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Introduction
Publications
Publications (387)
Sole structures on the base of turbidites, and other bed types, are typically classified into scour marks and tool marks, such as flutes, grooves, skim marks and prod marks. Yet, there are a range of other common sole marks that are unrelated to scouring or tools, and whose origin is poorly understood. Prominent among these sole structures are long...
We explored the settling dynamics of vertically aligned particles in a quiescent, stratified two-layer fluid using particle tracking velocimetry. Glass spheres of $d=4\,{\rm mm}$ diameter were released at frequencies of 4, 6 and 8 Hz near the free surface, traversing through an upper ethanol layer ( $H_1$ ), where H is height or layer thickess, var...
Large anabranching rivers form channels in sediments of varying strength, resulting from erosional and depositional processes that act over geological time scales. Although bank strength variability is known to affect channel morphodynamics, its impact on the migration of large sand-bed rivers remains poorly understood. We report the first in situ...
Fluvial islands are vital from both morphological and ecological perspectives and consequently have been hotspots of morphodynamic research in large rivers around the world. This study selected 14 representative fluvial islands in the lower reaches of the Yangtze River and explored their spatial-temporal evolution, including their shape and area dy...
Large rivers are characterized by large water discharges, high suspended sediment fluxes and low slope, and typically display multiple channels that are separated by large complex bars. The most common channel style found in these rivers is characterized by the alternating presence of single and multiple channel threads. Mid‐channel compound bars s...
Dunes are ubiquitous features in alluvial channels, serve as major agents of sediment transport and contribute significantly to flow resistance. Research in the past decade has illustrated the complexity of dune geometry and widespread occurrence of dunes that have a low leeside angle. However, there is a debate concerning the occurrence of such du...
River damming has brought great benefits to flood mitigation, energy and food production, and will continue to play a significant role in global energy supply, particularly in Asia, Africa, and South America. However, dams have extensively altered global river dynamics, including riverine connectivity, hydrological, thermal, sediment and solute reg...
We investigated experimentally the settling behaviour of vertically aligned spherical particles within various quiescent media at different release frequencies. The particles had a diameter of $d = 4$ mm and density of $\rho _s = 2200$ kg m $^{-3}$ , and were released near the free surface of water, ethanol, a G60 water–glycerine mixture (60 % glyc...
Climate change affects cryosphere-fed rivers and alters seasonal sediment dynamics, affecting cyclical fluvial material supply and year-round water-food-energy provisions to downstream communities. Here, we demonstrate seasonal sediment-transport regime shifts from the 1960s to 2000s in four cryosphere-fed rivers characterized by glacial, nival, pl...
Understanding of the formative conditions of many sole structures is limited, with chevron marks and striated groove marks being particularly enigmatic. These sedimentary structures are examined here through laboratory modelling. An idealized tool, resembling an armoured mud clast, was dragged through substrates of kaolinite–seawater mixtures of di...
Sand patches are one of the precursors to early-stage protodunes and occur widely in both desert and coastal aeolian environments. Here we show field evidence of a mechanism to explain the initiation of sand patches on non-erodible surfaces, such as desert gravels and moist beaches. Changes in sand transport dynamics, directly associated with the h...
Sand patches are one of the precursors to early stage protodunes and occur widely in both desert and coastal aeolian environments. Here we show field evidence of a mechanism to explain the initiation of sand patches on non‐erodible surfaces, such as desert gravels and moist beaches. Changes in sand transport dynamics, directly associated with the h...
This paper discusses the geological evolution of the Paraná River in Corrientes Province, located inside the Mesopotamic Argentine region, and reviews the principal geomorphological and hydro-sedimentological characteristics of this outstanding fluvial system.
Active lateral migration of the Paraná River inside its large alluvial fan, which covers...
The unsteady dynamics and induced turbulence associated with flow development of a fully-submerged canopy with relatively low flexibility were explored experimentally under small Cauchy numbers Ca≲9 using particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Inspection of the flow around a rigid canopy supported the identificati...
We conducted laboratory experiments to quantify the effect of low concentrations of clay, C∈[0,2]%, on turbulence in water-clay flows under nearly isotropic conditions using a novel approach. Full optical access was possible using Laponite RD™, a synthetic clay capable of producing clear suspensions of clay particles. Turbulence was generated in a...
The haor landscape is a wetland ecosystem in northeast Bangladesh, comprising shallow
depressions that undergo large changes in water inundation between the monsoon and dry seasons. Sediment
is supplied to the haor from rivers originating in the adjacent Shillong Plateau, and can adversely affect these
largely arable agricultural lands. The crit...
The haor landscape is a wetland ecosystem in northeast Bangladesh, comprising shallow depressions that undergo large changes in water inundation between the monsoon and dry seasons. Sediment is supplied to the haor from rivers originating in the adjacent Shillong Plateau, and can adversely affect these largely arable agricultural lands. The critica...
Flooding, already the largest hazard facing humankind, is becoming more frequent and affecting more people. Adapting to flooding must consider more than just water to encapsulate the effects of sediment movement, re-imagine flooding through a sociogeomorphic lens and expand approaches to knowing about floods.
Hydrothermal explosions are significant potential hazards in Yellowstone National Park, Wyoming, USA. The northern Yellowstone
Lake area hosts the three largest hydrothermal explosion craters known on Earth empowered by the highest heat flow values in Yellowstone and active seismicity
and deformation. Geological and geochemical
studies of eighteen...
Hydrothermal explosions are significant potential hazards in Yellowstone National Park, Wyoming, USA. The northern Yellowstone Lake area hosts the three largest hydrothermal explosion craters known on Earth empowered by the highest heat flow values in Yellowstone and active seismicity and deformation. Geological and geochemical studies of eighteen...
River dams provide many benefits, including flood control. However, due to constantly evolving channel morphology, downstream conveyance of floodwaters following dam closure is difficult to predict. Here, we test the hypothesis that the incised, enlarged channel downstream of dams provides enhanced water conveyance, using a case study from the lowe...
Poyang Lake in the Changjiang (Yangtze) River catchment has undergone frequent spring drought since 2003, and some researchers attributed this phenomenon to sand mining and the lakebed deformation in the outlet channel linking the lake with Changjiang River main channel. However, there is still a lack of high-resolution subaqueous geomorphological...
The distinct turbulence dynamics and transport modulated by a common seagrass species were investigated experimentally using a flexible surrogate canopy in a refractive-index-matching environment that enabled full optical access. The surrogate seagrass replicated the dynamic behaviour and morphological properties of its natural counterpart. The flo...
This paper quantifies changes in primary dune morphology of the mesotidal Lower Columbia River (LCR), USA, through ~ 90 river kilometres of its fluvial‐tidal transition at low‐river stage. Measurements were derived from a Multibeam Echo Sounder dataset that captured bedform dimensions within the thalweg (≥ 9m depth; H/Hmax ≥ 0.7) of the LCR main ch...
Bangladesh is dominated by three great rivers – the Jamuna–Brahmaputra, Ganga, and Meghna – that combine to feed sediment into one of the World's largest deltas in the Bay of Bengal. The Jamuna River has developed in a region of significant tectonic activity associated with Himalayan uplift and development of the Bengal foredeep. The bedload, altho...
Decimeterscale earlystage aeolian bedforms represent topographic features that differ notably from their mature dune counterparts, with nascent forms exhibiting more gently sloping lee sides and a reverse asymmetry in their flowparallel bed profile compared to mature dunes. Flow associated with the development of these “protodunes”, wherein the...
Sedimentary pyrite morphologies, spatial distribution relative to their spectral compositions were studied in carbonaceous shales (Fc) of the Mamfe Cretaceous Basin (MCB) in SW Cameroon. Lithofacies analysis of Fc reveals laminated (Fcl), oolitic (Fco), marlstone (Fcm), algal mat (Fca) and pelletoidal (Fcp) pyritized microfacies. Results of petrogr...
The Middle-Late Triassic Yanchang Formation, present in the large intracratonic Ordos Basin, is built of alternating sandstones, mudstones, and tuffs, representing a complete lacustrine cycle. Cores from wells in the south-western part of the basin show various types of soft-sediment deformation structures, particularly contorted lamination/bedding...
Dunes are the most prevalent bedform present in sand‐bedded rivers and their morphology typically comprises multiple scales of three‐dimensional topography. However, our understanding of flow over dunes is predicated largely on two‐dimensional models, a condition which is rare in nature. Here, we present results of Large Eddy Simulations over a sta...
Sand, gravel, and crushed stone are the most mined materials on Earth. Aggregates constitute the foundation for modern civilization and are essential for providing shelter, infrastructure, and communication, but are an increasingly scarce resource. Here, we review the interconnections between the impacts of aggregate mining and the services they pr...
Barchan dunes are crescent-shaped bedforms that form in aeolian (i.e., wind-driven) environments (including both Earth and other planets, such as Mars) as well as subaqueous environments. Under the forcing of the aloft turbulent boundary layer, they migrate downstream at a rate inversely proportional to their size, which results in complex interact...
This thesis investigates the planform response of proglacial fluvial systems to deglaciation, specifically in northwest North America. Increase glacier retreat is extremely widespread today, drawing our attention to proglacial environments. Fluvial systems are being directly impacted by increasing rates of glacier retreat, resulting in changes to
d...
A Correction to this paper has been published: https://doi.org/10.1007/s00445-021-01456-1
Although erosion during high-energy passage of a pyroclastic density current (PDC) causes great damage, analyses of the effects of such erosion are sparse in scientific literature compared to observations and interpretations of depositional processes. In this paper, we review observations of surfaces where PDCs have eroded sets of grooves that prov...
Despite an increasingly large body of work advancing our understanding of flow interactions occurring at the interface of a turbulent flow overlying a permeable bed, little is known concerning how such flow may be affected by the presence of biofilms, which exist in nearly all aquatic environments. This study quantifies the effects on flow exerted...
Multibeam backscatter strength can be used to characterize seafloor acoustic characteristics, and classify seabed substrate types. Herein, we use acoustic reflectance data to examine the distribution of manganese nodules in deep-sea substrates in a seamount region of the Western Pacific Ocean. Based on the multibeam backscatter strength, the backsc...
Hyperpycnal flows are river-derived extrabasinal turbidity currents transporting both sand and clay to lacustrine, coastal, shelf and deepwater sedimentary environments. Experimental research in the past twenty years has shown that the presence of clay in sediment-laden flows promotes a transitional behavior between fully turbulent flow and a quasi...
The Cambrian Mount Simon Sandstone has been the subject of extensive study and multiple industrial-scale carbon storage demonstrations at Decatur, Illinois, USA. The development of a reliable paleoenvironmental model is critical to successful large-scale carbon dioxide (CO2) storage, but is complicated by the need to interpret pre-vegetation sedime...
Current understanding of the role that dunes play in controlling bar and channel‐scale processes and river morphodynamics is incomplete. We present results from a combined numerical modeling and field monitoring study that isolates the impact of dunes on depth‐averaged and near‐bed flow structure, with implications for morphodynamic modeling. Numer...
Sediment gravity flows demonstrate a wide range of rheological behaviors, and past work has shown how transformations between flow types generate spatiotemporal changes in the resultant sedimentary successions. We used the geometrical characteristics of a single climbing ripple to demonstrate how such flows can transform from a turbulent to a quasi...
Purpose
Source apportionment is a crucial step toward reducing heavy metal (HM) pollution within soils. Although comparison of receptor models to apportion sources is well-established in air and water pollution, it has been poorly implemented in evaluations of soil pollution. This study aimed (1) to assess the accumulation of As, Cr, Cu, Ni, Pb, Zn...
Dune-scale cross-beds are a fundamental building block of fluvial-deltaic stratigraphy and have been recognized on Earth and other terrestrial planets. The architecture of these stratal elements reflects bed-form dynamics that are dependent on river hydrodynamic conditions, and previous work has documented a multitude of scaling relationships to de...
The world’s great rivers are threatened by a range of anthropogenic stresses - climate change being just one - that are driving a major sustainability crisis. As rivers react to these stressors, declining resilience makes them more vulnerable to extreme events, amplifying their effects and driving system change from which there may be no recovery....
The Ordos Basin, central China, is a large-scale Late Triassic intracratonic lacustrine basin, and in which the Upper Triassic Yanchang Formation comprises interbedded sandstones, mudstones and tuffs, representing deposits of a complete lacustrine life cycle. Based on observation of extensive well cores, various types of soft-sediment deformation s...
We provide evidence for a large-scale geomorphic event in Cambodia’s great lake, the Tonlé Sap, during the middle Holocene. The present-day hydrology of the basin is dominated by an annual flood pulse where water from the Mekong River raises the lake level by c. 8 m during the monsoon season. We present new subsurface geophysical data, allied to ne...
A novel flow facility developed to enable a broad spectrum of fluid mechanics experiments involving complex geometries and employing high-fidelity optical diagnostics is described in this paper. The development of the facility, which comprises two fully operational refractive-index-matched (RIM) flow tunnels, was guided by the ambition to overcome...
Experimental evidence of amplitude modulation in permeable-wall turbulence - Volume 887 - Taehoon Kim, Gianluca Blois, James L. Best, Kenneth T. Christensen
Flutes and tool marks are commonly observed sedimentary structures on the bases of sandstones in deep‐water successions. These sole structures are universally used as palaeocurrent indicators but, in sharp contrast to most sedimentary structures, they are not used in palaeohydraulic reconstructions or to aid prediction of the spatial distribution o...
Recent growth of the construction industry has fuelled demand for sand, with considerable volumes being extracted from the world’s large rivers. Sediment transport from upstream naturally replenishes sediment stored in river beds, but the absence of sand flux data from large rivers inhibits assessment of the sustainability of ongoing sand mining. H...
Dunes form critical agents of bedload transport in all of the world’s big rivers, and constitute appreciable sources of bed roughness and flow resistance. Dunes also generate stratification that is the most common depositional feature of ancient riverine sediments. However, current models of dune dynamics and stratification are conditioned by bedfo...
The three‐dimensional, crescentic morphology of a barchan dune induces secondary flows and a complex vortex structure in its wake. In scenarios where barchans are in close proximity to each other, the flow modifications introduced by the wake of the upstream barchan are important for understanding the morphodynamics of the downstream barchan. The r...
Depositional bedforms are rhythmic, morphological patterns on the Earth's and planetary surfaces that are generated by flow of a medium (e.g., water, air, ice) over a mobile sedimentary bed. These bedforms are ubiquitous in riverine, eolian, coastal and oceanic environments. The morphology of such bedforms interacts with their formative currents, c...
A study of bed morphology and hydrodynamics in the anabranching reach of the Solimões River upstream of the Negro/Solimões confluence was carried out using ADCP/Multibeam measurements as well as bed sampling and satellite images analysis. The analysis of ADCP data revealed that in high flow conditions, the main channel carried 80% of the total disc...
Sand and gravel are being extracted faster than they can be replaced. Monitor and manage this resource globally, urge Mette Bendixen and colleagues. Sand and gravel are being extracted faster than they can be replaced. Monitor and manage this resource globally, urge Mette Bendixen and colleagues. A labourer carries away large basket of wet sand tha...
The spatial coherence of turbulent flow structures throughout the flow field associated with a collision between a smaller upstream barchan laterally offset from a larger downstream barchan is investigated using inhomogeneous, two‐point correlation coefficients of fluctuating streamwise velocity, from which the distribution, size, and orientation o...
Turbulent flow overlying periodic arrays (cubic- and hexagonally-packed) of large hemispheres was examined experimentally. Flow in the vicinity of the individual roughness elements was successfully examined by conducting particle-image velocimetry measurements in a refractive-index matched flume where the refractive index of the working fluid match...
Spatial and temporal variability of river temperature, and its impact on sediment transport, is explored. Global river temperatures, computed daily using 1980–2010 climate, reflect latitudinal and seasonal variations in solar radiation, wind patterns, humidity, and water sources, and can be cooler or warmer than air temperatures. Subpolar, Polar an...
The landscape of southwest Bangladesh, a region constructed primarily by fluvial processes associated with the Ganges River and Brahmaputra River, is now maintained almost exclusively by tidal processes as the fluvial system has migrated east and eliminated the most direct fluvial input. In natural areas such as the Sundarbans National Forest, year...
In the version of this Review originally published, the author name ‘Arthington’ was misspelt in refs 216 and 218. Further, in the sentence that starts “Global warming has also been linked to potentially significant increases in the flow of Russia’s three great Artic rivers..”, ‘Artic’ should have been ‘Arctic’. These errors have now been corrected...
The period since the 1960s witnessed significant progress in our ability to decipher the clastic rock record from a wide range of sedimentary environments, and spanning many spatio-temporal scales, from millimetric to that of the sedimentary basin, and involving processes acting on timescales of seconds to millions of years. This review assesses ad...
The world’s big rivers and their floodplains were central to development of civilization and are now home to c. 2.7 billion people. They are economically vital whilst also constituting some of the most diverse habitats on Earth. However, a number of anthropogenic stressors, including large-scale damming, hydrological change, pollution, introduction...
Images from specially‐commissioned aeroplane sorties (manned aerial vehicle, MAV), repeat unmanned aerial vehicles (UAVs) surveys, and Planet CubeSat satellites are used to quantify dune and bar dynamics in the sandy braided South Saskatchewan River, Canada. Structure‐from‐Motion (SfM) techniques and application of a depth‐brightness model are used...
Velocity pulsing has previously been observed in continuous turbidity currents in lakes and reservoirs, even though the input flow is steady. Several different mechanisms have been ascribed to the generation of these fluctuations, including Rayleigh-Taylor (RT) instabilities that are related to surface lobes along the plunge line where the river en...
Results of high-resolution particle-image velocimetry (PIV) measurements are presented to explore how turbulent flow overlying a permeable wall is linked to the underlying pore flow and how their interplay is controlled by the topography of the wall interface and wall thickness. Two permeable walls were constructed from uniform spherical elements (...
The landscape of southwest Bangladesh, a region constructed primarily by fluvial processes associated with the Ganges and Brahmaputra Rivers, is now maintained almost exclusively by tidal processes as the fluvial system has migrated to the east through the Holocene. In natural areas such as the Sundarbans National Forest, year-round spring-tide inu...
Lithofacies analysis, optical microscopic and X-ray diffraction approaches were employed to investigate basin-fill configuration and palaeodepositional environments of the Mamfe Cretaceous Basin in SW Cameroon. The asymmetric basin-fill comprises six lithofacies associations whose vertical architectures are influenced by early syn-rift, mid syn-rif...
Barchan dunes are three-dimensional, crescent-shaped bedforms found in regions of unidirectional flow and limited sediment supply, and while most commonly associated with aeolian environments, they have recently been observed in subaqueous domains and on the surfaces of Mars and Titan. As barchans migrate in the direction of the flow, they interact...
Channel confluences are key nodes within large river networks, and yet surprisingly little is known about their spatial and temporal evolution. Moreover, because confluences are associated with vertical scour that typically extends to several times the mean channel depth, the deposits associated with such scours should have a high preservation pote...