Sediment Mass Research Articles

Increased levels of forestry best management practices reduce sediment delivery from Middle and Lower Coastal Plain clearcut harvests and access features, southeastern states, USA

Over 390,000 ha of forestland are clearcut annually (1–2%) across the Coastal Plain region of the southeastern U.S. where forestland occupies approximately 30 million hectares in the region. Extensive periods of high-water tables, wet-weather and harvesting, rutting, erodible soils, and drainage networks typical of the Coastal Plain increase the potential for erosion and stream sedimentation. To mitigate these impacts, water quality forestry Best Management Practices (BMPs) were developed for erosion and sediment control and are recommended and approved by all southeastern state forestry agencies for application during and after harvests. The goal of this study was to estimate erosion and sedimentation from silvicultural operations in the Coastal Plain under three different and previously recognized levels of BMP implementation including BMP– (<80%), BMP-standard (80%–90%), and BMP+ (>90%), where 90% represents average implementation. A total of 35 recent clearcut sites were evaluated in the Coastal Plain of 12 southeastern states. Erosion was estimated via the USLE-Forest model at five operational features, including decks, stream crossings, haul roads, skid trails, and harvest areas only, which were classified into one of three BMP levels. Sediment traps were utilized on a subset of Coastal Plain sites in Virginia and North Carolina so that sediment delivery ratios (unitless) could be calculated. Clearcut area estimates were obtained from the United States Forest Service (USFS), Forest Inventory and Analysis (FIA) Program. The percent areas comprised within each operational feature were multiplied by total clearcut areas in the Coastal Plain region so that erosion and sedimentation estimates could be expanded to a regional scale. Examination of the different levels of BMP implementation revealed estimated sedimentation rates of 0.5 Mg ha−1 yr−1 and 0.4 Mg ha−1 yr−1 at the BMP-standard and BMP+ levels, respectively. The range of overall estimated sediment masses at the BMP-standard and BMP+ levels most accurately reflects the current state of BMP application in the Coastal Plain. BMPs were most obviously effective at mitigating erosion and potential sediment delivery from Coastal Plain skid trails and haul roads. The highest level of BMP implementation (BMP+) at forest roads and skid trails mitigated approximately 95% of sediment compared to BMP–. Overall sediment removal efficiencies were 77% for BMP-standard and 83% for BMP+ respectively when compared to BMP–. Conclusively, this study demonstrates that forestry BMPs are highly effective at mitigating erosion and stream sedimentation when appropriately applied in the southeastern Coastal Plain.

Numerical Simulation of Water-Sediment Two-Phase Seepage Characteristics and Inrush Mechanism in Rough Rock Fractures

The water-sediment two-phase flow in the rough fracture is one of the main causes of water-sediment inrush. In this study, numerical simulation models of the water-sediment two-phase flow in the smooth and rough fractures were established by ANSYS Fluent software based on the seepage theory; the mechanical properties of the water-sediment two-phase flow under different conditions were systematically investigated, and the influence laws of the surface morphology of the fracture on sediment volume concentration, sediment particle size, and sediment particle mass density were analyzed. In addition, the influence laws of the sediment volume concentration, sediment particle size, and sediment particle mass density on the absolute value of the pressure gradient, mean velocity of the fluid, and fluid turbulent kinetic energy were also illustrated from the perspective of sediment particle distribution. Research shows that during the water-sediment flow in the smooth fracture, the absolute value of pressure gradient Gp, the sediment volume concentrationФ, the sediment particle sizeDp, and the sediment mass densityρpare approximately linear, and the linearity ofGpandDpis the lowest; during the water-sediment flow in the smooth fracture, the mean velocityvof the continuous-phase fluid rarely changes withФ,Dp, andρp. However, during the water-sediment flow in the rough fracture,vis greatly affected byФ,Dp, andρp. During the water-sediment flow in the smooth fracture, the fluid turbulent kinetic energy kt decreases with the increase ofρpandФand decreases with the decrease of ρp. During the water-sediment flow in the rough fracture,ktis significantly affected byФ, Dp, andρp, which was manifested in the changes of curve shapes and deviation of the extreme points.

Initial Distribution and Interannual Decrease of Suspended Sediment in a Two‐Basin Lake Following a Massive Mine Tailings Spill: Quesnel Lake, BC, Canada

AbstractOn 4 August 2014, a tailings dam failure at Mount Polley Mine in central British Columbia led to the largest short‐term release of mine waste into a lake ever recorded. Once released by the breach, slurry entered the smaller of Quesnel Lake’s two basins, called the West Basin, from which the lake drains northwest into the Quesnel River. An estimated 38,000 ± 11,000 tonnes of fine solids remained suspended in the West Basin on 10 September 2014, 37 days postspill. This decreased to within background levels (&lt;300 tonnes) by June 2015, by which time ∼4,000 tonnes of sediment had flowed from the West Basin into the Quesnel River, and ∼31,000 tonnes had been transported east into the main basin, the direction opposed to the mean hydraulic gradient. Here, we evaluate sediment transport in Quesnel Lake following the Mount Polley tailings dam spill. We apply conservation of mass in two ways: using data collected between 12 August 2014 and 15 October 2020 to estimate suspended sediment mass and mass flows into and out of the West Basin; and using one‐ and two‐basin completely mixed models. Suspended sediment concentrations were highly elevated through the first three seasons postspill, then fluctuated within a gradually decreasing, seasonal cycle. The observed mass trend and an analytical mass balance model of a simplified, two‐basin system suggest that suspended sediment mass will fall to below the median prespill mass by 7 ± 5 years postspill.

Sediment Prediction in the Great Barrier Reef using Vision Transformer with finite element analysis

Suspended sediment is a significant threat to the Great Barrier Reef (GBR) ecosystem. This catchment pollutant stems primarily from terrestrial soil erosion. Bulk masses of sediments have potential to propagate from river plumes into the mid-shelf and outer-shelf regions. Existing sediment forecasting methods suffer from the problem of low-resolution predictions, making them unsuitable for wide area coverage. In this paper, a novel sediment distribution prediction model is proposed to augment existing water quality management programs for the GBR. This model is based on the state-of-the-art Transformer network in conjunction with the well-known finite element analysis. For model training, the emerging physics-informed neural network is employed to incorporate both simulated and measured sediment data. Our proposed Finite Element Transformer (FE-Transformer) model offers accurate predictions of sediment across the entire GBR. It provides unblurred outputs, which cannot be achieved with previous next-frame prediction models. This paves a way for accurate forecasting of sediment, which in turn may lead to improved water quality management for the GBR.

Analysis of Sediment in Goronyo Dam, Sokoto, Nigeria

Reservoir sedimentation has been a global bottle neck in maintaining the design storage capacity of reservoirs. Reservoir sedimentation leads to the reduction of the original capacity which affects irrigation, hydropower, flood control, drinking water supply and recreational activities. Introduction of mechanized farming without due regard to the nature of the environment is aggravating the erosion and sediment problem. This study has discussed and analyzed the most important parameters (bulk density, sediment volume, sediment mass, trap efficiency, sediment yield etc) for 31 years (1984 -2015) using Empirical Method and Goronyo Dam Stage Capacity Curve. The Mean bulk density (dBD) was gotten as 0.97gcm3, Sediment Volume (SV) as 26,179,302m3 , Sediment Mass (SM) as 25,393,922.94 tones, average annual sedimentation as 819,158.81ty-1 , Trap Efficiency (TE) as 90.2%, Sediment Yield (SY) as 908,158.00 ty-1, Specific Sediment Yield (SSY) as 42.35𝑡𝑘𝑚−2𝑦−1, The loss of storage (26,179,302m3)

History of slope instability in the Oldina plantation, Tasmania

Background: This paper describes a landslide swarm generated by exceptionally high two-day rainfall (c. 300 mm) associated with a stationary cut-off low pressure system over northern Tasmania in early June 2016 and investigates evidence for previous slope instability. The landslide swarm occurred in a recently harvested plantation in the Inglis River catchment at Oldina, south of Wynyard in north-west Tasmania. Within a relatively small area of plantation underlain by weathered Permian tillite and minor siltstones more than thirty rapid earthflows, rotational and translational landslides occurred. Many landslides also occurred in the nearby Forth and Mersey River catchments. Methods: Field observations combined with a digital elevation model produced from high-resolution drone imagery were used to describe the morphology of the Oldina landslides, and to calculate the mass of soil, sediment, and woody debris displaced. Radiocarbon dating of charcoal exposed in landslide backwalls enabled palaeo-landslides and periglacial activity at Oldina to be dated. Results: An estimated 48,400–72,310 t of soil, sediment and woody debris was carried downslope by the major landslides but has been retained within the plantation area. The total sediment loss from the affected upper catchments is likely to be greater than the above estimate as the contribution from small riparian landslides, sheet, gully, and rill erosion has not been accounted for, nor has streambank erosion and sediment transported off the study site been measured. Radiocarbon dating of charcoal in sediments indicated that two landslides had evidence of previous instability in the Holocene. Most ages indicated that previous instability dated to 35–15 cal ka BP, i.e., to a time when the climate was cold and dry and freeze-thaw processes in a sparsely vegetated landscape were active. Conclusions: During planning for harvest the soils developed on Permian tillite were correctly described as having a low to moderate risk of landslide erosion. This study concludes that the landslides initiated in June 2016 resulted from exceptionally heavy rain falling on harvested steep and hilly land coupled with the decline in root strength of the harvested trees. The frequency of such a combination of circumstances may increase if high-intensity rainfall increases in Tasmania as the result of climate change. To improve the long-term stability of this terrain and the overall sustainability of plantation forestry it is recommended that landslides and riparian areas are seeded with native vegetation, and that the current assessment of landslide risk for this terrain is re-evaluated.

Controls on Sediment Bed Erodibility in a Muddy, Partially-Mixed Tidal Estuary

The objectives of this study are to better understand controls on bed erodibility in muddy estuaries, including the roles of both sediment properties and recent hydrodynamic history. An extensive data set of erodibility measurements, sediment properties, and hydrodynamic information was utilized to create statistical models to predict the erodibility of the sediment bed. This data set includes &amp;gt;160 eroded mass versus applied stress profiles collected over 15 years along the York River estuary, a system characterized by “depth-limited erosion,” such that the critical stress for erosion increases rapidly with depth into the bed. For this study, erodibility was quantified in two ways: the mass of sediment eroded at 0.2 Pa (a stress commonly produced by tides in the York), and the normalized shape of the eroded mass profile for stresses between 0 and 0.56 Pa. In models with eroded mass as the response variable, the explanatory variables with the strongest influence were (in descending order) tidal range squared averaged over the previous 8 days (a proxy for recent bottom stress), salinity or past river discharge, sediment organic content, recent water level anomalies, percent sand, percent clay, and bed layering. Results support the roles of 1) recent deposition and bed disturbance increasing erodibility and 2) cohesion/consolidation and erosion/winnowing of fines decreasing erodibility. The most important variable influencing the shape of the eroded mass profile was eroded mass at 0.2 Pa, such that more (vs. less) erodible cases exhibited straighter (vs. more strongly curved) profiles. Overall, hydrodynamic variables were the best predictors of eroded mass at 0.2 Pa, which, in turn, was the best predictor of profile shape. This suggests that calculations of past bed stress and the position of the salt intrusion can serve as useful empirical proxies for muddy bed consolidation state and resulting erodibility of the uppermost seabed in estuarine numerical models. Observed water content averaged over the top 1 cm was a poor predictor of erodibility, likely because typical tidal stresses suspend less than 1 mm of bed sediment. Future field sampling would benefit from higher resolution observations of water content within the bed’s top few millimeters.

Cohesiveness of the Nigerian Mahin mud coast sediment: Implications for erodibility and morphodynamic modelling

Cohesive sediments in coastal zones and estuarine mudflats have transport mechanisms that are not well understood due to the complex sediment properties that influence their erodibility. However, understanding coastal sediment composition and behaviour is important to determine its resistance to hydrodynamic forcing. This study investigates the properties of mudflats along the Mahin coast of southwestern Nigeria to identify the dominant factors controlling their resistive forces and erodibility potentials. Sediment samples obtained from 6 stations along this muddy coast were subjected to physical, mechanical, electrochemical and mineralogical analyses. Our results show that the sediments are inorganic silt of high plasticity, containing inactive clay minerals. With cohesion and frictional angles (φ) that ranged from 42.4 to 46.9 kN/m2 and 10.2–11.7°, respectively, the sediments can be described as highly cohesive and overconsolidated. Organic contents in the muds are <20% of the entire sediment mass, reflecting the impact of vegetation removal along the coast. Whereas fairly neutral to alkaline pH shows the role of seawater in maintaining the chemical balance in the mud. Sediments with proximity to the western and eastern estuaries in the study area show similar characteristics compared to those farther from the estuaries. In addition, sediments closer to the estuaries are dominated by an active illite-montmorillonite mixed clay layer, which makes up <20% of their bulk composition, while those farther are dominated by illite and kaolinite. The correlation analysis revealed that the physical and mechanical properties of the mudflat sediments along the Mahin coast, southwestern Nigeria are influenced by their chemistry and mineralogical composition. Estuarine dynamics also play a key role in recent sediment transport along the mudflat. This study thus provides baseline data on sediment properties for modelling morphological changes of the Nigerian Mahin mud coast. In-situ erodibility experiments are recommended to ascertain the erosion parameters of the area.

Establishment of prediction models of trapped sediment mass and total filtration efficiency of pre-pump micro-pressure filter

The filter before a pump is a key piece of equipment of a micro-irrigation system, which can ensure safe and stable operation. This paper examines a pre-pump micro-pressure filter, using the trapped sediment mass and total filtration efficiency as the assessment indicators. Orthogonal experiments of the physical model of the inlet flow, sediment content, water separator type, and filter area were conducted. The experimental results were processed by analysis of variance, dimensional analysis, and multiple regression analysis. The influences of the factors affecting the trapped sediment mass in descending order were the sediment content, filter area, water separator type, and inlet flow. The influences of the factors affecting the total filtration efficiency in descending order were the filter area, sediment content, water separator type, and inlet flow. While the water separator type significantly affected the trapped sediment mass and total filtration efficiency, the difference between the different treatments was insignificant. The prediction model for the trapped sediment mass (total filtration efficiency) was established with an R2 of 0.998 (0.889). Since the relative errors between the predicted and measured values were less than 6%, these models could produce accurate predictions. These results provide technical support for the structural optimization and filtration mechanism of the filter and advance the theory of micro-pressure filtration.

Per- and poly-fluoroalkyl substances in sediments from the water-level-fluctuation zone of the Three Gorges Reservoir, China: Contamination characteristics, source apportionment, and mass inventory and loadings

Sixteen paired surface sediment samples (0–5 cm, n = 32) covering upstream to downstream of water-level-fluctuation zone of Three Gorges Reservoir, China were collected in March 2018 (following six months of submergence) and September 2018 (after six months of exposure). Seventeen per- and poly-fluoroalkyl substances (PFASs) were quantified to evaluate contamination characteristics, apportion source categories and estimate mass inventory and loadings. The concentration of ΣPFASs ranged from 0.26 to 0.82 ng·g−1 at high water-level (HWL) and 0.46–1.53 ng·g−1 at low water-level (LWL). Perfluorooctanoic acid (PFOA, mean: 0.32 ng·g−1) and perfluorooctane sulfonate (PFOS, mean: 0.12 ng·g−1) dominated, accounting 44.9% and 16.3% of the total PFASs, respectively. The distribution of PFASs was more influenced by anthropogenic activities than physicochemical parameters of the sediments. Positive matrix factorization (PMF) identified PFOA-based products was the major sources (40.1% and 38.6%, respectively). Besides, the direct sources of PFOA-, PFOS-, PFNA-and PFBA-based products played the predominant role, while the indirect degradation of precursors contributed relatively little. The sediment (0–5 cm) mass inventory of PFASs at LWL (57.5 kg) was higher than HWL (39.3 kg). The annual mass loadings of the total PFASs, PFOA, PFOS, perfluoroundecanoic acid (PFUdA) and perfluorononanoic acid (PFNA) from the upstream to the middle-lower reaches of Yangtze River were 27.4 kg, 11.1 kg, 4.63 kg, 2.89 kg and 2.57 kg, respectively. This study could provide the basic datasets of PFASs in surface sediments of the TGR, and also indicate an important transport of PFASs from upstream to the lower reaches, which should be further studied as well.

The constant flux and constant sedimentation (CF:CS) 210Pb chronological method applied to determine sedimentation rates at Amazon River watershed, Brazil

Activity profiles of excess 210Pb determined in three sediment cores from Amazon River mouth, Amapá State, Brazil, provide the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions. Chemical data on the sediments allowed calculation of the Geoaccumulation Index (Igeo) for each constituent analyzed. Significant direct relationships among Fe2O3 and major/minor constituents Al2O3 (r = 0.86), K2O (r = 0.94), MgO (r = 0.89), MnO (r = 0.92), BaO (r = 0.64), P2O5 (r = 0.62), and TiO2 (r = 0.54), inverse correlation between Fe2O3 and SiO2 (r = −0.93) and the direct correlation between SiO2 and LOI (loss on ignition) (r = 0.88) suggest competitive sorption of Si to Fe oxides and organic compounds. Igeo values between −3.75 and 0.22 for Si, Al, Na, K, Ca, Mg, Fe, Mn, Ti, P, S, Sr, Ba, Rb, Zn, Cr, Nb, Cu, Ni, As, V, Ga, Tb, Y, and Ce indicate practically unpolluted environments despite several mining activities in the Amazon basin and its vicinity. The apparent sediment mass accumulation rates between 0.5 and 2.4 gcm−2yr−1 are compatible with the results of others studies. The 210Pb activity at one sampling point (P1) exhibited an abrupt fluctuation, similar to findings from previous studies held at the northern channel of the Amazon River discharge. On the other hand, in two sediment profiles (P2 and P3), the excess 210Pb activity data validate the use of the CF:CS method, yielding unique straight lines and increasing the sedimentation rates database.

Fine-Grained Sediment and Phosphorus Storage in a Suspended-Load-Dominated, Alluvial Channel

HighlightsIn-channel sediment and TP storage were quantified along 13.5 km of a stream.TP and sediment masses were 1 and 3 times greater than their respective annual watershed load.Colluvial material at streambank toe represented the dominant storage pool.Sinuous stream reaches exhibited significantly greater storage versus channelized reaches.Abstract. In-channel storage of both fine sediment and sediment-bound phosphorus has been recognized as potentially large contributors to respective watershed loads, yet they are rarely quantified in the field. In this field-based study, we quantified and characterized in-channel fine sediment and total phosphorus (TP) storage within a third-order stream. We hypothesized storage to be significant within the context of watershed-scale sediment and TP loads and that storage trends are influenced by channel characteristics and hydraulics. In May 2015, the volume of stored in-channel sediment was estimated within a 13.5 km stretch of Walnut Creek, an alluvial stream draining an agriculturally dominated watershed in Jasper County, Iowa, USA. Storage volume was estimated in-field through a series of 240 transects which were stratified across reaches of the varying channel and hydraulic conditions (e.g., sinuosity, stream power). Overall storage volume was broken down into feature classes (e.g., point bars) based on in-channel depositional processes. Following in-field quantification, feature class sediment samples were collected and analyzed for physical properties (e.g., bulk density) and TP concentration. Physical and chemical analyses, coupled with in-field volume estimation, allowed for watershed-scale masses of in-channel sediment and TP to be calculated and then placed within the context of respective annual loads. Sediment and TP were estimated to be stored at ~2.7 Mg m-1 and 0.7 kg m-1, respectively. Sinuous reaches exhibited significantly greater sediment storage volume (p &amp;lt; 0.001) and depth (p &amp;lt; 0.001) versus straight reaches. Reach sinuosity exhibited a significant positive correlation (p = 0.03) with storage mass and represented the most effective storage predictor. The majority of storage mass (72%) was represented by colluvial material accumulations at the streambank toe. Loose bed sediment was the second greatest contributor to storage mass (18%), with the remaining feature classes (e.g., bars) representing a combined ~10%. Sediment storage mass was ~3.25 times greater than the watershed suspended sediment load for 2015. The TP mass was found to be nearly equal to the respective watershed load for 2015. In-channel sediment and TP storage masses within Walnut Creek were found to be significant in comparison to respective annual loads, and thus storage is expected to play a significant role in respective watershed routing, loading, and the overall budgets of these parameters. Though challenging, quantification of in-channel fine sediment and TP storage is necessary to relate source contributions (e.g., streambank erosion) to watershed loads and is critical to account for interannual sediment and TP export. Keywords: Channel evolution, Channel morphology, Iowa, Sinuosity, Stream power, Water quality, Watershed export.

Advection–diffusion settling of deep-sea mining sediment plumes. Part 2. Collector plumes

We develop and investigate an advection–diffusion-settling model of deep-sea mining collector plumes, building on the analysis of midwater plumes in Part 1. In the case of collector plumes, deposition plays a predominant role in controlling the mass of sediment in suspension, and thus on setting the extent of the plume. We first discuss the competition between settling, which leads to deposition, and vertical turbulent diffusion, which stretches the plume vertically and reduces deposition. The time evolution of the concentration at the seabed is found to be a highly nonlinear function of time that depends non-trivially on the ratio of diffusion to settling time scales. This has direct implications for the three extent metrics considered, namely the instantaneous area of the seabed where a deposition rate threshold is exceeded, the furthest distance from the discharge where the plume exceeds a concentration threshold and the volume flux of fluid in the water column that ever exceeds a concentration threshold. Unlike the midwater plume, the particle velocity distribution of the sediment has the greatest influence on the extent metrics. The turbulence levels experienced by the plume also markedly affects its extent. Expected variability of turbulence and particle settling velocity yields orders of magnitude changes in the extent metrics.

Origin, weathering and paleoclimatic significance of Middle - late Pleistocene slope covers, Mt. Kenya, Kenya

Stacks of the Pleistocene tills and associated airfall/slopewash/colluvial sediment abound on East African Mountains but few localities exist where thick deposits of middle to Late Pleistocene age can be studied to bedrock with topography the main soil-forming agent over &lt;0.8 Ma. Two tills form the main structure of the catena, the oldest buried in the crest, backslope and footslope of the deposit, the youngest forming the crest and upper backslope, with massive colluvial infill forming a still younger sediment mass superposed on older sediment in the lower backslope, footslope and toeslope, the latter all radiocarbon dated to within the last glaciation (Liki on Mt. Kenya; Weichselian in Europe, Wisconsin in North America). The moraine stack, first identified by J.W. Gregory in the late 19th century, as belonging to the ‘Older Glaciation’ (Illinoian in North America; Teleki on Mt. Kenya), is much older than originally thought with tills and other paraglacial sediment extending to saprolitic bedrock, paleomagnetic assessment and relative weathering indices placing the mass in the Brunhes Chron. These results demonstrate that despite erosion and weathering, paleosols in toposequences near the margins of successive glaciations retain properties allowing reconstruction of environmental changes over long periods of time.

Implementation of Forestry Best Management Practices and Sediment Delivery in Three Regions of North Carolina and Virginia

Abstract Forestry best management practices (BMPs) were created in response to the Clean Water Act of 1972 to protect water quality from nonpoint source pollutants such as sediment. The objectives of this study were to quantify the relationship between BMP implementation and sediment delivery on 58 recently harvested sites across three physiographic regions and five forest operational features. BMP implementation rates, erosion rates, sediment delivery ratios, and sediment masses were calculated at 183 silt fences functioning as sediment traps adjacent to streams in Virginia and North Carolina. Major access system features, including stream crossings, skid trails, and haul roads, typically delivered the greatest sediment mass to streams and had the highest sediment delivery ratios on a per feature basis. When accounting for sediment mass delivered and area in each feature, harvest area accounted for approximately 70% of sediment delivered to streams for all regions. Most features had proportionally higher erosion rates than sediment masses collected at silt fences, indicating that most erosion generated by forest operations is being trapped by either harvest areas or streamside management zones. For most features and regions, as BMP implementation increased, erosion rates and the sediment masses delivered to streams decreased.

Controls on submarine canyon morphology along a convergent tectonic margin. The Southern Caribbean of Colombia

Submarine canyons are major conduits for sediment transfer from continental shelf to deep marine environments. Mass failures and faults play a key role in the initiation and evolution of submarine canyons along convergent tectonic margins, in addition to continental sediment supply. Here we analyze high-resolution bathymetry and seismic data from the Colombian southern Caribbean to investigate the controls on submarine canyon morphology along a convergent tectonic margin. We propose three end-member types of canyons: Type I canyons have a direct connection to a major river associated with high sediment supply. These canyons are highly erosive and cut topographic barriers created by tectonic deformation. Type II canyons are associated with faults at the canyon's head, where the location, orientation, and sinuosity are controlled by fault strike. Also, the presence of faults is related to an increase in the occurrence of mass failures from the steep canyon borders, increasing the depth and width asymmetry. Finally, Type III canyons evolve toward the continental shelf edge through retrogressive mass failures. These mass failures produce erosional scars that merge downslope to create submarine canyons in early stages of development, which later evolve to wider but shallow canyons due to the progressive basinward merging. We argue that the morphology of each canyon type is controlled by the interaction between continental sediment supply, mass failures, shelf width, and fault occurrence. We also demonstrate that seafloor topography influences the size of submarine fan deposits at the mouths of canyons. We identified large fan deposits (>650 km2) on the continental rise, whereas in piggyback sub-basins we found smaller fans (<60 km2). Our analysis of downdip canyon morphology and associated deposits can be used to predict the development of submarine canyons and associated fans in convergent tectonic margins worldwide.

Calibrated Suspended Sediment Observations Beneath Large Amplitude Non‐Linear Internal Waves

AbstractWhile it has been recognized for some time that large amplitude non‐linear internal waves (NLIW) can mobilize and transport sediment, quantitative observations of this process are rare. Rarer still are accompanying estimates of suspended sediment mass concentration (SSC) during the passage of NLIW. Here, we present high resolution observations of NLIW and the SSC response within the bottom boundary layer. The observations were made in 250 m of water in a mildly sloping region of the Browse Basin on Australia’s Northwest Shelf. We compare two independent but direct calibration methods, and employ Bayesian methods to estimate the uncertainty in SSC. During a large NLIW event, the peak mean SSC estimate at 0.49 m above the sea bed was 161 mg L−1, with a maximum time‐rate‐of‐change of 0.14 mg L−1 s−1. The unsteady boundary layer forcing under NLIW resulted in a variable time‐height dependent relationship between bed stress and SSC with increasing height above the sea bed. Suspended sediment was restricted to the bottom mixing layer, with sharp vertical gradients of up to 40 mg L−1 m−1 observed at the edge of the layer. The observations presented here are intended to offer guidance to numerical sediment modelers about likely SSC under strong NLIW.

An Investigation on the Migration and Settlement Law of Temporary Plugging Particles in Horizontal Wellbore

Migration and settlement of temporary plugging particles of different sizes affect the effect of temporary plugging, which in turn affect the effect of reservoir reconstruction. However, the migration and settlement laws of temporary plugging particles in horizontal wellbore are still unclear. In order to study the migration and settlement laws of temporary plugging particles in horizontal wellbore, a set of multicluster perforation physical model experiment device for horizontal wells was built. Based on this experimental device, the effects of mass ratio, pumping rate, and adding sequence on the migration and settlement laws of temporary plugging particles were studied, respectively. The experimental results show that the 3 mm temporary plugging particles move forward in a leaping manner at the bottom of the horizontal wellbore and the 1 mm particles are distributed in layers in the horizontal wellbore, and the particles are less in the upper part of the wellbore and more in the bottom of the wellbore. The migration trajectory of the two mixed particles is similar to the single. Under different mass ratio, the settlement mass of particles in the perforation clusters at the outlet end is greater than that in the entrance end. When the 3 mm particles account for a relatively large amount ( m 3 mm : m 1 mm = 5 : 1 ), the settlement mass of the particles in the two perforation clusters is greater than other mass ratio conditions. For the same perforation, the settlement mass becomes greater as the proportion of 3 mm increases. When only 3 mm particles are considered, with the increasing of displacement, the mass of particles in the perforation clusters at the inlet end increases, and the mass of particles in the clusters at the outlet end decreases. With the increase of displacement, the sedimentation mass of particles in high angle perforations decreases, while the sedimentation mass in other perforations increases. Adding 3 mm first and then 1 mm particles, the particle settlement mass in the perforation cluster at the outlet end is twice the mass of the particles in the perforation cluster at the inlet end. Reversing the sequence, the settlement masses of the particles in the two clusters are almost equal. The particle distribution in the perforation at different angles has obvious gradation. The smaller the angle, the greater the settlement mass of the temporary plugging particles. This research results will provide reference for temporary plugging and fracturing construction.

Magnitude and factors influencing soil loss and sedimentation in the Mun River Basin, Thailand

Previous studies have shown potentially high soil loss in the Mun River Basin, the largest sub-basin of the Lower Mekong Region in Thailand, due to its rapid land cover changes, agricultural practices, and soil erodibility properties. This study aims to estimate the soil loss and sedimentation rates in the Mun River Basin using the analysis of long-term sediment loading data from the Royal Irrigation Department (RID), GIS-based Revised Universal Soil Loss Equation (RUSLE) approximation, and sediment core analyses. This study found that a high loss (>12.5 ton ha−1 yr−1) and RID sediment loading rate were predominant in the upper basin. The support practice was most sensitive to the loss, but during extreme rainfall events (El Niño Southern Oscillation), the role of rainfall intensity was more pronounced. Therefore, mechanical measures should be adopted in combination with the soil–water conservation practices to mitigate the effects in eroding agricultural areas. Sediment core analyses revealed that the highest sediment deposition rate was up to 5.2 cm yr−1 in the middle part of the Mun River Basin, primarily due to the floodplain lowland characteristics and repeated flooding events. Several factors influenced the sediment deposition rate: installation of dams or check dams, waterway maintenance, upstream land cover, water plant outgrowth, and flooding. The RID sediment loading also suggests that sediment mass transfer to the Mekong River was highly contributed from the lower basin, where the sediment from the upper part was either trapped by the dams or deposited within the channel.

Combining GRACE and satellite altimetry data to detect change in sediment load to the Bohai Sea

The Gravity Recovery and Climate Experiment (GRACE) satellites provide a powerful tool for monitoring sediment mass change. However, signal leakage from nearby groundwater storage depletion in the North China Plain limits the potential capacity of GRACE to estimate sediment input from the Yellow River flows into the Bohai Sea. In the present work, we developed an improved approach based on forward modeling to reduce signal leakage from GRACE data and combined it with satellite altimetry to recover sediment load changes from 2003 to 2013 to the Bohai Sea. The total sediment input averaged 1.7 ± 0.8 Gt/yr, which agrees well with the estimate based on in-situ sediment data measured from the sediment cores (1.1 Gt/yr). Our method is also capable to describe sediment seasonal variations, with higher inputs in winter and spring, which confirm the output simulated by the sediment transportation model. We make presently tentative connections of seasonal variations to sediment resuspension driven by climatic monsoons contributed rough seas: although sediment load in rivers peaks in summer, low water discharge of the Yellow River leads to most of the sediment being deposited in a narrow area near the river mouth and not transported into the Bohai Sea; in winter and spring, huge waves provide favorable conditions for resuspension resulting in large amounts of sediment near the estuary being transported to the ocean along with northward waves. Moreover, our results indicate coastal erosion is also a nonnegligible resource of the sediment in the Bohai Sea. Comparing to the traditional approach, our study provides a new technological way to derive sediment in the Bohai Sea, which is capable of providing continuous measurements with improved timeliness at a lower cost.