Sediment Erosion Research Articles

A review on water jet-sediment coupling and critical techniques during deep-sea polymetallic nodules collection

With the increasing development demand of the modern energy industry, heightened focus has been directed toward the exploitation of deep-sea polymetallic mineral resources. The water jet-sediment coupling under the jet action plays a crucial role in the collection processes. Understanding this mechanism is essential for achieving both efficient collection and minimal environmental disturbance. In this paper, from the deep-sea sediments to which the polymetallic nodules (PMNs) adhere, the characteristics of sediments are studied, focusing on physical and mechanical properties, cementation effects, rheological, and dynamic properties. Upon this foundation, the evolving patterns of flow field structure and characteristics (changes of pressure and velocity), jet-induced sediment erosion and plume generation (erosion pattern, disturbance volume), as well as the characteristics of nodules stripping-movement (such as lift-up force and movement law) are analyzed. Furthermore, following an analysis of the jet-sediment coupling mechanism, the technical applications of jet collection (collection structure design and operation parameter matching) are discussed. Finally, the existing problems and future research directions are discussed. This research reviews the coupling mechanism of water jet and sediment in the process of jet collection, which provides a reference for the design of collection equipment with high efficiency and low-disturbance characteristics.

Advanced high‐precision methodology for assessing sediment erosion in Pelton turbine buckets

AbstractDeveloping highly accurate sediment erosion testing methods for Pelton turbine overflow components is challenging due to their irregularly curved surfaces. In this study, we designed a method to evaluate the sediment erosion of the Pelton turbine bucket using test blocks with an accuracy of 0.0001 g. In addition, we conducted sediment erosion tests on a model Pelton turbine and conducted an in‐depth study on the installation design of the turbine runner and bucket, the design of the erosion test blocks, and the arrangement; we analyzed sediment abrasion distribution on the bucket's working surface. Our test results show that the bucket splitter edge, as well as the root of the working surface, are heavily worn. The maximum erosion rate of the working face is 0.7669 μm/h, and the maximum erosion rate of the splitter edge is close to 5 μm/h, which is highly consistent with the distribution of sediment erosion observed in Pelton turbines operating under sandy river conditions. This test method is essential for examining sediment erosion in Pelton turbines.

Improvements and characterization of a microcosmic-based device for sediment erosion

Improvements and characterization of a microcosmic-based device for sediment erosion

Quantitative reconstruction of sedimentary processes, provenance, and binary sources in Horqin Sandy Land, NE China: An integrated approach

As the largest semi-fixed dune field in China, the Horqin Sandy Land (HSL) provides a valuable opportunity to study the surface processes and paleoenvironmental evolution of drylands in the monsoon region. However, limited data and a single qualitative approach hinder our understanding of the sediment erosion and transport process of the HSL. The ability to trace and quantify sediment provenance of the HSL is increasingly needed to properly understand the source-to-sink processes, and to accurately interpret aeolian–fluvial interactions in terms of a comprehensive database and multidisciplinary approach perspective. This study integrates previously existing grain-size, heavy mineral, element geochemistry, Sr-Nd-Hf isotopic, and zircon-geochronological databases with new petrographic, TIMA automation heavy mineral data and statistical analysis. Together, the high degree of recycling of HSL severely limits the provenance identification of element fingerprints, although these elements are largely inherited from the parent rocks and are not affected by chemical weathering. The heavy minerals, Sr-Nd-Hf isotopes, and zircon U-Pb age composition together reveal that the HSL sediments are a binary mixture of the Palaeozoic-Mesozoic igneous rocks in the Great Xing’an Range (GXR) and the Precambrian metamorphic rocks in the Yanshan Mountains. The isotopic end-element mixing models, multidimensional scaling (MDS) diagrams and inverse Monte Carlo models of detrital zircon ages indicate that GXR and Yanshan Mountains account for ∼ 60 % and ∼ 40 % of the source contributions, respectively. Under the strong influence of the northwest to west winds controlled by the Mongolia-Siberian High, detrital material from the GXR is consistently transported to the interior of the dune field and intensively reworked. The Laoha River and the Yangxumu River originating from the Yanshan Mountains provide stable detrital sources for the HSL. In addition, the transverse flow of the Xilamulun River and the West Liao River has provided sufficient space and sediment for the dunes, which is conducive to the full mixing of materials inside the dune field. The sediment in the southeast of HSL shows an obvious Yanshan Mountains source dominance and a grain-size dependence. The coarse fractions (>63 μm) mainly modified from the river channel sand and alluvial plain of the Yangxumu River (∼75.8 %), while the fine fractions (<63 μm) have a strong affinity with the loess deposit of Yanshan Mountains (∼52.4 %). The fluvial-lacustrine deposits during the last glacial maximum served as a temporary transit station, providing a direct dust source for the modern dunes in the HSL region. Aeolian–fluvial interaction controls the geomorphology and landscape evolution of the HSL in the monsoon region; however, it is challenging to derive insights into the landscape evolution from studying surface samples.

Grain-size distribution in suspension through open channel turbulent flow using space-fractional ADE

The main aim of the present study is to develop a mathematical formulation that can describe the grain-size distribution (GSD) of non-uniform sediments in suspension over erodible sediment beds in a wide open channel under non-equilibrium conditions. The two important characteristics of sediment particles, such as non-local mixing and the hiding-hindering effect during settling, has been considered in the current study. The traditional advection–diffusion equation (ADE) is taken in the modified form as fractional ADE which is capable of capturing non-local movement of particles unlike the traditional diffusion theory where particles jump within a restricted distance along the vertical direction over a small time interval. The equation is further modified for any kth class of non-uniform sediment and the effect of non-local movement is included in the expression of depth averaged sediment diffusivity also. The settling velocity of a particle is taken in a form that contains the effect of hiding and hindering due to the presence of non-uniform particles in the flow. The space-fractional derivative is taken in the Caputo sense where the order α of the fractional derivative varies from 1<α≤2. The non-local effect is considered in the bottom and top boundary conditions also and the governing equation with boundary and initial condition have been solved by Chebyshev collocation method along with Euler’s backward method. The temporal variation of concentration profiles for different size particles is studied by varying α and it is observed that the magnitude of concentration decreases for each size as α increases. Non-local effect on bottom concentration for different size particle is also studied and it is seen that overshooting of bottom concentration gradually decreases as α increases for a particular size. Sensitivity analysis of α on GSD at different heights also has been done. The model has been validated for GSD under equilibrium conditions with available experimental data and it is found that the model aligns well when the non-local mixing effect is taken into account. At the end, an error analysis has been conducted to confirm the accuracy of the presented model.

Estimation of soil loss and sediment yield by using the modified RUSLE model in the Indus River basin, including the quantification of error and uncertainty in remote-sensing images

Context Indus River is the cradle of Pakistani lifeline, and its lower reaches are prone to soil loss owing to bank erosion. Aims The aim was to investigate the sediment yield in the Lower Indus River Basin (LIRB), while addressing challenges related to error or uncertainty in remote-sensing data. Methods We employed a modified revised universal soil loss equation (RUSLE) model, integrating high-resolution digital elevation model (DEM) and calibrated Climate Hazards Group InfraRed Precipitation with station data (CHIRPS). Additional data layers, including land use, soil and cropping data, were also utilised. Key results The extent of actual soil erosion ranges from minimum to maximum erosion; 38.9% area lies in the range &gt;50 Mg ha‒1 year‒1, whereas 23.2% area lies in the range of 0–10 Mg ha‒1 year‒1, and 18.1% area lies in the range of 10–20 Mg ha‒1 year‒1. Conclusions The study identifies critical erosion areas and tackles uncertainties in remote-sensing data. The spatial analysis showed that higher distribution sediment erosion along the channel flow direction from the northern part of LIRB to the Arabian Sea. Implications The findings have provided critical information for policymakers and water managers to implement effective measures to reduce erosion, maintain soil integrity and promote the sustainability of the Indus River system.

A late Paleogene erosion event in the Sanshui Basin, southern margin of the South China Block and its tectonic significance

Ubiquitous onshore Cenozoic basins of the southern margin of the South China Block (SCB) systematically show a stratigraphic hiatus in the sedimentary succession. The absence of strata between the residual Paleogene and the overlying Quaternary in the onshore basin is a serious obstacle to reconstruct their evolutionary history and completely understand the tectonic evolution of the southern SCB margin. Using multiple independent methods, this study reconstructs the entire tectonic subsidence and uplift history in the Sanshui Basin. To do so, we first constrain the eroded thickness and initial erosion time between the Quaternary strata and the residual Huayong Formation (∼41 Ma). The results show that the erosion thickness at the unconformity in the northwestern Sanshui Basin was approximately 2200 m, and the erosion event lasted from approximately 29 Ma to the early Quaternary. The tectonic evolution of the Sanshui Basin during the Paleogene to early Quaternary was characterized by four successive tectonic episodes, three rifting events, and one uplift stage. The first rifting episode lasted from ca. 66–48 Ma, during which approximately 1000 m of tectonic subsidence accommodated the deposition of the Xinzhuangcun (66–59 Ma), Buxin (59–53 Ma), and Baoyue (53–48 Ma) formations. This was followed by the second and third rifting episodes from ca. 48–29 Ma, during which the average tectonic subsidence was approximately 650–850 m, and the residual Huayong Formation (ca. 48–41 Ma) and eroded strata (ca. 41–29 Ma) accumulated. From 29 Ma to the early Quaternary, a tectonic uplift of approximately 1150 m occurred, with a rate of 43 m/Myr, which triggered the erosion of most sediments deposited during the second and third rifting episodes. Our results strongly suggest that although the main depocenters were located offshore since the second rifting episode, rifting in the Sanshui Basin continued until the occurrence of the late Cenozoic erosion event. The differential evolution between uplift (and erosion) onshore and subsidence offshore since the late Paleogene is probably related to the coastward attenuation of southeastern extrusion caused by the Indo–Asian plate collision.

Fault diagnosis of hydro-turbine runner based on improved masking signal method incorporate RLMD

Sediment erosion and foreign object impacts can cause irreversible damage to hydro-turbine runner. It is proposed to use the Improved Masked Signal method combined with the Robust Local Mean Decomposition method (IMS-RLMD) to denoise the acoustic vibrational signals collected from the hydro-turbine runner under normal operating condition, sediment-landed water flow condition, and foreign object impact condition. The IMS method reduces modal aliasing, which is easily occurred in the RLMD decomposition method, and achieves excellent signal denoised by efficiently screening the components. To validate the effectiveness of IMS-RLMD method, we use the Support Vector Machine optimized by the Grey Wolf algorithm (GWO-SVM) to identify the acoustic vibrational signals denoised by different methods. The accuracy of signal set processed by the IMS-RLMD method is 96.67 %, and the accuracy of original signal set and the signal set processed by the EMD, LMD, RLMD and VMD methods are 66.67 %, 75 %, 78.3 %, 86.67 % and 90 %. This result shows that the IMS-RLMD method is not only more suitable for denoising hydro-turbine acoustic vibrational signals, but also retains more effective features in the signals. Meanwhile, the LSTM and CNN models are set as the control group, and the identification results show that the identification method, GWO-SVM, and the denoising method, IMS-RLMD, are the best adapted solutions. Furthermore, it is found that the frequency spectrum of the acoustic vibrational signals changes significantly when foreign objects are washed into the runner or when sediment-landed water flow through the runner. This study provides an effective reference for the daily condition monitoring method of hydropower units and a valuable addition to the condition monitoring and fault diagnosis system of hydro-turbine.

Investigation and Simulation Study on the Impact of Vegetation Cover Evolution on Watershed Soil Erosion

Soil erosion has always been a critical issue confronting watershed environments, impacting the progress of sustainable development. As an increasing number of countries turn their attention to this problem, numerous policies have been enacted to halt the progression of soil erosion. However, policy-driven interventions often lead to significant changes in watershed vegetation coverage, under which circumstances, the original sediment erosion models may fall short in terms of simulation accuracy. Taking the Kuye River watershed as the research subject, this study investigates soil erosion data spanning from 1981 to 2015 and utilizes the Revised Universal Soil Loss Equation (RUSLE) model to simulate soil erosion. It is found that the extensive planting of vegetation after 2000 has led to a rapid reduction in soil erosion within the Kuye River watershed. The original vegetation cover and management factor (C) proves inadequate in predicting the abrupt changes in vegetation coverage. Consequently, this study adopts two improved plant cover and management factor equations. We propose two new methods for calculating the vegetation cover and management factor, one using machine learning techniques and the other employing a segmented calculation approach. The machine learning approach utilizes the Eureqa software (version11.0, Cornell University, New York, American) to search for the relationship between Normalized Difference Vegetation Index (NDVI) and C, ultimately establishing an equation that describes this relationship. On the other hand, the piecewise method determines critical values based on data trends and provides separate formulas for C above and below these critical values. Both methods have achieved superior calculation accuracy. Specifically, the overall data calculation using the machine learning method achieved an determined coefficient (R2) of 0.5959, while the segmented calculation method achieved an R2 of 0.6649. Compared to the R2 calculated by the traditional RULSE method, these two new methods can more accurately predict soil erosion. The findings of this study can provide valuable theoretical reference for water and soil prediction in watersheds.

Numerical study of nozzle erosion and its cascading impact on jet quality

Abstract Sediment erosion is one of the major factors affecting the overall efficiency of hydro-turbines working under sediment laden conditions. The erosion not only decreases the efficiency but also changes the flow characteristics. However, the research regarding the changes in flow characteristics due to erosion is limited. The objective of this study is to identify the changes in flow characteristics of a Pelton nozzle due to erosion. Particularly, in a Pelton turbine system, the nozzle and the bucket are the components that are mostly affected by the erosion. The flow in the nozzle is unaffected by the erosion in the bucket. Nonetheless, the overall flow characteristics in the bucket can be affected by nozzle erosion. The erosion in the nozzle decreases the jet velocity and make it bit more dispersed which eventually decreases its impact force on the bucket and eventually leads to the decrement in overall efficiency of the turbine. A numerical study was conducted to compare the pressure loss, jet diameter, velocity, and dispersion angle between eroded and uneroded nozzle. Some wavy perturbations were induced on the needle and nozzle casing of the reference uneroded case to create the eroded nozzle case. The CFD simulation was then performed in OpenFOAM using its inbuilt multiphase solver, incompressibleVoF (interFoam). It was observed that, with erosion the total pressure loss, jet diameter, and dispersion angle increases but the velocity of the flow decreases. If these changes in flow get detected during operation, it can be used to develop real-time condition monitoring system.

Experimental Investigations of Sediment Erosion in Guide Vanes of Francis Turbine

Abstract Guide vanes are the cascade of hydrofoil like structures surrounding the Francis turbine runner which guides the water from spiral casing and controls the flow to the turbine. A large portion of hydraulic energy of incoming flow is converted to kinetic energy within guide vanes. Sediment erosion causes deterioration of turbine components. Guide vanes are generally eroded due to sediments at the outlet region, facing plates, and clearance gap region. This research encompasses the study of erosion in guide vanes of a 2 kW capacity Francis turbine. The guide vanes were coated with four different coats of colour. The test rig was operated in maintaining erosive environment with an average concentration of sediment particles of 1400 ppm. The total time of operation was 36 hours and the observations were made at interval of each 4 hours. Observable patterns of erosion were seen at different location of guide vanes showing the areas prone to the effect of sediment erosion. The erosion was mostly observed at the trailing edge of the suction side of the guide vanes near to the top and bottom face. The pressure side of the guide vanes experienced a uniformly distributed erosion throughout the width at the leading edge. The causes of erosion were identified as high velocity and acceleration of sediment particles, vortex due to leakage flow and horse shoe vortices. The eroded weight of the guide vanes was recorded for 45 hours of rig operation in erosive environment. Cumulative erosion rate of 0.039 mg gm−1 hr−1 was quantified with an average percentage weight loss of 0.058% was observed in guide vanes.

Assessment of Wear-Resistance in Hydro Turbine Steel: The Impact of Sediment Erosion on a Metal-Ceramic Coating

Abstract Wear of the components of the hydropower plant is mainly because of the striking of rigid silt particles which is carried out with the water. The present study focuses on the development of a ceramic and metal-ceramic protective coating using flame spray and high-velocity oxy-fuel (HVOF) coating technique. A slurry erosion testing equipment has been utilized to examine the wear behavior of specimens with and without coating. Experiments are performed on the coating compositions developed by varying the weight percentage of Co-NiCrAlY (metal) and Al2O3 (ceramic). The erosive behavior of all the specimens has been investigated at impact angles 30°, 45°, 60°, and 90°, impact velocities varying between 6 to 12 m/s. The metallurgical characterization of the developed coatings has been performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. Vickers hardness measurement and surface wettability analysis have been conducted for the mechanical characterization of the coatings. The metal-ceramic coating shows overall better erosion-resistive behavior due to the combined shielding effect and reduction in impact energy of the ceramic and metal respectively. The acquired findings pertain to the refinement of metallurgical, microstructural, and mechanical attributes of the investigated specimen.

Numerical Study of Sediment Erosion of a Francis Turbine with change in guide vane design

Abstract The guide vane is a primary component influencing the sediment erosion of the turbines. For the current work, Francis turbine installed in the Bhilangana-III hydroelectric plant is numerically modelled to investigate the effect of guide vane design on turbine erosion. The existing guide vane profile has been modified to adopt an unsymmetrical hydrofoil shape. Two numerical models of the scaled turbine are developed using the commercial code ANSYS CFX. The first model is prepared with the existing guide vane, whereas the second model incorporates the modified guide vane. The erosion rate density is determined using a modified Grant and Tabakoff erosion model for different operating conditions and a sediment concentration range of 500 – 2500 PPM. The turbine with modified guide vanes showed a reduction in wear of guide vanes and runner by 12-23 % in comparison to that of the existing guide vanes. Further, the erosion is higher for both the part and high load conditions as compared to the best efficiency point operation.

Subsurface Sediment Transport in the Shallow Vadose Zone of Fine‐Textured Soils With Heterogenous Preferential Flows

ABSTRACTSubsurface sediment transport in tile‐drained landscapes occurs through macropores; however, little is known regarding how heterogeneous preferential flows influence fluxes. We performed laboratory rainfall simulations on 10 intact core lysimeters from a tile‐drained field in Indiana, USA to study the impacts of surface and subsurface erosion on sediment leachate in heterogeneous preferential flow paths. Seven rainfall simulations were conducted to assess the impact of rainfall intensity on the leachate of surface eroded sediments (three events), and the impact of antecedent conditions on subsurface eroded sediments (four events). Cumulative sediment yield, linear mixed effects modelling, and hysteresis analyses were performed for all events. Results were presented in a series of four case studies. Results showed that surface sediment leachate concentration and yield were tightly linked to the filtration capacity of lysimeters, with more than 2/3rd of sediment originating from a single lysimeter, despite similar flow leachate volumes from each. Rainfall intensity significantly impacted the transport of surface eroded sediment at the highest intensity. Subsurface sediment erosion from undisturbed macropores was low compared to surface soils, but we found contrasting controls on sediment concentrations at low and high antecedent moistures that were equally important to sediment leachate yields. Disturbed macropores produced comparable sediment yields to surface erosion and behaved similarly to soil pipes in terms of erosion mechanics. Hysteresis results generally highlighted contrasting results for surface and subsurface sources but suggest that the prominence of slow flow, low‐concentration leachate sources can alter the interpretation of results in field‐scale applications. Our findings underscore an array of processes and pathways for sediment transport in the shallow vadose zone, and results will be useful for evaluating new model formulations.

Signature investigation of misaligned jet in Pelton turbines due to flow obstruction in nozzle

Abstract This paper presents a part of the research works related to early stage fault detection and diagnosis of hydraulic turbines. The research works are currently focused on creating a database of the distinctive signals of the faults in the turbine through CFD investigations. The faults in the turbine are induced based on experience and literature review of the common sediment erosion patterns. In the case of Pelton turbines, erosion in the needle with ripple and groove shapes and wavy scales on the buckets are found to be the most common erosion patterns. This paper focuses on asymmetrical erosion patterns of buckets and the needle caused due to flow obstruction in nozzle and consequent misalignment of the jet. The partial blockage for CFD is modelled as a sector of an annulus distributed around the needle. Velocity, pressure, output torque and erosion rates on the needle and buckets are studied. By integrating the trend analysis with machine learning techniques, a real-time condition monitoring tool and procedure can be developed. Since a predictive maintenance of the turbines can be implemented, the outcomes of these research works can have a commercial value for sediment affected power plants globally.

Different nitrogen conditions regulating extracellular polymeric substances and erosion resistance of sewer sediment: Mechanism of microbial metabolism and molecular response

Nitrogen biotransformation plays a vital role in the metabolism of microbial communities in sewers. Extracellular polymeric substances (EPS) secreted by microbial communities can form gel-like sewer sediments, causing clogging of the sewer. However, knowledge on the effects of varying nitrogen conditions on the erosion resistance of sewer sediments and EPS produced by sewer microorganisms is limited. In this study, two typical organic/inorganic nitrogen ratios of sewage were reproduced in simulated sewer reactors, i.e., 3/7 (R1 group) and 7/3 (R2 group). Higher organic nitrogen (ON) concentrations were found to increase the critical erosion shear stress by 26.43%; this was ascribed to increased particle diameter, weakened electrostatic repulsion of sediments and stimulated EPS secretion in the R2 group. The protein and polysaccharide contents of the R2 group were 48.84% and 34.25% higher than those of the R1 group, respectively, which was supported by increased gene abundances for aromatic amino acid synthesis, general secretory pathways of protein, and synthesis of precursors and polysaccharides. Tightly-bound EPS in R2 group exhibited increased contents of hydrophobic protein secondary structures and intermolecular hydrogen bonds, thereby promoting the formation of gel-like sediment structures with enhanced erosion resistance. However, the microbial diversity and the abundance of key genes involved in EPS generation and secretion (e.g., tyrB, yajC, secB, gumF, and gumH) obviously decreased in the R1 group. Moreover, high ON concentrations increased microbial diversity and enhanced microbial glycolysis, tricarboxylic acid cycle and ammonium assimilation. This study reveals the formation mechanisms of EPS in sewer sediments under different nitrogen conditions and their effects on sediment erosion resistance, which contributed to improved sewer system operation and sewer sediment control.

Hypermobility of a Catastrophic Earthquake-Induced Loess Landslide

Landslide mobility refers to how far and fast a landslide can move downslope. It controls landslide impact areas and damage power. Highly mobile landslides are often initiated on slopes steeper than 30°. However, on 18 December 2023, an earthquake-induced landslide (35°52′54″N, 102°51′10″E) exhibited extraordinary mobility, with an overall travel angle of 1.5°, breaking an on-land landslide record. The landslide originated on a gentle slope (3.6°), eroded an earth dam along its travel path, and finally destroyed 51 houses and claimed 20 lives. Remote sensing and field surveys were conducted to provide morphological characteristics of the hazard chain. A numerical program, EDDA (Erosion–Deposition Debris Flow Analysis), was employed to reproduce the flow dynamics and investigate the causes of hypermobility. The findings reveal three primary causes of hypermobility: (1) liquefaction of the saturated silty loess stratum due to the combined effects of irrigation activity and seismic loading, (2) the loose and macro-pore structure of loess, and (3) confined topography and icy channel bed. The mechanisms revealed have broad implications for understanding fluidized mass movements on gentle slopes in seismically active regions.

Wood jam characteristics influence but do not fully explain wood jam morphologic functions

In-stream wood jams alter their surrounding channel morphology, thus setting riverscape morphology and ecosystem function. While wood jams clearly scour pools, retain sediment, and influence bank erosion, there is a lack of observational evidence of how wood jam characteristics themselves control morphologic effects. Here, I analyzed field observations of hundreds of wood jams to test the hypothesis that wood jam characteristics can predict local morphologic effects such as sediment retention, bar forcing, and pool scour. I found mixed support for this hypothesis: While jam characteristics such as porosity, channel blockage ratio, thalweg occupation, and having rootwads and multiple trunks significantly predicted morphologic effect occurrence and magnitude, they only explained a small portion of the variance in those morphologic effects. While wood jam characteristics are relevant in controlling their overall morphologic functions, those functions are both inherently variable and likely affected by numerous other factors, such as reach-scale topography, the sediment transport capacity to supply ratio, and interactions with surrounding wood and vegetation. Wood function restoration may be more effective if it targets reach-scale objectives across dynamic wood jam assemblages, instead of individual jams.

Unerosion: Simulating Terrain Evolution Back in Time

AbstractWhile the past of terrain cannot be known precisely because an effect can result from many different causes, exploring these possible pasts opens the way to numerous applications ranging from movies and games to paleogeography. We introduce unerosion, an attempt to recover plausible past topographies from an input terrain represented as a height field. Our solution relies on novel algorithms for the backward simulation of different processes: fluvial erosion, sedimentation, and thermal erosion. This is achieved by re‐formulating the equations of erosion and sedimentation so that they can be simulated back in time. These algorithms can be combined to account for a succession of climate changes backward in time, while the possible ambiguities provide editing options to the user. Results show that our solution can approximately reverse different types of erosion while enabling users to explore a variety of alternative pasts. Using a chronology of climatic periods to inform us about the main erosion phenomena, we also went back in time using real measured terrain data. We checked the consistency with geological findings, namely the height of river beds hundreds of thousands of years ago.

Distribution and Controlling Factors of the Contourites on the Northern Continental Slope of the South China Sea

ABSTRACTThe northern continental margin of the South China Sea (SCS) is an important component of deep‐water circulation, providing excellent conditions for studying bottom currents in a marginal sea. Seismic data were employed to discern the sedimentary patterns prevalent in the deep‐water continental slope sediments on the northern continental margin of the SCS, encompassing gravity flow, contourite and mixed depositional systems. The contourite depositional system includes various types of deposits (such as separated mounded drifts, patch or channel‐related drifts, deformed sheeted drifts, composite drifts, bottom current sediment waves, plastered contourite drifts) and various morphologic erosional features eroded by the bottom current (such as moats, non‐depositional surfaces, troughs and scarps). These contourite features are related to the continental slope's morphology and its sources. The Dongsha slope exhibits distinctive characteristics marked by intense bottom current erosion and deposition, featuring separated mounded drifts and deformed sheeted drifts along its lower slope. The lower slope of the Pearl River showcases a spectrum of bottom current‐induced features, including sediment wave fields, erosion fields and contourite drifts. The southern flank of the Shenhu slope is characterised by a bottom current erosion field, a non‐depositional surface, a sediment wave field and isolated mounded drifts. On the Yingqiong slope, the contourite drifts are limited to its southern flank where gravity flow action is absent, and the complex geomorphology interacts with the bottom current, forming a complex contourite depositional system. The results of this study serve as a foundational framework for further global research on bottom current circulation and hydrodynamics.