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• Hydrological and erosive response at event scale for a recently burned catchment. • Comparison of two hydrological models, OpenLISEM and MOHID Land. • Parametrization based on variation in boundary conditions characterizing each event. • Models performance revealed the importance of subsurface flow at event scale. • Ash and sediment movement during large event needs different model parameterization. Wildfires are a source of instability for the natural water cycle in forested watersheds, endangering the water quantity and quality reaching downstream water bodies. The faster hydrological response of a burned area leads to increased runoff and transport of sediment and ash particles during and after rainfall events. Therefore, the use of an adequate spatiotemporal resolution in hydrological models is necessary to properly estimate post-fire impacts. Especially when addressing hydrological events such as flash floods and debris flows, which are highly unpredictable and are characterized by short duration and high impact outside the burned area. This study aims to compare the ability of two hydrological models to simulate the hydrological response and sediment transport during the first year after a fire to ultimately understand which one would best serve as a post-fire hydrological predicting tool at event scale. To achieve this goal, OpenLISEM, an event-based hydrological model, and MOHID Land, a continuous model with variable timestep, were compared. Driven by several limitations identified in previous modeling exercises at this scale during the calibration phase, this work performed a parametrization through the variation in boundary conditions characterizing each event. OpenLISEM and MOHID Land models exhibited similar capabilities in simulating runoff during the first post-fire year. However, the larger erosion input parameters required by MOHID Land increase the complexity of erosion prediction and increase equifinality. In addition, MOHID Land limited capacity to perform sensitivity and uncertainty analyses emerged as a major disadvantage, hindering the assessment of the reliability of the model's predictions. Despite its limitations for not integrating subsurface flow and base flow, OpenLISEM is the most suitable model for assessing post-fire impacts on runoff and sediment production at the event scale, because of its ease of implementation and its reduced computational requirements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Distribution of vegetation avoided erosion in China increased by 12.89% in 1990–2020. • Greening of the surface has significantly prevented soil and water loss. • Spatial distribution roughly conforms to the division of the Hu Huanyong line. • Surface greening promotes a increase in vegetation avoided erosion efficiency. Global surface greening is very important to slow down regional warming, promote ecological balance and sustainable development, and China has made a significant contribution to this in the past 30 years, and effectively alleviated environmental problems such as land degradation, water shortage and air pollution by rapidly increasing vegetation coverage. Previous studies have shown that vegetation plays a positive role in alleviating soil erosion, but there is no quantitative description of runoff erosion and sediment transport under vegetation evolution with long time series and high resolution in China area. In this study, we use the RUSLE model and multi-source satellite remote sensing data to simulate overland soil erosion in China from 1990 to 2020 and analyze both the temporal and spatial variation of vegetation avoided erosion (VAE) and its correlation with multiple driving factors, such as Gross Primary Production (GPP). The results show that: 1)The distribution has increased by 12.89 % from 1990 to 2020, which is significant, and indicates that greening of the surface has significantly prevented soil and water loss;2)The spatial correlation strength of VAE-GPP in China is roughly in line with the division of the Hu Huanyong line (Hu-line), which is the result of the combined effect of vegetation distribution and human activities;3)The efficiency of VAE was significantly improved, especially the forest, accounting for about 76.50 % of the total, which was twice the sum of the other types. The research conclusion is of great significance to soil erosion prevention and control, soil ecological improvement, vegetation dynamic planning and regional sustainable development. [ABSTRACT FROM AUTHOR]

• Human interventions affect the dynamics of meandering channels. • Unusual inner bank erosion and outer bank deposition occurred due to upstream damming. • Altered flow-sediment regimes and channel boundary drive the unusual meander dynamics. Human activities, such as reservoir construction and bank revetment, significantly alter downstream flow and sediment regimes and river channel changes, impacting river ecosystem services. However, our understanding of how intense human activities affect morphodynamics of meandering channels in big river systems remains incomplete due to the lack of high-resolution in-situ data. Here, we use comprehensive data encompassing hydrology and sediment, historical channel maps, and high-resolution river bathymetry to investigate the evolution of meandering bends in the Middle Yangtze River (MYR) across three distinct phases: the natural period (1490–1975), the bank revetment period (1975–2002), and the post-dam period (2003–2018). The study revealed that, in the absence of human intervention, the meandering channels of the MYR naturally experienced inner bank deposition and outer bank erosion, largely governed by curvature-induced secondary flow patterns in flow and sediment transport mode. In 1975–2002, outer-bank revetments reduced erodibility, stabilizing outer banks, while inner banks continued to experience lateral and vertical deposition, causing a narrower and deeper channel hydraulic geometry. Conversely, meandering bends had exhibited an unusual pattern of 'outer bank deposition and inner bank erosion' in 2003–2018. Channel morphological changes characterized by channel incision and widening were driven by changes from erodible bank boundaries to solidified bank boundaries, substantial reduction in suspended sediment concentration, and an altered and extended effective flow range (10,000–25,000 m3/s). Our findings highlight that human interventions such as damming and bank revetments can alter the conventional erosion–deposition morphodynamics of meandering bends in large river systems, carrying vital implications for sustainable river management in the Anthropocene. [ABSTRACT FROM AUTHOR]

• A new 2D meshless bedload sediment transport model is developed based on ESPH. • A formulation for calculating the time step size for an HLLC Riemann solver in a weakly coupled approach is proposed. • The simulated results based on the developed 2D ESPH-SW-BST model show good agreement with the measured results. • A particle configuration of eight interacting particles can yield more accurate predictions of erosion peaks in cases with significant lateral flow effects. A 2D Eulerian meshless bedload sediment transport model is developed using smoothed particle hydrodynamics (SPH) to simulate rapidly varied flows over mobile beds. In the developed model, we adopt a weakly coupled numerical approach to explicitly solve the governing equations, including 2D shallow water equations for fluid flow motion and the Exner equation for bed sediment movement at the same time step. A defined virtual bedload velocity in a weakly coupled approach is involved in the calculation of time step sizes. However, nonphysical virtual bedload velocities, which often occur in cases with nearly flat beds, require extremely small time step sizes. A formulation of the lower and upper bounds of information propagation speeds for an HLLC approximate Riemann solver is thus proposed to remedy the problem. Four case studies involving dam break flows in prismatic and erodible channels, knickpoint migration, dam erosion due to overtopping flow and dam-break flow in an erodible channel with an abrupt expansion are adopted to validate the developed model. In addition, to compare the performances of different particle interaction configurations under Cartesian uniform particle arrangements, four and eight interacting particles are obtained by changing the smoothing length. Against the measured results, the case of eight interacting particles shows more accurate predictions of erosion peaks along the measured cross-sections because the lateral flows are significant. The good agreement between the simulated and measured results shows that the developed 2D Eulerian SPH bedload sediment transport model with eight interacting particles is well suited for simulating complicated flow-induced bed erosion. [ABSTRACT FROM AUTHOR]

• SY and Sr of the SL was the largest, but the sediment MWD was the smallest. • Change in the flow discharge did not affect the distribution pattern of sediment particles. • Dynamic coupling of runoff hydraulics and EG morphology drove soil loss. • SDR was the most direct influencing factor on the Sr in EGs. Ephemeral gully (EG) erosion represents the early stage of large-scale gully (locally named as "Benggang") development on Ultisols in the granite hilly area. However, the EG erosion process and the mechanism underlying sediment production have not been fully elucidated. In this study, a series of field scouring experiments were conducted under different flow discharge levels (10, 15, 20, 25, and 30 L·min−1), and the primary EGs in three typical soil layers with different weathering degrees (red soil layer (RL), transition layer (TL), and sandy layer (SL)) was dynamically monitored. The results indicated that the ratio of width to depth of the EGs rapidly decreased as the flow discharge increased. At 30 L·min−1, the average sediment yield and transport rate (Sr) of the SL were 4.85 and 5.39 times, greater than those of the RL, respectively. The sediment particles were concentrated within the 1–2 mm particle size range, accounting for over 35 %. In addition, the mean weight diameter of the sediment particles in the RL was the largest. The sediment distribution characteristics did not respond to flow changes but were affected by EG morphological changes. With increasing flow discharge, the flow shear stress and stream power increased. Further analysis revealed that the coupling effect of flow hydraulic characteristics and EG morphological evolution drove the EG erosion sediment production process, and the Sr of the SL was highly sensitive to flow discharge changes. The soil disintegration rate was an internal factor that directly affected soil loss in the EGs, with a path coefficient of 0.71. The bulk density, organic matter content, and sand content were all indirect influencing factors. The RL exhibited greater anti-erodibility than the other layers and could serve as an effective protective layer for granite hilly areas. These findings provide a theoretical basis for improving soil loss management systems. [ABSTRACT FROM AUTHOR]

• It is essential to utilize diverse sources of observational data for the validation of long-term morphological simulations. • The multiple underlayer settings of the Delft3D model enable its acquisition of decadal bed layer stratigraphy. • Wind and waves sort sediment based on grain size, smoothing out morphological changes induced by tides. • Sea level rise significantly influences regions characterized by intricate morphological features. • Radial sand ridges form under a radial regime with low tidal ellipticity, abundant sand, and minor cohesive sediment. The tidal sand ridges in the southwestern Yellow Sea are unique in the world characterized by radial morphology, significantly higher elevation above low water level, and fine-grained sediment deposits. Using a numerical model, we examined the morphological evolution of the radial sand ridge system from 1979 to 2059. The model was calibrated and validated using hydrodynamic and sediment transport data, seabed topography, and grain size distributions from sediment cores. Our findings reveal that tidal force is the primary driver of the ridges' evolution, and they will continue to expand in response to sediment supply from the abandoned Yellow River delta and the Yangtze delta, with the latter contributing more. The ridges are mainly composed of fine sand and mud, with finer sediment dominating in the north and coarser sediment dominating in the south. Wind and waves sort sediment, depositing sand on ridges and fine sediment in channels, leading to erosion of higher elevated lands and filling of deep channels. Sea-level rise increases regional erosion, which has a large impact on areas with complex morphology. The 500-year morphological evolution of sand ridge systems, simulated through an idealized model, illustrated that the formation of radial sand ridges is dependent upon specific conditions such as the radial tidal regime, sufficient sediment sand, and the presence of cohesive sediment. This study deepens our understanding of the long-term prediction of coastal morphology and interpretation of seabed stratigraphy, and offers insights for effective coastal management. [ABSTRACT FROM AUTHOR]

Water erosion, a notorious major threat to food security and ecosystem sustainability, is strongly conditioned by spatial and temporal scale effects. This paper systematically reviews the scale issues in runoff and sediment delivery (SIRSD) as a research field by integrating the traditional review approach and bibliometric analysis. This review summarises SIRSD's roots and the scale effect on runoff and sediment delivery. Then, we provide quantitative insights into the SIRSD domain's development history, thematic structure, geographic distribution, international cooperation, and methodologies. Findings show that: i) SIRSD arises from the gap between the non-linearity of runoff and sediment delivery across scales and our ability to measure it. Point-based and short-term measurements cannot capture the non-linearities from the spatio-temporal heterogeneities and cross-scale interactions of factors or processes. ii) Previous literature provides evidence that the spatial scaling of specific runoff (r), soil erosion (SE), sediment yield (SSY), or sediment delivery ratio (SDR) with drainage area (A) or slope length (L) exhibits contrasting patterns due to distinct mechanisms. Infiltration-excess and saturation-excess processes account for inverse and positive r - A relations, respectively. Interrill-erosion and rill-erosion cause inverse and positive SE-L relations. Hillslope-erosion and channel/bank-erosion explain inverse and positive SSY-A relations. Downstream increasing deposition and additional sediment inputs drive inverse and positive SDR-A relations. These scaling relationships can be nonlinear or complex due to spatial heterogeneities in land use, vegetation, topography, climate, lithology, and soil characteristics. Hence, applying an empirical scaling equation developed from the region with distinct environmental contexts is not recommended. Furthermore, the existing scaling patterns or equations may require updating given global climate and land use change. iii) SIRSD is a complex and multidisciplinary issue investigated by scientists from 93 countries since 1928. International research has substantially facilitated the understanding of SIRSD; still, more collaboration should focus on less-developed countries with high soil and water loss risks and urgent conservation needs, such as those in Africa and South America under cropland expansion. iv) Scale mismatch and scale break have discredited large-scale erosion and sediment assessments. Incorporating gully and bank erosion into modelling, extending the scale range of the L factor, and expanding the sediment scaling scope from watershed to slope may make a difference. Therefore, more research with nested design incorporating multiple scales is necessary for cross-scale analysis and scalable modelling. Addressing global climate change requires improving real-time urban flood forecasting and integrating downscaled climate models with hydrology, erosion, and sediment transport models. • A bibliometric review of the global SIRSD research for the first time. • SIRSD is rooted in the gap between natural nonlinearity and our measuring ability. • Scaling of specific runoff, erosion, sediment yield, and SDR has diverse patterns. • Scale mismatch and scale break discredit large-scale modelling and assessments. [ABSTRACT FROM AUTHOR]

Sand waves are found on shallow, sandy seabeds throughout the world and their dynamics may pose an imminent threat to offshore construction. Therefore, there is a pressing need to understand bed level dynamics in sand wave areas. These bed level dynamics lead to variations in sand wave shape and migration rate over time. However, these variations cannot be explained with the present-day process-based sand wave models, which all include a purely periodic tidal forcing. To explain these fluctuations a more intricate description of the hydrodynamics is necessary. The aim of this study is to explore the importance of time-varying, non-tidal currents for sand wave dynamics in the North Sea. We adopted the three-dimensional Delft3D-Flexible Mesh model, and were able to reconstruct time-varying, non-tidal currents on top of the periodic tidal forcing, while significantly reducing computation times. The simulated currents and water levels showed a good agreement with in-situ measurements. Compared to the situation with only tidal forcing, the simulated sedimentation and erosion rates were amplified up to 15 times due to time-varying, non-tidal currents. Additionally, periods of net erosion were found at locations in the sand wave transect where tidally forced models only showed net-sedimentation. It is therefore important to consider time-varying, non-tidal currents when predicting future sand wave dynamics in the field. • The reproduction of observed hydrodynamics is improved significantly compared to previous sand wave modelling approaches. • Effects of time-varying, non-tidal currents on sediment transport in sand wave fields are quantified. • Net sedimentation rates due to time-varying, non-tidal currents are be up to 15 times larger than the tidally induced rates. • First application of Delft3D FM software to study sand wave dynamics leads to a significant decrease in computation time. • Excluding time-varying, non-tidal currents can lead to underestimation of sand wave migration and trench infill rates. [ABSTRACT FROM AUTHOR]

• A strong signal of reduced winter conditions i.e. duration, snow accumulation and frost days. • Hydroclimatic regime shift alters the sediment flux seasonality in near future. • Thaw-seasons have important role controlling the annual sediment flux. Climate change alters high latitude hydrological cycle by diminishing the snow accumulation and spring flood magnitude, and by altering temperature and rainfall finally leading to hydroclimatic regime shift from snow-dominated to rain-dominated. These changes in temperature, precipitation patterns, and discharge strongly influence geomorphological processes in fluvial environments, leading to alterations in sediment transport, erosion, accumulation, and landscape changes. We conducted comprehensive analysis of hydroclimatic trends and shifts on boreal Oulanka River system, spanning over the past five decades. A strong signal of warming temperatures (+0.61 Celsius/decade), reduced winter conditions and warmer summers (+0.41 Celsius/decade) was detected. The spring flood magnitude diminished 7 %, but high discharge peaks (Q > annual p90m3/s) during other seasons increased 22 % together with 28 % increase of annual minimum discharge. Simultaneously, precipitation intensity increased during summer. The meander migration rate (mean 0.89 or 2.55 m/year) and bank erosion volume were interconnected to ground frost, high snow sum, high discharge, and high-water level during spring flood, but no significant long-term trends were observed. Our findings underscore that climate is the first-order control on fluvial geomorphology and emphasizes the complex interplay between various hydrological and climatic factors that shape the dynamics of river systems. Based on the results, we expect to see changes in the spatial–temporal distribution of high latitude rivers sediment flux in future. In addition, more attention should be addressed to the thaw seasons controlling the sediment transport, as majority of the observed shifts took place in these months. [ABSTRACT FROM AUTHOR]

Secondary airflow occurs when the primary flow interacts with obstacles and other roughness elements such as dense vegetation. It is characterised by the deviation of the wind velocity and direction from the primary flow. Secondary airflow is often manifested as a reversing, separation, horseshoe, or deflection vortex flow, which is fully developed where the curvature of the topography changes abruptly, such as near the crest region of an aeolian dune, the edge of an escarpment, or around buildings. Secondary airflow has been proven to be one of the main driving forces for the formation of obstacle-related bedforms, such as echo dunes, climbing dunes, cliff-top dunes, falling dunes, shadow dunes, foredunes, blowouts, and parabolic dunes. Morphologies of these obstacle-related dunes have been extensively investigated, whereas the factors controlling secondary airflow and their effects on sediment erosion, transport, and deposition have been less mentioned. Here, we review the types and characteristics of secondary airflow and the controlling factors of their patterns, such as the shape and spatial alignment of obstacles and the incident flow angle. We also investigate the effects of these controlling factors on the morphodynamics of obstacle-related bedforms. As confirmed by field observations, the wind-blown sand hazards controlled by the secondary airflow are discussed. Finally, we summarize the scales of the secondary airflow, and highlight the possible focus for future investigation. • Secondary airflow has been proven to be one of the main driving forces for the formation of obstacle-related bedforms. • Secondary airflow patterns and occurrence of the associated landforms are scale-dependent. • Secondary airflow is the main driving force for wind-blown sand hazards for desert infrastructures. [ABSTRACT FROM AUTHOR]

Submarine canyons serve as important sediment transport conduits from littoral zones to the deep sea, with strong impacts on the sedimentation patterns in marginal areas of the ocean. Moreover, such canyons can be major geohazards for submarine infrastructure, warranting a good understanding of their past and current behavior. Here, we present a study of the geological history and the recent activity of the Nahariya submarine canyon, the longest of a system of ∼15 small blind canyons located in the eastern Mediterranean Sea, offshore Israel. Two piston cores retrieved from the middle and outlet of the canyon, at 650 m and 915 m water depth, respectively, were the focus of a multi-proxy study aiming to characterize sediment transport and deposition along the canyon during the Last Glacial and up to the present. Both cores reveal a sequence of homogenous sediment of late last glacial age, which are capped by an unconformity overlying by fine laminated sediment dated to the last ∼200 years. Thus, the deglacial and most of the Holocene intervals are absent from the record. Evidence for down canyon sediment transport are abundant and include a 70 cm interval of mud clasts with disordered glacial ages that appears immediately below the hiatus, as well as broken calcareous shells of dead benthic foraminiferal species of shallow marine habitats, which are abundant throughout both cores. Similarly, shelf-derived living benthic foraminiferal species were found in the core-tops, indicating that active sediment transport persists along this canyon today. We conclude that the history of Nahariya submarine canyon includes a period of sediment accumulation that lasted until the last deglaciation. Thereafter, the canyon was dominated by an erosive regime that persisted throughout the Holocene. Sediment accumulation resumed ∼200 years ago. We suggest that the recent resumption of sediment-accumulation is a result of anthropogenic amplification of on-land soil erosion accompanied by a wet period that persisted in the region and enhanced land to sea sediment transport. • The geological history of a blind submarine canyon of E. Mediterranean is studied. • In-canyon last glacial sediment accumulation and Holocene erosion are observed. • Resumption of sediment accumulation occurred ca. 200 years ago. • This resumption reflects anthropogenic on-land soil erosion and shift to wet climate. • Shelf origin sediment is transported to deep canyon during glacial period and recent. [ABSTRACT FROM AUTHOR]

Storms and extremely energetic events may significantly impact the form and structure of beaches, and so cause erosive processes and coastal damages. Efficient management actions require an up-to-date and accurate knowledge of beach morphological changes, with the shoreline position being a good indicator of such changes. This work proposes the use of the open-source Shoreline Analysis and Extraction Tool (SAET) software for the definition of satellite-derived shorelines (SDSs) from L8 and Sentinel-2 imagery to reveal the shoreline position changes at the beaches of the Ebro Delta, NE Spain. Spatial-temporal models (STMs) of shoreline changes enable a characterisation of how the beaches responded to the storms of 2020. In conjunction with wave data, STMs enable an analysis of the erosive response to storm events, as well as a monitoring of subsequent beach recovery in the short and medium term (<1 year). Results show how Storm Gloria (January 2020, Hs max = 7.62 m) acted as a disruptive event and shifting point in the shoreline trend. As a response to that storm, major erosive processes occurred along the delta that caused an average shoreline retreat of 47 m. A progressive recovery during the spring and summer was mainly associated with periods of low wave energy. Nevertheless, by the end of the year a complete recovery had been achieved for about half of the coast, while the other half showed an average erosion of more than 10 m when compared to the pre-storm situation. Both the erosive and the recovery processes took place unevenly on different sections of the coast, probably dependent on factors such as the orientation of the beach and the pattern of longitudinal sediment transport along the coast. • Automatic shoreline extraction from Sentinel 2 and Landsat 8 imagery using SAET. • Pre and post-storm characterisation of SDS position in time and space using STMs. • Storm Gloria (January 2020) caused an unprecedented and heterogeneous impact on the Ebro Delta. • Slow recovery occurred in the months following the event conditioned by orientation and wave patterns. • About half of the delta showed a significant shoreline retreat by the end of 2020. [ABSTRACT FROM AUTHOR]

Quantitative predictions of marine and aeolian sediment transport in the nearshore–beach–dune system are important for designing Nature-Based Solutions (NBS) in coastal environments. To quantify the impact of the marine-aeolian interactions on shaping NBS, we present a framework coupling three existing process-based models: Delft3D Flexible Mesh, SWAN and AeoLiS. This framework facilitates the continuous exchange of bed levels, water levels and wave properties between numerical models focussing on the aeolian and marine domain. The coupled model is used to simulate the morphodynamic evolution of the Sand Engine mega-nourishment. Results display good agreement with the observed aeolian and marine volumetric developments, showing similar marine-driven erosion from the main peninsula and aeolian-driven infilling of the dune lake. To estimate the magnitude of the interactions between aeolian and marine processes, a comparison between the simulated morphological development by the coupled and stand-alone models was made. This comparison shows that aeolian sediment transport to the foredune, i.e. 214,000 m3 over 5 years, extracts sediment from the marine domain. As a result, the alongshore redistribution of sediment from the main peninsula by marine-driven processes decreased by 70,000 m3, representing 1.7% of the total marine-driven dispersion. From the aeolian perspective, marine-driven deposition and erosion reshape the cross-shore profile, controlling the supply-limited aeolian sediment transport and the magnitude of sediment deposition in the foredunes. In the region with persistent accretion along the Sand Engine's southern flank, a higher than average foredune deposition was predicted due to morphological development of the region where sediment is picked up by aeolian transport. Including these marine processes in the coupled model resulted in an increase of 1.3% in foredune growth in year 1 and up to 6.7% in year 5 along this accretive section. At the northern flank, where the developing lagoon and tidal channel provided increased shelter to the supratidal beach, predicted foredune deposition reduced up to −11.5% over the evaluation period. Our findings show that both aeolian and marine transports impact reshaping the nourished sand, where developments in one domain affect the other. The study findings echo that the interplay between aeolian- and marine-driven morphodynamics could play a relevant role when predicting sandy NBS. • Predicting nearshore–dune morphodynamics is enabled with a new 2D coupling framework. • The model reproduces the Sand Engine's dynamics in both marine and aeolian domains. • Alongshore varying marine sediment transport influences foredune growth patterns. • Marine alongshore transport is slightly reduced by aeolian transport into the dunes. [ABSTRACT FROM AUTHOR]

Vegetation and biological soil crust (biocrust) cover can have a stabilizing effect on dunes by fixing sediment in-place and increasing surface roughness, thus limiting dune mobility, sediment transport, and erosion. These biological effects influence rates of aeolian activity and thus surficial changes, though variability in wind and sediment supply may obscure these topographic effects. In this study, we compare monthly measures of sediment transport and decadal estimates of dune mobility to repeat topographic changes measured as a net volume change in sediment storage (difference in volume between all positive and negative topographic changes) and total volume change (absolute summed volume of all positive and negative changes) for areas of bare, vegetated, and biocrusted sand within a dunefield with limited sediment supply and unimodal winds. We found that monthly net volume changes normalized by area were similar between bare sand and sand with at least 20 % vegetation cover. However, total volume change was significantly greater for bare sand and correlated with monthly sediment flux estimates (R2 = 0.46), though the relationship was significantly improved by including monthly changes in surface roughness (R2 = 0.8). Longer-term decadal trends in topographic change showed larger total volume changes with the greatest decreases in vegetation canopy cover. Additionally, decadal total volume changes strongly correlated with estimates of dune mobility (R2 = 0.99). We also found that increased total volume changes did not necessarily signal increased net volume changes for all land cover types. Specifically, increases in total volume change for bare sand resulted in near equal or lower net volume changes, as both positive (deposition) and negative (erosion) change increased with sediment transport. Conversely, less mobile land covers, such as biocrust covered sand, increased in erosion without significant increases in total volume change, demonstrating that more stable surfaces might exhibit a larger topographic change imbalance than mobile sediment surfaces under the same conditions. This study highlights the importance of considering multiple measures of topographic change for interpreting sediment mobility, transport, and availability. Additionally, we hypothesize a novel framework for remote sensing-based empirical studies aimed at interpreting aeolian landscape evolution resulting from climate change effects on weather as well as biological controls such as vegetation and biocrusts. • Total and net volume changes demonstrate complexity of partially stable dunefields. • Total volume changes were highest for bare sand, correlating with sand transport. • Biological cover reduced correlations between surface changes and transport. • Net volume changes related to sediment availability but not transport or mobility. [ABSTRACT FROM AUTHOR]

• Contour currents with different physical natures observed over a drift-moat system • High SSC on the drift due to long-range sediment transport by contour currents • High SSC in the moat due to moat wall erosion by tidal-induced secondary flows • Formation of drifts forced by upslope sediment transport of tidal currents Contourite drifts are ubiquitous sedimentary features in the world′s oceans, and their formation are usually ascribed to sedimentation from contour currents. However, in-situ observations of contour currents and their associated sedimentary processes were inadequate. Here, we present mooring observation results from a drift-moat contourite system in the South China Sea to gain insight into its sediment dynamics and formation mechanism. We found that quasi-persistent contour currents develop in the moat, on and below the drift, yet subject to diverse physical oceanographic processes. High suspended sediment concentrations observed on the drift mainly occur in winter, induced by high levels of sediments transported by contour currents from Taiwan. In the moat, however, high suspended sediment concentrations are mostly caused by erosion of the moat wall during periods of strong tidal currents and low shear variance. Such results underscore the complexity of current patterns and sedimentary processes across various topographic units in the drift-moat contourite system. A novel formation mechanism of the contourite drift is thereby proposed, wherein sediment transport by contour currents brings materials for constructing the drift, while its formation is driven by near-critical reflection and upslope transport of sediments by tidal currents. [ABSTRACT FROM AUTHOR]

• The runoff, sediment load and runoff erosion power decreased significantly. • Compared with runoff, runoff erosion power-sediment relationship is better. • The power function of runoff erosion power and sediment is better than linear. • Erosion in particular geographic locations responds strongly to runoff erosion power. In recent years, the acceleration of urbanization in the Yangtze River Economic Belt (YREB) has brought about problems such as soil erosion, ecosystem degradation and decline in ecological service functions. Therefore, this paper selects the Fujiang River Basin (FRB) in Upper Yangtze River (UYR), and analyzes the relationship between runoff erosion power (REP) and sediment transport (ST) on the basis of analyzing the variation characteristics of hydrological elements. Based on SWAT model, a variety of scenarios are set up to quantitatively analyze the impact of different land use changes on runoff and ST and REP in the basin. The results indicated that: (1) The annual precipitation in FRB from 1960 to 2018 did not change significantly, while the annual runoff, annual ST and annual REP decreased significantly. Compared with runoff and runoff depth, the relationship between sediment transport modulus (STM) and REP is the best, especially the power function between them is better than the linear function. (2) The results of the evaluation indexes of the simulation results of the SWAT model based on the measured runoff and sediment data from 2008 to 2018 are pass and above, that is, the simulation results are considered reliable. (3) Under the five scenarios of conversion of sloping farmland to forest, conversion of dry land to paddy field and conversion of grassland to bushland and forest land, the runoff and ST in the basin decreased but the overall range was small. The simulation results of SWAT model show that the erosion of specific areas in the basin shows the greatest degree of weakening with the decrease of REP. [ABSTRACT FROM AUTHOR]

Estuarine deltas play a critical role in the interaction between the ocean and land and serve as the primary location for the deposition of terrestrial organic carbon and pollutants. However, many deltas are increasingly at risk of erosion due to natural processes and human activities. In particular, abandoned estuarine deltas are extremely prone to erosion in the absence of sediment replenishment. The erosion of sediment in these deltas is crucial in comprehending the evolution of delta erosion as it directly impacts coastal geomorphology, ecological environments, geochemical cycling, and carbon sequestration dynamics. Therefore, determining accurately the erosion characteristics of estuarine deltaic sediments is essential for assessing and managing these evolving coastal systems. Therefore, this study conducted erosion experiments on undisturbed sediment samples collected from the subaqueous delta of the abandoned Yellow River Estuary (Old Qingshuigou Estuary) utilizing the UMCES-Gust Erosion Microcosm System. The aim was to reveal the spatial distribution characteristics of sediment erodibility and explore the erosion process, characteristics, and influencing factors of the surface sediments in the area. Erosion characteristics exhibited a spatial distribution pattern of increased erodibility in nearshore sediment and reduced erodibility in offshore sediments. The critical erosion shear stress of surface sediments ranged from 0.2 to 0.68 N/m2, while the erosion rate increased linearly with an increase in erosion shear stress and reached a maximum value of 2.119 g/m2 s, suggesting that nearshore sediments exhibited strong erodibility. Furthermore, the erosion characteristics exhibited a strong correlation with the type of sediment. Silt exhibited surface erosion and Type I erosion (depth-limited erosion), whereas silty sand primarily underwent volume erosion and Type II erosion (steady-state erosion). Particle size characteristics played a crucial role in influencing erosion. Additionally, our results revealed that the effective particle size of sediment aggregates and the scale effect of turbulence were also important factors that affected sediment erosion characteristics. These findings not only enhance our understanding of the erosion characteristics of silty sediments but also provide valuable parameters for sediment transport models in large river deltas such as the Yellow River Delta, thus facilitating the release of buried organic carbon and heavy metals from estuaries. • The subaqueous delta of the abandoned Yellow River Estuary sediments were assessed. • UMCES-Gust Erosion Microcosm System was employed for erosion experiments. • Sediment erodibility distribution and erosion process characteristics were analyzed. • Particle size characteristics represented the most important influencing factors. • Erosion characteristics were closely related to the sediment type. [ABSTRACT FROM AUTHOR]

The implementation of check dams serves as a crucial measure in mitigating debris flow events, effectively stabilizing sediments and diminishing the magnitude of such occurrences. However, less attention has been paid to the fact that intact check dams also promote the release of sediment downstream, and the sediment control mechanism of the check dam during debris flow has not been clearly elucidated. In this study, according to the field survey data of the typical check dam and its surrounding sediment in Chutou Gully, several numerical flume models are built to explore the variation of the fluid kinetic energy and sediment alteration under the different channel gradients and different check dam setting patterns. An improved evaluation index for sediment transport of the check dam, DEI total , is put forward to evaluate the sediment control efficiency of the established flume models. The results show the influence range of the check dam can be generally divided into positive and negative regions. The positive regions effectively intercept sediment, while the negative regions enhance the fluid erosion on sediment and promote the release of sediment. Both the positive and negative regions of the check dam are affected by the channel gradient and dam height. In addition, with the increase in sediment diameter, the resistance of sediment to fluid erosion is significantly improved. • A detail investigation of the typical check dam and the surrounding sediment are presented. • An improved evaluation index is constructed and used to assess the check dam effect on sediment. • The control mechanism of the check dam on sediment during the debris flows were revealed. • We discussed the arrangement suggestion of the check dam resisting debris flows in gullies. [ABSTRACT FROM AUTHOR]

Literature review reveals that many erosion models have limitations for application to constructed landforms. The new EroCA model aims to address this gap. The model uses established erosion and sediment transport models applied to multiple particle size classes at fine spatial and temporal resolutions, covering both suspended load and bedload. Using data from an experimental plot in Northern Australia, global sensitivity analysis was used to investigate the sources of uncertainty, limitations of the model, and priorities for data collection. Further analysis explored sensitivity to model grid size. The results showed that the Manning roughness, erodibility parameters and particle size are the most important parameters. Results also showed low parameter identifiability and hence the difficulty of calibration, even when using high quality experimental data. EroCA has the capacity to be a powerful landform modelling tool at appropriate scales of application; however ideally its data needs would be considered during monitoring design. • In-depth attempt to develop and assess a high spatial resolution process-based erosion model for a mined landform. • Improved understanding of the effects of various parameters on soil erosion process and modelling. • New insight into the limitations of experimental plot data sets for supporting high resolution erosion models. [ABSTRACT FROM AUTHOR]

• Overlapping crater populations constrain the total era of martian valley formation. • Martian valleys may have formed intermittently over hundreds of millions of years. • Long-term erosion rates would have been similar to the modern Atacama Desert. A number of studies have constrained the cessation of martian valley network activity to around the Noachian-Hesperian boundary, but the total time period over which these features formed remains poorly constrained. Most attempts to ascertain valley network formative timescales rely on an intermittency factor that varies widely for terrestrial rivers and is unknown for Mars. In this contribution, superposition relationships are used to identify crater populations that pre- and postdate valley network incision, resulting in maximum cumulative valley formation times of ∼108 years. These timescales correspond with long-term erosion rates of ∼0.25 m/Myr, similar to those calculated for the Middle to Late Noachian as well as the central Atacama Desert since the Late Miocene. Assuming sediment transport rates previously calculated for other martian valley networks, this implies a minimum fluvial intermittency of ∼10−5, several orders of magnitude lower than modern day Earth rivers but similar to values independently calculated for some martian fluvial deposits. This low intermittency suggests that martian valley incision may have been significantly hindered by erosion into existing bedrock or by boulder armoring of the valley floor. Alternatively, unlike river valleys on Earth, runoff events driving martian valley network activity may have been non-seasonal, Milankovitch-like cycles, with long eras of quiescence between periods of intensified fluvial activity. [ABSTRACT FROM AUTHOR]

• (234U/238U) were analyzed for the Changjiang estuary sediments. • Catchment erosion was revealed by sediment comminution age. • Climate changes play a leading role in catchment erosion. • Human activities changed the natural erosion processes since the late Holocene. Catchment erosion not only plays an important role on landscape evolution, but also determines the exposure of rock debris in the regolith profile, and therefore impacts the chemical weathering and associated CO 2 absorption and ultimately global climate. But climate also modulates erosion and complex interaction loops, especially at large scale can hamper a clear understanding of these processes. Here we mainly use Uranium-series Comminution Age (t com) of core sediments from Changjiang estuary to reconstruct the catchment erosion, and the relationship with climate changes and human activities during the last 14 kyrs. Since 14 ka, the sea level has been rising continuously until current highstand system tract in the East China Sea where the Changjiang estuary is located. The sediments in the Changjiang estuary mainly come from the upper reaches erosion zone during this period, but the sediment supply from the middle and lower reaches has gradually increased since the Late Holocene. The period can be divided into two modes. The first mode happens from the Bølling-Allerød period to the Mid-Holocene when the sea level rose rapidly, and the t com of sediment recorded the residence time in the upper reaches erosion zone, with a periodic pattern of t com in a good agreement with climate changes. During the cold and dry periods, the longer t com (average 460 kyrs) is consistent with less precipitation resulting in shallower erosion with transported material mainly coming from the soil with longer residence time. In contrast, during the warm and wet periods, the t com is shorter (average 290 kyrs), with the more abundant precipitations that contribute to deeper erosion in the upper catchment, and more fresh material transported to the estuary through stronger hydrodynamic forces. The second mode is more chaotic and corresponds to 0 to 4 ka, when climate was warm and humid and stable sea level, but t com fluctuated from 200 kyrs to 650 kyrs. The increasing river flooding caused by abundant precipitation leads to lateral migration of the river channel in the middle and lower reaches, and the sediments deposited in the floodplain were eroded and mobilized again. In addition, the rapid development of human activities since 2 ka has accelerated deforestation and agricultural cultivation, leading to localized erosion of the floodplain. These remobilized sediments were transported to the estuary and deposited, resulting in a larger t com value. This study overall indicates that, in the millennial scale, the t com of fine detrital fraction shows a sensitive and quick response to catchment erosion, and provides new insights into quantifying the time scale of sediment source to sink processes and inferring the paleoenvironment accurately climate changes. [ABSTRACT FROM AUTHOR]

Coastal zones are dynamic environments where sediment transport significantly influences erosion, deposition, and ecosystem stability. Accurate modelling of the complex interactions between hydrodynamics, sediment transport, and morphological changes in high-energy shoreface areas is crucial for sustainable coastal management. This study aims to assess sediment dynamics and understand the dominant physical drivers of sediment transport in the shoreface by coupling high-resolution numerical modelling with a shoreface sand tracer experiment. Results from the field experiment showed high diffusion and a net onshore and downdrift movement of the tracer in agreement with the observed hydrodynamic data. The numerical modelling strategy, validated with in situ hydrodynamic data and tracer results, demonstrated good performance and highlighted the dominant modes of shoreface sediment transport. While during low energetic wave conditions, the dominant transport mechanism involves the slow-rate bed load sediment movement toward the shore, under moderate energetic wave conditions, longshore wave-induced suspended transport becomes the prevailing mode of transport. The study provides valuable insights to increase the understanding of sediment transport in the shoreface and highlights the importance of coupling numerical modelling with sediment tracer experiments. • Field observations and numerical modelling are used to understand sediment transport in the shoreface • Conceptual sediment dynamic model combines Lagrangian and Eulerian approaches • Energetic wave conditions increase wave-induced currents and sediment transport rates, with waves breaking over the bar crest. • Streaming and wave nonlinearities are the main drivers of sediment transport in the shoreface • Alongshore suspended transport dominates in the surf zone, distributing sediments downdrift [ABSTRACT FROM AUTHOR]

Storm surge, a major disaster in coastal areas, is generated by tropical cyclones. Strong currents and waves during storm surges often cause sediment transport and beach erosion, significantly damaging the coastal ecosystem. This paper presents a flow-wave-sediment-morphodynamic coupled model to predict morphodynamic changes caused by overwash during storm surges. In the model, the flow field is calculated using the generalized shallow water equations coupled with the Simulating Waves Nearshore (SWAN) model, while sediment transport and bed changes are computed using a non-equilibrium total-load sediment transport model. The model solves the governing equations by employing the explicit finite-volume approach based on a rectangular mesh. The Godunov-type central upwind scheme is adopted to calculate the interface fluxes, thereby solving the complex Riemann problem. A series of numerical experiments considering wave-induced longshore current and short-term bed erosion are conducted to validate the established model and demonstrate its ability to simulate waves, flow fields, and bed changes during storm surge. Specifically, we used the model to simulate the morphological evolution of the Santa Rosa barrier island caused by Hurricane Ivan's storm surge, and the results indicate that the model accurately predicts the real-case erosion process caused by storm surge and overwash during the hurricane. The simulated results clearly explain overwash development, including washover fans, foredune erosion, and back-barrier deposition. It demonstrates that the front dune significantly eroded with the Santa Rosa barrier island coastline retreating by a maximum of about 80 m during the storm surge. More than three breaches with a width of up to 135 m were formed on the sandy barrier due to wave overwash, while the topography at the breach changed significantly. • A new flow-wave-sediment-morphodynamic coupled model is developed to predict morphodynamic changes caused by overwash during storm surges. • A series of numerical experiments conducted using the new model demonstrates its ability and it successfully predicts the overwash erosion of the Santa Rosa barrier island during Hurricane Ivan's storm surge. [ABSTRACT FROM AUTHOR]

• Mass movement is an important erosion mode and sediment source in gully network. • Mass movement increased sediment concentration and led to peak sediment concentration. • Mass movement was prone to be triggered by rainfall with a medium-duration and moderate-intensity. • Rainfall amount and slope gradiet determined the trigger and total volume of mass movement. Mass movement erosion on the gully sidewalls is recognized as an important erosion mode and sediment source in hilly and gully watersheds. However, the trigger of mass movement erosion and transport of gravity-detached material remain poorly understood. A series of rainfall simulation experiments were conducted on six loess gully sidewall models, with a height (1 m), three rainfall (60 mm, 48 mm and 24 mm) and two slope gradients (70° and 80°), to quantitatively explore the sensitivity factor and transport mechanisms of mass movement. Results revealed that the accumulation volume and initiation of the mass failure were significantly influenced by rainfall amount. The accumulative volume of failure events was observed to increase in a linear pattern with increasing rainfall amount. The minimum cumulative rainfalls for the initiation of mass failure on the loess gully sidewalls were approximately 43.6, 28.2 and 65.6 mm for short-duration and high-intensity, medium-duration and moderate-intensity and short-duration and moderate-intensity rainfalls, respectively. This implied that the initiation of mass failure was more prone to rainfall events with a medium-duration and moderate-intensity than those with a high intensity and short duration. Rainfall amount and initial slope gradient were the most sensitive elements driving the number and volume of the mass movement erosion. Mass movement erosion raised sediment concentration, but the eroded material was unable to be transported by runoff in a timely manner. Average sediment concentrations at the model outlet increased by 1.9–11.9 times following the occurrence of mass failures compared to those before. A low instantaneous sediment delivery ratio of 0.032 for the mass movement erosion. The experimental findings help comprehend the influence of mass movement erosion on sediment supply on the gully sidewall in the hilly and gully network, i.e. the Loess Plateau. [ABSTRACT FROM AUTHOR]

[Display omitted] • Continued erosion is expected to occur in the sandy shores. • Equilibrium relationship between sediment supply and hydrodynamic forces has been severely disrupted. • Global climate change-induced sea level rise has a small effect on erosion in the short term. • Human activities are the critical effect on the erosion. • Reduced seaward sediment transport by coastal surface runoffs is a new factor. Most sandy shores (SSs) are currently experiencing erosion to various degrees due to the combined impact of increasing climate change and human activities. In order to reveal the evolution of the SSs in the Shandong Peninsula (SP), shoreline and elevation changing data are obtained from 29 SSs and results show that most (27 of 29) of the SSs exhibited erosion. The length of the SSs has decreased by 241.4 km from 2010 to 2020, and the average shoreline recession rate was found to be 1.0 m/a and the downward erosion rate was in the range of 0.05 to 0.10 m/a. Climate change-induced sea level rise has a smaller effect on the erosion in the short term and the construction of massive coastal engineering structures has become a major cause of local coastal erosion. The coastal erosion rate caused by river damming and sand mining in the early years has abated and reduced seaward sediment transport induced by the expansion of the built-up area has become a new factor of coastal erosion. In the past decade, the 672 km2 net increase in land area mainly originated from human activities, has occupied the original space for hydrodynamic energy dissipation, which has severely disrupted the balance between sediment supply and the hydrodynamic environment and the system then rebalance itself by eroding unprotected SSs. Therefore, with the increase in hydrodynamic forces caused by climate change and the scarcity of sediment supply caused by human activities, continued erosion is expected to occur in the SSs. [ABSTRACT FROM AUTHOR]