Sinuous Channels Research Articles

32 years of changes in river paths and coastal landscape in Bangladesh, Bengal Basin

AbstractThis study examines the geomorphological changes and environmental impacts on the coastline and the evolution of major river systems in Bangladesh over the past 32 years using remote sensing and GIS analyses. The central coastal area, characterized by fine sediments, has experienced significant land erosion due to the dynamics of the Meghna Estuary and its depositional patterns. In contrast, the southwestern Sundarbans Forest coast has remained relatively stable, aided by mangrove root stabilization despite anthropogenic threats. Channel migration analysis revealed the Brahmaputra River’s persistent braided configuration, while its tributaries, Teesta and Dharla, increased meandering nature due to reduced water availability and human interventions. The Ganges-Padma system displayed a shift towards a more sinuous channel pattern driven by reduced water discharge due to the Farakka Barrage construction in the upstream and a minor decrease in precipitation. The Upper Meghna River maintained moderate sinuosity with stable anastomosed patterns, whereas the lower Meghna River’s convergence with the Jamuna and Padma Rivers increased its susceptibility to erosion. These findings highlight the interplay of natural processes and human activities in shaping the coastal and fluvial landscapes of Bangladesh and the Bengal Basin, emphasizing the need for sustainable land-use practices and adaptive management strategies to mitigate future risks associated with sea-level rise and river course changes.

Flow turbulence and morphological characteristics in an asymmetric alluvial sinuous channel

On a physical model, an experimental study has been carried out to study the flow turbulence and morphological characteristics in an asymmetric sinuous channel. Velocity distribution shows no evidence of outer bank cell of secondary flow. Streamwise turbulence intensity is more dominating than transverse and vertical turbulence intensity. Bursting events are quantified by octant analysis, which reveals that the internal ejections and external sweeps are prominent. There is a significant role of internal ejection, external sweep events, and helical flow in forming erosion and deposition zones. The transition probabilities of movement states that stable organizations of events are the most possible movements, whereas cross organizations of events have the least possible movements. The morphological changes at all cross sections shows deposition near the inner bend and maximum erosion near center at the bend apex, progressing towards the outer bend. Moreover, the deposited sediment bar at the inner bend promoted flow separation over the point bar. Topographic steering of the flow induces reasonable variations in the redistribution of flow velocity. As the study provides insights into the flow turbulence and morphological characteristics in an asymmetric sinuous channel, it will be a beneficial help to engineers for planning hydraulic structures.

Architecture and depositional processes of a submarine channel during the late Miocene in the Yinggehai basin, northwestern South China Sea

Submarine channels are the most extensive sediment transport systems on Earth. They transport sediment over hundreds of kilometers and form sediment deposits in the deep-sea, which can act as hydrocarbon reservoirs. During the Late Miocene, a sinuous submarine channel with sediment processes was discovered in the Yinggehai Basin, northwestern South China Sea. However, process interpretations of the factors that influence the stacking patterns, distribution, and morphology of these sinuous channel deposits in this region are not well understood. Based on the interpretation of high-resolution 3D seismic data and exploration well data, and insights from flow dynamics, we analyzed the factors influencing channel morphology, the architecture of the channel, and its associated geomorphic evolution. The channel can be divided into three sections (Sections Ⅰ, Ⅱ, and Ⅲ) in terms of its planform, and into two seismic units (Unit 1 and Unit 2) in terms of its vertical structure. The sinuous submarine channel originated from a combination of inherent structural features from secondary faults and strong erosion from turbidity currents, which occurred due to a sharp decline in sea level during the Late Miocene. Changes in the channel's orientation led to erosion and channel-margin failures, causing an increase in channel width and a decrease in margin gradient. The distribution and stacking patterns of the deposits are greatly influenced by the provenance, sea level changes, and the morphology of the channel. In Sections Ⅰ and Ⅲ, a river-like secondary flow with a limited lateral density gradient leads to vertical deposits. In Section Ⅱ, changes in the channel's orientation altered its morphology and induced topographic forcing, producing a strong river-like secondary flow. This flow consistently caused sediment to accumulate on the inner bank and erode on the outer bank, leading to lateral stacking of deposits in Unit 2. During the filling of Unit 2, diapiric activity uplifted the strata, resulting in thinner deposition in Section Ⅲ, while deposition thickness increased in Section Ⅱ with sufficient provenance. Unit 1 of Section Ⅲ displays desirable properties for a hydrocarbon reservoir, including thick sandstone with good sorting and roundness. This study provides valuable insights into the diverse architectures of spatially and temporally linked submarine channels, and establishes a correlation between the evolutionary process of the channel and the stacking patterns of its constituent elements.

Tidal versus fluvial point bars: Key features from the integration of outcrop, core and wireline log information of Triassic examples

AbstractThe Triassic red beds of the Tabular Cover of the Iberian Meseta are an excellent reservoir outcrop analogue, a direct consequence of high‐quality exposures, which offer exceptional three‐dimensional outcrops, as well as a wide variability of depositional environments. Fluvial and transitional with tide‐influenced and wave‐influenced settings are recognised. Three point bar geobodies of similar scale, but influenced by different processes, were selected from this succession. Point bar geobody 1 was influenced by purely fluvial processes while geobodies 2 and 3 were tide‐influenced. Both types of geobody were developed as point bar deposits in sinuous channels. A fully integrated study was carried out on these geobodies, utilising both outcrop and subsurface‐based approaches, to characterise the key differences between fluvial and tidal point bars in the sedimentary record. The outcrop‐based component involved traditional field data collection methods alongside digital techniques and data capture, including the use of digital outcrop models. Additionally, subsurface‐based methods were employed, utilising core and wireline logs obtained from wells drilled in close proximity to the outcrop. The integration of these approaches aims to accurately differentiate the depositional settings of the three different geobodies, which while apparently very similar in many key respects also exhibit considerable differences when considered from the perspective of subsurface management of potentially similar geobodies. This study also emphasises the need to clearly distinguish high‐sinuosity deposits based on their depositional sub‐environment in order to properly evaluate their potential for subsurface management. Additionally, it highlights the presence and importance of internal baffles that may well influence fluid migration and indeed even compartmentalise geobodies. Three point bar geobodies of similar scale, but influenced by different processes, have been selected in this succession. A fully integrated study was carried out on these geobodies, utilising both outcrop‐based and subsurface‐based approaches, to characterise the key differences between fluvial and tidal point bars in the sedimentary record.

Timescale of the Morphodynamic Feedback Between Planform Geometry and Lateral Migration of Meandering Rivers

AbstractAcross varied environments, meandering channels evolve through a common morphodynamic feedback: the sinuous channel shape causes spatial variations in boundary shear stress, which cause lateral migration rates to vary along a meander bend and change the shape of the channel. This feedback is embedded in all conceptual models of meandering channel migration, and in numerical models, it occurs over an explicit timescale (i.e., the model time step). However, the sensitivity of modeled channel trajectory to the time step is unknown. In numerical experiments using a curvature‐driven model of channel migration, we find that channel trajectories are consistent over time if the channel migrates ≤10% of the channel width over the feedback timescale. In contrast, channel trajectories diverge if the time step causes migration to exceed this threshold, due to the instability in the co‐evolution of channel curvature and migration rate. The divergence of channel trajectories accumulates with the total run time. Application to hindcasting of channel migration for 10 natural rivers from the continental US and the Amazon River basin shows that the sensitivity of modeled channel trajectories to the time step is greatest at low (near‐unity) channel sinuosity. A time step exceeding the criterion causes over‐prediction of the width of the channel belt developed over millennial timescales. These findings establish a geometric constraint for predicting channel migration in landscape evolution models for lowland alluvial rivers, upland channels coupled to hillslopes and submarine channels shaped by turbidity currents, over timescales from years to millennia.

Landscape evolution of the Ganga-Sai interfluve in response to river dynamics and Late Pleistocene-Holocene climate change via a meander cut-off lake of a plains-fed channel

The floodplains in the interfluve between the Ganga and Sai rivers in the Central Ganga Plains exhibit a broad suite of geomorphic features such as a linear array of meander cut-offs and oxbows representing abandoned sinuous channels. Here we integrate regional and local scale geomorphic analysis using satellite imageries with detailed chronostratigraphic and paleoclimatic reconstruction from a large oxbow lake (Baraila Tal) in the paleochannel belt to infer landscape evolution in this region. The stratigraphic succession at Baraila Tal supported by sedimentology and stable isotope composition of organic matter and micro-gastropod shells suggests that the lake was previously a part of an active fluvial system, and the depositional environment transformed from a fluvial to a lacustrine system in response to geomorphic and climatic changes during the post-LGM period. Integrating geomorphic and paleoclimatic data, we identify four stages (I-IV) of landscape evolution in the Ganga-Sai interfluve region during the Late Pleistocene-Holocene interval: (I) active channel phase of paleo-Sai river before 12 kyr, (II) development of paleochannel belt and meander cut-offs during 12–8 kyr, (III) development of ‘misfit’ Sai river and gullied landscape during 8–7 kyr, and (IV) expansion of ephemeral lakes (wetlands) and subsequent filling post 7 kyr. We have demonstrated the use of paleoclimate and paleovegetation data retrieved from a meander cut-off lake for deciphering landscape evolution.

Increased sediment connectivity between deltas and deep-water fans in closed lake basins: A case study from Bozhong Sag, Bohai Bay Basin, China

The connection between deltaic clinothem growth and the formation of down-dip deep-water systems on continental margins has been extensively discussed as a crucial component of sequence stratigraphic theory. However, in lacustrine settings, the growth of deltaic clinothems and outlying deep-water fans remains comparatively poorly understood. In the southwestern Bozhong Sag, Bohai Bay Basin, China, both lacustrine deltas and outlying sub-lacustrine fans were developed during the Oligocene, providing an opportunity to investigate the connection between lacustrine deltaic clinothem growth and the formation of outlying sub-lacustrine fans in deep-lacustrine systems. We employ 3D seismic data, well data, core data, and sandstone grainsize data to analyze the stacking patterns and internal architectures of these two sedimentary systems in the lower and upper successions of our study interval, SQEd2L. In addition, elemental geochemical parameters were utilized to reveal the paleoclimatic signature of the different stratigraphic successions. Our results suggest that there are two main types of deltaic clinothem stacking patterns in the lower and upper successions of SQEd2L, respectively: (1) in the lower succession, progradational to aggradational stacking patterns have a flat to steeply rising rollover trajectory, and (2) in the upper succession, aggradational to progradational and degradational stacking patterns have a slightly rising to flat and slightly falling trajectory. Meanwhile, the sub-lacustrine fans with straight channels and thick lobe complexes are coupled with progradational and aggradational (PA) deltaic clinothems in the lower succession. In the upper succession, small-scale sub-lacustrine fans with sinuous channels and thin lobe complexes are coupled with aggradational to progradational and degradational (APD) deltaic clinothems. The sediment connectivity between lacustrine deltas and sub-lacustrine fans stands in stark contrast to their counterparts in marine basins (such as marine APD clinothems coupled with large-scale deep-water fans, while marine PA clinothems rarely produce deep-water fans). In addition, two contrasting paleoclimatic stages have been identified in SQEd2L, namely the earlier humid stage in the lower succession and the later semiarid climatic stage in the upper succession. A comprehensive analysis of the differences between lacustrine and marine basins indicates that climatic variations play a pivotal role in deep-lacustrine deposition. Consequently, a climate-cycle-driven, sediment-supply-dominated sedimentary model of delta-to-fan sediment connectivity is proposed that incorporates the efficiency of terrigenous sediment dispersal into deep-lacustrine floors and the architecture of sub-lacustrine fans. The findings of this study further refine the implementation of the sequence stratigraphy paradigm and enhance the understanding of delta-to-fan sediment connectivity in deep-lacustrine depositional systems.

Higher-order turbulent characteristics of sinuous alluvial river

Sinuous channels with movable banks were examined for flow patterns in laboratory experiments. The velocity, Turbulent kinetic energy (TKE) budget, TKE flux, and bursting events were analyzed to examine the turbulent flow behavior. Quadrant analysis is performed to determine the contribution of bursting events to Reynold shear stress. At the apex of the sinuous channel, quadrant analysis reveals a mixing of events. On the other hand, as the hole size increases, the contribution of events decreases. The TKE (turbulent kinetic energy) flux is greater near the riverbed and diminishes as it approaches the bed surface. The TKE flux is higher at the river bend's exit than at the entry point. Examining the TKE budget, the TKE production and TKE dissipation indicate that TKE dissipation surpasses the production near the riverbed and the surface. These terms are uniformly distributed and decrease as they approach the surface.

Long-term slope instability induced by the reactivation of mass transport complexes: An underestimated geohazard on the Norwegian continental margin

Submarine landslides are significant geohazards, capable of displacing large volumes of sediment from continental margins to deposit mass transport complexes (MTCs) and generate offshore tsunamis. However, the reactivation of MTCs after their initial failure has long been overlooked. By analyzing high-quality three-dimensional seismic reflection data and seismic attribute maps, as well as comparing the geometry of different MTCs, we investigate the development of long-term slope instability and its hazardous consequences on the northwest flank of the Storegga Slide on the Norwegian margin. Our results demonstrate that the reactivation of MTCs can deform both their inner structure and overlying strata, promoting the formation of sinuous channels and local slope failures on the seafloor. These findings further reveal the MTCs that are underconsolidated or comprise slide blocks may remain unstable for a long time after their initial failure, particularly when affected by slope undercutting and a corresponding reduction in lateral support. This study shows that MTC-prone sequences are more likely to comprise regions of continental slopes with long-term instability and recurring marine geohazards.

Mud retention in hydrologically closed basins promoted pre-vegetation meandering: evidence from the Neoproterozoic Diabaig Formation, Scotland

Abstract Fluvial point-bar deposits are described from the c. 1 Ga Diabaig Formation, representing some of the most compelling architectural evidence of planform sinuosity recognized in pre-vegetation sedimentary strata to date. The stratigraphical architecture of the deposits indicates different planform transformations in response to meander-bend expansion and downstream migration. Point-bar architectural motifs are locally abundant in the unit and this is attributed to elevated amounts of mud-calibre cohesive sediment. Mud afforded landscape stability that, together with limited stream power, was sufficient to corral sediment into single-thread, sinuous channels. Significant volumes of fine-grained sediment were encouraged to accumulate by the local basin setting of several topographically confined endorheic depressions. These conditions ceased once the hydrologically closed valleys were filled, with the overlying sandstone-dominated Applecross Formation subsequently deposited by low-sinuosity, braided rivers that bypassed fine-grained sediment oceanward. Other endorheic basins conducive to the formation of depositional meanders should be expected to have been relatively widespread on pre-vegetation Earth, though many individually limited in size, confined by their inherited topographies. Depositional architectures representative of sinuous channel planforms remain scarce within more extensive, externally drained basins.

Mud Could Have Made Meandering Rivers Long Before Plants Arrived

New evidence from 1.2-billion-year-old rocks suggests that single, sinuous channels could have formed in muddy floodplain sediments without the stabilizing help of vegetation.

A world-class example of a Late Palaeozoic glaciated landscape in Chad

Continental glacial deposits are rarely preserved in nature. Recent studies of the LPIA reveal the presence of periglacial deposits in Northern Chad covering an area of 20,000 km2. Using satellite maps, this project managed to examine the entirety of the Ennedi Plateau. 3D reconstructions of this mountain range reveal complex glacial morphological features. This paper presents large-scale subglacial features interbedded with proglacial fluvial features and discussed the variables at play during the progressive, repetitive, and perhaps cyclical nature of the Carboniferous glaciation. Using remote sensing techniques, this paper shows that there are three major ice advance–retreat cycles that led to the deposition of mega-scale glacial lineations with a complex fluvial channel belt. Palaeo-geomorphological mapping of satellite images in northern Chad reveals that the Late Carboniferous Chadian ice sheet covered at least 20,000 km2, a much greater extent than previously thought (ca. 6000 km2). Glacial lineations (GLs) are dominant and extensive on the plateau. They are arranged in widespread ice stream networks and developed at multiple stratigraphic levels. This broadly indicates palaeo-ice flow to the north. We report a newly discovered pristine channel belt, covering at least 300 km2 of a plateau in the Ennedi Plateau. A swarm of N–S trending channels, up to 250 m wide, is recognised. These are of both braided and meandering characters and are organised into channel belts of up to 500 m width. The mapped palaeo-morphology shows complex crosscutting relationships. The channel belt is intercalated with zones of GLs; hence, ice activity preceded and succeeded fluvial activity. Preserved planform sinuous channel geometries show distinctive point bar deposits and scroll bar geometries therein, which testify to a terrestrial, subaerial environment, rather than to their evolution in the subglacial realm, e.g. as eskers. Therefore, we find that cross-cutting, amalgamated channel systems record the complex phases of meltwater release during glacial retreat in the advance–retreat cycles of the Late Palaeozoic Ice Age in Chad.

Flow dynamics and sedimentation at a turbidity channel confluence in the Yinggehai basin, northwestern South China sea

Submarine channel systems transport vast amounts of terrestrial sediment into the deep sea via turbidity currents, however, there is a paucity of research detailing their dynamics, especially regarding the issue of how flows transport sediment and deposit at channel bends and channel junctions. From the analysis of core data, a high-resolution 3D seismic dataset, and local topography, a 3D numerical model is used to simulate the evolution of turbidity currents containing multiple size classes of sediments in the Late Miocene submarine channels in the Yinggehai Basin, northwestern South China Sea. The model solves the Reynolds-averaged Navier–Stokes (RANS) equations, the mass conservation equation, and the Exner equation for bed evolution caused by sediment entrainment and deposition. The results for the tendency of the total volumetric concentration of sediment in the turbidity current and bed thickness distribution reasonably match the infilled thickness of the channel interpreted from seismic data. The turbidity current in submarine channels is limited by the sloping topography and the channel geometry. Geochemical results show that, during the Late Miocene, sediments were derived from mixed sources. The simulation result accurately reveals the scope and magnitude of sediment contributions from each provenance. The confluence zone of the two channels (W and E) receives coarse-grained thick-bedded sediments via E channel flow transport showing a homogeneous distribution, a good hydrocarbon reservoir. This study improves our understanding of the processes of turbidity currents and their depositional characteristics within submarine channels, the reconstruction of their depositional environment, flow structures, spatial partitioning of sediment, and reservoir distributions within sinuous channels.

Updating Local Anisotropies with Template Matching During Geostatistical Seismic Inversion

Iterative geostatistical seismic inversion methods are widely used to predict petro-elastic rock properties from seismic reflection data. When the model perturbation technique uses two-point geostatistics, these methods struggle to reproduce complex and nonstationary geological environments such as faults, folds and highly variable depositional systems. These limitations are often due to the use of a global variogram model to express the expected spatial continuity pattern of the property of interest. In complex geological environments a global variogram model might be unable to detect local heterogeneities and rapid variations of lithology, and result in nonrealistic geological models. Local heterogeneities might be predicted from the data using seismic attribute analysis, which can be imposed during geostatistical seismic inversion as local anisotropy models. In these approaches, the information about the local spatial continuity patterns is fixed and will guide and condition the entire inversion procedure, which can lead to errors and uncertainty in areas where this approach is not appropriate due to high local uncertainty of geological features, given the poor signal-to-noise ratio of the data or the presence of important geological features below the seismic resolution. This work proposes an iterative geostatistical seismic inversion method which iteratively updates the local spatial continuity models based on the trace-by-trace misfit between observed and predicted seismic data. The update of the local spatial continuity models aims at surpassing the limitations of the seismic inversion methods that use a fixed a priori variogram model. The method is successfully illustrated in a challenging two-dimensional synthetic data set and in a real case application. The results demonstrate the benefit of updating iteratively the imposed local spatial continuity patterns based on the data misfit. The inverted models are capable of better predicting the location of faults and reproducing the continuity of sinuous channels.

Predicting Subsurface Architecture From Surface Channel Networks in the Bengal Delta

AbstractGroundwater is the primary source of water in the Bengal Delta but contamination threatens this vital resource. In deltaic environments, heterogeneous sedimentary architecture controls groundwater flow; therefore, characterizing subsurface structure is a critical step in predicting groundwater contamination. Here, we show that surface information can improve the characterization of the nature and geometry of subsurface features, thus improving the predictions of groundwater flow. We selected three locations in the Bengal Delta with distinct surface river network characteristics—the lower delta with straighter tidal channels, the mid‐delta with meandering and braided channels, and the inactive delta with transitional sinuous channels. We used surface information, including channel widths, depths, and sinuosity, to create models of the subsurface with object‐based geostatistical simulations. We collected an extensive set of lithologic data and filled in gaps with newly drilled boreholes. Our results show that densely distributed lithologic data from active lower and mid‐delta are consistent with the object‐based models generated from surface information. In the inactive delta, metrics from object‐based models derived from surface geometries are not consistent with subsurface data. We further simulated groundwater flow and solute transport through the object‐based models and compared these with simulated flow through lithologic models based only on variograms. Substantial differences in flow and transport through the different geologic models show that geometric structure derived from surface information strongly influences groundwater flow and solute transport. Land surface features in active deltas are therefore a valuable source of information for improving the evaluation of groundwater vulnerability to contamination.

Subglacial catastrophic-flood origin of linear and curvilinear flat-rimmed pit chains on Mars: Evidence from geomorphological mapping and detailed landsystem analysis

Flat-rimmed pits lacking emanating flow-like features on pit margins are typically clustered as linear or curvilinear chains on Mars. Their formation has been attributed to faulting, volcanism, or roof collapse of subsurface voids. Here we test these end-member models by conducting landform analysis and systematic geomorphological mapping in the central Tharsis region. Our work shows that the mapped flat-rimmed pit chains were formed on a lava-plain landscape that is mantled by a surficial meter-sized boulder layer. The flat-rimmed pit chains are closely associated with a landform assemblage consisting of localized pit-linking/terminating dendritic networks of gullies, U-shaped troughs, isolated sinuous channels, sinuous round-topped boulder-bearing ridges, and rampart craters. The absence of pit-bounding and pit-cutting faults rules out the faulting origin, while the lack of rubble-filled pit floors and erupting flow-like landforms does not favor the volcanic and roof-collapse mechanisms. When viewed together, the mapped flat-rimmed pit chains and their closely associated landform assemblage can be explained by a glacial-landsystem model: (1) pits were created by vortex-induced erosion during repeated, violent, catastrophic mega-flooding below a regionally extensive ice sheet possibly covering the entire Tharsis region (i.e., the Tharsis ice cap), (2) the subglacial floods exploited bedrock and/or ice sheet fracture sets resulting in linear and parallel chains, (3) localized pit-linking and pit-terminating U-shaped troughs and round-topped boulder ridges represent subglacial channel bodies including glacial eskers, (4) surficial boulders represent glacial deposits, (5) local trough-bounded pit chains resemble coulees and their hosted rock basins on Earth, and (6) rampart craters with viscous-flow ejecta deposits represent surface or near surface ice generated by the inferred glaciation. We suggest that the excavated pit material was transported by subglacial megafloods along the giant (>6000 km long) circum-Tharsis outflow channels to the outwash plains in the northern-hemisphere lowlands.

Effect of downward seepage on turbulence and morphology in mobile boundary sinuous channel

The porous boundary of alluvial channels allows water to interact with the surrounding groundwater. With reduction in groundwater level, transfer of water from the main channel to the groundwater is significant and referred to as downward seepage. The action of downward seepage causes morphological alteration along the sinuous alluvial channel. Laboratory experiments were conducted for no-seepage and seepage conditions to study the effect of downward seepage on turbulence and bed morphology in rectangular and trapezoidal sinuous channels. The deformation along the streambed and bank of the sinuous channels showed remarkable alterations with seepage. Downward seepage caused excess sediment transport in the sinuous channels showing high erosion along banks and streambed. With increased flow rate and downward seepage, prominent depositionalzones near inner region and erosion zones near outer region of the bend were observed in sinuous channel with rectangular cross section. Sinuous channel with trapezoidal cross section showed less morphological change as the side slope was almost equal to the angle of repose of the sand. However, with the application of downward seepage, the streambed of the channel has lowered in elevation, indicating sediment transport. Mean streamwise velocity at the center of the bend showed an average percentage increase in 26% in the rectangular channel and about 20% in the trapezoidal channel with downward seepage. The Reynolds shear stress estimated with downward seepage has increased near the channel bed, indicating high momentum flux. Higher bed shear stress was indicated near the channel bed with downward seepage, which results in downstream sediment transport.

Electrostatic deposition of TiO2 nanoparticles on porous wood veneer for improved membrane filtration performance and antifouling properties

Wood has been a promising water purifier material on account of its abundant natural transport channels, easy processing, and renewability, which is mainly focused on its utilization in growth direction for effective separation.Wood veneer manufacured from raw wood block has a reversed-tree pore structure, and possesses advantages of low cost, easy fabrication, material saving, and abundant sources. To realize its functionalization and practicable application for membrane separation, modification of wood veneer is prerequisite. Herein, thin wood veneer with disparate utilization direction of wood was developed to design filter membrane loading TiO2 nanoparticles for treatment of dye wastewater. Wood veneer with reversed-tree transport pathways exhibits unique porous structure, and filtering direction and wood growth direction is almost orthogonal generated numerous sinuous channels. Thereout, sufficient area for loading TiO2 nanoparticles and contacting pollutants as well as appropriate water transport pathways at significantly shrinking thickness of wood (the thickness of 0.2 mm) can be provide by these sinuous channels. TiO2 nanoparticles was first modified by (3-Aminopropyl)triethoxysilane with high positive charge, and immobilized on negatively charged wood surface through atmospheric impregnation via strong electrostatic attractive interaction. Vast quantities of exposed TiO2 nanoparticles on wood cell lumens significantly enhance the adsorption ability for dye contaminants, resulting in a high membrane separation performance. The flux of TiO2/wood veneer membrane can achieve high level of 636.94 L/(m2h) with considerable methylene blue removal of 99.9% at 0.01 MPa. Meanwhile, it shows good cycling stability as well as decent flexibility and excellent mechanical strength. Moreover, the designed membrane with photocatalytic function of TiO2 also displays impressive decontaminated and recycling ability. The flux can recover its pre-recession level after 10 h light irradiation. The designed TiO2/wood veneer with simple preparation process and excellent water treatment capacity exhibits promising results for practical wastewater treatment.

Flow Characteristics of a Sinuous Channel with Flexible Banks

Flow Characteristics of a Sinuous Channel with Flexible Banks

The influence of creeping slope failure on turbidity current behaviour

ABSTRACTErosional scars, slumps, slides and debrites (mass‐transport deposits) on submarine slopes form relief that influences turbidity current behaviour. However, the interaction of mass‐transport deposit emplacement kinematics (i.e. rapid emplacement versus creep), the morphology of the evolving seafloor topography and subsequent flow types is complicated. This study describes two outcrop examples of deep‐water, predominantly turbiditic, deposits overlying mass‐transport deposits, from the Eocene slope succession of the Aínsa Basin (Spanish Pyrenees). In both examples, the mass‐transport deposit substrate continued to creep contemporaneously with turbidity current deposition and bypass. In the first case study, structures in the mass‐transport deposits are extensional and oriented parallel to flow. In the second, structures are compressional and oriented perpendicular to flow. Mudstones dominate the slope succession, but deposits overlying mass‐transport deposits form sandstone‐prone accumulations. Lateral confinement by flow‐parallel extensional faults enhanced channel‐formation. Channel incision occurred close to the exhumed fault plane on the hangingwall. Incision ceased as the fault gradually locked‐up, and channels avulsed to the hangingwall of a newly active normal fault, while the abandoned channel was filled by a thinning and fining‐upward succession. Barriers formed where the long axes of compressional anticlines developed in mass‐transport deposits formed perpendicular to flow. Here, turbidites filled the bathymetric lows in the axes of synclines. Continued tightening of synclinal depocentres led to repeated stoss side trapping and upslope accretion of coarse‐grained sediment accumulation. This generated thickening and coarsening‐up, followed by thinning and fining‐upward successions, tracking the decreasing, then increasing flow bypass associated with topographic expression on the mass‐transport deposit. This study shows how post‐emplacement creep, and orientation of topographic features on mass‐transport deposits, influence the routing and deposition of contemporaneous turbidity currents, and illustrates examples of facies successions that could be misinterpreted as the product of other autogenic submarine slope processes, such as lateral migration of sinuous channels, or compensational lobe stacking.