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A one-dimensional morphodynamic model was improved to study the unsteady flow and sediment transport processes in a tail reach of the Yellow River estuary (YRE). In this model, the modified equations for flow hydrodynamics take the effects of sediment concentration and bed evolution into consideration. The improved model was validated using measurements in the tail reach of the YRE for the years 2003 and 2015, and the model showing an excellent data fit for discharge, water level, suspended sediment concentration and the cumulative volume of channel evolution. The effect of different cross-sectional spacings was also studied using the model results in the tail reach, with various numerical tests of the 2015 flood event conducted. It was found that an appropriate cross-sectional distance of less than 3.14 km should be adopted when simulating the process of bed deformation. Moreover, the interaction between runoff and tide in 2015 was studied on the basis of the simulated water levels and an empirical relation for the location of tidal limit was established. The results show that the tidal limit in 2015 was 15.84 km downstream of Xihekou.

As one of the most important margin seas around the west Pacific, the eastern China seas are important sink for terrigenous materials and forms multiple geology structures. So research the composition and spatial distribution of sediments could help us to understand the dynamics mechanism of the marine sedimentary environment, further to comprehend the land-sea interaction process. Based on high spatial resolution sediment survey in the eastern China seas, the distribution diagram of the sediment types was compiled to reveal the space regularities of sediment. In this study, the Principal Component Analysis (PCA) method was used to identify the controlling factors that are the main controls of the sediment distribution in the study area, which revealed three factors (F1, F2 and –F1) representing grain size categories of >5.75φ, 4.25–5.75φ and 1.50–3.00φ, respectively. F1 represents fine sediments (>5.75φ), -F1 represents coarse sediments (1.50–3.00φ), and F2 represents intermediate-sized sediments (4.25–5.75φ). The sediment transport patterns of the different grain size categories in the eastern China seas are discussed in the context of a comprehensive analysis of sediment grain size composition, material sources, flow patterns, and other factors. The results show that fine-grained sediments represent a “distant” sink of terrigenous material that formed in a stable and low-energy sedimentary environment. The coarse sediment deposits were formed in the late Pleistocene when the hydrodynamic conditions were relatively strong, and the intermediate-sized sediments were distributed in an area with a high concentration of suspension representative of mid-strength hydrodynamic conditions.

Wind-blown sand is one of the key factors affecting the evolution of sediment transport, erosion, and deposition in rivers crossing desert areas. However, the differences and complex variations in the spatial and temporal distribution of the underlying surface conditions are seldom considered in research on the river inflow of wind-blown sand over a long time period. The Yellow River contains a large amount of sediment. The Ningxia–Inner Mongolia reach of the Yellow River was selected as the research area of the current study. The reach flows out of Heishanxia and then flows through the Tengger, Hedong, Ulan Buh, and Kubuqi Deserts. In the current study, the wind speed, vegetation coverage, and sand matter on the river basin's surface were analyzed from the perspectives of the river basin surface and riverbank line. The vegetation coverage of the river basin's surface was calculated using the normalized difference vegetation index. Based on the types of sand matter, vegetation coverage, and other underlying surface conditions, the loose particle sediment transport efficiency was determined, the Lettau and Lettau formula for the sediment transport rate was modified, a surface wind-erosion sand flux model was established, and the amount of wind-blown sand transported into the Ningxia–Inner Mongolia reach was calculated. The results show that, from 1981 to 2014, the annual average amount of wind-blown sand transported into the main stream and tributaries of the Ningxia–Inner Mongolia reach of the Yellow River were 7,310,000 and 13,190,000 t, respectively. The Shizuishan–Bayangole reach received 51% of the total wind-blown sand that transported into the main stream, while the tributaries in the Shidakongdui area were the most important source wind-blown sand, providing 74% of the total wind-blown sand inflow from the tributaries. In recent years, the amount of sand transported into the river of the mainstream and tributaries of the Ningxia–Inner Mongolia reach of the Yellow River has significantly decreased from 1981 to 2002, particularly in 1993–2002, which is mainly the result of the weakening wind speed, increasing vegetation coverage, and embankment construction. More specifically, environmental protection policies led by the government, such as “returning farmland to forest”, have played an important and positive role. Therefore, when regulating the water and sediment in the Ningxia–Inner Mongolia reach of the Yellow River, the issue of wind-blown sand deposition into the river should be fully considered in water and sediment regulation.

Selective removal of particles and nutrients by water erosion is a key factor in soil erosion studies. Most agricultural soils are located on gentle slopes where fertility is high; however, until now, the main attention on sediment transport mechanisms was paid to high-slope gradients, where soil erosion is intense, but soils are less productive. Despite the importance of sediment size distribution (SSD) and transport mechanisms under unsteady-state conditions, few studies have been done on this issue. Higher sediment concentrations in the early stages of the runoff indicate the need to deal with unsteady-state conditions. To address this issue, sheet erosion experiments were done using a 0.2 m by 1 m tilting flume under controlled laboratory conditions. Six inflow rates (75, 100, 125, 150, 175, and 200 mL/s) were applied on two contrasting soils, including an adjacent agricultural soil and a not cultivated soil (namely Cropland soil and Control soil, respectively) at two low slope gradients (1.5% and 2%). No rill formation was observed during the experiments. The sediment-laden runoff was sampled during unsteady-state flow to determine the SSDs and sediment transport mechanisms of eroded particles for unsteady-state conditions. The results indicated different trends in the selective removal of sediment particles depending on hydraulic conditions and soil aggregate size. The contribution of suspension-saltation (SS) to the total sediment load for the Cropland and Control soils varied from 22% to 68% and from 35% to 59%, respectively, while up to 78% and 65% of soil particles were transported by bed load (BL), respectively. However, SS and BL indicated a reverse trend with stream power. The Cropland soil showed a single peak in the SSD at low stream powers because of the selective removal of fine particles (0.042 mm), whereas the SSD was shifted to a bimodal distribution at higher stream powers with the selective depletion of both fine (≤ 0.084 mm) and coarse (1.5 mm) particles. The Control soil experienced a unimodal SSD in a range of sizes between 0.109 and 0.175 mm for all stream powers. The findings of the current study highlight the need for further study on the erosion of low-slope agricultural soils, where small stream powers can remove fine and fertile soil particles.

Coastal Louisiana has the nation's most fragile and valuable wetlands, whose loss represents 80% of the total losses in the United States. The severely restricted mobility of conventional shoreline protection structures makes them impossible to be redeployed. The Wave Suppression and Sediment Collection (WSSC) system is a novel technology of high mobility and compatible with existing shoreline protection technologies. Previous laboratory studies on WSSC showed great potential for wave reduction and sediment collection. The current study aimed to optimize the design parameters of WSSC using a validated computational model. A computational fluid dynamics (CFD) model was developed and validated using experimental data from the previous laboratory study. Then, a parametric analysis was conducted with a focus on the performance optimization of wave reduction and sediment collection with respect to pipe diameter and face slope. Simulation results showed that the wave reduction efficiency decreased with increasing pipe diameter and face slope. In contrast, the sediment transport efficiency was enhanced by increasing pipe diameter but was not affected significantly by varying face slopes.

The Huangmaohai Estuary (HE) is a funnel-shaped microtidal estuary in the west of the Pearl River Delta (PRD) in southern China. Since China's reform and opening up in 1978, extensive human activities have occurred and greatly changed the estuary's topography, and modified its hydrodynamics. In this study, we examined the morphological evolution by analyzing remote sensing data with ArcGIS tools and studied the responses of hydrodynamics to the changes in topography from 1977 to 2010 by using the Delft3d model. We took the changes in estuarine circulation during neap tides in dry seasons as an example. The results show that human reclamation caused a narrowing of the estuary, and channel dredging deepened the estuary. These human activities changed both the longitudinal and lateral estuarine circulations. The longitudinal circulation was observed to increase with the deepening and narrowing of the estuary. The lateral circulation experienced changes in both the magnitude and pattern. The momentum balance analysis shows that when the depth and width changed simultaneously, the longitudinal estuarine circulation was modulated by both the channel deepening and width reduction, in which the friction, pressure gradient force, and advection terms were altered. The analysis of the longitudinal vortex dynamics indicates that the changes in the vertical shear of the longitudinal flow, lateral salinity gradient, and vertical mixing were responsible for the change in the lateral circulation. The changes in water depth are the dominant factor affecting lateral circulation intensity. This study has implications for sediment transport and morphological evolution in estuaries heavily impacted by human interventions.

The morphodyamics of back-barrier tidal basins have been extensively investigated by numerical modelling, but the influence of mouth islands (which may be submerged under future sea level rise) has been rarely explored. Using the Dongshan Bay in southern China as a reference site, we explore numerically the effects of geological constraints (i.e., islands) on the long-term morphodynamics of back-barrier basins. Model results indicate that the spatial configuration of mouth islands can considerably affect the morphological development of tidal basins. The presence of mouth islands can increase both the current velocity and the residual current by narrowing the inlet cross-sectional area, resulting in more sediment suspension and transport. Meanwhile, erosion tends to occur in the tidal basin and sedimentation occurs in the ebb-delta area, and the erosion (or sedimentation) volume is larger with the presence of more mouth islands. Further, the spatial distribution of mouth islands can also considerably affect tidal basin evolution: the basin-side mouth islands tend to cause more basin erosion with higher tidal currents and more sediment transport, while the delta-side ones may play a hindering role resulting in sediment deposition in the basin. Finally, larger tidal prisms are observed in basins with more mouth islands and those with basin-side mouth islands, suggesting that the number and location of mouth islands can also affect the empirical relation between tidal prism and inlet cross-sectional area. This modelling study furthers the understanding of barrier basin morphodynamics affected by mouth islands and informs management strategies under a changing environment.

The Great Lakes are non-tidal, but experience significant water level fluctuations at hourly, seasonal, and decadal scales. A rise of 0.83 m was observed between 2013 and 2020 on Lake Erie with the annual water level near the previous record high of 174.89 m set in 1986. In response to elevated water levels, barrier beach-ridges located on the eastern shore of the Point Pelee foreland, in the Lake Erie’s central basin, experienced accelerated erosion including overwash and breaching, removal or burial of vegetation, and damage to infrastructure and sensitive habitat. Historical aerial imagery between 1931 and 2020 and annual average lake levels between 1920 and 2020 were examined to characterize barrier retreat and breach initiation, expansion, and closure. Results indicate that the barriers have transgressed at a rate of >1 m y−1, but the rate of transgression and progradation, overwash, and breaching are dependent on decadal-scale variations in water level. Ephemeral breaches and delta deposits were found to be a significant source of landward sediment transport if breaches remained open for multiple years. This may represent a self-reinforcing cycle that promotes breach fill-in processes, even during high lake levels, and increases the barrier width and resiliency in response to further lake level fluctuations. While common patterns of barrier dynamics were found throughout the time series, human impacts may modify historic barrier transgression rates and breach and recovery processes.

International audience; In order to optimize ship navigation in the macrotidal Gironde Estuary, a recent project funded by the port of Bordeaux aims at better understand and forecast hydrodynamic and fine sediment transport within the estuary. In the framework of this project, a two-dimensional hydro-sedimentary model is built. The model includes hydrodynamic forcings, mixed-sediment transport, and consolidation processes. The harmonic analysis of the astronomical tides reveals a strong distortion of the tidal wave inducing the growth of overtide constituents and the non-significant effect of tide-surge interactions in annual-scale prediction. Depending on hydrological conditions, river discharge can considerably alter the model accuracy due to the migration of the turbidity maximum zone modifying the bottom roughness. Comparison with measurements shows the ability of the model to reproduce suspended-sediment concentrations in the central Estuary. Sensitivity of the model to sediment features has also been discussed in regard of suspended-sediment concentrations and fluid mud deposits. The model will be further coupled with ship squat predictions and a morphodynamic model.p { margin-bottom: 0.25 cm; line-height: 115%; }

Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurements carried out on mobile bed rills (grain resistance and sediment transport) and the values estimated by flow resistance equation (grain resistance) for fixed bed rills in the same slope and hydraulic conditions; (iii) the Γ function relationship was calibrated using measurements carried out on mobile bed rills and the data of Jiang et al. (2018). Results This analysis demonstrated that the effect of sediment transport on rill flow resistance law is appreciable only for 7.7% of the examined cases and that the theoretical approach allows for an accurate estimate of the Darcy-Weisbach friction factor. Furthermore, for both fixed and mobile beds, the mean flow velocity was independent of channel slope, as suggested by Govers (1992) for mobile bed rills. Conclusions The investigation highlighted that the effect of sediment transport on rill flow resistance is almost negligible for most of the cases and that the experimental procedure for fixing rills caused the unexpected slope independence of flow velocity.

This chapter discusses the factors that have led to an increasing interest in the human impact in geomorphology, and then discusses the literature that appeared between c. 1960 and 2000. These developments were in four main areas: (i) intellectual and policy-related; (ii) technological developments that alter geomorphological processes; (iii) demographic trends; and (iv) proliferation of techniques for the study of landform and process change. Much work was undertaken on landforms produced by construction and excavation. Interest also developed in accelerating ground subsidence, which is a widespread phenomenon that creates engineering problems. Indeed, with increasing exploitation of tundra areas for such activities as oil exploitation, there was an increasing interest in the problems associated with permafrost. Rivers have also been greatly impacted. Humans have modified sediment transport by rivers in two ways. First, as a result of accelerated soil erosion, the delivery of sediment to rivers has increased. Secondly, burgeoning dam construction has caused sediment to be trapped in reservoirs. Far-reaching changes in channel form have been produced by land-use and land-cover changes. In addition to non-deliberate changes to river systems, there have been a whole range of deliberate modifications (e.g. channelization). Some valley bottoms areas have suffered from accelerated sedimentation while others have become incised with gullies (‘arroyos’). Studies have indicated an increasing incidence of mass movements. These have been attributed to such factors as deforestation, road cuts, changes in slope drainage and irrigation of farm land. Much work has also been undertaken on wind erosion of dryland surfaces. Human activities, most notably air pollution, have changed the nature and rate of weathering, although enhanced weathering by salt can also be accelerated by irrigation. Large numbers of people live in coastal zones, and have had a major impact on coastal landforms and processes. Many of the world's shorelines have been eroding and the complex mix of causes, natural and anthropogenic, that could be responsible have been analysed. Finally, since the 1980s there has been a growing realization of the importance of global heating for geomorphological phenomena.

Coasts are among the most intensely used environments on the planet, but they also present dynamic and unique hazards including flooding and erosion. Sea level rise and changing wave climates will alter patterns of erosion and deposition, but some existing coastline evolution models are unable to simulate these effects due to their one-dimensional representation of the systems, or of sediment transport processes. In this paper, the development and application of the Coastline Evolution Model 2D (CEM2D) is presented, that incorporates these influences. The model has been developed from the established CEM model and is capable of simulating fundamental cause-effect relationships in coastal systems. The two-dimensional storage and transport of sediment in CEM2D, which is only done in one-dimension in CEM, means it is also capable of exploring the influence of a variable water level on sediment transport and the formation and evolution of morphological features and landforms at the meso-scale, from 10 to 100 years and over 10 to 100 kilometres. The model sits between one-dimensional and three-dimensional models, with the advantage of increased complexity and detail in model outputs compared to the former, but with more efficiency and less computational expense than the latter.

Clay minerals preserved in marine sediments carry important information about sediment transport processes from sources to sinks. To reveal the dynamic transport processes of clay minerals and related controlling factors in the southern South China Sea, spatiotemporal variations of clay mineral assemblages from previous studies (Cores MD05-2893, CG2, SO18287-3, MD01-2393, SO18383-3, and MD97-2150) are integrated to assess their controlling factors over the past 30 ka. Based on the smectite/(illite + chlorite) ratio in six cores, we found that the clay mineral variations on the continental slope off Sunda Shelf (Cores MD05-2893, CG2, and SO18287-3) have been controlled by the sea-level changes during the last glacial sea-level lowstand and by the East Asian monsoon during the Holocene sea-level highstand periods. Meanwhile, the clay mineral variations on the continental slope off the Mekong River (Cores MD01-2393, SO18383-3, and MD97-2150) have been driven by the chemical weathering in the Mekong River basin that associates with the East Asian summer monsoon evolution. Accordingly, we conclude that the glacial-interglacial variation of clay minerals in an integrated picture of the southern South China Sea region since the Last Glacial Maximum has been mainly controlled by sea-level change and East Asian monsoon evolution. However, these controlling factors play independent roles in different parts of the southern South China Sea, which appears more heterogeneous than generally expected.

A comprehensive understanding of the sedimentation dynamics within Lake Winnipeg (surface area: 23,750 km2) and its role in sediment transport in the downstream river system was achieved by determining the properties of lake bottom sediment and patterns of sediment accumulation rates and by constructing a conceptual total (i.e., organic and inorganic) sediment budget. Net deposition was the governing process in the South and North Basins, whereas transportation dominated in the Narrows. The largest fluvial source of sediments to the lake, the Red River, supplies 35% of the total sediment load. Although accumulation rates in profundal zones progressively decreased northward from this source at the south end of the lake, high accumulation rates with low inventories of fallout radionuclides in the northern margin of the North Basin indicate a second sediment source, which was determined to be erosion of north shore banks, which accounts for up to 50% of the total sediment load to the lake. The nearshore-offshore gradient in bottom sediment properties in the North Basin confirmed that the signature of this source can reach at least 20 km southward into the lake. However, the properties of bottom sediments, sedimentation dynamics, and sediment budget suggested that some of the materials eroded from the north shore are exported without interaction with the lake bottom and this local sediment source is the dominant source for the downstream river system. It was concluded that Lake Winnipeg effectively disconnects the downstream Nelson River from sediment transport processes in its upstream watershed (953,250 km2).

International audience; The current study focuses on the issue of the decrease in sediment discharge to the Mediterranean Sea by the largest river in Algeria, the Wadi Cheliff (i.e. Cheliff River). This study clarifies the effect of climatic and anthropogenic factors on the changes in the sedimentary dynamics of the Cheliff River discharging to the sea. The data used (rainfall, water discharge, and sediment discharge) concern the Sidi Bel Attar gaging station on the Cheliff River, only 18 km from discharge to the Mediterranean Sea. A power-type statistical regression model was used to fill the 74.2% gap in Suspended Solids (SS) measurements in the establishment of a SS database for the period 1951-2012. The study results show that the transport of suspended sediment discharged to the sea is about 487 t/km(2)/yr. Statistical tests of breaks highlight that rainfall decreased by 26% and that water and sediment input to the sea declined from 74% to 63% for the period of 1981-2012. The correlation analysis shows a decrease in the contribution of rainfall on sediment and water input at the outlet equal to 77.9% and 77.8%, respectively, during the period of 1980-2012, compared to the period of 1968-1980. However, the double mass method reflects the contribution of factors other than rainfall to the decrease of sediment input to the sea. These other factors mainly include large dams, which intercepted about 71% of the total volume of sediment discharged to the sea during the period of 1968-2010. In addition the contribution of large dams to the reduction of sedimentary input to the sea is more important than that of the decrease in rainfall. The management of large dams also contributes to the increase in the sediment deficit to the sea through the prioritization of interception of sediment at the expense of releases, for socio-economic purposes, 68.4% of the Cheliff River discharge is diverted for human use. This has led to an increase in the mean water bed level at bankfull downstream, where the Cheliff River gave up 51% of its width to the floodplain between 1996 and 2009. In the light of the scarcity of sediment transport data in North Africa and in many other areas, the current study provides a reference framework for other studies: providing useful information for the study of the transfer of sediment from land to sea, and the links with the socio-economic needs.

To understand the functioning of fluvial systems it is important to investigate dynamics of sediment transport and the source of sediments. In case of reconstructing past processes these studies must be accompanied by the numerical dating of sediment samples. In this respect optically stimulated luminescence is a widely used technique, by which the time of sediment deposition can be directly dated. Recently, in various fluvial environments it has been shown that certain luminescence properties of minerals, and especially that of quartz, can be applied as indicators of fluvial erosion and/or sediment provenance. These properties are residual luminescence (or residual dose) and luminescence sensitivity of quartz grains. However, the values of the parameters above are affected by various factors, the importance of which is under debate. The present study therefore aims to assess these factors along a ~560 km long reach of River Mureş (Maros) a relatively large river with a compound surface lithology on its catchment. The research focused on the sandy fraction of modern sediments, collected from the main river and from three tributaries alike. This way not only longitudinal downstream changes, but the influence of tributaries could also be studied. Based on the data, both investigated parameters show a great variation, which can be attributed to the lithological differences of subcatchments and geomorphological drivers, such as erosional activity and potential number of sedimentary cycles, and human activity. However, relationships are not entirely clear and are influenced by the maximum grain size of the samples investigated, and the recycling of previously laid deposits with different properties. Still, when performing detailed dating studies, and tracing sediments from certain parts of the catchment luminescence properties can be a useful tool in the future.

Construction of large dams is attractive because of their great benefits in flood control, hydropower generation, water resources utilization, navigation improvement, etc. However, dam construction may bring some negative impacts on sediment transport and channel dynamics adjustments. Due to the effects of recent water and soil conservation projects, sediment retention in the newly constructed large upstream reservoirs, and other factors, the sedimentation in the Three Gorges Reservoir (TGR) is quite different from the amount previously predicted in the demonstration stage. Consequently, based on the measured data, characteristics of sedimentation and the related channel deformation in the TGR were analyzed. The results imply that sediment transport tended to be reduced after the Three Gorges Project (TGP). Sedimentation slowed dramatically after 2013 and indicated obvious seasonal characteristics. Due to the rising water level in the TGR in the flood season, the yearly sediment export ratio ( E r a t i o ) was prone to decrease. The water level near the dam site should be reasonably regulated according to the flow discharge to improve the sediment delivery capacity and reduce sedimentation in the TGR, and to try to avoid situations where the flood retention time is close to 444 h. The depositional belt was discontinuous in the TGR and was mainly distributed in the broad reaches, and only slight erosion or deposition occurred in the gorge reaches. Sedimentation in the broad and gorge reaches accounted for 93.8% and 6.2% of the total sedimentation, respectively. The estuarine reach located in the fluctuating backwater area experienced alternate erosion-deposition, with a slight accumulative deposition in the curved reach. Sedimentation mainly occurred in the perennial backwater area. The insight gained in this study can be conducive to directly understanding of large reservoir sedimentation and mechanism of channel adjustment in the reservoir region in the main channel of large river.

Arctic river deltas and deltaic near-shore zones represent important land–ocean transition zones influencing sediment dynamics and nutrient fluxes from permafrost-affected terrestrial ecosystems into the coastal Arctic Ocean. To accurately model fluvial carbon and freshwater export from rapidly changing river catchments as well as assess impacts of future change on the Arctic shelf and coastal ecosystems, we need to understand the sea floor characteristics and topographic variety of the coastal zones. To date, digital bathymetrical data from the poorly accessible, shallow, and large areas of the eastern Siberian Arctic shelves are sparse. We have digitized bathymetrical information for nearly 75 000 locations from large-scale (1:25 000–1:500 000) current and historical nautical maps of the Lena Delta and the Kolyma Gulf region in northeastern Siberia. We present the first detailed and seamless digital models of coastal zone bathymetry for both delta and gulf regions in 50 and 200 m spatial resolution. We validated the resulting bathymetry layers using a combination of our own water depth measurements and a collection of available depth measurements, which showed a strong correlation (r>0.9). Our bathymetrical models will serve as an input for a high-resolution coupled hydrodynamic–ecosystem model to better quantify fluvial and coastal carbon fluxes to the Arctic Ocean, but they may be useful for a range of other studies related to Arctic delta and near-shore dynamics such as modeling of submarine permafrost, near-shore sea ice, or shelf sediment transport. The new digital high-resolution bathymetry products are available on the PANGAEA data set repository for the Lena Delta (https://doi.org/10.1594/PANGAEA.934045; Fuchs et al., 2021a) and Kolyma Gulf region (https://doi.org/10.1594/PANGAEA.934049; Fuchs et al., 2021b), respectively. Likewise, the depth validation data are available on PANGAEA as well (https://doi.org/10.1594/PANGAEA.933187; Fuchs et al., 2021c).

Net sediment transport is predominantly seaward in fluvial-dominated estuaries worldwide. However, a distributary branch in the Changjiang Estuary, the North Branch, undergoes net landward sediment transport, which leads to severe channel aggradation. Its controlling mechanism and the role of human activities remain insufficiently understood, although such knowledge is necessary for better management and restoration opportunities. In this study we revisit the centennial hydro-morphodynamic evolution of the North Branch based on historical maps, field data, and satellite images and provide a synthesis of the regime change from ebb to flood dominance. The North Branch was once a major river and ebb-dominant distributary channel. Within which alternative meandering channels and sand bars developed. Deposition of river-borne sediment leads to infilling of the branch, while tidal flat embankment reduces the bankfull width and modifies the channel configuration, resulting in a profound decline in the sub-tidal flow partition rate. The North Branch then becomes tide-dominant with an occurrence of tidal bores and elongated sand ridges. Once tidal dominance is established, extensive tidal flat reclamation enhances the funnel-shaped planform, amplifying the incoming tides and initiating a positive feedback process that links tidal flat loss, sediment import, and channel aggradation. Overall, the shift in branch dominance is a combined result of a natural southeastward realignment of the deltaic distributary channels and extensive reclamation. One management option to mitigate channel aggradation is to stop the aggressive reclamation and allow tidal flats to build up, which might reduce the sediment import and eventually lead to a morphodynamic equilibrium in the longer term. Understanding the impact of tidal flat reclamation is informative for the management of similar tidal systems under strong human interference.

The Greater Barents Sea Basin (GBSB) in Arctic Russia and Norway is an intracratonic basin that accommodated an enormous amount of sediment during the Triassic. These deposits are up to 4.5 km thick over an area 2,500,000 km2, and consist of marine mudstones and mudstone-rich fluvio-deltaic topsets with sandstone-dominated fluvial channels. The basin is well-studied and data-rich, but regional correlation between different parts is lacking. Provenance data from adjacent Arctic basins have been interpreted to imply sediment transport from the Ural orogen across the GBSB, but these are disputed because of great transport distances, poorly constrained sediment-transport directions and unknown timing of bypass. We integrated data from 3,238 seismic lines, 257 wells and palynostratigraphy, as well as published outcrop data, to create the first unified stratigraphic framework for the Triassic deposits across the entire GBSB. Results show that (1) sediment was transported northwest by one linked sedimentary system stretching across the entire basin; (2) sediment was derived from a source in the east comprising the Urals and West Siberia; (3) the main stratigraphic boundaries are major flooding surfaces which can be traced throughout the basin; and (4) significant amounts of sediment overspilled from the Barents Sea into adjacent sedimentary basins, starting with the Lomonosov Ridge from the Early Triassic, and into basins to the northwest (e.g. Sverdrup, Chukotka) during the late Carnian. These results provide a better understanding of geodynamics and provenance data in the Arctic, to improve the prediction of reservoirs in the area, and indicate a protracted uplift-history of the northernmost Urals that started in the Carnian ~237 Ma. Furthermore, it shows how large intracratonic basins interact with uplands and subside over tens of millions of years. publishedVersion

A well-established 3D phase-averaged beach morphodynamic model was applied to investigate the morphodynamics of a typical artificial beach, and a series of discussions were made on the surfzone hydro-sedimentological processes under calm and storm events. Model results revealed that the nearshore wave-induced current presents a significant 3D structure under stormy waves, where the undertow and longshore currents exist simultaneously, forming a spirallike circulation system in the surfzone. Continuous longshore sediment transport would shorten the sediment supply in the cross-shore direction, subsequently suppress the formation of sandbars, showing that a typical recovery profile under calm waves does not necessarily develop, but with a competing process of onshore drift, undertow and longshore currents. Sediment transport rate during storms reaches several hundreds of times as those under calm waves, and two storm events contribute approximately 60% to the beach erosion. Sediment transport pattern under calm waves is mainly bed load, but as the fine sands underneath begin to expose, the contribution of suspended load becomes significant.

A preliminary field-based investigation was undertaken in a small (< 10 km2) river valley located in the mountainous Jura region of northwest Switzerland. The aims of the work were to assess sediment generation and annual sediment transport rates by tree throw on forested hillslopes, and to document surface hydrology characteristics on four fresh soil mounds associated with recent tree throws over a 24-day monitoring period. For the soil mounds, average sediment recovery ranged from 7.7–28.2 g (dry weight), equivalent to a suspended sediment concentration of 145.2–327.8 g L−1, and runoff coefficients ranged from 1.0%–4.2%. Based on a soil bulk density value of 1,044 kg m−3, upslope runoff generation areas were denuded by an average 0.14 mm by the end of the 24-day monitoring period, representing an erosion rate equivalent to 2.1 mm yr−1. A ca. 50 cm high soil mound could therefore feasibly persist for around 200–250 years. For tree throw work, the dimensions of 215 individual tree throws were measured and their locations mapped in 12 separate locations along the river valley representing a cumulative area equivalent to 5.3 ha (av. density, 43 per ha). Tree throws generated a total of 20.1 m3 of fine-sediment (< 2 mm diameter), or the equivalent of 3.8 × 10−4 m3 m−2. The process of tree throw was originally attributed to two extreme weather events that occurred in west and central Europe in late December 1999. Taking the 18-year period since both storms, this represents an annual sediment transport rate of 2.7 × 10−5 m3 m−1 yr−1. Exploring the relationship with wind on fall direction, 65.5% of tree throws (143) generally fell in a downslope direction irrespective of hillslope aspect on which they were located. This infers that individual storms may not have been responsible for the majority of tree throws, but instead, could be associated with root failure. Given the high density of tree throws and their relative maturity (average age 41 years), we hypothesise that once trees attain a certain age in this river valley, their physiognomy (i.e. height, mass and centre of gravity) compromises their ability to remain securely anchored. We tentatively attribute this possibility to the presence of bedrock close to the surface, and to the shallow soil profile overlaying steep hillslopes.

As misturas solidas e liquidas no curso fluvial sao intensificadas em areas de confluencia de rios condicionadas principalmente pela abertura angular da juncao. O conhecimento da dinâmica hidrossedimentologica em juncoes de leito rochoso com diferentes aberturas angulares e fundamental para entendimento do ajustamento morfologico nas confluencias e subsidiar acoes de preservacao e conservacao dos ecossistemas fluviais. Nesse sentido, o presente trabalho apresenta os resultados de um estudo hidrogeomorfologico sobre confluencia fluvial com ângulo de juncao obtuso (>100o), em rio de planalto com leito rochoso, na Formacao Serra Geral. A pesquisa avaliou segmento fluvial a montante e jusante do rio das Pedras e no tributario rio das Pombas, em Guarapuava, Parana, por meio de observacoes e mensuracoes das caracteristicas morfologicas e hidraulicas largura, profundidade do talvegue, declividade do leito e vazao em margens plenas. O ajustamento morfologico em confluencias obtusas e peculiar, uma vez que o ângulo de juncao fluvial condiciona uma dinâmica especifica de fluxo, erosao, transporte e deposicao de sedimentos, resultado principalmente de sua associacao com a natureza geologica do leito fluvial e os tipos de uso e manejo da terra a montante da confluencia. Hydrogeomorphology of an obtuse fluvial confluence, Guarapuava, Parana A B S T R A C T Solid and liquid mixtures in river courses intensify in areas of river confluence, conditioned mainly by the angular opening of the junction. Knowledge of hydrosedimentological dynamics in bedrock junctions with different angular openings is essential for understanding morphological adjustment at confluences and for supporting actions for the preservation and conservation of river ecosystems. For this reason, this article presents the results of a hydrogeomorphologic study on a river confluence with an obtuse junction angle (>100o), in a plateau bedrock river, in the Serra Geral Formation. The research evaluated a fluvial segment upstream and downstream of the Pedras River and in the Pombas River tributary, in Guarapuava, Parana, through observations and measurements of morphological and hydraulic characteristics, width, talweg depth, bed declivity and bankfull flow. Morphological adjustment in obtuse confluences is peculiar in that the fluvial junction angle conditions specific flow, erosion, sediment transport and deposition dynamics, mainly resulting from its association with the geological nature of the river bed and types of land use and management upstream of the confluence. Keywords: Fluvial channel stability, bedrock, fluvial morphology.

In the year 2013, the Northwestern Himalaya witnessed an extreme hydrological event that severely affected the upper Ganga Basin. The unexpected high sediment mobilisation in the basin affected the human population, infrastructure, and ecology in several reaches of the Ganga river and its tributaries. In an exceedingly affected reach, the Kedarnath valley, a considerable sediment volume (∼26243 × 104 m3) was mobilised during the 2013 extreme hydrological event. In the Srinagar valley, up to 50 × 104 m3 of legacy sediment was washed away during the same event. This sediment mobilisation generated sediment pulses in the affected region, which is assessed through remote sensing, field observations and existing literature, in the Kedarnath and Srinagar valleys. Results show that the evolution of translative, dispersive, and their combined sediment pulse pattern in both selected reaches of the upper Ganga Basin. The mountainous region of the upper Ganga basin has very few monitoring stations observing sediment movement, and data from such stations are mostly unavailable due to which our understanding of the sediment movement in the Himalaya remains very poor. Therefore, it is suggested that there is a need for detailed studies of the sediment transport mechanism in the Himalayan river basins especially during such extreme hydrological events when large volume of sediment is mobilised.

Tree uprooting is an important process which leads to many geomorphic consequences. Some of the most important are the transport of sediment and mixing of soil. The aim of this article is to make a detailed examination of the magnitude of sediment transport caused by an extreme windthrow event in three severely affected catchments. Also, a comparison is made of the windthrow event with a mass movement event in the aspect of the magnitude of sediment transport and soil mixing. The study was conducted in three second- to third-order catchments in the Tatra Mountains, where a strong foehn wind event caused extensive windthrow in 2013, and a high-magnitude rainfall event triggered mass movements in 2007. The volume of sediment uplifted by the uprooting event was calculated based on the mapping of root plates using high-resolution (0.04 m) aerial images and measurements of root plate volumes conducted in the field. The volume of sediment transported by shallow landslides was determined based on a Digital Elevation Model (DEM, 1-m resolution). Windthrows affected 34%, 76%, and 94% of the area of the investigated catchments. Most of the trees had fallen downslope. The direction of treefall was influenced by the slope aspect and steepness. Root plates and pits covered 1.3%, 4.8%, and 5.4% of the area of the catchments. Sediment flux generated by the uprooting event, calculated for the entire area of each investigated catchment ranged from 8.1 × 10−4 to 9.9 × 10−3 m3 m−1 event−1. This was notably lower than the sediment flux generated by the mass movement event (also calculated for the entire area of each catchment), which was 1.8−6.1 × 10−2 m3 m−1 event−1. By contrast, uprooting affected a much larger area than the mass movement event, which underlines its significant role in the mixing of soil.

Kelud Volcano is one of the active volcanoes and located in East Java. After the eruption, Kelud Volcano left a number of volcanic materials from the rock, sand and the ash on residential land, plantations and the surrounding area. The main problem is the eruption of Kelud Volcanoes has the potential to experience an increase in the frequency of eruptions and there has been no development of a regional reconstruction model for secondary impacts due to eruptions in the field of water resources infrastructure. Based on these problems, a test of the Sabo and modular hydraulic physical models will be planned. This study discusses the identification of the location and volume of sediments that have the potential to become Kali Putih lava flows from Kelud Volcanoes. The Takahashi analysis method is used to analyze the estimated excess volume of the target sediment which must be controlled by sabo technology. Identification of sediment transport zones is obtained from the classification of slope on existing buildings obtained from satellite imagery. The results of the analysis are as follows: 1.) Sediment transport areas in the Putih Watershed have an area of 863 km2. 2.) The total volume of Kali Putih sediment that has the potential to become cold lava after the eruption is 4,139,414.23 m3. 3.) Sabo and modular hydraulic physical model testing is required. 4) A model of regional reconstruction is needed for secondary impacts due to eruptions in the water resources field. 5) New sabo plan planning is needed

The shoreline of northern Colombia is located in the tropical zone along the south coast of Caribbean Sea. Its coastal processes are strongly influenced by the northeast trade wind, which results in the dominating northeasterly approaching wave occurring over 95% of the time. This drives a persistent southwestward longshore sand transport. The state of the beach along the generally northeast-southwest trending northern Colombia coast is strongly influenced by this constant unidirectional longshore sediment transport. At locations where this westward longshore sand transport is interrupted, naturally or anthropogenically, beach accretion occurs along the updrift shoreline coupled with erosion at the downdrift side. Natural interruption of longshore transport can be caused by tidal inlets, protruding headland, shoreline orientation change, and nearshore bathymetry variations. Anthropogenic interruption of the longshore transport along the northern Colombia coast is mainly caused by the construction of groins, as well as harbors at some locations. Numerous groins were constructed due to their local success in creating beach accretion at the drift side. However, severe beach erosion occurs along the downdrift shoreline. Shoreline protection along the northern Colombia coast, and coasts in the tropical area in general, should carefully consider the persistent unidirectional longshore sand transport and should not be misguided by the local updrift accumulation as being a successful project.

Sediment material transported by the Indus River has two origins, the catchment and its wetted perimeter, whereas the amount of materials transported from the river itself depends on variables such as the flow type and the sediment load. The annual sediment load transported in the Indus River ranged from 270 to 600 million tons (MT) before the building of dams and barrages. The average sediment load is 0.715 MT/day or approximately 260 MT/ year after the construction of hydraulic structures. The average particle size, D50, of the bedload is approximately 0.125mm at the Sukkur barrage [1]. In this study, research was conducted to evaluate sediment problems in the Nara Canal, take-off from the left pocket of the Sukkur Barrage on the Indus River. The collected data from the left pocket, the bed, and suspended material in upper Nara and its off-taking canals were analyzed to assess sediment transport dynamics of upper Nara canal at various locations and its off-taking canals. The bed material at RD 553+600 shows a minimum size of 0.07 and a maximum of 0.7mm with 54% fine-sand mixed with 46% medium-sand in 2003. Fine-sand increased to an average of 75% while medium sand diminished to 25% at RD 553+600 in Nara canal and at RD 595+000 in Jamrao complex in 2013. The suspended load with low and high flows during 2012 exhibits that in all the cases the sand proportion was increasing in the Upper Nara canal system flowing to the Jamrao complex. The sediment concentration value indicates that there is the deposition of sand at the upper Nara canal and the Jamrao complex causing a discharge reduction in the Nara Canal system.

The study presents an analysis of the sediment thickness compared with bathymetric and geophysical settings in the Bay of Bengal and Andaman Sea, Indian Ocean. It uses a combination of the high-resolution data: topographic GEBCO, satellite and marine gravity anomalies, EGM2008 geoid and GlobSed to visualize the correlation between relief, gravity and trends in continent-ocean sediment transport. The results include thematic maps and 3D model showing increased sediment thickness in the Bengal Fan (8,0 to 8,2 km) in NE direction with maximum in Ganges Fan (16,2 km), and southward decrease in the Andaman Sea from Irrawaddy river mouth (6-7 km) to the Strait of Malacca (1-2 km). All maps and 3D model have been plotted by Generic Mapping Tools (GMT) cartographic scripting toolset version 6.0.0.

Interactions among different landforms and varied complicated physical processes cause sediment transport in coastal regions being the interest of ocean management planning studies. In coastal zones, the derivation of the bedload sediment transport rate and the flow velocity distribution is done by entropy theory which assumes the modified spatiotemporal disorder power index (MSTDPI) and the time-averaged flow velocity (as a random variable). Studying the deposition trend of bedload sediment transport rate for the sand particle (BLSTRS) and estimating the coastal erosion rate as a case study, the Makran coast is selected. To analyze the spatiotemporal patterns, the disorder power index (entropy-power) method is applied in this study where the monthly data of six Makran coastal sections from January 1970 to December 2015 are used. The studied data are mainly focused on the correlation of the flow rate of the sediment from the Makran River, and the spatiotemporal patterns of BLSTRS. Despite their meaningful spatiotemporal variability, it is not very easy to explain how the abovementioned variables perform together; the entropy-power index allows a better understanding of the combined performance of such parameters as the flow velocity and sediment transport by showing clearer signals for the assessment of coastal engineering issues at very large (coastal) scales.

Climate change in the Antarctic over the past 50+ years has caused contraction of ice and snow cover, longer melt seasons and intensified glacier melting. These changes affect erosion and sediment redistribution processes that are vital to our understanding of terrestrial and freshwater ecosystems and sediment input to oceans. This 79 day study of the Orwell Glacier meltwater stream on Signy Island (5 December 2019–21 February 2020) used 5 min recordings of turbidity, stream discharge (Q) and air temperature (AT), supplemented by 454 water samples from which suspended sediment concentration (SSC) was gravimetrically determined, to calculate daily suspended sediment loads (SSLs). Qmean was 47.8 ± 3.5 l s-1, SSCmean was 71.0 ± 15.9 mg l-1 and daily SSLmean was 75 ± 8 kg day-1 with a suspended sediment yield of 43.6 t km-2 yr-1. A multiple regression model predicted SSLs reliably (multiple r = 0.95, r2 = 0.91, n = 79) and, when run with ATmean + 1°C (expected on Signy Island by 2060) and ATmean + 2°C (expected by 2100) scenarios, the model predicted 7% and 13% increases in SSLs, respectively. The SSLs estimated in this study are low when compared with others from around the world.

Submarine channels are the main conduits and intermediate stores for sediment transport into the deep sea, including organics, pollutants, and microplastics. Key drivers of morphological change in channels are upstream-migrating knickpoints whose initiation has typically been linked to episodic processes such as avulsion, bend cutoff, and tectonics. The initiation of knickpoints in submarine channels has never been described, and questions remain about their evolution. Sedimentary and flow processes enabling the maintenance of such features in non-lithified substrates are also poorly documented. Repeated high-resolution multibeam bathymetry between 2012 and 2018 in the Capbreton submarine canyon (southeastern Bay of Biscay, offshore France) demonstrates that knickpoints can initiate autogenically at meander bends over annual to multi-annual time scales. Partial channel clogging at tight bends is shown to predate the development of new knickpoints. We describe this initiation process and show a detailed morphological evolution of knickpoints over time. The gradients of knickpoint headwalls are sustained and can grow over time as they migrate through headward erosion. This morphology, associated plunge pools, and/or development of enhanced downstream erosion are linked herein to the formation and maintenance of hydraulic jumps. These insights of autogenically driven, temporally high-frequency knickpoints reveal that cut-and-fill cycles with depths of multiple meters can be the norm in submarine systems.

An inverse reduced-gravity model is used to simulate the deep South China Sea (SCS) circulation. A set of experiments are conducted using this model to study the influence of the Luzon overflow through the two inlets on the deep circulation in the northern SCS. Model results suggest that the relative contribution of these inlets largely depends on the magnitude of the input transport of the overflow, but the northern inlet is more efficient than the southern inlet in driving the deep circulation in the northern SCS. When all of the Luzon overflow occurs through the northern inlet the deep circulation in the northern SCS is enhanced. Conversely, when all of the Luzon overflow occurs through the southern inlet the circulation in the northern SCS is weakened. A Lagrangian trajectory model is also developed and applied to these cases. The Lagrangian results indicate that the location of the Luzon overflow likely has impacts upon the sediment transport into the northern SCS.

One of the most common types of methods to design stable dimensions of a channel is empirical regime relationships to which morphological parameters of stable rivers are related. These relationships could be considered to be more realistic for the design purposes as they consider sediment transport in the rivers. Bed material gradation curve of rivers and river bed armouring development are key points to identify river characteristics and controlling factors in sediment transporting and eroding processes of gravel bed rivers, respectively. In this study, field work was initially carried out on several gravel bed rivers in Khuzestan and Chaharmahal provinces. 24 hydrometeorological stations in 17 river reaches were sampled to characterize bed material gradation curve. With regards to bed structure of gravel bed rivers, samplings were made by surface and volumetric methods. Thereafter, sediment samples were differentiated in three categories of surface, armour and sub-armour layers. The collected field data were originally applied to derive regime relationships by using multivariate regression analysis. The effect of bed structure was then studied in these relationships for the better understanding of that in the regime relationships. The regime relationships yield most appropriate estimated value for four variables equations in comparison with less variables equations.

Kali Lamong River with a trapezoidal channel shape has a bottom width of about 30 m, a top width of 40 m and a depth of 3.5 m. In one of the river segments, the basis is in the form of a fixed bed and it is assumed that there is no sediment transport in this section. On the downstream side after the fixed bed section, the river segment is a mobile bed with river bed material that has an average grain diameter of 1.5 mm, a relative mass density of 2.6, and porosity of 0.3. Flowrate with Q50 is 1000.00 m3/sec with a maximum flow speed of 15 m/sec. Riverbed degradation will occur initially at the upstream point in the fixed and mobile beds. Depth of riverbed degradation calculated by the Parabolic model of 80.00 cm / year based on the solution of the equation.

Wetlands as unique, rich, and fertile ecosystems are among the most vital environments in the world. Quaternary sediments of wetlands are the main components of our environment and an essential source of clastic, organic, and chemical substances that can be caused by natural processes and erosion or created by human intervention. This article broadly deals with the grain size and geochemistry of Quaternary sediments in Saghalak-Sar as one of the wetlands in Guilan province in the north of Iran. The 74 surface and subsurface samples (from 10 core) of the sediments were graded, and sedimentationparameters of the particles (Sorting, Skewness, and Kurtosis) were determined. Also, the frequency of elements oxides and subelements oxides were determined by ICP and XRF, respectively. The sediments were classified into eight sedimentary types including Slightly Gravelly Muddy Sand, Slightly Ggravelly Sandy Mud, Sandy Mud, Gravelly Muddy Sand, Gravelly Mud, Slightly Gravelly Sandy Mud, and Gravelly Sand. On the east of the wetland (core 1 to 8), the percentage of sand is less the mud, and on the south and west of the wetland (core 9 to13), the sand is higher, indicating more energy in the south and west. Sorting of sediments is poorly to moderately sorted and the Skewness in most samples is coarse Skewed. The number of sediment content is 2 to 3, but the sand content is the majority of the samples. According to these data, the sediments are transmitted to sedimentary basins by the river or muddy streams. The comparison of the oxide elements of the above samples with upper continental crust (UCC) indicated the mean value of SiO2 (63.1%) in the wetland sediments is slightly less than the average of this oxide in the upper continental crust (66.6%), the average of CaO (0.8) less than the average of upper continental crust (except the 12 core and surface sediments sw1) and the amount of Na2O (0.8) and K2O (2.1) are less than the upper continental that indicates the destruction of plagioclases as a result of chemical weathering in the source or during the transport process. The comparison of MgO, Fe2O3, TiO2 sediment samples at different depths and upper continental crust shows that the average of MgO (1.2) is lower than the upper continental crust ten but Fe2O3 ( 7.2), TiO2 (1.2) arehigher than the upper continental crust. The decrease of CaO, Na2O, and SiO2 and the increase of Al2O3 and Fe2O3 indicate an increase in weathering during the transport process and the production of clay and aluminum oxide and iron oxide due to the decomposition of complex clays and non-clay minerals. Matching sediment samples on the two-axial diagrams of the main elements oxides, i.e., (Fe2O3+ MgO) versus Al2O3/ SiO2 and TiO2 and log (K2O / Na2O) versus SiO2, as well as the triangular diagrams of the sub-elements Zr, Th, La, and Sc, indicate that the wetland sediments are more inclined towards the range of oceanic arc islands and continental arcs, and are composed of subduction rocks.

Erosional landscapes transport sediment downstream, host natural hazards and are geologically active. While perturbations in external forcing, particularly climate and tectonics, sculpt erosional landscapes, similar landforms can be created by internal dynamics, that is, feedbacks between topography, erosion and sediment transport that occur independent of external perturbations. Internal system responses, termed autogenic dynamics, can remain active as landscapes adjust to perturbations in forcing, allowing for complex responses to external perturbations that potentially obscure links between external forcing, topographic form and sedimentary archives. Autogenic dynamics are being increasingly recognized in depositional systems, yet understanding of autogenic dynamics in erosional landscapes is nascent. In this Review, we discuss the mechanisms that contribute to internal dynamics in erosional landscapes. We use examples of autogenic terrace formation, knickpoint formation and river-basin reorganization to show how autogenic dynamics that occur over spatial scales of metres and temporal scales of hours can influence the evolution of mountain ranges over Myr periods. Unravelling the mechanics of autogenic processes allows the interplay of internal dynamics and external forcing to be explored and provides a framework to assess the influence of erosional processes in the geologic record. The morphology of erosional landscapes is often considered to be set by climate and/or tectonics; however, similar topographic features can arise through internal processes and feedbacks. This Review considers how the internal and external processes drive landscapes evolution, and how such processes can be differentiated in topographic and stratigraphic records.

The aim of this paper is to evaluate a newly developed one dimensional unsteady flow, sediment transport and bed evolution model for a looped river network through a long term simulation of a real-life scenario. The model was assessed by verifying it for the Danube, Tisa, and Sava rivers in Serbia for a five year time interval. The total length of the modeled domain was 741.94 km from which 486.48 km is the length of the modeled Danube River reach, 132.50 km the modeled section of the Sava and 122.96 km the length of the modeled Tisa River reach. The simulated domain included smaller tributaries such as the Kolubara, Mlava, Nera, Pek, Porecka, Tamis, and Great Morava rivers. Due to the size of the domain that was included in the model, the work also includes extensive research regarding the available measurements, issues with measurement errors, and suggestions on overcoming incomplete measurements by developing different types of correlations. The attained results were analyzed by comparing the simulation results with measured water levels, discharges, and suspended sediment concentrations. The implemented evaluation of the results confirmed the developed model's reliability.

International audience; Wind waves breaking at an angle with the shoreline force the drifting of littoral sediments, which is known for contributing to the formation and growth of barrier spits. Intriguingly, increased rates of longshore wave power have also been associated with the erosion of some barrier spits on the updrift margin of tidal inlets. Therefore, a numerical experiment was designed and is presented here, which investigates the possible links between the longshore wave power and the shortening of these elongated coastal barriers. Based on a process-based model, the experiment provides new insights into the forces at play in the redistribution of sediments between a sandspit and its adjacent inlet, respectively the Cap Ferret and the Bay of Arcachon's tidal inlet, in SW France. More particularly, model scenarios were defined that show how combined waves and tide create gradients of residual sediment transport responsible for a sediment deficit at the spit – inlet boundary. The deficit was also found to deepen with increasing longshore wave energy, as if the transfer of sediment from the spit to inlet shoals was accelerated. This physically explains the previously observed retreat of the spit's distal end during periods dominated by the positive phase of North Atlantic Oscillation (NAO) in winter. Indeed, according to model results, higher and/or more oblique waves associated with the positive phase of the NAO are expected to increase the transfer and storage of the drifting sediments to and by the inlet shoals, and this at the expense of the spit. While these conclusions remain valid, we noticed that the sensitivity of model results to the bottom friction enhanced the importance of accurately representing the spatio-temporal distribution of bed roughness when investigating the morphodynamic interactions between real-world tidal inlets and their margins.

The vertical density gradients of salinity and suspended sediment concentration (SSC) cause stratification in estuaries, which play a vital role in the turbulence structure, water mixing, and sediment transport. To investigate the effect of stratification, especially SSC-induced stratification, on maintaining the estuarine turbidity maximum (ETM), we conducted in situ measurements on sediment dynamics at the upper and central ETM sites in the South Passage of Changjiang Estuary in July 2018. The gradient Richardson number was estimated as a proxy for the stratification that is attributable to salinity or/and SSC. We found that salinity-induced stratification was observed mainly on the surface and in the middle layers, whereas SSC-induced stratification occurred mainly in the near-bottom layers. Furthermore, at the central ETM, the baroclinic effect was enhanced during the neap tide when the salinity-induced stratification was stronger than that during the spring tide. In the early phase of floods with minimum velocity during the neap tide, salinity-induced stratification suppressed the turbulence and vertical diffusion of sediments. Moreover, the flocculation enhanced the settling process within the water column. Consequently, high concentrations of fine-grained sediments formed near the bottom and promoted SSC-induced stratification, thereby leading to the continuous accumulation and trapping of sediments. In conclusion, the interactions among the “salinity- and SSC-induced stratification” processes served as crucial constraints of the temporal and spatial variations of the ETM in the Changjiang Estuary.

Trough mouth fans comprise the largest sediment deposits along glaciated margins, and record Pleistocene climate changes on a multi-decadal time scale. Here we present a model for the formation of the North Sea Fan derived from detailed horizon and attribute interpretations of high-resolution processed 3D seismic reflection data. The interpretation shows that stacked channel-levee systems form up to 400 m thick sedimentary sequences. The channels are elongated and can be traced from the shelf edge towards the deep basin for distances of >150 km, and document long-distance sediment transport in completely disintegrated water-rich turbidite flows. Downslope sediment transport was a continuous process during shelf-edge glaciations, reaching accumulation rates of 100 m/kyr. Our data highlight that exceptionally large volumes of meltwater may discharge to the slopes of trough mouth fans and trigger erosive turbidite flows. We conclude that freshwater supply is likely an underestimated factor for sedimentary processes during glacial cycles., Trough mouth fans are created via repeated glacigenic sediment transport from ice sheets. Here the authors use 3D seismic reflection data to present a formation model for the North Sea Fan and find that exceptionally large volumes of meltwater may mean that freshwater supply is underestimated during glacial cycles.

A model is developed to simulate the morphodynamics of a barred shore profile on the scale of a storm cycle, comprising the phases of high and low wave activity. In the CROSS-PB model, the main mechanisms governing sediment transport in wave shoaling and surf zones are taken into consideration, in particular, skewness and asymmetry of the wave orbital velocities, undertow, and infragravity oscillations associated with wave groups. By comparing calculations with observed data, it is concluded that the model correctly reproduces seaward displacement of bars during a storm and shoreward under moderate or weak wave conditions. The first process is shown to be provided by balance of transport mechanisms when the peak offshore transport is located at the front slope of bar. The second process is conditioned by dominant shoreward transport and its sharp decay over the bar crest. Testing of the model yields estimates for the calibration coefficients, and it is concluded that shoreward sediment flux is mainly controlled by wave asymmetry.

International audience; The purpose of this study is to better understand the system of Quaternary loess-palaeosol sequences (LPS) of the Matmata region in southern Tunisia. Results from a combination of predominantly classical methods (grain size and mineral analysis, CaCO3- content estimation, environmental magnetism) indicate strong soil formation phases during which the conditions of sedimentation changed drastically. The heavy mineral analysis underlines northwest, west and southwest provenances of the loessic material. Furthermore, we discuss the process of soil formation in LPS and explain why these soils are very sandy in comparison to the loess units. During phases of soil formation, the northwestern sediment transport path was blocked while sandy material was blown dominantly from the southwestern Grand Erg. Therefore, we present a conceptual model including a provenance analysis of the loessic material that support and improve earlier results of Coudé-Gaussen and collaborators.; Dans cette étude, nous présentons un modèle conceptuel pour une meilleure compréhension du système de séquences de loess paléosol (LPS) dans la région de Matmata située dans le sud de la Tunisie. Les résultats d'une combinaison de méthodes principalement classiques (analyse granulométrique, analyse minéralogique, détermination de la teneur en CaCO3, magnétisme environnemental) indiquent des phases de formation importante de sols au cours desquelles les conditions de sédimentation ont fondamentalement changé. L'analyse des minéraux lourds met en évidence une origine nord-ouest, ouest et sud-ouest du matériel loessique. En outre, nous discutons la nature de la formation des sols et expliquons pourquoi ces sols sont si sableux par rapport aux unités de loess. Pendant les phases de formation des sols, le trajet des sédiments en provenance du nord-ouest a été bloqué alors que les matériaux sableux pouvaient encore être soufflés à partir du Grand Erg au sud-ouest. Notre modèle conceptuel de la provenance du lœss à Matmata soutient et précise les conclusions de Coudé-Gaussen et collaborateurs.

Beach nourishment is a common strategy for erosion mitigation that also increases coastal resilience to storm impacts, provides habitat, and supports the economy. Regulations often require that placed sediment closely match the native grain size distribution and composition, however characteristics can vary based on the borrow site. Certain sediment properties will also influence beach slope and other critical beach functions. This study evaluates the 3-dimensional sediment properties and beach morphology of nourished and non-nourished barrier island beaches in northern Palm Beach County, Florida, USA. Surveyed beach profiles were compared with predicted slope based on median grain size. The inlet-adjacent beach managed with annual placement of beneficial use of dredged materials consisted of poorly sorted coarse sand and the steepest measured slope. Sediment was progressively finer and better sorted downdrift with decreasing foreshore slopes. Although sediment near the shoreline is typically the coarsest, clasts were finer than the mid-beach location suggesting that the sampling period coincided with beach recovery and onshore sediment transport of finer material. Sediment at the surface differed from sediment at depth, likely due to the frequent introduction of sediment from various borrow areas compared to the dominance of weathered coquina at depth. The non-carbonate, siliciclastic fraction was primary quartz with few other minerals. The estimated beach slope at the location with the coarsest sediment matched the measured slope. A lower beach slope was predicted for the other locations with finer grain sizes at the shoreline that was attributed to slightly steeper slopes associated with beach accretion. Therefore, complicated spatio-temporal morphodynamics of beaches should be considered when using median grain size from only one sampling event.