from sediment transport. Through long‐term (2002–2017) sediment flux observations in seven headwater basins on the TP, we reveal that the gravity satellite‐derived TMS has decreased at a rate of 3.85 ± 0.23 Gt yr−1 in the seven basins, of which 0.35 ± 0.04 Gt yr−1 is contributed by sediment transport. Neglecting this contribution leads to an overestimation of the TWS loss by 10.1 ± 1.3%, equivalent to the annual water demand of an additional 0.62 million people in the surrounding nations. Regionally, the overestimation is surprisingly high in the Indus River and Yarkant River basins, reaching up to 50.8%–77.6%. Plain Language Summary: Accurate quantification of the change in the terrestrial water storage (TWS) on the Tibetan Plateau (TP) is imperative to improve the assessment of water availability that are critical for ∼2 billion people downstream. Through long‐term sediment flux observations, here we find that sediment transport makes a substantial contribution to gravity satellite‐derived TWS change in regions with a high erosion rate such as the TP, which has never been taken into consideration in previous studies. Neglecting this contribution leads to an overestimation of the TWS loss by about 10% on average for the seven headwater basins on the TP. The contribution is especially high in the Indus River and Yarkant River basins. Our findings improve the regional estimation of water availability and thus support climate adaptation and sustainable water resource management. Key Points: For the first time, we quantify the contribution of sediment transport to gravity satellite‐based estimation of TWS change on the TPNeglecting the contribution of sediment transport leads to an overestimation of the TWS loss by 10.1% on averageThe overestimated TWS loss is equivalent to the annual water demand of an additional 0.62 million people in surrounding nations [ABSTRACT FROM AUTHOR]

Soil erosion poses a significant problem in the Mediterranean region, posing serious threats to the environment and natural resources. The objective of this study is to identify and evaluate the risks associated with gully erosion in the Medjerda watershed in the northeastern part of Algeria. To accomplish this goal, two models were utilized: the fuzzy analytic hierarchy process (F-AHP) and the frequency ratio (FR). Twelve factors that contribute to soil erosion were considered in the study: slope, elevation, distance to streams, land use and land cover, drainage density (DD), topographic wetness index (TWI), rainfall, soil groups, lineament density, soil power index (SPI), sediment transport index (STI), and plan curvature. The results indicate that sediment transport index (STI), rainfall, and slope are the most influential factors in predicting erosion in the Medjerda Basin. To validate the models used, the area under the receiver operating characteristics curve (AUC) was employed. The AUC values obtained for the FR and F-AHP models were 75.5 and 73.7%, respectively, indicating their excellent accuracy in identifying the erosion susceptibility area. The accuracy ratings of both models demonstrate their outstanding predictive capabilities. Thus, the results of soil erosion susceptibility maps with a better success rate and forecast could be beneficial and effective for implementing various policy measures to safeguard soil. They could be useful for managing gully erosion risks in different parts of the river basin. [ABSTRACT FROM AUTHOR]

The present paper develops a new framework to predict the mean flow through an array of cylinders in which the flow around the array (array‐scale) and the flow around individual cylinders (element‐scale) are modeled separately using actuator disc theory and empirical drag models respectively, and then coupled through the net drag force. Applying this framework only requires knowledge of the array geometry and incident flow. The framework is validated using high‐fidelity direct numerical simulations for arrays of between 7 and 109 cylinders having different arrangements (staggered, concentric, random) and bounding shapes (circular, square) in both two‐ and three‐dimensional flows. In general, the framework outperforms existing models which require calibration and are only valid for part of the practical parameter space. The demonstrated scale separation suggests different combinations of element‐scale and array‐scale models/theories may be used for other arrangements of bluff bodies. Plain Language Summary: The temporally and spatially averaged velocity, or mean flow, within an array of cylinders is important for many practical applications including, for example, estimating the rates of sediment transport and nutrient uptake within a patch of aquatic vegetation, the hydrodynamic forces on offshore structures, and the efficiency of power generation with a turbine farm. However, a general predictive tool for mean flow is currently lacking. To develop this predictive capacity, this study uses the idea of scale separation to integrate models from different research fields, including the actuator disc theory originally developed for design of turbines and propellers, and element‐scale drag models initially proposed for aquatic vegetated flows, to develop a unifying, predictive, analytical framework to estimate the mean flow. The framework is validated using high‐fidelity direct numerical simulations of arrays of cylinders with different arrangements (staggered, concentric, random) and array shapes (square, circular). With only knowledge of the array geometry and incident flow, the framework predicts the mean flow exceptionally well across a wide range of practical flow conditions. This leads to a step‐change in our ability to predict the fraction of incoming flow passing through a porous array, hydrodynamic load on offshore structures, and sediment flux within aquatic vegetation systems when combined with bed load transport models. The framework could be an important guide for coastal and riverine restoration projects using aquatic vegetation and the design of offshore structures and turbine farms. Key Points: A predictive framework based on an idea of scale separation is proposed for the mean velocity of the flow passing through an array of cylindersThe framework is versatile, being applicable for a wide range of practically meaningful cylinder arrangements, array shapes and array flow blockagesHigh‐fidelity, three‐dimensional direct numerical simulations are employed to investigate flow through the array of cylinders and validate the new predictive framework [ABSTRACT FROM AUTHOR]

The battering of bedrock by bedload collisions is the primary mechanism by which bedrock rivers erode and landscapes evolve. The energy imparted via impacts acts to detach bedrock via the growth and intersection of surface fractures. We present impact experiments designed to test the influence of particle impact energy on bedrock erosion rates. We found that erosional efficiency increased with increasing impact energy. Notably, these increases in efficiency are not captured by a widely‐used mechanistic bedrock erosion model. Observed increases in erosional efficiency were linked with enhanced elastic energy dissipation captured by differences in the coefficient of restitution. We suggest that this increase in energy dissipation is indicative of enhanced crack extension for high velocity impacts. Our experiments indicate a clear energy‐dependence for bedrock detachment processes that is not yet captured by bedrock incision models but may be integrated into long‐term erosion rates and landscape evolution. Plain Language Summary: Bouncing sediment grains batter the bedrock beds of rivers during floods. As these impacts collide with the bed, they slowly chip away at the riverbed bedrock. It's perhaps intuitive that a grain with more energy when it collides with the riverbed is able to chip away more bedrock. But, how much more destructive are these high energy impacts? We designed an experiment where we hit a bedrock sample with a steel ball at a range of impact energies, over and over again, up to 30,000 times, and measured how much material was chipped away. High energy impacts eroded more material, but this increased efficiency of erosion is not fully captured by impact‐based erosion models. We hypothesize that for higher energy impacts, a larger fraction of the incoming energy is used to crack the bedrock, more easily eroding material. We liken the relative influence of these high energy impacts to a battering ram, where only a few strikes can easily break down a door, whereas lower energy impacts, similar to a simple knock, are unlikely to achieve the same result. We suggest that this effect may be important in determining the influence of extreme events on bedrock erosion over long timescales. Key Points: Impact experiments demonstrate that bedrock erosional efficiency is enhanced with increasing impact energyExperimentally‐derived coefficients of restitution and rock resistance coefficients indicate enhanced elastic energy dissipation with increasing impact energyResults suggest that more energetic impacts enhance crack extension, increasing erosional efficiency [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that vegetation‐generated turbulence can enhance erosion rate and reduce the velocity threshold for erosion of non‐cohesive sediment. This study considered whether vegetation‐generated turbulence had a similar influence on natural cohesive sediment. Cores were collected from a black mangrove forest with aboveground biomass and exposed to stepwise increases in velocity. Erosion was recorded through suspended sediment concentration. For the same velocity, cores with pneumatophores had elevated turbulent kinetic energy compared to bare cores without pneumatophores. However, the vegetation‐generated turbulence did not increase bed stress or the rate of resuspension, relative to bare cores. It was hypothesized that the short time‐scale fluctuations associated with vegetation‐generated turbulence were not of sufficient duration to break cohesion between grains, explaining why elevated levels of turbulence associated with the pneumatophores had no impact on the erosion threshold or rate. Plain Language Summary: Mangrove habitat grows by retaining sediment. To restore these systems, it is necessary to understand how vegetation influences the transport and retention of sediment. This study used sediment cores collected from the interior of a mangrove forest to study how the aboveground roots, called pneumatophores, influence hydrodynamic conditions and sediment transport, and in particular the onset and rate of sediment erosion. Individual pneumatophores generate eddies that enhance turbulence, compared to conditions without pneumatophores. In sandy soil, vegetation‐generated turbulence can enhance erosion. However, in this study, vegetation‐generated turbulence did not increase the rate of erosion for natural cohesive (muddy) sediment, suggesting that the mangrove forest interior has naturally greater resistance to erosion and sediment loss. Key Points: For the same velocity, cores with pneumatophores had higher turbulent kinetic energy (TKE) compared to cores without pneumatophoresUnlike sands, the inception of erosion and erosion rates for cohesive sediment were better predicted by bed shear stress than by TKEModelers should parameterize erosion within vegetation differently for cohesive and non‐cohesive sediment [ABSTRACT FROM AUTHOR]

This paper presents the parallelization of two widely used implicit numerical solvers for the solution of partial differential equations on structured meshes, namely, the ADI (Alternating-Direction Implicit) solver for tridiagonal linear systems and the SIP (Strongly Implicit Procedure) solver for the penta-diagonal systems. Both solvers were parallelized using CUDA (Computer Unified Device Architecture) Fortran on GPGPUs (General-Purpose Graphics Processing Units). The parallel ADI solver (P-ADI) is based on the Parallel Cyclic Reduction (PCR) algorithm, while the parallel SIP solver (P-SIP) uses the wave front method (WF) following a diagonal line calculation strategy. To map the solution schemes onto the hierarchical block-threads framework of the CUDA on the GPU, the P-ADI solver adopted two mapping methods, one block thread with iterations (OBM-it) and multi-block threads (MBMs), while the P-SIP solver also used two mappings, one conventional mapping using effective WF lines (WF-e) with matrix coefficients and solution variables defined on original computational mesh, and a newly proposed mapping using all WF mesh (WF-all), on which matrix coefficients and solution variables are defined. Both the P-ADI and the P-SIP have been integrated into a two-dimensional (2D) hydrodynamic model, the CCHE2D (Center of Computational Hydroscience and Engineering) model, developed by the National Center for Computational Hydroscience and Engineering at the University of Mississippi. This study for the first time compared these two parallel solvers and their efficiency using examples and applications in complex geometries, which can provide valuable guidance for future uses of these two parallel implicit solvers in computational fluids dynamics (CFD). Both parallel solvers demonstrated higher efficiency than their serial counterparts on the CPU (Central Processing Unit): 3.73~4.98 speedup ratio for flow simulations, and 2.166~3.648 speedup ratio for sediment transport simulations. In general, the P-ADI solver is faster than but not as stable as the P-SIP solver; and for the P-SIP solver, the newly developed mapping method WF-all significantly improved the conventional mapping method WF-e. [ABSTRACT FROM AUTHOR]

The recession of Alpine glaciers causes an increase in the extent of proglacial areas and leads to changes in the water discharge and sediment balance (morphodynamics and sediment transport). Although the processes occurring in proglacial areas are relevant not only from a scientific point of view but also for the purpose of climate change adaptation, there is a lack of work on the continuous monitoring and multitemporal characterization of these areas. This study offers a multidisciplinary approach that merges the contributions of different scientific disciplines, such as hydrology, geophysics, geomatics, and water engineering, to characterize the Rutor Glacier and its proglacial area. Since 2020, we have surveyed the glacier and its proglacial area using both uncrewed and crewed aerial surveys (https://doi.org/10.5281/zenodo.8089499 , ; https://doi.org/10.5281/zenodo.10100968 , ; https://doi.org/10.5281/zenodo.10074530 , ; https://doi.org/10.5281/zenodo.10101236 , ; https://doi.org/10.5281/zenodo.7713146 ,). We have determined the bathymetry of the most downstream proglacial lake and the thickness of the sediments deposited on its bottom (https://doi.org/10.5281/zenodo.7682072 ,). The water depth at four different locations within the hydrographic network of the proglacial area (https://doi.org/10.5281/zenodo.7697100 ,) and the bedload at the glacier snout (https://doi.org/10.5281/zenodo.7708800 ,) have also been continuously monitored. The synergy of our approach enables the characterization, monitoring, and understanding of a set of complex and interconnected processes occurring in a proglacial area. [ABSTRACT FROM AUTHOR]

In order to investigate the impact of marine propeller wake fields on sediment siltation in shallow water channels, this study employs the unsteady RANS approach and the Volume of Fluid model. A full-scale numerical self-propulsion test was conducted on a 50,000 DWT oil tanker under the influence of a free surface. The research includes forecasting the effect of propeller wakes on sediment redeposition following the dredging of the approach channel to Jiaxing Port in the China Sea. Initially, uncertainty research was carried out on the full-scale ship and propeller system, and the credibility of the computational results was quantified. The simulated results based on the sediment transport numerical model were then compared and validated against actual data from monitoring stations. The self-propulsion performance and the velocity distribution of the propeller wake were examined under three different propeller speeds. Scenarios simulated included no ship navigation, daily single-ship navigation, and daily two-ship navigation, evaluating the siltation distribution within the channel over one month. The results demonstrate that ship propeller wakes positively influence the reduction of channel sedimentation, with the maximum monthly siltation reduction reaching 0.108 m during single-ship tidal navigation and 0.11 m during two-ship tidal navigation. [ABSTRACT FROM AUTHOR]

Guru Prasath, J.; Sannasiraj, S.A., and Chandramohan, P., 2024. Nearshore morphological changes due to severe cyclonic storm activity along the east coast of India. Journal of Coastal Research, 40(4), 696–713. Charlotte (North Carolina), ISSN 0749-0208. Nearshore waves, wind, and tidal current mobilize seabed sediments; sort, transport, and redistribute the sediments; and modify the nearshore seabed morphology. Waves play a dominant role in morphological changes among winds, waves, and tidal currents. The nearshore wave breaking induces the initiation of sediment movement, and the associated alongshore current transports a large volume of sediments that tend to either accrete toward or erode from the beach face and seabed. Sediment transport rate in the nearshore waters during cyclones is higher than that under normal conditions. The measured changes due to Cyclone Nivar in November 2020 in the nearshore morphology along the Mahabalipuram coast are examined to understand the response of nearshore morphology to cyclonic wave-induced forcing. The beach-profile measurements across 10 transects at 100 m spacing covering about 1000 m along the coast were measured before and after the passage of Cyclone Nivar as a part of the present field study. The evolving beach profiles during Cyclone Nivar were simulated using the storm-induced beach change (SBEACH) model, which is a cross-shore profile evolution model. The changes due to berm erosion and deposition of nearshore sand bars have been compared from field measurements data and model prediction. The calibrated model was then used to simulate the beach profile response at two other locations along the cyclone-affected coastline to examine the shoreline impact. The calibrated model can be used along the coast to understand the poststorm profiles of the beach with reasonable accuracy. [ABSTRACT FROM AUTHOR]

• The coupled 2D mophodynamic model considers effects of sediment concentration and bed deformation in the governing equations. • Unstructured meshes better conform with the irregular geometry of the natural rivers. • Channel adjustments play a significant role in sediment transport of alluvial rivers during a flood event. It is difficult to predict the detailed morphodynamic processes induced by heavily sediment-laden floods in alluvial rives, due to the complexity in topography and the significant channel evolution rates, especially in a braided reach of the Lower Yellow River (LYR). A two-dimensional morphodynamic model using a coupled solution approach was firstly developed, with the effects of sediment concentration and bed deformation being directly considered in the hydrodynamic governing equations. The finite volume method with the HLL-MUSCL scheme was adopted in the numerical solution, which can obtain second-order accuracy in space and time. In addition, unstructured meshes were used to accommodate the irregular boundaries. The proposed model was validated using measurements in the braided reach of the LYR during the flood events of 2020 and 2004, with general agreement obtained between the calculated and measured hydrographs of flow and sediment concentration. The highest accuracy was achieved in the simulation of discharge, with a Nash-Sutcliffe efficiency coefficient (NSE) of 0.92. The simulation accuracy in sediment concentration was improved by the coupled approach, with the relative error of the calculated peak value decreasing from 17 % to 9 %. In addition, transport characteristics of graded suspended sediments were well simulated, with the fine fraction being transported downstream and the medium fraction depositing in the study reach. Influences of channel adjustments on the sediment transport processes were investigated during a flood event. The results demonstrated that the incised channel in 2020 was characterized by a larger water depth and smaller velocity, as compared with the shallow channel in 2004. Consequently, the peak discharge decreased and the flood propagation time was extended under the 2020 topography, associated with the lower sediment discharge at the outlet due to the reduced sediment transport capacity. [ABSTRACT FROM AUTHOR]

Bedload sediment transport plays an important role in the evolution of rivers, marshes and deltas. In these aquatic environments, vegetation is widespread, and plant species have unique morphology. However, the impact of real plant morphology on flow and sediment transport has not been quantified. This study used model plants with real plant morphology, based on the aquatic species Phragmites australis, Acorus calamus and Typha latifolia. The frontal area of these species increases away from the bed, which leads to higher near‐bed velocity than would be predicted from depth‐average frontal area. A plant morphology coefficient was defined to quantify the impact of vertically‐varied plant frontal area. Laboratory experiments confirmed that the plant morphology coefficient improved the prediction of near‐bed velocity, near‐bed turbulent kinetic energy and bedload transport rate in canopies with realistic morphology. Plant morphology can alter transport rates by up to an order of magnitude, relative to the assumption of uniform morphology. Plain Language Summary: Aquatic vegetation is a crucial component of river, marsh and delta ecosystems. It has a significant impact on landscape evolution by altering sediment transport. Each vegetation species has a unique shape, but the impact of plant shape on sediment transport has not been previously investigated. This study explained how plant shape impacts sediment transport. Results show that differences in plant shape can change velocity and turbulence close to the channel bed, and thus alter sediment transport rate by an order of magnitude. Plants with greater vertical variation in shape, and specifically less plant volume near the channel bed, produced greater sediment transport. A parameter was defined to quantify the impact of plant shape on flow and sediment transport. By incorporating this parameter, our new model improves the prediction of sediment transport in vegetated regions. This study provides a method for describing the impact of plant shape on flow and sediment transport, which is important to the management and restoration of rivers, marshes and deltas. Key Points: Plant morphology influences the near‐bed velocity, turbulent kinetic energy (TKE) and bedload transport rate inside emergent canopiesA new model accounts for plant morphology in the prediction of near‐bed velocity and TKE and bedload transportFor each canopy solid volume fraction, plants with greater vertical variation in frontal area produce greater bedload transport [ABSTRACT FROM AUTHOR]

In this paper, an Eulerian two-phase-flow model sedFoam is extended to include an air phase together with the water and sediment phases. The numerical model called sedInterFoam is implemented using the open source library OpenFOAM. SedInterFoam includes the previous features of sedFoam for sediment transport modeling and also solves the air/water interface using the volume of fluid method coupled with the waves2Foam toolbox for free surface wave generation and absorption. Using sedInterFoam, four test cases are successfully reproduced to validate the free-surface evolution algorithm implementation, mass conservation of sediment and fluid phases, predictive capabilities and demonstrate its potential in modelling a broader range of coastal applications with sediment transport dominated by surface waves. [ABSTRACT FROM AUTHOR]

Hydrogeomorphology studies river dynamics, focusing on the interactions between flow structure, sediment transport, and the morphologies that characterize rivers and their watersheds. It provides an analytical framework and tools for better integrating knowledge of river dynamics into river management in the broadest sense, and more specifically, into river restoration as well as into the assessment and prevention of risks associated with fluvial hazards. In Quebec, hydrogeomorphology is emerging as a significant contribution to risk assessment and management approaches, and is at the heart of a paradigm shift in river management whereby process restoration aims to increase the resilience of fluvial systems and societies, and improve the quality of fluvial environments. This contribution outlines the trajectory of hydrogeomorphology in Quebec, based on scientific publications by Quebec geographers, and discusses the discipline's aims in research and knowledge integration for river management. Messages clés: Les géographes du Québec ont contribué fortement au développement des connaissances et outils de l'hydrogéomorphologie.L'hydrogéomorphologie a évolué d'une science fondamentale à une science où les connaissances fondamentales sont au service de la gestion des cours d'eau.L'hydrogéomorphologie et le cortège de connaissances et d'outils qu'elle promeut font de cette discipline une partenaire clé pour une gestion holistique des cours d'eau. [ABSTRACT FROM AUTHOR]

AlMashan, N.; Al-Attar, I., and Neelamani, S., 2024. Assessment of annual sedimentation into Failaka Marina (Kuwait) and possible solutions for reduction of siltation. Journal of Coastal Research, 40(3), 527–553. Charlotte (North Carolina), ISSN 0749-0208. Sedimentation is critical for ports, harbors, and marinas, requiring accurate assessment. Failaka Marina in Kuwait is experiencing a severe noncohesive sedimentation problem. The samples collected at the seven locations along the beach showed that the beach has a uniform grain-size diameter, meaning it is poorly graded sand. The sampling at the tip of the southern breakwater showed that the shoaling is mainly sand. The suspended-sediment concentration varies from 0.025 kg m–3 to 1.2 kg m–3, whereas the mean concentration at the marina entrance is 0.85 kg m–3. The time series of the suspended solids over a year in the seawater surrounding Failaka Island shows a range of 8 to 48,069 ppm. Such a considerable variation in suspended load is due to the massive amounts of dredging and spoil disposal at Boubyan Island and Basra Port (Iraq) when a high sediment load moves around Failaka Island with a concentration of more than 40,000 mg L–1. Annual sedimentation is about 2.35 m y–1, which is responsible for blocking the main entrance for navigation. Kuwait's Ministry of Communication allocates $4 to $6 million annually for dredging and disposal activities. This study evaluates the six marina entrance modification scenarios to determine the best scenario that achieves a measurable reduction in sedimentation rate in the Marina. Six marina breakwater modifications were studied, and annual sedimentation rates were numerically computed. The study use Coupled MIKE 21/3 to simulate hydrodynamic conditions for cohesive sediment transport in a problem area. Field data from 2015 calibrated and validated the model. The primary sediment-moving force is SE wind and sea-swell waves. Littoral drift along Failaka Island's southern coastline and high suspended-sediment concentration result in littoral drift and settling. The best scenario showed a 28% sedimentation reduction and a 26% reduction in maintenance dredging costs from the six studied scenarios. [ABSTRACT FROM AUTHOR]

Silt-rich meltwater plume deposits (MPDs) analyzed from marine sediment cores have elucidated relationships that are clearly connected, yet difficult to constrain, between subglacial hydrology, ice-marginal landforms, and grounding-zone retreat patterns for several glacial catchments. Few attempts have been made to infer details of subglacial hydrology, such as flow regime, geometry of drainage pathways, and mode(s) of sediment transport through time, from grain-scale characteristics of MPDs. Using sediment samples from MPD, till, and grounding-zone proximal diamicton collected offshore of six modern and relict glacial catchments in both hemispheres, we examine grain shape distributions and microtextures (collectively, grain micromorphology) of the silt fraction to explore whether grains are measurably altered from their subglacial sources via meltwater action. We find that 75 % of all imaged grains (n = 9400) can be described by 25 % of the full range of measured shape morphometrics, indicating grain shape homogenization through widespread and efficient abrasive processes in subglacial environments. Although silt grains from MPDs exhibit edge rounding more often than silt grains from tills, grain surface textures indicative of fluvial transport (e.g., v-shaped percussions) occur in only a modest number of grains. Furthermore, MPD grain surfaces retain several textures consistent with transport beneath glacial ice (e.g., straight or arcuate steps, (sub)linear fractures) in comparable abundances to till grains. Significant grain shape alteration in MPDs compared to their till sources is observed in sediments from glacial regions where (1) high-magnitude, potentially catastrophic meltwater drainage events are inferred from marine sediment records and (2) submarine landforms suggest supraglacial melt contributed to the subglacial hydrological budget. This implies that quantifiable grain shape alteration in MPDs could reflect a combination of high-energy flow of subglacial meltwater, persistent sediment entrainment, and/or long sediment transport distances through subglacial drainage pathways. Integrating grain micromorphology into analysis of MPDs in site-specific studies could therefore aid in distinguishing periods of persistent, well-connected subglacial discharge from periods of sluggish or disorganized drainage. In the wider context of deglacial marine sedimentary and bathymetric records, a grain micromorphological approach may bolster our ability to characterize ice response to subglacial meltwater transmission through time. This work additionally demonstrates that glacial and fluvial surface textures are retained on silt-sized quartz grains in adequate amounts for microtexture analysis, which has heretofore been conducted exclusively on the sand fraction. Therefore, grain microtextures can be examined on silt-rich glaciogenic deposits that contain little to no sand as a means to evaluate sediment transport processes. [ABSTRACT FROM AUTHOR]

Mount Meager is a deeply eroded quaternary volcanic complex located in southwestern British Columbia (BC) and is known for its frequent large landslides. In 2010, the south face of Mount Meager collapsed, generating a long-runout debris avalanche that was one of the largest landslides (50 × 106 m3) in Canadian history. Over the past 14 years, the landslide deposit has been reworked by stream action, delivering large amounts of sediment to Lillooet River, just downstream. In this study, we investigate 10 years of geomorphic evolution of the landslide deposit using orthophotos and digital elevation models (DEMs) generated using Structure from Motion (SfM) photogrammetry on aerial photographs acquired during unmanned aerial vehicle (UAV) and Global Navigation Satellite System (GNSS) surveys. The SfM products were used to produce a series of precise maps that highlight the geomorphological changes along the lower Meager Creek within the runout area of the landslide. Comparison of DEMs produced from 2010, 2012, 2015, and 2019 imagery allowed us to calculate deposit volume changes related to erosion, transport, and redeposition of landslide material. We estimate that about 1.1 × 106 m3 of sediment was eroded from the landslide deposit over the period 2015–2019. About 5.2 × 105 m3 of that sediment was redeposited inside the study area. About 5.8 × 105 m3 of sediment, mainly sand, silt, and clay, were exported from the study area and are being carried by Lillooet River towards Pemberton, 40 km from Mount Meager, and farther downstream. These remobilized sediments likely reduce the Lillooet River channel capacity and thus increase flood hazards to the communities of Pemberton and Mount Currie. Our study indicates a landslide persistence in the landscape, with an estimated 47-year half-life decay, suggesting that higher flood hazard conditions related to increased sediment supply may last longer than previously estimated. This study shows the value of using SfM in tandem with historic aerial photographs, UAV photos, and high-resolution satellite imagery for determining sediment budgets in fluvial systems. [ABSTRACT FROM AUTHOR]

Exploring very-large-scale motions (VLSMs) in open channel flows (OCFs) is crucial for comprehensively understanding material transport and energy exchange. While previous studies focused on OCFs in ideal flumes with simple boundaries, this paper presents large eddy simulation (LES) results on the existence and scale characteristics of VLSMs in complex river morphologies with the Minjiang River in southwestern China as a case study. This research demonstrates that the OpenFOAM-based LES model is capable of accurately reconstructing the time-averaged flow field and providing instantaneous velocity data that capture VLSMs with sufficient resolution. Spectrum analysis of the streamwise fluctuating velocity shows that VLSMs are present in the straight segment of the river, with streamwise wavelengths approximately (16–22) times the water depth but are absent in the bend and confluence segments due to the suppression by secondary currents. This article validates the effectiveness of LES in examining the characteristics of VLSMs in natural rivers, thereby laying a good foundation for further studies on the impacts of such structures on sediment transport and pollutant dispersion. [ABSTRACT FROM AUTHOR]

The dating of moraine deposits can present challenges to standard geochronological methods; terrestrial cosmogenic nuclide (TCN), sediment luminescence and radiocarbon dating may suffer from problems of incomplete resetting (by inheritance, intermittent cover/exposure, transport under unfavourable conditions) and/or a lack of suitable (organic) material. Rock surface luminescence burial dating (RSLBD) offers an alternative approach with considerable potential in dating moraines. In RSLBD, large cobbles/boulders are targeted, rather than smaller grains usually used in luminescence dating. The age limit of RSLBD is much higher than that of radiocarbon dating, and rocks are much more readily available than organic material. In contrast to TCN dating, the effect of exposure prior to deposition can be measured. In this study, we sampled a broad selection of primarily granitic boulders of various sizes and shapes (e.g. different degrees of roundness and sphericity) from the Vimmerby Moraine, a prominent and accessible feature in southern Sweden dated using TCN to 14.4±0.9 ka. Our study was designed to test whether morphological characteristics can be used to discriminate in favour of the most light‐exposed boulders and minimize measurements of non‐exposed boulders. As expected, not all RSLBD ages can be attributed to the same depositional event, but the majority of the resulting ages provide a mean age of 13.0±1.5 ka, consistent with the cosmogenic nuclide dating of the Vimmerby Moraine. Despite the apparently successful TCN study, the luminescence–depth profiles measured in the buried surfaces of the sampled clasts indicate that >50% of these moraine boulders were exposed to light (and cosmic radiation) before final deposition, implying some (presumably small) TCN inheritance; seven of the 16 boulders identified as light exposed were sufficiently bleached to be useful for RSLBD. These results and their implications in regard to transport and deposition of the sampled cobbles are critically discussed and evaluated. [ABSTRACT FROM AUTHOR]

Accurate modelling and prediction of sediment transport in aquatic environments is essential for sustainable coastal and riverine management. Current capabilities rely on physical process-based numerical models and fine-scale sediment flux measurements. High-resolution hydroacoustic instrumentation has emerged as a promising tool for such measurements. However, challenges arise due to the inherent complexity of ultrasound scattering processes. This study introduces a numerical modelling using a point-particle approach to simulate the echoes backscattered by such instrumentation in sediment-laden flow conditions. The model considers geometric, statistical, particle cloud, and flow-induced effects on sediment velocity, concentration, and flux estimates using an acoustic concentration and velocity profiler as a reference. The model performance is assessed here under unidirectional constant flow conditions in terms of velocity, concentration, and time-resolved sediment flux estimates for a large range of the particles' advection speed and sampled volume sizes. Application to the estimation of the measurement accuracy of sediment flux in these flows is also considered, with a final error on the flux seen to be partially controlled by the residence time of particles within the sampled volumes. The proposed model provides insights into scattering processes and offers a tool for investigating robust sediment flux estimation techniques in various flow conditions. [ABSTRACT FROM AUTHOR]

The Laurentide Ice Sheet's (LIS) interior had a dynamic polythermal base, but the spatiotemporal variations of subglacial processes related to ice divide migration and other transient changes remain largely unknown, limiting our understanding of regional glacial dynamics. Previous studies focused on the regional glacial landform record, while ice sheet models lacked detailed parameterization within these regions, leading to an overestimation of cold-based subglacial conditions' extent and duration. In this study, glacial sediment dispersal patterns as identified by heavy minerals, clasts, and multivariate statistics of till matrix geochemistry were used to assess ice sheet dynamics within the Quebec–Labrador sector of the LIS. The earliest ice-flow phase produced and transported till across the study area (>175 km). However, major oxide data from till matrix geochemistry show a correlation with underlying bedrock, and this relationship is relatively common in areas of thin till cover and resistant bedrock lithologies. These results suggest a switch from an early phase of widespread erosion and long, sustained sediment transport to one of more limited erosion, perhaps abrasion dominant and shorter transport. Till compositional data and related dispersal patterns add supporting evidence to earlier ice sheet reconstructions based on ice-flow indicators and 10Be data together suggesting a transition from widespread uniform warm-based conditions during the earliest ice flow, followed by the development of an ice divide, its migration, and more sporadic warm-based conditions. Consequently, a thorough understanding of ice-flow history is essential for ice sheet modelling and future mineral exploration programs in inner ice sheet regions of the LIS. [ABSTRACT FROM AUTHOR]

Smoothed particle hydrodynamics (SPH) is a meshless, particle-based approach that has been increasingly applied for modelling of various fluid-flow phenomena. Concerning multiphase flow computations, an advantage of the Lagrangian SPH over Eulerian approaches is that the advection step is straightforward. Consequently, the interphasial surface can be explicitly determined from the positions of particles representing different phases; therefore, there is no need for the interface reconstruction step. In this review paper, we briefly recall the basics of the SPH approach, and in particular the physical modelling and numerical implementation issues. We also mention the weaknesses of the approach and some remedies to overcome them. Then, we demonstrate the applicability of SPH to selected interfacial flow cases, including the liquid column break-up, gas–liquid flow regimes in a channel capturing the transitions between them and the wetting phenomena. Concerning the two-fluid modelling, it is illustrated with sediment transport in the presence of surface waves. Various other applications are briefly recalled from the rich and growing literature on the subject, followed by a tentative list of challenges in multiphase SPH. [ABSTRACT FROM AUTHOR]

Understanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice‐sheet dynamics. Yet, direct data are sparse and difficult to acquire. Here, we employ ultra‐wideband radar to map high‐backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. Our backscatter analysis reveals that the basal ice in an area of ∼10,000 km2 is composed of along‐flow oriented sediment‐laden basal ice units connected to the basal substrate, extending up to several hundred meters thick. Three‐dimensional thermomechanical modeling supports that these units form via basal freeze‐on of subglacial water that originated from further upstream. Our findings suggest that basal freeze‐on, and the entrainment and transport of subglacial material play a significant role in an accurate representation of material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice‐sheet modeling. Plain Language Summary: We investigate the lowermost portion of the ice column of the Antarctic ice sheet, known as basal ice. This part holds crucial information about how the ice sheet behaves when it flows. Using the principle of echo‐location, we use radar technology to scan the ice in East Antarctica's Jutulstraumen drainage basin. We discover that a significant portion of the basal ice in this region is filled with sediment and can be several hundred meters thick. To better understand how this distinctive type of ice forms, we used a mathematical model that suggested that these ice units likely form when water underneath the ice is transported and refreezes at particular locations. Our findings highlight the importance of these freezing and mixing of materials from beneath the ice. Understanding where these ice units are located provides important information for ice‐flow models to ultimately better understand how the Antarctic ice sheet behaves in the future. Key Points: We have identified high‐scattering basal ice in Jutulstraumen Glacier's onset region using radar, reaching several hundred meters from the bedBackscatter analysis suggests that the basal ice units contain unstratified point scatters and cause little radio‐glaciological loss3D thermo‐mechanical modeling implies that freeze‐on of basal meltwater generated upstream likely initially formed the basal ice units [ABSTRACT FROM AUTHOR]

Sediment grains are progressively rounded during their transport down a river. For more than a century, Earth scientists have used the roundness of pebbles within modern sediment, and of clasts within conglomerates, as a key metric to constrain the sediment's transport history and source area(s). However, the current practices of assessment of pebble roundness are mainly qualitative and based on time-consuming manual measurement methods. This qualitative judgement provides the transport history only in a broad sense, such as classifying distance as "near" or "far". In this study, we propose a new model that quantifies the relationship between roundness and the transport distance. We demonstrate that this model can be applied to the clasts of multiple lithologies including modern sediment, as well as conglomerates, deposited by ancient river systems. We present field data from two Himalayan catchments in Nepal. We use the normalized isoperimetric ratio (IRn), which relates a pebble's area (A) to its perimeter (P), to quantify roundness. The maximum analytical value for IRn is 1, and IRn is expected to increase with transport distance. We propose a non-linear roundness model based on our field data, whereby the difference between a grain's IRn and the maximum value of 1 decays exponentially with transport distance, mirroring Sternberg's model of mass loss or size reduction by abrasion. This roundness model predicts an asymptotic behaviour for IRn , and the distance over which IRn approaches the asymptote is controlled by a rounding coefficient. Our field data suggest that the roundness coefficient for granite pebbles is 9 times that of quartzite pebbles. Using this model, we reconstruct the transport history of a Pliocene paleo-river deposit preserved at the base of the Kathmandu intermontane basin. These results, along with other sedimentary evidence, imply that the paleo-river was much longer than the length of the Kathmandu Basin and that it must have lost its headwaters through drainage capture. We further explore the extreme rounding of clasts from Miocene conglomerate of the Siwalik zone and find evidence of sediment recycling. [ABSTRACT FROM AUTHOR]

A high‐resolution wave model is crucial for accurate modeling of sediment and organic material transports, but its computational costs hinder direct coupling to an ecosystem model. We developed a machine learning model using long short‐term memory to simulate large‐scale, high‐resolution waves. Trained with numerical wave model (NWM) outputs and wind data from nine locations, our model successfully replicates NWM results for daily mean significant wave height and period in Chesapeake Bay with identical spatial resolution. Compared to the NWM, the data‐driven model has root‐mean‐square errors below 6 cm for daily mean significant wave height and 1 s for the wave period in the bay. It demonstrates excellent model skills and can accurately forecast daily mean significant wave height and period at NOAA wave stations comparable to NWMs. Using minimal wind data and having a short runtime, our data‐driven model shows promise as an alternative for wave forecasting and coupling with sediment and ecological models. Plain Language Summary: Accurately modeling sediment and organic transport necessitates the use of a high‐resolution numerical wave model (NWM). However, the computational expenses of running an NWM within an ecosystem model pose significant challenges. We conducted a study using a machine learning approach based on long short‐term memory to replicate the results of an NWM. The data‐driven wave model (DWM) was trained with the NWM outputs and wind data from nine locations. The trained DWM can replicate the NWM results of daily mean significant wave height and period in Chesapeake Bay with identical spatial resolution and the same predictive skill with a root‐mean‐square error of less than 6 cm and 1 s, respectively for the model domain. The model successfully forecasted daily mean significant wave height and period at NOAA wave stations, showing great forward prediction capability. Notably, the DWM only relied on a minimal amount of wind data from selected locations and had a short runtime. These findings indicate that machine learning is promising as an alternative approach to NWM for wave forecasting. Moreover, it can serve as an alternative wave model and be coupled to ecological models for simulating sediment transport, light attenuation, and resuspension of organic materials. Key Points: A machine learning‐based wave model reproduces the numerical wave model (NWM) results at the same spatial resolution with good accuracyThe data‐driven model, trained on daily significant wave height and period using NWM outputs, has comparable wave prediction skillThe fast‐running data wave model, driven by wind data from nine locations, can forecast waves and couple with sediment and ecological models [ABSTRACT FROM AUTHOR]

Feedbacks between sediment and plants in the submersed aquatic vegetation (SAV) beds of the Susquehanna Flats help modulate sediment delivery into the upper Chesapeake Bay from its major tributary (Susquehanna River). Recent modeling work has shown that SAV can steer the river plume, directly controlling sediment transport and fate. However, transport mechanisms likely differ between flood and non‐flood conditions and depend on event timing. An opportunity to evaluate these insights in the field occurred with several flood events in summer 2018. Sediment and biomass samples were collected after the flood in the large, continuous main SAV bed of the Flats and in smaller patches to the west of the main bed to evaluate the effect of SAV bed size (width). Sediment characteristics (grain size, organic content) and deposition rates were compared to previous observations during non‐flood conditions in the main bed in 2014–2015 and in the smaller patches in 2019. Overall, sediment deposition rates could be predicted by an empirical model including sediment load, vegetation biomass, and SAV bed width, reflecting the role of vegetation in steering the Susquehanna River plume and modulating sediment input to the upper Chesapeake Bay. Understanding spatiotemporal patterns of sedimentation is essential for realistic estimates of sediment and nutrient (especially nitrogen and carbon) storage in freshwater SAV systems, which have not received as much attention as their saltwater counterparts. [ABSTRACT FROM AUTHOR]

Fluvial discharge is a principal driver of suspended sediment (SS) transport in the Central Himalayan region, Nepal. The study examines the relationship between specific discharge at three hydrometric stations along the main Kali Gandaki (KG) River, four hydrometric stations on its tributaries with rainfalls across the entire basin and its sub basins, in relation to SS transport at a hydropower reservoir. Over the period of 2006–2017, the average monthly rainfall in June (388.39 ± 84.24 mm), July (674.91 ± 105.24 mm), August (571.81 ± 110.77 mm), and September (356.50 ± 104.39 mm) yielded an average of 2.469 ± 1.641, 12.952 ± 4.932, 12.629 ± 7.937, and 4.406 ± 2.363 megatons (Mt) of SS loads, respectively, flowing from the KG catchment into the hill-side dam reservoir. Results indicated that approximately 97% of SS was transported during the monsoon season (June–September). This corresponds to an estimated annual weathering rate in the basin of 4390 tons/km2/year, equivalent to 1.66 mm/year. Notably, both the specific direct runoff discharge and the monsoonal daily erosion rate during major rainfall events (> 30 mm/day) exhibited an upward linear trend with the basin's rainfall. [ABSTRACT FROM AUTHOR]

Shorelines face growing threats due to climate change and diminishing sand supply. Coastal headlands, common rocky features along coastlines, are crucial in shaping hydrodynamics and sediment transport. Yet, the influence of future climate conditions, including sea‐level rise (SLR) and intensified storm energy on complex shorelines with headlands has remained relatively unexplored. In this study, we model changes in hydrodynamics and headland bypassing under different SLR and higher storm wave scenarios. Our findings reveal the formation of circulation cells on both sides of a headland, where wave energy converges around the headland zone. Future climate conditions result in larger storm waves on the beach. However, SLR enhances nearshore currents through a landward shifting of the circulation cells, while higher storm waves intensify offshore flow currents due to the seaward movement of the cells. This effect, in turn, increases the potential for headland sediment bypassing. Plain Language Summary: Coastal headlands, prominent rocky features along open coastlines, play a crucial role in protecting nearby beaches from strong waves and erosion. They also affect how sand is exchanged between different beaches. We use a model to explore how future climate conditions including sea‐level rise (SLR) and larger storm waves influence coastal waves, littoral currents, and the transport of sand around headlands. Our findings reveal that headlands converge wave energy forming circulation flow cells. SLR results in stronger nearshore currents, driven by the landward movement of the rotating flow cells. In contrast, larger storm waves can move the rotating flow cells seaward, thereby increasing offshore current strength and the potential for sand transport around the headland. Understanding how coastal waves, flow and sediment transport change under future climate conditions will help determine coastal resilience. Key Points: The formation of circulation cells and wave energy convergence around headlands during storms reduce bottom shear stress at the beachSea‐level rise increases wave heights, currents, and bed shear stress in the nearshore because of landward shifting of the circulation cellsHigher storm waves expand the surf zone, shift circulation cells seaward, and enhance potential headland sediment bypassing [ABSTRACT FROM AUTHOR]

The 2021 Navalacruz wildfire occurred in a mountainous area in the Sistema Central (Spain). Despite having an average low severity index (dNBR), the loss of vegetation cover associated with the fire was responsible for a high rate of sedimentation in the rivers and streams. Additionally, the burned area affected up to 60 cultural heritage sites, including archaeological and ethnological sites, and damage ranged from burnt pieces of wood to the burial of archaeological sites. In the present work, we document and analyze the post-fire evolution in several rivers and streams. This is based on a field survey of infiltration rates, hydrodynamic modeling, and the study of channel morphological changes. Our analysis revealed how the first post-fire rains caused the mobilization and transport of ashes. This created hydrophobicity in the soils, resulting in large amounts of materials being transported to rivers and streams by subsequent medium- and low-magnitude storms. A hydrological and hydraulic model of the study catchments under pre- and post-fire conditions suggests that these trends are a consequence of a post-fire increase in flow rates for similar rainfall scenarios. In this respect, our estimates point at a significant increase in sediment transport capacities associated with this post-fire increase in flow rates. The combination of locally steep slopes with high-severity fire patches, and a considerable regolith (derived from pre-fire weathering), resulted in a series of cascading responses, such as an exacerbated supply of sand to the drainage network and the triggering of debris flows, followed by erosion and entrenchment. [ABSTRACT FROM AUTHOR]

Effects of bed material and downstream flow depth on bed evolution in a right-angled channel confluence were studied through laboratory experiments. Velocity field, water surface elevation, and bed profile were measured intermittently until the flow attained equilibrium. Sediment discharges at various locations of the confluence were estimated from bed levels. Six prominent bedforms were identified, and their characteristics were quantified. The sediment discharges from different channels were initially high but decreased to approximately zero as the flow attained equilibrium. Downstream flow depth influenced overall sediment transport in the system, including the main features of bed morphology. Overall erosion in the confluence reduced as the particle size of the bed material increased. In addition, the maximum scour depth occurred at the confluence edge, and, due to the sharp corner of the confluence, its location did not change with time. Results from the present experimental study can help validate numerical models and assist in the design of a right-angled confluence. This study is related to the hydraulics of man-made confluences with mobile beds and can be useful in the following practical applications. More accurate numerical models to predict maximum scour, bed morphodynamics, and sediment transport in man-made confluences can be developed using the detailed bed profile measurements at different time instants presented in this study. Note that available numerical models use sediment discharge formulas (e.g., Meyer-Peter-Muller, Van Rijn), which are for sediment flows in straight channels. The interplay between the three-dimensional flow field, developed bed shear stress, and sediment discharge can be explored. In addition, A man-made confluence with the mobile bed can be designed with findings from the present study. The bedforms corresponding to equilibrium flow depend on discharge ratio, confluence angle, flow conditions at the exit channel, and bed material characteristics. The major bedforms can be incorporated into the confluence geometry. [ABSTRACT FROM AUTHOR]

Following the eruption of the Taal Volcano in January 2020 and its continuous signs of unrest in the preceding years, this study delves into the investigation of sediment transport in the Pasig River, Philippines. The historical data of total suspended solids (TSS) and arsenic indicated a notable increase starting from the year 2020. The field measurements were conducted in February and March of 2022, two years after the eruption. Due to the observed homogeneity in the river's mixing, a refined 1D sediment transport model was developed. In this study, HEC-RAS modeling software was employed. The calibration process using the Laursen transport function yielded an impressive R2 value of 0.9989 for the post-eruption model. This predictive accuracy underscores the robustness of the developed model. The study's scope was further expanded by creating a model for February 2020, incorporating water quality data gathered by the Pasig River Coordinating and Management Office. The model simulation results showed peak TSS values of 120.63 mg/L and 225.15 mg/L in February 2022 and February 2020, respectively. The results of the study highlight the probable impact of geological events on sediment dynamics within the Pasig River, which could help manage and sustain ongoing river improvements. [ABSTRACT FROM AUTHOR]

The process of removing water from sewage sludge is particularly important due to its high content in the raw sludge. This translates into problems with the transport and storage of sediments. Additionally, high water content reduces the calorific value of the sludge. The methods for selecting the appropriate parameters for sewage sludge conditioning and filtration, based on the experimental data presented in this work, may allow for the optimization of sludge dewatering lines in small and large sewage treatment plants. The optimization of the dewatering process has a significant impact on the environmental and economic benefits, which consequently results in a decrease in the power costs of the devices used, flocculants, and sludge processing, and, above all, it contributes to the reduction in the negative impact on the environment. The use of mineral substances in the preparation of sewage sludge improves the effects of its dewatering in the pressure filtration process, as expressed in the obtained values of the final hydration and process efficiency. The use of polyelectrolytes alone significantly improves the effects of sewage sludge dewatering. In this work, the polyelectrolytes were supported by the addition of cement or zeolite. The conditioning of sewage sludge in combined methods using C-494 polyelectrolyte and minerals made it possible to reduce the compressibility coefficient to the range of 0.24–0.47 and, at the same time, to achieve the best results of sludge dewatering in the filtration process. The lowest hydration of 74.9% was achieved when polyelectrolyte and cement were added to the sludge, and this hydration was 6.5 percentage points lower compared to that of the non-filtered sludge. [ABSTRACT FROM AUTHOR]

The spatiotemporal variations in suspended sediment concentration (SSC) in the lower reaches of the Yellow River exhibit significant variability and are influenced by reservoir operations. Understanding the spatiotemporal distribution characteristics of SSC in water holds crucial implications for environmental protection and reservoir operation management. Based on daily-scale SSC monitoring data from four hydrological stations in the lower Yellow River, this study established an SSC remote sensing model applicable to Landsat series satellite data. The independent variable of the model, Rrs(NIR)/(Rrs(G) + Rrs(R) + Rrs(SWIR)), demonstrated sensitivity to water bodies with different SSC values. Distinctive spatiotemporal characteristics in sediment transport were observed across the lower Yellow River. Spatially, the SSC values in the Sanmenxia and Xiaolangdi reservoirs were notably lower than those in other river sections, averaging 1008.42 ± 602.83 mg/L and 1177.89 ± 627.95 mg/L, respectively. Over time, the majority of the river sections (96%) exhibited decreasing trends in SSC during 1984–2022, particularly in the downstream Xiaolangdi reservoir, with average SSC values of 4265.58 ± 1101.77 mg/L in the 1980s and 1840.80 ± 2255.15 mg/L in the 2020s. Seasonal variations in SSC were prominent, with higher summer concentrations, averaging 5536.43 ± 2188.77 mg/L (2020s summer) and 814.11 ± 158.27 mg/L (2020s winter). Reductions in SSC during 1984–2022 primarily occurred in summer, weakening its seasonal variability in the lower Yellow River. Water discharge emerged as a critical factor influencing suspended sediment transport, with SSC increasing in high-water-flow months. Following the construction of the Xiaolangdi reservoir, the relationship between SSC and water discharge at different stations underwent notable alterations. This study enhances our understanding of the spatiotemporal dynamics of suspended sediment transport in the lower Yellow River, providing valuable insights for utilizing long-term Landsat series data in the dynamic monitoring of river sediment transport. [ABSTRACT FROM AUTHOR]

In mountain regions, the impact of areas on the sediment conveyance can not only be described by their susceptibility to debris flow release, but also by their structural connectivity to the rivers. This generates the need to combine susceptibility and connectivity for accurate analyses of sediment transport. Our study exploits an approach developed by [Steger, er al. 2022; https://doi.org/10.1002/esp.5421] and upscales it to the South Tyrolean Dolomites region. The approach comprised the modeling of debris flow release susceptibility using an interpretable machine learning algorithm, the training of a logistic regression model, and the combination of the resultant classified maps to create a joint susceptibility-connectivity map. The results show the quantitative thresholds for the susceptibility probability and the Index of Connectivity (IC) that allow to discriminate between susceptible and not susceptible, as well as connected and disconnected areas, which are represented via a variety of maps. [ABSTRACT FROM AUTHOR]

River bifurcations are constituent components of multi-thread fluvial systems, playing a crucial role in their morphodynamic evolution and the partitioning of water and sediment. Although many studies have been directed at exploring bifurcation dynamics, the conditions under which avulsions occur, resulting in the complete abandonment of one branch, are still not well understood. To address this knowledge gap, we develop a novel 1D numerical model based on existing nodal point relations for sediment partitioning, which allows for the simulation of the morphodynamic evolution of a free bifurcation. Model results show that when the discharge asymmetry is so high that the shoaling branch does not transport sediments (partial avulsion conditions) the dominant branch undergoes significant degradation, leading to a higher inlet step between the bifurcates and further amplifying the discharge asymmetry. The degree of asymmetry is found to increase with the length of the downstream channels to the point that when they are sufficiently long, the shoaling branch is completely abandoned (full avulsion conditions). To complement our numerical findings, we also formulate a new analytical model that is able to reproduce the essential characteristics of the partial avulsion equilibrium, which enables us to identify the key parameters that control the transition between different configurations. In summary, this research sheds light on the fundamental processes that drive avulsion through the abandonment of river bifurcations. The insights gained from this study provide a foundation for further investigations and may offer valuable information for the design of sustainable river restoration projects. [ABSTRACT FROM AUTHOR]

The grain size 2 mm is the conventional border between sand and gravel. This size is used extensively, and generally without much physical justification, to discriminate between such features as sedimentary deposit type (clast-supported versus matrix-supported), river type (gravel bed versus sand bed), and sediment transport relation (gravel versus sand). Here we inquire as to whether this 2 mm boundary is simply a social construct upon which the research community has decided to agree or whether there is some underlying physics. We use dimensionless arguments to show the following for typical conditions on Earth, i.e., natural clasts (e.g., granitic or limestone) in 20 ∘ C water. As grain size ranges from 1 to 5 mm (a narrow band including 2 mm), sediment suspension becomes vanishingly small at normal flood conditions in alluvial rivers. We refer to this range as pea gravel. We further show that bedload movement of a clast in the pea gravel range with, for example, a size of 4 mm moving over a bed of 0.4 mm particles has an enhanced relative mobility compared to a clast with a size of 40 mm moving over a bed of the same 4 mm particles. With this in mind, we use 2 mm here as shorthand for the narrow pea gravel range of 1–5 mm over which transport behavior is distinct from both coarser and finer material. The use of viscosity allows the delineation of a generalized dimensionless bed grain size discriminator between "sand-like" and "gravel-like" rivers. The discriminator is applicable to sediment transport on Titan (ice clasts in flowing methane/ethane liquid at reduced gravity) and Mars (mafic clasts in flowing water at reduced gravity), as well as Earth. [ABSTRACT FROM AUTHOR]

The difficulties of measuring bedload transport in gravel-bed rivers have given rise to the morphological method wherein sediment transport can be inferred from changes in riverbed elevation and estimates of the distance traveled by sediment: its path length. Because current methods for estimating path length are time- and labor-intensive, we present a method to estimate a characteristic path length from repeat digital elevation models (DEMs of difference, i.e., DoDs). We propose an automated method to extract the spacing between erosional and depositional sites on the DoD by the application of variational mode decomposition (VMD), a signal processing method, to quantify the spacing as a proxy for path length. We developed this method using flume experiments where bed topography and sediment flux were measured and then applied it to published field data with physical path length measured from tracer measurements. Our sediment transport estimates were not significantly different than the measured sediment flux at lower discharges in the lab. However, we observed an underestimation of sediment flux at the higher discharges in the flume study. We interpret this as a limit of the method in confined settings, where sediment transport becomes decoupled from morphological changes. We also explore how the time between survey acquisitions, the morphological active width relative to the channel width, and DoD thresholding techniques affect the proposed method and the potential issues they pose for the morphological method in general. [ABSTRACT FROM AUTHOR]

Reliable descriptions of erosion events are foundational to effective frameworks relevant to the fate of tidal landscape evolution. Besides the rhythmic, predictable action of tidal currents, erosion in shallow tidal environments is strongly influenced by the stochastic wave-induced bottom shear stress (BSS), mainly responsible for sediment resuspension on tidal flats. However, the absence of sufficiently long, measured time series of BSS prevents a direct analysis of the combined tide- and wave-driven erosion dynamics and its proper representation in long-term morphodynamic models. Here we test the hypothesis of describing erosion dynamics in shallow tidal environments as a Poisson process by analysing, with the peak-over-threshold theory, the BSS time series computed using a fully coupled, bi-dimensional numerical model. We perform this analysis on the Venice Lagoon, Italy, taking advantage of several historical surveys done in the last 4 centuries, which allow us to investigate the effects of morphological modifications on spatial and temporal erosion patterns. Our analysis suggests that erosion events on intertidal flats can effectively be modelled as a marked Poisson process in different morphological configurations because the interarrival times, durations, and intensities of the over-threshold exceedances are always well described by exponentially distributed random variables. The resulting statistical characterization allows a straightforward computation of morphological indicators, such as the erosion work, and paves the way for a novel synthetic, yet reliable, approach for the long-term morphodynamic modelling of tidal environments. [ABSTRACT FROM AUTHOR]

A proper understanding of sediment resuspension and transport processes is key to the morphodynamics of shallow tidal environments. However, a complete spatial and temporal coverage of suspended sediment concentration (SSC) to describe these processes is hardly available, preventing the effective representation of depositional dynamics in long-term modelling approaches. Through aiming to couple erosion and deposition dynamics in a unique synthetic theoretical framework, we here investigate SSC dynamics, following a similar approach to that adopted for erosion. The analysis with the peak-over-threshold theory of SSC time series computed using a fully coupled, bi-dimensional model allows us to identify interarrival times, intensities, and durations of over-threshold events and test the hypothesis of modelling SSC dynamics as a Poisson process. The effects of morphological modifications on spatial and temporal SSC patterns are investigated in the Venice Lagoon, for which several historical configurations in the last 4 centuries are available. Our results show that, similar to erosion events, SSC can be modelled as a marked Poisson process in the intertidal flats for all the analysed morphological lagoon configurations because exponentially distributed random variables describe over-threshold events well. Although erosion and resuspension are intimately intertwined, erosion alone does not suffice to describe also SSC because of the non-local dynamics due to advection and dispersion processes. The statistical characterization of SSC events completes the framework introduced for erosion mechanics, and together, they represent a promising tool to generate synthetic, yet realistic, time series of shear stress and SSC for the long-term modelling of tidal environments. [ABSTRACT FROM AUTHOR]

Based on measurements with the Swiss plate geophone system with a 1 min temporal resolution, bedload transport fluctuations were analysed as a function of the flow and transport conditions in the Swiss Erlenbach stream. The study confirms a finding from an earlier event-based analysis of the same bedload transport data, which showed that the disequilibrium ratio of measured to calculated transport rate (disequilibrium condition) influences the sediment transport behaviour. To analyse the transport conditions, the following elements were examined to characterise bedload transport fluctuations: (i) the autocorrelation coefficient of bedload transport rates as a function of lag time (memory effect), (ii) the critical discharge at the start and end of a transport event, (iii) the variability in the bedload transport rates, and (iv) a hysteresis index as a measure of the strength of bedload transport during the rising and falling limb of the hydrograph. This study underlines that above-average disequilibrium conditions, which are associated with a larger sediment availability on the streambed, generally have a stronger effect on subsequent transport conditions than below-average disequilibrium conditions, which are associated with comparatively less sediment availability on the streambed. The findings highlight the important roles of the sediment availability on the streambed, the disequilibrium ratio, and the hydraulic forcing in view of a better understanding of the bedload transport fluctuations in a steep mountain stream. [ABSTRACT FROM AUTHOR]

The presence of a late Quaternary ice sheet/ice shelf over the East Siberian Sea has been proposed in several papers. Here, we further document its duration/resilience based on the sedimentary, bulk mineralogical, and geochemical (organic matter content and its stable isotopic composition, U‐Th series) properties of a core raised from the southernmost Mendeleev Ridge. The chronostratigraphy of the studied core was mainly built from the 230Th excess (230Thxs) distribution and decay downcore. At the core‐top, peaking 230Thxs values during the early MIS 3 and mid‐MIS 1 encompassing an MIS 2 hiatus were observed. As documented in several papers, these peaks suggest seasonally open ice conditions over proximal continental shelves. Below, the interval spanning MIS 4 and possibly MIS 5d records major ice‐rafting events illustrated by overall high coarse‐fraction contents. Underlying MIS 5e, down to MIS 11, the sediment depicts relatively low sand (1.7±2.5 dw%), high clay (33.5±4.7 dw%), and very low organic carbon (0.10±0.06 dw%) contents, and low δ13Corg values (−24.3±0.9‰). This section is interpreted as recording fine sediment transport by deep currents and/or meltwater plumes below a resilient ice cover, only interrupted by a few short‐duration events. These events include (i) detrital carbonate pulses assigned to deglacial events along the NW Laurentide Ice Sheet margin (Termination (T) III), and (ii) intervals with some planktonic foraminifer occurrences, likely relating to their advection from open areas of the Arctic Ocean (MIS 5e, 9 and 11). All Terminations, but TII and the early MIS 3, show peaking Mn/Al values linked to the submergence of Arctic shelves under a rising sea level. We conclude that the resilient ice cover, likely an ice shelf, has been present over the southern Mendeleev Ridge during most of the interval after the Mid‐Pleistocene Transition and was favoured by the low summer insolation of the MIS 14 to 10 interval. [ABSTRACT FROM AUTHOR]

Floods are among the most common natural disasters responsible for severe damages and human losses. Numerically produced data, managed by user-friendly tools for geographically referenced data, have been adopted to increase preparedness and reduce vulnerabilities. This paper describes the locally sensed and numerically produced data that characterize a flood event that occurred in February 2016 in the Portuguese Águeda River, referred to as Agueda.2016Flood for short. The data were managed through the RiverCure portal, a collaborative web platform connected to a validated shallow-water model featuring modelled dynamic bed geometries and sediment transport. The dataset provides a synthesis of topo-bathymetric, hydrometric and numerically produced data from a calibrated hydrodynamic model. Due to the lack of measured hydrometric data near the city, the numerically produced data are crucial for a complete description of the flood event. The Agueda.2016Flood dataset constitutes a complete validation test for flood forecasting models and a tool to better mitigate floods in this river and in similar rivers. Thus, Agueda.2016Flood is a relevant dataset for Águeda River stakeholders as well as for the community of flood modellers, as it provides a well-documented validation event for forecasting tools. The dataset can be accessed at 10.4211/hs.937927473a3a4e66a07a2e2fdd9d581e (Ricardo et al., 2024). [ABSTRACT FROM AUTHOR]

One of the challenges in using Manning’s equation lies in accurately determining Manning’s roughness coefficient, especially due to sediment transport. The condition of sediment transport within a specific section of a river can be in equilibrium, meaning that the amount of sediment entering and exiting the segment is balanced or it can be in non-equilibrium, where there is an imbalance between the sediment entering and leaving the segment. Experiments were carried out in the laboratory to simulate both transport conditions, one involving sediment feeding (equilibrium condition) and the other without sediment feeding (non-equilibrium condition). A total of 180 mean velocity profiles were measured using an acoustic doppler velocimeter (ADV) in fixed and movable bed flows. The present experiment was combined with theoretical approaches to evaluate Manning’s coefficient in open channels under sediment transport-flow conditions and reach conclusive results. The shape of the velocity profile, u/U, for flows over a movable bed with sediment feeding is “slender” compared to those without sediment feeding. The presence of sediment transport affects the shape of the velocity profile, especially in the inner region, influencing Manning's roughness coefficient. This coefficient can be determined from two-point velocity measurements at z/H = 0.1 and 0.2 for fixed and movable bed flows with and without sediment feeding, respectively. On average, sediment feeding increases the coefficient by 19% compared to the non-sediment feeding case. [ABSTRACT FROM AUTHOR]

The rapid expansion of laver (Porphyra yezoensis) cultivation on lower tidal flats has become integral to the local economy, yet it also raises concerns regarding its potential impact on the morphological evolution due to increasing human activities. This study utilizes integrated near-bed field measurements to assess morphological dynamics and quantify sediment erosion processes, highlighting the significant impact of laver harvest on tidal flat stability. Our results show that erosion and bed coarsening in the cultivated areas experienced a notable intensification immediately after harvest, with net erosion in cultivated areas reaching approximately −38.2 mm during the first tide post-harvest, markedly higher—more than an order of magnitude—compared to adjacent uncultivated areas. The erosion rate notably spiked with the average bed level change rate increasing to −13.8 × 10−4 mm/s, compared to a rate of +0.3 × 10−4 mm/s during the unharvest period. Subsequently, the cultivated areas entered a recovery phase with a deposition amount of +12.5 mm, while the net cumulative erosion thickness throughout the entire observation period was −25.2 mm. The cultivation method, characterized by consistent harvests every 10 days, means that even minor erosion from continuous harvests can escalate into significant degradation. This study suggests that long-term cultivation cycle practices may result in irreversible changes to the depositional environment, potentially jeopardizing the habitat viability and ecological function. Sustainable agricultural strategies, including site selection, infrastructure planning, monitoring environmental changes, ecological assessments and sustainable practices, are recommended to mitigate the negative impacts of cultivation on regional stability and preserve the coastal ecological balance. [Display omitted] • Post-harvest erosion rates illustrate dramatic sediment loss in cultivated areas. • Regular harvesting practices lead to cyclic environmental degradation. • Strategies for sustainable cultivation enhance tidal flat ecosystem resilience. [ABSTRACT FROM AUTHOR]

Soil erosion rates after wildfire are strongly controlled by intrinsic properties such as topography, weather, climate, soil, and vegetation. These landscape and hydroclimatic properties are important in determining post-fire erosion rates; however, their influence on post-fire erosion and their interaction with the intensity of a wildfire remains uncertain. A key limitation in resolving this uncertainty is the lack of conceptual models and frameworks for organising data related to the geomorphic sensitivity of landscapes to wildfire. Our aim is to develop a framework for consolidating understanding of post-fire erosion in the context of hydroclimatic conditions which contribute to system states, for example soil and vegetation properties, and wildfire regime. The framework is developed around a simple conceptual model where the change in erosion due to wildfire is a product of change in runoff generation and sediment supply, which is strongly related to landscape net primary productivity (NPP). We hypothesised that geomorphic sensitivity to wildfire should vary as a unimodal humped relationship across a gradient of NPP, peaking at an intermediate level. To develop this framework and to test the hypothesis, we first review intrinsic soil and vegetation properties related to the supply and transport of sediment from burned and unburned hillslopes. Net primary productivity is systematically related to these intrinsic properties because it integrates many processes involved in soil and vegetation development. Empirical data indicate a trend in the change in surface runoff generation with NPP after wildfire, peaking at an NPP of approximately 15 Mg C ha−1 y−1. A simple model of fuel availability and soil heating are correlated with a similar "humped" trend in sediment supply. These results are consistent with our conceptual model, which indicates that sediment supply and runoff contribute towards a distinct peak in wildfire effects on erosion at an intermediate level of NPP. We propose that landscapes of intermediate NPP typically have the highest quantity of fuel available to burn, which cause large changes to the soil surface properties. Landscapes at intermediate NPP also tend to produce intrinsic soil and vegetation properties that promote erosion after wildfire. The interplay between these short and long-term landscape characteristics is strongest at intermediate levels of NPP. Our proposed biogeographic model of geomorphic sensitivity to wildfire was supported by erosion data from burned hillslope and zero-order catchments studies from a range fire-prone landscapes in Australia and North America. Our proposed conceptual model will help identify areas most vulnerable to post-fire erosion changes. [ABSTRACT FROM AUTHOR]

Algeria, a semi-arid Mediterranean country, is distinguished by a more marked interannual variability in solid inputs compared to liquid inputs. This study aimed to comprehensively analyze hydrometeorological variables, such as rainfall, suspended sediment load, and flood flows in the Wadi Mina basin (6048 km2), using both traditional and advanced statistical techniques. These techniques included the MK trend tests MMK, and TFPWMK, as well as newer methods such as ITA and IPTA. To identify breakpoints, the CUSUM test and the SQ-MK test were used. The study was based on monthly data covering 40 years of rainfall (1970–2010) and 41 years of data on flood flows and suspended sediment load (1969–2010). The results indicated stable annual rainfall across the stations, suggesting a consistent rainfall regime over time. However, notable variability in sediment loads and flood flows was observed, with stations like Ain Hamara, Sidi Aek Djilali, and Wadi El Abtal displaying marked decreases in annual sediment loads, hinting at effective erosion control or natural attenuation of erosive processes. In contrast, a significant increase in flood events was recorded at Ain Hamara, attributed to climatic fluctuations or land use changes affecting runoff. Monthly analyses further demonstrated the enhanced sensitivity of ITA and IPTA over traditional methods, effectively uncovering subtle trends not detected by MK, MMK, and TFPWMK. For example, increasing rainfall trends during winter at Takhmert station and significant sediment transport patterns at Ain Hamara during colder months suggested dynamic seasonal hydrological behaviors. Additionally, critical insights into abrupt changes were revealed through CUSUM and SQ-MK tests, such as a pivotal shift in flood regimes at Takhmert in 2003 and a critical change in rainfall patterns at Ain Hamara in 2008, necessitating adjustments in water management and agricultural practices. [ABSTRACT FROM AUTHOR]

We present the implementation of a new fully distributed multiclass soil erosion module. The model is based on a 2D finite volume solver (Iber+) for the 2D shallow water equations that computes the overland flow water depths and velocities. From these, the model evaluates the transport of sediment particles due to bed load and suspended load, including rainfall-driven and runoff-driven erosion processes, and using well-established physically-based formulations. The evolution of the mass of sediment particles in the soil layer is computed from a mass conservation equation for each sediment class. The solver is implemented using High Performance Computing techniques that take advantage of the computational capabilities of standard Graphical Processing Units, achieving speed-ups of two orders of magnitude relative to a sequential implementation on the CPU. We show the application and validation of the model at different spatial scales, ranging from laboratory experiments to meso-scale catchments. • A multiclass soil erosion module is implemented in a 2D shallow water model. • Sediment transport is modelled considering rainfall and runoff driven processes. • The GPU parallelization of the code enables its application to complex catchments. [ABSTRACT FROM AUTHOR]

The formation and evolution of coastal dunes result from a complex interplay of eco-morphodynamic processes. State-of-the-art models can simulate aeolian transports and morphological dune evolution under certain conditions. However, a model combining these processes for coastal engineering applications was not yet available. This study aims to develop a predictive tool for dune development to inform coastal management decisions and interventions. The aeolian sediment transport model AeoLiS is extended with functionalities that allow for simulations of coastal landforms. The added functionalities include the effect of topographic steering on wind shear, avalanching of steep slopes and vegetation processes in the form of growth and wind shear reduction. The model is validated by simulating four distinct coastal landforms; barchan-, parabolic-, embryo dunes and blowouts. Simulations, based on real-world conditions, replicate the landform formation, migration rates and seasonal variability. • Dune shaping processes are implemented into AeoLiS enabling landform simulations. • Four distinct landform types are simulated utilizing AeoLiS. • AeoLiS replicates accurate landform shapes and dynamics under real-world conditions. • Capabilities added to AeoLiS enable its use for a range of engineering applications. [ABSTRACT FROM AUTHOR]

The main purpose of the research was to develop appropriate tools for forecasting the effects of storms. The use of the high-resolution SWAN wave model powered by AROME wind fields to couple it with the SWANOneSed sediment transport model and a model using the Ruggiero formula, predicting the extent of the flooded shore, allowed the development of reliable tools for forecasting the effects of storms. Validation using qualitative analysis showed that the results obtained from the coupled SWANOneSed model are characterized by high consistency in intensification and direction of changes. The model using the Ruggiero formula obtained a high value of the correlation coefficient, i.e. 0.970 and 0.992 for the Satbałtyk-Xbeach model data, based on the Hunt&Mase formula, and the high-resolution Pleiades Neo satellite data, respectively. By combining models from the SWAN family, i.e. the SWAN and SWANOneSed wave model and a model using the Ruggiero formula, it was possible to obtain reliable and compatible tools enabling an uninterrupted and synchronized operational process of generating forecasts of storm effects. [Display omitted] • The coupling of the SWAN & SWANOneSed enables reliable and operational forecasting. • Measured & terrain surveyed data-fed model are consistent with other observed data. • Formula van Rijn reliably reproduces sediment transport in various types of coasts. • The Ruggiero formula is applicable in various parts of the Polish coast. [ABSTRACT FROM AUTHOR]

— The sediment transport plays a major role in every aquatic ecosystem. However, the lack of instruments to monitor this process has been an obstacle to understanding its effects. We present the design of a single sensor built to measure water velocity, suspended sediment concentration and depth in situ , and how to associate the three variables to estimate and analyse sediment transport. During the laboratory calibrations, the developed instrument presented a resolution from 0.001 g/L to 0.1 g/L in the 0–12 g/L range for the measurement of suspended sediment concentration and 0.05 m/s resolution for 0–0.5 m/s range and 0.001 m/s resolution for 0.5–1 m/s range for the measurement of water velocity. The device was deployed for 6 days in an estuarine area with high sediment dynamics to evaluate its performance. During the field experiment, the sensor successfully measured the tidal cycles and consequent change of flow directions, and the suspended sediment concentration in the area. These measurements allowed to estimate water discharge and sediment transport rates during the different phases of tides, and the daily total volume of water and total amount of sediment passing through the estuary. • Development of an instrument for in-situ continuous monitoring of sediment transport. • Methodology to calibrate the sensor for flow velocity and sediment concentration. • Field experiment in an estuarine environment to measure hydraulic dynamics. • Measurement of the stream flow inversion during high and low tides. • Estimation of water discharge and sediment transport rate. [ABSTRACT FROM AUTHOR]