Search

The potential response of shoreface depositional environments to sea level rise over the present century and beyond remains poorly understood. The shoreface is shaped by wave action across a sedimentary seabed and may aggrade or deflate depending on the balance between time-averaged wave energy and the availability and character of sediment, within the context of the inherited geological control. For embayed and accommodation-dominated coastal settings, where shoreline change is particularly sensitive to cross-shore sediment transport, whether the shoreface is a source or sink for coastal sediment during rising sea level may be a crucial determinant of future shoreline change. While simple equilibrium-based models (e.g. the Bruun Rule) are widely used in coastal risk planning practice to predict shoreline change due to sea level rise, the relevance of fundamental model assumptions to the shoreface depositional setting is often overlooked due to limited knowledge about the geomorphology of the nearshore seabed. We present high-resolution mapping of the shoreface-inner shelf in southeastern Australia from airborne lidar and vessel-based multibeam echosounder surveys, which reveals a more complex seabed than was previously known. The mapping data are used to interpret the extent, depositional character and morphodynamic state of the shoreface, by comparing the observed geomorphology to theoretical predictions from wave-driven sediment transport theory. The benefits of high-resolution seabed mapping for improving shoreline change predictions in practice are explored by comparing idealised shoreline change modelling based on our understanding of shoreface geomorphology and morphodynamics before and after the mapping exercise. [ABSTRACT FROM AUTHOR]

Sediment production at each stage of erosion and its redistribution vary at different scales in a watershed, a slope and even a plot. The preparation of sediment budgets on watershed and slope scales have been considered in the two preceding decades, and a review of this tool on a plot scale can also help to better understand the process of sediment production, redistribution and delivery. The present study was conducted to budget sediments in laboratory plots with sandy-loamy soil and under rainfall simulation with the intensities of 30, 50, 70 and 90 mm h-1. Sediment tracing was performed on the surface of the plots by measuring the changes in the density of synthetic color-contrast aggregates using image processing. The results indicated the ability of this method to prepare sediment budgets on a plot scale. The contribution of interrill erosion in sediment production was increased with an increase in the rainfall intensity; however, the proportion of sediment redistribution within the plot was decreased. The average sediment delivery ratios for the rainfall intensities of 30, 50, 70 and 90 mm h-1 were 7.30, 8.54, 11.74 and 15.64%, respectively. The insignificance of this ratio on a plot scale was emphasized due to the short period of the experiment and should be considered in laboratory research projects.

This study explores the morphological features and internal structure of small-scale washovers along the south-eastern Baltic Sea coast, providing insights into these most widespread yet often neglected deposits in the recent research of geomorphological and sedimentary record of storm surges. A 15-year-long record of morphological changes of the coast was acquired from regional orthophotos to analyse their geometry and spatial characteristics. Sedimentological analyses comprising a description of deposits, grain size and shape analyses, and Ground Penetrating Radar profiling were undertaken to investigate the internal structure of washovers. The formation of washovers appeared to be correlated with the average winter NAO (North Atlantic Oscillation) index. The study revealed different scaling relationships of selected spatial parameters in two coastal settings and extended previously hypothesized relationships of length-area, area-volume, and length-volume. The internal structure of washovers is defined by low-angle planar cross-stratification and horizontal stratification, both disrupted by small troughs. Grain-size data indicated extremely short transport of dune and beach sediments, lately deposited in the form of washovers. The study proves that in all domains, the geomorphological characteristics of washovers are scalable, despite the different coastal settings, and even small-scale washovers fit the existing development models. • Small-scale washovers fit and extend the existing geomorphological models. • Washovers tend to form and grow periodically on multiyear scale. • Georadar facies allow for identification of washovers in the sedimentary record. • Characteristics of washover deposits indicate local, short transport. [ABSTRACT FROM AUTHOR]

Coastal areas globally suffer from serious erosion and sedimentation problems. The assessment of coastal erosion risk is fundamental for better coastal management. The main goal of the current study was to enhance coastal management by identifying the coastal erosion risk and suggest possible mitigation measures. The study was developed for the Egyptian Northern Coast. MIKE 21 was used to evaluate the erosion and test the proposed measures. First, a bathymetric survey of the study area was conducted. Then the tidal data, storm surge, and global sea rise data were collected. The offshore wave data, shoreline data were compiled. And then, the different nearshore wave modeling and wave propagation were modeled. The model was calibrated using measured data in 2014 and validated using measured data in 2016. Future shoreline changes for the years 2029, 2039, and 2049 were depicted. A suitable mitigation measure was used and tested for the same years. The groins with a specific size and arrangement were tested. The main goal of the study is to find a suitable solution to protect the coast and investigate its impact on the shoreline in the next 30 years. The proposed mitigation measure minimized the coastal erosion of the study area rigorously.

This study evaluates long-term and seasonal changes of sediment budget in Lena delta based on remote sensing dataset. Since 2000 Landsat images have been applying during ice-free period, from June to September. The sediment concentration at the delta topset was compared with sediment concentrations data at the outlets of: the Main, the Olenekskaya, the Tumatskyaya, the Trofimovskaya and the Bykovskaya channels to calculate suspended sediment budget in delta. The sediment concentration was calculated based on the archive Landsat images (more than 30 images). We have estimated influence of air temperature on thermal coastal erosion and the accumulation of sediments in the river Lena's delta. The increase of the daily average air temperature from 5°С to 14°С plays critical role in the degradation of permafrost and the activation of the processes of thermal erosion and thermal denudation of the right channels coasts and this fact means that these results can help to estimate special aspects of biochemical budget of the delta. [ABSTRACT FROM AUTHOR]

For the first time, we quantified the erosional pulse around the Permian-Triassic Boundary (PTB) over an entire sedimentary basin. We selected the intracratonic Central European Basin System, which is well suited for a sediment bud get approach, because of its long-lasting subsidence and minor sediment loss to adjacent ocean basins. Our GIS-based analysis relies on basin-wide homogenised and compiled seismic, sedimentary and stratigraphic data of the Petroleum Geological Atlas of the Southern Permian Basin. We calculated sediment volumes, sediment fluxes and sedimentation rates (SR) averaged over the entire basin with an area of about 1 Mio km2 from isopach maps of different time slices including the Rotliegend, the Zechstein, the Lower, Middle and Upper Buntsandstein, the Muschelkalk as well as the Keuper. To separate chemical versus clastic sediments, we used facies maps which were interpreted and analysed according to their predominant sediment composition. The result is a 4-9 fold increase of clastic SR in the Lower Buntsandstein compared to the background from the Rotliegend until the Keuper. These rates stayed elevated until the Upper Buntsandstein. We calculated clastic SR of 37 and 28 m/Ma in the Rotliegend and Zechstein, respectively, before they rose to 120 m/Ma in the Lower Buntsandstein. The Middle and Upper Buntsandstein show clastic SR in the order of 75 m/Ma, whereas they dropped to around 13 m/Ma in the Muschelkalk and Keuper. From a review of independent sedimentary, climatic, palynological and tectonic constraints, we conclude that the detrital peak of the Buntsandstein must have been caused by the globally visible environmental perturbations at the PTB. [ABSTRACT FROM AUTHOR]

The Changjiang (i.e. the Yangtze River) debouches a huge amount of sediment to the East China Sea and exerts a significant effect on the evolution of the down‐drift Qiantang River system. This study quantitatively documents the temporal change in the import of Changjiang sand and mud to the late Quaternary Qiantang River incised valley by establishing separate mixing models based on zircon U‐Pb ages for the sand and trace‐element compositions of the mud fraction. Results indicate that the Qiantang River provided all of the sediment to its valley before ca 8.0 cal kyr bp. However, its sediment proportion decreases upward due to the onset of export of sediment from the Changjiang after its delta had prograded sufficiently. Changjiang mud, a major component (ca 87%) of the Changjiang‐derived sediment, is considered to be primarily supplied through the resuspension and landward transportation of sediment from the inner‐shelf mud wedge in the East China Sea by flood‐tidal currents and waves. Changjiang sand, which arrived in the Qiantang River valley later than the mud, is interpreted to be derived from the reworking of older deposits on the East China Sea shelf and along the northern margin of the Qiantang River estuary. In the later part of the valley fill, Qiantang River sediment is only ca 9% of the Changjiang contribution, although Qiantang River mud has begun to be exported recently. The Changjiang contribution to the Qiantang River system constitutes ca 50% of the total sediment load discharged by the Changjiang during the 8–6 cal kyr bp period, but <4% since 6 cal kyr bp. This study illustrates the need to exercise caution when interpreting compositional data from linked coastal‐shelf sediment‐dispersal systems with significant along‐coast transport, and is expected to be applicable in a general way to other linked river–coastal‐shelf systems. [ABSTRACT FROM AUTHOR]

The features of the suspended sediment load along the 200-km braided channel of the Lena River from the city of Pokrovsk to the Aldan River mouth (upstream of the Aldan braiding) are described in detail (30-m resolution) based on water-sediment concentration modeling, using the collection of Landsat images for the period of 1992–2018. It is shown that large anabranching river reaches correspond to changes of the system of sediment transport and accumulation, manifesting themselves as the predominance of the occurrences of positive (increase) or negative (decrease) ΔS0 values (where ΔS0 stands for suspended sediment-concentration budget). The conditions of a longitudinal decrease in suspended-sediment concentration along the braided reach of the Lena River are characterized by high water discharges (>20 000 m3/s) and are associated with sediment accumulation in riffles and floodplain areas. It has been revealed that a significant role in the longitudinal decrease in water-sediment concentration is played by lateral floodplain branches, which accumulate a part of the incoming suspended sediments and exert a dilution effect on the sediment flow downstream of the confluence with the main channel. Cases of a longitudinal increase in the water-suspended sediment concentration are typical for lower water flow rates (<20 000 m3/s) and are related to increased bank thermal erosion in summer and erosion of riffles during a low-water period. A combination of the grid of suspended-sediment concentration, velocities, and channel depths with a 30 × 30-m resolution (more than 20 000 cells) for low-water conditions revealed a dependence of the local suspended-sediment concentration on the transporting capacity of the flow, which was determined for particular verticals. A correspondence between the regime of certain reaches in different phases of water regime is observed. It indicates the mutual influence of the directedness of mass exchange and channel morphology. The transformation of distribution systems of suspended sediments may be interpreted as one of the self-regulation mechanisms in the channel system. Complex systems of sediment flow distribution along the channel of a large river reflect the opposite directions of erosion-accumulation processes caused by bends in the longitudinal profile. [ABSTRACT FROM AUTHOR]

Dungeness is a cuspate foreland on the south coast of England that is the largest shingle feature in Europe and includes hundreds of beach ridges. It is also the location of two nuclear power stations that were constructed in the 1960s. The dominant southwest waves cause longshore drift from west to east, eroding the southwest side of Dungeness, accompanied by accretion on the east side. A record of this eastward movement and sediment accretion is preserved by the shingle beach ridges. The power stations are located on the eroding southwestern side of the ness, and a system of beach recharge has been used to move shingle from the downdrift, east-facing shore to the updrift, southwest-facing shore to protect the power stations from coastal erosion. We use a novel combination of historic images, ground-penetrating radar (GPR), and Lidar (HIGL) to investigate accretion and beach ridges at Dungeness during the past 80 years. We report changes in accretion along the coast and use GPR to determine the thickness of beach gravels. The amount of accretion, represented by the width of the backshore, decreases downdrift from south to north. The number of beach ridges preserved also decreases from south to north. By combining the shingle thickness from GPR with elevation data from Lidar surveys and records of beach accretion measured from aerial images, we estimate the volume and mass of gravel that has accumulated at Dungeness. Historic rates of beach accretion are similar to recent rates, suggesting that the 55 years of beach recharge have had little impact on the longer-term accretion downdrift. [ABSTRACT FROM AUTHOR]

The sediment budget has been introduced as a valuable concept and tool for describing the production, transport and deposition of sediment in a watershed. In order to study the effect of slope on sediment budget, the distribution map of erosion and sedimentation of the Khamsan Representative Watershed, located in the south of the province of Kurdistan, was prepared using 137Cs and overlapping with the slope map. The results showed that 15 sub-watersheds with an average area of ​​185.39 ha and an average slope of 31.83% had a mean sediment delivery ratio of 28.43%. Increasing the area to the whole watershed (4098.66 ha without rocky outcrops) with an average slope of 25.26%, the ratio decreased to 12.63%. This finding emphasizes on the impact of internal plain with the average slope of 10.27% on sediment trapping and decrease of sediment delivery ratio by 15.8%. The results of comparing the sediment budgets in slope classes showed that an orchard, irrigated agriculture and rangeland treated with soil conservation activities, the sedimentation is a dominant condition in all the slope degrees, while almost all the erosion caused by rain fed agriculture with the slope gradient degrees of 2-20%, and the rangeland with the gradients slope of more than 30%. Therefore, it is recommended to investigate the sediment delivery ratio with an emphasis on the performance of the low-slope areas as a sediment trap before applying the check dams, if necessary, and only in the most efficient places. Also prevent the conversion of rangeland to dryland and farming, also prevent plowing in the slope direction.

Abstract Sedimentary processes and spatial distributions of tsunami deposits in valleys have poorly been understood despite many paleo-tsunami deposits have recently been discovered from sedimentary sequences in valleys. We conducted an exhaustive investigation of 2011 Tohoku-oki tsunami deposits in a narrow valley at the south end of Sendai Plain, northeastern Japan, to collect sedimentological data of the tsunami deposits in the valley and to correlate them with tsunami inundation and associated sedimentary processes. The tsunami deposits were investigated at 174 sites to cover the entire inundation area of the narrow valley. We analyzed thickness, sedimentary structures, and grain size of the tsunami deposits to correlate their spatial variation with tsunami flow hydrodynamics and topographic features. The tsunami deposits, composed of sand and mud layers, were found to be 0–40 cm thick. Sand thickness generally decreased inland with local fluctuation. The sand layer was mostly composed of single unit on the upper main valley and sub-valleys, although it was mainly composed of 2–6 sub-units on the lower main valley and in the pond. Mud thickness is strongly controlled by local sources, namely, the rice paddy and the pond. The depositional area of the mud layer coincides with the distribution of the rice paddies and the pond location. The mud layer also considerably thicker in and around the pond. These results indicate that sediment thickness and sedimentary structures are highly varied on a local scale, but they are generally controlled by local topography. Sediment budget in the valley was estimated, and it may provide implications to general sedimentary process. Total depositional volume of the tsunami sand deposited on land is half of the volume of sediments disappeared from the sandy beach and sand dune, suggesting the rest must have been discharged into the sea by the backwash. Spatial distribution of sediment thickness and sedimentary structures as well as sedimentary processes inferred from 2011 Tohoku-oki tsunami deposits will benefit searching and identification of paleo-tsunami deposits in valleys of other coastal environments.

Numerical simulation of the sediment by the Delft3d model was conducted to examine the changes in the sediment budget transport caused by long-term wave changes at the Maengbang beach. Representative waves were generated with input reduction tools using NOAA NCEP wave data for about 40 years, i.e., from January 1979 to May 2019. To determine the adequacy of the model, wave and depth changes were compared and verified using wave and depth data observed for about 23 months beginning in March 2017. As a result of the error analysis, the bias was 0.05 and the root mean square error was 0.23, which indicated that the numerical wave results were satisfactory. Also, the observed change in depth and numerical result were similar. In addition, to examine the effect due to long-term changes in the waves, the NOAA wave data classified into each of the representative wave grades, and then the annual trend of the representative wave was analyzed. After deciding the weight of each wave class considering the changed wave environment in 2100, the amounts of sedimentation, deposition, and the sediment transport budget were reviewed for the same period. The results indicated that the sedimentation pattern did not change significantly compared to the current state, and the amount of the local sediment budget shown in the present state was slightly less. And there has been a local increase in the number of sediment budget transport, but there is no significant difference in the net and amount of sediment movements.

Lena River is one of the largest “pristine” undammed river systems in the World. In the middle and low (including delta) 1500 km course of the Lena main stem river forms complex anabranching patterns which are affected by continuous permafrost, degradation of the frozen ground and changes in vegetation (taiga and tundra). This study provides a high-resolution assessment of sediment behavior along this reach. Comprehensive hydrological field studies along the anabranching channel located in the middle, low and delta courses of the Lena River were performed from 2016 to 2022 including acoustic Doppler current profiler (ADCP) discharge measurements and sediment transport estimates by gravimetric analyses of sediment concentration data and surrogate measurements (optical by turbidity meters and acoustic by ADCP techniques). These data were used to construct regional relationships between suspended sediment concentrations (SSC, mg/L), turbidity (T, NTU) and backscatter intensity (BI, dB) values applicable for the conditions of the Lena River. Further, field data sets were used to calibrate the seasonal relationships between Landsat reflectance intensities and field surface sediment concentration data. Robust empirical models were derived between the field surface sediment concentration and surface reflectance data for various hydrological seasons. Based on the integration of in situ monitoring and remote sensing data we revealed significant discrepancies in the spatial and seasonal patterns of the suspended sediment transport between various anabranching reaches of the river system. In the middle course of the Lena River, due to inundation of vegetated banks and islands, a downward decrease in sediment concentrations is observed along the anabranching channel during peak flows. Bed and lateral scour during low water seasons effects average increase in sediment load along the anabranching channels, even though a significant (up to 30%) decline in SSC occurs within the particular reaches of the main channel. Deposition patterns are typical for the secondary channels. The anabranching channel that was influenced by the largest tributaries (Aldan and Viluy) is characterized by the sediment plumes which dominate the spatial and temporal sediment distribution. Finally, in the distributary system of the Lena delta, sediment transport is mostly increased downwards, predominantly under higher discharges and along main distributary channels due to permafrost-dominated bank degradation.

The Vu Gia Thu Bon (VGTB) River basin is critical for regional development and prosperity in water resources. However, human interventions (e.g., dam construction and sand mining) have significantly affected this basin's sediment budget and morphological alterations over recent decades. Such humane actions drive an imbalance in water resources in the basin from upstream to downstream. Therefore, this study investigated spatiotemporal changes in sediment budget and morphology alterations using long-term data and bathymetric surveys; from these data, dams and sand mining contributions were quantified and differentiated. Based on field survey data and interviews, we estimated the sand-mining volume by incorporating reported and a newly proposed empirical formula. The results show that the total riverbed incision volume from 2010 to 2021 was 63.30 Mm 3 , with an incision rate of 0.14 m/yr. The officially reported sand-mining rate was 1.12 Mm 3 /yr, while the newly proposed empirical formula estimated 4.4 Mm 3 /yr. According to the developed empirical formula, the percentage reductions in the sediment budget due to sand mining and upstream dams were 69.7 % and 30.3 %, respectively, according to reports, and 17.8 % and 82.2 %. The statistical method was thus likely too conservative compared to the developed empirical formula. We found that the natural sediment supplies sourced from upstream were insufficient to compensate for the mined bed material. Therefore, our combination of different datasets permitted the assessment of future geomorphological developments within the VGTB River basin under the ongoing sediment deficits. The results of this study provide valuable insights into the impacts of human interventions, specifically sand mining, on the sediment budget, morphological alterations, and riverbed incision. The developed assessment forms the foundation for developing and expanding the region's water/sediment resource management strategies., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Deltas and estuaries worldwide face the challenge of capturing sufficient sediment to keep up with relative sea‐level rise. Knowledge about sediment pathways and fluxes is crucial to combat adverse effects on channel morphology, for example, erosion which enhances bank collapse and increasing tidal penetration. Here, we construct sediment budgets which quantify annual changes for the urbanized Rhine‐Meuse Delta of the Netherlands, a typical urban delta experiences changing fluvial and coastal fluxes of sediment, engineering works and dredging and dumping activities. The delta shows a negative sediment budget (more outgoing than incoming sediment) since the 1980s, due to anthropogenic intervention. Following a large offshore port expansion, dredging in ports and harbors in the region has doubled in the past 5 years, likely due to the induced change in net sediment fluxes. In addition, the deeper navigation channels, ports, and harbors are now trapping siltier sediment, changing the sediment composition in the mouth. The removal of sediment by dredging is adverse to the necessity for sediment in heavily eroding branches. To allow for sustainable sediment management in the future and to cope with sea‐level rise, further measurements are required to properly quantify the amount of incoming sediment at the boundaries of the system and the internal mechanisms of transport. The varied response of the branches has important consequences for navigation, ecology and flood safety and management of the sediment in the system. These effects will be of pivotal importance in coming decades with similar implications for many urbanized deltas worldwide. Plain Language Summary: Deltas need sufficient sediment to grow with sea‐level rise and counteract natural and human‐induced subsidence. A sediment budget quantifies if a delta is net gaining sediment or if it is losing sediment over a long time period. The Rhine‐Meuse Delta (RMD) has a negative budget: Its entire network of channels is losing sediment annually. The reason for this negative budget is the high amounts of sand and mud removed for navigation to inland ports and from harbors which are periodically dredged. As a result, some of the channels in the area degrade rapidly, which causes issues for river management and dynamics including water quality, flood safety, and ecology. Other deltas worldwide are managed similarly to the RMD and will therefore face the same sediment issues. A strategy is required to deal with channel degradation and find ways to maintain sediment in the system. Key Points: Human impacts on delta channels can be quantified using empirical relations between tidal prism and cross‐section area in delta channelsEstablishing sediment budgets for delta channel networks requires data concerning both sand and mud, which are jointly subject to dredgingReduced sediment input to deltas may partially be compensated for by influx of marine sediment, which is a large source of uncertainty [ABSTRACT FROM AUTHOR]

Abstract Deltas and estuaries worldwide face the challenge of capturing sufficient sediment to keep up with relative sea‐level rise. Knowledge about sediment pathways and fluxes is crucial to combat adverse effects on channel morphology, for example, erosion which enhances bank collapse and increasing tidal penetration. Here, we construct sediment budgets which quantify annual changes for the urbanized Rhine‐Meuse Delta of the Netherlands, a typical urban delta experiences changing fluvial and coastal fluxes of sediment, engineering works and dredging and dumping activities. The delta shows a negative sediment budget (more outgoing than incoming sediment) since the 1980s, due to anthropogenic intervention. Following a large offshore port expansion, dredging in ports and harbors in the region has doubled in the past 5 years, likely due to the induced change in net sediment fluxes. In addition, the deeper navigation channels, ports, and harbors are now trapping siltier sediment, changing the sediment composition in the mouth. The removal of sediment by dredging is adverse to the necessity for sediment in heavily eroding branches. To allow for sustainable sediment management in the future and to cope with sea‐level rise, further measurements are required to properly quantify the amount of incoming sediment at the boundaries of the system and the internal mechanisms of transport. The varied response of the branches has important consequences for navigation, ecology and flood safety and management of the sediment in the system. These effects will be of pivotal importance in coming decades with similar implications for many urbanized deltas worldwide.

This study discusses the potential impact of removing Posidonia banquette on the sediment budget of a siliciclastic-sediment-starved beach-barrier system. The morphology as well as the sediment volumes of this system were estimated. The banquette’s composition and sediment content were determined with samples collected during five sampling campaigns conducted in one year. The carbonate content of the system was estimated by analyzing three 1 m long cores collected along the barrier. Five digital terrain models from DGPS surveys were used to compute the beach’s average morphology to estimate the sediment volumes. The carbonate and siliciclastic sediment content from the cores were used to calculate the overall beach’s sediment mass. Total sediment mass accounted for 126,000 m3, of which ca. 86% was siliciclastic quartz sand and approximately 14% was carbonate sediment. Total banquette deposition during the year accounted for 2300 m3, with a maximum and averaged sediment content of 339 kg m3 and 78 kg m−3. A permanent loss of ca. 1.31% of total mass will occur if 5000 m3 of banquette were to be removed. In such beach settings, banquette removal may limit sediment availability, reducing the overall sediment mass and decreasing beach resilience against climate change effects such as sea level rise.

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

This paper summaries finding from a survey of Mediterranean Shoreline Change Data Infrastructure (study sites, time extents, projects, programs, data assembly points, etc.) conducted in the framework of the Medsea_Checkpoint project on behalf of EMODnet and the European Union Directorate General for Maritime Affairs and Fisheries. The main goal of the project was to identify available data on sediment mass balance at the coast at regional scale. An intensive focused research was undertaken to identify possible data sources. This research developed a dual approach: Firstly, an extensive European and research projects spatial database survey and, secondly, a scientific literature survey from scientific databases. The results from both approaches were integrated in a GIS environment and the assessment concludes: (a) contrarily to sea level o sea surface oceanography variable, there is a lack of valid data on sediment mass-balance or shoreline change (erosionaccretion) along the Mediterranean at basin level. (b) Despite there are different datasets originated from national agencies, observation systems or research projects there is a lack of comparable methods, uniform time-extent and proper spatial coverage along all the Mediterranean shores. Therefore, against Global Change Issues, and Spatial Marine Planning or Integrated Coastal Management issues, there is a need to evaluate the existing best practices related to shoreline change, in order to develop homogenous and reliable datasets that would have to use comparable and spatial temporal scales, as it is accounting for other oceanographic thematic issues such as sea level, sea temperature or fisheries among others. [ABSTRACT FROM AUTHOR]

Suspended sediment plays a critical role in riverine ecosystem health and river processes and is respondent to human alterations such as dams and increased land use. Gavins Point Dam, located on the Missouri River near Yankton, South Dakota, restricts upstream suspended load; yet, suspended sediment concentrations (SSC) increase when the river reaches Sioux City, Iowa. We determined the suspended load concentrations of seven tributaries of the Missouri River entering downstream of the dam. These data were collected from 2012 to 2019 during the summer months of May–July using a depth‐integrated sampler. Sediment rating curves were created based on discharge and SSC. We constructed a simple sediment budget, which indicated that the tributaries located in South Dakota contribute the bulk of the Missouri River's suspended load at ~80%, while the Nebraska tributaries contribute <5%. The remaining sediment is likely supplied by bank and bed erosion. Temporal changes were examined by comparing our recent measurements with historical data from USGS gaging stations on the James River and the Big Sioux River. Suspended sediment and discharge have increased by nearly an order of magnitude, potentially due to increases in precipitation and land use. Sediment budgets are useful resources for informing river management plans on a basin‐wide scale. Given the drastic, long‐term impacts of disruptions to sediment and flow regimes from dams and climate change, this research provides necessary groundwork for remediation efforts and river management. [ABSTRACT FROM AUTHOR]

The role of individual tropical cyclones in mobilizing sediment by shallow landsliding has been studied widely in islands of the Pacific but hardly within the Insular Caribbean. An opportunity to conduct such a study materialized in 2017 when Hurricane María provoked over 70,000 landslides on the island of Puerto Rico. Through aerial photo interpretation and high‐resolution digital elevation models, this study provides an estimate of the net mobilization and delivery of sediment by shallow landslides in a wet subtropical and actively cultivated 43.8 km2 watershed. Landslide mobilization and delivery are contextualized here in terms of other active sources of sediment and annual sediment delivery. Maximum hourly and 24‐h average rain intensities within the study watershed during Hurricane María were 68 and 10.2 mm h−1, respectively, and these represent intensities with local recurrence intervals of less than 10 years. However, these rain intensities were sufficient to trigger 2,318 landslides that mobilized 230,510–436,330 Megagrams of sediment, an amount that is much greater than surface erosion contributions and represents the equivalent of 0.5–3.6 years of annual watershed‐scale sediment delivery. The high susceptibility to landsliding in this region of Puerto Rico is linked to the abundance of roads (∼21 km km−2), particularly those crisscrossing terrain with slopes ranging from 30° to 60°. Only 15% of these roads are within actively cultivated areas. The remaining roads represent the support infrastructure of abandoned coffee farms that still appear to be inducing a legacy of much geomorphological and watershed management relevance. Plain Language Summary: Managing sediments is vital for many steep tropical islands where the protection of vital natural resources such as soil, water, and coral reefs is of utmost importance. Wherever rain‐driven shallow landslides are prevalent, they tend to be the dominant process releasing sediment from hillslopes and delivering them to streams. This study uses information captured as a response to Hurricane María in 2017, a tropical cyclone that had catastrophic consequences for several Caribbean islands. Aerial photographs and high‐resolution topographic data that became available for Puerto Rico after the hurricane allowed us to estimate the volume of sediment released by landslides and evaluate the factors contributing to their occurrence. Results indicate that the coffee‐growing region of Puerto Rico is very susceptible to landslides and that these landslides represent a large portion of the sediment impacting its natural resources. The high level of vulnerability to landslides is largely due to the presence of a dense road network that partly serves active farming but that is mostly within presently abandoned farms. The findings of this study imply that management strategies for this region must not only attend active cropland but also abandoned farms to effectively reduce the adverse impacts of erosion. Key Points: Landslide sediment mobilization due to a Category 4 hurricane was significant relative to surface erosion and watershed sediment deliveryAbout 77% of the total sediment mobilized by landslides originated within abandoned coffee farms presently under a secondary forest coverA dense road network supporting past and present agricultural activity makes this landscape very susceptible to landslides [ABSTRACT FROM AUTHOR]

Bedrock‐canyon rivers tend to be supply limited because they are efficient transporters of sediment and not because the upstream supply of sediment is small. A byproduct of this supply limitation is that the finer alluvium stored in these rivers has shorter residence times and smaller volumes than in alluvial rivers. To improve our understanding of disequilibrium sediment transport and its effect on sand storage in bedrock‐canyon rivers, we undertook a 20‐year study, synthesized herein, of the Colorado River in Grand Canyon. Despite the large loads for which it was renowned, this river exhibited evidence of natural sand‐supply limitation and became the perfect natural laboratory for studying sand transport in a bedrock canyon after upstream dam construction exacerbated this supply limitation. During our study, we made and analyzed an unprecedented ∼2.5 million measurements of the suspended and bed sediment. Results indicate that sand storage in this bedrock‐canyon river is self‐limiting owing to the physical controls of flow and grain size causing negative feedbacks that likely also operate in other bedrock‐canyon rivers. Following episodic tributary floods that supply finer sand, sand migrates quickly downstream in the form of a wave in which large systematic changes in bed‐sand grain size occur. These grain‐size changes cause discharge‐independent systematic changes in suspended‐sand concentration in excess of a factor of 20. Although the tributary supply of sand increases the amount of sand storage, it also greatly increases the downstream sand transport by causing bed‐sand fining, thus limiting the residence time and volume of sand storage. Plain Language Summary: Increases in flow and decreases in sand grain size interact to limit sand storage in bedrock‐canyon rivers such as the Colorado River in Grand Canyon. For a given grain size, an increase in flow (i.e., discharge) will cause a large, nonlinear increase in sand transport. Likewise, for a given flow condition, a decrease in grain size (i.e., fining of the bed‐sand grain‐size distribution) will also cause a large, nonlinear increase in sand transport. In bedrock‐canyon rivers where the bed sand is typically coarser than the sand supply, the episodic addition of sand causes temporary fining of the bed sand that produces sand‐transport increases that may be as large as those caused by typical flow increases. This grain‐size effect causes newly supplied sand to migrate downstream as sand waves, with substantial coupled changes in sand grain size occurring in the bed and in transport. Adding finer sand to a bedrock‐canyon river therefore only temporarily increases the sand storage because it also increases the downstream sand transport. Because the downstream transport of sand is increased at higher discharge, increases in flow lead to greater self‐limitation of sand storage, and therefore lesser amounts of sand in a bedrock‐canyon river like the Colorado River. Key Points: Episodically supplied sand migrates downstream in the Colorado River as a sediment wave that splits into two packets based on Rouse numberContinuous measurements are required to detect sand‐storage change in rivers with systematic discharge‐independent changes in sand transportDecreases in bed‐sand grain size following sand‐supplying events help limit sand storage in bedrock‐canyon rivers by increasing sand export [ABSTRACT FROM AUTHOR]

A sharp decline in the Sediment load at the seaward most Datong station (DTS) of the Yangtze River occurred at an average rate of 7.22 × 106 t/yr since 1956, and this drop had a staircase pattern that can be divided into five distinct periods (1956–1968, 1969–1991, 1992–2002, 2003–2012, and 2013–2017). In this study, a new holistic basin‐wide Sediment Budget Method (SBM) was developed using sediment data from a total of 74 gauging stations (arguably the largest datasets so far) to estimate the sediment contributions to DTS from tributaries and mainstream. Our results show that the Jinsha River in upper basin between Panzhihua and Xiangjiaba used to be one of the largest contributors to DTS in 1956–2002 (16%–33%), but its contribution decreased sharply after 2003 due to the impoundment of Three Gorges Dam (TGD) and decreased further to nearly nil in 2013–2017 due to the impoundment of new cascade dams (CDs) which were upstream of TGD. In contrast, the mainstream between Yichang and Datong contributed 50%–64% of the DTS in 2003–2017, owing to the active channel erosion downstream of TGD. Before 2003 about 66%–84% of the DTS was contributed by the upper reach, but 72%–91% of the DTS was from the middle‐lower reaches after 2003, reflecting a drastic shift in sediment suppliers from upper to middle‐lower reaches. On average, the drop of DTS was 128.37 × 106 t/yr due to TGD impoundment in 2003–2012 and 27.28 × 106 t/yr due to CDs impoundment in 2013–2017 because of the reservoir trapping and the inhibition of historically eroding channels in the reservoir area. This new SBM can be applied to other large and small rivers around the world to track sediment sources/sinks and provide valuable results for sediment resource management. Key Points: A new holistic basin‐wide method is developed to estimate contributions of tributaries and mainstream to the Yangtze River sediment loadThe decrease in Yangtze River sediment load shows a staircase pattern that is divided into five distinct periods from 1956 to 2017Sediment trapping and inhibited river channel erosion in the major reservoir areas are the two major causes of the sharp sediment load decline [ABSTRACT FROM AUTHOR]

We investigate the sediment routing systems of the eastern Red Sea rifted margin by constraining the sediment accumulation history of the offshore depositional domain from regional seismic sections, wells, and outcrops observations and comparing it to the denudation history of the onshore erosional domain (Arabian Shield - Delaunay et al. (2024, submitted in this issue). We show that the rift (28–16 Ma) was segmented into a northern high-relief segment (28°N-21.5°N) under marine depositional environments and a southern low-relief magmatic segment (21.5°N-13°N) under continental depositional environments. The late syn -rift (Transition period - 16-14 Ma) was associated with a decrease in the magmatic and tectonic activity of the rifted margins, marine flooding of the entire basin, and the onset of the evaporitic sequence resulting from partial isolation from the global ocean. During the early post-rift (14–5 Ma), the southern segment underwent an uplift and a significant increase of the siliciclastic accumulation (15 fold), suggesting a rapid retreat of the escarpment initially corresponding to the former rift shoulder. During the late post-rift (5–0 Ma) the siliciclastic accumulation dropped and carbonate sedimentation returned suggesting a shift towards arid climatic conditions and a slowdown in the retreat of the onshore escarpment. [ABSTRACT FROM AUTHOR]

To get a full understanding of the impacts of global change on the catchment-scale sediment balance, models are needed that combine hillslope soil erosion processes with channel morphodynamics. Here we present a modification to the SPHY-MMF model that includes a novel channel morphodynamics module, which determines erosion and deposition in rills and channels. We applied the model to a Mediterranean study area in southeast Spain, in which we show that channel erosion contributes substantially (35%–40%) to the total sediment yield, highlighting the importance of accounting for channel erosion in catchment-scale sediment budget estimations. The climate change scenarios show that the different erosional processes (i.e. sheet, rill, channel) are projected to decrease or increase, depending on the projected change in annual and extreme precipitation. From this we conclude that interactions between different erosional and depositional processes should be considered when studying the impact of global change on the catchment-scale sediment balance. [Display omitted] • We present a novel channel morphodynamics module for the SPHY-MMF model. • The new module determines erosion and deposition in rills and channels. • We assessed the impacts of land use and climate change on the sediment balance. • Channel erosion contributes substantially (35%–40%) to the catchment sediment yield. • Differences in future annual and extreme precipitation control the sediment balance. [ABSTRACT FROM AUTHOR]

Washover fans are located on small barriers in fetch‐limited micro‐tidal coastal environments in Denmark. These washover fans are formed during high‐energy storm events and we present a method to quantify their volumes and to estimate sediment exchanges between washover fans and their adjacent morphologies. We use high resolution digital terrain models (DTMs) based on light detection and ranging (LiDAR) data. We have delineated landforms using known methods of scale analysis and geomorphometric classification. We quantified volumes of the delineated landforms and estimated the related sediment budgets. These computed volumes were compared using different pre‐depositional surfaces. Finally, we assessed the sediment exchange and associated sources of sediments of the washover fans. We applied a scale analysis to determine suitable DTM resolution and focal statistics window size as input to a geomorphometric classification analysis. Landform areas and landforms were delineated using morphometric threshold values, and volumes and sediment budgets of the delineated landforms were computed using different assumptions to define the pre‐depositional surface. Resulting washover fan volumes were validated against digital elevation model (DEM) of difference (DoD) derived volumes. Sediment budgets were derived from representative volumes of the washover fans and adjacent berms. We show that quantification of washover features derived from DTMs, using geomorphometric analysis is feasible and that the presented approach provides estimates of washover deposit volumes with an accuracy between 1% and 28% compared to control volumes. © 2021 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Burrowing into riverbanks by animals transfers sediment directly into river channels and has been hypothesised to accelerate bank erosion and promote mass failure. A field monitoring study on two UK rivers invaded by signal crayfish (Pacifastacus leniusculus) assessed the impact of burrowing on bank erosion processes. Erosion pins were installed in 17 riverbanks across a gradient of crayfish burrow densities and monitored for 22 months. Bank retreat increased significantly with crayfish burrow density. At the bank scale (<6 m river length), high crayfish burrow densities were associated with accelerated bank retreat of up to 253% and more than a doubling of the area of bank collapse compared with banks without burrows. Direct sediment supply by burrowing activity contributed 0.2% and 0.6% of total sediment at the reach (1.1 km) and local bank (<6 m) scales. However, accelerated bank retreat caused by burrows contributed 12.2% and 29.8% of the total sediment supply at the reach and bank scales. Together, burrowing and the associated acceleration of retreat and collapse supplied an additional 25.4 t km−1 a−1 of floodplain sediments at one site, demonstrating the substantial impact that signal crayfish can have on fine sediment supply. For the first time, an empirical relation linking animal burrow characteristics to riverbank retreat is presented. The study adds to a small number of sediment budget studies that compare sediment fluxes driven by biotic and abiotic energy but is unique in isolating and measuring the substantial interactive effect of the acceleration of abiotic bank erosion facilitated by biotic activity. Biotic energy expended through burrowing represents an energy surcharge to the river system that can augment sediment erosion by geophysical mechanisms. [ABSTRACT FROM AUTHOR]

The landscape setting of estuaries varies widely and is an important aspect of determining how they evolve. This paper focusses on alluvial estuaries in river valleys and how they respond to sea level rise. We examine the implications of marine transgression, as a response to sea level rise, where the estuary moves upwards and landwards to maintain its position in the tidal frame (so‐called stratigraphic rollover). Here we encapsulate such kinematic movement of the estuary morphology using a 'morphokinematic' model, to assess the potential response to sea level rise and sediment supply. The model of the estuary form includes a single convergent channel, intertidal and surrounding floodplains (the valley) and allows the relative importance of the space available for deposition of sediments, the accommodation space, to be investigated as a function of rates of sea level rise and sediment supply. The transgression of the system is determined using a sediment mass balance, taking account of any supply from the river and marine environment. Model results confirm that the transgression distance, measured as the distance the entity moves landward, varies in proportion to the change in accommodation space, which mainly depends on the floodplain area. As the size of the floodplain reduces, the transgression distance is less and the system becomes much more sensitive to changes in the rate of sea level rise or changes in sediment supply. The greater demand for sediment when a floodplain is present results in greater cannibalization of the estuary form (i.e. greater landward movement) to meet the sediment demand. When the floodplain is disconnected from the estuary, the synergistic relationship is lost and the accommodation space increases. The capacity for restoration will depend on the availability of sediment and the prevailing rate of sea level rise. [ABSTRACT FROM AUTHOR]

Non-invasive techniques such as seismic investigations and high-resolution multibeam sonars immensely improved our understanding of the geomorphology and sediment regimes in both the lacustrine and the marine domain. However, only few studies provide quantifications of basin wide-sediment budgets in lakes. Here, we use the combination of high-resolution bathymetric mapping and seismic reflection data to quantify the sediment budget in an alpine lake. The new bathymetric data of Lake Brienz reveal three distinct geomorphological areas: slopes with intercalated terraces, a flat basin plain, and delta areas with subaquatic channel systems. Quasi-4D seismic reflection data allow sediment budgeting of the lake with a total sediment input of 5.54 × 106 t sediment over 15 years of which three-quarter were deposited in the basin plain. Lake Brienz yields extraordinarily high sedimentation rates of 3.0 cm/yr in the basin plain, much more than in other Swiss lakes. This can be explained by (i) its role as first sedimentary sink in a high-alpine catchment, and by (ii) its morphology with subaquatic channel-complexes allowing an efficient sediment transfer from proximal to distal areas of the lake. [ABSTRACT FROM AUTHOR]

The volume and grain‐size of sediment supplied from catchments fundamentally control basin stratigraphy. Despite their importance, few studies have constrained sediment budgets and grain‐size exported into an active rift at the basin scale. Here, we used the Corinth Rift as a natural laboratory to quantify the controls on sediment export within an active rift. In the field, we measured the hydraulic geometries, surface grain‐sizes of channel bars and full‐weighted grain‐size distributions of river sediment at the mouths of 47 catchments draining the rift (constituting 83% of the areal extent). Results show that the sediment grain‐size increases westward along the southern coast of the Gulf of Corinth, with the coarse‐fraction grain‐sizes (84th percentile of weighted grain‐size distribution) ranging from approximately 19 to 91 mm. We find that the median and coarse‐fraction of the sieved grain‐size distribution are primarily controlled by bedrock lithology, with late Quaternary uplift rates exerting a secondary control. Our results indicate that grain‐size export is primarily controlled by the input grain‐size within the catchment and subsequent abrasion during fluvial transport, both quantities that are sensitive to catchment lithology. We also demonstrate that the median and coarse‐fraction of the grain‐size distribution are predominantly transported in bedload; however, typical sand‐grade particles are transported as suspended load at bankfull conditions, suggesting disparate source‐to‐sink transit timescales for sand and gravel. Finally, we derive both a full Holocene sediment budget and a grain‐size‐specific bedload discharged into the Gulf of Corinth using the grain‐size measurements and previously published estimates of sediment fluxes and volumes. Results show that the bedload sediment budget is primarily comprised (~79%) of pebble to cobble grade (0.475–16 cm). Our results suggest that the grain‐size of sediment export at the rift scale is particularly sensitive to catchment lithology and fluvial mophodynamics, which complicates our ability to make direct inferences of tectonic and palaeoenvironmental forcing from local stratigraphic characteristics. [ABSTRACT FROM AUTHOR]

Recent developments in unmanned aerial vehicles (UAVs) have resulted in high-resolution digital elevation models (DEMs) of vulnerable coastal environments, including beach–foredune topography. If performed repetitively, they can offer an excellent tool to determine the spatial and temporal changes in the sediment budget, which may be required for proper land management. However, the quality of a UAV, slope parameters, and vegetation significantly influence DEM accuracy. The aim of this study is to compare precise GPS-RTK transects across a section of the South Baltic coast in Poland with those obtained from a DEM based on high-resolution and high-accuracy images obtained by a wind-resistant, high-quality fixed-wing UAV during beyond visual line of sight operation (BVLOS). Different land cover classes, slope inclination, and general curvature, as well as surface roughness, were taken into consideration as possible factors influencing the uncertainty. The study revealed that marram grass greatly affects the accuracy of the UAV-derived model and that the uncertainty of the UAV-derived DEM increases together with increasing slope inclination and, to a lesser degree, with increasing general slope curvature. We showed that sediment budget determinations with the use of a UAV-based DEM are correct only where grass cover is sparse, in our study, up to 20% of the area. [ABSTRACT FROM AUTHOR]

Abstract Lakes, as key recorders of sedimentation regime variations, have undergone dramatic erosion/deposition worldwide in response to global warming and increasing anthropogenic interference. Poyang Lake, China's largest freshwater lake, has not escaped these variations. Herein, we show that the sedimentation in Poyang Lake has likely undergone a unique phase shift from sediment sink (annually storing 421 × 104 t) during 1960–1999 to sediment source (yearly losing 782 × 104 t) during 2000–2012, with respect to the Changjiang (Yangtze) River. In comparison with sedimentation during 1960–1999, Poyang Lake sedimentation during the period 2000–2012 is characterized by no deposition during the flood season and enhanced erosion during the dry season. Furthermore, Poyang Lake's largest delta, the Ganjiang Delta, prograded at a rate of 32.7 m/a from 1983 to 1996, which increased to 52.8 m/a from 1996 to 2005 but dropped significantly to 1.7 m/a from 2005 to 2015. A sediment core collected in the shallow‐water shoal of the central lake indicates a stable increase in sedimentation flux from 1960 to 2002, with a mean value of 0.27 g/(cm2·a), followed by a decline in sedimentation flux after 2002. Our findings show that the tributary sediment input from the lake catchment dominated the sedimentation of Poyang Lake prior to 2000, when it was significantly larger than the sediment output to the Changjiang River. However, thereafter, the contribution of tributary sediment to the output dropped by 50%, and the rest has been provided by the lake itself. Namely, channels along Poyang Lake's waterway became the additional source of the lake's sediment output in the 2000s.

Satellite imagery and climate change projections improve our ability to map and forecast sediment sources and transport pathways at high resolution, which is vital for catchment management. Detailed assessment of temporal and spatial changes in erosion risk are key to forecasting pollutant dispersal, which affects water treatment costs and ecology. Outputs from scenario modeling of the River Derwent catchment, Yorkshire, indicate clear spatial and temporal trends in erosion risk. These trends are not picked up by using traditional methods, which rely on static land use maps. Using satellite-derived maps show that lower resolution traditional land-use maps relatively underestimate erosion risk in terms of location of source areas and seasonal variation in erosion risk. Seasonal variation in agricultural practices can be assessed by incorporating bare land variation into models, which show that erosion risk is relatively overestimated if all agricultural land is assumed to have the same character. Producing seasonal land use maps also allows the assessment of temporal variation in rainfall, which in combination with climate change projections allows for adaptable management plans. The bias in gradient in modeling, which assumes that high gradients result in greater sediment erosion risk, show that traditional models underestimate the contribution of erosion risk in lowland areas. This is compounded by the absence of artificial drainages in topographic rasters, which increases connectivity in lowland areas. By producing end member scenarios, model outputs help to inform where catchment management should be targeted, and whether seasonal interventions should be implemented. This information is vital to communicate with landowners when they implement catchment management practices, such as sediment traps and earth bunds. Adaption of erosion risk modeling practices is urgently needed in order to quantify the impact of artificial interference in which human activity disrupts ‘natural’ sediment source-to sink configurations, such as integrating new pathways and stores due to land use change and management. Furthermore, integrating higher resolution catchment modeling and improved seasonal forecasts of pollutant flux to oceans will permit more effective interventions. This paper highlights single output erosion risk maps are not effective to inform catchment management.

Examples of sediment budgets are needed to document the range of budget types and their controls. Sediment budgets for three small agricultural catchments (7.6 to 15.6 km2) in southwestern Australia are dominated by channel and gully erosion, with sheet and rill erosion playing a subordinate role. Erosion was increased by clearing naturally swampy valley floors and hillslopes for agriculture and grazing, and episodic intense rainstorms. The proportion of sediment from channel and gully erosion in the sediment budget appears to be determined by the depth of alluvial fills. Dryland salinization caused by clearing native vegetation has connected hillslopes to channels across narrow floodplains, increasing the Sediment Delivery Ratio (SDR). Yield and SDR are found to be insensitive to major in-catchment changes of vegetation cover after initial clearing, the ratio of sheet and rill erosion/channel and gully erosion, and sediment storage masses. This supports the idea that yield alone is often a poor indicator of the impact of land use and land management change. Riparian vegetation would reduce sediment yield but not phosphorus yield. This study demonstrates the value of mixed methods where field observations and chemical analysis are combined with information from local people.

Dungeness is a cuspate foreland on the south coast of England that is the largest shingle feature in Europe and includes hundreds of beach ridges. It is also the location of two nuclear power stations that were constructed in the 1960s. The dominant southwest waves cause longshore drift from west to east, eroding the southwest side of Dungeness, accompanied by accretion on the east side. A record of this eastward movement and sediment accretion is preserved by the shingle beach ridges. The power stations are located on the eroding southwestern side of the ness, and a system of beach recharge has been used to move shingle from the downdrift, east-facing shore to the updrift, southwest-facing shore to protect the power stations from coastal erosion. We use a novel combination of historic images, ground-penetrating radar (GPR), and Lidar (HIGL) to investigate accretion and beach ridges at Dungeness during the past 80 years. We report changes in accretion along the coast and use GPR to determine the thickness of beach gravels. The amount of accretion, represented by the width of the backshore, decreases downdrift from south to north. The number of beach ridges preserved also decreases from south to north. By combining the shingle thickness from GPR with elevation data from Lidar surveys and records of beach accretion measured from aerial images, we estimate the volume and mass of gravel that has accumulated at Dungeness. Historic rates of beach accretion are similar to recent rates, suggesting that the 55 years of beach recharge have had little impact on the longer-term accretion downdrift.

This paper presents the history and evolution of the different projects carried out from 1999 to 2008 at Cavo beach in the Elba Island, Italy. The village of Cavo almost completely lost its beach in the 1970s due to the reduction of sedimentary input, and the backing coastal road was defended by a revetment and two detached breakwaters. Such severe erosion processes continued in the following years and impeded any possibility of beach tourist development. In 1999, a project based on the removal of existing breakwaters and beach nourishment works based on the use of gravel as borrow sediment and the construction of two short groins to maintain nourished sediment, raised environmental concern and did not find the approval of the stakeholders. They were worried about the characteristics of the sediments, i.e., waste materials from iron mining rich in red silt and clay. Such sediment fractions made the sea red during the nourishment and deposited on the Posidonia oceanica meadow in front of the beach, with a potential environmental impact. Furthermore, they cemented the gravel fraction forming a beach rock. Between 2006 and 2008, these materials were covered with better quality gravel, extending and raising the beach profile, which required the elevation and lengthening of the two existing groins. Beach evolution monitoring following the second project, based on morphological and sedimentological data acquired before, during and after the works, demonstrated the great stability of the newly created beach. The wider beach has allowed the construction of a promenade and the positioning, in summer, of small structures useful for seaside tourism, increasing the appeal of this village. Data presented in this paper shows an interesting study case, since few examples exist in international literature regarding gravel nourishment projects monitoring and evolution.

The present marine Baltic Sea basin (BSB) occupies an eroded Proterozoic intra-cratonic basin on the Fennoscandian shield. Competing models propose a Neogene fluvial origin, with later modification by glacial erosion, or a much younger development, with overdeepening beneath the Fennoscandian Ice Sheet (FIS). We test these alternatives using a first order source to sink sediment budget for the catchment of the BSB. Best estimates derived from geomorphic and cosmogenic nuclide evidence suggest depths of erosion over the last 1 Ma of 20 m in basement and 40 m in sedimentary rocks that surround the BSB. As the BSB has been overdeepened below a regional base level provided by the shallow Darss Sill at the boundary with the Kattegat, erosion of the BSB may be interpreted as glacial in origin, without a fluvial component. The estimated total volume of source area erosion is 30,628 km3 of which 87% is derived from the present BSB. Sediment volumes in the sink area within the limits of maximum Pleistocene glaciation are estimated at a minimum of 37,629 km3, after correction for local erosion, porosity, and carbonate losses. Marine Isotope Stage 12 and younger sediments account for 87% of the total Pleistocene sediment volume in the sink in Poland. Although significant uncertainties remain, the sediment budget is consistent with erosion of the BSB entirely by the FIS, mainly when the ice sheet reached its maximum extent and thickness during the Middle and Late Pleistocene glaciations. [ABSTRACT FROM AUTHOR]

Purpose: The sediment dynamics of (peri-)glacial catchments can be highly variable and complex. Understanding these dynamics and their underlying causes is not only of interest from a scientific perspective but also required to address the practical problems with which they are often associated. In order to better understand the sediment dynamics of glaciated mountainous catchments, suspended sediment fluxes in the 9.1 km2 Djankuat catchment (North Caucasus, Russia) were monitored intensively during the 2017 ablation season. Materials and methods: The intra-event suspended sediment dynamics were studied using a newly proposed simple hysteresis index (SHI), quantifying to what extent evolutions in sediment concentration are characterized by a clockwise or anticlockwise hysteresis loop. Results and discussion: The resulting catchment suspended sediment yield was 1033 t km−2 year−1, with the glacier itself contributing 72% of the suspended sediment load. However, during rainfall events, also hillslope erosion in the proglacial area became a very significant sediment source. Clockwise hysteresis loops occurred in 61.8% of the events, while anticlockwise in 11.8%. On the other hand, only 47.8% of the total suspended sediment flux was transported during clockwise events. Our observations clearly indicate that events showing a stronger clockwise pattern (i.e., a higher SHI) are associated with a larger sediment input from the proglacial area. Conclusions: Overall, our results provide data and insights on sediment dynamics in an understudied environment. They illustrate that the type and characteristics of sediment concentration hysteresis loops are to some extent linked to the dominant sediment sources during the event. As such, the proposed methodology and SHI may also help with a better understanding of sediment dynamics in other environments. [ABSTRACT FROM AUTHOR]

Sediment budget and sediment availability are direct metrics for evaluating the resilience of coastal bays to sea‐level rise (SLR). Here we use a high‐resolution numerical model of a tidally dominated marsh‐lagoon system to explore feedbacks between SLR and sediment dynamics. SLR augments tidal prism and inundation depth, facilitating sediment deposition on the marsh platform. At the same time, our results indicate that SLR enhances ebb‐dominated currents and increases sediment resuspension, reducing the sediment‐trapping capacity of tidal flats and bays and leading to a negative sediment budget for the entire system. This bimodal distribution of sediments budget trajectories will have a profound impact on the morphology of coastal bays, increasing the difference in elevation between salt marshes and tidal flats and potentially affecting intertidal ecosystems. Our results also clearly indicate that landforms lower with respect to the tidal frame are more affected by SLR than salt marshes. Key Points: SLR increases sediment deposition on the marsh platform but reduces the sediment‐trapping capacity of tidal flats and baysFor a given SLR the increase of bottom sediments resuspended and exported out of the system is more significant for sand than mud fractionLandforms lower with respect to the tidal frame are more affected by SLR than salt marshes [ABSTRACT FROM AUTHOR]

Psuty, N.P.; Ames, K.; Liu, G., and Habeck, A., 2020. Interactive geomorphological resilience of sediment pathways and coastal features, post-Hurricane Sandy, Fort Tilden, New York. Journal of Coastal Research, 36(4), 694–708. Coconut Creek (Florida), ISSN 0749-0208. Geomorphological resilience is an essential concept in dynamic coastal systems, incorporating the recovery and regeneration of the dune/beach system and the interaction between these systems, anthropogenic forces, and ecological factors. Recovery of the coastal geomorphological system at the Fort Tilden site after Hurricane Sandy was influenced by the wooden bulkhead and the variety of groins interacting with the sediment budget. Monitoring of the recovery revealed that the alongshore coastal dune/beach system response (one-dimensional, two-dimensional, and three-dimensional metrics) was strongly related to the 11 groin sectors and that the total volume losses increased downdrift. Hurricane Sandy resulted in a general inland displacement of the dune feature along the entire site, mean of –32 m, and a landward displacement of the shoreline, mean of –3 m. There was a volumetric loss of 81,000 m3; 29,000 m3 of this was from the dune feature. Post-Sandy to Fall 2018, the dune was displaced 2 m seaward and had a volumetric gain of 10,580 m3. Comparison of the dune displacement and sediment budget metric indicated that through the six-year recovery period, the dune feature was accumulating sediment but that it was not shifting seaward to its former position despite updrift beach nourishment totaling ∼3,180,000 m3 in the period 2010–18. The inland displacement and retention of the beach-dune system under a negative sediment budget is consistent with geomorphological theory, indicating a geomorphological resilience to rebuild while shifting inland. Accordingly, the former position of Shore Road along Fort Tilden is deemed unsuitable for reconstruction in place because of increased exposure in the Post-Sandy environment. [ABSTRACT FROM AUTHOR]

The rapid uplift of the Tibetan plateau, the intense movement of the Ailao Shan-Red River Shear Zone (ARSZ), and the related climate change during the Cenozoic Indo-Asian collision have been widely studied; however, their timings varied considerably due to different data and methods used. As these events have been documented in the Red River sediment that came from the eastern Tibetan plateau and the Red River region and eventually deposited in the offshore Yinggehai and Qiongdongnan basins, here these events can be explored by calculating and analysing the Red River sediment budget, especially in the Qiongdongnan basin based on dense seismic profiles and wells. Results show that the Red River sediment mainly accumulated in the Yinggehai basin and the west part of the Qiongdongnan basin, and there are three sedimentary accumulation peaks in the Red River sediment budget during ~29.5–21, ~15.5–10.5, and ~5.5–0 Ma. By further comparing with previous studies on the timings of these events, it is inferred that the first sedimentary peak, prior to the onset of the monsoon intensification (~22 Ma), was probably driven by an intense left-lateral movement of the ARSZ in ~29.5–21 Ma. The second peak (~15.5–10.5 Ma), however, reflects a rapid uplift of the Tibetan plateau after the cessation of the left-lateral strike slip of the ARSZ. The third peak (~5.5–0 Ma) is most likely linked with a right-lateral movement of the ARSZ and the related climate change. Overall, the Red River sediment budget from the offshore Yinggehai and Qiongdongnan basins provides an important constraint on the timings of these tectonic events as well as the related climate change during the Cenozoic Indo-Asian collision. [ABSTRACT FROM AUTHOR]