Bed Sediment Research Articles

Evaluating the influence of seasonal stratification on mercury methylation rates in the water column and sediment in a contaminated section of a western U.S.A. reservoir

Mercury methylation frequently occurs at the active oxic/anoxic boundary between the sediment bed and water column of lakes and reservoirs. Previous studies suggest that the predominant mercury methylation zone moves to the water column during periods of stratification and that high potential methylation rates (Km) in sediment require oxygenated overlying water. However, simultaneous measurements of methylmercury (MeHg) production in both the sediment and water column remain limited. Understanding the relative importance of sediment versus water column methylation and the impact of seasonal stratification on these processes has important implications for managing MeHg production. This study measured Km and potential demethylation rates (Kdm) using stable isotope tracers of unfiltered inorganic mercury and MeHg in sediments and water of the littoral and profundal zones of a shallow branch of the Nacimiento Reservoir in California's central coastal range. Field sampling was conducted once during winter (well-mixed/oxygenated conditions) and once during late summer (thermally stratified/anoxic conditions). The results showed very high ambient MeHg concentrations in hypolimnetic waters (up to 7.5 ng L−1; 79% MeHg/total Hg). During late summer, littoral sediments had higher Km (0.024 day−1) compared to profundal sediments (0.013 day−1). Anoxic water column Km were of similar magnitude to Km in the sediment (0.03 day−1). Following turnover, profundal sediment Km did not change significantly, but water column Km became insignificant. Summer and winter sediment Kdm were higher in profundal (2.35, 3.54 day−1, respectively) compared to the littoral sediments (0.52, 2.56 day−1, respectively). When modelled, Km in the water column could account for approximately 40% of the hypolimnetic MeHg. Our modelling results show that the remaining MeHg in the hypolimnion could originate from the profundal sediment. While further study is needed, these results suggest that addressing methylation in the water column and profundal sediment are of equal importance to any remediation strategy.

Bullet impacts in building stone excavate approximately conical craters, with dimensions that are controlled by target material

Bullet impacts are a ubiquitous form of damage to the built environment resulting from armed conflicts. Bullet impacts into stone buildings result in surficial cratering, fracturing, and changes to material properties, such as permeability and surface hardness. Controlled experiments into two different sedimentary stones were conducted to characterise surface damage and to investigate the relationship between the impact energy (a function of engagement distance) and crater volumes. Simplified geometries of crater volume using only depth and diameter measurements showed that the volume of a simple cone provides the best approximation (within 5%) to crater volume measured from photogrammetry models. This result suggests a quick and efficient method of estimating crater volumes during field assessments of damage. Impact energy has little consistent effect on crater volume over the engagement distances studied (100–400 m), but different target materials result in an order of magnitude variation in measured crater volumes. Bullet impacts in the experiments are similar in appearance to damage caused by hypervelocity experiments, but crater excavation is driven by momentum transfer to the target rather than a hemispherical shock wave. Therefore in contrast to predictions of impact scaling relationships for hypervelocity experiments, target material plays the dominant role in controlling damage, not projectile energy.

Human-induced pollution and toxicity of river sediment by potentially toxic elements (PTEs) and accumulation in a paddy soil-rice system: A comprehensive watershed-scale assessment

This study aimed to assess pollution by potentially toxic elements (PTEs) in the Zarjoub and Goharroud river basins in northern Iran. Due to exposure to various types of pollution sources, these rivers are two of the most polluted rivers in Iran. They also play an important role in irrigation of paddy fields in the study area, increasing concerns about the contamination of rice grains by PTEs. Hence, we analyzed the concentrations of eight PTEs (i.e., As, Co, Cr, Cu, Mn, Ni, Pb, and Zn) at ten channel bed sediment sampling sites in each river, fifteen samples of paddy soils and fifteen co-located rice samples in the relevant watersheds. Results of the index-based assessment indicate moderate to heavy pollution and moderate toxicity for sediments in the Goharroud River, while both pollution and toxicity of the Zarjoub River sediment were characterized as moderate. Paddy soils in the watersheds were found to be moderate to heavily polluted by PTEs, but the values of the rice bioconcentration factor (RBCF) indicated intermediate absorption for Cu, Zn, and Mn, and weak and very weak absorption for Pb/Ni and As/Co/Cr, respectively. The concentration of Zn, Cu, Pb, and Cr was negatively correlated to the corresponding values of RBCF, highlighting the ability of rice grains to control bioaccumulation and regulate concentrations. Industrial/agricultural effluents, municipal wastewater, leachate of solid waste, traffic-related pollution, and weathering of parent materials were found to be responsible for pollution of the Zarjoub and Goharroud watersheds by PTEs. Mn, Cu, and Pb in rice grains might be responsible for non-carcinogenic diseases. Although weak absorption was observed for As and Cr in rice grains, the concentrations of these elements in rice grains indicate a high level of cancer risk if ingested. This study provides insights to control the pollution of sediment, paddy soils, and rice.

GAIA - a unified framework for sediment transport and bed evolution in rivers, coastal seas and transitional waters in the TELEMAC-MASCARET modelling system

In rivers, coastal seas and transitional waters, sediment transport processes involve a variety of interacting factors that dynamically vary over time and space. The flow dynamics within these highly heterogeneous natural systems influences the spatial patterns of erosion and deposition of the bed sediments, which in turn shapes and conditions the bottom morphology. By taking advantage of the established modelling framework in both two- and three dimensions for unstructured meshes proposed within the Telemac-Mascaret system, the new module Gaia provides a code structure for solving sediment transport and morphological evolution problems. By a clear treatment of sedimentary processes that happen in the water column, in the bed structure, and at the water–bed interface, Gaia efficiently manages the spatial and temporal variability of sediment size classes, properties and transport modes for two- and three dimensions. In addition, this module can easily be expanded and customised to particular requirements by modifying user-friendly, easy-to-read, and well-documented FORTRAN-90 subroutines.

The Rance tidal power station: Toward a better understanding of sediment dynamics in response to power generation

A three-dimensional coupled hydrodynamic and morphodynamic numerical model was developed to analyze sediment dynamics in the Rance estuary, in response to the tidal power station (TPS) built near the mouth in the 1960s. The Rance estuary is a relatively small low-discharge steep-sided ria, located along the Brittany coast in northern France, with a maximum spring tidal range of 13.5m. Taking advantage of this significant tidal regime, the first and currently the second largest operational tidal power station in the world was built at the estuary’s mouth, with peak output capacity of 240MW. After calibration and validation of the model for present-day conditions, suspended sediment concentration (SSC) and bed level evolution were evaluated at tidal and fortnightly scales for different scenarios, with and without TPS. Peak SSC are reached during spring tides and specifically during the estuary’s infilling (flood) stage where both turbines and sluice gates are open. Unbalanced with sediment transport during ebb, sediments are accumulated in the main channel of the upper estuary. Under natural tidal forcing (i.e., without TPS), simulations show that an estuarine turbidity maximum forms in the upper estuary, and sediment deposition is significant. However, sedimentation rates are two times lower than those observed in the presence of the TPS. A possible alternative for reducing sediment accumulation in the upper estuary would be the opening of sluice gates simultaneously with the turbines during falling tide, to enhance ebb currents that would allow particles transport towards the estuary’s downstream.

Experimental study of sediment washout from stormwater sumps.

Sumps are commonly used in urban stormwater systems, which can be considered as a simple pretreatment device for stormwater quality control. However, they may function as pollution sources due to sediment washout under high flow conditions. An experimental study was conducted to investigate the scour process of predeposited sediments from a sump and its influencing parameters. Under conditions with large inflows or high sediment deposit, the sediment particles could be resuspended, entrained and flushed out. The washout mass decreased exponentially with time if the sediment bed surface depth was larger than a threshold value; otherwise, the amount of washout would be much smaller. The same scour pattern was observed for all the testing cases, of which the largest scour depth always occurred below the outlet. The deposit below the inlet might increase under conditions with high flow rates and low levels of sediment bed. Dimension analysis was performed and principal non-dimensional parameters were found, including the Péclet number, the pipe Froude number, and the dimensionless particle diameter, which can be used to determine whether the washout would occur and its intensity in a stormwater sump under given conditions.

Performance evaluation of constructed wetland for removal of pharmaceutical compounds from hospital wastewater: Seasonal perspective

Constructed wetland employs vegetation as a natural medium to remove pollutants from wastewater for this treatment. It is eco-friendly, sustainable, economical, low maintenance, low running cost, and easy to use. This has prompted several studies to investigate its performance in treating pollutants from the conventional to emerging contaminants category, including pharmaceutical compounds. However, there is still a lack of work on the impact of monsoons on the removal efficiency of pharmaceutically active compounds from wastewater. This study evaluated constructed wetland performance during the premonsoon, monsoon, and post-monsoon seasons. A pilot-scale constructed wetland setup was established to conduct this study. The target compound included paracetamol, ibuprofen, carbamazepine, lorazepam, ciprofloxacin, sulfamethoxazole, and Fluvastatin. In the constructed wetland, for paracetamol and ibuprofen, NSAIDs concentration was observed to be 1503–6307 ngL−1 and 564–808 ngL−1. The concentrations of antibiotics, sulfamethoxazole, and ciprofloxacin were 16532–21635 ngL−1 and 734–1178 ngL−1, respectively. The carbamazepine, lorazepam, and Lutvastatin concentration range was 616–906 ngL−1, 2742–3775 ngL−1, and 694–2068 ngL−1, respectively. The hazard quotient approach was adopted to evaluate potential environmental risk from target compounds. The increase of paracetamol 33 %, ibuprofen 94 %, ciprofloxacin 242 %, Sulfamethoxazole 64 %, and carbamazepine 77 % validated the study hypothesis. However, a decrease of 15 % lorazepam and 43 % Fluvastatin inferred that dilution was inversely proportional to the removal of these compounds. The seasonal removal efficiency was in order pre-monsoon < post-monsoon < monsoon. Hospital wastewater had HQ values of 90, 100, and 130 for premonsoon, monsoon, and post-monsoon, respectively. After treatment from the constructed wetland, the wastewater effluent had reduced HQ value to 53, 35, and 70 for premonsoon, monsoon, and post-monsoon periods respectively. The HQ values were further reduced in tubesettler to 22, 11, and 28. Ciprofloxacin posed no significant risk. However, sulfamethoxazole posed a high risk during premonsoon, monsoon, and post-monsoon season. Further works are required to analyze the removal mechanism through plant uptake, sediment bed, and biodegradation for a different season or climatic condition to present the real-time performance of constructed wetlands for treating wastewater loaded with pharmaceutical compounds.

Geochemistry of uranium in the Ganga (Hooghly) River estuary, India: The role of processes in the water column and below the sediment-water interface

In this study, we discuss the cycling of uranium (U) in the Ganga (Hooghly) River estuary through investigation of the composition of the water samples of six periods of contrasting water discharge, the bulk and exchangeable phases of the coexisting suspended particulate matter (SPM) and the bed sediments. In addition, we evaluate data on urban and industrial effluent waters that drain into the estuary. Similar U concentrations of freshwaters and effluent waters do not indicate the anthropogenic source to be an important contributor of U to the estuary. The removal of dissolved U in the low-salinity zones, observed for five of six study periods, is primarily linked to the cycling of the FeMn oxyhydroxide phases. The compositions of exchangeable phases of SPM provide supportive evidence for the removal of dissolved U. Mass balance calculations show that the degree of removal of dissolved U can be sustained by the observed enhancement of exchangeable U in the SPM. Loss of U from the bed sediments is inferred from the distributions of exchangeable U concentrations as a function of salinity. Multiple observations based on compositions of the exchangeable and bulk phases of bed sediments indicate mobilization and loss of both U and Mn through suboxic diagenesis in the sediment columns followed by tidally-induced sediment resuspension.We estimate that 40–60% of riverine U is removed in the low-salinity zone during the monsoon and post-monsoon periods. More importantly, the salinity range over which U removal occurs varies between the periods of similar water discharge. The estimated U flux from the estuary is ∼70% higher in 2012 than in 2013. A significant difference between the annual U fluxes, driven mainly by considerable variation in the magnitude of U removal, suggests that estimates of meaningful annual U fluxes would require data at higher temporal resolution. This study highlights the importance of processes operating in the water column and below the sediment-water interface in the cycling of U in the Hooghly River estuary, where the solute-particle interaction driven by high SPM load is known to influence the cycling of trace metals.

Numerical simulation of impact and entrainment behaviors of debris flow by using SPH–DEM–FEM coupling method

Abstract Increasing rain levels can easily destabilize and destroy particulate matter in mountainous areas, which can cause natural disasters, such as debris flow and landslides. Constitutive equations and numerical simulation are the theoretical bases for understanding the behavior of these disasters. Thus, this study aimed to investigate the impact of the debris flow and its entrainment behavior on gully bed sediments. We adopted a coupled analysis method based on elastic–plastic constitutive equations by considering the elasto-plasticity of slurry and the elastic characteristics of debris materials. The coupled method consisted of smooth particle hydrodynamic (SPH), discrete element method (DEM), and finite element method (FEM) (SPH–DEM–FEM). SPH particles represented fluid, DEM particles denoted solid immersed in fluid, and FEM elements represented the terrain and structures. The coupling analysis model was used to simulate the coupling contact of solid, liquid, and structures and to describe the entrainment behavior between solid and liquid phases. The model feasibility was verified by comparing the basic simulation results with experimental values of the dam break model and the rotating cylindrical tank model. The coupled model was then combined with the data management and modeling of geographic information system to simulate the 2010 Yohutagawa debris flow event. Finally, we explored the influence of debris shape-related parameters on the debris flow erosion entrainment process.

Effect of sediment gradation on scour by symmetric crossing jets: an experimental investigation

Abstract A laboratory study with 162 experiments was designed and conducted to investigate the effect of three non-uniform sediment samples on the scour morphology by the symmetric crossing jets. The bed sediment materials with close median diameter values and different non-uniformities were utilized to investigate the scour at various crossing angles. The results were also compared with the equivalent single jet. The proper novel relationships were presented to predict the scour hole depth, and dimensions. The results showed that at a crossing angle of 30° with low and medium tailwater depth, the scour depth increases with increasing the non-uniformity of the bed materials. At the crossing angle of 30°, the armor layer was created perfectly that was thick on the bottom of the scour hole, but for the crossing angles of 70° and 110° it was thin and was a mixture of the coarse and fine particles. At low tailwater depth at the crossing angles of 70° and 110°, by increasing the non-uniformity of the sediments, the scour tended to be more asymmetric. At the high tailwater depth, for the crossing angles of 70° and 110° the scouring was less than that of the crossing angle of 30° and single jet.

Optimized Screening Methods for Investigation of the Larval Settlement of Lanice conchilega on Artificial Substrates

The Belgium sandy coastline is very vulnerable to erosion; therefore, development of sustainable and nature-based coastal protection solutions is important. Enhancing the settlement of the ecosystem engineer Lanice conchilega (Pallas, 1766) which stabilises the sediment bed, is a possible solution. In order to enhance larval settlement by artificial substrates in the field, efficient methodologies are required to screen a wide range of artificial substrates and measure how they influence currents and larval settlement. Therefore, in this study, we describe the development of innovative artificial substrate screening methodologies using an optimised recirculating aquaculture system (RAS) by: (1) analysing the capture rate of passively floating plastic particles, (2) measuring current velocity by means of an acoustic doppler velocimeter and (3) monitoring settlement of living L. conchilega larvae. Of the eight substrates evaluated, one was proven to significantly enhance the settlement of L. conchilega, namely Geotextile 3D knitted fabric with PES knit, PA spacers and wood sticks mounted at a density of 680 sticks/m2. The results of this study show that controlled lab conditions, in conjunction with innovative methods, allowed for successful screening of a number of substrates in a short time in terms of their ability to enhance larvae settlement.

Torpedo pile penetration by combined water jet and mechanical vibrations in cohesive sedimentary beds

The penetration efficiency and safety of piles on the seabed affect the cost of offshore structures and the reliability of relevant equipment, which entails to the success or failure of the development and utilization of ocean resources. However, the traditional methods of pile penetration, including pressing method, impact driving method and vibro-driving method, are difficult to adapt to the complex marine environment. In this study, the torpedo pile penetration in cohesive sedimentary bed was investigated by applying downwardly directed vertical water jet and mechanical vibrations. The experimental work was developed in the laboratory through a series of pile penetration tests in different types of cohesive sediments. During the penetration processes of the torpedo pile, the relevant influencing factors such as water content of cohesive sediment, vibration intensity and water jet velocity were considered. The experimental results show that the penetration depth of the torpedo pile increases with the increase of water jet velocity, vibration intensity and water content of cohesive sediment. Based on the dimensionless analysis and data regression, a formula for the critical penetration depth of the torpedo pile in cohesive sediment is proposed, which is correlated with the water jet velocity and vibration intensity, as well as the torpedo pile and soil properties. In addition, the formula is verified by the experimental data of other study, which presents good consistency.

Applying geochemical and colour properties to quantify sediment sources in a Brazilian semiarid ephemeral river system

• The Brazilian semiarid is the most densely populated dry region in the world. • Sediment source apportionment was quantified in a semiarid ephemeral catchment. • The combination of conventional and alternative tracers improved source discrimination. • Our results may gain high visibility given the climate change projections for the semiarid regions. The Brazilian semiarid is the most densely populated dry region in the world. Although climate change projections underline the need for the creation of integrated strategies to protect water resources in the semiarid, sediment source apportionment data remain scant for this environment. Accordingly, we evaluated sediment source contributions in one of the most relevant Brazilian semiarid catchments by combining geochemical and colour tracer properties. In doing so, we explored the applicability of colour tracers as a low-cost alternative to the use of time-consuming and costly properties, such as geochemical tracers. Two source classification schemes were used based on environmentally contrasting regions within the catchment (upper, middle and lower catchment parts) and land use (Caatinga biome - natural vegetation, unpaved roads, and channel banks). Suspended sediments (SS) and bed sediments (BS) were used as target sediment. A total of 660 individual source material samples were collected and composited. Geochemical and colour tracers were measured on the source and target sediment samples and used as potential fingerprints to discriminate and quantify the sediment source contributions. The geochemical tracers provided weak source discrimination based on land use. However, combining geochemical and colour tracers improved the final outputs. Using the MixSIAR model, the lower catchment contributed more sediment than the other regional sources. The Caatinga (SS = 49 %; BS = 47 %) contributed more sediment than channel banks (SS = 35 %; BS = 39 %). Overall, our results suggest that the recovery and conservation of the Caatinga vegetation and the stabilization of channel banks, especially in the lower catchment part, are critical for improving sediment supply control in the semiarid study basin. More studies are needed to evaluate the conservative behaviour of colour tracers in ephemeral rivers.

Morphodynamics of vortex ripple creation under constant and changing oscillatory flow conditions

The morphodynamics of orbital vortex ripples due to oscillatory flow and induced sediment transport was studied numerically. The methodology was based on large-eddy simulations of the full coupling of turbulent oscillatory fluid flow, bed and suspended sediment transport, and bed evolution. The Immersed Boundary method was implemented for the imposition of fluid and sediment boundary conditions on the mobile bed surface. Results are presented for ripple creation starting from flat or rippled beds, as well as results of ripples adapting to changing flow (wave) direction. The computed equilibrium ripple dimensions are in agreement with existing empirical predictions; however, the computed ripple profile is not as steep in the vicinity of the ripple crest as the analytical one in Sleath (1984). The time needed for the bed geometry to reach equilibrium, in cases where the initial bed is almost flat or it is formed by ripples that shorten towards equilibrium, is longer than in cases where the initial bed is formed by ripples that widen towards equilibrium. Moreover, the ripple crests are reoriented when the flow changes direction by 45°; the new equilibrium ripple crestline is perpendicular to the flow direction. Finally, the numerical results are compared with corresponding results of flow above fixed ripples. The bed load flux does not present substantial differences between the fixed and mobile bed cases. On the contrary, a strong increase of the suspended load flux is observed for the mobile bed case in comparison to the fixed bed case. • LES Coupling between oscillatory flow, sediment transport, and bed morphodynamics. • Same flow forcing results into same bed equilibrium regardless of initial bed form. • Evolution of ripples longer than equilibrium ones is slower than for shorter ones. • Ripples are reoriented perpendicular to the flow direction. • Suspended load over mobile rippled bed is larger than over fixed ripples.

Transport and accumulation of plastic particles on the varying sediment bed cover: Open-channel flow experiment.

Contamination of sea bottom sediments by microplastics is widely confirmed, but the reasons for its patchiness remain poorly understood. Laboratory experiments are reported where combined sets of various plastic particles, different by shape, size, density, and flexibility, were transported by the step-wise increasing open-channel flow over the bottom covered with natural sediment of increasing grain size. For every particular flow velocity, observations revealed the recurrent formation of relatively narrow retention areas, where plastic particles lingered for some time in their motion. These areas follow the line of change of the sediment type from finer to coarser grains. It is shown that contact friction drives the retention of a particle at finer sediments, while particle/sediment-grain interaction becomes of importance when particles and sediment grains are of similar sizes. The presence of this effect can be expected for a relatively wide range of natural conditions.

On the abundance and occurrence of the mangrove crabs, Scylla spp. (Crustacea: Portunidae) from Munjang mangrove, Bangka Belitung Island

The mangrove ecosystem is one of the most productive ecosystems on earth. This ecosystem provides a lot of functions for the living organism inhabiting here, such as fishes, mollusks, echinoderms, crustaceans, ect. The mangrove crab is one of the common crustaceans that can be found in the mangrove. This Purtunidae crab is very popular due to their role in the food chain as well as for the economic income that has a high value in the market. However, overexploitation may decrease the crab population. This study aimed to investigate the abundance and occurrence of the mangrove crabs from Munjang mangrove, Bangka Belitung Island from August 2020 to June 2021 using baited traps with the line transect method at four zones. A total of four species of mangrove crabs, Scylla olivacea, S. paramamosain, S. serrata and S. tranquebarica, were found in this location and dominated by S. serrata. Shannon diversity index (H’) was a in low category (&lt;1), evenness index range (J) from 0.35 to 0.89, and there was dominant species in this study. The bed sediment iswas dominated by the muddy clay substratum except in zone 4 with sandy. Overall, this location is a suitable habitat for the Scylla spp. And better management is urgently needed before these crabs are exploited by humans.

Natural and anthropogenic contributions to the elemental compositions and subsequent ecological consequences of a transboundary river's sediments (Punarbhaba, Bangladesh)

An anthropogenically less affected transboundary river (Punarbhaba, Bangladesh) was studied to detect associated risks from the combined origin(s) of geochemically and toxicologically significant elements in benthic sediments. A total of 30 river bed sediments were analyzed by instrumental neutron activation analysis targeting the 15 chemical elements viz., Na, Al, K, Ti, Cr, Mn, Co, Zn, As, Rb, Sb, Cs, Ba, Th, and U. Among the estimated elements, the mean abundances (μg/g) of Rb (136), Sb (0.66), Cs (6.66), Th (14.6), and U (3.92) were 1.4–1.7 times higher than the crustal origin. These elements are primarily responsible for the contaminated state of the Punarbhaba River. The studied area is ‘moderately polluted’ (Igeo: 2.01 to 0.02) and possesses ‘minor enrichment’ (EF: 1.98 to 0.48) in terms of the measured elements. The output of statistical analyses projected that the studied elements are geochemically fractionated in an oxidizing environment (U/Th = 0.44) and mostly originated from felsic sources, thus confirming the mineral is comprised of aluminosilicates and alkali feldspar. However, SQGs-based and ecological risk indices invoked minor (Cr: 6.67%) to no potential ecotoxicological threats for Cr, Mn, Co, Zn, As, and Sb. Nonetheless, altered distribution patterns caused by geogenic activities increased Cr and Zn in the environment which may cause toxicity (Cr: 22–53%, Zn: 35–70%), and pose potential ecological risks, specifically in upstream locations (P-2, P-3, P-5). Further, this study broadened the perspective of sediment deposition from fractionation, fluvial transportation, and weathering events beyond the industrial disintegration of elements, which will aid researchers and policymakers to comprehend combined risks from suspended sediments.

Local scour of cohesive sediment bed at the pile subjected to lateral vibration

In this study, the local scour of cohesive sediment bed at the pile subjected to lateral vibration was investigated experimentally. The experiments were carried out in a unidirectional free-surface flow channel in the laboratory. The findings of the experiments indicate that lateral vibrations produce significant effects on local scour of the bed at the pile, and the effects are completely different for non-cohesive and cohesive sediment bed. For non-cohesive sediments, the equilibrium scour depth decreases with the increase of vibration intensity. On the contrary, for cohesive sediments, the equilibrium scour depth increases with the increase of vibration intensity, and there appears a peak and plateau, which may be attributed to the shear-thinning behavior of cohesive sediments near the pile under vibration loadings. Cohesive sediments around the pile are fluidized by vibration, so that the cohesive force among sediment particles decreases, resulting in larger local scour. An empirical formula for estimating equilibrium local scour depth at pile foundation subjected to lateral vibration is proposed and tested using reported data and data obtained in this study.

Footprint beds record Holocene decline in large mammal diversity on the Irish Sea coast of Britain.

Long-term monitoring along the Irish Sea coast of Britain at Formby has identified hundreds of animal and human footprints in 31 discrete sediment beds. A new programme of radiocarbon dating shows that the Formby footprints span at least 8,000 years of the Holocene Epoch from the Mesolithic period to Medieval times. In a landscape largely devoid of conventional archaeology and faunal records, we show how species data from the footprint stratigraphy document long-term change in both large mammal diversity and human behaviour. The footprint beds record shifting community structure in the native fauna through an era of profound global change. As sea levels rose rapidly in the Early Holocene, men, women and children formed part of rich Mesolithic intertidal ecosystems from ~9,000 to 6,000 cal BP, with aurochs, red deer, roe deer, wild boar, beaver, wolf and lynx. Doggerland was reclaimed by the sea in this period. In the agriculture-based societies that followed, after 5,500 cal BP human footprints dominate the Neolithic period and later beds, alongside a striking fall in large mammal species richness. Stacked footprint beds can form multimillennial records of ecosystem change with precise geographical context that cannot be retrieved from site-based fossil bone assemblages.

Appendicular osteology of Skorpiovenator bustingorryi (Theropoda, Abelisauridae) with comments on phylogenetic features of abelisaurids

Skorpiovenator bustingorryi is a derived abelisaurid theropod represented by a fairly complete skeleton from the Late Cretaceous sedimentary beds of north-western Patagonia. Although some features were described in the original paper, mainly related to the skull, the appendicular anatomy remains undescribed. The aim of the present contribution is to provide a detailed description and analysis of the available appendicular bones, including comparisons with other ceratosaurian theropods close to Skorpiovenator. In this way, new autapomorphies emerged to further distinguish Skorpiovenator from its relatives. Furthermore, a comprehensive phylogenetic analysis was performed and several characteristics of the hind limb, in particular some of the autopodium, resulted in the identification of new apomorphic traits for Ceratosauria and Abelisauridae. These features might prove to be useful for future phylogenetic analyses and may help to resolve the still confusing and debated internal relationships of abelisaurid theropods.