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A GPU-accelerated 3D smooth particle hydrodynamics (SPH) scheme is developed and applied to a coastal multi-phase liquid-sediment interaction and sediment transport. The SPH scheme's meshless design and the sediment's particle structure enable the modeling of the waves' interactions with the sediment particles beyond the limitation of the mesh-based methods. A Newtonian constitutive model is used to model the liquid phase, and the sediment transport is formulated based on the Herschel-Bulkley-Papanastasiou (HBP) model. The yield characteristics of the sediment phase are estimated using the Drucker-Prager yield criterion. Due to the parallelization of the solution on graphics processing units, the 3D SPH scheme's performance, which uses millions of particles, is improved. Good correlations were observed in the SPH predictions and experimental measurements, with a maximum difference of 4.85 %. The validated scheme is applied to formulate forecasting models for the coastline sediment transport. It is found that erosion and scouring are expected at the coastline region inclined to the direction of the sea waves, with a predicted mass erosion of about 60e3 kg in four years. The wave's velocity is also established to be directly proportional to the sediment transport. The proposed multi-phase SPH methodology is proven effective for sediment transport prediction. • PIV and 3D SPH approaches are developed to study the morphodynamics variables of a coastal liquid-sediment system. • The approaches are applied to analyze the multi-phase liquid-sediment interaction phenomenon of the coastline. • The findings of the presented SPH model show good correlation with those of the PIV experiment. • The ability of the presented method to investigate the coastline sediment transport is demonstrated. • Forecast models are formulated for predicting the coastline sediment transport as a function of time and wave velocity. [ABSTRACT FROM AUTHOR]

Exploring overland flow resistance and sediment delivery capacity under different landscape vegetation conditions is critical for better understanding hydrodynamic mechanisms of soil erosion processes and hydrological connectivity on hillslopes. To evaluate flow resistance relations and sediment transport for landscape vegetation coverage and combinate effect of vegetation patches, field simulated rainfall experiments were conducted using a series of overland runoff and sediment transport rates in 3 m (L) × 2 m (W) experimental plots with coverages of 0%, 20%, 40%, 60% and 90% in a uniformly distributed condition and composited flow paths of different patches (horizonal path, vertical path, random patches and S-shaped path) in the same coverage (40% and 60%). The runoff rates for the grassland with coverages of 20–90% were decreased by 19.3–61.4% (P < 0.05), and the sediment concentrations were reduced by 81.7–97.8% (P < 0.05) compared to the bare land. The Darcy-Weisbach resistance coefficient doubled and the stream power declined by 60.0% when grassland coverage increases to 90%. The runoff rates varied little among the conditions of horizontal, vertical, random and S-shaped flow paths at the coverage of 60%, while the rate apparently reduced by 34.1% (P < 0.05) when the vertical flow path became horizontal under the same coverage of 40%. The sediments for poorly connected flow paths could reduce sediment >90% either on high-coverage or low-coverage grassland. Our field experiments confirmed that the increase of vegetation coverage and the combination of landscape patches could significantly reduce runoff rates, sediment yields and flow velocities, increase surface roughness, promote flow resistance and diminish hydraulic shear stress and the stream power. The poorly-connected paths (horizontal and random) exhibited a stronger flow resistance and weaker sediment transport capacity than the well-connected paths (vertical and S-shaped). • The runoff and sediment are considerably decreased with the coverage increasing. • The flow resistance to runoff is enhanced by poorly connected flow paths. • The sediment transport is significantly influenced by the different flow paths. • The sediments for poorly connected flow paths could reduce sediment >90%. [ABSTRACT FROM AUTHOR]

Abstract The complex interactions between flow hydrodynamics, sediment transport, geometry, and changes in base level control the morphodynamic evolution of tidal channels, inlets, and estuaries. Research on these complex settings have involved decades of field, laboratory, and modeling work. Studies on the one-dimensional morphodynamic of well-mixed, tide-dominated channels demonstrate that the evolution of a horizontal channel subject to tidal fluctuations at the ocean boundary is characterized by erosion in the ocean part of the channel and the formation of a landward migrating shoal that, depending on the channel length, may reach the landward boundary. When the shoal reaches the landward end of the domain, it is reflected and a beach forms as the flow and sediment transport reach conditions of equilibrium. At equilibrium, the elevation of the channel bed profile remains constant over a tidal cycle. Building on previous work, this study focuses on the poorly explored effects of nonuniformity of the sediment size distribution and of the interaction between tidal channel and longshore sediment transport on the equilibrium of tidal channels. The model is verified at laboratory scale, and it is then applied to predict equilibrium conditions with nonuniform sediment and without an imposed input of sediment from the ocean. Model results show that nonuniformity of the grain size distribution of the sediment increases the profile concavity. The equilibrium deposits tend to coarsen from the land to the ocean, and the sediment of the landward deposits presents an upward fining pattern. When the imposed input of sediment from the ocean is relatively small, the equilibrium profile presents a stable shoal at the oceanward part of the channel. In the case of a large input of sediment from the ocean, the channel gradually fills with sediment. The grain size distribution of these channel fill deposits coarsen in the oceanward and upward directions. The comparison between model results and field observations shows that the model can qualitatively capture some of the main features of tidal channels and can thus be of aid in coastal management and restoration with proper site-specific modifications. Highlights • The non-uniformity of the sediment and its caliber play a prime control on estuarine morphodynamics; • Estuarine morphodynamics strongly depends on the interaction between the tidal channel and the longshore sediment transport. • A 1D model of a tidal channel can capture some characteristics of tide dominated estuaries. • The combination of sinusoidal tidal forcing and constant input of sand from the ocean results in cyclic deposition. [ABSTRACT FROM AUTHOR]

Posidonia oceanica plays a significant role in the stabilization and protection of the coast in Gulf of Giens. Unfortunately, its distribution has been declining remarkably due to both anthropogenic interventions and natural factors. The present study focuses on the numerical simulation of the presence of Posidonia as well as the influence of its disappearance on hydrodynamics and sediment transport along Alamanarre beach. The model results indicate that the regression of Posidonia leads to significant changes of the hydrodynamic parameters, sedimentation rates, and causes severe erosion along Almanarre beach. In the annual wind conditions, the mean current speed is increased by 50.38%–80.65%, the mean significant wave height increased by 14.03%–16.58%, and the total load of sediment increased by 252%–426%, in absence of Posidonia. Regarding the seasonal wind variation, the disappearance of Posidonia induces an increase of the mean current speed about 52.86%–58.34%, the mean significant wave height by 8.23%–11.27%, and sediment transport rate by 358.99%–394.53%. Under the impact of extreme events with the disappearance of Posidonia, the mean current speed, the mean significant wave height, and the sediment transport rate increase by 12.53%–58.48%, 23.91%–34.67%, and 65.15%–154.62%, respectively. [ABSTRACT FROM AUTHOR]

In this study, we modified and applied an open source CFD software package, the TELEMAC, to simulate sediment transport and bed morphology on a meandering stretch of Nakdong River, between Gangjeong and Dalsung Weirs, whose length is about 20 km. The numerical simulations have been carried out on a High Performance Computing Cluster (HPC) with the real river bathymetry and with different operation scenarios of the weirs. The hydrodynamic parameters and bed evolutions obtained from the numerical results have been validated against field observation data. In addition, this study is to figure out a magnitude of bed evolution and the location where the erosion or deposition taking place under the weir operating conditions. [ABSTRACT FROM AUTHOR]

Experimental measurements are obtained to investigate the detailed hydrodynamics of wave–wave interactions in the swash-zone. Two bores are generated using a double dam-break mechanism and interact on a 1:10 impermeable rough slope. Measurements of the hydrodynamics are obtained via acoustic displacement sensors and a combined particle image velocimetry and laser induced fluorescent system. Two types of interactions are investigated: wave capture, with the second bore reaching the first one during the uprush, and weak wave–backwash interactions when interaction happens during the backwash of the first wave. The relative strength of the bores at the initial shoreline and time between their arrivals determines the initial type of interaction, however the type as well as the intensity of the interaction may vary throughout the swash-zone for the same swash event. During wave capture and weak wave–backwash interactions, the fluid of the first bore is advected upwards, then mixed with the fluid of the second bore by intense shearing and highly turbulent vortices generated at the front of the second bore because of the relative velocity differences between the two bores. The details of the hydrodynamics during interaction confirm the potential of swash–swash interactions to suspend sediment and transport it shoreward or interrupt seaward sediment transport. [ABSTRACT FROM AUTHOR]

In this study an incompressible smoothed particle hydrodynamics (ISPH) approach coupled with the sediment erosion model is developed to investigate the sediment bed scour and grain movement under the dam break flows. Two-phase formulations are used in the ISPH numerical algorithms to examine the free surface and bed evolution profiles, in which the entrained sediments are treated as a different fluid component as compared with the water. The sediment bed erosion model is based on the concept of pick-up flow velocity and the sediment is initiated when the local flow velocity exceeds a critical value. The proposed model is used to reproduce the sediment erosion and follow-on entrainment process under an instantaneous dam break flow and the results are compared with those from the weakly compressible moving particle semi-implicit (WCMPS) method as well as the experimental data. It has been demonstrated that the two-phase ISPH model performed well with the experimental data. The study shows that the ISPH modelling approach can accurately predict the dynamic sediment scouring process without the need to use empirical sediment transport formulas. [ABSTRACT FROM AUTHOR]

Nearshore submerged structures made of sand-filled geosystems are an interesting use for this type of coastal protection technology. These systems have an advantage over more traditional materials such as concrete units or rock, which is the limited and non-permanent impact on natural coastal processes. On top of that are also some important research achievements and improvements at the level of the materials. However, at more exposed hydraulic conditions under high wave energy its application is still hampered by the lack of knowledge about their performance. This paper describes research results based on a series of laboratory measurements of the hydrodynamic and morphodynamic change produced in the vicinity of submerged nearshore structures. An analysis of the different model outputs produced, with respect to sediment transport, wave reflection and wave-induced pressures, has been made and is discussed throughout the paper. Such a comparative analysis provides insights into the efficiency of each defence scheme in maintaining a beach and in protecting the shoreline. The sand-filled geosystems as nearshore submerged structures proved to be efficient in retarding the offshore movement of sediments and in maintaining the shoreline, even if instabilities due to elements' displacement and local scour have been observed. [ABSTRACT FROM AUTHOR]

Abstract: A 2D depth-averaged model for hydrodynamic, sediment transport and river morphological adjustment is presented. The sediment transport submodel considers non-uniform sediment, bed surface armoring, impact of secondary flow on the direction of bed-load transport, and transverse slope of river bed. The bank erosion submodel incorporates a simple simulation method for updating bank geometry during either degradational or aggradational bed evolution. The model is applied to a 180° bend with a constant radius under unsteady flow conditions, and to Friedkin''s laboratory meander channels. The results are in acceptable agreement with measurements, confirming the two dimensional model''s potential in predicting the formation of river meandering and improving understanding of patterning processes. Future researches are needed to clarify some simplifications and limitations of the model. [Copyright &y& Elsevier]

Abstract: Experiments and numerical simulations are carried out to study clear-water scour around three bridge piers with cylindrical, square, and diamond cross-sectional shape, respectively. To handle movable-bed channels with embedded hydraulic structures, the fluid–structure interaction curvilinear immersed boundary (FSI-CURVIB) method is employed. The hydrodynamic model solves the unsteady Reynolds-averaged Navier–Stokes (URANS) equations closed with the k-ω turbulence model using a second-order accurate fractional step method. Bed erosion is simulated by solving the sediment continuity equation in the bed-load layer using a second-order accurate unstructured, finite-volume formulation with a sand-slide, bed-slope-limiting algorithm. Grid sensitivity studies are carried out to investigate the effect of grid resolution on the predictive capability of the model. Comparisons of the simulations with the experimental data show that for all three cases the agreement is reasonable. A major finding of this work, however, is that the predictive capability of the URANS morphodynamic model improves dramatically for the diamond shape pier for which sediment transport is driven primarily by the shear layers shed from the pier sharp edges. For piers with blunt leading edge, on the other hand, as the circular and square shapes, the URANS model cannot resolve the energetic horseshoe vortex system at the pier/bed junction and thus significantly underpredicts both the scour depth at the nose of the pier and the rate of scour growth. It is also shown that ad hoc empirical corrections that modify the calculated critical bed shear stress to enhance scour rate in the pier leading edge need to be applied with caution as their predictive capabilities are not universal but rather depend on the pier shape and the region of the flow. [Copyright &y& Elsevier]

Abstract: On 10th March 2008, the high energy storm Johanna hit the French Atlantic coast, generating severe dune erosion on Vougot Beach (Brittany, France). In this paper, the recovery of the dune of Vougot Beach is analysed through a survey of morphological changes and hydrodynamic conditions. Data collection focused on the period immediately following storm Johanna until July 2010, i.e. over two and a half years. Results showed that the dune retreated by a maximum of almost 6m where storm surge and wave attack were the most energetic. Dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre- and post-storm dune toe, and reducing impacts of the storm surge. Dune recovery started in the month following the storm event and is still ongoing. It is characterised by the construction of “secondary” embryo dunes, which recovered at an average rate of 4–4.5cm per month, although average monthly volume changes varied from −1 to 2m3.m−1. These embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune. These dune-construction processes were facilitated by growth of vegetation on low-profile embryo dunes promoting backshore accretion. After more than two years of survey, the sediment budget of the beach/dune system showed that more than 10,000m3 has been lost by the upper tidal beach. We suggest that seaward return currents generated during the storm of 10th March 2008 are responsible for offshore sediment transport. Reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross-shore sediment redistribution inducing net erosion in the tidal zone. [Copyright &y& Elsevier]

Abstract: A thorough discussion of results from laboratory experiments with regular waves sheds light on the gap that lies between the sediment transport associated with ripple migration and the performance of a standard bedload transport formula in terms of bed shear concept. It is found that the extent of deviations of the bedload transport formula by Ribberink (1998) from the measured rate of sediment transport associated with ripple migration becomes systematically apparent under conditions of increasing settling time factor Ω s (= η/(w 0 T); η is the ripple height, w 0 the settling velocity and T the wave period). Re-examination of previous two field studies demonstrates a further reinforcement for phase-lag argument addressed in this paper. [Copyright &y& Elsevier]

Abstract: Cohesive sediment is an important component of aquatic environments, which must be monitored and managed for environmental, engineering, and human health reasons. While the hydrodynamic aspects of sediment erosion and transport are well understood, the erodibility of cohesive sediment has proved more difficult to address and predict. Erodibility is the propensity for the sediment to be eroded, and is represented typically as an erosion threshold or erosion rate. It is an attribute of the sediment itself, and is dependent on the sediment properties that dictate the resistive forces in the sediment, such as gravity, friction, cohesion, and adhesion. This paper reviews recent findings from a range of disciplines to create a comprehensive picture of the physical, geochemical and biological properties that influence the erodibility of cohesive sediment. By identifying these key sediment properties, we provide the background for a discussion on how changes in and interactions between the properties generate significant spatial and temporal variations in erodibility. We discuss the development of a predictive model of erodibility, and emphasize the need for more comparable field and laboratory data. [Copyright &y& Elsevier]

Abstract: New laboratory data are presented on the influence of free long waves, bound long waves and wave groups on sediment transport in the surf and swash zones. As a result of the very significant difficulties in isolating and identifying the morphodynamic influences of long waves and wave groups in field conditions, a laboratory study was designed specifically to enable measurements of sediment transport that resolve these influences. The evolution of model sand beaches, each with the same initial plane slope, was measured for a range of wave conditions, firstly using monochromatic short waves. Subsequently, the monochromatic conditions were perturbed with free long waves and then substituted with bichromatic wave groups with the same mean energy flux. The beach profile changes and net cross-shore transport rates were extracted and compared for the different wave conditions, with and without long waves and wave groups. The experiments include a range of wave conditions, e.g. high-energy, moderate-energy, low-energy waves, which induce both spilling and plunging breakers and different turbulent intensities, and the beaches evolve to form classical accretive, erosive, and intermediate beach states. The data clearly demonstrate that free long waves influence surf zone morphodynamics and promote increased onshore sediment transport during accretive conditions and decreased offshore transport under erosive conditions. In contrast, wave groups, which can generate both forced and free long waves, generally reduce onshore transport during accretive conditions and increase offshore transport under erosive conditions. The influence of the free long waves and wave groups is consistent with the concept of the relative fall velocity, H/w s T, as a dominant parameter controlling net beach erosion or accretion. Free long waves tend to reduce H/w s T, promoting accretion, while wave groups tend to increase the effective H/w s T, promoting erosion. [Copyright &y& Elsevier]

Abstract: Overwash is an important process in barrier island evolution and its effects on the barrier morphology and sedimentology have been widely studied. However, the short-term sediment dynamics of overwash processes are not well known due to the lack of specific field studies. This paper presents field data that clarify the sedimentary dynamics of overwash processes on different washover morphologies, and determine the factors leading to non-storm overwash occurrence. Two fieldwork campaigns were undertaken during overwash events: GO.1 (winter of 2001), and GO.3 (winter of 2003), on western Barreta Island (Algarve, Portugal). The fieldwork included measurements of oceanographic conditions, overwash flows, morphology variations, mixing depth and sediment transport paths using tracers. The sediment dynamics induced by overwash varied according to the washover morphology (washover plain versus washover lobe). The sediment transport inside the washover plain was different for the two fieldwork campaigns (average mixing depth of 13cm for GO.1 and 6cm for GO.3); however it had similar main stages: Stage 1 — crest accretion, Stage 2 — onshore transport, and Stage 3 — dynamic equilibrium. The sediment transport inside the washover lobe can be characterised by one onshore flow stage, with erosion of the mouth and channel, and accretion on the washover fan. The main factors governing the occurrence of non-storm overwash in the study area were the combined occurrence of: (1) typical winter waves, (2) spring high tides, (3) washover crest below the high-tide level +2m, and (4) absence of prominent beach berm. This study proved that when the proper conditions are generated, non-storm overwash has sediment transport comparable to storm overwash and therefore may be significant for barrier evolution. Further field studies of overwash are needed, principally for more detailed overwash flow velocity measurements, high-frequency morphologic surveys, and barrier groundwater measurements. [Copyright &y& Elsevier]

Abstract: The objectives of this work are (1) to examine the mechanisms that influence tsunami erosion and deposition mechanisms in the littoral zone via physical simulations of breaking solitary waves over a fine sand beach, and (2) to provide experimental data for validation of numerical models to predict tsunami erosion and deposition processes. The experiments were carried out in a 48.8m×2.16m×2.1m wave flume. The flume was instrumented to observe free surface elevations, cross-shore velocities, suspended sediment concentrations, vertical and cross-shore pore-pressure gradients near the shoreline, and morphological changes. In addition, wave–sediment interactions were observed via underwater video cameras. The results are systematically analyzed to investigate the roles of wave breaking, bore runup, wave drawdown, and wave-induced pore-pressure variations on tsunami erosion and deposition processes. The studies showed that the wave plunging on a thin layer of water prior to reaching the shoreline did not cause much sediment suspension, while the waterjet impinging directly on the beach entrained substantial amounts of sand. The suspended sediments were subsequently pushed up the slope by fluid momentum as the broken wave transformed to a turbulent bore. A small net deposition region was observed near the maximum runup point where both the flow velocity and the water depth were near zero. A significant amount of the sediment transport occurred during the wave drawdown in the form of thick sheet flow, which resulted in net erosion of the shore face and the beach. A hydraulic jump formed near the wave breaking region toward the end of the drawdown, which caused most of the suspended sand to deposit in the wave breaking region. Consequently, breaking solitary waves over a sloping fine sand beach led to net erosion of the shore face and the beach, net deposition in a small region immediately seaward of the max excursion point, and net deposition in the wave breaking zone. [Copyright &y& Elsevier]

Abstract: A field experiment was conducted on a high energy sandy beach (Truc Vert, France) to examine swash zone processes and shoreline erosion–accretion in response to changing wave and tide conditions. Beachface morphological changes were measured at the swash-by-swash timescale using an array of ultrasonic bed-level sensors and at the tidal timescale through total station surveys. Hydrodynamic and sediment dynamic data were collected using arrays of pressure transducers, electromagnetic current meters, optical backscatter sensors and total load sediment traps. Data were collected for 16 consecutive days (33 tides) over a spring–neap–spring tidal cycle with offshore significant wave heights of 1–4m and periods of 5–12s. The swash motion was predominantly at infragravity wave frequencies. Over the measurement period, the upper beach experienced phases of accretion, erosion and stability. Trapped sediment loads for the uprush and backwash were predicted reasonably well by cross-shore velocity skewness, but the prediction of net transport over individual swash events by velocity-based models was more problematic, particularly lower in the swash zone where swash interactions were more prevalent. Net sediment fluxes over individual swash events often exceeded 100kg per unit meter beach width and such rates were only one order of magnitude less than the net transport typically experienced across the high tide swash zone over complete tidal cycles. Upper beach erosion–accretion at the tidal timescale was reasonably well predicted by the Dean criterion based on offshore wave steepness and dimensionless fall velocity, but the beach gradient also played a significant role in controlling the occurrence of erosion and accretion. [Copyright &y& Elsevier]

Abstract: The rate of recession of Niagara Falls (Horseshoe and American Falls) in northeastern North America has been documented since the 19th century; it shows a decreasing trend from ca. 1 m y−1 a century ago to ca. 0.1 m y−1 at present. Reduction of the flow volume in the Niagara River due to diversion into bypassing hydroelectric schemes has often been taken to be the factor responsible, but other factors such as changes in the waterfall shape could play a role and call for a quantitative study. Here, we examine the effect of physical factors on the historically varying recession rates of Niagara Falls, using an empirical equation which has previously been proposed based on a non-dimensional multiparametric model which incorporates flow volume, waterfall shape and bedrock strength. The changes in recession rates of Niagara Falls in the last century are successfully modeled by this empirical equation; these changes are caused by variations in flow volume and lip length. This result supports the validity of the empirical equation for waterfalls in rivers carrying little transported sediment. Our analysis also suggests that the decrease in the recession rate of Horseshoe Falls is related to both artificial reduction in river discharge and natural increase in waterfall lip length, whereas that of American Falls is solely due to the reduction in flow volume. [Copyright &y& Elsevier]

Abstract: Steady state suspended-load of sediment transported in flow over erodible beds usually is treated by the advection-diffusion approach, though in recent years, it is being treated as a two-phase flow phenomenon incorporating kinetics of sediment particles. Among the advection-diffusion approaches, Rouse''s (1937) equation is the well-known, although a number of researchers in later periods have attempted to improve it by modifying the mixing length concept taking into account other aspects. In this paper, the advection-diffusion approach and associated logarithmic law of flow velocity are revisited. It is concluded from the logarithmic law that the Reynolds shear stress is a linear function of height above the bed, which reduces to bed shear stress in the case of a long horizontal channel. As a consequence, it is shown that the volumetric concentration of sediment is best approximated by the sum of two power laws of height above the bed. An equation is derived for the suspended-load transport rate in terms of elementary functions. [Copyright &y& Elsevier]

Abstract: A dynamical model is proposed to study sediment transport in river networks. A river can be divided into segments by the injection of branch streams of higher rank. The model is based on the fact that in a real river, the sediment-carrying capability of the stream in the th segment may be modulated by the undergone state, which may be erosion or sedimentation, of the th and th segments, and also influenced by that of the th injecting branch of higher rank. We select a database about the upper-middle reach of the Yellow River in the lower-water season to test the model. The result shows that the data, produced by averaging the erosion or sedimentation over the preceding transient process, are in good agreement with the observed average in a month. With this model, the steady state after transience can be predicted, and it indicates a scaling law that the quantity of erosion or sedimentation exponentially depends on the number of the segments along the reach of the channel. Our investigation suggests that fluctuation of the stream flow due to random rainfall will prevent this steady state from occurring. This is owing to the phenomenon that the varying trend of the quantity of erosion or sedimentation is opposite to that of sediment-carrying capability of the stream. [Copyright &y& Elsevier]

Abstract: Field observations and sediment samples at a coastal-plain setting in southeastern Sri Lanka were used to document the erosional and depositional impacts of the 2004 Indian Ocean tsunami and to interpret the hydrodynamic processes that produced an extensive sand-sheet deposit. Tsunami deposit thicknesses ranged from 6 to 22 cm with thickness being controlled partly by antecedent topography. The deposit was composed of coarse to medium sand organized into plane-parallel laminae and a few laminasets. Vertical textural trends showed an overall but non-systematic upward fining and upward thinning of depositional units with an upward increase in heavy-mineral laminations at some locations. Repeated patterns in the vertical textural trends (upward fining, upward coarsening, uniform) were used to subdivide and correlate the deposit into five hydro-textural stratigraphic units. The depositional units were linked to hydrodynamic processes and upcurrent conditions, such as rates of sediment supply and composition of the sediment sources. Vertical changes in grain-size distributions recorded the depositional phases associated with flow acceleration, initial unsteady pulsating flow, relatively stable and uniform flow, flow deceleration, slack water, and return flow or flow redirection. Study results suggest that vertical textural trends from multiple cross-shore sections can be used to interpret complex tsunami flow histories, but at the location examined, interpretation of the lateral textural trends did not provide a basis for identifying the correct sediment transport pathways because flow near the landward boundary was multidirectional. [Copyright &y& Elsevier]

A coastal area morphodynamics model was developed which is capable of modelling both short-term and long-term bathymetric changes in coastal areas. The model is composed of three main modules: wave transformation module, hydrodynamic module and sediment transport and morphology module. The three main modules run simultaneously where the waves and coastal currents information are passed to the sediment transport module, which calculates the sediment transport fluxes and the corresponding bathymetric changes. The model''s output is linked through dynamic plotting libraries, which produces contour plots, vector plots and animation files for the waves, currents, sediment transport fluxes and bathymetry. The model''s output compares very well with other commercial models for the case of an offshore breakwater over a sloping beach. [Copyright &y& Elsevier]

Abstract: The paper presents (1) a semi-theoretical model for the computation of maximum clear-water scour depth below underwater pipelines in uniform sediments under steady flow and (2) an experimental investigation on the influence of upward seepage on clear-water scour depth below underwater pipelines. Based on the “image method” of the potential flow theory for the flow through the gap between a circular pipeline and the scoured bed, a theoretical model is presented for the computation of maximum scour depth below underwater pipelines in clear-water condition considering the wall correction. Also, a simple theoretical calculation, that involves Chiew''s (1991) [Chiew, Y.M., 1991. “Prediction of maximum scour depth at submarine pipelines.” J Hydraul Eng 117(4), 452–466] gap flow curve, is proposed to estimate the maximum scour depth considering the wall correction. The computed results agree satisfactorily with the experimental data. In addition, the potential predictors of the maximum scour depth given by different researchers are compared with the experimental data. The result of an experimental investigation on the scour depth below pipelines under the influence of upward seepage through the bed sediment is presented. In general, the scour depth below pipelines with upward seepage is smaller than that without seepage. There exists a critical value of the ratio of seepage velocity to main flow velocity that corresponds to a minimum scour depth. [Copyright &y& Elsevier]

Abstract: This paper analyses the morphological response induced by low-crested structures on the adjacent seabed, with particular interest in the erosion patterns that frequently develop at gaps and roundheads. The mechanisms responsible for erosion processes are examined by means of morphodynamic simulations with the numerical suite MIKE 21 CAMS developed by DHI Water & Environment. The main purpose of the paper is to verify how and how far a commercial code can predict bed evolution, in vicinity of defence structures in a real case, in order to get information that may be very useful for structure design and possible maintenance of existing works. The code is applied to a long-term simulation on a study site that is characterized by a composite intervention and suffers from severe erosion, Lido di Dante (Italy). The simulation covers the period (one year and a half) between two available multi-beam surveys, in order to have a detailed real bathymetry as starting point and another one, as accurate as the first, to compare numerical with surveyed results. All the other input data for the model, as waves, tide, wind and sediment characteristics, are derived from measurements in the area; moreover, the code is calibrated using wave and current data acquired during a field campaign. The bed evolution derived from simulations shows a good agreement with the survey both in the locations and in the intensity of erosive and depositional areas. A sensitivity analysis of results to some selected modelling parameters is performed on a shorter simulation period (one month), showing that accounting for bed slope in sediment transport modelling has greater effects in bathymetry evolution than the use of a complex sediment bathymetry or the representation of wave diffraction. [Copyright &y& Elsevier]

Abstract: Low crested structures for beach defence purposes are frequently configured in the form of cells. This paper investigates the hydrodynamic and morphological response of such defence schemes by means of laboratory experiments and numerical simulations. Experiments were carried out at the large mobile-bed basin of the “Laboratorio di Idraulica Costiera” of the “Politecnico di Bari”, IT. Tests peculiarity is the simultaneous simulation of three different types of lateral confinement: a channel, representative of an indefinitely long structure, and two areas with narrow and wide gaps, representative of a common scheme and of an almost isolated structure respectively. Submerged, zero freeboard and emerged conditions were tested. A typical storm of the Northern Adriatic sea was reproduced by 6 wave attacks. Water level and currents were measured in front and behind the structures, at gaps and roundheads. Results, focusing on rip current intensities and piling-up, are presented and discussed. An extensive plan view of wave intensities and flow patterns inside the basin is provided through numerical simulations with MIKE 21 numerical suite. The sand bed was surveyed along 30 profiles covering the narrow gap area and the isolated structure roundheads. For the submerged conditions tests, 15 of these profiles and the shoreline position were monitored after each step of the simulated storm. Average and maximum values of local erosion at the structure toe are presented. Time evolution of erosion at gaps is related to the main hydrodynamic variables through Bijker sediment transport formula. Evaluation of volume changes in the protected area shows that sand is in average trapped behind the barriers, being transported offshore from gaps and returning inshore over the crest. The observed and reconstructed transport mechanism is a combination of bed load and suspended transport, the latter being slightly more important. Bed level changes are well predicted by morphodynamic simulations performed with MIKE 21 CAMS. [Copyright &y& Elsevier]

Abstract: Data from field experiments carried out in the swash zone on two Pacific beaches in Japan were analyzed to determine net sediment transport rates and the resulting foreshore response. The experiments involved artificial modification of the foreshore slope with a bulldozer, either making the slope steeper or milder, after which a wide range of measurements were performed as the slope evolved back towards its equilibrium value under the action of the incident waves. A sediment transport formula was developed to predict the net transport rate over many swash cycles and compared with the derived transport rates from the surveys of the foreshore. This formula was then combined with the conservation equation for sediment volume to yield a mathematical model for simulating the foreshore evolution under varying waves and water level. Predictions by the model were compared to measurements yielding satisfactory agreement, although the optimum values on the main calibration coefficient displayed some variation between experiments. Further analysis of a limited number of cases indicated that this coefficient may be dependent upon the ratio between the incident wave period and the swash period, which characterizes the interaction between individual waves in the swash zone. A simple analytical solution was also derived for a schematized foreshore shape to estimate the typical time scale of the morphological response. [Copyright &y& Elsevier]

Rising sea level and increasing tropical storm frequency caused by the changing climate are threatening small Island economies which depend on their coastal environments and resources. Owing to the high socio-economic and environmental values of tropical sandy beaches, monitoring the evolution trends of shorelines are regarded as an essential strategy to improve the resilience of Island states. The present study conducted in Mauritius, indicates a net erosional effect at Le Morne amounting to 8049.7 ± 5% m2 which is attributed to the hydrodynamics of the lagoon, whilst a net accretional effect has been observed at Flic-en-Flac, equivalent to 6571.3 ± 5% m2 and attributed to periodic beach nourishments. The shoreline evolution at Le Morne is predominantly influenced by Passe de la Prairie where an average energy of 0.162 m2/Hz, corresponding to an average wave height of 1.16 m, carries enough energy and momentum to influence the sediment transport near the peninsula. At Flic-en-Flac, longshore currents propagating on either sides of the central region and directed northwards and southwards influence the shoreline, resulting in an accretion zone extending 62.5 ± 15 m near Villa Caroline over the 2009–2018 period. To dampen this problem, a beach management strategy is proposed which revolves around the restoration of corals in front of eroded shores, replacement of casuarina trees, and enforcement of regulatory laws. [Display omitted] • The evolution of shoreline is detected using satellite imagery and GIS. • In-situ measurements are used to comprehend sediment transport. • Hydrodynamic modelling is performed to support the analysis. • The link between shoreline changes and coastal current propagation is presented. • Management measures to dampen the impacts of erosion are proposed. [ABSTRACT FROM AUTHOR]