Search

Tidal flats, crucial for biodiversity and ecosystem services, are facing significant alterations due to human activities such as reclamation. In South Korea, over 65% of tidal flats have been reclaimed since the 1970s, resulting in morphological changes and altered sediment transport dynamics. This study investigates sediment transport processes in the artificial Aam tidal channel, created as part of the megacity development project in Incheon, Korea. Using data from Acoustic Doppler Current Profiler and Vector instruments deployed in 2019 and 2021, we analyzed tidal asymmetry, current velocities, shear stress, and suspended sediment concentration. Our results reveal a pronounced tidal asymmetry influencing sediment transport, with ebb-dominant currents near the channel entrance and flood-dominant currents in the interior. We observed significant sediment deposition in the landward section of the channel, driven by tidal mixing asymmetry and rainfall events. These findings highlight the complex interactions between artificial structures and natural sediment dynamics, informing future coastal development and management strategies. [ABSTRACT FROM AUTHOR]

Sediment fingerprinting technology is widely used to differentiate sediment sources. However, despite its long-recognized benefits, there it has been seldom applied to assess the variability of sediment sources during storm events. In this study, sediment fingerprinting is used for four storm events to determine the dynamic changes in sediment sources throughout them in the black soil region in Northeast China. Three potential sediment sources—cultivated land, unpaved roads, and gullies—were effectively differentiated using four geochemical tracers (As, Be, Cs, and Cu), with an accuracy of 100%. The relative sediment contribution from each source was determined using linear and Bayesian mixing models. The mean absolute fit (MAF) values of the linear mixing model (MAFmean = 0.976–0.949) were higher than those of the Bayesian mixing model (MAFmean = 0.921–0.992), indicating that the first performed better. Cultivated land was the primary source of the sediment load, accounting for 59.03% of it (load-weighted mean = 68.29%), followed by the gullies (37.15%, load-weighted mean = 28.09%), and unpaved roads (3.90%, load-weighted mean = 3.69%) for the four storm events. In addition, a high variability in sediment source contribution was observed during the storm events. Cultivated land was the dominant sediment source during storm events with higher sediment concentrations (logarithmic function, r2 = 0.878, p

In-situ mooring systems with acoustic Doppler current profilers were installed in the western (TM01) and eastern (TM02) parts of Yeosu Bay from September 3 to October 2, 2021, to understand the controlling mechanisms of suspended sediment transport. In the bay, freshwater from the Seomjin River freely exchanges with seawater from the open sea. Over the mooring period, current flows were mainly dominated by ebb tides. Power spectral density analysis of the suspended sediment concentration (SSC) exhibited a quarter-diurnal (6.21 h) frequency at TM01 and a semi-diurnal (12.42 h) frequency at TM02. The results suggested that SSC variations in the western part were driven primarily by local sediment resuspension, while they were influenced predominantly by horizontal advection in the eastern part. Differences in SSC variation at the two stations could be due to the physical properties of the bed sediments (TM01: sandy mud containing shell fragments, TM02: mud). Such current flows and SSC variations over the tidal cycles caused an imbalance of sediment transport. At TM01, the sediment fluxes were dominantly seaward due to tidal pumping (88% of the total) and the discharge of suspended sediments in the surface layer by residual circulation. At TM02, landward sediment fluxes were driven primarily by the residual current (73% of the total). Although the suspended sediment fluxes tended to be compensated and balanced mutually by circulation over the entire period, the suspended sediment fluxes at TM02 were approximately twice higher than those at TM01. This was caused by the difference in SSC asymmetry between flood and ebb at the two stations. The mechanisms controlling the transport of suspended sediment could vary spatially, and the relative contribution of tidal pumping and residual circulation could result in an imbalance of sediment transport. [ABSTRACT FROM AUTHOR]

Significane The analysis of source-to-sink system is a comprehensive study of tectonic geology, sedimentology, and sequence stratigraphy. Because of its integral, dynamic, and semiquantitative-quantitative characteristics, it has attracted widespread attention. Progress This review first introduces the key issues of the deep-time source-to-sink systems (pre-Quaternary systems), which include the quantitative characterization of sediment mass balance and the control of the transport process on the sediment. Due to the lack of stratigraphic records and the difficulty in obtaining parameters, the research is still challenging.Second, it reviews the quantitation methods of deep-time source-to-sink systems that can be classified into three categories, namely, geochronology, uniformitarianism, and sedimentology. By obtaining information such as geomorphological parameters, hydraulic parameters, erosion rates, and sediment flux, various methods establish the quantitative relationships between "sources" and "sinks" and then rebuild the sedimentary basin infilling history. This article introduces the principles and related parameters of different methods and then compares the advantages and limitations to provide a reference for future research. It is believed that geochronology is widely used, and the core lies in provenance analysis. The key to uniformitarianism is the analogy of geological background and the selection of geological parameters. The sedimentology is controlled by multiple variables, and the tectonic-climate background and research scale need to be considered comprehensively. Conclusions and Prospects Finally, this review states the development of quantitative analysis of deep-time source-to-sink systems. Under the guidance of the important idea of "the present is the key to the past", the research needs to focus on the provenance systems, sediment routing systems, sediment dispersal, and redistributive process, and coupling relationship between various parameters. Research also needs to pay attention to quantitative analysis at multiple timescales and multidisciplinary dynamic analysis. Compared with continental margin source-to-sink systems, continental lacustrine source-to-sink system patterns and prediction models need to be further improved.

The nature and amount of sediment transferred from one plate to the other near the subduction interface partly determines the tectonic and seismogenic regimeof a margin. Examination of over 500 multichannel seismic lines has enabled us to build up a global database of subduction zone front characteristics at unprecedented spatial resolution. The total thickness of sediment in the trench below the deformation front, as well as that of the subduction channel at a distance from the trench, combined with other indices such as the tectonic regime of the forearc or the migration of the volcanic front, have enabled us to revisit the accretionary or erosional character of active margins. Preliminary conclusions, based on ~3/4 of sufficiently documented subduction zones, show a predominance of the erosive character of subduction over the last million years. The flux of solid matter through the shallow part of the subduction channel is of the order of 1.5 km³/yr, and that of pore fluids 0.4 km³/yr. Some subduction zones, such as theMediterranean, are characterized by exceptional solid flux in the channel, while fluid flux is comparatively moderate. This is due to the fact that channel sediments are compacted even before subduction. Overall, fluid flux in the channel is greater under erosivemargins, due to the higher rate of subduction and often higher porosity. Maximum porosity in the channel is reached when there is neither accretion nor tectonic erosion. [ABSTRACT FROM AUTHOR]

A seasonal variability in flow and sediment flux at the Socheongcho Ocean Research Station (SORS) on the west coast of Korea in 2018 was investigated to elucidate the formation of a two-layered flow structure and changes in sediment transport during stratification. An analysis of SORS data revealed stable temperatures (5–10 °C) in deeper waters, while surface temperatures rose from 6 °C in April to a peak of 30 °C in late August, gradually declining and leading to full water column mixing by late November. This temperature variation induced stratification, influencing the development of a two-layered flow structure. In winter, a singular flow structure was observed, contrasting with the emergence of a two-layered structure as stratification progressed. In the surface layer, residual currents flowed northward in summer and southward in winter, consistent with previous studies. In deeper layers, a southward residual current persisted, irrespective of the season. Sediment flux consistently moved southward, regardless of the season or water depth, with notably higher cumulative sediment flux in the deeper layer (1300 kg·m−2s−1) compared to the surface layer (300 kg·m−2s−1). These findings diverge notably from previous studies, providing new insights into ocean currents and material transport in the Yellow Sea. [ABSTRACT FROM AUTHOR]

Tidal flats, crucial for biodiversity and ecosystem services, are facing significant alterations due to human activities such as reclamation. In South Korea, over 65% of tidal flats have been reclaimed since the 1970s, resulting in morphological changes and altered sediment transport dynamics. This study investigates sediment transport processes in the artificial Aam tidal channel, created as part of the megacity development project in Incheon, Korea. Using data from Acoustic Doppler Current Profiler and Vector instruments deployed in 2019 and 2021, we analyzed tidal asymmetry, current velocities, shear stress, and suspended sediment concentration. Our results reveal a pronounced tidal asymmetry influencing sediment transport, with ebb-dominant currents near the channel entrance and flood-dominant currents in the interior. We observed significant sediment deposition in the landward section of the channel, driven by tidal mixing asymmetry and rainfall events. These findings highlight the complex interactions between artificial structures and natural sediment dynamics, informing future coastal development and management strategies.

To understand the Holocene sedimentary evolution of the Pearl River associated delta–estuary–shelf system, high‐resolution seismic data were acquired from Lingdingyang Bay to the inner shelf. A Pearl‐derived Holocene subaqueous clinoform developed over the pre‐Holocene incised channel/valley network. Overlying the Holocene ravinement surface, progradational highstand and acoustically semi‐transparent or transparent transgressive system tracts are separated by a maximum flooding surface. Restricted and thick in‐channel/in‐valley retrogressive deposits represent an earlier transgressive deposit. Displaying a westward‐oriented along‐shore extent, the highstand sediment accumulated asymmetrically within 30 m water depths, corresponding to a modern hydrodynamic environment. The wedge‐shaped highstand unit thickened landward with a depocentre (>15 m) located in western Lingdingyang Bay, possibly because of higher sediment trap efficiency inside the salinity front. Preliminary analyses suggest that the Pearl River has been trapping sediment to fill its extensive estuarine system for most of the Holocene and its sediment trap efficiency is greater since the sea‐level highstand. Since ca 7.5 ka bp, the total volume of highstand sediment accumulated in the entire delta‐estuary‐shelf dispersal system was approximately 128.36 × 109 m3. The calculated highstand riverine sediment flux was 16.01 to 16.50 Mt/yr. This value is equivalent to approximately one‐fifth of the flux that occurred prior to widespread dam construction and likely related to late‐Holocene intensified anthropogenic influence in South China. Since ca 7.5 ka bp, only ca 35% of the Pearl‐derived sediment has been dispersed to offshore shelf areas from the delta‐estuary system. With the dramatic decrease in river sediment discharge in recent decades, a larger fraction of Pearl‐derived sediment transported to the shelf might have been interrupted and changed. [ABSTRACT FROM AUTHOR]

Although it is widely known that observations of aeolian sediment transport are susceptible to large sampling errors, sample designs are frequently used that do not sufficiently reduce the measurement uncertainties inherent in the study of aeolian processes. Here, we examine the influence of sample size (n) and sampling location on uncertainty in models of aeolian sediment transport responses to vegetation cover change. We compare measurements from a stratified random array of 27 horizontal sediment mass flux samplers to vegetative cover data collected at a 1 ha site over a period of nearly 6 years. To assess the sensitivity of modeled relationships between aeolian transport and vegetative cover to sample design, we analyze statistical regressions for all possible combinations of sample size and sampler locations. We show that at least 17 randomly located samplers are needed to consistently capture the sediment mass flux response to vegetative cover change. We found that multiple statistically significant models can describe the sediment flux‐vegetative cover relationship when using smaller sample sizes, demonstrating the risks of inferring sediment transport response from an underpowered sample design. Across vegetative functional groups, we found that woody cover generally influenced aeolian sediment transport rates more than herbaceous cover, while model uncertainty at large sample sizes (n > 17) showed the limitation of using vegetative cover as an indicator of aeolian sediment transport. Our results suggest an evaluation of sampling practices in aeolian sediment transport studies may be needed to avoid inferential errors that are likely pervasive in this field of study. Plain Language Summary: Studies of aeolian sediment transport are prone to sampling errors, largely due to the many factors that control the transport process. However, researchers often look to simplify sample designs and monitoring methods as monitoring is time consuming and expensive. To that end, vegetative cover is an easily collected and interpreted environmental indicator that affects the rates of aeolian sediment transport. However, little consideration has been given to how many samples are needed to confidently model the relationship between changes in vegetative cover and sediment transport. We investigate how changes in sample size, modeling approaches, and vegetative cover may affect inferences made about aeolian sediment transport. We show that using traditional approaches in aeolian research (using small sample sizes and relatively simple environmental data) could risk false conclusions being drawn about aeolian transport processes, even with models that appear to be accurate. If sampling does not adequately describe the sediment transport "population" response, variability in field measurements can be so large that it undermines our understanding of how and why aeolian sediment transport rates change over time. These findings may require a re‐evaluation of typical sediment transport sampling practices. Key Points: Heterogeneity in soil, vegetation, and wind cause aeolian sediment flux to have large spatiotemporal variabilityModels describing change in aeolian sediment fluxes with ground cover are highly sensitive to sampling errorLarge sample sizes and a variety of environmental indicators are needed to produce consistent models that can inform wind erosion management [ABSTRACT FROM AUTHOR]

The Himalayan orogen exports millions of tons of sediment annually to the Indo‐Gangetic foreland basin, derived from both hinterland and foreland fold‐thrust belts (FTB). Although erosion rates in the hinterland are well‐constrained, erosion rates in the foreland FTB and, by extension, the sediment flux have remained poorly constrained. Here, we quantified erosion rates and sediment flux from the Mohand Range in the northwestern Himalaya by modeling and measuring the cosmogenic radionuclide (CRN) 10Be and 26Al concentrations in modern fluvial sediments. Our model uses local geological and geophysical constraints and accounts for CRN inheritance and sediment recycling, which enables us to determine the relative contributions of the hinterland and foreland FTB sources to the CRN budget of the proximal foreland deposits. Our model predictions closely match measured concentrations for a crustal shortening rate across the Mohand Range of 8.0 ± 0.5 mm yr−1 (i.e., approximately 50% of the total shortening across the Himalaya at this longitude) since 0.75−0.06+0.02 $0.7{5}_{-0.06}^{+0.02}$ Ma. This shortening implies a spatial gradient in erosion rates ranging from 0.42 ± 0.03 to 4.92 ± 0.34 mm yr−1, controlled by the geometry of the underlying structure. This erosion pattern corresponds to an annual sediment recycling of ∼2.0 megatons from the Mohand Range to the downstream Yamuna foreland. Converted to sediment fluxes per unit width along the Himalaya, the foreland FTB accounts for ∼21% ± 5% of the total flux entering the foreland. Because these sediments have lower 10Be concentrations than hinterland‐derived sediment, they would lead to ∼14% overestimation of 10Be‐derived erosion rates, based on Yamuna sediments in the proximal foreland. Plain Language Summary: Cosmogenic radionuclides such as beryllium‐10 (10Be) are important tools for tracking erosion processes at the Earth's surface. However, they are challenging to apply when sediment remains temporarily stored for millions of years before being re‐eroded. We call this sediment recycling. We quantified sediment recycling in the Mohand Range, at the foothills of the northwestern Himalaya, based on the present‐day 10Be concentration in fluvial sediments recycled from tectonically uplifted older foreland deposits. We do this by modeling how the 10Be concentrations change as sediment is first eroded in the Himalayan source region, then deposited in the foreland, and finally eroded again. By comparing modeled and measured concentrations, we find that erosion rates in the Mohand Range vary from 0.42 ± 0.03 to 4.92 ± 0.34 mm yr−1, corresponding to about 2.0 megatons of sediment recycling from this range to the downstream Yamuna foreland. Because the 10Be concentration in recycled sediment is lower than that in sediment eroded from the high Himalaya, admixing high Himalayan sediments with recycled material may result in erosion rates that are higher than the actual erosion rates in the high Himalaya. Key Points: Novel approach for tracking cosmogenic nuclide accumulation in fluvial sediments through each step of a fold‐thrust belt sediment routing system10Be‐derived erosion rates and sediment flux from the Mohand Range in the northwestern HimalayaOnset of Main Frontal Thrust motion and rate of crustal shortening across the Mohand Range constrained by modeling 10Be concentrations in present‐day river sediments [ABSTRACT FROM AUTHOR]

Discrepancies between estimated sediment and actual yields are large. The sedimentation often causes severe damage due to a lack of on-site measurement data in the current disaster prevention system. This paper presents a robust early-warning system in which the statistical analysis used to predict sedimentation is conducted within the context of the underlying physical mechanisms. This three-phase early-warning system employs data collection, data generation, and AI (Artificial Intelligence) prediction. Data collection involves the use of HEC-HMS (Hydrologic Engineering Center – Hydrologic Modeling System) to transform measured precipitation data into flow discharge from various sub-catchments. Empirical formulas related to landslide volume and soil erosion are then used to establish suitable boundary conditions for data generation. Finally, a 2D model, SRH-2D (Sediment and River Hydraulic-Two Dimension model), is used to simulate data pertaining to temporal variations in sediment flux under various storm event scenarios. The simulated data are then used as input for the training and testing three artificial neural networks. The primary strength of this study is to improve the prediction ability in large-scale sedimentation issues in mountain rivers. These models returned good prediction results with 1–6 h lead times by interdisciplinary integration with the hydraulic and statistical fields. HIGHLIGHTS The sediment flux in the mountain basin was successfully predicted with field data and data generated by numerical modeling.; The accuracy of sediment flux predictions could be improved by adopting various data sources and greatly improves the results of conventional that rely on a single variable.; The sediment flux prediction obtained a reasonable result, and there were no difficulties in predicting underlying trends.;

[Objective] The characteristics of sand and dust transport amount and particle size on the windward and leeward sides of a natural Populus euphratica riparian forest at the Arghan section of the lower reaches of the Tarim River under the prevailing wind direction were studied in order to provide a theoretical basis for its windbreak and sand fixation capacity. [Methods] Sediments were collected from two windward sites (Y1 and Y2) and two leeward sites (B1 and B2) of the forest at five heights of 10, 30, 50, 100, and 150 cm near the surface using a BSNE sand collector. The particle size characteristics of the sand samples were then measured using a Microtrac S3500 laser diffraction particle size analyzer. [Results] ① The horizontal flux of sand and dust in the four sample plots followed either a power function or exponential function distribution, and total sediment transport followed the order of Y1 > Y2 > B1 > B2. The sediment transport for each sample plot decreased with increasing height from the soil surface. ② The reduction of sediment on the leeward side compared with the windward side ranged from 35% to 80% less than on the windward side, indicating that the natural P. euphratica riparian forest in the lower reaches of the Tarim River has obvious windbreak and sand fixation benefits. ③ The average particle size of sand grains at all heights was 80~93 μm, mainly composed of extremely fine sand. The particle size frequency curve showed a single peak distribution, and the sand dust composition was simple, mainly composed of local sand sources. [Conclusion] The sediment transport on the leeward side of the natural P. euphratica riparian forest in the study area was lower than that of the windward side. Average particle size was smaller and sorting performance was better on the leeward side than on windward side. The average particle size smaller than that of the windward side, the sorting was better than that of the windward side, the kurtosis was narrower than that of windward side, and skewness is slightly smaller than that of the windward side. The P. euphratica riparian forest exhibited obvious windbreak and sand fixation benefits, and can be used as an effective measure to reduce the damage by wind and sand transport in the study area.

Ongoing climate warming has strong moderating control over aquatic processes, such as ice cover duration, length of the growing season, vertical mixing patterns, thermal stratification, and the availability of light and nutrients. These fundamental mechanisms in turn influence the population dynamics of aquatic organisms such as diatoms and chrysophytes.In our study, over 3.5 years with contrasting meteorological conditions, we investigated eutrophic Lake Żabińskie located in northeast Poland. By combining observational data of meteorological conditions, physicochemical variables measured in the water column, and modern sedimentation, we sought to explain the relationships between changes in meteorological conditions, dynamics of total fluxes and the taxonomic composition of diatoms and chrysophyte cysts.Our results show the direct influence of meteorological conditions on physicochemical conditions and their indirect influence on total diatom and chrysophyte cyst fluxes and taxonomic succession. The former refers to the importance of air temperature and wind speed in shaping the mixing regime of Lake Żabińskie, while the latter refers to the nutrient cycling driven by changes in the mixing regime, which in turn influences the formation of biotic signals in the sediment. Our study also revealed that the biotic response to unusual meteorological conditions that occurred in 2020 (i.e., warm winter without ice cover) differed from typical years in terms of the phenology of diatom and chrysophyte cyst blooms. However, this response was not as pronounced as in lakes with lower productivity and can be attributed to the already turbid conditions and high nutrient concentrations, which alter the threshold for noticeable changes to occur. The taxonomic composition of diatoms and chrysophyte cysts also changed in response to changes in meteorological conditions.Complex interactions between physical and chemical conditions masked the direct influences of meteorological conditions on lake biota under eutrophic conditions. Nevertheless, high‐resolution monitoring enabled indirect links to be recognised. Both phenology and turnover in community composition responded to changes in meteorological conditions.These results show how ongoing climate change might affect biota in eutrophic lakes in the future. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Colorado River has flowed across the dextral strike-slip plate boundary between the North American and Pacific plates since the latest Miocene or earliest Pliocene. The Fish Creek-Vallecito Basin (FCVB) lies on the Pacific Plate in southern California, dextrally offset from the point where the modern Colorado river enters the Salton Trough; it contains a record of ancestral Colorado River sedimentation from 5.3–2.5 Ma. The basin stratigraphy exhibits a changing balance between locally derived (L-Suite) and Colorado River (C-Suite) sediments. This paper focuses on the Palm Springs Group (PSG), a thick fluvial and alluvial sequence deposited on the upper delta plain (between 4.2–2.5 Ma) when the Colorado was active in the area, allowing the detailed examination of the processes of sediment mixing from two distinct provenance areas. The PSG consists of three coeval formations: 1) Canebrake Conglomerate, a basin margin that has coarse alluvial fan deposits derived from surrounding igneous basement; 2) Olla Formation, fan-fringe sandstones containing L-Suite, C-Suite, and mixed units; and 3) Arroyo Diablo Formation, mineralogically mature C-Suite sandstones. Stratigraphic analysis demonstrates that the river flowed through a landscape with relief up to 2000 m. Satellite mapping and detailed logging reveal a variable balance between the two suites in the Olla Formation with an apparent upward increase in L-Suite units before abrupt cessation of Colorado sedimentation in the basin. Stable heavy mineral indices differentiate L-Suite (high rutile:zircon index: RZi 40–95) from C-Suite (RZi: 0–20). Both suites have garnet:zircon index (GZi) and apatite:tourmaline index (ATi) mostly above 50, although many L-suite and mixed Olla samples have much lower ATi (20–50), suggesting that the distal floodplain was wet and the local sediment had a longer residence time there, or went through several cycles of erosion and redeposition. Heavy mineral analysis, garnet geochemical analysis, and detrital zircon U-Pb age spectra allow us to quantify the amount of mixing from different sediment sources. These data show that about 30% of the mixed units are derived from the Colorado River and that up to 20% of the L-Suite is also derived from the Colorado River, suggesting that there was mutual cannibalisation of older deposits by fluvial channels in a transitional area at the basin margin. Although this study is local in scope, it provides an insight into the extent and nature of sediment mixing in a two-source system. We conclude that most 'mixing' is actually interbedding from separate sources; true mixing is facilitated by low subsidence rates and the rapid migration of fluvial channels. [ABSTRACT FROM AUTHOR]

Recently uplifted, highly erodible rocks, and recurrent high intensity storms, generate exceedingly high erosion and sedimentation rates in the East Coast Region (Tairāwhiti) of Aotearoa New Zealand. Despite the recent nature of the Anthropocene record in global terms (∼650 years since Māori arrival, 250 years of colonial impacts), human disturbance has profoundly altered evolutionary trajectories of river systems across the region. Here we document catchment-by-catchment variability in anthropogenic signature as geomorphic river stories for five catchments (Waiapu, Hikuwai, Waimatā, Waipaoa, Mōtū). We show how targeted, fit-for-purpose process-based rehabilitation programmes that manage at source and at scale are required to facilitate river recovery in each of these catchments. The largest rivers in the region, Waiapu and Waipaoa, comprise steep, highly dissected terrains that are subject to recurrent hillslope failures, including systemic shallow landslides, occasional deep-seated rotational slumps and earthflows. Localised sediment input from large (>10 ha) gully mass movement complexes overwhelms valley floors. Targeted revegetation programmes are required to reduce extreme sediment inputs from these sources. Although there are fewer gully complexes in the Hikuwai, multiple landslips supply vast volumes of fine-grained sediment that aggrade and are recurrently reworked along channel margins in lowland reaches. Waimatā has no gully complexes and a smaller number of landslips, but large areas are subject to sediment input from earthflows. The terrace-constrained flume-like nature of this system efficiently flushes materials ‘from the mountains to the sea’, recurrently reworking materials along channel banks in a similar manner to the lower Hikuwai. Systematic reforestation in the middle-upper catchment and revegetation of riparian corridors is required to reduce sedimentation rates in these catchments. In contrast, terraces buffer sediment delivery from hillslopes in the upper Mōtū catchment, where a bedrock gorge separates large sediment stores along upper reaches from the lower catchment. As reworking of valley floor sediments in response to bed incision and reworking (expansion) of channel margins is the primary contemporary sediment source in this system, bed control structures and revegetation of riparian corridors are required as part of targeted sediment management plans. We contend that geomorphic river stories provide a coherent platform for Anthropocene rehabilitation strategies that work with the character, behaviour and evolutionary trajectories of river systems. Although this generic lens can be applied anywhere in the world, we highlight particular meanings and implications in Aotearoa New Zealand where such thinking aligns directly with Māori values that respect the mana (authority), mauri (lifeforce) and ora (wellbeing) of each and every river.

A seasonal variability in flow and sediment flux at the Socheongcho Ocean Research Station (SORS) on the west coast of Korea in 2018 was investigated to elucidate the formation of a two-layered flow structure and changes in sediment transport during stratification. An analysis of SORS data revealed stable temperatures (5–10 °C) in deeper waters, while surface temperatures rose from 6 °C in April to a peak of 30 °C in late August, gradually declining and leading to full water column mixing by late November. This temperature variation induced stratification, influencing the development of a two-layered flow structure. In winter, a singular flow structure was observed, contrasting with the emergence of a two-layered structure as stratification progressed. In the surface layer, residual currents flowed northward in summer and southward in winter, consistent with previous studies. In deeper layers, a southward residual current persisted, irrespective of the season. Sediment flux consistently moved southward, regardless of the season or water depth, with notably higher cumulative sediment flux in the deeper layer (1300 kg·m−2s−1) compared to the surface layer (300 kg·m−2s−1). These findings diverge notably from previous studies, providing new insights into ocean currents and material transport in the Yellow Sea.

Two field campaigns in Dafeng and Jianggang were organized to compare spatial variations of hydrodynamic characteristics and sediment transport patterns on intertidal flats of different types with distinct human interferences along middle Jiangsu coast, China. The major contributors to the different patterns of sediment dynamics between the two tidal flats were offshore tidal current field and human interference. Offshore tidal force provide the basic setup of tidal current patterns on tidal flats, which is then modified by local morphology. Seawalls parallel to coast reduce tidal flat width, forcing tidal energy to dissipate within a shorter distance and thus influencing tidal flat morphology. Seawalls vertical to coast and major tidal current significantly reduce tidal current speed, which favors sediment deposition on tidal flats. Two seawalls built on both sides of the observational tidal flat profile caused much reduced current speed at Dafeng tidal flat, comparing to the offshore station. Being exposed to offshore radial tidal currents, hydrodynamics at Jianggang was much stronger than that at Dafeng. Residual currents at both areas showed net landward transport at the lower flat and net seaward transport at the upper flat, in favor to sediment accumulation at the middle flat. Sediment flux over tidal cycles showed net landward sediment transport at Dafeng, and net seaward transport at Jianggang, consistent with the convex-up accretion-dominated profile observed at Dafenge, and concave-up erosion-dominated profile observed at Jianggang. The instantaneons sediment flux changed significantly due to variations in velocity and sediment concentrations, but these terms counteracted with each other within tidal cycles, leading to the dominant role of Eulerian flux in determining net sediment flux over tidal cycles. [ABSTRACT FROM AUTHOR]

Paleo-relief reconstruction in source-to-sink system analysis is currently a hot topic in sedimentology, playing an important role in understanding regional tectonic evolution, climate change, surface weathering, sediment supply, and their interrelationships, and it is a key component of source paleogeographic reconstruction. Source areas in deep time are not well preserved due to later tectonic destruction, weathering, and denudation, making it difficult to reconstruct paleo-relief. The BQART sediment flux model depicts the relationship between sediment flux, bedrock lithology, river discharge, drainage area, maximum relief, and annual average temperature in an exorheic setting. When sediment flux and other parameters are acquired from the sedimentary record, maximum relief can be calculated using the BQART model. Through integration of lithofacies paleogeography, cyclostratigraphy, paleohydrolog-ical and paleogeomorphological relationship methods, a BQART model-based approach is proposed for paleo-relief reconstruction in deep time and, based on quantitative paleogeographic reconstructions, and uplift amplitudes and rates can be calculated by employing the sediment-volume backfilling method. Based on this approach, the inner zone of the Emeishan Large Igneous Province (ELIP) was estimated to be rising slowly during the Late Permian, reaching more than 200 m at the end of the Permian, with total tectonic uplift estimated as 500-750 m. This comprehensive analysis demonstrates that deep-time paleo-relief reconstruction approaches are suitable for a middle-large exorheic basin with a warm and humid paleoclimate, which is of great significance for the exploration and development of mineral resources in energy-rich basins. [ABSTRACT FROM AUTHOR]

In a river cross section or segment that has attained an equilibrium flow regime, the relationship between geometric (river depth, width, hydraulic radius, bed slope, etc.) and/or hydraulic (velocity, roughness, shear stress, etc.) factors in relation to the river's equilibrium discharge (i.e., flows of fixed nominal return period or at bankfull depth) is termed hydraulic geometry (HG). HG relations have been proposed from a multitude of approaches: empirical, statistical, physically based, and extremal. Furthermore, multiple extremal hypotheses exist, depending on the variable to be optimized (maximized or minimized). In this study, we (1) present a unified framework by invoking the principle of maximum entropy (or, equivalently, Laplace's law of insufficient reason), that is, assuming that individual contributions by geometric and hydraulic factors to HG through the optimization of extremal hypotheses (Froude number, frictional resistance, mobility index, stream power, sediment flux, etc.) presumably stem from equiprobable contributions of these factors—in other words, entropy is maximized; (2) enumerate 26 combinations (groups of sizes two to five) of the five basic HG variables, namely depth, width, slope, velocity, and friction, and analyze their interrelations; and (3) relax our initial equiprobability assumption by plugging in a scaling (weighting) parameter and show that 11 special cases of the 26 unique combinations lead to reasonable approximations of benchmark empirical results in the literature in at least one instance for each of the five extremal hypotheses considered here. The benefits of the unified framework include providing a theoretical basis to bring together various hypotheses that result in HG relations and providing an analytical way to quantify (or explain) epistemic uncertainty therein. Ultimately, this unified framework improves our understanding of HG and provides an analytical framework for improving predictions of river flows. [ABSTRACT FROM AUTHOR]

Topographic diffusivity is an often-used metric of regolith mobility. It accounts for the collective effects of climate, substrate, fauna, flora, and other factors on hillslope degradation and is used to model natural lowering in landscapes. The present study assesses where temporal variations in diffusivity derived from known past climate fluctuations have occurred. We also determine where significant differences might result when modeling landscape degradation if a long-term constant diffusivity is applied instead of diffusivity that varies through time. A space-for-time substitution approach was implemented. Through use of a transfer function that correlates current diffusivities with air temperatures, we mapped the relative diffusivities globally at a 500 yr temporal resolution for 21 ka. The analyses spanned all land areas from the tropics to the poles with a spatial resolution of 3.70° latitude by 3.75° longitude using paleo-temperature data from the TraCE-21ka global paleoclimate model. The results show Arctic and subarctic regions with the highest relative maximum diffusivities and largest variance from current values. The results suggest strong surficial dynamics in the Arctic and subarctic regions driven by local and spatially transient deglaciation and long-term stability in the tropics that correlates with relatively stable climate there through the past 21 ka. [ABSTRACT FROM AUTHOR]

Understanding trends in estuarine sediment fluxes is of great interest to sustainable estuarine management addressing anthropogenic interferences and climate change. The long‐term sediment budget of the Western Scheldt estuary, Netherlands, is investigated by a detailed analysis of a unique and long‐term bathymetric data set and data of a three‐dimensional subsurface model ('GeoTop'). Different sediment types show contrasting transport behaviour. The Western Scheldt narrowed and deepened, while the estuary exported sand (1.5 to 2.5 million m3 per year) and imported mud (0.5 to 1.5 million m3 per year) over the 1860 to 1955 period. The eroded sand originated from the channels in the seaward part of the estuary and was dispersed in all directions. A significant amount of mud permanently deposited in the side branches, which were also gradually reclaimed. These results suggest that sediment characteristics potentially play a crucial role in deriving long‐term sediment budgets and morphodynamic behaviour of estuarine environments. Future morphodynamic sand–mud model studies may reproduce and further explain the underlying transport processes of the current study. [ABSTRACT FROM AUTHOR]

Copyright of Acta Sedimentologica Sinica is the property of Acta Sedimentologica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding channel migration is essential in interpreting long‐term evolution of fluvial systems and their deposits. Using data from an experimental delta, we analyzed the kinematics of the upstream channel and assessed the relative dominance of continuous lateral channel migration versus abrupt changes (i.e., avulsions). Detailed investigation of channel centerline location at minute intervals reveals a short‐term correlation between the magnitude of migration rates measured at the same location and a spatial correlation that diminishes with distance between points. The main finding is that the channel migrates across the entire deltaic domain without large and abrupt lateral shifts but through continuous lateral migration at variable rates. Long periods of back and forth small moves are separated by short bursts of rapid lateral migration. This finding contradicts the default expectation that that aggrading systems are characterized by avulsions and suggests that highly mobile rivers tend to avulse less. We contrast this with another experiment conducted under similar conditions but with finer sediment supplied at a lower rate which shows drastically less lateral migration; the kinematics is instead dominated by periodic flow reconfiguration episodes akin to avulsions, an indication that channel migration‐style depends on the sediment load. The characteristics of these two experiments parallel two regions of the Mississippi River, the meandering and highly mobile alluvial plain and the less dynamic deltaic region, suggesting that bedload sediment deposition at the transition into backwater zone plays an important role in re‐shaping the river planform and migration style. Plain Language Summary: Water and sediment were fed into a basin to investigate how the resulting channel moves as a function of sediment rate. In one experiment, conducted with coarser sediment (1 mm) delivered at a high rate, the main channel migrated laterally at uneven rates sweeping the entire basin without abrupt flow path relocation that is referred to in the field as avulsion. Long periods of back and forth small moves were separated by short bursts of rapid migration. A comparison experiment, conducted with finer sediment (0.25 mm) supplied at a lower rate showed drastically less lateral migration. The main channel remained confined within a narrow zone for extended periods of time separated by shorter periods during which the flow spread into multiple channels. Eventually, the flow coalesced again forming a new main channel at a different location. The two experiments mirror two regions of the Mississippi River, the meandering and highly sinuous upstream fluvial region and a less dynamic deltaic region suggesting that downstream reduction in sediment load plays an important role in defining the river shape and the rate of migration. Key Points: Highly mobile fluvial systems can aggrade significantly over a wide area thorough continuous, gradual lateral migrationThe lateral migration shows complex patterns with extended periods of small lateral moves separated by bursts of rapid migrationHigh sediment rates favors gradual migration while low sediment rates result in flow reconfiguration and channel relocation akin to avulsion [ABSTRACT FROM AUTHOR]

Interrill erosion is driven by raindrops and sheet flow. Raindrop impacts cause sediment detachment and splash, but can also affect flow transport. Even if these processes have been studied for long, the actual effect of raindrop impacts on particle settling velocities has not been experimentally assessed. This leads to unconstrained adjustments in the soil erosion models, the settling velocity of particles being a freely adjustable parameter allowing for better fitting the particle flux measured at the outlet. To address the effect of raindrop impacts on the settling of particles in sheet flow, a laboratory flume experiment was designed, using an upstream feeder of sediment (100–200 μm) and simulated rainfalls. It reproduced conditions close to sheet flow, while not allowing for the detachment of particles from the flume bottom. Two series of experiments were run: a series with a high rainfall intensity (175 mm/h) generated by an oscillating‐nozzle rainfall simulator, and a series with lower rainfall intensities (10, 15, 25, 35, 55 mm/h) generated by a drop‐former rainfall simulator. When a rainfall was applied, it systematically decreased the sediment concentration at the outflow compared to the no rain condition; however, no obvious relationship was found with the rainfall intensity. This shows that raindrop impacts increase particle settling velocities in sheet flow. Two underlying mechanisms are suggested, related to the momentum of the raindrops or to the turbulence caused by the raindrops into the flow. Further studies should be carried out, using computational fluid dynamics and collaboration with the fluid mechanics community. [ABSTRACT FROM AUTHOR]

Deformation of subglacial sediment during basal slip shapes the beds of many fast‐flowing glaciers and ice streams. The resultant sediment flux impacts glacier dynamics and rates of subglacial erosion over a range of timescales, but its fundamental dependencies are not well understood. Using a cryogenic ring shear device, we conducted experiments to investigate the effects of both effective stress and slip speed on rates of till transport. Sediment fluxes were computed using digital image correlation from a photographic time series of the till bed. We find a near‐linear relationship between sediment flux and slip speed, but a non‐monotonic, double‐valued dependency of sediment flux on effective stress. Deformation primarily occurred in a thin shear band near the ice sole, the thickness of which could vary with both parameters. Coupling between ice and till increased at higher slip speeds and effective stresses and scaled the magnitude of the flow profile. Plain Language Summary: Rapid motion of many glaciers and ice streams occurs by ice sliding over soft sediment beds. This sediment is mobilized in response to stress exerted by the overriding ice, which influences rates of erosion and generates subglacial landforms over a range of timescales. However, the physical processes that control this sediment flux are poorly understood largely due to the difficulty of isolating the influence of specific variables in the field. We address this uncertainty with a custom ring shear device capable of simulating glacier slip in the laboratory at realistic pressures, temperatures, and ice speeds. We tested the influence of two key parameters on sediment deformation—the slip speed of ice and the pressure exerted by the ice on the bed—and computed the rates of sediment transport using an image processing technique called digital image correlation. We find a near‐linear relationship between sediment flux and slip speed, but a nonlinear relationship with ice pressure. Sediment deformation was mostly concentrated in a thin zone near the ice‐sediment interface. Coupling between ice and sediment increased at faster ice velocities and higher ice pressures, which scaled sediment transport rates. Key Points: Sediment flux in deforming till varies non‐monotonically with effective stressThe relationship between sediment flux and the speed of basal ice is nearly linearCoupling between ice and till causes the grain velocity profile of the bed to scale with slip speed [ABSTRACT FROM AUTHOR]

• Dam-induced sand settling in the Burdekin River delta is raising the flood levels and threatening channel avulsion. • This trapping of sand in the Delta is starving the coast of sand and generating rapid coastal erosion. • Climate change is enhancing this coastal erosion as in the last few decades the mean sea level and the frequency of strong winds have increased significantly. • This is threatening Ramsar-listed wetlands of international significance. • The connectivity of water and sediment between the various parts of river basin demonstrates the need to manage the river at the basin scale using ecohydrology principles. This study documents the impact of climate change and human activities on the Burdekin River delta and coast. The Burdekin River is located in the dry tropics with a seasonally and interannually highly variable discharge, controlled by occasional cyclones and the ENSO-dependent monsoon. Even though the peak discharge from cyclonic rainfall is decreased by a dam, large floods still occur during long-duration monsoon. While the dam traps much of the coarse sediment runoff, large amounts still reach the Delta originating from catchments downstream of the dam. The riverbed in the Delta has measurably risen in recent decades. In turn, this increases the flood levels and the threat of channel avulsion. Sand trapping by the dam and in the Delta is also starving the coast of sand, and this generates rapid coastal erosion along the 11 km long Cape Bowling Green peninsula. Climate change is enhancing this coastal erosion as in the last few decades the mean sea level and the frequency of strong winds have increased significantly. The peninsula may breach soon. As the peninsula protects Ramsar-listed wetlands of international significance, its breaching is predicted to impact the fisheries that depend on the Cape (the black marlin billfish) and on the wetlands (mud crabs, barramundi and mangrove jacks), as well as shorebirds and waterbirds. These findings demonstrate the connectivity of water and sediment throughout the river basin and the coast, and the need for management at the basin scale using ecohydrology principles. [ABSTRACT FROM AUTHOR]

Vegetation colonization is known as an effective process for stabilizing talus slopes, but little quantitative data is available about the relationships between vegetation, sediment fluxes, and sediment storage. The results of a detailed analysis of a single active fine-grained scree slope show that the upper section, scattered with shrubby vegetation, represents an environment characterized by strong biogeomorphic feedbacks. Engineering species (Thuya occidentalis, Betula papyrifera , Cornus sericea, Salix caprea) are well adapted to high sediment mobility with different modes of reproduction and survival. White cedar has a high sediment trapping capacity (>22 m3 per individual) and generates a micro-relief of 80 cm on average. It is responsible for 99 % of the volume of sediment trapped by shrub vegetation, even though it represents 44 % of the total shrub population sampled. In contrast, the hardwoods species have a very low capacity for sediment trapping (<1 m3 per individual) and micro-relief generation (>20 cm). This is likely due to the morphology of the growth which, despite a strong capacity to produce stump rejections, remains limited in trapping sediment. The shrubby vegetation directly influences the trajectory of frost-coated clast flows, the dominant slope process. Nevertheless, the vegetation appears to be quite resilient and stable on a decadal scale, where even the occurrence of extreme debris flows had little impact. In the downslope section, the debris flows, frost-coated clast flows, and snow avalanches present original and circumstantial modalities of tree-line regression. If the upper slope remains of sufficient size to allow for the occurrence of high-magnitude geomorphic events, the tree line appears to be driven primarily by slope processes rather than climate. Although it may be surprising that recent warming lowers the tree line on the studied talus slope, this provides new insight into the complex and non-linear relationships between vegetation and talus slope processes. • Shrub vegetation on active scree provides strong biogeomorphic feedbacks. • White cedar has a high sediment trapping capacity compared to hardwood species. • Engineering species are adapted to sediment mobility for reproduction and survival. • Mass-wasting processes present circumstantial modalities of tree-line regression. • Tree line is driven primarily by slope processes rather than climate. [ABSTRACT FROM AUTHOR]

Retrogressive thaw slumps (RTS) are an important landform of rapid permafrost degradation in regions with very high ground ice contents. RTS mobilize significant amounts of sediment, meltwater and organic carbon and impact downstream hydrological systems by directly affecting topography and water quality. The term megaslump has previously been coined for RTS exceeding 20 ha in size. The Batagay megaslump in the Yana highlands of NE Siberia with an area of 87.6 ha (in 2023, including the bowl-shaped part and the erosional outlet) has been identified as the largest megaslump on Earth. We use very high resolution remote sensing from satellite data and drones, geological structure modeling, and field data to assess how much and what material is thawed and mobilized in the Batagay megaslump. The total volume of permafrost thaw and material loss from the Batagay RTS amounts to about 1 million m3 per year. The material is by one third composed of thawed sediments and by two thirds of melted ground ice. About 4000 to 5000 tons of previously permafrost-locked organic carbon is released every year. Organic carbon content has been measured as Total Organic Carbon (TOC) of sediments and as Dissolved Organic Carbon (DOC) of ground ice. From its formation in the 1970s until 2023, the Batagay RTS – due to thermal denudation and headwalls retreat – mobilized a total volume of about 34.7 million m3 of which 23.4 million m3 were melted ground ice and 11.3 million m3 were thawed deposits including a total of about 169,500 t organic carbon. With these rates of sediment and carbon mobilization, the Batagay megaslump is not only a prominent local feature of rapid permafrost thaw, but offers excellent conditions to study rates and mechanisms of rapid permafrost degradations and to calculate the stock and release of, e.g., organic matter. • 3D geological modeling allowed estimating the Batagay megaslump material flux. • The megaslump mobilized ca. 35 million m3 since initiation in the 1990s. • Since 2014, the annual mobilized volume amounts to ca. 1 million m3/year. • About ⅔ of the total material volume was ground ice and ⅓ was permafrost sediments. • Organic carbon release amounts to 4000 to 5000 tons per year. [ABSTRACT FROM AUTHOR]

• Lateral migration rates in meandering rivers increase with sediment supply globally. • Migration rates respond to sediment supply similarly independent of bank vegetation. • Meander migration rates decline across sediment flux gradients caused by dams. Meandering rivers move gradually across the floodplains, and this river movement presents socioeconomic risks along river corridors and regulates terrestrial biogeochemical cycles. Experimental and field studies suggest that fluvial sediment supply can exert a primary control on lateral migration rates of rivers. However, we lack an understanding of the relative importance of environmental boundary conditions, such as floodplain vegetation and sediment supply, in setting the pace of river meandering across different environmental settings. Here, we combine the analysis of satellite imagery and global-in-scale sediment and water discharge models to evaluate the controls on lateral migration rates of 139 meandering rivers that span a wide range in size, climate, and bank vegetation. We show that migration rates normalized by the channel width monotonically increase with the volumetric sediment flux normalized by the characteristic size of the river. This relation is consistent across rivers in vegetated and unvegetated catchments, indicating that enhanced lateral migration rates in unvegetated basins is likely not only facilitated by lower bank mechanical strength, but also by higher normalized sediment supply in ephemeral rivers. Using three case examples, we also demonstrate that width-normalized meander migration rates respond to spatial gradients in sediment supply caused by river impoundments, highlighting the prominent role of sediment supply in setting the pace of meander migration. Our results suggest that sediment-supply variations caused by climate, land-cover and land-use changes can lead to predictable changes in meandering river evolution and ultimately drive architectural changes in sedimentary stratigraphy. [ABSTRACT FROM AUTHOR]

The formation of vertical sedimentary succession of a delta in the arid and semi-arid basin-margin progradation dramatically depends on the variation of sediment flux and accommodation, but the discontiguous record of signals tends to exist enormously variable, which renders the bulk record of microfacies difficult to quantify from the vertical sedimentary succession. We analyzed the 18 vertical sedimentary successions collected from 18 field trenches of a lake delta by the cusp-catastrophe model, allowing detailed mapping of microfacies. The present detailed study indicates the suitability of cusp-catastrophe theory for explaining vertical sedimentary succession in the BWH (Bawanghe) delta. Three equilibrium states of processes responsible for the deposition of the BWH delta's evolution were established: sandy-dominated upper leaves primarily exhibit the delta plain; sandy/muddy-dominated lower leaves present the delta plain and pro-delta; and sandy-dominated middle leaves which commonly developed the delta front. The result of analysis shows that the reliability of the cusp-catastrophe model to identity mutation of vertical sedimentary succession exceeds 50 %, and to identity microfacies transitions with a precipitation periodicity exceeds 70 %. These cognitions support the previous view that changing precipitation results in an abrupt change in margin progradation. Simultaneously, the study gives new insights into the microfacies quantification of lake deltas and reveals the influence of crest value changes of precipitation on vertical sedimentary succession can be understood from the dependence of microfacies distribution on the change of sediment flux and accommodation. [ABSTRACT FROM AUTHOR]

The Colorado River has flowed across the dextral strike-slip plate boundary between the North American and Pacific plates since the latest Miocene or earliest Pliocene. The Fish Creek-Vallecito Basin (FCVB) lies on the Pacific Plate in southern California, dextrally offset from the point where the modern Colorado river enters the Salton Trough; it contains a record of ancestral Colorado River sedimentation from 5.3–2.5 Ma. The basin stratigraphy exhibits a changing balance between locally derived (L-Suite) and Colorado River (C-Suite) sediments. This paper focuses on the Palm Springs Group (PSG), a thick fluvial and alluvial sequence deposited on the upper delta plain (between 4.2–2.5 Ma) when the Colorado was active in the area, allowing the detailed examination of the processes of sediment mixing from two distinct provenance areas. The PSG consists of three coeval formations: 1) Canebrake Conglomerate, a basin margin that has coarse alluvial fan deposits derived from surrounding igneous basement; 2) Olla Formation, fan-fringe sandstones containing L-Suite, C-Suite, and mixed units; and 3) Arroyo Diablo Formation, mineralogically mature C-Suite sandstones. Stratigraphic analysis demonstrates that the river flowed through a landscape with relief up to 2000 m. Satellite mapping and detailed logging reveal a variable balance between the two suites in the Olla Formation with an apparent upward increase in L-Suite units before abrupt cessation of Colorado sedimentation in the basin. Stable heavy mineral indices differentiate L-Suite (high rutile:zircon index: RZi 40–95) from C-Suite (RZi: 0–20). Both suites have garnet:zircon index (GZi) and apatite:tourmaline index (ATi) mostly above 50, although many L-suite and mixed Olla samples have much lower ATi (20–50), suggesting that the distal floodplain was wet and the local sediment had a longer residence time there, or went through several cycles of erosion and redeposition. Heavy mineral analysis, garnet geochemical analysis, and detrital zircon U-Pb age spectra allow us to quantify the amount of mixing from different sediment sources. These data show that about 30% of the mixed units are derived from the Colorado River and that up to 20% of the L-Suite is also derived from the Colorado River, suggesting that there was mutual cannibalisation of older deposits by fluvial channels in a transitional area at the basin margin. Although this study is local in scope, it provides an insight into the extent and nature of sediment mixing in a two-source system. We conclude that most ‘mixing’ is actually interbedding from separate sources; true mixing is facilitated by low subsidence rates and the rapid migration of fluvial channels.

Continental rifts form by extension, and their subsequent evolution depends on the tectonic and climatic boundary conditions. We investigate how faulting, topography, and the evolution of the sediment flux during rifting are affected by these boundary conditions, in particular whether it is possible to correlate tectonic activity, topography, and sediment flux on long timescales (40 Myr). We use a thermomechanical model coupled with a landscape evolution model and present a series of 14 models, testing the sensitivity of the models to crustal strength, extension rate, and fluvial erodibility. The degree of strain localization drives the structural evolution of the modeled rifts: slow extension, high crustal strength, and efficient surface processes promote a high degree of strain localization, resulting in fewer active faults with larger offset. Overall, the magnitude of sediment production correlates with the degree of strain localization. In case of unchanged erosional power and similar amount of extension, systems with slower extension produce more sediment owing to a stronger positive feedback between erosion and fault offset. We observe a characteristic sequence of events, reflecting the morpho‐tectonic evolution of rifts: the highest rock uplift rates are observed before the maximum elevation, and the highest sediment flux postdates the peak in elevation. Our results indicate that for natural systems, the evolution of the sediment flux is a good proxy for the evolution of topography, and that a time lag of 2–5 Myr between the peaks in main tectonic activity and sediment flux can exist. Plain Language Summary: Continental rifting is the response of the uppermost part of the Earth to extensional, tectonic forces. The resulting landscape consists of subsided, sediment‐filled basins and uplifted, high‐elevation rift shoulders. Resolving what contributes to rifting on long‐timescales (i.e., tens of millions of years) from natural examples is challenging, since inverting the sedimentary record to resolve correlations between tectonic activity, topography, and the sediment production relies on several assumptions. We use computer models to simulate continental rifting, and subject the models to different boundary conditions. This allows us to have a holistic view of the rifting process under variable conditions over a 40‐million‐year period, and we assess how the topography, tectonic deformation, and sediment production evolve over time. We see that the degree of localization of deformation is decisive for the evolution of the rifts, and that localization correlates with sediment production. Furthermore, the temporal evolution of the sediment production reflects the tectonic and topographic evolution. Moving from models to natural examples, our findings indicate that the evolution of the sediment production is a good proxy for topography. However, a time lag of 2–5 million years could exist between the main tectonic activity and the highest sediment production. Key Points: Coupled, thermomechanical models show that during continental rifting, the sediment flux reflects the topographic evolution of riftsHigh crustal strength, slow extension, and efficient surface processes promote strain localization and sediment productionModel results suggest a time‐lag of 2–5 Myr between rifting and the peak in sediment flux [ABSTRACT FROM AUTHOR]

The southeastern portion of the Yangtze River Estuary (or Yangtze Estuary) was considered to be the deposition center and the mudbank of the Yangtze River Delta. As the fluvial sediment supply began to decline in the 1980s and the reduction accelerated after the completion of the Three Gorge Dam in 2003, more fluvial sediment was trapped decreasing the suspended sediment concentration (SSC) environment in the river mouth area. Moreover, the accretion rate of the mudbank has slowed down in recent decades. In fact, the mudbank shrank and has faced a regime shift from sediment sink to source. A better understanding of the tidal-scale dynamics and spatial variability of the system is essential to explore the conversion of the sediment sources and sinks in the Yangtze Estuary affected by natural variations and human activities. Flow velocity, salinity, and suspended-sediment concentration during spring and neap tides were measured at three sites on the mudbank in July 1982 and July 2013. The variation in flow was not significant at all the sites measured in the study area from 1982 to 2013. However, the sediment dynamics changed remarkably over these three decades. The temporal distribution of the SSC increased in the bottom layer. The SSC was much larger during the early flood tide period in 2013. The tidal range increased by nearly 10% and the flood dominance increased in the study area from 1982 to 2013. The salinity dynamics underwent a transition from a stratified system in 1982 to a well-mixed system in 2013. The landward sediment budget increased remarkably from 1982 to 2013. The decreased fluvial sediment supply, increased flood dominance, well-mixed salinity, and increased tidal range were directly responsible for the larger landward sediment budget and more severe erosion in the mudbank in 2013. The current results reveal the flow and sediment dynamics during the conversion of the sediment sink to source. Furthermore, it was determined that the sediment-starved process in the estuarine environment, which occurred due to the reduction in the fluvial sediment, leads to an increased landward transport of sediment. The current study provides a clear understanding of the mechanisms governing the delta system transition in the mudbank of the Yangtze Estuary, which is useful for delta protection in the future. • Sediment in the mudbank of the Yangtze Estuary were transported to offset reduced fluvial sediment into the river mouth. • The mudbank experienced increased tidal asymmetry, weaker stratification, and decreased fluvial sediment in recent decades. • Fluvial sediment reduction and estuarine engineering projects have contributed to the conversion of source and sink. [ABSTRACT FROM AUTHOR]

Sedimentary systems respond to environmental forcings in dissimilar ways over different timescales. The Lake Malawi (Nyasa) Rift is an ideal natural laboratory for evaluating the overall functioning of lacustrine source‐to‐sink systems on orbital or younger scales. These closed sedimentary systems exhibited high spatiotemporal climate variability, and their responses to two late Pleistocene lake‐level stillstands are evaluated. The coarse‐grained deposits documented a dramatic transgression from 350 to 200 m below present lake‐level (BPLL) developed during an important climate transition in tropical Africa. Based on an integrated analysis of a digital elevation model and high‐resolution single/multi‐channel seismic profiles, catchment geomorphology has been linked with sediment delivery in the sink area. The coarse‐grained deposition of each source‐to‐sink system is quantified through a sediment mass calculation. A modified empirically‐derived 'BQART' predictor with a bedload equation to assess the sediment discharge is employed based on a Monte Carlo simulation, considering temperature lapse rate and topographic effects. The river discharges are estimated by specific empirical relationships that associate catchment area to various climate systems, developed using a global modern river database. The results show that the total sediment discharge increases from 7.53 to 9.50 Mt year−1; likewise, the preserved coarse‐grained deposits also record a significant increase in deposition rate from 350 to 200 m BPLL stage, indicating that the short length‐scale source‐to‐sink systems are sensitive to the high‐amplitude lake transgression developed from the climate shift. The volume of upstream buffered deposits may decrease within the progressively wetter climate, while the buffering degree was substantially influenced by the pre‐existing landforms. Moreover, the substantial deep‐water mud dispersal is not well‐developed, despite the relatively higher lake‐level and slightly wetter climate. This quantitative source‐to‐sink analysis with the modified sediment predictor yields preliminary constraints for system functioning in response to high‐amplitude climate change in a closed sedimentary system. [ABSTRACT FROM AUTHOR]

Rivers act as 'jerky conveyor belts' that transmit fluxes of flow and sediment downstream. This transmission of fluxes can be highly variable within a drainage basin resulting in either abrupt or gradational sediment (dis)connectivity patterns and processes. This study assesses sediment (dis)connectivity across a basin as a means to understand the locational, transmission and filter sensitivity properties of a fluvial system. Drawing upon the case study of Richmond River Catchment, New South Wales, Australia we use the concepts of effective catchment area and buffers, along with graph theory and an empirical sediment transport model CASCADE (Catchment Sediment Connectivity and Delivery), to assess (1) the degree to which modelled sediment cascades along the river network are connected or disconnected (2) how the position, pattern and configuration of (dis)connection facilitates or restricts geomorphic adjustment in different parts of a catchment, and (3) use the findings as a basis to explain the locational-transmission-filter sensitivity of the catchment. We use this analysis to segregate supply limited and transport limited reaches and identify various controls on sediment dynamics: in-stream sediment storage units, junctions between different geomorphic river types, tributary confluences and sediment storage units within partly confined floodplain units. Such analysis lays the foundation for network scale identification of potential hotspots of geomorphic adjustment. [ABSTRACT FROM AUTHOR]

Assessing rivers' and hillslopes' sensitivity to external forcing is paramount to understand landscape evolution, in particular as a response to Quaternary climate changes. River networks are usually considered to be the main conveyors of environmental signals, such as changes in precipitation, temperature, or baselevel. Yet because hillslopes provide the source of sediment for river networks, their response to environmental change also modulates landscape dynamics. In order to characterize such behavior, we analyze the response times of a transport‐limited hillslope. We use simple numerical models of denudation to study hillslope responses to oscillatory forcing and understand their filtering effects on environmental signals. Modifications in the frequency of climate oscillation, such as the change that occurred at the Mid‐Pleistocene Transition, can significantly modulate hillslope sediment‐flux response. We infer a wide range of hillslope responses, ranging from negligible change over the full range of climate‐forcing frequencies, to a significant filtering of long‐period signals. Plain Language Summary: Landscapes are constituted of hillslopes and rivers where different types of erosion and sediment transport processes take place. Due to their large extent, river networks are an important driver of global landscape response to climatic or tectonic changes. Hillslopes have smaller dimensions but are also where most sediment production occurs and for that reason it is important to have a good understanding of how they respond to perturbations. We use simple numerical models of hillslope evolution to study the influence of oscillating changes of either the efficiency of sediment transport across the hillslope or the rate of channel downcutting at its base. Our results indicates that the period of oscillations for these perturbations controls the amplitude of the sediment flux response out of the hillslope, and provide a framework to understand how this landscape component reacts to climatic cycles such as the glacial/inter‐glacial oscillations of the Quaternary. For example, a major change occurred 800 ka ago with a shift in climate oscillation from 40 to 100 ka period. Our models suggest that in some landscapes this change in period alone could have induced a significant decrease in the amplitude of hillslope sediment flux response. Key Points: A complex hillslope dynamics is associated with the linear to nonlinear sediment flux transitionHillslopes filtering potential of external signals is highly contrasted depending on the type of forcingChanges in the climatic signal frequency at the Mid‐Pleistocene Transition could induce a significant shift in hillslope erosional response [ABSTRACT FROM AUTHOR]

Bay–marsh systems, composed of an embayment surrounded by fringing marsh incised by tidal channels, are widely distributed coastal environments. External sediment availability, marsh-edge erosion, and sea-level rise acting on such bay–marsh complexes may drive diverse sediment-flux regimes. These factors reinforce the ephemeral and dynamic nature of fringing marshes: material released by marsh-edge erosion becomes part of a bay–marsh exchange that fuels the geomorphic evolution of the coupled system. The dynamics of this sediment exchange determine the balance among seaward export, deposition on the embayment seabed, flux into tidal channels, and import to the marsh platform. In this work, we investigate the sediment dynamics of a transgressive bay–marsh complex and link them to larger-scale considerations of its geomorphic trajectory. Grand Bay, Alabama/Mississippi, is a shallow microtidal embayment surrounded by salt marshes with lateral erosion rates of up to 5 m year−1. We collected 6 months of oceanographic data at four moorings within Grand Bay and its tidal channels to assess hydrographic conditions and net sediment-flux patterns and augmented the observations with numerical modeling. The observations imply a divergent sedimentary system in which a majority of the suspended sediment is exported seaward, while a smaller fraction is imported landward via tidal channels, assisting in vertical marsh-plain accumulation, maintenance of channel and intertidal-flat morphologies, and landward transgression. These results describe a dynamic system that is responsive to episodic atmospheric forcing in the absence of a strong tidal signal and the presence of severe lateral marsh loss. [ABSTRACT FROM AUTHOR]

The processes underlying sediment transport mechanics are still debated. Here, we present novel ensemble particle bedload measurements, obtained with high‐frequency imaging of particle velocities and activity over various bedform migration stages. We show that the bedload particle flux quickly responds to the unsteady non‐uniform flow over the bed. Mean particle velocity linearly increases over the dune slopes towards the crest. In contrast, particle activity exhibits a power law increase over the dune slopes, with the top layer almost saturating in the saltation regime. Furthermore, the spatial and temporal variability of particle motion over dune slopes is high. For lower flow, spatial and temporal variability from small‐scale topography, such as superposed bedforms, spurs, and irregular crestlines, are shown to be important for quantifying sediment dynamics. With increasing flow, however, the cross‐stream particle velocities increase significantly, influenced by the large‐scale dune topography (transverse slopes). Overall, variability in the particle flux increases with both flow strength and frequency of turbulent events. For the mean particle flux over the dune slopes, however, differences between neighboring dunes are large, which are attributed to dune topography variations and flow acceleration. The presented insights are essential to validate numerical simulations of sediment dynamics in three‐dimensional flow conditions over dune beds. Plain Language Summary: Rivers convey water and sediment, often resulting in bedforms covering riverbeds. Yet, our understanding on how individual sediment particles contribute to the formation of various bedforms remains rudimentary. This major knowledge gap is mainly due to a complete lack of direct particle measurements over bedforms. Here, we present the collection of a novel data set of not only bedforms, but also individual particles that contribute to the formation of the bedforms, for a riverbed in controlled laboratory conditions. Using cameras to visualize and quantify the transport of sediment, we can appreciate and quantify the complexity of sediment transport and the limitation of present theories. Key Points: Particle activity of the bedload layer saturates, whilst particle velocity continues to increase over dune stoss slopesBedload particle flux responds to small‐scale topographic features for lower flows, while it is independent for higher flowsSediment transport peaks over the upper section of the dune stoss slopes [ABSTRACT FROM AUTHOR]

Reconstructing the original depositional level of the Mesozoic and older c'salt giants' can reveal if their basins became filled to global sea level, but is complicated by dissolution, diapirism and because the time elapsed is so great. This is less of a problem in the Red Sea, a young rift basin that is transitioning to an ocean basin and where the evaporites away from coastal fringes are less affected by diapirism. In this study, we explore vertical movements of the evaporite surface of the central Red Sea imaged with deep seismic profiling, for the period of time after most evaporite deposition ended at 5.3 Ma (the Miocene-Pliocene boundary). This boundary is readily mapped across the basin as a prominent reflection in seismic data correlated with stratigraphy at three DSDP sites. We quantify changes in the average elevation of the evaporite surface due to (a) thermal lithospheric subsidence, (b) isostatic loading by Plio-Pleistocene sediments and water, (c) deflation needed to balance the volume of evaporites overflowing oceanic crust of 5.3 Ma age, (d) loss of halite by dissolution and (e) dynamic topography. Our best estimate of the evaporite level (-132 m air-loaded or -192 m water-loaded) lies below the range of estimated global sea level towards the end of the Miocene, suggesting that the basin remained under-filled. If geological interpretations of shallow water conditions existing at the end of the Miocene (Zeit Formation) are correct, this implies that the water level of the Red Sea declined and was unstable. These calculations illustrate how spreading of evaporites can enhance thermal subsidence to cause rapid development of accommodation space above major evaporite bodies, which in the Red Sea case has remained largely unfilled. [ABSTRACT FROM AUTHOR]