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One of the main problems that often affect water resources management is the loss of reservoir capacity due to sediment deposition inside them. This problem is unintentionally exacerbated in some countries by inefficient management, due to the lack of economic resources to carry out the estimation of siltation using classical methods. The United Nations World Water Development Report, launched in March 2020 on the occasion of World Water Day, alerts to the chronic lack of financing for water infrastructure in the world. In the case of Mexico, investment in water infrastructure should correspond to at least 5 percent of Gross Domestic Product (GDP); however, less than 2 percent is being invested for the 2018–2024 6-year period. Therefore, this paper presents a methodology to estimate the sedimentation of water bodies using a soil erosion model MMF, a sediment trap model STEP, and the estimation of the fluxes generated by these using the methodology proposed by (Jenson and Domingue in Photogramm Eng Remote Sens 54: 1593–1600, 1988; Tarboton et al. in Hydrol Processes 5: 81–100, 1991). The results for the study area showed an effectiveness of 80% for the estimation of siltation. The average soil erosion in the watershed is low 0.2 t ha−1, the trap efficiency is about 38%, resulting in an annual sedimentation of 0.3% (1 623 000 tons year−1). This low sedimentation value is mainly due to the heterogeneity of the slopes, which does not allow the concentration of surface flows.

Banyuurip is one of the villages in Ujung Pangkah District which has potential natural resource that is mangrove forests. However, the occurrence of abrasion and conversion of mangrove land has impacted mangrove ecosystem. Rehabilitation efforts by replanting mangroves have been carried out, but they have not been effective in overcoming the current problems. The reduction of mangrove area that led the decreased of mangrove’s function can affect the livelihood of the local community, including fishermen. The installation of geosynthetic bags, which are sand-filled bags arranged on the ground, is done as an alternative solution in Banyuurip Village which functions as coastal protection and a sediment trap. The utilization of geosynthetic material is often used to help the coastal problem, the used of geosynthetic material is rarely carried out in mangrove areas. This study aims to determine the sediment characteristics, sedimentation rates, and sedimentation process based on the relationship between current velocity and sedimentation rate. The result shows that generally the type of sediment fraction in this location is silt (79,12% - 80,12%) and the rest is clay. The current installation of geosynthetic bags can result in the land extension from the trapped sediment behind the structure. In addition, the current velocity conditions and the sediment transport process also affect the sedimentation process that occurs. The average sedimentation rates around the geosynthetic bags installation area ranged from 150.72-305.01 mg.cm-2.day-1. This study may provide a basic information for further development in Banyuurip Mangrove Center and other mangrove conservation area.

The field investigation of the reservoir area of Baglihar Hydropower project shows that the sediment budget to the reservoir is controlled by fragile rock type like shales, sandstones, phyllites and slates, soil characteristics, steep hill slopes, rainfall and landslides. The rocks are highly weathered, fissile and micaceous in nature and very sensitive to water absorption. The analysed sediments are characterised by dominance of sands, silts and clays with lower values of plasticity (14.3PL), liquidity (23.5 LL), cohesion (118) and shear strength (202 Kpa). The slope wash deposits are highly susceptible to landslides and slope failures and directly contribute to the sediment budget in the reservoir. In addition tributaries of Chenab River also bring sediments in the reservoir from the catchment area. The empirical relationship for estimating the long-term reservoir trap efficiency for large storage based on correlation between the relative reservoir size and trap efficiency was simulated in 3D model which shows that the annual sediment trap efficiency of the Baglihar reservoir is of 0.39%. The extrapolation of the calculated values shows that the total sediment load shall increase by 11% in the next 30 years and 20% in the next 50 years and correspondingly 40% in the next 100 years that shall induce corresponding decrease in the reservoir volume over the time. By applying flushing schemes, life span of the reservoir can be extended. It is estimated that after 100 years the reservoir shall lose ~35.6% storage volume. On further extrapolation, the trap efficiency will decrease from 25.5% after 30 years to 23% after 100 years. The estimated trap efficiency of Baglihar reservoir is 60%, which is greater than that based on numerical results, showing a significant overestimation.

This survey is the first to explore the seasonal cycle of microbial eukaryote diversity (

Unlined pressure tunnels in sound rock, combined with pressurized sand traps at the downstream end, allow for low-cost construction of hydropower tunnel systems. This design concept is utilized in hydropower plants across the world. Currently, many such power plants are being upgraded with higher installed capacity, which may result in challenges with the sand trap efficiency. A physical scale model test, accompanied by 3D CFD simulations of a case study pressurized sand trap, has been studied for economic retrofitting. The geometric model scale is 1:36.67 while the velocity scale and sediment scale are 1:1 (same average flow velocity and sediment size in model and prototype). This is currently an uncommon scaling approach but with several advantages, as presented in this paper. Various options for retrofitting were investigated. A combined structure of ramp and ribs was found to significantly improve the sediment trap efficiency. The main novelties from this work are the proposed design of the combined ramp and rib structure. Secondary results include an efficient setup for physical scale models of pressurized sand traps and a methodology that combines the benefits of 3D CFD simulations with physical scale models testing for sand trap engineering and design.

Regularly spaced earthen mounds called heuweltjies dot landscapes of the succulent Karoo of western South Africa. Colonies of the western harvester termite, Microhodotermes viator typically occupy the mounds, but there is substantial, unresolved debate regarding the role (if any) played by the colonies in mound formation. Recent studies demonstrate the role of aeolian sediment accretion in mound formation. A system dynamics model that includes a sequence of physical and biological state transitions illustrates processes that culminate in the localized deposition of aeolian sediments in a patch occupied by a colony of M. viator. The process starts with the successful establishment of a termite colony. As the colony develops, the termites accumulate soil nutrients, creating a fertile island, which fosters localized development of denser vegetation. The vegetation patch functions as a sediment trap, accumulating greater amounts of aeolian sediments than in the surrounding, sparser vegetation. Positive feedback loops contribute to continuity of patch occupancy by termites and persistence of processes responsible for mound formation and maintenance. System behavior is dependent on exogenous environmental variables, including climate and sediment supply. This context-dependent behavior explains geographical variation in mound size and the occurrence of other physical manifestations of colonies.

Episodic floods and storm events have significantly impacted the marine sedimentary environment and hydrodynamic processes of inner–shelf regions. The influence of a storm event on the coastal sedimentary environment depends on its trajectory and intensity, making it difficult to forecast the environmental impact. We analyzed the grain size distributions and time-series of settling particulate matter during Tropical Storm Muifa by collection of settling particulate samples and surface sediment samples before and after the storm from the inner-shelf of Heini Bay, China. We determined end-member components from shallow sediment core data and sediment trap data using end-member modeling with coupled cluster analysis. The results show that this storm event increased the mean grain size of seafloor sediment due to the addition of coarser particles, but did not increase the particle size range of settling particles. These findings are confirmed by the extremely leptokurtic distribution of particle size and the single-peak at 50–53 µm, indicative of improved sorting and very positive skewing during the storm period. Furthermore, the storm carried these coarser particles into the bay, so there was a coarser sediment texture in the middle of the bay. In addition, we identified a common end-member component responding to this extreme weather event from the settling sediment particles during Tropical Storm Muifa and the nearby shallow sediment core samples. Our reconstruction of this historical extreme weather event indicated there were two sedimentary fragments that corresponded to two high-frequency periods of historical storm events. This indicates that storm events redistribute sediment in the seafloor and cause structural changes of grain size composition.

Reservoir siltation surveys facilitate the quantification of the mean area-specific sediment yield (SSY) of catchments for decadal and longer time spans. This requires information on the volume (VS) and dry bulk density (dBD) of reservoir deposits, the period of time (TR) during which they were accumulated, the reservoir sediment trap efficiency (TE) and the catchment area (A). For the calculation of the catchment-wide average rate of erosion by water (E), the sediment delivery ratio (SDR) of the catchment needs to be estimated. Each step in this workflow represents a potential source of uncertainty. Here, we explore the extent to which individual error sources contribute to uncertainties in SSY and E values. Mean SSY and E values are inferred for small to medium-sized catchments (≤100 km2) of 15 small (≤350 × 103 m3) intermittently dry reservoirs located in the southern Kruger National Park and observation periods of 30 to 65 yr. Mean relative uncertainties of resulting SSY and E values amount to ±21% and ±46% at the 95% confidence level, respectively. Uncertainties in SSY values arise mainly from the TE estimation (mean fractional uncertainty contribution of 64%), while the SDR estimation is the major cause (79%) for uncertain E values. Uncertainties in the determination of VS and dBD values are rather unimportant, contributing together

Despite the fact that dinoflagellate cysts of the diverse genus Spiniferites are abundant in coastal and estuarine sediments worldwide, little is known about patterns of their seasonal or annual pr...

Water level variation substantially affects the trophic levels in a lake. The primary objective of this research is to investigate the impact of water level fluctuation on sediment and phosphorous (P) dynamics in Tonle Sap Lake (TSL), Cambodia. Water samples were collected from eight cross sections in a lake at 3-month intervals for 3 years, during the low-water period (March and June) and high-water period (September and December) from December 2016 to June 2019. Water quality parameters—temperature, conductivity, salinity, dissolved oxygen, pH, oxidation reduction potential, chlorophyll-a (Chl-a), and blue green algae—were measured using an EXO(R) sensor. The sedimentation and resuspension rates of the sediment were measured using a sediment trap. Sediments were collected during the low-water period of March 2017. The sediment resuspension condition was simulated via centrifugation (150 rpm, end-to-end mechanical shaker, room temperature 25 °C for 24 h) to assess phosphorous dynamics. The P content in the bed sediment was fractionated to obtain loosely bound, metal oxide bound, apatite bound, and organic bound P. Sediment resuspension was greater during the low-water period ( 4.8 m). The sites exhibited significant variation (p < 0.05) in terms of dissolved oxygen, pH, oxidation–reduction potential, Chl-a, and depth during low- and high-water periods. In general, the Chl-a concentration throughout the sampling campaigns ranged between 1.7 and 9.0 μg/L, suggesting the existence of a mesotrophic state in the TSL. The zero equilibrium P concentration of sediment in TSL was greater when the sediment was under the resuspension condition (18.9 ± 3.0 μg/L) than under the static condition (7.7 ± 1.1 μg/L). In TSL, during resuspension (low-water) conditions, sediments act as a source and release P (apatite bound, loosely bound, metal oxide bound, and soluble reactive P). However, in static (high-water) conditions, sediments act as a sink by adsorbing P from the overlying water.

Anoxic sinkholes are unique geomorphological features of modern reef systems and in terms of “lake-like” sediment successions very special marine depositional environments. This study presents results of a sedimentological survey, which focuses on the “Great Blue Hole”, a circular Pleistocene karst cavity, situated in the shallow eastern lagoon of Lighthouse Reef Atoll (Belize, Central America). The investigated Blue Hole is located within the tropical cyclone belt and acts as consequence of its unique geomorphology as a giant sediment trap for both fair weather and storm sedimentation. As an important innovation step, we applied a multi-proxy approach based on textural, compositional and geochemical data to ensure a more reliable differentiation between sediments with fair weather and storm condition affiliation. Sediments having formed under both conditions were texturally categorized by determination of classical sedimentary parameters such as mean grain size and sorting. Sediment composition has been quantified in thin sections based on 40 samples discretely taken along a core from the bottom of the 125 m deep and 320 m wide cavern. Classification of sedimentary facies follows a modified scheme for unconsolidated carbonate sediments based on the Dunham nomenclature. Fair-weather sediments are generally finer than 20 μm and consist on average of 81% carbonate fine material, 12% Halimeda platelets, 3% coral fragments, 2% organic material, 1% mollusc shells, 1% foraminifer tests, and minor portions of coralline red algae and echinoderm plates (0–1%). Intercalated event bed sediments are coarse-silt to sand-sized (> 20 μm) and differ in terms of generally lower fine carbonate material amounts (50%) and increased abundances of over-washed Halimeda platelets (28%) and coral fragments (6%). Combined analyses of this study have revealed four primary sedimentary facies with affiliation either to the background (mudstone) or cyclonic event sedimentation (Halimeda wackestone, algae-rich packstone, coralgal rudstone) as well as a transitional sub-facies indicating storm-induced background overprinting (background wackestone). The striking compositional and textural differences of the Halimeda wackestone, algae-rich packstone and coralgal rudstone facies are considered to be another helpful (semi)-quantitative proxy to identify event beds of tropical cyclones in unconsolidated sinkhole sediment successions.

International audience; Paleolimnological studies are central for identifying long-term changes, yet many studies rely on bioindicators that deposit detectable subfossils in sediments, such as diatoms and cladocerans. Emerging DNA-based approaches are expanding the taxonomic diversity that can be investigated. However, as sedimentary DNA-based approaches are expanding rapidly, calibration work is required to determine the advantages and limitations of these techniques. In this study, we assessed the congruence between morphological and DNA-based approaches applied to sediment trap samples for diatoms and crustaceans using both intracellular and extracellular DNA. We also evaluated which taxa are deposited in sediment traps from the water column to identify potential paleolimnological bioindicators of environmental variations. Based on 18S rRNA gene amplicons, we developed and analyzed a micro-eukaryotic, monthly time series that spanned 3 years and was comprised of paired water column and sediment trap samples from Cultus Lake, British Columbia, Canada. Comparisons of assemblages derived from our genetic and morphological analyses using RV coefficients revealed significant correlations for diatoms, but weaker correlations for crustaceans. Intracellular DNA reads correlated more strongly with diatom morphology, while extracellular DNA reads correlated more strongly with crustacean morphology. Additional analyses of amplicon sequence variants shared between water and sediment trap samples revealed a wide diversity of taxa to study in paleolimnology, including Ciliophora, Dinoflagellata, Chytridiomycota, Chrysophyceae, and Cryptophyceae. Partial RDAs identified significant environmental predictors of these shared assemblages. Overall, our study demonstrates the effectiveness of DNA-based approaches to track community dynamics from sediment samples, an essential step for successful paleolimnological studies.

Comprehensive field observations characterizing the biological carbon pump (BCP) provide the foundation needed to constrain mechanistic models of downward particulate organic carbon (POC) flux in the ocean. Sediment traps were deployed three times during the EXport Processes in the Ocean from RemoTe Sensing campaign at Ocean Station Papa in August–September 2018. We propose a new method to correct sediment trap sample contamination by zooplankton “swimmers.” We consider the advantages of polyacrylamide gel collectors to constrain swimmer influence and estimate the magnitude of possible trap biases. Measured sediment trap fluxes of thorium-234 are compared to water column measurements to assess trap performance and estimate the possible magnitude of fluxes by vertically migrating zooplankton that bypassed traps. We found generally low fluxes of sinking POC (1.38 ± 0.77 mmol C m–2 d–1 at 100 m, n = 9) that included high and variable contributions by rare, large particles. Sinking particle sizes generally decreased between 100 and 335 m. Measured 234Th fluxes were smaller than water column 234Th fluxes by a factor of approximately 3. Much of this difference was consistent with trap undersampling of both small (1 mm) and with zooplankton active migrant fluxes. The fraction of net primary production exported below the euphotic zone (0.1% light level; Ez-ratio = 0.10 ± 0.06; ratio uncertainties are propagated from measurements with n = 7–9) was consistent with prior, late summer studies at Station P, as was the fraction of material exported to 100 m below the base of the euphotic zone (T100, 0.55 ± 0.35). While both the Ez-ratio and T100 parameters varied weekly, their product, which we interpret as overall BCP efficiency, was remarkably stable (0.055 ± 0.010), suggesting a tight coupling between production and recycling at Station P.

Formation of shoals in an estuarine environment creates significant problems such as reduction in depth in navigational channels, decreased discharges and degradation of water quality. One of the widely used solutions to reduce sedimentation is the implementation of a sediment trap by creating a trench or a pit in the submerged bottom at specific locations. A sediment trap is defined as a section of the estuarine bed deepened to a depth greater than its surroundings. The lower velocity allows sediments to deposit in the trap rather than move past over it. Implementation of a silt trap at specific locations in a highly dynamic domain like Hooghly estuary helps to optimize the dredge quantity or the maintenance dredging can be localized to a specific location (the trap) rather over a wide submerged area. This study involves optimization of the location and shape of a silt trap near the Haldi-Hooghly confluence point, West Bengal, India. The trap was designed to reduce the dredging quantity in the downstream Jellingham channel which is a part of the navigational channel en route to Haldia Dock Complex in the Hooghly estuary. Based on a comprehensive numerical study, an option of irregular polygon shaped silt trap of a surface area of 250,000 m2 positioned in such a way to trap the sediments from both the Hooghly and the Haldi rivers near the Haldia anchorage was finalized which was found to perform efficiently in reducing the dredge quantity in the Jellingham channel. The details of the study are reported in this paper.

Despite the potential importance in the oceanic carbon cycle and benthic ecosystem, global feature of lateral supply of aged organic matter hosted on lithogenic particles derived from sediment resuspension has not been systematically examined. We compiled concentrations and fluxes of lithogenic material in the ocean in a global-scale by using literature data of sediment trap studies to understand the contribution of resuspended sediment to sinking particulate matter. We find that these contributions are significant in various oceanic settings, particularly over continental margins. Lithogenic material flux decreased with increasing distance from the margins and above the seafloor. Examination of Δ14C values of sinking POC revealed strong relationships with parameters that represent contribution of resuspended sediment. We then derive estimates for the contribution of aged POC from sediment resuspension to sinking POC based on these relationships and global lithogenic material flux data.

Three-dimensional numerical modelling of the marine and fluvial dynamics of the lower Murray River demonstrate that the mid-Holocene sea-level highstand generated an extensive central basin environment extending at least 140 kilometres upstream from the river mouth and occupying the entire one to three kilometre width of the Murray Gorge. This unusually extensive, extremely low-gradient backwater environment generated by the two metre sea-level highstand captured most, if not all, of the fine-grained sediment discharged from the 1.06 million square kilometre Murray-Darling catchment. This material was sequestered within a >60 kilometre long, >10 metre thick valley-wide deposit of finely laminated mud. This previously unrecognised sediment trap persisted from 8,518 to 5,067 cal yr BP preventing sediment delivery to the marine environment. Its identification requires that mid-Holocene climate reconstructions for southeastern Australia based on fluctuations in the delivery of fine-grained sediment to the ocean offshore the lower Murray River’s mouth must be re-evaluated.

Studies of dinoflagellate cysts or ciliates in sediment traps provide essential information on weekly, monthly, seasonal, annual, and/or multi-annual changes in their fluxes in relation to measured or implied environmental parameters. Such information is essential for understanding ecological preferences of individual taxa which is the foundation for performing reliable (paleo)environmental high-resolution regional reconstructions. Up to date, sediment trap studies are rare, and only three of those deal with dinoflagellate cysts production in ice-covered conditions: in Antarctic waters (Harland and Pudsey, 1999); Arctic fjords in the Svalbard archipelago (Howe et al., 2010); and Hudson Bay (Heikkilä et al., 2016). All these studies consistently show a very limited or no cyst recovery from the samples that were collected during the ice-covered intervals. However, the timing of individual species production (e.g. cysts of Pentapharsodinium dalei, Islandinium minutum, and Spiniferites elongatus) within the ice-free condition is inconsistent as it varies from region to region. In this session, we will present our preliminary results on dinoflagellate cyst continuous bi-weekly record at the Beaufort Sea shelf break from September 2014 to August 2015.

This paper presents research on the influence of suspended sediments on selected aspects of a reservoir&rsquo, s functioning. As the amount of sediment suspended in water (SS) there was found to correlate significantly with sedimentation rate (Us), it was possible to develop a function allowing the rate of accumulation of sediments to be predicted by reference to known amounts of suspended sediment. The latter factor was also shown to correlate significantly with the content of organic matter in suspension (OMSS), in sediment captured in a sediment trap (OMS), and of bottom sediment (OMSB). Analysis of amounts of suspended sediment can provide for estimates of total loads of organic pollutants deposited in the sediments of a reservoir. A further significant correlation with SS was noted for the concentration of total phosphorus in water (TPW), confirming the importance of internal production where the circulation of this biogenic substance in a reservoir ecosystem is concerned. Analysis of stable carbon isotopes in turn showed that entrapped sediments were depleted of&mdash, or enriched in&mdash, 13C, in line with whether concentrations of total P in those sediments (TPS) were at their highest or lowest levels. This dependent relationship may thus be of key importance in assessing sources of phosphorus, as well as in forecasting concentrations present in reservoir sediments. The results obtained make it clear that sediments suspended in the water of a reservoir unify phenomena and processes ongoing there, between elements of the water-sediment system.

The Maldives archipelago acts for over 25 myrs as a giant natural sediment trap in the eastern Arabian Sea. Drifts and periplatform deposits bear the record of environmental changes such as sea-lev...

Rock-glacier sediment transfer and ice melting can impact surface waters located downstream. However, there is a lack of knowledge on the influence of rock-glacier dynamics on the geochemical, hydrochemical, and ecological characteristics of adjacent impounded surface waters. In the Col d'Olen area (Long-Term Ecological Research site, NW Italian Alps), an intact rock glacier terminates into a pond and solute-enriched waters originating from the rock glacier flow into the pond through a subsurface hydrological window. In this study, we performed geophysical and ground surface temperature measurements. Moreover, we sampled soils and sediments in different compartments of the investigated rock-glacier - pond system and we further sampled benthic invertebrates in the pond. Cold ground thermal regime, ground-ice presence, and coarse debris cover on the rock glacier together with its lithology (serpentinites) influence the rock-glacier geochemistry and ecology with respect to surrounding areas. Pond geochemistry is affected by transfer of trace-metal-enriched fine-grained debris and meltwaters from the rock glacier. Enhanced bioavailability of serpentinite-associated trace metals was proved, with concentrations of Ni and Cr in benthic invertebrates up to 384 and 110 mg kg−1 d.w., respectively, potentially exerting toxic effects on pond biota. The advancing movement of the rock glacier not only has delivered sediments to the pond, but it has progressively filled the valley depression where the pond is located, creating a dam that could have modified the level of impounded water. This process likely constituted a sediment trap in which serpentinitic rock-glacier sediments could be deposited at the pond bottom, with related geochemical and ecological implications. This study illustrates the importance of rock glaciers in influencing the characteristics of downstream freshwater bodies and highlights the need to improve our knowledge about climate-change-related impacts of rock-glacier dynamics on alpine headwaters.

A synthesis of published and newly acquired stable and radiocarbon isotope data from soil, river, and marine particulate organic carbon (OC) from the South China Sea drainage and sedimentary basin reveals that OC derived from bedrock‐erosion (petrogenic OC) and marine productivity comprises the major contributors to bulk OC in particulate matter reaching abyssal depths, while soil‐derived OC appears negligible. Aluminum‐radiocarbon relationships of sediments suggest that soil OC initially associated with detrital terrestrial minerals is lost and replaced by marine OC during transport beyond the continental shelf. We estimate that petrogenic OC sinking to a ~30,000 km2 region of the deep northeastern South China Sea accounts for 0.6% of global petrogenic OC burial. The basin‐wide OC isotope patterns coupled with sediment trap observations highlight both the spatial variabilities of OC components as they propagate from source to sedimentary sink and the significance of petrogenic OC to deep ocean sediments., Geophysical Research Letters, 45 (17), ISSN:0094-8276, ISSN:1944-8007

Yunlong Lake, a subtropical alpine lake in southwest China, was selected for a sediment trap diatom study between September 2013 and August 2015. Combining the results of meteorological records, wa...

This study examines how geochemical signals regarding the source and transformation in suspended particles are transported in the marine portion of the sediment dispersal system. In the source-to-sink sedimentary continuum of a world major river, the Changjiang (Yangtze) River, is used to demonstrate the close coupling between the marine physical processes and the geochemical signals carried by suspended particles. A sediment trap mooring configured with a non-sequential sediment trap, a downward-looking ADCP, CTD, LISST-100× were deployed for 29 days in the winter of 2014 off the coast of Zhejiang Province, China in water depth of 22.5 m. The mooring rendered two types of data. Physical processes included temporal changes of water depth, currents at 11 depths, temperature at two depths, and salinity at one depth. There was 15-cm accumulation of captured particles in the trap, which rendered the total mass flux of 233.3 g/cm2/day. The trap material was analyzed for grain-size composition, total 210Pb, minerals including mica/illite, kaolinite, chlorite, k-feldspar, plagioclase, quartz, and dolomite. Organic material (TOC, TN) and carbon isotope δ13C were also measured. The range of terrestrial fraction (Ft) of the trap material was between 45–60%. EOF analysis was used to examine the covariability in both data sets. For the physical data set, 37 variables were used in the analysis. For the sediment trap material, 15 variables were used. The EOF results of the physical processes indicate the tidal flow was the most important physical forcing for the transport of suspended particles and water masses that carried marine- and terrestrial-sourced particles. Wave and current combined resuspension entrained reworked sediment off the seabed, which was then transported landward or seaward. The most important covariability of the particle properties in the sediment trap was caused by hydrodynamic sorting that separated the clay from silt and sand sizes. Geochemical signals of the particles were carried by clay and the particle mass (dry weight) was associated with silt and sand. The temporal characteristics of the sorting show the spring-neap tidal cycle. The next major distinction was the contrast between terrestrial- and marine-sourced materials. The EOF analysis further distinguish contributions from the distal Changjiang River and proximal small rivers at the tertiary level of the covariability. The coverabilities in both data sets show close correspondence. Our findings give firm evidence to show marine processes dominated the transport of land-derived fluvial sediment and the incorporation of marine-sourced particles into the dispersal system. There is complexity in both physical processes and geochemical signals of suspended particles. However, our study points out the close coupling between the two.

Thirty-seven years post-eruption, erosion of the debris avalanche at Mount St. Helens continues to supply sediment to the Toutle-Cowlitz River system in quantities that have the potential to lower the Level of Protection (LoP) against flooding unacceptably, making this one of the most protracted gravel-bed river disasters to date. The Portland District, US Army Corps of Engineers (USACE) recently revised its long-term plan for sediment management (originally published in 1985), in order to maintain the LoP above the Congressionally-authorised level, while reducing impacts on fish currently listed under the Endangered Species Act, and minimising the overall cost of managing sediment derived from erosion at Mount St Helens. In revising the plan, the USACE drew on evidence gained from sediment monitoring, modelling and uncertainty analysis, coupled with assessment of future LoP trends under a baseline scenario (continuation of the 1985 sediment management strategy) and feasible alternatives. They applied geomorphological principles and used engineering science to develop a Phased Sediment Management Plan that allows for uncertainty concerning future sediment yields by implementing sediment management actions only as, and when, necessary. The phased plan makes best use of the potential to enhance the sediment trap efficiency and storage capacity of the existing Sediment Retention Structure (SRS) by incrementally raising its spillway and using novel hydraulic structures to build islands in the NFTR and steepen the gradient of the sediment plain upstream of the structure. Dredging is held in reserve, to be performed only when necessary to react to unexpectedly high sedimentation events or when the utility of other measures has been expended. The engineering-geomorphic principles and many of the measures in the Phased Sediment Management Plan are transferrable to other gravel-bed river disasters. The overriding message is that monitoring and adaptive management are crucial components of long-term sediment-disaster management, especially in volcanic landscapes where future sediment yields are characterised by uncertainty and natural variability.

Siltation of reservoirs is an indicator of the intensity of erosion processes and sediment yields of river catchments. An estimation of sediment yield is significant for hydroengineering practices, environmental prediction and modelling. It also reflects environmental changes in the form of climate and land use. The present study aimed to compare the amount of sediment deposited in a small reservoir in Poland, with the estimate of sediment yield from its catchment, using the Universal Soil Loss Equation coupled with a sediment delivery ratio (USLE-SDR) and an estimate of annual bed load transport, provided by a regional bed load formula. The estimate of the annual amount of bed load was based on the flow frequency graph and bed load rating curve of Skibinski. The dam of the reservoir was constructed in 1976. The first reservoir survey was carried out between 1979 and 1980, when the reservoir volume was estimated to be 252,000 m3. Subsequent surveys were carried out in 1991, 2003, 2009 and in the Spring of 2020. These surveys enabled the amount of sediment, deposited in the reservoir, to be measured across four different periods: 1980–1991, 1992–2003, 2004–2009 and 2010–2019. For the same periods, the USLE with a constant SDR (calculated using the approach provided by Vanoni) were used to estimate the quantity (mass) of suspended sediment yield from the contributing area of the catchment. The volume of suspended sediment, deposited in the reservoir, was obtained, taking into account the reservoir trap efficiency and assuming a density of suspended sediment deposits. Hydrological investigations of the Plachty gauging station on the Zagozdzonka River, the left tributary of the Vistula River, have been carried out by the Department of River Engineering at Warsaw University of Life Sciences since 1962. The catchment area at the Plachty gauging station, located just upstream of the reservoir, is 82.4 km2, whereas the catchment area above the dam of the Staw Gorny reservoir, is 91.4 km2. The estimated annual sediment yields for the catchment, based on reservoir surveys across four periods between 1980 and 2020, suggest a general decrease over time. This study was also undertaken to examine long-term variability in sediment yield, both in suspended sediment and bed load, related to rainfall-runoff erosivity, river discharge and land use changes, which could influence changes in catchment sediment yield. An analysis of local temperature and catchment runoff revealed a long-term increase in the mean annual temperature and a corresponding decrease in annual discharge. The annual values of total sediment input to the reservoir (suspended and bed load), estimated using the USLE-SDR and a bed load formula with sediment trap efficiency, are very close to the measured amounts of deposits in the reservoir. Annual deposits in the reservoir are decreasing with time. This is presumably caused by the decrease in arable land in the catchment. From the mean annual deposits in the reservoir, around 35% is bed load and 65% is suspended load. The average annual specific suspended sediment yield in the catchment, is ca. 9 Mg/km2.

Gully land consolidation (GLC) is a slope-gully reclamation program that was implemented after “Grain for Green” project on the Loess Plateau, China. Through the GLC project, the Chinese government planned to increase the area of cropland by 337.80 km2 from 2013 to 2017. To quantify the impact of GLC on runoff and sediment transport, the coupled SWAT (Soil and Water Assessment Tool) model, which was integrated with a process-based terrace algorithm, was employed in this research. The results showed that the improved SWAT model was proven to be a powerful tool for detecting the effect of GLC on flow and sediment discharge. The effect of GLC on flow and sediment loading was concentrated in the flooding period, its runoff interception efficiency was 169,350 m3/(km2·yr), and sediment trap efficiency was 3979 t/(km2·yr), showing that it had good flow and sediment reduction benefits. However, the GLC project drastically altered the water and sediment flux equilibrium, and excessive expansion was likely to lose parts of riparian-ecosystem functions of the downstream river. In view of this, we integrated the improved SWAT (embedded in the terrace module), double-mass curve and Pettitt test to identify the recommended ratio of GLC area to the total area in the Yanhe watershed. The results demonstrated that if the reclaimed gully area accounted for 0.8% (61 km2) of the total area (7608 km2), the runoff abruptly changed. Therefore, the reclaimed gully area should remain within 0.8% of the total area in the Yanhe watershed, if so, GLC not only alleviates the contradiction between agricultural development and ecological restoration, but also gives full play to its functions of reducing flood and restricting sediment transport.

Microplastics (MPs) are long-lasting anthropogenic pollutants, observed in all types of natural environments. The MPs abundance and their temporal variability in beach sands, surface waters (manta trawl), and suspended sediments (sediment trap) were assessed in Mazatlan, Mexico, a tourism destination on the northern Pacific coast, under the hypothesis that MP contamination is influenced by rainfall and population density. The MP concentrations in beach sands from urban and rural areas nearby Mazatlan (4–36 MPs m−2) and in surface waters (1.7–2.0 MPs m−3) were comparable between type of sampling sites; whereas the MP fluxes in sediment trap samples varied widely (40–782 MPs m−2 day−1) with highest values during the rainfall season. The MPs recovered were mostly white/clear (48–54%), and the prevailing shapes were fragments in beach sands and surface waters (59–80%), and fibers (75%) in suspended sediments. The synthetic polymers polypropylene, polyethylene, and polyethylene terephthalate were the most abundant in the study area.

There is a rich literature on coral reef sediments. However, this knowledge is spread among research fields, and the extent to which major sediment reservoirs and reservoir connecting processes have been quantified is unclear. We examined the literature to quantify where and how sediments have been measured on coral reefs and, thereby, identified critical knowledge gaps. In most studies, sediments in one reservoir or one sedimentary process were quantified. The measurement of water column sediments (55% of reservoir measurements) and sediment trapping rates (42% of process measurements) were over-represented. In contrast, sediments on reef substrata, and the transition of sediments from the water column to the benthos, were rarely quantified. Furthermore, only ~20% of sediment measurements were accompanied by the quantification of hydrodynamic drivers. Multidisciplinary collaborative approaches offer great promise for advancing our understanding of the connections between sediment reservoirs, and the sedimentary and hydrodynamic processes that mediate these connections.

This paper was specially written to complement the first part series published by (Nassar et al., 2019), to investigate the impact of anthropogenic changes around tidal entrances on sedimentary mass stocks in response to the successive pressures of decision-makers due to the sensitivity of the issue. The CMS package was therefore used to model coastal processes at the Bardawil Lagoon Western inlet1 and to forecast sediment-logical stocks each year such that the accumulation of sediments within the inlet can be mitigated by impeding the navigation of this inlet and by allowing water movement between sea and lake. The CMS package is based on a finite-volume approach. A CMS-Flow and CMS-Wave two steering modules have been introduced. In this analysis, unorthodox structural scenarios inside the tidal inlets were evaluated: extension of the jetties, flow-diverted wall (FDW), current deflector wall (CDW), sediment trap (ST), radial channels (RC) and lateral wide channel (LWC). Following the current posture of inlet 1, the use of CDW, ST or RC was considered to be reasonable compensation for the current dredging operation. This is mostly attributed to a lower infilling pace as well as the fewer dredging at year-end. Whereas the benefits generated from maintenance dredging can be perceived to be slightly costly, the long-term benefits of that expenditure can justify it.

The assessment of sediment yield from reservoir siltation requires knowledge of the reservoir's sediment trap efficiency (TE). Widely used approaches for the estimation of the long-term mean TE rely on the ratio of the reservoir's storage capacity (C) to its catchment size (A) or mean annual inflow (I). These approaches have been developed from a limited number of reservoirs (N ≤ 40), most of them located in temperate climate regions. Their general applicability to reservoirs receiving highly variable runoff such as in semi-arid areas has been questioned. Here, we examine the effect of ephemeral inflow on the TE of ten small (≤280 × 103 m3), intermittently dry reservoirs located in the Kruger National Park. Field work was conducted to determine the storage capacity of the reservoir basins. The frequency and magnitude of spillage events was simulated with the daily time step Pitman rainfall-runoff model. Different runoff scenarios were established to cope with uncertainties arising from the lack of runoff records and imperfect input data. Scenarios for the relationship between water and sediment discharge were created based on sediment rating curves. Taking into account uncertainties in hydrological modelling, uncertainties of mean TE estimates, calculated from all scenarios (N = 9), are moderate, ranging from ±6% to ±11% at the 95% confidence level. By comparison, estimating TE from the storage capacity to catchment area (C/A) ratio induces high uncertainty (ranges of 35% to 65%), but this uncertainty can be confined (15% to 33%) when the latter approach is combined with hydrological modelling. Established methods relying on the storage capacity to mean annual inflow (C/I) ratio most probably lead to an overestimation of the TE for the investigated reservoirs. The approach presented here may be used instead to estimate the TE of small, intermittently dry reservoirs in semi-arid climate regions.

Meridiani Planum is one of the most intensely studied regions on Mars, yet little is known about the physical properties of the deposits below those examined by the Opportunity rover. We report the detection of subsurface echoes within the Meridiani Planum deposits from data obtained by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument. The delay time between the surface and subsurface returns is indicative of materials with a real dielectric constant of 3.6 ± 0.6. The real dielectric constant is strongly modulated by bulk density. Newly derived compaction relationships for Mars indicate that the relatively low dielectric constant of the Meridiani Planum deposits is consistent with a thick layer of ice-free, porous, basaltic sand. The unique physiographic and hydrologic setting of Meridiani Planum may have provided an ideal sediment trap for eolian sands. The relatively low gravity and the cold, dry climate that has dominated Mars for billions of years may have allowed thick eolian sand deposits to remain porous and only weakly indurated. Minimally compacted sedimentary deposits may offer a possible explanation for other nonpolar region units with low apparent bulk dielectric constants.

Under certain geomorphological conditions, sandy sediments supplied to a coast may become trapped in nearshore sedimentary compartments because these are laterally confined by bedload boundaries or convergences. Where sediment supply is small or the shoreface very steep, and accommodation space as a consequence large, the trapping mechanism may be very efficient. The Tsitsikamma coast along the South African south coast is a case in point, the sediment supplied by local rivers over the past 12 ka having been trapped in a nearshore sediment wedge extending at least 5 km offshore. On the basis of high-resolution seismic surveys, the volume of the sediment wedge has been estimated at 1,354×106 m3. As 5% of this volume is considered to have been contributed by bioclastic material of marine origin, the terrestrial input would be 1,286×106 m3. This amounts to an average annual terrestrial sediment input of 0.1072×106 m3. Using a detailed sediment yield map, the modern mean annual sediment supply to the Tsitsikamma coast by local rivers has been estimated at 0.1028×106 m3. Unless coincidental, the remarkable similarity of the two values suggests that the current climatic conditions along the Tsitsikamma coast correspond to the Holocene mean. This conclusion is supported by the currently available climate data for the South African south coast.

The shoaling of the Central American Seaway (CAS) around 4.6 Ma (million years ago) is thought to have enhanced the Gulf Stream, strengthening the Atlantic Meridional Overturning Circulation and potentially influencing the evolution of Pliocene climate. Paleoclimate records indicate a buildup of heat and salt in the Caribbean and changes in the formation of North Atlantic Deep Water (NADW) associated with a major step in the shoaling of the CAS at 4.6 Ma. However, so far, direct evidence supporting an intensification of the Gulf Stream is scarce. Here we report new North Atlantic early Pliocene (5.3–3.9 Ma) records of sea surface temperature (SST) reconstructed using the U 37 K ' and TEX86 paleotemperature indices. Based on new sediment trap measurements near the study site, we suggest that in this particular region, the two paleothermometers record SST during different seasons: spring for U K 37 ' and summer for TEX86. At 4.6 and 4.2 Ma, our results indicate substantial increases in SST and salinity during summer but not spring, pointing to a significant intensification of the Gulf Stream and its extension, the North Atlantic Current, after the shoaling of the CAS. The divergence of the U 37 K ' and TEX86 temperature trends in those intervals suggests that the Gulf Stream intensification contributed to the strong North Atlantic seasonality that is observed today.

International audience; Deltaic sediments are important for biogeochemical metal cycling since they are hotspots for metal inputs. In addition, they are potential sites for diagenetic processes leading to either the burial of inorganic contaminants or their release. Diffusive fluxes of certain metals (Fe, Mn, Pb, Zn, Cu and Cd) in the sediments of the Mejerda River Delta (MRD) (Gulf of Tunis, Tunisia) were quantified by modeling the available concentration profiles in the pore water. The metals’ burial and sedimentation fluxes were also calculated using both the asymptotic concentrations of available metal profiles and sediment trap results. These fluxes were assembled with the exchange fluxes at the sedimentwater interface in order to develop complete metal transfer budgets. The results showed that budgets of Cu and Zn are almost neutral. The sediment appears tobe a good trap for iron since its average burial flux at the three studied stations is about 332.6 g m−2 year−1. Organic matter degradation, carbonate dissolution, and oxyhydroxide reduction are the main mechanisms which accelerate the release of metals associated with the suspended particle matter once they reach the pore water in the seabed.

We compiled modern and fossil relative abundance of coccolithophore species Florisphaera profunda from published and unpublished datasets, along with ocean environmental variable data from satellite remote sensing and physical measurements. The database includes relative abundances of F. profunda in sediment trap (n = 26) and core-top (n = 1258), and sediment core samples (n = 104). Downcore data covers the Last Glacial Maximum (n = 94, 24-19 ka) or the Mid-to-Late Holocene (n = 77, Data in Brief, 22 (22), ISSN:2352-3409

Submerged vanes alter sediment transport by inducing a secondary circulation without significantly compromising the conveyance capacity of the river. Here, a laboratory study is conducted to investigate whether wood logs or trunks can be used for sediment management. The effectivity of a traditional vane field is compared to set-ups with screens of stacked logs, and large individual trunks. Results indicate that all three set-ups redistribute sediment but that the trunks are least effective in inducing a secondary circulation and cause higher turbulence and drag, leading to a stronger decrease in streamwise velocity. We conclude that a field of trunks acts as a sediment trap because of a strong reduction of the streamwise velocity, without a strong secondary flow such as dominant in the other configurations. Screens of stacked logs can be successfully implemented in rivers, as they are only slightly less effective than traditional vanes. The risk of piping underneath objects and the associated scour are points of concern.

Some aspects of the life cycle of the Southern Ocean diatom Fragilariopsis kerguelensis have been investigated previously, but many of its details have not been surveyed in nature. We investigated ...

Dredging poses a potential threat to coral reefs, yet quantifying impacts is often difficult due to the large spatial footprint of potential effects and co-occurrence of other disturbances. Here we analyzed in situ monitoring data and remotely-sensed sediment plumes to assess impacts of the 2013–2015 Port of Miami dredging on corals and reef habitat. To control for contemporaneous bleaching and disease, we analyzed the spatial distribution of impacts in relation to the dredged channel. Areas closer to dredging experienced higher sediment trap accumulation, benthic sediment cover, coral burial, and coral mortality, and our spatial analyses indicate that >560,000 corals were killed within 0.5 km, with impacts likely extending over 5–10 km. The occurrence of sediment plumes explained ~60% of spatial variability in measured impacts, suggesting that remotely-sensed plumes, when properly calibrated against in situ monitoring data, can reliably estimate the magnitude and extent of dredging impacts.