Search

The main purpose of the research was to develop appropriate tools for forecasting the effects of storms. The use of the high-resolution SWAN wave model powered by AROME wind fields to couple it with the SWANOneSed sediment transport model and a model using the Ruggiero formula, predicting the extent of the flooded shore, allowed the development of reliable tools for forecasting the effects of storms. Validation using qualitative analysis showed that the results obtained from the coupled SWANOneSed model are characterized by high consistency in intensification and direction of changes. The model using the Ruggiero formula obtained a high value of the correlation coefficient, i.e. 0.970 and 0.992 for the Satbałtyk-Xbeach model data, based on the Hunt&Mase formula, and the high-resolution Pleiades Neo satellite data, respectively. By combining models from the SWAN family, i.e. the SWAN and SWANOneSed wave model and a model using the Ruggiero formula, it was possible to obtain reliable and compatible tools enabling an uninterrupted and synchronized operational process of generating forecasts of storm effects. [Display omitted] • The coupling of the SWAN & SWANOneSed enables reliable and operational forecasting. • Measured & terrain surveyed data-fed model are consistent with other observed data. • Formula van Rijn reliably reproduces sediment transport in various types of coasts. • The Ruggiero formula is applicable in various parts of the Polish coast. [ABSTRACT FROM AUTHOR]

Understanding sediment transport processes on natural sandy beaches is essential for gaining insights into beach recovery and making effective coastal management decisions. This study examines surfzone sediment transport rates related to beachface morphological variations on an embayed mesotidal sandy beach located on the northwestern coast of the Baja California Peninsula in Mexico. Data were collected during a week-long field experiment conducted in June 2016 under low-to-moderate wave energy conditions (H s = 0.4 − 1.3 m). Daily topographical surveys and continuous measurements of near-bottom suspended sediment fluxes were conducted alongside the application of an extended energetics-based model that accounted for velocity and acceleration skewness. Results reveal contrasting accretionary and erosive patterns in the inner surfzone, along with consistent sediment deposition in the swash zone throughout the study period. Onshore sediment transport is found to be related to short-period calm wave conditions (H s < 0.7 m; T p < 10 s) and a weak undertow (<0.2 ms−1). Alongshore nonuniform wave breaking, influenced by irregular bathymetry and moderate-energetic oblique waves from the northwest, contributes to an alongshore gradient in sediment transport rate, leading to erosion in the northern part of the intertidal beach and accretion in the southern part. Suspended sediment flux measurements at 0.2 m above the bed suggest offshore mean transport predominates over oscillatory transport throughout the field experiment. Nevertheless, this observation should be interpreted with caution, as the flux is not vertically integrated across the water column and does not consider fluid acceleration. The model predictions effectively replicate sediment transport rates and consequent volumetric changes (Accuracy = 55– 63 % ; RMSE = 44–69 m3; Bias = − 2 to −61 m3), although they underestimate observed accretion by a factor of three and overestimate erosion by a factor of two. Overall, this research highlights the complexities of natural sandy beach recovery processes in mesotidal environments and emphasizes the importance of considering both cross-shore and longshore components in sediment transport assessments. [Display omitted] • Beachface accretion remains consistent under low-to-moderate wave conditions. • Combined velocity- and acceleration-skewness model reproduces onshore sediment transport, but underestimates beachface accretion. • Erosive and accretive surfzone patterns are linked to nonuniform wave breaking influenced by bathymetry. • Undertow significantly governs offshore sediment flux near the seabed within the surfzone. [ABSTRACT FROM AUTHOR]

• Flume experiments were conducted to assess the impact of submerged flexible vegetation on regular wave attenuation and beach morphology. • The presence of vegetation prevented further erosion of the beach, resulting in a reduction of 7% to 63% in experiments. • The attenuation caused by vegetation results in the wave breaking point being closer to the shoreline on vegetated sand, leading to shoreline retreat. • A dimensionless equation was developed to characterize the behaviour of the cross-shore beach profile under the protection of flexible vegetation. Coastal protection methods are evolving from hard engineering techniques to natural enhancement approaches. Aquatic vegetation provides an environmentally friendly solution by effectively dissipating waves and resisting erosion. Laboratory flume experiments were conducted to investigate the effect of submerged flexible vegetation on the regular wave attenuation and cross-shore profiles on the artificial plane beach under varying hydraulic conditions. Variations in the waveform, wave spectrum, and wave height were analysed in the vegetation zone. Results show vegetation distorts the waveform and accelerates the attenuation process of the wave energy, and wave height evolution behaves differently from the theoretically obtained attenuation by Mendez and Losada (2004) due to the underestimating vegetation-induced attenuation and neglecting sediment-induced attenuation. Additionally, the formation process of the winter and summer profiles of the vegetated beach was analysed by the screenshots. Regenerated wave breaking becomes more apparent with increasing wave periods. The critical surf similarity parameter of the vegetated beaches was found to be lower than that of a smooth, impermeable slope because of the energy dissipation. Vegetation did not alter the type of the beach profiles, as compared to the final profiles and their characteristic parameters of the unvegetated beaches. Instead, it reduced the erosion depth and brought the eroded area closer to the shoreline. Dimensionless parameters were formulated to characterize the response of the cross-shore beach profile under the shelter of flexible vegetation, and an empirical equation about maximum erosion depth was developed within the scope of the experiment. [ABSTRACT FROM AUTHOR]

Beaches are important coastal features that provide vital ecosystem services; however, these systems are threatened by coastal erosion, sea-level rise, and coastal squeeze. Beach nourishments are a commonly applied coastal protection measure to mitigate erosion and flood risks while maintaining or enhancing recreational values. Nourishments vary in scale from mega-nourishments to small-scale nourishments, where the latter has typically been less studied due to the limited resources for monitoring. Meanwhile, with rising sea levels, the implementation of small-scale nourishments is expected to increase, and there is a need for more knowledge about the morphological evolution and technical lifetime of these interventions. In this study, the morphological responses of small-scale beach nourishment (total volume 20,000 m3 which amounts to 30 m3 added per m alongshore) are observed and quantified over various timescales, considering the initial adjustment, long-term development, and event-driven response. The investigated nourishment is implemented in a partly sheltered coastal embayment in the semi-enclosed Baltic Sea, which has a complex interaction between waves and water levels. Furthermore, the beach is surrounded by hard structures, a rock revetment at the back, and a harbor mole and a groin, influencing the longshore and cross-shore sediment transport. The results show that substantial reduction in subaerial volume can be attributed to specific events. In addition, we observed considerable spatial variation in the sediment re-distribution induced by hard structures and variability in the nearshore bathymetry. The lifetime of the beach nourishment is just over two years. The nourished material remains in the system at the end of the lifetime but is not available for beach recovery. Still, the added subaerial volume has eroded at the midsection, and the protective beach width has been reduced, leaving the rock revetment exposed with reduced protection for the hinterland. The energy conditions at the site are highly episodic, which impacts morphological evolution, and observations indicate that the development is event-driven. • Beach morphodynamics in a low-energy coastal embayment • Episodic wave activity and water level variations are influenced by basin effects. • Morphological response of a small-scale beach nourishment at different timescales • Beach nourishment performance during an extreme storm surge [ABSTRACT FROM AUTHOR]

While the impact of the spatio/temporal variability of grain size on morphological beach state is reasonably well understood, relatively little is known on its impact at a scale of days/months on aeolian sediment transport. This study focuses on five short intensive wind events during which aeolian sediment transport measurements, beach surface sampling and elevation change surveys were carried out for 1 to 3 days, over a 16-month period on a microtidal beach dominated by offshore winds. Monthly observations show a high temporal variability in beach grain size in relation to the decoupling between hydrodynamic and aeolian processes, from medium sand after a marine storm and inundation of the beach, to very coarse sand after several weeks of storm-force winds. During each wind event, topographic change on the beach ranged from zero, to 0.55 m. The time scale of coarsening depended on the initial beach grain size and could be very fast when the beach was composed of medium sand (e.g. 388 μm sand changed to coarse sand of 547 μm in 40 h). In contrast, it took one month to transition from a coarse median beach grain size of 883 μm to a very coarse one of 1323 μm. This variability in grain size results in dramatically different rates of sediment flux. For example, during average wind speeds of 10 to 14 m/s the sediment flux when the beach was composed of medium sized sand ranged between 21 and 154 kg/m/h compared to 0.4 to 50 kg/m/h when the beach was composed of coarse and very coarse sized grains. Overall, this study highlights the importance of beach grain size variability on aeolian sediment transport and shows that for similar incident wind and climatic conditions aeolian sediment transport rates vary dramatically. The study demonstrates the importance of taking care when using a constant median grain size in the calculation of long-term aeolian sand transport on beaches with heterogeneous spatial and temporal beach grain size variability. • Transport rates can be ten times greater on medium-sized beach than coarse one. • Offshore wind generate a grain size sorting, the finest sands are exported seaward. • Topographic variations of the beach depends on its grain size and sand supply. • The return of fine sediments depends on marine storms occurrence and intensities. [ABSTRACT FROM AUTHOR]

An approach involving data on wave-induced sediment transport estimates is essential for managing coastal environments. Numerical models are powerful tools to understand and investigate many processes responsible for longshore sediment transport (LST) in a systematic way, since direct measurement of LST is a difficult task. This paper presents estimates of longshore sediment transport through numerical modeling of wave-induced sediment dispersion patterns in the Formosa Bay, State of Rio de Janeiro - Southeast Brazil. The analysis was conducted using the computational package Coastal Modeling System/SMC-Brazil and mathematical formulations proposed by Cerc (1984). The results suggest average residual solid discharge (Qsr avg) in the order of 131,442.745 m3/yr in northern sector, −151,908.32 m3/yr in central sector, and 71,987.69 m3/yr in southern sector of investigated area. In addition, it is important to highlight that minor variations in the wave incidence angle may cause changes in the longshore sediment drift, promoting the convergence and divergence zones throughout the investigated area. The results presented contribute to the advancement of knowledge on the topic addressed here and will be useful in future engineering projects related to beach nourishment and the management of coastal areas subject to erosion processes. • Data are presented on simulations of wave-induced longshore sediment transport rates in Baia Formosa Bay, southeastern Brazil. • The Coastal Modeling System SMC/Brazil were used. • Results suggest different solid outflow rates for each sector of investigated area. • The model may provide a basis for planning actions and environmental management in coastal zones. [ABSTRACT FROM AUTHOR]

Beach loss is a growing global challenge that threatens the safety of coastal communities, the health of coastal ecosystems, recreational amenities, and regional economies dependent on tourism. Spatial gradients in longshore sediment transport, or divergence of drift (DoD), is a primary driver of beach width change over multi-annual time scales, but the response of any particular beach can be challenging to characterize and predict. Here we present a new method to characterize DoD using a non-uniform segmentation of the coastline informed by the spatial distribution of longshore transport potential, including the location of physical barriers identified using satellite imagery, and both maxima and reversals in longshore transport potential derived from nearshore wave data. The method demonstrates improved capacity to predict beach width trends at sandy beaches compared to methods that rely on a uniform segmentation of the coastline. In an application to southern California where satellite data documents two decades of beach width change, the non-uniform segmentation method correctly predicts the sign of beach trends at 93% of transects within a littoral cell and achieves a linear correlation between DoD and beach width trends exceeding 0.8. Moreover, we find that a minimum of five years of data are required to establish consistently strong correlations between DoD and beach width changes. Conversely, use of a uniform segmentation is shown to be unreliable for estimating beach width trends due to strong sensitivities to shoreline segment size. This work shows the potential to leverage nearshore wave data and satellite-based beach width data for improved characterization of shoreline dynamics relevant to beach erosion management. • A new shoreline modeling method is presented for estimating divergence of drift. • Segment boundaries are identified using longshore transport characteristics. • Strong correlations were shown between divergence of drift and beach width trends. • A littoral Peclet number characterizes the dominant longshore transport mechanism. [ABSTRACT FROM AUTHOR]

This paper presents the use of an Eulerian–Eulerian multi-phase model to examine sediment transport over a gravel beach under regular waves. A previously published full-scale experiment is reproduced numerically; the simulated wave deformation, flow velocity, pore pressure, and morphological evolution are consistent with measurements. The multi-phase model can produce berm formation for smaller waves and beach erosion for larger waves as observation in previous field studies. The sensitivity analysis suggests that the nonlinear component of drag has significant effect on the berm formation through infiltration and exfiltration. The two simulated forces applied on the sediment (drag and buoyancy) are examined. The drag is the main force directly for sediment transport; therefore the sediment transport rate has high correlation with depth-averaged flow velocity. The buoyancy that is caused by plunging flow impacting beach face can push the sediment landward in the bore front, where the flow acceleration has its peak. The flow acceleration is considered in some previous sediment transport models empirically for simulating morphological evolution of gravel beach under waves. The buoyancy links the flow acceleration and sediment transport rate in the bore front. • Sediment transport in a gravel beach is simulated using a multiphase model. • The drag is the main force directly for sediment transport. • The buoyancy links the flow acceleration and sediment transport rate in the bore front. • The nonlinear drag has the effect on berm formation. [ABSTRACT FROM AUTHOR]

Storm surge, a major disaster in coastal areas, is generated by tropical cyclones. Strong currents and waves during storm surges often cause sediment transport and beach erosion, significantly damaging the coastal ecosystem. This paper presents a flow-wave-sediment-morphodynamic coupled model to predict morphodynamic changes caused by overwash during storm surges. In the model, the flow field is calculated using the generalized shallow water equations coupled with the Simulating Waves Nearshore (SWAN) model, while sediment transport and bed changes are computed using a non-equilibrium total-load sediment transport model. The model solves the governing equations by employing the explicit finite-volume approach based on a rectangular mesh. The Godunov-type central upwind scheme is adopted to calculate the interface fluxes, thereby solving the complex Riemann problem. A series of numerical experiments considering wave-induced longshore current and short-term bed erosion are conducted to validate the established model and demonstrate its ability to simulate waves, flow fields, and bed changes during storm surge. Specifically, we used the model to simulate the morphological evolution of the Santa Rosa barrier island caused by Hurricane Ivan's storm surge, and the results indicate that the model accurately predicts the real-case erosion process caused by storm surge and overwash during the hurricane. The simulated results clearly explain overwash development, including washover fans, foredune erosion, and back-barrier deposition. It demonstrates that the front dune significantly eroded with the Santa Rosa barrier island coastline retreating by a maximum of about 80 m during the storm surge. More than three breaches with a width of up to 135 m were formed on the sandy barrier due to wave overwash, while the topography at the breach changed significantly. • A new flow-wave-sediment-morphodynamic coupled model is developed to predict morphodynamic changes caused by overwash during storm surges. • A series of numerical experiments conducted using the new model demonstrates its ability and it successfully predicts the overwash erosion of the Santa Rosa barrier island during Hurricane Ivan's storm surge. [ABSTRACT FROM AUTHOR]

During August 2018 – November 2019, the transport pathways of dredge material from a specially constructed nearshore feeder berm were investigated as part of a collaborative study by the City of South Padre Island, U.S. Army Corps of Engineers–Galveston District, U.S. Geological Survey, Partrac GeoMarine Inc., and Texas A&M University, into the efficacy of beneficial use dredge material (BUDM) as a method of replenishing the beach profile and shoreface at South Padre Island, Texas with sediment. Dual-signature (fluorescent and ferrimagnetic) tracer particles, designed to be hydraulically equivalent to the dredge material, were placed on the berm, and a sampling program was initiated to monitor the spatiotemporal movement of tracer particles under the influence of the prevailing hydrodynamic regime. Wave and current data were collected and were used together with available metocean data to identify the forcing mechanisms of sediment transport; improved understanding garnered from the consideration of multiple datasets can be used to inform future coastal management decisions. Tracer analysis results indicated low magnitude, shoreward transport of dredge material from the berm and along shore transport in both northerly and southerly directions. Small amounts of tracer detected in beach face samples demonstrated connectivity between the constructed feeder berm and the shoreface. However, the generally low tracer concentration within beach face samples indicated low rates of sediment transport for berm sediments, and a low magnitude sediment transport pathway from the berm directly to the beach face, with possible storage of sediment in the nearshore bar system. Given that the berm was at or beyond the closure depth and considering the relatively weak prevailing near bottom hydrodynamic conditions, the potential for sediment to be mobilized and transported during the study period was generally low. Periods of higher energy waves, driven by north-northwest winds, were identified as a key driver of sediment transport but due to the infrequent nature of these events the sediment transport regime across the area of interest was temporally limited. Longshore movement of sediment was both north and south, mainly dependent on prevailing wind directions and resulting longshore currents. We discuss implications for coastal zone management and the use of feeder berms as an artificial beach nourishment mechanism to replenish sediments lost by coastal erosional processes. The insight into nearshore emplacement of material can be used by local governments and coastal managers to optimize the efficacy of berm emplacement and implement such schemes as a cost-effective nourishment option, or when onshore placement of material is not feasible. • Hydrodynamic and tracer measurements were effective monitors of sediment transport. • Hydrodynamic monitoring indicated relatively weak sediment transport conditions. • Tracer sampling confirmed that transport to replenish the beach was low magnitude. • Consider sediment transport regime before selection of BUDM placement area. • Licensed BUDM placement areas may not be optimal for beach nourishment. [ABSTRACT FROM AUTHOR]

Predicting the future behavior of beach and nearshore systems requires an accurate delineation and understanding of coastal cell boundaries, sediment transport pathways, and sediment sources and sinks. Unfortunately, there is a paucity of field datasets on beach and nearshore morphological change that extend fully from the top of the dunes to beyond the depth of closure to enable quantification of the sediment budget. Here, for the first time, we employ a total sediment budget approach, examining a sandy and embayed beach located in the north coast of SW England, to investigate inter- and multi-annual embayment scale sediment dynamics over a 10-year period that includes extreme storm erosion and post-storm recovery. We demonstrate that, despite the deeply embayed nature of the beach, the shoreline orientation roughly parallel to the dominant wave direction and the overwhelmingly cross-shore forcing of the inter-tidal beach volume, the system is neither closed, nor balanced. The very significant net changes in the recorded sediment volume from dune top to depth of closure (−14.5 m ODN), representing a loss of c. 100 m3 m−1 during the extreme storm period and a gain of c. 200 m3 m−1 during the recovery period, indicate that significant sediment transport occurs seaward of the base of the terminating headlands and beyond the morphological depth of closure. The results further indicate that the inter-tidal region is partly uncoupled from the sub-tidal region, with the former region dominated by cross-shore sediment fluxes, whereas the subtidal region is also significantly affected by longshore sediment fluxes. A conceptual model is presented that balances the observed volume changes with inferred fluxes, forced by variations in total and alongshore wave power. This study contradicts the general assumption that when sediment exits the inter-tidal, it rests undisturbed in the sub-tidal, waiting for a period of low-moderate energy to bring it onshore. The large sediment volumetric variations across the lower shoreface (depth of 5–20 m), which are of the same order of magnitude as, but uncorrelated with, those occurring in the inter-tidal region, are suggestive of an energetic longshore transport system across this deeper region. It is possible that this transport system extends along the whole north coast of SW England and this finding may lead to a shift in understanding of sediment budgets along exposed and macrotidal embayments globally. Unlabelled Image • Full sediment budget was produced along an exposed macrotidal embayment and linked to wave forcing. • Inter- and sub-tidal volumes are not inversely correlated, indicating decoupling. • Sediment budget suggests significant exchange around headlands and/or across depth of closure. • Beaches on this coast type can be considered part of an extended coastal cell. [ABSTRACT FROM AUTHOR]

The twin ambits of climate change and coastal development have raised public awareness of shoreline management. Simultaneously, they have highlighted a gap in our understanding of sediment transport and morphodynamic processes at time and space scales appropriate for shoreline management purposes. Here, we analyse an exceptional set of beach surveys gathered over a period of twenty-two years along the Suffolk coast, eastern UK, that extends over approximately 80 km to investigate the meso-scale shoreline variations. The surveys have been made biannually along fixed transects spaced at approximately 1 km intervals as part of a strategic monitoring exercise undertaken by the coastal authorities to assist in shoreline management planning. Changes in beach volume, foreshore slope and shoreline position have been computed to investigate both spatial and temporal changes. The analysis reveals some distinct responses to the physical processes of tides and waves, anthropogenic interventions and geological controls. Neither a clear relationship between the presence of sea defences and beach response nor an ordered regional-scale shoreline movement are evident. Temporal variations in beach volumes and position provide a similarly complex picture with recessionary, accretionary and stable behaviour all apparent within the study site. There is evidence of quasi-cyclic behaviour at some locations as well as a reduction in variability over time-scales beyond approximately five years. • Historic beach surveys over a period of 22 years along a frontage of 80km have been analysed for their meso-scale dynamics. • Meso-scale morphological changes of protected and unprotected beaches have been classified. • The majority of beaches fronting hard defences don't exhibit erosive trends; the majority of those without hard defences do. • Beach morphodynamics are constrained to the synoptic scale, with little coherent variation at the meso-scale. [ABSTRACT FROM AUTHOR]

Depth of Closure (DoC) calculation has been analysed for engineers and researchers during decades due to its relevant importance on marine works, such as beach nourishments or littoral defense projects. Several methods can be found in the literature related to the evaluation of DoC. However, they just focus on the bottom elevation change, leaving aside the cross-shore sediment transport issue. This work deals with all requests of the DoC definition and presents a new method based on the comparison of repetitive beach profiles. The main contribution of this research is the methodology presented to quantify the cross-shore sediment transport by the calculation of the Net Cross-shore Sediment Transport Parameter (NCSTP C). Its application to a complex area of the East Spanish coast concludes that NCSTP C values less than or equal to 10% can be considered as no significant. The differences between several criteria based on the change of the bottom elevation are also studied in order to evaluate if they are relevant for engineering works. The new methodology developed is a great advance in the knowledge of this imaginary boundary (DoC), since it allows to discriminate between different possible DoC values when applying any method based on profile surveys comparison. • New method to obtain the Depth of closure from profile surveys. • Quantification of the net cross-shore sediment transport. • 762 periods of time analysed over 22 years (1992–2014). • Five profile survey criteria have been compared. • The new method permits the selection of the DoC among several possible values. [ABSTRACT FROM AUTHOR]

Sandy beaches are highly dynamic due to the transport of sediment by waves and currents. While beach erosion is mainly driven by cross-shore currents, beach recovery is driven by the onshore-directed transport of sediment by incoming short waves. This latter process is complex and often inaccurately predicted by morphodynamic models. This is partly because of the omission of the effects of bed form-induced and surface-generated turbulence on sediment pick-up in these models. In this paper, the phase relationship between the oscillatory flow, turbulence and suspended sediment concentration was investigated based on field measurements obtained beneath shoaling waves, spilling breakers and surf bores. Wave-averaged and intra-wave variability in turbulence and suspended sediment concentration were analysed on a wave-by-wave basis, where individual waves were extracted and then grouped according to relative wave height. Beneath shoaling waves, small but steep wave ripples were shown to affect the phasing of suspended sediment concentration and to cause an offshore-directed short-wave suspended sediment flux. Beneath spilling breakers and surf bores, sediment was mainly stirred under the wave crest and the short-wave suspended sediment flux was onshore-directed. Based on the analysed data, several mechanisms were suggested to cause sediment stirring: friction between the wave orbital motion and the seabed, penetration of surface-generated turbulence towards the seabed, increased bed shear stress at the wave front due to acceleration skewness, and during conditions with strong undertow, wave-current interactions. [ABSTRACT FROM AUTHOR]

We develop an idealised one dimensional (cross-shore) morphodynamic model that couples wave, tide and sediment dynamics to study the effect and evolution of a shoreface nourishment. Sediment fluxes driven by wave skewness, wave asymmetry (both onshore) and return flow (offshore) are considered. With the aid of new analytical expressions for the skewness and standard deviation of wave velocity and acceleration, sediment fluxes are calculated. Nourishment is viewed as a perturbation to the system in equilibrium that is subject to the divergence of the perturbed sediment flux and a gravity driven diffusion term. Depending on the location, a nourishment may provide a feeder or lee effect. In moderate and mild wave conditions, the evolution of a nourishment primarily depends on the relative location of nourishment and break point. Placed well offshore of the break point, the nourishment induces an overall positive perturbation in sediment flux, resulting in onshore migration (feeder effect). Located closer to the break point, the nourishment induces an earlier wave breaking, which dissipates part of the wave energy (lee effect), leading to a negative sediment flux perturbation around this break point and a positive sediment flux perturbation around the break point of the un-nourished beach. Depending on the intensity of the earlier breaking, the nourishment either migrates onshore (weak break) or splits into onshore and offshore moving parts (strong break). The relative importance of the diffusion term and the divergence of perturbed sediment flux may lead to a primarily migrating or decaying evolution of nourishment. In storm wave conditions, the nourishment tends to move offshore due to the predominance of return flow driven sediment flux. The sensitivity to wave period and tide are also studied. Model results are consistent with observations, as well as prevailing theory on cross-shore sediment transport. • An idealised one dimensional (cross-shore) morphodynamic model that couples wave, tide and sediment dynamics is developed to study the e_ect and evolution of a shoreface nourishment. • In moderate and mild wave conditions, a nourishment placed well o_shore from the break point induces an overall positive perturbation in sediment ux, resulting in onshore migration (feeder e_ect). Located closer to the break point, the nourishment induces an earlier wave breaking, which dissipates part of the wave energy (lee e_ect), resulting in onshore migration (weak break) or splitting into onshore and o_shore moving parts (strong break). In storm wave conditions, nourishment moves o_shore due to the predominance of return-ow-driven sediment ux. • Tide a_ects nourishment evolution through shifting the relative location of the nourishment and break point. The sediment dynamics at low tide dominate the evolution of the nourishment. [ABSTRACT FROM AUTHOR]

Pile-Rock breakwaters (PRBW) have been constructed as long continuous features in the West Sea of the Mekong Delta. Optimising the gap arrangement and spatial orientation of these continuous breakwaters can result in positive impacts on the velocity field, sediment distribution, and shoreline morphology. In this study, experimental and numerical modelling was performed to investigate the effect of breakwater gaps on bedload sediment transport and nearshore bed morphology. The gap width across various hydrodynamic conditions was found to have a significant impact on bedload sediment transport and nearshore bed morphology. This study found breakwater gaps can result in high current speed and flow due to wave diffraction, which subsequently also accelerates the shoreline and bed erosion process. The gaps also have a positive impact by facilitating sediment supply behind the breakwaters, which enhances the living shoreline. The sediment exchange rate was higher in low water conditions for the emerged breakwater caused by wave circulation stirring up the sediment with higher wave amplitude. During high-water conditions, the results showed a relatively smaller area of sedimentation behind the breakwater. Under high water level conditions, the ability to stir up sediment decreases, resulting in low sediment transport. The findings from this study can be used to optimize the design of pile-rock breakwaters and their performance on the deltaic coast. • Gap arrangement were investigated by physical and numerical models. • 3D wave basin laboratory and 2D Xbeach numerical modelling were applied. • High velocity and flow through the breakwater gaps due to wave diffraction. • The gaps facilitate the sediment supply behind the breakwaters. • The sediment exchange supply is greater in low water conditions and versa. [ABSTRACT FROM AUTHOR]

In this study the numerical model Delft3D is implemented on high-resolution grids to evaluate beach morphological response to groins and submerged breakwaters under sea-breeze conditions. The numerical model is compared with field measurements from three sites on the northern Yucatan coast of Mexico. At these sites, relatively low energy waves with significant wave heights arrive at a steep oblique angle to the coast that drives high sediment transport rates. After calibration of the model, by adjustment of model free parameters, the model results show accurate representations of the diurnal variation of hydrodynamic conditions (wave height and current velocity) driven by the daily sea-breezes. Moreover, the morphodynamic model shows a good representation of the rapid morphological changes, particularly of the accretion pattern caused by a temporary groin and the subsequent recovery following the structure removal. However, erosion patterns at the downdrift areas of structures were not reproduced, owing to the numerical model limitations of simulating swash morphodynamics. Model validation with field observations of the beach response behind submerged breakwaters enabled the model to be used for a parametric study. Following previous work, new equations are developed in the present study that show an improvement for predicting shoreline changes near submerged breakwaters under sea-breeze conditions. Despite the limitations in reproducing downdrift erosion, overall the high-resolution modelling approach satisfactorily simulates the hydrodynamic and the updrift accretion responses to coastal structures on sandy beaches with oblique waves. • Simulations of beach change near groins and submerged breakwaters are performed. • Results are compared to measurements at three sites with high sediment transport rates. • New equations show improved prediction of shoreline change near submerged structures. [ABSTRACT FROM AUTHOR]

Rising sea levels are expected to cause widespread coastal recession over the course of the next century. In this work, new insight into the response of sandy beaches to sea level rise is obtained through a series of comprehensive experiments using monochromatic and random waves in medium scale laboratory wave flumes. Beach profile development from initially planar profiles, and a 2/3 power law profile, exposed to wave conditions that formed barred or bermed profiles and subsequent profile evolution following rises in water level and the same wave conditions are presented. Experiments assess profile response to a step-change in water level as well as the influence of sediment deposition above the still water level (e.g. overwash). A continuity based profile translation model (PTM) is applied to both idealised and measured shoreface profiles, and is used to predict overwash and deposition volumes above the shoreline. Quantitative agreement with the Bruun Rule (and variants of it) is found for measured shoreline recession for both barred and bermed beach profiles. There is some variability between the profiles at equilibrium at the two different water levels. Under these idealised conditions, deviations between the original Bruun Rule, the modification by Rosati et al. (2013) and the PTM model predictions are of the order of 15% and all these model predictions are within ±30% of the observed shoreline recession. Measurements of the recession of individual contour responses, such as the shoreline, may be subject to local profile variability; therefore, a measure of the mean recession of the profile is also obtained by averaging the recession of discrete contours throughout the active profile. The mean recession only requires conservation of volume, not conservation of profile shape, to be consistent with the Bruun Rule concept, and is found to be in better agreement with all three model predictions than the recession measured at the shoreline. [ABSTRACT FROM AUTHOR]

Underneath rock slopes of rubble mound structures often one or more granular filter layers are present. These filter layers prevent base material washout. In contrast to traditional filters, geometrically open filters allow for some movement of base material. In order to design such open filters the amount of erosion and accretion of base material needs to be predicted. Based on 2D physical model tests Van Gent and Wolters (2015) presented a method to estimate the erosion and accretion of sand underneath rock slopes. Since the developed method was only valid for perpendicular wave attack, a new study has been performed to assess effects of oblique wave attack on the amount of erosion and accretion of sand underneath a rock slope. For that purpose 3D physical model tests were performed in a wave basin with 5 different wave angle between 0° (perpendicular wave attack) and 75°. Based on the test results it was shown how the effects of wave obliquity can be taken into account in the design of open filters. In addition, the effect of the storm duration on open filters has been studied. This led to an extended design method to predict the amount of erosion and accretion of sand underneath rock slopes under wave loading. [ABSTRACT FROM AUTHOR]

Disequilibrium-type models for two beach profile parameters, P , the shoreline position and net bulk sediment transport, are developed for laboratory experiments that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates. The model principle follows the classical disequilibrium approach but with non-monotonic relationships between the forcing and the chosen beach profile parameter at equilibrium, P eq , previously verified and presented in part 1 of this work (Baldock et al., 2017). Two such relationships are required to model beach profile evolution that exhibits morphological hysteresis. The model coefficients are derived for monochromatic and random wave experiments and subsequently used to model data obtained from cyclic erosive and accretive wave conditions of shorter durations, alternating through multiple cycles. In these conditions equilibrium conditions were not reached and hysteresis does not occur. The model is used to investigate the morphological feedback between the outer and inner bars and the resulting behaviour of the bulk transport, and the relative depth over the bar crest is shown to be an attractor in this case. The model coefficients and morphological time-scales derived from the cyclic experiments are very similar to those derived from the equilibrium experiments for the bulk transport. Normalised mean square model errors range from 1% to 20% when applied to independent data. The data from the cyclic wave conditions can be inverted to derive the conditions expected at equilibrium, which match those observed, indicating a robust model relationship between the forcing and P eq . The relationship between the forcing and P eq can also be determined directly from the cyclic experiments. This approach may be more robust than determining the relationship from periods where P is stationary since, in a time-series of P versus the forcing, stationary points can occur due to changes in wave conditions, in addition to the instances when P = P eq . [ABSTRACT FROM AUTHOR]

Novel series of experiments are presented that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates. The experiments were conducted in a wave flume at medium scale using both monochromatic and random waves, representing 2D conditions. Beach profiles were obtained with high spatial resolution at frequent intervals with a laser profiler, from which shoreline location, bar position and sediment transport rates were derived. Experiments were conducted for sequences of wave climates, where a sequence comprised of 6–13 sequential tests, each commencing with the beach profile from the preceding test. Each test was run until equilibrium conditions were obtained and had a constant wave height, increased or decreased relative to the preceding test. Cyclical conditions were also included, with erosive and accretive wave conditions of short durations alternating through multiple cycles, so that equilibrium conditions were not reached during a test. With a sequence of increasing wave heights, the relationship between the shoreline position and the bulk cross-shore sediment transport, at equilibrium, was non-monotonic, indicating a maximum in the landward sediment transport rate. For test series comprised of a sequence of increasing wave heights followed by a sequence of decreasing wave heights, morphological hysteresis was observed in the equilibrium shoreline position and bulk cross-shore sediment transport, such that shoreline recession, or offshore transport, continued in some instances after reductions in wave height. This is inconsistent with classical equilibrium type shoreline evolution models. However, when equilibrium conditions were not reached, in the cyclic sequences, no such morphological hysteresis was observed and a dynamic equilibrium is reached. The morphological hysteresis occurs because of the decay, stranding, or increased relative depth, of the breaker bar following a reduction in wave height, often in conjunction with a new breaker bar generated by further offshore transport in the inner surf zone. Similar sequences of morphological response are evident in field data and larger scale tests in the literature. Finally, it is shown that the morphological hysteresis can be explained using the classical equilibrium beach state model of Wright et al. (1985) by introducing the concept of a subsequent alternate active beach state, which may occur following a change in wave conditions. [ABSTRACT FROM AUTHOR]

Coastal dunes provide many ecosystem services including protection of infrastructure from wave overtopping and habitat for native species. Foredunes grow at different rates and assume different forms (i.e., short and wide to tall and narrow) depending on a range of factors including pre-existing beach and dune morphology, wind, wave, and water levels, sediment grain size, and vegetation characteristics, yet the relative importance of these factors on foredune growth is understudied. Here, we quantify foredune evolution (2016–2019) and explore the relative influence of a suite of metocean, sedimentary, and ecological factors for dune growth on three barrier islands in the U.S. North Carolina Outer Banks (Cape Lookout National Seashore). We incorporate observed and hindcast wind, wave, and water level data into the process-based, coupled beach-dune evolution model, Windsurf, to explore the relative contribution of factors likely to influence foredune growth at the annual timescale (2016–2017). Our cross-shore topographic profile observations show varied interannual foredune change rates and characteristics, including horizontal retreat and progradation at the dune toe and vertical erosion and accretion at the dune crest. Model results indicate that, of the factors explored, pre-existing morphology had the greatest influence on the type of foredune growth that occurred (i.e., incipient dune development, widening of the dune, and/or vertical accretion), which dramatically altered the final shape of the dune. Variations in wind and wave climates were associated with the relative contribution of marine- and aeolian-driven bed elevation changes and were particularly influential during storms. In addition, increases in the minimum elevation of vegetation on the dune profile (analogous to the cross-shore distance between the shoreline and established vegetation line, i.e., the vegetation limit, as coined by Duran and Moore, 2013) increased dune crest height and dune volume. Moreover, variations in the minimum vegetation elevation resulted in a larger range of dune crest elevations and dune volumes than differences in the median sand grain size. We suggest that insights into the relative influence of metocean, sedimentary, and ecological factors to dune growth can assist in the development of practical coastal management strategies. • Pre-existing beach-dune morphology had the largest influence on dune growth type. • Exposure to the dominant wave direction led to increased dune volume. • Higher minimum vegetation elevation and finer sand resulted in taller dunes. • Minimum vegetation elevation influenced dune growth more than sand grain size. [ABSTRACT FROM AUTHOR]

The swash zone largely influences nearshore hydrodynamics and morphodynamics through dissipating or reflecting wave energy and controlling whether sediment will be stored on the upper beach or returned to the inner surf zone. It is a region where active beach accretion and erosion occur and beach protection measures such as sand nourishments are often placed. Hence, proper prediction of swash zone beach evolution is required to evaluate beach management scenarios. This paper describes the advances related to swash zone sand transport processes and morphodynamics. We discuss the effects of a variety of physical processes and factors (e.g. bore turbulence, pre-suspended sediment advection, wave-swash interactions, infragravity waves, in−/exfiltration, pressure gradient and bed slope) on sand transport in the swash zone. We then focus on practical models of swash zone sand transport which are appropriate for predicting longer term (days to years) beach evolutions. Three types of practical models, i.e. empirical sand transport formulae, sand transport distribution methods and equilibrium models, are identified. The strengths and limitations of these practical models are discussed. The empirical sand transport formulae include the intra-swash formulae and swash-averaged formulae. The intra-swash formulae are more physics-based and can take physical processes into account more explicitly. However, upscaling of them for modelling sand transport and morphological changes over tidal cycles or longer term is problematic due to the difficulty in obtaining reliable and accurate instantaneous swash hydrodynamics(e.g. flow velocities) and due to the error propagation. Swash-averaged formulae can be more suitable for predicting longer-term morphological changes while they still require better parameterisations of important physical processes (e.g. wave-swash interactions). Sand transport distribution methods generally work reasonably well for beach erosion under energetic wave conditions whereas they have the inability to predict the beach recovery under mild wave conditions. Equilibrium models show a potential for predicting the beach evolution under both erosive and accretive conditions well. The equilibrium slope appears to be an essential factor that largely determines the performance of the equilibrium models. This equilibrium slope should depend on wave conditions and sediment characteristics, and a quantitative relationship between them needs further research in order to make the equilibrium models more predictive. [ABSTRACT FROM AUTHOR]

Experimental results involving shoreface nourishment scenarios are presented. The experiments are performed at small scale and the effects of nourishment placement and timing in relation to long-term cross-shore profile development are investigated. Four different nourishment scenarios are tested experimentally, with nourishment positioned both in the trough of a pre-developed profile as well as along the bar of the profile. The results demonstrate that under all scenarios the erosion of the shoreline slows relative to the case without nourishment. The two cases where the nourishment was placed along the bar reduced erosion of the shoreline more compared to the two cases with nourishment in the trough onshore of the bar. Compared to past experiments on nourishment presented in the literature, the present experiments were run for a longer duration, and the concepts of equilibrium profile and the development towards such an equilibrium were investigated. Curiously, the experiments showed a reversal of the sediment transport rate from being primarily offshore directed across the entire profile to onshore directed in the inner surf zone region closest to the shoreline. This reversal of transport rate occurred without changing the incoming wave conditions and resulted in deposition at the shoreline. This either questions the existence of equilibrium beach profiles or at the very least shows that the development towards such an equilibrium will not always be monotonic in time. • Shoreface nourishments are performed at model scale investigating the influence of timing and placement on long term profile development. • Placement of nourishment can disturb the cross-shore profile shape over long time. • After long time running with the same wave climate the transport rate changed from offshore directed to onshore directed in the inner surf zone. • The change in sign was related to cessation of wave-breaking and resulted in sand returning to an otherwise eroding beach. [ABSTRACT FROM AUTHOR]

Beach accretion is the natural mechanism that allows dry beaches to recover. Human response to climate change produces hardening of the coasts and the incident marine climate, which increases beach erosion produced during winter and prevents a full recovery during summer. Beach nourishments are performed all around the world to fight coastal erosion with a nature-friendly philosophy. Softer techniques as beach scraping are also widely applied. A kind of beach scraping is proposed here as an innovative nature-assisted beach enhancement technique, that aims to accelerate naturally produced sand accretion on the beach profile. It consists of mechanically ploughing the intertidal area of a beach to create ridges and furrows. Prototype-scale laboratory experiments were performed to analyse its effectiveness under controlled conditions. Seven 1 h tests having different water levels and the same initial bottom geometry and sea state conditions (H s = 0.3 m, T p = 7 s) were performed. Sea state, sand, and initial slope characteristics assured accretive conditions. Ploughed and flatbed initial slope geometries were simultaneously tested into two sub-channels of the wave flume. The results indicate that the bottom roughness is 3.57 times larger for the ploughed geometry. Consequently, wave energy dissipation is larger for the ploughed geometry, and therefore, the significant wave height at the shoreward end of the study area is 11% smaller for the ploughed geometry. This smaller wave height under the ploughed morphology leads to more accretive conditions, as observed from the measured onshore sediment transport, which is 2.9 times larger than the natural transport, and the larger accreted sediment volume in all seven test cases. These results demonstrate the effectiveness of ploughing to enhance natural beach accretion under highly probable accretion conditions. Further research is required to define the thresholds of marine conditions in which the potential of beach ploughing can be exploded. • Working with nature. • Ploughing the intertidal area of a beach enhances natural accretion. • Real scale laboratory experiments measuring sediment transport. • Mechanically ploughing increases bed roughness. • Extra wave energy dissipation is produced by ploughing. [ABSTRACT FROM AUTHOR]

Estuarine beaches often lack well developed surf zones; incident waves break and convert directly to swash on the steep foreshore, resulting in greater influence of the swash zone in generating longshore flows and sediment transport. This study was conducted to evaluate longshore sediment transport in the swash zone of an eroding estuarine beach and relate transport rates to changes in beach position and volume downdrift of a shore-perpendicular structure. Field data were gathered on a sandy beach on the bay side of Fire Island, New York, USA in a short fetch (12–15 km) microtidal (mean range 0.21 m) environment. Wave and swash processes, beach changes and sediment tracer and trapping experiments were conducted during strong onshore winds in March and April 2012. Daily topographic surveys of the beach revealed pulses of sediment movement alongshore at small temporal (daily) and spatial (5 m) scales. The mid foreshore retreated 2.75 m from the beginning to the end of the 24 days of monitoring. This retreat was associated with a loss of 2.1 m 3 of sediment per meter of shoreline length. The greatest amount of foreshore retreat during a single storm event was 1.27 m, associated with a volume loss of 0.9 m 3 of sediment per meter. Mean wind speed on that day was 11.3 m s − 1 with a maximum of 18.2 m s − 1 ; significant offshore wave height at the time of maximum wind speed was 0.30 m. Mean significant wave heights ranged from 0.12 to 0.26 m during the five times when trapping occurred, resulting in mean longshore swash velocities of 0.08 to 0.23 m s − 1 and transport rates ranging from 0.413 to 1.516 m 3 h − 1 . The longshore sediment transport rates are similar to rates gathered under similar longshore current velocities on microtidal low energy beaches. Transport rates on beaches in sheltered environments can differ from rates calculated using existing formulas that may be more appropriate for high-energy beaches, where a greater proportion of sediment is transported in the surf zone than in the energetic swash zone under plunging breakers. Transport rates calculated from three existing formulae (Bagnold, 1963, CERC, 1984, Kamphuis, 2002) revealed that estimates from Bagnold compared most favorably with measured rates because of direct measurements of longshore current velocities. Rates of erosion on beaches in short fetch environments can be high despite low wave energies because the low, narrow beaches have little volume, magnifying the importance of seemingly low rates of transport in the swash. [ABSTRACT FROM AUTHOR]

A moderate-size (344,000 m3) subaerial beach nourishment was placed in 2012 in front of flood-prone homes at Imperial Beach, California. The subaerially persistent coarser-than-native nourishment sand spread alongshore over a ∼ 4 km span. By winter 2018/19 subaerial sand volumes in front of the flood-prone homes were eroded to near pre-nourishment levels, while sand accumulated near a river mouth ∼ 1.5 km to the south. The observed alongshore patterns of post-nourishment erosion/accretion are consistent with the modeled convergence/divergence of alongshore currents driven by wave radiation stress S x y gradients associated with refraction over a relic cobble ebb shoal. The same alongshore patterns of subaerial erosion/accretion were observed in the 6 years preceding the nourishment, indicating a wave-driven erosion hotspot in front of the flood-prone homes, and an accretion hotspot near the region of river mouth migration. Over the 13-yr observation period, the river mouth migrated 600 m southward and closed in 2016, possibly owing to nourishment sand and El Niño intensified local drift convergence. The computationally efficient drift (radiation stress) gradient model uses simplified wave and surfzone dynamics, assumes proportionality between alongshore sediment transport and the radiation stress component S x y , but nevertheless captures the overall patterns of alongshore nourishment evolution and provides a framework to inform sand management. • The subaerial influence of relatively coarse beach nourishment sand spans 4 km of coast 6 years after placement. • Accretion and erosion hotspots are persistent, 6 years before and after nourishment. • A simple drift divergence model that captures refraction over an ebb shoal describes the alongshore variable sand volume trends. [ABSTRACT FROM AUTHOR]

Shorelines bordering ebb deltas are often subject to deformation by the approach and attachment of ebb-tidal shoals. Although this is a common behaviour, little attention has been paid to the link between shoal migration and the multi-annual development of the adjacent beach-dune system. This study aims to understand beach-dune systems' behaviour during the approach phase of an ebb-tidal shoal attachment event. Topographic and bathymetric data of the barrier island of Texel (NL) was used to calculate shoreline position, beach and dune volume, dunefoot position, and shoal displacement rates. Two classical beach-dune interaction models were used to understand the observed behaviour: the surfzone-beach-dune model and the sediment budget model. The analysis revealed how a larger bank on the land-facing side of the ebb delta split into two smaller shoals with different morphological behaviours. One of the shoals (S1) moved consistently landwards, recently attaching the shore, whereas the second shoal (S2) is still evolving and presents a milder landward movement than S1. In parallel to the landward movement of S1, the adjacent coastline was subject to erosion, partially counterbalanced by nourishments. However, despite the erosion, dunes are growing in volume, suggesting a net positive transfer of sand from the beach to the dunes. In the surfzone-beach-dune model, regular nourishments positively affect beach state by maintaining sufficient beach size for aeolian sediment transport and reducing shoreline erosion. In the budget model, dune volume growth may occur despite a slightly negative beach budget. Framing Texel in the budget model implies that the beach budget before the start of the approach phase is crucial in defining the behaviour of the dune system during this phase. If the shoal approach significantly reduces the beach budget, the system may cross the budget threshold that dune building is possible. Thus, the dune system may evolve to an erosional state, including dune ridge dissection and blowout development. Hence, nourishments have been essential in keeping the current morphological state during the attachment of the shoal, as they restrict the system from crossing the negative morphological threshold. Thus, without the nourishments, beach erosion driven by the shoal might have led to morphological changes in the dune system that could lead to years of a weakened level of protection until foredune recovery after attachment. • Shoal-induced changes in beach budget influence dune development. • Dune morphology may change depending on the beach state prior to attachment. • Nourishments can retain beach budget at a sufficient level to maintain dune morphology. [ABSTRACT FROM AUTHOR]

Estimating sediment budget is a challenge that requires understanding the morphological relationship between the subaerial beach and the upper and lower shoreface. Based on a unique dataset of monthly measured topographic and bathymetric measurements, this study describes the morphodynamics of the subaerial and subtidal sections of a highly-dynamic beach over a 5-year period (2015–2020). Typically, the beach presents a longshore bar trough (LBT) state at the end of the winter, driven by net offshore sediment transport. The nearshore morphology evolves into more reflective states (rhythmic bar beach, RBB; transverse bar rip, TBR; and low tide terrace, LTT) driven by onshore sediment transport when the incident wave-energy decreases over the spring and summer. Seasonal variations of the incident wave-energy resulted in large subaerial-subtidal exchanges of sediment (200–300 m3 m−1), but these exchanges were an order of magnitude smaller in yearly scales. Subaerial and upper-shoreface morphological changes varied alongshore. Larger variations existed in the south, influenced by persistent rip channels. Instead, alongshore processes resulting from changes in wave direction may control the morphodynamics in the center and north. The subtidal section in north and center gained significant amount of sand (300 m3 m−1) during high-energy conditions, which contributed to a net annual gain of 60 m3 m−1. The origin of that sediment is currently unknown, it could have bypassed from an adjacent beach, shifted alongshore or inputted from the lower shoreface deeper than the depth of closure. This research shows the presence of very large monthly-to-seasonal total volume fluctuations relative to net annual or multi-annual changes, and highlights that comparatively small additions to the annual sediment budget could potentially contribute to the long-term stability of the beach. • Largest morphological variations in the south influenced by persistent rip channels. • Very large monthly-to-seasonal volume fluctuations relative to net annual changes. • Small additions to the annual budget could contribute to long-term beach stability. [ABSTRACT FROM AUTHOR]

Coastal processes along the Munambam to Chettuwa coastline located at the south-west part of India have been studied to understand the role of a mudbank and artificial structures like breakwaters in causing shoreline changes. The mudbank occurring along this coast is different from those in South America, Lousiana and China. The morphology and coastal processes of the coast have been studied by collecting nearshore and beach data from 2009 to 2013. Location of the mudbank area has been shifting over the years from north to south. The beach at the mudbank and its north is accreting while the southern side is eroding. Harbor breakwaters and seawalls are other factors influencing beach stability. An erosion hotspot along this mudbank coast is identified and management interventions proposed based on numerical model studies using MIKE 21 SW model and LITPACK. The model results are calibrated and validated with field observations. Sediment transport along this sector was estimated using LITDRIFT module. Shoreline change was calculated using the LITLINE module. The production run was carried out with different management options and the most suitable option is recommended for the eroding sector. The other sectors do not require any intervention to sustain the beaches. [ABSTRACT FROM AUTHOR]

The typically curved and stable planform shape of embayed beaches is often observed in the presence of rigid headlands. The long-term alongshore equilibrium shape is variable and is controlled by headland geometry, cellular circulation patterns and wave obliquity at the shoreline. We use a process-based morphological model to simulate the development of embayed beaches depending on different environmental conditions and geological settings (i.e., topography and geometry). The embayment is allowed to develop from an initially straight beach to one which is curved under idealized wave forcing conditions and without external sediment input. Bay development can be approximated with an exponential function with coefficients representing rate of growth and bay size. Long-term shoreline cutback is both uniform (shoreline translation) and non-uniform (shoreline rotation) and is parameterized. Alongshore gradients in flow and transport patterns are related to long-term non-uniform shoreline cutback. Rotation of the beach ceases as the bay matures, leading to a curved shoreline planform, which is a remnant of decaying erosion processes. [ABSTRACT FROM AUTHOR]

At wave-dominated coasts, it is common the presence of coastal barriers that can be of different typologies and whose dynamics can influence the formation of lagoon systems. Along southeastern and south Brazil the dynamics involving barrier-lagoon evolution is related to wave and aeolian process associated with sea-level behavior. For a better understanding about the relationship regarding to coastal process, barriers, and lagoons the application of geophysical techniques enables to identify morphostratigraphic characteristics improving the acknowledgment of the main processes forming these morphologies. In this study, a 1.4 km long common-offset GPR profile, in cross-shore direction, was surveyed in order to obtain the internal depositional architecture of the sandy coastal barrier to the east of Salgada lagoon, located in the wave-dominated Paraiba do Sul river delta, in southeastern Brazil. The GPR allows to describe morphostratigraphic characteristics imprinted by sediment dynamics and how it is related to the lagoon system formation. Eight radarfacies were identified, grouped according to the coastal barrier pattern, divided in barrier spit and beach ridge, and sediment transport characteristics. Five radarfacies comprise the barrier spit environment and three the beach ridge environment. The barrier spit environment radarfacies showed different characteristics of the portions of the spit sequence (initial, medium or distal), and along with its subsurface imaging angle (parallel, oblique or transversal to the spit growth direction) providing highly detailed data regarding those barrier types. This recognition allowed the interpretation of a previous spit, approximately 3 m deep, located under another one that overlapped it. Also, spit accretion records were found, which occur due to the seaward exposure to high-angle wave action. Meanwhile, the beach ridge environment radarfacies revealed the typical pattern of progradation due to swash processes, and also the occurrence of berm ridge accretion and overtopping/overwashing processes. The integrated analyses using the subsurface data indicated that the evolution of the targeted coastal barriers and the lagoon can be divided into four stages. The first stage is the most landward barrier spits growth, where Salgada lagoon was beginning its closing process. This is followed by the second stage with the continuity of barrier spits growth but with changes in spits orientation. The third stage represents an erosive phase, with a major erosive truncation that probably eroded a significant area of the spits. At the last stage suggested there was a subsequent accumulation phase, marked by the formation beach ridges. Besides that, it is also important to recognize that the development of coastal barriers of different types at the site showed an alignment variability of paleocoastlines. While barrier spits revealed variation in their orientation, beach ridges have kept their alignment more constant. This fact occurred independently of erosive episodes. Furthermore, the GPR profile acquisition strategy made it possible to investigate the spit from different perspectives, which helped with the interpretation of deeper radarfacies. • Different morphostratigraphic patterns observed from barrier spit to subsequent beach ridges formation identified using GPR. • Lagoon enclosing related to the regressive barrier spit development; barrier spit set erosion; and beach ridges set formation. • Landscape evolution proposal with four main phases in a highly dynamic coastal area in a wave-dominated deltaic context. • Understanding lagoon and coastal barriers evolution contributes to sedimentary capes developed during Holocene knowledge. [ABSTRACT FROM AUTHOR]

A field-based experimental study of beach scarp morphodynamic evolution was conducted on the shoreface of a macrotidal sandy beach subject to storms combined with spring tide events (Luc-sur-Mer, France). Both video and in-situ measurements on an artificial berm are used to understand beach scarp evolution over one tide during stormy conditions. Image time stacks are used to analyze the swash action on the beach scarp and topographical data of the scarp are recorded with a terrestrial scanner laser to quantify the morphodynamic response of the beach scarp to wave action. This work provides a new and unique dataset about beach scarp changes and berm morphology in particular under rising tide and oblique wind-wave conditions. During one stormy event, the berm was completely destroyed. However, contrasting alongshore changes were measured during the erosive phase with different crest and foot scarp retreats and eroded volumes between the west and the east side of the berm. The beach in front of the scarp also shows a contrasting residual evolution, indicating an evident longshore sediment transport on the study area as a consequence of incident oblique wave conditions. A strong connection between beach evolution and beach scarp changes is clearly identified. The scarp erosion increases on the west side of the berm when the beach level is lowered and reduces when the beach surface rises on the east side. The beach slope and foreshore elevation as a result of a longshore sediment transport between east and west profiles, influence swash activity. Overall, water depth and swash activity became progressively different along the scarp during the experiment. Swash measurements indicate that the presence of the beach scarp strongly influences the swash motion. At high tide, the reflection of the uprush on the scarp front induces a collision between the reflected backwash and the following uprush dynamic. These collisions reduce and sometimes stop the motion of the following uprush, reducing the incoming swash excursion. Consequently, the scarp presence modifies the swash interaction that normally appears on a planar beach surface. With a beach scarp, the swash energy level is substantially attenuated and its spectrum is characterized by a large band. The number of uprush impacts on the scarp front calculated from video images reaches about 25 per 5 min. In spite of the swash energy attenuation due to swash/swash interactions, these impacts provoke the berm destruction in about two hours. However, the onshore migration of the swash zone induced by the rising tide appears to be important to explain scarp destruction, compensating the attenuated swash activity due to backwash-uprush interactions. [ABSTRACT FROM AUTHOR]

Understanding time scales of beach response (erosion and recovery) to extreme storms is particularly relevant for management of coastal land and risk. Observations show that rock-bounded platform beaches are generally remarkably stable and only occasionally respond to extreme storm wave forcing with abrupt morphological changes. The present work aims to understand the conditions leading to the disruption of beach stability (storm thresholds for morphological changes) and to comprehend the conditions of the subsequent recovery. Results obtained at two rock-bounded beaches of the western Portuguese coast over five years provided the foundations of a new conceptual morphodynamic model. This model explains abrupt beach disruption as a consequence of full inundation of the beach profile during extreme storms, together with strong wave reflection at the rigid landward boundary, causing major erosion of the subaerial beach. We argue that the timescale of post-storm recovery depends essentially on the fate of the sediment transported offshore during the storm event. If sediments remain within the beach sediment cell (underwater beach section) beach recovery to pre-storm conditions is very fast, while recovery is much slower if sediments exit the beach sediment cell. In the latter case, beach recovery depends on external sand sources, which can lead to recovery time scales of several years. • We investigate conditions leading to abrupt morphological changes in rock-bounded platform beaches. • Total water level adequately describes thresholds for significant erosion during major storms. • A conceptual model explaining patterns of erosion and recovery is proposed. • Abrupt erosion is triggered by wave reflection at the landward hard boundary of the beach. • Beach recovery depends on the geological framework, which controls sediment exchanges with adjacent sediment cells. [ABSTRACT FROM AUTHOR]

Excessive erosion of sand beaches defines a serious problem worldwide and is particularly pronounced in the Mediterranean region. One of the typical measures for alleviating this erosion consists in building rigid breakwaters in the vicinity of the coast for diminishing sand transport. This solution, however, is often accompanied by undesirable alteration of the coastline. In this work we address the viability of using conceptually new structures with inflatable elements striving to improve the control over the sediment transport. The aim of the inflatable element is to adapt the breakwater configuration to the sea state. A preliminary design is proposed and tested in a number of storm scenarios using an in-house finite element/level set model. Influence of various breakwater design parameters upon its functionality is studied. Transmission coefficients and maximum pressures exerted upon the breakwater are estimated. Numerical study performed shows that for the considered range of storm scenarios the proposed design is characterized by transmission coefficients below 0.5. It is also shown that the use of inflatable elements facilitates adaptation of the breakwater functionality to a given sea state. • An adaptive breakwater: inflatable tubes on top of an immersed rigid platform. • Performance studied via in-house enhanced FEM/level-set model. • Transmission coefficients and flow characteristics estimated for various storm scenarios. • Design parameters' influence upon efficiency of the breakwater studied. • Breakwater's ability of adapting to storm conditions shown. [ABSTRACT FROM AUTHOR]

The field observation at two neighboring beaches showed significant effects of berm height on beach profile changes during a major storm. The fully nonlinear Boussinesq wave model, FUNWAVE-TVD, with a sediment transport module was used to simulate the beach erosion processes of the two beaches. The model reproduced the beach profile changes in good agreement with the measured data. The model results revealed that, for the beach with a higher berm, the wave force, wave-induced undertow flow, along with the higher sediment concentration on the berm induce more offshore sediment transport and cause significant beach profile changes compared to the beach with a lower berm. The erosion trend with different berm heights was predicted by using a series of numerical tests with different berm heights and offshore forcing conditions. The test results suggested that beach erosion increases with the berm height until the berm height reaches a certain level. • Field observation erosion/deposition shows pattern different storm-induced between two neighboring beaches. • The sediment module in the Boussinesq model, FUNWAVETVD, is validated against measured morphological data for the first time for the wind wave conditions. • Trend of beach erosion with different heights of beach berm is investigated. [ABSTRACT FROM AUTHOR]

Abstract: Numerical cross-shore profile evolution models have been good at predicting beach erosion during storm conditions, but have difficulty in predicting the accretion of the beach during calm periods. This paper describes the progress made in modifying and applying the public domain XBeach code to the prediction and explanation of the observed behaviour of coarse-grained beaches in the laboratory and the field under accretive conditions. The paper outlines in details the changes made to the original code (version 12), including the introduction of a new morphological module based upon Soulsby's sediment transport equation for waves and currents, and the incorporation of Packwood's infiltration approach in the unsaturated area of the swash region. The competence of this modified model during calm conditions for describing the steepening of the profile, and the growth of the beach berm is demonstrated. Preliminary results on the behaviour of the beach subject to both waves and tides are presented. Good agreement is found between the model simulations and large-scale laboratory measurements, as well as field observations from a composite beach in the UK. The reasons for the model's capabilities are discussed. [Copyright &y& Elsevier]

Beaches are dynamic systems characterized by frequent morphological changes due to storm events, gradients in longshore sediment transport, seasonal variations in wave climate and more. The complexity of variations in beach morphology can increase significantly after a beach nourishment, particularly when coastal structures are involved. This study investigates the impacts of a groin field, consisting of both notched and traditional groins, on the morphological evolution of a beach in Deal, New Jersey, USA. More specifically, an evaluation of the performance and specifications of the notched groins is undertaken. In 2016, the beach in Deal was nourished and three of the eight groins comprising the groin field were concurrently notched in order to promote increased movement of longshore sediment transport while maintaining a stable shoreline. The study site was monitored nine times over a period of two years (2018–2019) using Unmanned Aerial Systems Structure from Motion (UAS-SfM) photogrammetry. The near-term morphological response of the study site was evaluated by analyzing high-resolution digital elevation models (DEMs) and longshore sediment transport estimates based on measured wave data. The elevation change maps established that in general, the groin notching was partially successful in reducing shoreline asymmetry in consequence of sediment transport bypassing through the notches. Differences in behavior and patterns of elevation change adjacent to each individual notched groin was observed even though they were all notched according to the same specifications. While all three notched groins were effective in stabilizing the adjacent shoreline, they varied in their effectiveness at promoting longshore sediment transport through the notch. This is likely attributable to the relative location of the notched groins within the groin field and the characteristics of the post-nourishment morphological evolution; the direction of net annual longshore sediment transport at Deal beach is northward, which caused the southern areas of the study site to narrow and the northern areas of the study site to widen. Consequently, the notched groins in the wider sections of beach did not function as intended, as the notches filled in with sediment causing them to mimic the behavior of a traditional groin, including restricted longshore sediment transport and significant erosion/accretion offsets. In the narrower section of beach, the notched groin functioned as designed, such that the notch was located in the swash zone and therefore allowed bi-directional sediment transport and maintained a stable and relatively symmetrical shoreline. Thus, the notched groins performed most effectively when the notch was consistently located toward the seaward end of the swash zone. • Groin notches function optimally when the notch is located in the swash zone. • Improperly constructed notches can fill-in with sediment and behave like traditional groins. • Notch specifications can vary to account for position and uncertainty in the equilibrated beach. • Notch designs should reflect the direction and magnitude of net longshore sediment transport. [ABSTRACT FROM AUTHOR]

Abstract: Mechanisms through which naturally-occurring hard landforms, such as rock and coral reefs, influence coastal sediment transport are still poorly understood. Therefore, field investigations were undertaken during storm conditions on the sandy beaches of Yanchep Lagoon in southwestern Australia, which are perched on Quaternary limestone reefs. During two consecutive winter storms, the response of three subaerial beach profiles were quantified at: (a) an Exposed Profile which was fronted to seaward by a predominantly sandy substrate; (b) a Reef Profile that was fronted directly seaward by limestone outcrops submerged below mean sea level; and (c) a Bluff Profile where the dry beach was perched on a limestone bluff that reached above mean sea level and that contained a shallow coastal lagoon. The subaerial beach response to the storms had considerable spatial variation alongshore and was strongly dependent on the local rock topography. The Exposed Profile eroded most with a 2m-high scarp cut into the dune while the dunes at the Reef and Bluff Profiles were stable. The Bluff Profile also eroded considerably and the coastal lagoon widened and deepened. The Reef Profile was the most stable overall because erosion was balanced by short periods of accretion during the storm period which was partly due to sediment supplied by longshore transport through the coastal lagoon from the Bluff Profile. During the month after the storms wave energy was relatively low and the beach at the Exposed Profile accreted almost to the pre-storm volume, although the scarp in the dune was still present. The Reef Profile accreted most in the month after the storms while recovery at the Bluff Profile was low. It appeared that the bluff inhibited onshore sediment transport during and after the storms and in addition, strong currents in the lagoon transported sediment alongshore to supply the other beach profiles. These observations indicated that rock topography, especially elevation relative to sea level determined if beach erosion was reduced during storms and whether accretion was dampened in the post-storm recovery phase. [Copyright &y& Elsevier]

Abstract: This paper describes field measurements that document the formation of barchan dunes in the Moroccan Atlantic Sahara desert. The first mechanism described is the transformation of patches and proto-dunes at Cap Juby beach to barchan dunes of elementary size. This transformation is discussed in relation to the wind speed and saturation length. The second mechanism is the ejection of small barchans of elementary size by other small barchans in response to the perturbation of the target barchan by two other impacting small barchans. This remote initiation is discussed in relation to the bulk flux transported by the barchan dunes involved in this interaction and to their morphology. Other modes of barchan initiation observed in the field are also presented. [Copyright &y& Elsevier]

Abstract: Future shoreline changes on a sandy beach with a structure such as a jetty or groin can be estimated when wave time series is known (i.e. sequence of wave height, period, and direction). This paper presents an extension of an existing solution () for the linearized partial differential equation for shoreline change at an infinite jetty where waves are time varying and when the angle of the shoreline is small with respect to the waves breaking at the shoreline. The novel solution provided in this paper allows the previous constant wave condition solution to be extended to the case where wave properties (i.e. wave direction, wave height, and wave period) are time varying. Example usage of the method presented shows that shorelines may be of different final plan form shape for time varying wave conditions even though the sediment transport along adjacent beaches is not spatially varying (i.e. spatially constant) from time step to time step. Although this difference in shape may have been known previously using numerical models, it could not be proved analytically. Reversals of wave height, period, and direction time series are shown to provide different final shoreline shapes even though the time series consists of the same waves although in different ordered time. The solution provided will allow one line numerical shoreline models to be tested using an analytic solution. [Copyright &y& Elsevier]

Abstract: Mixed beaches, with poorly sorted grains of multiple sizes, are a common and globally distributed shoreline type. Despite this, rates and mechanisms of sediment transport on mixed beaches are poorly understood. A series of tracer deployments using native clasts implanted with Radio Frequency Identifier (RFID) tags was used to develop a better understanding of sediment transport directions and magnitudes on the mixed grain-size beach of the Elwha River delta. Using tracer samples selected to match the distribution of the coarse fraction on the beach we find that all grain sizes, up to large cobbles (128–256mm), were mobile under most measured wave conditions and move in relationship to the direction of the alongshore component of wave energy as estimated by incident breaking wave angles. In locations where the breaking wave is normal to the shoreline we find that tracers move in both alongshore directions with approximately equal frequency. In locations where breaking waves are oblique to the shoreline we find that alongshore transport is more unidirectional and tracers can approach average velocities of 100m/day under winter wave conditions. We use the tracer cloud to estimate the beach active width, the mobile layer depth and sediment velocity. Our results suggest that, while sediment velocity increases under increased incident wave angles, the active layer depth and width decrease, reducing sediment flux at the site with the more oblique breaking waves. This result is contrary to what is suggested by traditional wave energy transport models of alongshore sediment transport. [Copyright &y& Elsevier]

Abstract: New large-scale laboratory data are presented on the influence of long waves, bichromatic wave groups and random waves on sediment transport in the surf and swash zones. Physical model testing was performed in the large-scale CIEM wave flume at UPC, Barcelona, as part of the SUSCO (swash zone response under grouping storm conditions) experiment in the Hydralab III program (Vicinanza et al., 2010). Fourteen different wave conditions were used, encompassing monochromatic waves, bichromatic wave groups and random waves. The experiments were designed specifically to compare variations in beach profile evolution between monochromatic waves and unsteady waves with the same mean energy flux. Each test commenced with approximately the same initial profile. The monochromatic conditions were perturbed with free long waves, and then subsequently substituted with bichromatic wave groups with different bandwidth and with random waves with varying groupiness. Beach profile measurements were made at half-hourly and hourly intervals, from which net cross-shore transport rates were calculated for the different wave conditions. Pairs of experiments with slightly different bandwidth or wave grouping show very similar net cross-shore sediment transport patterns, giving high confidence to the data set. Consistent with recent small-scale experiments, the data clearly show that in comparison to monochromatic conditions the bichromatic wave groups reduce onshore transport during accretive conditions and increase offshore transport during erosive conditions. The random waves have a similar influence to the bichromatic wave groups, promoting offshore transport, in comparison to the monochromatic conditions. The data also indicate that the free long waves promote onshore transport, but the conclusions are more tentative as a result of a few errors in the test schedule and modifications to the setup which reduced testing time. The experiments suggest that the inclusion of long wave and wave group sediment transport is important for improved near-shore morphological modeling of cross-shore beach profile evolution, and they provide a very comprehensive and controlled series of tests for evaluating numerical models. It is suggested that the large change in the beach response between monochromatic conditions and wave group conditions is a result of the increased significant and maximum wave heights in the wave groups, as much as the presence of the forced and free long waves induced by the groupiness. The equilibrium state model concept can provide a heuristic explanation of the influence of the wave groups on the bulk beach profile response if their effective relative fall velocity is larger than that of monochromatic waves with the same incident energy flux. [Copyright &y& Elsevier]

Abstract: This study focuses on barred beach shoreface nourishments physically simulated in a wave flume. The attack of a schematic storm on three different nourishments is analysed. The apex and waning storm phases lead respectively to offshore and onshore sediment transports. Nourishments in the trough and on the outer bar feed the bar and increase wave dissipation offshore. The bar acts as a wave filter and reduces shore erosion (lee effect). In contrast, nourishment on the beach face leads mostly to shore feeding and reconstruction (feeder effect). With successive nourishments, the beach face clearly becomes steeper and onshore sediment transport is reduced during moderate wave climates. The surface grain size analysis reveals marked variations. Coarser sediments are sorted on the bar and the upper beach face. These locations correspond to large wave dissipation zones during the storm apex. [ABSTRACT FROM AUTHOR]

Abstract: In-situ and laboratory-based magnetic measurements were made on sand samples from the beach on the eastern side of Point Pelee National Park (PPNP) in northwestern Lake Erie, in order to examine both the composition and spatial distribution of magnetic minerals. Magnetic remanence measurements on bulk and particle size fractions showed that the magnetic properties were dominated by multidomain ferrimagnetic grains, probably magnetite and/or maghemite. Particle size-specific measurements on different grain size fractions showed that the <250μm fraction of the beach sands was responsible for the majority of the bulk magnetic signal and that these magnetic grains, and other dense minerals, were concentrated into the finer fractions by sorting processes. Selective entrainment and erosion of lighter quartz minerals lead to concentration of heavy magnetic minerals as placer deposits in the finer fractions. Highest in-situ magnetic susceptibility values were observed in the mid-back beach sands where the beach was the narrowest and had experienced significant erosion in the past. Lowest magnetic susceptibility values were in beach areas which were wider and appeared to be less sensitive to erosion; therefore magnetic susceptibility provided a useful proxy for mapping erosion along the PPNP beaches. Mapping in-situ magnetic susceptibility along the 8.9km length of eastern PPNP identified 2.4km (31%) of the beach where erosion was high and where efforts to minimize erosion should be directed. This technique can be applied to a wide range of sedimentary settings and permits quantitative identification of areas of erosion and better targeting of mitigation measures aimed at reducing the impacts of erosion. [ABSTRACT FROM AUTHOR]

Abstract: State-of-the-art morphodynamic field data were collected from Slapton Sands (UK), a fine-gravel beach (D 50 =2–10mm), over a 10-day period under a range of wave–tide conditions, comprising a mixture of southerly swell and easterly wind waves (H s =0.5–1m; T s =4–8s; tide range=3–4m). Over the field period, the upper beach experienced accretion and berm formation during tides with low steepness, swell-dominated wave conditions (H/L <0.01), and underwent erosion during tides dominated by high steepness wind waves (H/L >0.01). Surprisingly, the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves, and suggests that upper beach morphological change can be decoupled from the overall sediment budget. A submerged accretionary feature (the beach step) grew and migrated onshore on the rising tide, typically reaching a maximum relief of around 0.5m, then gradually decreased in prominence while migrating offshore as the tide fell, resulting in little net morphological change. The step was better developed during the falling tide than the rising tide and, through its control on the swash hydro- and sediment dynamics, the step had a significant effect on the development of the berm. Swash flow velocities under the conditions measured were often in excess of 2ms−1 for both the uprush and the backwash. Onshore mean flows occurred in the upper swash region (<40% inundation), while the lower swash region (>40% inundation) was characterised by offshore mean flows. Swash infiltration losses in the swash zone increased from 40% in the lower swash region to 100% in the upper swash region. The most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone (90–100% inundation). [Copyright &y& Elsevier]

Abstract: Sediment supply provides a fundamental control on the morphology of river deltas, and humans have significantly modified these supplies for centuries. Here we examine the effects of almost a century of sediment supply reduction from the damming of the Elwha River in Washington on shoreline position and beach morphology of its wave-dominated delta. The mean rate of shoreline erosion during 1939–2006 is ~0.6 m/yr, which is equivalent to ~24,000 m3/yr of sediment divergence in the littoral cell, a rate approximately equal to 25–50% of the littoral-grade sediment trapped by the dams. Semi-annual surveys between 2004 and 2007 show that most erosion occurs during the winter with lower rates of change in the summer. Shoreline change and morphology also differ spatially. Negligible shoreline change has occurred updrift (west) of the river mouth, where the beach is mixed sand to cobble, cuspate, and reflective. The beach downdrift (east) of the river mouth has had significant and persistent erosion, but this beach differs in that it has a reflective foreshore with a dissipative low-tide terrace. Downdrift beach erosion results from foreshore retreat, which broadens the low-tide terrace with time, and the rate of this kind of erosion has increased significantly from ~0.8 m/yr during 1939–1990 to ~1.4 m/yr during 1990–2006. Erosion rates for the downdrift beach derived from the 2004–2007 topographic surveys vary between 0 and 13 m/yr, with an average of 3.8 m/yr. We note that the low-tide terrace is significantly coarser (mean grain size ~100 mm) than the foreshore (mean grain size ~30 mm), a pattern contrary to the typical observation of fining low-tide terraces in the region and worldwide. Because this cobble low-tide terrace is created by foreshore erosion, has been steady over intervals of at least years, is predicted to have negligible longshore transport compared to the foreshore portion of the beach, and is inconsistent with oral history of abundant shellfish collections from the low-tide beach, we suggest that it is an armored layer of cobble clasts that are not generally competent in the physical setting of the delta. Thus, the cobble low-tide terrace is very likely a geomorphological feature caused by coastal erosion of a coastal plain and delta, which in turn is related to the impacts of the dams on the Elwha River to sediment fluxes to the coast. [Copyright &y& Elsevier]

Abstract: The present contribution considers the dynamics of beaches occupied by outcropping/buried beachrocks, i.e. hard coastal formations consisting of beach material lithified by in situ precipitated carbonate cements. The dynamics of a Greek microtidal beach with beachrocks (Vatera, Lesbos) are examined through the collection and analysis of morphological and sedimentary field data, a 2-D nearshore hydrodynamic model and a specially constructed 1-D morphodynamic model. The results showed that the beachrock-occupied part of the beach is characterised by distinctive morphodynamics as: (i) its beachface is associated with large slopes; (ii) there is a good spatial correlation between the sub-aerial and shallow submerged mean beach profile and the buried/outcropping upper beachrock surface; and (iii) the seaward margins of the submerged beachrock outcrops are always associated with a ‘scour step’ i.e. a submerged cliff. The results also showed that beachrock outcrops can bias cross-shore sediment exchanges by impeding onshore transport due to the presence of the scour step. In this sense, beachrock outcrops may be considered as offshore transport ‘conduits’ for the beach sediments. A conceptual model of beach sediment transport, based on the field data and the hydrodynamic modelling is proposed. According to this model, fresh beach material from adjacent terrestrial sources is transported alongshore, towards the central part of the embayment, where a littoral transport convergence zone occurs under most wave conditions. There, the laterally supplied sediments are lost offshore. [Copyright &y& Elsevier]

Abstract: Landsat Enhanced Thematic Mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret geomorphological changes in the coastal zone between Kitchener drain and Damietta spit in the northeastern Nile delta previously recognized as a vulnerable zone to the effects of any sea-level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km2 to the agricultural deltaic land. About 48 km2 of sand dunes, marshes, sabkhas and salt pans have been converted to productive fish farms. The main urban centers have expanded, and new urban centers (Damietta harbor and the New Damietta city) have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As the consequence of human activities the size of Manzala lagoon has been reduced to less than 50%. Short-term shoreline changes along the coast of the study area established from beach profile survey, spanning the years of 1990 to 2000, reveal longshore patterns of erosion versus accretion. The rate of shoreline retreat has increased in the downdrift side of Damietta harbor (−14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwater system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures. [Copyright &y& Elsevier]

Abstract: Beach profile equilibrium is the principal concept assumed by most numerical modelling. The response of beach profile configuration to natural and anthropogenic changes could be predicted to help in selecting the most appropriate engineering design required to mitigate coastal erosion and accretion alongshore. Thus, in order to apply coastal engineering projects, the predicted profile of equilibrium should be close enough to the measured profile. Therefore, before application of numerical modelling techniques, equilibrium expressions have to be validated at the study site. This research aims to assess the validity of the equilibrium profile concept on the Nile Delta coast based on beach profiles surveyed in 1990 from the main promontories; Abu-Quir Bay, the Rosetta promontory and the El-Burullus promontory. The results indicate that the equilibrium beach profile is consistent with the measured profiles at the study sites beyond 200 m distance offshore at −4 m depth. In contrast, the equilibrium status is not valid along the beach face at −1 m depth. Accreted beaches at Abu-Quir bay and Burullus promontory are characterized by wide berms and gentle beach face whereas eroded stretches at Rosetta promontory have a narrow berm and steep beach faces. The measured profiles are also compared with the exponential beach profile concept. An exponential hypothesis is not valid along the Nile Delta coast. Profiles measured at Abu-Quir, Rosetta and El-Burullus depart significantly from the exponential equation. Despite the fact that equilibrium expression can describe beach profiles along the Nile Delta, one equilibrium profile equation is not sufficient to assess all beach profiles. This can be explained as the morphology of beach profiles is subjected to some factors including; sediment characteristics, wave parameters and closure depth, which vary alongshore. Analysis of the validity of the equilibrium beach profile is recommended to get accurate results in modelling simulations and design the most appropriate engineering projects required for shore protection. [Copyright &y& Elsevier]