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River sediment supply (Qs) and longshore sediment transport (LST) are recognized as two paramount controls on river delta morphodynamics and stratigraphy. We employed the Delft3D model to simulate the evolution of deltas from fluvial to wave‐dominated conditions, revealing the interplay between river‐ and wave‐driven sediment quantities. Wave‐influenced deltas may show alternating accumulation and retreat patterns driven by avulsions and wave‐induced sediment diffusion, posing coastal management challenges. Deltas with higher wave energy evolve under a fine balance between river supply and intense wave‐mediated sediment redistribution and are highly vulnerable under conditions of sediment reduction. Reducing Qs by ∼40%–70%, common in modern dammed rivers, can rapidly shift bypass from ∼0 to 1 (no bypass to complete bypass). This leads to accelerated diffusion and potential sediment loss in modern deltas. The study highlights the importance of accurately computing sediment quantities in real‐world deltas for improved management, especially under increasing anthropogenic and climatic pressures. Plain Language Summary: Ocean waves, like proficient sculptors, shape the meeting points of rivers and seas—where deltas are created. Under the power of ocean waves, the sediments transported by rivers are organized into distinct patterns. Using an advanced computer model, our research unveils how this interplay affects the physical form of these deltas and their functioning. In certain conditions, the sediment carried by waves can jump over the river mouth and move further along the coastline, contributing to stretching the delta and inducing erosion. Currently, river sediments are getting blocked behind river dams, depriving deltas of their sediment nourishment. As sediment supply decreases, powerful waves at the sea erode deltas more easily, endangering ecosystems, human communities and infrastructure. Because deltas are facing challenges from climate change and increased human activities, informed and innovative management strategies based on better knowledge of natural processes are needed to preserve these valuable coastal regions. Key Points: Deltas transition from avulsion‐dominated with localized depocenters to more diffuse and alongshore‐deflected wave‐dominated depocentersBypass increases and trapping decreases abruptly when longshore transport (LST) at the river mouth equals river sediment transport (Qs)LST under large‐scale blocking due to mouth bar and shoreface adjustment feeds wave‐dominated updrift beach ridge plains (strandplains) [ABSTRACT FROM AUTHOR]

Morphometric analysis of previously unresearched tributary junction fans (TJFs) of the Spiti valley cold desert, India, was conducted to understand the factors influencing their development. An integrated remote sensing and field approach was employed, including the development of multi-method morphometric indices viz. fan conicality (FCI), sweep angle (SA), fan width-to-length ratio (W/L), feeder stream-order and valley floor width-to-height ratio (Vf). Such TJFs, which are the most suitable cultivation and settlement sites in this region, were found to be largely polygenic and planimetrically confined, with many being multi-staged in terms of their development. The results of morphometric analyses reveal that the TJFs are relatively smaller but steeper than their counterparts in other settings, with high relative topographic confinement causing the construction of smaller and steeper fans. The competence of the feeder stream, along with associated processes, notably influences fan morphology using differential sediment transporting capacity. TJFs created by more competent streams are less steep, more influenced by topographic confinement and more vulnerable to truncation by the trunk stream. Furthermore, tectonically induced base-level fall and resultant downcutting in confined environments have caused the formation of truncated, multi-staged and entrenched fans and are primarily responsible for coupling between TJF catchments and trunk stream in the study area. [ABSTRACT FROM AUTHOR]

Enzyme-induced carbonate precipitation (EICP), which precipitates calcium carbonate within the soil matrix to cement the granular grains, presents a promising bio-mediated approach for scour countermeasures. This study explores the erosion performance of bio-cemented sand in a closed-conduit flume system, investigating the effectiveness of EICP in mitigating scour and reducing erodibility. Various parameters such as curing duration, cementation degrees and urease activities are examined to understand their influence on erosion behaviors. Furthermore, the study incorporates the analysis of calcium carbonate content and crystal microstructure to provide a better understanding on the EICP mechanism in scour mitigation. These results highlight the critical role of the interaction between calcium carbonate content and crystal features in determining the effectiveness of erodibility reduction. As the precipitated amount increases, the cemented soil exhibits enhanced hydraulic erosion resistance, with the erosion mode shifting from particle erosion and aggregated detachment to chunk fracture. In other words, the mode of sediment transport essentially is affected by the variations in crystal size, crystal quantities and deposited morphology. Two predictive formulas for threshold Shields parameter and erosion rate are also developed. Notably, the cemented soil could maintain its stability under an elevated flow of 4 m/s under an EICP treatment with 1 M of urea and calcium chloride, and a curing duration of 24 h. These findings are anticipated to serve as a valuable theoretical foundation for engineering applications. [ABSTRACT FROM AUTHOR]

Although the Carpathian Mts. area is considered as extremely prone to surface erosion which results in capacity loss of the dammed reservoirs, a lack of data to follow details of this process is perceivable. The research of the selected sediment fractions transport tracking was conducted using the capabilities of the digital platform—Macromodel DNS (Discharge‐Nutrient‐Sea) for the catchment with drinking water reservoir in the Polish part of Western Carpathian. The continuity of sediment transport simulation in two hydrologically different elements of the catchment—the river and the reservoir—was possible due to consolidation of two models in the platform—SWAT (Soil & Water Assessment Tool) and AdH/PTM (Adaptive Hydraulics Model/Particle Tracking Model). The result of those modules' integration was a database for tracking the individual sediment fractions delivered to the reservoir and deposited in specific reservoir zones. The implementation of climate and land use change scenarios allowed additionally to analyse the estimation of those processes in the future. The simulation outcomes consist of daily flows and monthly sediment loads at the reservoir inflow and the individual sediment particle fractions deposition location inside of the reservoir. [ABSTRACT FROM AUTHOR]

ABSTRACT Present day submarine canyons are active conduits for the transfer of large volumes of sediment, carbon and pollutants from continents to oceans. However, the evolution of submarine canyons over geological timescales remains poorly understood due to their erosional nature and low preservation potential. The Late Cretaceous Punta Baja Formation represents a well‐preserved submarine canyon‐fill that evolved on a tectonically‐active ocean‐facing margin. Exposures provide kilometre‐scale continuous strike and dip sections of the 120 m thick and 1.2 km wide feature. An inherited tectonic fabric influenced the location and orientation of canyon incision into fluvial bedrock. The stratigraphic evolution of the Punta Baja submarine canyon is reconstructed from incision to fill, which shows that it remained an active sediment conduit throughout the time represented by the preserved fill. The depositional architecture of the north–south oriented erosionally confined canyon‐fill is asymmetrical, with sub‐vertically stacked channel‐fills to the west, and an overbank confined by the canyon margin to the east. Sedimentary process interactions led to depositional patterns that are considered distinct to submarine canyon fills. Dynamic topography generated by mass‐wasting processes captured sediment and drove knickpoint development, an autogenic mechanism that modifies sediment delivery to the ocean floor. Widespread upstream dipping surfaces in channel‐fills are interpreted as the stratigraphic expression of upstream migrating supercritical‐flow bedforms, which played an important role in sediment storage and transport in the canyon. The steep relief and internal topography of canyons leads to complicated and characteristic confined overbank flow behaviour and depositional patterns. This study provides insight into how processes that are observed in modern canyons are selectively preserved through the lifetime of the canyon and construct or destroy stratigraphy on geological timescales. [ABSTRACT FROM AUTHOR]

Depth of closure (DOC), the point in a beach profile where surface wave action no longer impacts the sediment on the seabed, is used in several coastal engineering application (e.g., beach fill in beach nourishment project, placement of dredged materials). Measurement of DOC requires long term measurements on the evolution of coastal profile data which is not readily available for many locations around the world. Empirical formulation relating the DOC with statistical properties of wave height and period and other drivers of coastal profile are often used to compute DOC for wide range of applications. In this study, empirical formulation and associated uncertainty of standard models used to calculate DOC are revisited. These models are evaluated and compared using local wave data and recalibrated to improve local efficacy. Recalibrated models are then applied to climate change models to project future DOC and examine coastal retreat along the coast of Louisiana. [ABSTRACT FROM AUTHOR]

The Paleogene paleotopography of the western United States, which may grant insight into Farallon subduction dynamics and North American Cordillera orogenic processes, can be constrained by reconstructing drainage networks through sediment provenance studies. In the northern Sierra Nevada, the provenance of SW-directed, Paleogene paleochannel deposits is controversial; prior studies favor either sources proximal to the deposits or distal source areas in central Nevada. These different hypothesized source areas would have contrasting implications for the paleotopography of the Sierra Nevada and western Basin and Range. We conducted a new provenance analysis of paleochannel deposits in the Sierra Nevada and western Nevada using new and compiled detrital zircon U-Pb age data from across the preserved paleochannel network, together with compiled bedrock geochronologic ages of potential sediment source areas for the paleochannel deposits. The geochronology compilation of potential source areas reveals systematic longitudinal variations in bedrock ages within the study area. Jurassic ages are present primarily in the western Sierra Nevada batholith, Cretaceous ages are dominant in the eastern Sierra Nevada batholith, and Eocene ages are present only in north-central Nevada. The distribution of potential source ages allows confident inference of sediment provenance from detrital zircon U-Pb ages. The distributions of detrital zircon U-Pb ages in the paleochannel deposits can be categorized into three distinct types. The first type, found in the vicinity of Malakoff Diggins State Historic Park (SHP) and further northwest, is dominated by Jurassic, Paleozoic, and Precambrian ages reflecting derivation from local sources in the western Sierra Nevada, and also contains scattered Eocene ages. The lack of Late Cretaceous ages in these samples, despite the presence of Late Cretaceous plutons in close proximity to the east, suggests small sediment source areas with fluvial transport of zircon grains no farther than 50 km. The few Eocene ages in these samples likely reflect volcanic air fall, consistent with an overlying tuff at one sample site that is interpreted to have its volcanic source to the north, outside the paleochannel network. The second zircon age distribution type, from samples south of Malakoff Diggins SHP, includes Cretaceous and Jurassic ages representative of exposed bedrock across the entire width of the Sierra Nevada batholith but no Eocene ages. This combination of ages suggests a sediment source area that encompassed the entire batholith but did not include north-central Nevada. The third zircon age distribution type, from samples to the northeast of Malakoff Diggins SHP, contains Jurassic, Cretaceous, and Eocene ages consistent with fluvial derivation of sediment from the entire width of the Sierran batholith as well as from north-central Nevada. This third type only occurs in fluvial deposits interbedded with Oligocene ignimbrite tuffs, whereas samples older than the Oligocene tuffs belong to zircon age distribution types 1 or 2. Thus, prior to the emplacement of Oligocene ignimbrites, there is no evidence of fluvial transport of sand-sized sediment from north-central Nevada sources to Sierran paleochannel deposits. The lack of pre-Oligocene fluvial transport across the Sierra Nevada may reflect either a Paleogene drainage divide that separated the Sierra Nevada from north-central Nevada or a large-scale knick zone with a low-gradient upstream reach that trapped sand and larger sediment. The first arrival of fluvially transported Eocene zircon grains following Oligocene ignimbrite emplacement suggests that ignimbrite volcanism, and related hinterland uplift, established or promoted sediment transport from north-central Nevada across the Sierra Nevada by driving drainage reorganization or steepening existing channels. Our provenance analysis broadly confirms previous paleochannel network reconstructions, especially for the Ancestral Yuba River, and thus validates the use of paleochannel deposits as a datum by which to infer post-Paleogene tilting of the northern Sierra Nevada. Azimuthal trends in Ancestral Yuba River paleochannel gradient suggest ~0.6° SW-directed, post-Paleogene tilting of the northern Sierra Nevada, which would have resulted in ~1 km of uplift of the range crest. Such a magnitude is consistent with Eocene–Oligocene stable isotope paleoelevation estimates. [ABSTRACT FROM AUTHOR]

In the Tsitsa River catchment of the Eastern Cape Province, South Africa, concerns regarding the sedimentation of a proposed large, multipurpose, in-channel water storage scheme prompted investigations of sub-catchment suspended sediment loads and yields. Confluence-based fingerprinting and source apportionment was undertaken to explore whether this simple approach could identify relative sub-catchment contributions to downstream sediment loads, supplementing modelling and direct sampling. In November 2018, fine sediment sequestered in bed substrates was sampled above and below confluences, using a resuspension technique. The < 63 µm sample fraction underwent analysis of mineral magnetic properties, gamma emitting radionuclide activities and geochemistry to identify suitable tracers. Conservatism and range tests were used to select different combinations of composite fingerprints at seven confluences. Bivariate source apportionment using an unmixing model showed that the approach could be used as a preliminary means of determining relative sub-catchment sediment contributions. Catchment characteristics such as geology and land cover, as well as land tenure and management, were considered as explanatory factors for the difference in sediment contributions. The results for most sub-catchments were broadly similar to those from other studies. Shortcomings of this approach included the reliance on a single sampling effort, and uncertainty associated with sub-catchment sediment transport and residence times. [ABSTRACT FROM AUTHOR]

Before the increase in anthropogenic activities, the global coastal ocean was a net autotrophic system. From human activity and the evolution of the earth, changes have been generated in its continents, oceans, atmosphere and life. Transport of sediments and bioelements to the coastal zone has been drastically altered, and there is debate about whether this zone is autotrophic or heterotrophic. This work carried out an exploratory study of five sandy beaches in the central coastal area of the state of Veracruz, three urban beaches on a gradient of anthropogenic activities in the Metropolitan Zone of Veracruz (ZMV) and two natural, non-urbanized beaches far from the ZMV to determine the concentrations and biochemical characteristics of the heterotrophic bacterial groups found in samples of surface marine sediments during two contrasting seasons in the region: dry season and rainy season. The presence of heterotrophic bacteria reflected the degree of anthropogenic disturbance that each beach presents, with a tendency to concentrate mainly on those close to urban centers. On the other hand, the anthropogenic disturbance gradient did not influence the diversity of biochemical characteristics of heterotrophic bacteria. [ABSTRACT FROM AUTHOR]

[Objective The aims of this study are to analyze the response of farmland surface runoff and sediment loss to rainfall patterns under different planting modes, to explore the laws of farmland surface runoff and sediment transport in the Poyang Lake plain area under new circumstances, and to provide scientific basis for preventing and controlling farmland surface soil erosion, [Methods] 64 rainfall events were classified using K-means clustering method, and combined with monitoring data such as runoff and sediment production in runoff plots, the impact of surface runoff and sediment losses in different rainfall types of farmlands under three planting modes were analyzed. Results] (1) The duration, rainfall and maximum rainfall intensity of 30 minutes were taken as the rainfall characteristic indicators. The rainfall could be divided into 4 types (type A: 'medium duration, small rainfall and light rainfall intensity', type B: 'short duration, small rainfall and medium rainfall intensity', type C: 'long duration, heavy rainfall and medium rainfall intensity', and type D: short duration, medium rainfall and heavy rainfall intensity'). (2) The variation of runoff and rainfall of each planting mode was basically the same, and the runoff was also more when the rainfall was larger. In each month dry farming mode produced the most runoff, (3) No matter what type of rainfall, the runoff and sediment losses of dry farming mode were the highest. Under the types A and C. the runoff and sediment yields of water farming mode were the lowest. Under the type B. the runoff reduction effect of water and dry rotation mode was the best. (4) There were significant differences in the total runoff and sediment loss under different planting modes, and the performance followed the order: dry farming mode paddy upland rotation mode paddy farming mode. [Conclusion In conclusion. compared with the dry farming model, the water farming model has certain advantages in reducing runoff and sediment, especially when dealing with type A and type C. the effect of runoff and sediment reduction is more obvious. [ABSTRACT FROM AUTHOR]

Water-reactive polymer grouts can be injected directly into contaminated sediment zones where a portion of the contaminated pore water may participate in grout polymerization and contaminants may be immobilized in the grout matrix. This study evaluated the effectiveness of injecting a water-reactive polymer grout into frozen soil for immobilizing iodide by incorporation into grouted soil monoliths. Iodide was used as a model sediment contaminant. Soil freezing is a unique method used in subsurface remediation and was investigated because it may limit the amount of contaminated water displaced and mobilized during pressure grouting. In addition, joint use of grouting and soil freezing has the potential to broadly impact other remediation challenges, for example, treatment of collapsible soil and soil in water-active areas. Variables analyzed were freezing, moisture content, iodide concentration, and accumulated pressure due to carbon dioxide gas generated during polymerization. Iodide mobilization, iodide leaching as cumulative fraction leached (CFL), effective diffusivity (D), and leachability index (LI) were evaluated. Iodide mobilized during polymer injection into frozen sands was 37.9%±12.9% which indicated that soil freezing did not prevent iodide from being mobilized when injecting the liquid polymer. Lowering the moisture content from 5% to 1.6% by weight, to align reacted water with the introduced polymer, resulted in a decrease in the mobilization of iodide to only 0.23%±0.06%. This is the lowest reported result for contaminant displacement from liquid reaction additions known to the authors. All grouted samples leached less and more slowly than the ungrouted (control) samples. Grouting reduced effective iodide diffusivity by more than 96% and the LI of the grouted soil monoliths was greater than 6.0, which meets the criteria for materials intended for shallow burial with radioisotopes. These results demonstrate that polymer grouting of sands can be used to immobilize and slow the subsurface transport of sediment contaminants. [ABSTRACT FROM AUTHOR]

Naumure Multipurpose Project (NMP) featuring a 169 m high Concrete Face Rock Filled Dam (CFRD) is the proposed reservoir project in the West Rapti River with an installed capacity of 218.34 MW. Most of the rivers in Nepal carry significant sediment loads that will consequently catalyze reservoir sedimentation. This phenomenon prevails as the primary factor in reducing reservoirs useful life, making ineffective for both flood control and hydroelectricity generation. Ultimately, such process of sedimentation has adverse impacts on projects economic feasibility and long-term sustainability. Therefore, the objective of this research was to examine the expected sediment deposition pattern in the NMP reservoir throughout its operational period by employing 1D HEC-RAS model to simulate the sedimentation process. The model was simulated for 10, 20, 30, 40 and 50 years. Yang's equation as a sediment transport function, Active layer as a bed sorting method and Toffaleti as a fall velocity method were best suited for the river reach. The delta deposition was formed between 11 km and 22 km upstream of the dam region in the Jhimruk river, with the sediment deposition depth reaching peaks of about 23 m, 38 m, 39 m, 41 m and 49 m in 10, 20, 30, 40 and 50 years, respectively. Similarly, the delta deposition was formed between 13 km and 33 km upstream of dam region in the Madi river, with the sediment deposition depth reaching peaks of about 47 m, 62 m, 60 m, 68 m and 75 m in 10, 20, 30, 40 and 50 years respectively. Headcutting of delta deposition occurred between 20 and 30 year due to high flood during low stage of reservoir. Furthermore, the study revealed that about 6.22%, 11.61%, 15.94%, 22.96% and 25.65% of the storage capacity of NMP reservoir will be depleted in 10, 20, 30, 40 and 50 years respectively. [ABSTRACT FROM AUTHOR]

Rates of land surface processes provide insights into climatic and tectonic influences on topography. Bedrock incision rates are estimated by dating perched landforms such as strath terraces, assuming a constant bedrock incision rate from terrace abandonment to the next terrace level or present river level. These estimates express biases from the stochastic nature of sediment and water discharge in controlling river incision as well as from using a mobile channel elevation as a reference frame, leading to different incision rates when calculated over different timeframes. We introduce a 1‐D model incorporating fluvial mechanics, tectonics, sediment, and climate variability to predict these biases and assess their sensitivity to climate and tectonics. Findings suggest biases intensify under highly variable climates and slow rock uplift, with climate periodicity being a primary control for our modeled scenarios. Our model provides a mechanism to improve river incision measurement uncertainty, impacting paleoclimate and tectonic geomorphology reconstructions. Plain Language Summary: Geomorphologists often measure how fast rivers erode bedrock over time by dating river terraces that have been uplifted to be higher than the elevation of the modern river channel. This helps us learn how landscapes evolve and about what past climates were like over long timescales. But this method is complicated by the fact that rivers do not erode rocks at a steady rate and the elevation of the channel surface above which we measure terrace height changes over time. We present a numerical model that predicts how these terraces develop under different climates and rates of rock uplift. Model results imply that measurements of long‐term river incision are most susceptible to temporal bias in regions experiencing highly variable paleo‐climate and slow rock uplift. Our model helps us make better measurements of river erosion and understand how climate and rock uplift shape landscapes. Key Points: We present a numerical model that reproduces biases in rates of river incision measured from strath terracesWe find that these measurement biases are the strongest when climates are highly variable and rock uplift is slowUnderstanding bedrock incision measurement biases allows for bias correction in field studies and improves data comparability [ABSTRACT FROM AUTHOR]

In rivers, the addition of finer sediment to a coarser riverbed is known to increase the mobility of the coarser fraction. Two mechanisms have been suggested for this: a geometric mechanism whereby smaller sizes smooth the bed, increasing near-bed velocity and thus mobility of the larger sizes, and a viscous mechanism whereby a transitionally smooth turbulent boundary layer forms, rendering the coarser grains more mobile. Here, we report on experiments using two sediment mixtures to better understand these proposed mechanisms. In Mixture 1, we used 0.5 and 5 mm grains, and in Mixture 2, we used 2 and 20 mm grains. If the entrainment of coarse gravel by finer sediment is a purely geometric effect, then the addition of finer material should produce the same effect on the mobility of the coarser material for both mixtures because they have the same size ratio. We show that addition of finer material has a different effect on the two mixtures. We observed an increase in the mobility of the coarse fraction for both mixtures, but the increase in coarse fraction mobility for Mixture 1 was almost twice that for Mixture 2. Our experiments show that in addition to the geometric effect, enhancement of coarse gravel transport by finer sediment is also driven by a viscous effect. [ABSTRACT FROM AUTHOR]

Integrating coastal topographic and bathymetric data for creating regional seamless topobathymetric digital elevation models of the land/water interface presents a complex challenge due to the spatial and temporal gaps in data acquisitions. The Coastal National Elevation Database (CoNED) Applications Project develops topographic (land elevation) and bathymetric (water depth) regional scale digital elevation models by integrating multiple sourced disparate topographic and bathymetric data models. These integrated regional models are broadly used in coastal and climate science applications, such as sediment transport, storm impact, and sea-level rise modeling. However, CoNED's current integration method does not address the occurrence of measurable vertical discrepancies between adjacent near-shore topographic and bathymetric data sources, which often create artificial barriers and sinks along their intersections. To tackle this issue, the CoNED project has developed an additional step in its integration process that collectively assesses the input data to define how to transition between these disparate datasets. This new step defines two zones: a micro blending zone for near-shore transitions and a macro blending zone for the transition between high-resolution (3 m or less) to moderate-resolution (between 3 m and 10 m) bathymetric datasets. These zones and input data sources are reduced to a multidimensional array of zeros and ones. This array is compiled into a 16-bit integer representing a vertical assessment for each pixel. This assessed value provides the means for dynamic pixel-level blending between disparate datasets by leveraging the 16-bit binary notation. Sample site RMSE assessments demonstrate improved accuracy, with values decreasing from 0.203–0.241 using the previous method to 0.126–0.147 using the new method. This paper introduces CoNED's unique approach of using binary code to improve the integration of coastal topobathymetric data. [ABSTRACT FROM AUTHOR]

Iron‐rich, ferruginous waters were the dominant geochemical regime for most of Earth's history. Modern ferruginous waters are found in stratified, sulfur‐poor lakes, and serve as crucial analogs for biogeochemical cycling throughout Earth's past. Here we present the first depth‐resolved data of physical structure, nutrients and trace elements from Lake Poso (Indonesia), a deep oligotrophic ancient lake. Lake Poso is ferruginous, with anoxia below ~ 90 m depth, placing it among the world's largest ferruginous lakes. Physical stratification is weaker than other tropical anoxic lakes, indicating sensitivity for paleoclimate reconstructions. Trace elements and nutrients are predominantly shaped by the oxic–anoxic transition. Manganese– and Fe oxyhydroxide–driven biogeochemical cycling occurs at distinct depth horizons, with Co and Ni controlled by Mn and showing shallow release in anoxic waters, while V, Cr, P, and As are controlled by Fe, with release in surface sediments and diffusive transport. Chromium is nonquantitatively removed in anoxic waters, in contrast to widespread assumptions in Cr‐based paleoreconstructions. Oxycline U and Se removal corresponds to a local N minimum, suggesting biological reduction and/or uptake. These first ferruginous water Se data also show removal in sediments, indicating sediment signals reflect multiple removal processes and informing Se‐based paleoreconstructions, while the absence of sediment U removal contrasts other anoxic basins. A comparison with other ferruginous lakes demonstrates how local influences drive deviations from expectations in other systems, and highlight common, generalizable ferruginous basin features. Therefore, these data will guide research in ferruginous settings across space and time, and improve paleoreconstructions from ferruginous sediment records. [ABSTRACT FROM AUTHOR]

Logjams create an upstream backwater of deepened, slower water, locally reducing bed shear stress. We compared hydraulic impact of logjam series across 37 geomorphically diverse reaches of mountain streams observed over 11 years in the US Southern Rockies. To enable reach‐scale comparison of logjam structure and spacing, we identified the modeled best‐fit effective resistance coefficient minimizing difference between outflow exiting a 1D channel with logjams present, and the same model channel with elevated channel resistance. Effective resistance increased with ratio of jam upstream depth to depth without a logjam, ratio of backwater length to average spacing, and decreased for randomly distributed jams due to close spacing, which reduced backwater impact. An analytic approximation and boundaries for region of relative spacing with steepest increase in effective resistance are provided. Our results can assist in targeting interventions to areas where hydraulic impact is greatest, providing value for money in nature‐based solution design. Plain Language Summary: In a river channel, logjams created by wood pieces create upstream backwater regions with slower, deepened water. By creating a backwater, logjams increase heterogeneity of habitat and sediment transport and increase connection between river channel and floodplain. We compared logjams in 37 reaches of mountain streams in the US Southern Rockies. The sites studied had high variation in logjam density, channel steepness, channel width, and floodplain width. To compare between reaches and identify the ability of logjam backwaters to slow water within a river channel, we found an effective channel resistance coefficient that produced similar model output as a reach containing a series of logjams. The effective resistance increased with ratio of jam upstream depth to flow depth without a logjam, and ratio of backwater length to average spacing. The highest rate of increase in effective resistance with more logjams in the river reach occurs for an intermediate range of inter‐jam spacing relative to backwater length. Engineered logjam and wood addition projects could target this range to provide the most benefit per intervention. Key Points: We compared the hydraulic impact of logjams, identified by effective resistance, across 37 reaches and 11 years in the Colorado RockiesEffective resistance increases with decreasing stream power, analytically linked to dependence on jam structure and spacingObserved random jam distribution reduces effective resistance compared to uniform distribution, due to backwater truncation [ABSTRACT FROM AUTHOR]

Sediment residence time (SRT) is a key parameter of the Earth's surface system, bridging the realms of sediment transport, biogeochemical cycles, sedimentary archives, and watershed management. SRT in mountainous catchments includes the time particles have spent in the subsurface weathering zone, which has been challenging to measure thus limiting our understanding of the magnitude and controlling factors of SRT in steep terrains. In this study, we apply the 234U/238U activity ratio, (234U/238U), which reveals particle comminution age, to estimate SRTs in 32 catchments (drainage area of 6.79–143.67 km2) draining an active mountain range at the eastern margin of the Tibetan Plateau. The uranium comminution age allows us to account for the time that particles have spent in the weathering zone. The sampled catchments span a range of erosional, topographic, climatic and lithologic conditions, providing a unique opportunity to explore the controlling factors on SRTs. We measured the (234U/238U) of the 20–25 µm size fraction of the collected riverbed sediment samples and used the results to calculate particle comminution ages, which are used to approximate SRTs of fine sediment in the catchment. We then investigated the relationships between estimated SRTs and denudation rates, topography, climate, and lithology to assess controls on SRTs. The estimated SRTs range from 5.0 to 149.2 ka, and exhibit strong negative correlations with the 10Be-derived denudation rates and metrics for landscape steepness (relief, gradient, and channel steepness), with weak-to-moderate correlations with climatic and lithologic conditions. By combining the SRTs and denudation rates and assuming a steady-state weathering zone, we estimate a catchment-average comminution depth of 1.98 to 28.7 m, comparable to the depth of weathering zone estimated from modeling studies. Considering a topographic steady-state where denudation rates are in equilibrium with uplift rates, our results suggest that tectonic uplift exerts a primary control on the SRT in active mountain ranges, such that faster uplift rates shorten SRTs. Our findings suggest that tectonic uplift could regulate the temporal duration of chemical weathering by limiting the SRTs of fresh minerals in mountainous regions, sustaining a 'kinetically-limited' weathering scenario. [ABSTRACT FROM AUTHOR]

The construction of large reservoirs has modified the process of water and sediment transport downstream, resulting in changes in the morphology of the river cross-section. Changes in water and sand transport and cross-sectional morphology are reflected in the rating curve at the cross-section. This study analyzed the variations in the rating curve at the Huayuankou (HYK) section and their influencing factors, and conducted water level predictions based on this relationship. The findings revealed that while the annual mean water level has shown a declining tendency over the past 20 years, the annual mean discharge has shown a constant pattern. The rating curve at this stretch narrowed from a rope-loop type curve in its natural condition to a more stable single curve as a result of the construction of the dam upstream of the HYK section. The effect of pre-flood section morphology and the water–sediment process on the scattering degree of the rating curve is inverse; increasing roughness and hydraulic radius decreases scattering degree, while increasing sand content and sand transport rate increases scattering degree. Using the measured data from 2020 as an example, the feasibility of predicting cross-sectional water levels using the rating curve was verified. The prediction results were accurate when the flow was between 1000 and 2800 m3/s; However, when the flow was between 2800 and 4000 m3/s, the forecast results were typically slightly lower than the measured values. Overall, the method demonstrates good predictive accuracy. Insight from the method can be used to predict water levels to better inform decision making about water resources management, and flood emergency response in the lower Yellow River. [ABSTRACT FROM AUTHOR]

The construction of large reservoirs has modified the process of water and sediment transport downstream, resulting in changes in the morphology of the river cross-section. Changes in water and sand transport and cross-sectional morphology are reflected in the rating curve at the cross-section. This study analyzed the variations in the rating curve at the Huayuankou (HYK) section and their influencing factors, and conducted water level predictions based on this relationship. The findings revealed that while the annual mean water level has shown a declining tendency over the past 20 years, the annual mean discharge has shown a constant pattern. The rating curve at this stretch narrowed from a rope-loop type curve in its natural condition to a more stable single curve as a result of the construction of the dam upstream of the HYK section. The effect of pre-flood section morphology and the water–sediment process on the scattering degree of the rating curve is inverse; increasing roughness and hydraulic radius decreases scattering degree, while increasing sand content and sand transport rate increases scattering degree. Using the measured data from 2020 as an example, the feasibility of predicting cross-sectional water levels using the rating curve was verified. The prediction results were accurate when the flow was between 1000 and 2800 m3/s; However, when the flow was between 2800 and 4000 m3/s, the forecast results were typically slightly lower than the measured values. Overall, the method demonstrates good predictive accuracy. Insight from the method can be used to predict water levels to better inform decision making about water resources management, and flood emergency response in the lower Yellow River. [ABSTRACT FROM AUTHOR]

Catastrophic sediment overloading of mountain streams in response to coseismic landsliding causes river systems to fundamentally reorganize their morphology and sediment transporting characteristics, influencing sediment yields, bedrock incision, and the coupling between erosion and tectonics. A sequence of 13 airborne LiDAR surveys of an alpine tributary of the Hāpuku River, New Zealand, reveals patterns of sediment mass balance change over 5 years following delivery of 6.6 million cubic meters of landslide debris during the 2016 magnitude 7.8 Kaikōura earthquake. The surveys reveal how mountain river systems modulate catastrophic sediment deliveries to their lower reaches through sediment storage, evolution of channel morphology, and armoring of the bed. Variations in valley width contribute to the delay and diffusion of the seismically induced disturbance "wave" as it moves across river process domains. The landslide sediment train remnants may persist for longer than the return time of their triggering mechanism, leading to a long-lived hiatus in bedrock incision in this tectonically active mountain catchment. [ABSTRACT FROM AUTHOR]

The laser stripe method (LSM) for measuring solids distribution in sediment-laden flow has been extended to accommodate the presence of multiple sediment fractions which can differ in particle size and shape. A measurement setup with two lasers emitting green and red laser sheets was utilized to measure the vertical distribution of the near-wall concentration of a bimodal sediment mixture composed of green and red particles. The extended method was calibrated under controlled conditions in a calibration cell and was validated for measuring distributions in sediment-laden flow in a laboratory tilting flume. The results from the flume demonstrate that the extended LSM can successfully produce vertical profiles of the total concentration of all particles and the relative concentration of the two fractions. The accuracy of total concentration measurements using the extended LSM is consistent with that of the original LSM, both exhibiting an error of 0.015. The extended LSM evaluates the relative proportion of individual fractions with an error of 0.05. [ABSTRACT FROM AUTHOR]

Understanding soil erosion and sediment transport from the hillslope scale to the regional scale is crucial for studies on water quality, soil‐water conservation, the lateral carbon cycle, environmental zoning and vulnerability. However, most existing erosion and sediment transport models are only applicable at the hillslope scale or for small watersheds with fine spatial resolutions (typically much less than 1 km). This study presents a process‐based soil erosion and sediment transport model for model applications designed for applications with coarse spatial (e.g., ≥10 km) and temporal (e.g., from hourly to daily) resolutions. This new model, referred to as VIC‐SED, effectively accounts for interactions between erosion and hydrological processes. This is achieved by tightly coupling the erosion processes with a hydrologically based Three‐layer Variable Infiltration Capacity (VIC‐3L) land surface model (LSM) and to a multi‐scale routing (MSR) model. VIC‐SED considers the impacts of (a) the spatio‐temporal variability of rainfall intensity on erosion processes and (b) soil moisture on the soil detachment process. VIC‐SED is evaluated in two watersheds. Results demonstrate that VIC‐SED is capable of reproducing water and suspended sediment discharges at coarse spatial resolutions and varying temporal scales varying from 15‐min to daily intervals. Our study indicates that the VIC‐SED model is a promising tool for studying and assessing the impacts of climate and land cover changes on suspended sediment yields over large regions using coarse spatial and temporal resolutions. Plain Language Summary: Soil erosion is a global issue impacting soil‐water conservation, making the qualification of sediment transport crucial for evaluating water quality and landscape evolution. Existing models predominantly focus on hillslopes or small watersheds, with limited applicability to larger spatial scales. This limitation is partly due to the complexity of erosion processes and the empirical formulations involved in the erosion and sediment transport. To address this gap, we developed a novel process‐based soil erosion and sediment transport model for large‐scale land surface modeling. This model is integrated with the sophisticated Three‐layer Variable Infiltration Capacity (VIC‐3L) hydrological model and a multi‐scale routing (MSR) scheme for water and sediment transport. It explicitly accounts for the spatial and temporal variability of rainfall intensity and formulates the impact of soil moisture on the soil detachment process. Results from two applications demonstrate the model's capability to predict soil erosion and sediment dynamics at large spatial and temporal scales. Key Points: A novel process‐based SED model is developed for applications with coarse spatial and temporal resolutions of precipitationThe SED model is coupled with VIC accounting for subgrid‐scale variability of rainfall intensity, soil, vegetation, and flow path lengthThe coupled VIC‐SED model is evaluated with two case studies and its model parameters are insensitive to spatial and temporal resolutions [ABSTRACT FROM AUTHOR]

Pleistocene outburst floods from the drainage of glacial Lake Missoula carved bedrock canyons into the Columbia Plateau in eastern Washington, USA, forming the Channeled Scabland. However, rates of bedrock incision by outburst floods are largely unconstrained, which hinders the ability to link flood hydrology with landscape evolution in the Channeled Scabland and other flood-carved landscapes. We used long profiles of hanging tributaries to reconstruct the pre-flood topography of the two largest Channeled Scabland canyons, upper Grand Coulee and Moses Coulee, and a smaller flood-eroded channel, Wilson Creek. The topographic reconstruction indicates floods eroded 67.8 km³, 14.5 km³, and 1.6 km³ of rock from upper Grand Coulee, Moses Coulee, and Wilson Creek, respectively, which corresponds to an average incision depth of 169 m, 56 m, and 10 m in each flood route. We simulated flood discharge over the reconstructed, pre-flood topography and found that high-water evidence was emplaced in each of these channels by flow discharges of 3.1 × 106 m³ s−1, 0.65–0.9 × 106 m³ s−1, and 0.65–0.9 × 106 m³ s−1, respectively. These discharges are a fraction of those predicted under the assumption that post-flood topography was filled to high-water marks for Grand and Moses Coulees. However, both methods yield similar results for Wilson Creek, where there was less erosion. Sediment transport rates based on these discharges imply that the largest canyons could have formed in only about six or fewer floods, based on the time required to transport the eroded rock from each canyon, with associated rates of knickpoint propagation on the order of several km per day. Overall, our results indicate that a small number of outburst floods, with discharges much lower than commonly assumed, can cause extensive erosion and canyon formation in fractured bedrock. [ABSTRACT FROM AUTHOR]

The World's one of largest inhabited river-made island Majuli, developed in response to depositional processes of large sediment load carried by the Bramhaputra River and Subhansari River from the Himalayan hinterland. But, for decades it has been going through a significant rate of erosion, which is severely threatening the existence of the island and its rich cultural heritage. These erosional processes result in exposure to island depositional records and provide an opportunity to study these sedimentary deposits. This paleo depositional record is very well analysed by adopting the methodology of facies identification and their relationship diagram. A total of 18 exposed outcrop sections are studied with detailed sedimentological documentation, facies identification and symbols assigned to facies. Then calculations and tabulations are carried out for Facies Relationship Diagram (FRD) along with the construction of the sequence model, which provides a lateral and vertical lithofacies association developed in the entire island sequentially. On the basis of validation of obtained data through field survey and analysis of more vertical profiles, we study the correlation between existing bank erosion and dominated sedimentary facies at Majuli Island. This analysis results in two facies sequences: one mud-dominated and the other sand-dominated facies. The Massive Mud and Massive Sand beds are represented as the main facies between these two sequences. Therefore, mud-dominated sequence represents the Flood Plain deposit, whereas the sand-dominated sequence represents Bar and Channel deposits. This study also reveals that sedimentary sequences developed by the Bramhaputra River are mud dominated, while that of the Subhansiri River is both mud and sand sequences. This reflects the differential source to sink transport of sediments, as the Bramhaputra River carries sediment load for a longer distance than the Subhanshiri River. This study also reveals that areas of sand-dominated facies show higher erosion than mud-dominated facies. Therefore, the sedimentary record of the Subhansiri River is more vulnerable to erosion. [ABSTRACT FROM AUTHOR]

Rapid urbanization has an accelerated impact on catchment hydrology and geomorphology due to land use and land cover changes as a result of anthropogenic development activities in river catchment areas that cause increased surface runoff and higher sediment yield. The present study investigates the channel changes and sediment transport phenomena, including bed material movement from the upstream to the estuaries of the Pahang River Basin, Peninsula Malaysia. The river geometry survey associated with the spatial variation in sediment transport has confirmed that changes in river bed profile occur due to the erosion and sediment deposition along the Pahang River. The sediment size distribution for the Pahang River was very coarse sand and gravel after the December 2014 flood. The river geometry survey showed a gentle slope that can induce lower discharge typical of alluvial rivers relating to flood events. Quantitative assessment of sediment load is, therefore, of critical importance for future river basin management. [ABSTRACT FROM AUTHOR]

Offshore structures are deployed extensively to harvest marine resources. Due to the harsh marine environments and heavy-duty working conditions, the risks associated with failure due to scour are high, and the need for accurate prediction of these risks is increasing. Often, pipelines and cables are critical elements of subsea energy transportation and telecommunication, and they are highly susceptible to scour-induced failure. The scour around spheres is relevant to the offshore industry as a simplified three-dimensional representation of subsea structures. This paper presents a numerical study, using FLOW-3D HYDRO, of the scour around on-bottom cylinders and spheres. Whereas most published research investigated scour around stationary solid objects, this paper presents numerical results of a more challenging case of scour around sagging cylinders and spheres. The model was validated against published experimental and numerical results. The scour depth was found to increase with the decrease of the sagging velocity of the solid object. For sagging horizontal cylinders, the scour depth reaches a plateau of 1.1 times the cylinder diameter when the dimensionless sagging velocity is smaller than 0.094. For sagging spheres, the maximum scour depth reaches 0.37 times the sphere diameter when the dimensionless sagging velocity is reduced to 0.0103. The findings provide guidelines for future research on more complicated interactions between flow, solid objects, and the seabed, accounting for the deformation of infrastructure over time. Practical Applications: This paper concerns the flow, sediment transport, and scour around horizontal cylinders and spheres undergoing slow downward motion, which resembles the sagging of on-bottom infrastructure under the influence of gravity and bed erosion. Offshore structures are deployed extensively to harvest marine resources. Pipelines and cables are critical subsea infrastructures that are susceptible to scour-induced failure. Spherical objects are commonplace in the offshore industry, so a sphere can be deemed as an idealized three-dimensional body. This paper provides detailed FLOW-3D simulations and developed empirical relationships between the dimensionless scour depth and dimensionless sagging speed. Most previous research considered only the scour around fixed objects, so this paper provides a novel addition to the existing knowledge on the scour phenomenon. The computational methods established in this study are useful for simulating more-complicated scenarios. The findings provide guidelines for more-realistic predictions of scour and for the design of scour mitigation measures. [ABSTRACT FROM AUTHOR]

Rainfall erosion can cause environmental and economic damage by decreasing the storage capacity of water reservoirs because of the detachment of soil particles. The purpose of this study was to develop a one-dimensional physicomathematical model that can help predict the effects of rainfall erosion on the banks of water reservoirs. The model was developed using the Mein–Larson model to describe water infiltration, the kinematic wave approximation to represent overland flow generation, and the steady state sediment continuity equation to estimate sediment transport. The model was validated using rainfall simulator tests and lateritic soil samples with a bimodal soil–water retention curve. The results showed conformity with the experimental data, identifying a threshold in the models for discharge per unit area and sediment yield rate, as well as a linear increase in the models for total runoff and sediment load per unit area. However, the model failed to capture the peak in sediment yield rate owing to raindrop impact during the initial minutes of rainfall. Parametric analysis highlighted the impact of increasing the calibration constant of splash erosion, erodibility coefficient, and critical shear stress on the slope of the sediment load per unit area model. Despite its limitations, the model demonstrates satisfactory predictive capability for sediment load per unit area under high-intensity rainfalls, achieving an R2 greater than 0.92 in five of the six cases examined. [ABSTRACT FROM AUTHOR]

The sedimentary record of the Paleocene–Eocene Thermal Maximum (PETM, ca. 56 Ma) allows the study of feedback mechanisms over the entire duration of a climatic event, from carbon release to the subsequent recovery phase. Clay sedimentation increase in the oceans during the PETM is linked to enhanced terrestrial erosion. Fluvial channel mobility has been invoked to explain this increase in fine sediment export based on more frequent transitional avulsions. In this study, we test whether the reworking of Microcodium (prismatic calcite concretions) from the floodplain to marine environments can serve to fingerprint floodplain reworking due to channel mobility. We quantified the abundance of floodplain-sourced Microcodium grains reworked in fluvial to marine sandstones pre-dating and coeval to the PETM in the Southern Pyrenees (Tremp Basin, Spain). Laser ablation–inductively coupled plasma–mass spectrometry U-Pb ages on calcite confirm the Thanetian age of the Microcodium grains. Our data show a four-fold increase in the export of floodplain sediments to the marine domain during the PETM. Moreover, we show that this is predominantly due to enhanced channel mobility, reworking channel banks and interfluves, with increased erosion in the hinterland as a secondary factor. This increase in floodplain reworking would correspond to an increase in biospheric carbon burial flux by a factor of 2.2. Therefore, enhanced channel mobility and fine-grain sediment transport to the oceans during a climatic perturbation such as the PETM may constitute an important negative feedback mechanism. [ABSTRACT FROM AUTHOR]

Active orogens balance tectonic rock uplift with erosion, commonly via river incision coupled to landslide denudation of “threshold” hillslopes, but sediment’s role in this feedback is unclear. We report fluvial geometry and sediment size, prevalence, and mobility across two ≤600-m-tall gneissic northern Alaska Range anticlines that sustain steep landslide-clad hillslopes but differ 10× in late Pleistocene–recent rock uplift rate. Enigmatically, the river steepens and narrows prominently across the fold experiencing slow surface uplift (∼0.5 mm/ yr) but remains low-gradient and wide downstream across the anticline undergoing rapid differential rock uplift (∼5 mm/yr). Frequent bedload mobilization across both folds implies fluvial equilibration to sediment transport despite discrepant channel forms and similarly prevalent hillslope-derived boulders. Boulder prevalence correlates significantly with channel slope and width on the slowly uplifting anticline, but weakly on the rapidly uplifting anticline. Strong correlations across the tectonically quiescent anticline may reflect local incision-suppressing boulder aggradation that forces the channel to steepen and narrow, consistent with field observations. Conversely, weak correlations across the rapidly uplifting anticline imply that boulders may modulate expected tectonic channel adjustment by preferentially aggrading to subdue slope, and deflecting frequently mobile bedload to drive lateral erosion that maintains channel width, steepens adjacent hillslopes, and perpetuates hillslope-channel coupling. Hence, hillslope-derived boulders may occupy important roles in regulating feedbacks between river incision and landslide erosion that differ fundamentally at high and low tectonic rates. [ABSTRACT FROM AUTHOR]

Sedimentary landforms on Earth and other planetary bodies are built through scour, transport, and deposition of sediment. Sediment connectivity refers to the hypothesis that pathways of sediment transport do not occur in isolation, but rather are mechanistically linked. In dryland river systems, one such example of sediment connectivity is the transport of fluvially deposited sediment by wind. However, predictive tools that can forecast fluvial‐aeolian sediment connectivity at meaningful scales are rare. Here we develop a suite of models for quantifying the availability of river‐sourced sediment for aeolian transport as a function of river flow, wind regime, and land cover across 168 km of the Colorado River in Grand Canyon, USA. We compare and validate these models using topographic changes observed over 10 years in a coupled river sandbar‐aeolian dunefield setting. The models provide a path forward for directly linking fluvial hydrology with the management and understanding of aeolian landscapes. Plain Language Summary: Landscapes on Earth are built from sediment, which is deposited by a variety of processes, especially water and wind. In rivers located in dry regions, sediment is deposited by flowing water during river floods. Once this sediment dries, it is often then moved by wind across the landscape. Although we frequently observe this sediment connectivity between water and wind, we are not currently able to predict when and where windblown transport of river‐deposited sediment may occur. We used maps of sand in Grand Canyon along 168 km of the Colorado River, along with records of river flow, wind speed, and vegetation cover, to develop four models that predict how much sediment is available for wind to move. We compared the results of these models to actual windblown sediment transport at a study site in Grand Canyon, finding that when models predicted more sand was available at the site, we also observed more landscape changes there which were due to wind. Our research makes it possible to understand how changes in river flows affect the amount of sediment moved by wind. Key Points: We developed four methods for modeling the extent of exposed, bare sand available for windblown transport in river valleysOur models employ data on river flow, land cover, wind velocity, and vegetation to predict exposed, bare sand extent at corridor scalesWhere models predict increased areal extent of bare sand, we also observe a greater volume of topographic changes driven by wind [ABSTRACT FROM AUTHOR]

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

Green sea dykes, also known as ecosystem-based sea dykes, represent a novel type of coastal defense consisting of both traditional structural engineering and coastal ecosystems, designed to cope with the future trends of sea level rise and intensified storms. Here we focus on the mid-latitude mud coasts (eastern China in particular), which face the most prominent risks of storm surge, storm-induced giant waves, and shoreline erosion, and summarizes the scientific basis of green sea dykes and the current status of engineering practices. We show that the basic mechanisms of nearshore wave energy dissipation include bottom friction, sediment transport, and form drag. These explain the wave damping capacity of oyster reefs and salt marshes on mud coasts. In tidal flat environments, oyster growth increases frictional resistance and even causes wave breaking; the resuspension and transport of fine-grained sediments on salt marsh beds and the movement or resistance to hydrodynamic forcing of salt marsh vegetation stems effectively dissipate wave kinetic energy, and their efficiency increases with the elevation of the bed surface. Based on the wave damping capacity of oyster reefs and salt marshes on mud coasts, ecosystem-based sea dykes are being built in combination with traditional structured sea dykes. By utilizing natural tidal flats outside the dykes or implementing artificial modification projects, a certain scale of salt marshes and/or oyster reefs can be maintained, which serve to protect the sea dykes and enhance their wave resistance functions. From the perspective of system optimization, it is necessary to further improve the efficiency and sustainability of green sea dykes under constraints such as regional environment characteristics, ecosystem health, investment capacity, and ecological resilience. Related scientific issues include the theorization of the wave damping process of salt marshes, the niche and scale control of oyster reef and salt marsh ecosystems, the establishment of engineering standards and the design of the optimal form of sea dykes. [ABSTRACT FROM AUTHOR]

Mining activities can lead to an exacerbated enrichment of metal concentrations. Pollution by metal(loid)s in arid regions has been little elucidated. This study assessed the transport and mobilization of trace elements in an arid environment under two ephemeral wash systems originating from processed tailing materials in the Valley Wells Smelter, California (USA). Overall, enrichment factors evidence a significant increase in trace elements in the South Wash compared to the North Wash. The Principal Component Analysis demonstrates in the South Wash that Cd-Cu is associated with As-Pb-Zn and Ba-Co-Mn primarily. All areas (from South and North wash) indicated extremely high enrichment of Cu due to mining activities. Data showed that in the northern wash area the metals As, Cu and Sr presented concentrations much higher than the background. The geochemical survey indicates deleterious effects on the environmental quality of the investigated areas, requiring reparative and conservative measures. [ABSTRACT FROM AUTHOR]

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

The phenomenon of rhythmic patterns of the coastal-zone morphology (beach cusps, longshore sand waves, spits, and nearshore bars) is considered the result of self-organization of the relief when a positive feedback is established between sediment transport and morphology. It is shown that the dynamics of the contour and profile of the coast can be described in terms of the diffusion equation, which allows for both attenuation and growth of relief perturbations. The conditions are determined under which the self-organization mechanism is activated and the resulting perturbations grow over time. Rhythmic structures of the coastal contour are traditionally associated with waves propagating at a large angle relative to the coastal normal. However, it has been shown that the self-organization of beach cusps and megacusps also occurs in normal coast waves due to the development of circulation cells in the surf zone. The conclusion is substantiated that the formation of nearshore bars under certain conditions is also determined by the self-organization mechanism. The results obtained help to interpret the available observational data regarding the evolution of multiple bar systems. [ABSTRACT FROM AUTHOR]

The in situ measurement of sediment transport in wave‐dominated environments presents significant challenges and currently often relies upon the use of fluorescent sediment tracers. However, this method is constrained by challenges in conducting unbiased and representative sampling, as well as facing overall logistical complexities and labour‐intensive procedures. Whilst other tracer techniques are available, such as using magnetic tracers, their performance in tracking sediment transport has not been quantified. The objective of this study is to assess the effectiveness of magnetic tracers in evaluating net transport rates and tracer dispersal patterns. Conducted in a controlled large wave flume, the experiments simultaneously employed fluorescent and magnetic tracers, allowing a comprehensive comparison of the tracers' dispersion patterns and the net transport rates. Results show that the dispersal of magnetic and fluorescent tracers displays a high degree of spatial coherence in both horizontal and vertical dimensions. Similarly, net transport rates are comparable (<16% difference), both showing net transport in the direction of the wave propagation (towards onshore) driven by non‐linear and streaming effects. Magnetic tracer recovery rate (49%) was lower than for fluorescent tracers (73%) and is attributed to the loss of magnetic ink from particles; an aspect of the magnetic technique that requires improvement. This study therefore indicates that the use of magnetic tracers to quantify sediment transport is an effective method with the advantages of being significantly less labour‐intensive than using the commonly applied fluorescent sediment tracer method. [ABSTRACT FROM AUTHOR]

Large rivers are characterized by large water discharges, high suspended sediment fluxes and low slope, and typically display multiple channels that are separated by large complex bars. The most common channel style found in these rivers is characterized by the alternating presence of single and multiple channel threads. Mid‐channel compound bars separate a main deeper channel from shallower secondary channels, leading to low‐order braiding and low to moderate sinuosity. Despite the importance of this type of river for global terrestrial sediment transport and the interpretation of ancient fluvial successions, integrated depositional models for large multi‐channel rivers are still not fully developed. This paper interprets the channel morphodynamics and depositional architecture of such large rivers by investigating the distinctive features of their laterally‐accreting mid‐channel bars in the Solimões–Amazonas River. This is achieved by examination of temporal series of satellite images, quantification of bedforms using multibeam echosounding surveys, analysis of shallow seismic and ground penetrating radar surveys of selected areas, and on‐site field observations and sample collections. Such mid‐channel bars produce directional variability in planform scroll bar accretion of up to 180°. As these bars – and their associated channels – evolve, they become progressively shallower, due to the bifurcation of the two channels and the resultant partitioning of discharge that leads to a gradual reduction in transport capacity within the outer channel. The preserved successions of this process in the alluvial plain are characterized by fining‐upward trends, with larger cross‐strata sets at mid‐depths and internal erosional surfaces marking distinct cycles of bar development with potentially differing palaeocurrent trends. The new depositional models proposed for these mid‐channel bars and channels constitute a basis for the recognition of large multi‐channel river deposits in the ancient rock record. [ABSTRACT FROM AUTHOR]

Numerical forward modelling and laboratory experiments suggest that autogenic factors in the sediment routing system serve as long‐pass filters, preserving only orbital cycles with a period exceeding the compensation timescale, Tc, or thickness in the depth domain exceeding the compensation depth scale, Hc. For a specific orbital cycle with a certain period, this preservation in alluvial strata occurs unless it exhibits a sufficiently large amplitude. This study stratigraphically confirms, for the first time, the long‐pass filtering of autogenic dynamics using elemental data from the alluvial–lacustrine Sifangtai and Mingshui formations in the Songliao Basin. Spectral analysis of the Si and Zr series in coarse‐grained sediments reveals no cyclic signal with thicknesses below the estimated lower limits of Hc. This implies that the spatial storage threshold for orbital cycles in proxies of the coarse‐grained sediment component is equal to or less than Hc. However, cyclic signals of obliquity and precession with smaller thicknesses are identified in Ti, Fe and Al enriched in the fine‐grained sediment components of the stratigraphy. Notably, previously reported proxies preserving high‐frequency orbital cycles are derived from fine‐grained sediment components, differing from the sedimentation rate series used in the reported experimental studies. Therefore, the authors hypothesize a grain‐size component‐dependent storage threshold, suggesting that the storage threshold of orbital cycles in proxies associated with fine‐grained components is lower. This hypothesis arises from the weaker effect of autogenic dynamics on the content of fine‐grained sediment components transported to the sampling site by a suspended load compared to coarser components that are subjected to stronger autogenic dynamics within or near channels. The hypothesis and model presented propose a dynamic process elucidating the nuanced roles of autogenic dynamics in preserving orbital cycles. This perspective, considering sediment composition, inspires prioritizing proxies enriched in the fine‐grained fraction for identifying allogenic cycles in alluvial strata. [ABSTRACT FROM AUTHOR]

Nearshore incised valleys are important conduits for the transport of sediment, nutrients, pollutants and organic carbon from the continents to the sea. Therefore, it is essential to understand the autogenic evolution of deltas confined within incised valleys and how such evolution is affected by relative sea‐level rise. To date, limited research has focused on how deltas constrained by incised valleys or other forms of antecedent topography respond to rising sea level. An existing theory of autostratigraphy envisages scenarios in which two‐dimensional or unconfined three‐dimensional fan deltas can experience three evolutionary stages under constant rates of relative sea‐level rise and sediment supply: progradation, autoretreat and post‐autobreak transgression. In this work, an integrated study of geometric numerical models and physical experiments is undertaken to investigate autostratigraphic delta evolution for a variety of incised‐valley geometries, under conditions of constant rates of relative sea‐level rise and sediment supply. Results indicate that interplays of antecedent topography (valley geometries) and sediment mass balance expressed in resultant deltaic geometries can result in autogenic changes in shoreline dynamics and river avulsion frequency on deltas. The following primary findings arise. (i) Compared to valleys with rectangular and trapezoidal cross‐sectional profiles, valleys with triangular cross‐sections tend to contain deltas that experience faster rates of progradation, autoretreat and post‐autobreak transgression under rising sea level, and exhibit a more prominent convex‐seaward shoreline trajectory. (ii) The shoreline trajectory is also related to delta topset geometry, becoming more convex‐seaward under decreasing topset slopes. (iii) River avulsion frequency on deltas with rising sea level varies markedly across valleys with different geometries, even under the same rate of relative sea‐level rise; this is attributed to the difference in temporal evolution of shoreline migration for different valley geometries and the resultant difference in the delta topset aggradation. This study highlights complexities in responses of sedimentary systems under the confinement of different topographic configurations that have hitherto largely been overlooked in sequence‐stratigraphic models. The findings provide insight into future shoreline behaviour and river avulsion hazard on confined deltas, and for decoding the stratigraphic record. [ABSTRACT FROM AUTHOR]

The aim of this study was to provide a broader view of the transport and mobilization of metal(loid)s in sediments from the Yellow Pine Mill site in Goodsprings, Nevada. This mine was principally a lead ore operation located in the township of Goodspring, Nevada. From the two wash systems originating from processed tailing piles of the mill the contaminant migration was evaluated. Concentrations of metal(loid)s in sediments were up to 10 times higher in the south wash than in the north. Maximum levels of As and Pb in surficial south wash sediments were 103 and 1351 mg kg−1, respectively. Similarly, the enrichment factors of Cd, Cu, and Pb were far lower in north wash tailing than those obtained for south wash. Principal component analysis (PCA) data from the south wash shows PC2 explained 13.98% of the total variance and loadings on Zn (0.982), Cu (0.875), Pb (0.778), and Cd (0.690), which can be considered anthropogenic component associated with mine tailing. Evaluation of the transport mechanism of sediments indicates that metal(loid)s in sediments were found to have been derived from anthropogenic activities and migrated at least 1050 m beyond source materials in the south wash. Sediment transport from source areas to the wider environment during storm events. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to explore the scale effect in the process of runoff and sediment movement on the slope, to clarify the scale effect influence mechanism of runoff and sediment movement in the hilly and gully region of the Loess Plateau, so as to provide scientific support for the study of runoff and sediment transfer mechanism and the comprehensive management of runoff and sediment in the Yellow River Basin. [Methods] Based on the runoff and sediment data of four runoff fields in Zizhou runoff test station of the Yellow River, the scale transfer effect of runoff and sediment yield on slope was revealed by comparing and analyzing the runoff and sediment yield processes of different slope lengths under rainfall events. The concept of scale transfer efficiency was proposed to characterize the runoff and sediment transfer relationship between the upper and lower levels, and to further explore the influencing factors on runoff and sediment transfer efficiency. [Results] (1) The characteristics of different rainfall types had different effects on the runoff and sediment yield on the slope. The rainfall duration mainly affected the runoff and sediment yield on the slope, and the average rainfall intensity mainly affected the starting time of runoff and sediment yield on the slope. (2) Under the event of rainfall, the runoff transfer of different slope lengths was an ideal equilibrium transfer mechanism, and with the increase of slope length, the transfer capacity of runoff showed a decreasing trend. Under the condition of 40~60m slope length, the transfer of sediment was a non- equilibrium transfer process. With the increase of slope length, the transfer capacity of sediment increased first and then decreased. (3) The influencing factors on flow-sediment transfer efficiency on different scale slopes were different. Runoff depth, average rainfall intensity and surface soil moisture content after rain were the main factors affecting the transfer efficiency of flow-sediment scale. [Conclusion] The runoff and sediment yield capacity of the slope in the loess hilly and gully region is affected by rainfall characteristics and slope length. There is a significant scale effect of damage or gain in the transmission of runoff and sediment along the way. The efficiency of water and sediment transport is regulated by multiple factors such as rainfall intensity, runoff and soil moisture. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to investigate the spatial and temporal changes of runoff and sediment load in the Kuye River Basin, to quantify the contribution of climate change and human activities to variation of runoff and sediment load, and to provide scientific basis for the rational use of water resources and the optimal allocation of soil and water conservation measures in the Kuye River Basin. [Methods] Based on the runoff, sediment load and rainfall data of Xinmiao, Wangdaohengta, Shenmu and Wenjiachuan hydrological stations in Kuye River Basin from 1960 to 2020, the spatial and temporal variation characteristics of runoff and sediment load were analyzed by the linear trend method, Mann-Kendall trend test and Pettitt mutation test, and the double mass curve was used to quantitatively analyze the contribution rate of climate change and human activities to runoff and sediment load variation in different periods. [Results] Annual runoff and sediment load in the Kuye River Basin showed a significant decreasing trend from 1960 to 2020 (p<0.01). The runoff reduction rates of Xinmiao, Wangdaohengta, Shenmu and Wenjiachuan hydrological stations were 2.4 million m³/a, 3.4 million m³/a, 8.1 million m³/a, 10.6 million m³/a, the reduction rates of sediment load were 0.438 million t/a, 0.693 million t/a, 1.603 million t/a and 2.721 million t/a, respectively. The annual runoff and sediment load of each hydrological station changed abruptly both in 1979 and 1996, so the runoff and sediment load sequences could be divided into the reference period (1960-1979, P1) and the change period (1980-1996, P2;1997-2020, P3). During the study period, the average annual runoff depth and sediment load modulus of different sub-basins showed a decreasing trend, but there were differences in space. [Conclusion] The increasing human activities (water conservancy and soil conservation measures, coal mining, etc.) are the dominant factors on variation of runoff and sediment load in the Kuye River Basin. Compared with the base period, the runoff and sediment load of each hydrological station decreased in both P2 and P3 periods, and reduction was more intense in P3 period. In the P2 and P3 periods, the contribution of human activities to the reduction of runoff sediment transport was higher than that of rainfall changes. [ABSTRACT FROM AUTHOR]

Floods are becoming more widely acknowledged as a common occurrence of nature's dangers on a global scale. Although forecasting models primarily focus on timely warnings, models aimed at evaluating dangerous zones can play a vital role in shaping policies for adaptation, mitigation, and reducing the risk of disasters. Using machine learning techniques including hybrid black widow optimization (BWO) with XGBoost, LGBoost, and AdaBoost. We generate a flood susceptibility map for considered region of lower mahanadi basin (LMB). This study examines the effectiveness of these machine learning models in assessing and mapping flood susceptibility, while also providing suggestions for future research in this area. Flood susceptibility model was developed using 13 variables: Altitude, Aspect, Curvature, Distance from river, Drainage Density, Stream Power Index (SPI), Sediment Transport Index (STI), Rainfall intensity, Land Use Land Cover (LULC), Topographic Wetness Index (TWI), Terrain Roughness Index (TRI), Normalized Difference Vegetation Index (NDVI), and slope. Additionally, flood inventory data were incorporated into the model. Dataset was divided into a 70% portion for training model and a 30% portion for validating model. To assess the performance of the model, several evaluation metrics were employed, including receiver operating characteristic (ROC) curve and other performance indices. Evaluation of flood susceptibility mapping, using ROC curve method in combination with flood density yielded strong and reliable results for various models. BWO‐XGBoost achieved a score of 0.889, BWO‐LGBoost achieved a score of 0.937, and BWO‐ADABoost achieved a score of 0.904. These scores indicate effectiveness of these models in accurately predicting flood susceptibility in the study area. A comparison was made with commonly used methods in flood susceptibility assessment to evaluate the efficiency of proposed models. It was found that having a first‐class and enlightening database is crucial for accurately classifying flood types in flood susceptibility mapping. This aspect greatly contributes to improving the overall performance of the model. Among the evaluated methods, the hybrid model BWO‐LGBoost demonstrated better performance compared with others, indicating its effectiveness in accurately predicting flood susceptibility. [ABSTRACT FROM AUTHOR]

High‐elevation, low‐relief continental plateaus are major topographic features and profoundly influence atmospheric circulation, sediment transport and storage, and biodiversity. Although orogenic surface‐uplift mechanisms for modern continental plateaus near known plate margins like Tibet are well‐characterized, they cannot account for examples in intracontinental settings like the Colorado Plateau. In contrast to canonical plate‐tectonic uplift mechanisms, broad‐scale hydration‐induced metasomatism of the lower crust has been suggested to reduce its density and increase its buoyancy sufficiently to contribute to isostatic uplift. However, the relationships between key petrophysical properties in these environments are not fully quantified, which limits application of this model. Here, we develop a series of petrological models that describe the petrological and topographic effects of fluid–rock interaction in non‐deforming continental crust of varying composition. We apply an open‐system petrological modelling framework that utilizes reactive‐transport calculations to determine the spatial and temporal scales over which mineralogic transformations take place compared with the magnitude of infiltration of aqueous fluids derived from devolatilization of subducting oceanic lithosphere. The buoyancy effect of hydration‐induced de‐densification is most significant for metabasic lower crust, intermediate for metapelitic crust, and minimal for granodioritic crust. We apply these results to a case study of the ~2 km‐high Colorado Plateau and demonstrate that under ideal conditions, hydration of its lower–middle crust by infiltrating aqueous fluids released by the Farallon slab during Cenozoic low‐angle subduction could have uplifted the plateau surface by a maximum of ~1 km over 16 Myr. However, realistically, although hydration likely has a measurable effect on surface tectonics, the uplift of orogenic plateaus is likely dominantly controlled by other factors, such as lithospheric delamination. [ABSTRACT FROM AUTHOR]

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

Wave-induced sheet flow leads to intense sediment transport. Fine sand and medium/coarse sand exhibit opposite directions of net sediment transport under velocity-skewed oscillatory sheet flows. A newly developed two-phase mixture model is employed to simulate the sediment transport under these conditions. The model accounts for particle stress, two-phase momentum exchange, and turbulence modulation. The effects of grain size on flow characteristics and sediment transport are primarily investigated. The model effectively reproduces the spatial and temporal distributions of two-phase velocities and sediment concentration as well as the periodic distribution of erosion depth. Comparisons between configurations with medium and fine sand demonstrate that the grain size impacts sediment transport in two main ways. First, the grain size influences the periodic variations in erosion depth and the quantity of suspended sediment. A decrease in the grain size increases the phase residual and phase lag, enhancing offshore sediment transport. Second, suspended sediments modulate the flow dynamics within the oscillatory boundary layer. Through the mobile bed effect and density stratification, the grain size affects two-phase velocities, turbulence, and net sediment transport. [ABSTRACT FROM AUTHOR]

As cross‐shelf gradients of most properties are typically much steeper than those in the alongshore direction, transport across isobaths tends to be inhibited, particularly at oceanic fronts where cross‐shelf gradients are markedly pronounced. Consequently, variations in cross‐shelf gradients may exert a significant influence on offshore transport; however, this influence is not yet well understood. This study employs reconstructed daily suspended sediment concentration (SSC) data from the Yellow Sea's offshore region to investigate the dynamics of offshore transport. Our analysis on an interannual scale shows that offshore SSC correlates more with temperature gradients at the oceanic front than with winter storms, despite the latter's vital role in causing frontal instability. The observed increase in offshore transport over the past two decades is likely connected to Kuroshio Current warming, which has strengthened the horizontal density gradient at the oceanic front, driving the strengthened offshore transport of coastal sediments during instability episodes. [ABSTRACT FROM AUTHOR]

Knowing the amount of sediment transported in rivers is important in river and hydraulic engineering. In essence, sediment transport process is very complex, whose direct measurement is not only challenging but also costly. In this regard, several equations have been developed to estimate sediment discharge, while their estimations may be an order of magnitudes different from one another under specific circumstances. In a bid to improve the estimation of sediment transport, this study proposed a new data-driven equation based on 543 reliable field measurements at 25 rivers using the Modified honey bee mating optimization (MHBMO) algorithm. The data include mean flow velocity, water surface slope, mean flow depth, median particle size, water surface width, suspended load, and bed load measured in the field. The performance of the new equation was compared to those of Yang, Engelund and Hansen, Shen and Hung, and Ackers and White using 6 metrics. Moreover, another nature-inspired optimization algorithm, i.e., genetic algorithm (GA) was employed to enhance the comparison. Based on the results, the MHBMO-based equation outperformed other estimation models and served as the best method in the ranking analysis. For instance, it improves the determination coefficient of Yang's equation, which is one of the widely-used equations recommended by the United States Bureau of Reclamation by 15.2%. Despite being ranked the second, the GA-based equation was only marginally less precise than the MHBMO-based model. Furthermore, the sensitivity analysis indicates that the sediment load is mostly sensitive to mean flow depth. Finally, it is postulated that applications of nature-inspired algorithms can help to improve the estimation of sediment transport. [ABSTRACT FROM AUTHOR]