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Houston, J.R., 2023. Measured fate of beach nourishment sand. Journal of Coastal Research, 39(3), 407–417. Charlotte (North Carolina), ISSN 0749-0208. The fate of sand placed over a 20-year period in one of the largest series of beach nourishment projects ever conducted in the United States is determined by using direct measurements of elevation vs. distance from dunes to closure depth. Four projects placed 11.25 million m3 of sand from 1998–2017 on a 28.8-km-long shoreline at Panama City on Florida's Gulf of Mexico coast. Profile measurements were available in 1996 following Hurricane Opal and in 2018 after Hurricane Michael, one of the largest hurricanes to strike the United States, which came ashore only 30 km from Panama City beaches. The profiles were about 300 m apart within the project template and extended down to closure depth. After about 20 years, 87 ± 3% of the nourishment sand remained on profiles. Some sand used for nourishment was dredged within closure depth along a 3.6-km section and resulted in sand loss of 4% ± 1% as sand partially refilled the dredged holes. About 9% ± 3% was lost to longshore transport out of the project area. Calculations based on the equilibrium profile concept used in U.S. beach nourishment design predicted beaches should have widened 30.9 m ± 0.9 m and profiles raised 0.69 m ± 0.10 m due to the measured volume of sand remaining on profiles from the start of beach nourishment in 1998 to November 2018 after Hurricane Michael. The measured change in beach width was 32.4 m ± 4.0 m, and the rise was 0.66 m ± 0.05 m. The rise of 0.66–0.69 m is comparable to the 0.81 m mean sea-level rise by the year 2100 projected by the Intergovernmental Panel on Climate Change for its worst-case temperature scenario. [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 study investigates the impact of beach sediment supply on dune volume evolution through data analysis and model simulations of the Kennemer dunes in the Netherlands. A cross-shore sediment transport model (the CS-model) is applied with local time-averaged longshore sediment transport gradients derived from bathymetric and topographic observations. The model is used to study the relative importance of different transport processes on dune volume evolution, assuming that aeolian transport from the beach to the dune is supply-limited. The wave-driven longshore transport gradients are found to explain a large part of the observed variation in the dune evolution within the study area. In accreting parts of the coast, dunes are growing due to sediment supply from longshore transport, whereas in eroding parts, dune growth depends on supply from artificial nourishments. Seasonal constructions on the beach and vegetation removal from the dunes partly impede dune growth along the considered stretch of coast. The model performance is satisfactory, being able to reproduce a considerable part of the large variation in the alongshore dune response observed in the study area. Overall, the results are a promising contribution to the capability of simulating decadal-scale dune evolution, which is important for long-term flood risk assessments and safe designs of nature-based solutions. • Decadal-scale dune volume evolution was successfully simulated with the CS-model. • Long-shore transport gradients and nourishments control dune evolution at this site. • Seasonal beach houses are found to partly impede dune growth. [ABSTRACT FROM AUTHOR]

Abstract A reduced-complexity numerical model, LX-Shore, is developed to simulate shoreline evolution along wave-dominated sandy coasts. The model can handle any sandy shoreline geometries (e.g. sand spits, islands), including non-erodible areas such as coastal defenses and headlands, and is coupled with a spectral wave model to cope with complex nearshore wave fields. Shoreline change is primarily driven by the gradients in total longshore sediment transport and by the cross-shore transport owing to variability in incident wave energy. Application to academic cases and a real coast highlights the potential of LX-Shore to simulate shoreline change on timescales from hours (storm) to decades with low computational cost. LX-Shore opens new perspectives in terms of knowledge on the primary mechanisms locally driving shoreline change and for ensemble-based simulations of future shoreline evolution. Highlights • A new shoreline change model is developed for wave-dominated sandy coasts: LX-Shore. • The numerical implementation allows addressing complex shoreline plan-view shapes. • LX-Shore couples cross-shore and alongshore processes. • LX-Shore simulates shoreline variability up to decades with low computational cost. • LX-Shore can provide new insights into the mechanisms controlling shoreline change. [ABSTRACT FROM AUTHOR]

ABSTRACT Messaros, R.C.; Rosati, J.D.; Buonaiuto, F.; Rasmussen, C.; Vega, A.M., and Bocamazo, L., 2018. Assessing the coastal resilience of Manasquan Inlet to Sea Bright, New Jersey: Regional sediment budget 1992–2003. Assessing the resilience of regional coastal systems requires analysis of the short- and long-term erosion and accretion characteristics of beach material, including natural and anthropogenic sources and sinks. A regional sediment budget provides that accounting and is pivotal to successful management practices that enhance the resilience of coastal systems. The U.S. Army Corps of Engineers, New York District, updated the regional sediment budget for Manasquan Inlet to Sea Bright, New Jersey, for 1992–2003, which reflects the effects of various beach replenishment projects. The study area is approximately 33.8 km long and encompasses two inlets, mainland beaches from Manasquan Inlet to Long Branch, and a barrier-spit landform from Long Branch to Sea Bright. The previous sediment budgets represented a relatively eroded and limited source beach condition. This updated sediment budget is the first to analyze the with-project condition incorporating periodic beach nourishments/renourishments. The shore protection project consisted of an initial fill of approximately 17 Mm3 (million cubic meters) between 1994 and 2002 and additional fill/renourishment of 11 Mm3 between 2008 and 2016. Data for the sediment budget were based on volumetric change of the beach as developed from digitized, historical, aerial shoreline images as well as volumes and location of sediment replenishment (nourishment) activities in this region of the shoreline. Results from this budget indicate a net longshore transport of sediment northward from Manasquan Inlet toward Sea Bright, increasing from 106,000 m3/y just north of Manasquan Inlet to 343,000 m3/y north of Monmouth Beach. This updated sediment budget establishes a good understanding of the beach processes over time, which will enhance the ability to provide better coastal management and resilience for the northern New Jersey shoreline. [ABSTRACT FROM AUTHOR]

The Pinetamare Marina, located SE of the mouth of the Volturno River and the Regi Lagni Canal (southern Italy), is interested by silting phenomena due to longshore transport of fluvial sediments. To eliminate this severe problem, the design of the new Marina includes the construction of a sediment trap, placed perpendicular to the breakwater, to prevent the accumulation of the sand sediments at the marina entrance. To study the efficiency of this solution, experiments were performed through a physical model in a wave basin, with appropriate scaling of the geometric characteristics and of the hydrodynamic processes. The experimental tests highlighted that the trap is able to intercept sediments and to mitigate the port silting for about two years, after which it is necessary to dredge the accumulated sand sediments. These sediments are used to compensate the erosion of the beaches downstream the breakwater. [ABSTRACT FROM AUTHOR]

As a part of the Dredging Operations and Environmental Research (DOER) Program, movable-bed physical model experiments were performed at the U.S. Army Engineer Research and Development Centre's (ERDC), Large-scale Sediment Transport Facility (LSTF) to investigate the fate and evaluate the benefits of nearshore-placed dredged material. The resulting bathymetry was measured with detailed surveys, the migration of the mound was quantified and comprehensive observations of hydrodynamics were obtained. The potential suitability of dredged material placement in the nearshore/surf zone was demonstrated after 10 h of oblique wave attacks. It has been shown that, as the mound was located at the edge of the surf zone, very likely wave breaking induced horizontal circulation may be dominant. A downdrift accretion of the submerged beach was observed, which is due to the transport of part of the sediment suspended by breakers at the mound and captured by the longshore currents. The experiments provided useful validation data for numerical morphological models. [ABSTRACT FROM AUTHOR]

Along many coastlines of the world, beaches provide the primary defence against flooding or erosion with their fate under rising sea levels still only poorly researched. This is particularly the case for the coastline of Southeast England, where ~190 km of shingle barriers protect low-lying hinterland or a coastal plain that is at or barely above the present reach of waves. During the Holocene transgression, these beaches moved into their present position through longshore extension and cross-shore roll back. This process stopped more than a century ago with port developments affecting longshore transport and the construction of groynes to hold the beach in place. This was followed by beach recharge and recycling towards the end of the 20 th century to build up and maintain beaches as coastal defences in their mid 19 th century position. This paper explores the design requirements for these beaches under future sea level rise scenarios of 1 to 5 m using recently developed tools. It shows that the presently still semi-natural beaches have to increase in size with crest height elevations having to rise by at least up to 1.26 times the rate of sea level rise and that due to higher longshore wave power, especially during storm conditions in the future, higher and stronger groynes are needed to hold these larger beaches in place. Future design requirements for beaches are sensitive to foreshore levels and orientation of the beach to the dominant waves with those presently characterised by shallow foreshores and oblique wave approach requiring the biggest adjustments. Required size increases will be difficult to implement due to the built-up nature of the hinterland. The engineering alternative would be to replace beaches with hard structures, a process that has already started where maintaining a beach is no longer economically viable or the residual risk associated with overwashing and an eventual tidal breach has become unacceptable. [ABSTRACT FROM AUTHOR]

Embayed beaches occurring along rocky coasts with headlands controlling hydrosedimentary processes are considered to be constrained sedimentary systems with little longshore sediment transfer between them. Such beaches are likely to narrow under rising sea level and a deficit of fluvial sediment, and because beaches act to dissipate wave energy, cliff erosion is expected to increase. Knowledge of hydrosedimentary processes in fetch-limited environments such as embayed beaches is therefore a fundamental management tool in erosion-prone coastal areas such as the Algarve region (southern Portugal). The main objective of this work is to quantify longshore sediment transport (LST) using a sedimentary tracer and compare the results with the ones derived via empirical formulae from several authors. To achieve this, we establish the spatial and temporal patterns of stained sediment, and relate these to marine climate data over six tidal cycles for three adjacent embayed beaches. The values of displaced sand estimated using tracer and scaled to mixed layer depth were compared with the results of five well-known LST formulae to assess the applicability of each model to mesotidal environments. Of the LST formulae used, the CERC (2013) shows to be the most accurate in our study area. This study demonstrates the efficacy of using tracers for tracking and quantifying the sediment transport and as a basis for assessing the viability of different LST formulae for representing transport in these types of environments. The work also shows the importance of the morphological control of hydrosedimentary processes, including the disruption of longshore drift and the sediment transfer promoted by shore platforms. [ABSTRACT FROM AUTHOR]

Wegner, C.E. and Ellis, J.T., 2017. The influence of sea-level rise on wave-energy dissipation and wave-driven currents at Buck Island Reef National Monument. Modern Caribbean reefs have undergone significant degradation in the past century because of various anthropogenic stressors, which include climate-change-related impacts, hurricanes, and, potentially, sea-level rise. Degraded reefs will be unable to maintain sufficient vertical accretion with substantial increases in sea level, which will alter the hydrodynamics of these systems. A reduction in wave dissipation by reefs has the potential to shift the shorelines behind the reefs, potentially resulting in economic and habitat losses for tropical shorelines. This study focused on a barrier reef with low, live coral cover (<10%) and accretion rates comparable to current rates of sea-level rise in the region (∼1.7 mm/y). Tides served as a proxy for sea-level rise, with the spring high tide representing a future low tide. These findings indicate that at low tide, infragravity wave frequencies (0.004-0.04 Hz) dominate in the lagoon and are a function of wave breaking on the reef. At high tide, the infragravity waves are less prominent. Current velocities were higher at high tide, averaging 0.14 m s−1 vs. 0.11 m s−1 at low tide. The spectral current characteristics correlate with the infragravity wave frequencies and suggest that these waves are a driving force in lagoon circulation. Wave-energy transmission increased at high tide by 20-30% throughout the sampling period. These results suggest that with sea-level rise, infragravity band waves will be reduced and affect the stresses on the sea bed and sediment-transport processes, also allowing larger and more energetic waves to reach the shoreline. [ABSTRACT FROM AUTHOR]

Low-energy, non-tidal lake beaches are known to be subject to longshore morphodynamics, but little is known about how they are driven by wind and wave-driven currents. Lake Markermeer is a shallow (∼ 4 m deep), wind-dominated lake, of approximately 700 km 2. A gradient in wind-induced water level set-up at the leeward shore induces a flow from the shallower to the deeper parts of the lake, thereby generating a large-scale, horizontal circulation. Flow measurements and results from a numerical Delft3D model of the lake show that these circulations impact the nearshore currents greatly, even more than wave-driven longshore currents for most wind conditions. From nearshore measurements at the first study site in lake Markermeer, we found a clear relation between longshore sediment transport capacity and the measured longshore volume flux. The model numerical can predict flow direction and magnitude for any wind condition. Using wind statistics, the net transport capacity for a short period or a long term mean can be predicted. The relation is confirmed for a second study site, which shows a distinct net transport capacity that could not be explained from wave-driven longshore flow alone. Concluding, large-scale lake circulations are of great significance for the morphological development of low-energy, non-tidal beaches in shallow, wind-driven water bodies. Knowledge of these circulations and their dependence on wind characteristics is a crucial factor to better understand and predict sediment losses of lake beaches. • In wind-dominated lakes, bathymetrical variance causes water level set-up gradients. • In shallow lakes, set-up gradients can induce large-scale, horizontal circulations. • Large-scale lake circulations affect longshore sediment transport on lake beaches. • Longshore sediment transport has a significant impact on design and maintenance. [ABSTRACT FROM AUTHOR]

In the present paper, a set of 319 field and laboratory data on longshore transport rate has been gathered, checked, and finally adopted in order to overcome a noticed limitation in the previous version of General Longshore Transport (GLT) procedure for the estimation of Longshore Transport (LT). In particular, the extensive number of additional data, characterized by a wide mobility range, has allowed to obtain a single equation able to determine the longshore transport rate at coastal slopes consisting of loose not-cohesive materials, from reshaping dynamically stable berm breakwaters to sandy beaches. The reliability of the GLT procedure has been assessed by an independent verification with 39 field and laboratory data, for both offshore and breaking wave characteristics as an input. In addition, the GLT procedure has been compared with the van Rijn (2014) formula. • Gathered high quality datasets of longshore transport from field and laboratory experiments. • Calculation of longshore transport rate at slopes consisting of loose not-cohesive materials. • GLT procedure for longshore transport at any coastal mound for both offshore and breaking wave characteristics as an input. • Improvement and verification of the General Longshore Transport procedure on an independent dataset. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess the longshore transport gradients and wave power distribution along the Ilha Comprida beach system and relate it to the distribution of the current erosion process along this barrier island. The study is based on quantitative analysis of the potential longshore drift and the wave power distribution, as well as on the morpho-sedimentary seasonal variations in the beach system. Therefore, the 30-year wave reanalysis database from the global wave generation model WAVEWATCH III (NOAA/NCEP) has been extracted and analyzed for the region, as well as field surveys with topographic measurements and sediment samples. The numerical model MIKE 21 SW has been applied to propagate waves onshore and recognize the longshore transport tendencies and the nearshore wave power distribution. Results show an overall transport trend to the NE, being larger in the southern sector than in the northern sector of the island. Varying transport magnitudes prove to generate gradients in longshore drift. Two positive gradients in the longshore drift, resulting in local sediment losses, are observed. One is found in the central-southern area and another in the northern part of the island. Both areas coincide with erosive spots, as observed through field surveys. The central-southern positive gradient becomes larger and migrates to the south during the most energetic months, while the northern gradient presents only variations in magnitude, being relatively stable in position throughout the year. Nearshore wave power results show two main areas with higher values that coincide with the positive longshore transport gradients. Sediment data presents low temporal variability, although spatial variations have been found reflecting the local hydrodynamic conditions, while the volumetric data shows largest values in the central-northern sector, being smaller in the central-southern and northern regions. Moreover, the central portions are more stable than the extreme portions regarding its seasonal variability. Our findings show that along this wide open stretch of coastline, exposed to the same offshore wave regime, an alternated nearshore wave regime results in areas with hydrodynamic conditions which lead to erosion or accretion. Erosion is caused by negative sediment balance as a function of higher wave power and positive gradients in longshore transport, and accretion due to lower wave power and negative gradients in longshore transport. Our findings help in further understanding the island's long-term evolution and current state of its beaches. [ABSTRACT FROM AUTHOR]

Shoreline erosion is often exacerbated by reduction of sediment inputs because of interference with sediment transport by human structures. We evaluate use of sediment dredged from a navigation channel to establish a feeder beach adjacent to a bulkhead as a solution for addressing erosion of landforms and habitats on sandy estuarine shores. The objectives are to determine how beach volume, position and shape within and downdrift of the fill area change and whether the volumes supplied by dredging match sediment losses caused by human actions. The fill was placed along a 75 m length of shoreline adjacent to a marina in Great South Bay at Fire Island, New York, USA. Changes in beach shape and volume were determined from topographic surveys conducted before and after fill and at half year intervals for 18 months. The quantity of fill was 1747 m 3 . Maximum shoreline advance due to fill emplacement was 20.7 m. The maximum volume placed at any transect was 28.6 m 3 m − 1 of shoreline length. Erosion of the fill occurred rapidly, with landward migration of a conspicuous scarp. The edge of the upland 18 months after the fill was placed was up to 4.6 m farther landward than prior to the fill. Movement of sediment alongshore downdrift of the fill occurred as wave-like pulses, extending the active foreshore bayward, causing accretion of the inner low tide terrace, burying saltmarsh peat outcrops on the foreshore and creating a higher and wider overwash platform over portions of the saltmarshes. Landforms downdrift of the fill area underwent successive stages including erosion (pre-nourishment), accretion, stability (with throughput of sediment) and then erosion. Beach nourishment compensates for human-induced sediment losses. The volume of sediment added from maintenance dredging can slow the rate of erosion but may not prevent long-term shoreline retreat. Restoration and maintenance of coastal landforms and habitats to specific target states at a given location is difficult, but augmenting longshore sediment inputs can allow those locations to undergo cycles of erosion and accretion, creating a variety of landforms and habitats where only erosional forms existed previously. Alternatively, nourishment could occur more frequently and in smaller volumes to reduce fluctuations in accretion-erosion cycles. [ABSTRACT FROM AUTHOR]

Sand nourishments are a widely applied technique to increase beach width for recreation or coastal safety. As the size of these nourishments increases, new questions arise on the adaptation of the coastal system after such large unnatural shapes have been implemented. This paper presents the initial morphological evolution after implementation of a mega-nourishment project at the Dutch coast intended to feed the surrounding beaches. In total 21.5 million m 3 dredged material was used for two shoreface nourishments and a large sandy peninsula. The Sand Engine peninsula, a highly concentrated nourishment of 17 million m 3 of sand in the shape of a sandy hook and protruding 1 km from shore, was measured intensively on a monthly scale in the first 18 months after completion. We examine the rapid bathymetric evolution with concurrent offshore wave forcing to investigate the feeding behaviour of the nourishment to the adjacent coast. Our observations show a large shoreline retreat of O (150 m) along the outer perimeter of the peninsula, with locally up to 300 m retreat. The majority (72%) of the volumetric losses in sediment on the peninsula (1.8 million m 3 ) were compensated by accretion on adjacent coastal sections and dunes, confirming the feeding property of the mega nourishment. Further analyses show that the morphological changes were most pronounced in the first 6 months while the planform curvature reduced and the surf zone slope flattened to pre-nourishment values. In the following 12 months the changes were more moderate. Overall, the feeding property was strongly correlated to incident wave forcing, such that months with high incoming waves resulted in more alongshore spreading. Months with small wave heights resulted in minimal change in sediment distribution alongshore and mostly cross-shore movement of sediment. [ABSTRACT FROM AUTHOR]

Medellín, G.; Mariño-Tapia, I., and Euán-Ávila, J., 2015. The influence of a seawall on postnourishment evolution in a sea-breeze-dominated microtidal beach. The postnourishment beach evolution is evaluated on a sea-breeze-dominated microtidal beach in Yucatan (Mexico). The study area has experienced severe beach erosion due to both alongshore sediment-transport gradients during calm conditions and offshore sediment transport during extreme wave events. Therefore, a shoreline restoration program, including beach nourishment and the removal of groynes, was carried out in 2002. Bimonthly subaerial/intertidal beach profiles measured during 7 years (2002-09), in front of a seawall and at an adjacent beach (nonwalled), are employed to analyze the beach nourishment evolution. Empirical orthogonal function (EOF) analysis of the shoreline time series is performed using the data extracted from the 50 field surveys. The temporal evolution of the EOF analysis shows the following: (1) an abrupt increase in beach width due to nourishment at the study site at the beginning of 2003, (2) followed by a sustained increase (from 2004 to 2007) owing to the sediment advection from a massive beach fill performed up-drift of the study area, and (3) a decrease in beach width from 2007 until the end of the study period. Moreover, the mean profile-volume change is estimated separately for walled and nonwalled beach sections. The nonwalled profiles results are consistent with the temporal evolution described by the EOF analysis. On the other hand, walled beach profiles show a net volume loss from 2002 to 2007, remaining stable during the following 3 years. Consistent with previous studies, seasonal variability of sand volume was found to be greater in front of the seawall with respect to the nonwalled section. Nevertheless, the erosional/despositional rates in the two sections show opposite trends during mean (sea-breeze) wave conditions, being more important in the subaerial beach profiles. The latter implies that swash-zone sediment transport represents an important contribution to the total sediment budget in the study area; hence, seawalls can significantly modify coastal dynamics in sea-breeze-dominated environments. [ABSTRACT FROM AUTHOR]

The General Longshore Transport (GLT) model (Tomasicchio et al., 2013) and the Van Rijn (2014) expression represent the only two available general formulae in literature for the estimation of longshore transport (LT) at sand, gravel and shingle beaches. The GLT model is based on an energy flux approach combined with an empirical relationship between the wave induced forcing and the number of moving elements. An independent verification of the GLT model is performed for the estimation of the total (bulk) LT at shingle beaches. Without any further calibration, the suitability of the GLT model, even for the shingles beach case, is assessed by means of the comparison between the LT predictions and the observations from two field data sets (Chadwick, 1989; Nicholls and Wright, 1991). In most cases the GLT predicts LT rates within a factor of 2 of the observed values. The predictive capability of the GLT model is tested with reference to two different formulae recently proposed in literature (Mil-Homens et al., 2013; Van Rijn, 2014). It is shown that the GLT model gives a better agreement with the observations (Chadwick, 1989; Nicholls and Wright, 1991; Van Hijum and Pilarczyk, 1982) with respect to the other considered formulae. Moreover, long term (annual) field data (Van Wellen et al., 2000) have been used for a further verification. In addition, the GLT model confirms to have a better agreement even for the LT at dynamically stable berm reshaping breakwaters (Lamberti and Tomasicchio, 1997; Van der Meer and Veldman, 1992). [ABSTRACT FROM AUTHOR]

Abstract: Longshore transport of sand, gravel and shingle has been studied using field and laboratory data over a wide range of conditions. A detailed model (CROSMOR) for cross-shore and longshore sediment transport has been used to determine the effects of wave period, grain size, beach/surf zone slope and type of waves (wind waves or swell waves). The longshore transport was found to be proportional to wave height to the power 3.1 (≈H3.1), to grain size to the power −0.6 (≈d50 −0.6) and to beach slope to the power 0.4 (≈tanβ0.4). Regular swell waves yield much larger (factor 1.5) longshore transport rates than irregular wind waves of the same height. It is proposed to take this effect into account by a swell correction factor. Based on all results, a new simple and general (dimensionally correct) expression for longshore transport of sand, gravel and shingle beaches with grain sizes between 0.1 and 100mm has been derived. Short-term and long-term field data of sand, gravel and shingle have been used for verification. In most cases the predicted longshore transport rates are within a factor of 2 of the measured values. The CERC and Kamphuis formulas have also been tested. [Copyright &y& Elsevier]

This study aims to characterize the wave climate near the coastal region of Maputo (Mozambique), and to provide a first assessment of the sediment transport load in this area. A time-series of 13 years' worth of offshore wave data, obtained from reanalysis products, was propagated to the coast. Wave propagation was performed using Linear Wave theory and the numerical model, Simulating WAves Nearshore (SWAN). Propagations with SWAN were carried out considering different scenarios in order to evaluate the influence of parameters such as wind, tidal level, frequency spectrum and numerical mesh resolution on wave characteristics along the coast. The prevalent waves propagated came from between east and southwest directions. Results from linear propagation were used to estimate the potential longshore sediment transport. The Coastal Engineering Research Center formula was applied for a stretch of beach in the Machangulo Peninsula. A net potential rate of longitudinal sediment transport (of the order of 105 m3/year, along an extension of the coast of 21 km) was directed northwards, and was consistent with the frequent wave directions. [ABSTRACT FROM AUTHOR]

Healy, T. and de Lange, W., 2014. Reliability of geomorphic indicators of littoral drift: Examples from the Bay of Plenty, New Zealand. The net direction of littoral drift can be evaluated by multiple lines of evidence, including a range of geomorphic indicators and trends in sediment characteristics. In this article, the processes that influence the longshore transport of sediment are reviewed and assessed by the types of geomorphic indicators and sediment trends that can be expected. Various proxies for measured littoral drift are used to evaluate the littoral drift in the Bay of Plenty, New Zealand. Previous studies, utilising geomorphic indicators and, to a lesser extent, sediment characteristics and simple models of longshore sediment transport, developed a conceptual model of two main littoral drift systems starting at the western and eastern margins of the Bay of Plenty and converging in the vicinity of Ohiwa Harbour, an estuary enclosed by two opposing spits within the bay. Comparison of geomorphic indicators of littoral drift with the results of 30 years of monitoring and investigation demonstrate that geomorphic indicators can be misleading or misinterpreted. Overall, they do not appear to have been reliable for the Bay of Plenty, whereas sediment characteristics have performed better. The published rates of net littoral drift, and also the directions, appear to be too high and are inconsistent with observed patterns of erosion and accretion. Further, the exchange of sediment between the beach and the inner shelf has not been considered. Within the Bay of Plenty the net littoral drift magnitude and direction varies in response to changes in the wave climate associated with climatic variability, particularly the magnitude, frequency, and duration of the La Niña and El Niño extremes of the El Niño-Southern Oscillation. Decadal-scale fluctuations in the patterns of erosion and accretion along the Bay of Plenty coast have also been recognised. Finally, the influence of tectonic effects on geomorphic indicators of littoral drift needs further investigation. [ABSTRACT FROM AUTHOR]

Shoreline evolution due to longshore sediment transport is one of the most important problems in coastal engineering and management. This paper describes a method to predict the probability distributions of long-term shoreline positions in which the evolution process is based on the standard one-line model recast into a stochastic differential equation. The time-dependent and spatially varying probability density function of the shoreline position leads to a Fokker-Planck equation model. The behaviour of the model is evaluated by applying it to two simple shoreline configurations: a single long jetty perpendicular to a straight shoreline and a rectangular beach nourishment case. The sensitivity of the model predictions to variations in the wave climate parameters is shown. The results indicate that the proposed model is robust and computationally efficient compared with the conventional Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The development of coastal adaptation pathways along sandy barrier-island coasts requires an understanding of multi-decadal barrier morphodynamics in response to forcings such as sea-level rise, sediment fluxes, and storminess. Long- and cross-shore sand exchanges among barrier-system compartments (shorefaces, beaches, dunes, tidal inlets, backbarrier lagoons) and between adjacent barrier islands can play a fundamental role in barrier-system morphology and resilience to sea-level rise. We explore these dynamics through investigation of historical areal changes within the 13 largely undeveloped Virginia Barrier Islands of the United States Mid-Atlantic Coast. We pair subaerial island areas mapped from historical surveys and modern aerial and satellite imagery with representative island thicknesses determined from stratigraphic and lidar-derived elevation data to estimate volumetric changes through time. Overall, the Virginia Barrier Islands lost ~3.4% (16 × 106 m3) of their 1887 C.E. volume between 1887 and 2017 C.E. The loss from three central islands (Parramore, Hog, and Cobb)—historically characterized by rotational behavior—was 43% (79 × 106 m3). In particular, Parramore Island continuously decreased in volume over the 20th and 21st centuries. In contrast, growth of Assateague and northern Wallops islands (located at the northern, updrift end of the island chain) from 1887 to 2017 C.E. resulted in a volume increase of ~59 × 106 m3. Whereas the Virginia Barrier Islands as a whole modestly decreased in size (and thus volume) directly in response to storm impacts and accelerating relative sea-level rise since the mid-1800s, the differential behavior of islands south of Assateague suggests more regional controls on coastal geomorphic behavior. Specifically, we identify the roles of antecedent substrate, sand trapping and changing wave-refraction patterns associated with the growth of Assateague Island, and inter-island sand exchanges in response to changing updrift barrier-scale behaviors. These findings help to better understand the underlying mechanisms behind state changes of barrier islands; in particular, the mechanisms by which geomorphic change along one barrier island influences those located several to tens of kilometers downdrift. This highlights the need to consider coastal beach and sand management over long reaches, even in systems which are largely unaffected by development, nourishment, and shoreline hardening. [ABSTRACT FROM AUTHOR]

Coastal erosion is widespread across the Bight of Benin owing to the perturbation of the sediment transport by the installation of the major ports of Lomé (Togo), Cotonou (Benin), and Lagos (Nigeria), among other factors. While different coastal management measures have been put in place to mitigate the effects of this hazard, they have seldom lessened the damage caused by it. To this end, this study examined the coastal processes in Southwest Nigeria (Barrier-Lagoon and Mud coast sections) through the numerical modelling of the hydrodynamic, spectral-wave, and sediment transport for three months to apprehend the poor performance of the management measures. Model results reveal that the nearshore current is mainly directed eastward with the persistent exposure of the area to wave-action. Two major sediment transports; the eastward/south-eastward and westward/north-westward sediment transports, were also identified. The predominance of these sediment transport patterns implies that the continuous adoption of reactive, site-specific hard-engineering coastal management approaches will give counter-productive results. Thus, to sustainably manage the coastal erosion problem across the Bight of Benin, there is the need to adopt a long-term, regional perspective with a cascade of coastal management measures covering all areas under the influence of the predominant sediment transports. • We investigated the incessant failures of coastal erosion management measures. • This was carried out through the numerical simulation of sediment transport. • Sediment load across the study area mainly moves towards the east. • The sediment load characteristics and preference for hard coastal measures is a challenge. • This has great implications for sustainable management of coastal erosion. [ABSTRACT FROM AUTHOR]

The sensitivity of a one-line longshore shoreline change model to the incident wave direction is evaluated at Narrabeen Beach (Australia). As previously observed, the application of the one-line model using wave conditions generated along the 10-m depth contour produces a long-term reorientation of the coastline, with an initial transition period and then a new stable equilibrium during the 10-year period from 2005 to 2015. However, this coastline change in shoreline planform shape is not observed in the shoreline position measurements. The source of this error is investigated by assuming that it is caused by biases in the incident wave direction and by using a Monte Carlo approach to search for the optimal set of wave angle bias corrections to apply at each cross-shore transect. The obtained optimal values enable the one-line model to reproduce accurately the shoreline planform, and they are coherent with estimates of the wave breaking angle obtained independently using a nearshore wave propagation model. Then, using the corrected wave angle time series as a reference, a second Monte Carlo analysis is completed to investigate the sensitivity of the model to errors in the mean wave direction drawn from Gaussian distributions with varying standard deviations. The analysis shows the range of expected errors in shoreline position for an estimated range of errors in the mean wave direction at Narrabeen beach. This work highlights the importance of considering the sensitivity of one-line longshore model simulations to errors in the incident wave angle, which can be relatively large given the uncertainties in spectral wave model estimates of wave direction, in wave buoy observations, and in wave propagation methods or input bathymetry used to estimate wave breaking conditions. • One-line shoreline change models often produce artifacts in beach planform. • One-line longshore models are highly sensitive to small incident wave angle biases. • Wave angle bias corrections can be obtained using a Monte Carlo approach. • Accurate observations or simulations of wave breaking conditions are necessary. [ABSTRACT FROM AUTHOR]

Thirty years of monitoring surveys and shoreline erosion studies (1980-2010) along the South Carolina coast show that artificial beach nourishment and the natural process of inlet shoal bypassing have advanced the shoreline along most of the developed beaches and barrier islands. Of the ~98 mi (~161 km) of developed beaches (including public parks), fully 80% were much healthier in 2010 than in 1980, as evidenced by burial of seawalls, wider berms, and higher dunes. About 15% of the developed beaches are in approximately the same condition as in 1980; the remaining ~5% are considered in worse condition. The balance of South Carolina beaches (~89 mi, ~146 km) are principally wilderness areas with limited public access. The dominant condition of wilderness beaches is high erosion; limited new sand inputs, particularly via inlet bypassing; and accelerated recession as many of these sand-starved beaches wash over salt-marsh deposits. High erosion results from a combination of sand losses to the lagoon, winnowing of muddy marsh deposits outcropping across the receding beach, and longshore transport losses to the adjacent inlet. An estimated 75% of the undeveloped beaches in 2010 were well landward of their 1980 positions. Between 1980 and 2010, -39.4 million yd³ (~30.1 million m³) of beach nourishment from external sources was added to developed and park beaches (~62.6 mi, ~102.6 km). This is equivalent to an addition of ~168 ft (~51 m) of beach width in the nourished areas. Natural shoal bypassing events appear to have added a similar magnitude of new sand along accreting beaches. Bypassing events at some beaches involved -2~5 million yd³ (1.5-3.8 million m³). Ebb dominance at many South Carolina inlets is shown to play an important role in preserving the littoral sand budget, maintaining large sand reservoirs for bypassing and helping maintain the developed beaches in the state. Low rates of erosion in other areas, such as the Grand Strand, combined with large-scale nourishment have advanced those beaches well beyond historic conditions. [ABSTRACT FROM AUTHOR]

Large-scale construction of tourist infrastructure on beaches around the world is consistently linked to unwanted morphological changes that lead to coastal erosion. Dune destruction, alteration of sediment sources, and the rigidisation of the coastal system are known to be the main causes of erosive behaviour on many tourist beaches. To plan sound shoreline management strategies, detailed understanding of the sediment transport processes is necessary. The present contribution focuses on the main sediment transport processes that take place at Cancun, Mexico, a large (12 km) and highly developed tourist beach. High-resolution quarterly beach profile monitoring from September 2007 to June 2009 is used to calculate volumetric changes that are reasonably well explained by the spatial patterns of modelled sediment transport potential. This parameter was calculated using the wave propagation model WAPO of Universidad Nacional Autonoma de Mexico, which explicitly solves diffraction and reflection processes that are particularly important in systems with pronounced rocky headlands, such as the northern and southern ends of Cancun beach. Results show a dominance of northward longshore transport in most of the system, and an important transport divergence with consistent southward transport at the southern end. Cross-shore transport seems to dominate the middle-north section of the beach. This behaviour is consistent with recent advances in the understanding of wave circulation in embayed beaches. The method used here is considered a good approximation of sediment transport patterns when local (surf zone) morpho- and hydrodynamic data are absent or difficult to acquire. [ABSTRACT FROM AUTHOR]

The hydrodynamic and morphodynamic parameters of a region in southern Brazil were determined by collecting sediments with stream traps (bedload and suspended load) in the surfzone and capturing images, studying topography, and researching sedimentology with the help of a movie camera, a total station, and laboratory work. Data on deep-water waves were garnered with a CPTEC/INPE model. Field work was carried out in 50 field trips during a 1-year period; 42 out of 50 trips focused exclusively on hydrodynamic and morphodynamic data, whereas eight of the trips were also used for collecting sediments. In addition, data on wind direction and velocity and on the longshore currents were also collected. All data were obtained in normal atmospheric conditions. Field work was carried out in six cross-shore profiles along Cassino Beach and Mar Grosso Beach (three profiles on each side of the estuary of Patos Lagoon). [ABSTRACT FROM AUTHOR]

Abstract: In the present paper a general longshore transport (LT) model is proposed after a re-calibration of the model originally introduced by Lamberti and Tomasicchio (1997) based on a modified stability number, N s ⁎⁎, for stone mobility at reshaping or berm breakwaters. N s ⁎⁎ resembles the traditional stability number (Ahrens, 1987; van der Meer, 1988) taking into account the effects of a non-Rayleighian wave height distribution at shallow water (Klopman and Stive, 1989), wave steepness, wave obliquity, and nominal diameter of the units. Nine high-quality data sets from field and laboratory experiments have been considered to extend the validity of the original model for a wider mobility range of the units: from stones to sands. The predictive capability of the proposed model has been verified against the most popular formulae in literature for the LT estimation of not cohesive units at a coastal body. The comparison showed that the model gives a better agreement with the physical data with respect to the other investigated formulae. The proposed transport model presents a main advantage with respect to other formulae: it can represent an engineering tool suitable for a large range of conditions, from sandy beaches till reshaping breakwaters. [Copyright &y& Elsevier]

Abstract: Subtle changes in the directional wave climate driven by changes in large scale climate variability have the potential to result in spatial changes (erosion and accretion) of sandy coastlines due to deviations in longshore sediment transport supply. 50+ years of hindcast offshore directional wave conditions for southeast Queensland, Australia were used to derive yearly wave climates that were input into a spectral wave model to estimate nearshore breaking wave conditions and resulting longshore sediment transport along a 35km stretch of sandy coastline. Resulting temporal deviations in net annual longshore transport were smoothed using a 5-year Hamming filter and compared against two climate indices known to influence the Australian climate: the Southern Oscillation Index (SOI) and the Inter-decadal Pacific Oscillation (IPO). During the negative IPO phase (more El Niño like) deviations in estimated transport were significantly correlated to the SOI index at −1 year lag and correlated to the IPO index at +1 year lag. During positive phases of the IPO (more La Niña like) highest correlations were found at 6 year lag (SOI) and −10 year lag (IPO). A linear regression model combining the influence of both indices explained 65% of the predicted variability in longshore transport during negative phases of the IPO and 48% of the variance during positive phases of the IPO. During positive phases of the IPO, the SOI index was shown to dominate model response and may indicate an increase in the influence of the South Pacific Convergence Zone with respect to the wave climate off the east coast of Australia. A model spanning both phases and only considering positive lags (knowledge of past climate indices) explained approximately half of the predicted variability in longshore transport over the entire record length. The results presented here indicate strong links between these large scale climate indices and estimated longshore transport ), such that a simple model derived from knowledge of these indices could be used as a first pass estimate of spatial and temporal variability in longshore sediment transport and resulting large scale coastal evolution. [Copyright &y& Elsevier]

Numerically estimated wave properties and the associated closure depth along the eastern Baltic Sea coast from the Sambian (Samland) Peninsula up to Pärnu Bay in the Gulf of Riga are compared against the existing data about accumulation and erosion. Typical values of the closure depth are about 5-6 m (maximum 6.58 m) at the open Baltic Sea coast, 3--4 m in the Gulf of Riga and 2--2.5 m in semi-sheltered smaller bays. The areas of intense accumulation or erosion (especially the areas of their high variability) generally coincide with the sections, hosting high wave intensity, except for a few locations, dominated by anthropogenic impact. It is shown that the longshore variations in wave intensity (or closure depth) can be used to identify the location of major accumulation and erosion domains. The sections that host the largest change in the wave height along the coast reveal erosion or accumulation features, depending on the predominant wave approach direction. [ABSTRACT FROM AUTHOR]

Abstract: Few large-scale field measurements of longshore sediment transport have been undertaken on beaches composed of coarse sediments, in part owing to difficulties associated with measurement in energetic swash zones in which large clasts are moving. Here we present results from a field experiment in which Passive Integrated Transponder tags were used to investigate patterns of cobble transport over 8months on a mixed sand and gravel beach on the east coast of New Zealand. The study objectives were to document rates of alongshore transport, and measure rates of cobble abrasion under field conditions. Cobble recovery rates were highly variable over the study period with 30–60% recovery at site 1 compared to much lower (0–20%) recovery rates at sites 2 and 3. Consistent uni-directional patterns of net alongshore sediment transport were observed. The median cobble transport rate was approximately 500m over 207days, indicating long-term net northward transport rates on the order of 2–2.5m/day. Results highlight a number of factors, in addition to longshore energy flux, that are important for understanding the observed patterns. In particular, across-shore sediment transport during storms may have been smaller at site 1 than the other sites owing to lesser wave exposure. This is partly responsible for higher cobble recovery rates at this site and also an increased amount of time during which cobbles were able to be transported alongshore on the lower beachface. Unique to this study, results demonstrate the use of PIT tags to provide direct measurement of cobble abrasion under natural processes. Repeat weight measurement on individually tracked cobbles show that after 207days the median loss was 11.3g, or 1.8% of total weight. There was a general trend of abrasion increasing with net transport distance, but longshore cobble movement was highly variable ranging from 130 to 2500m. [Copyright &y& Elsevier]

This study examines changes in shoreline change trends at Grand Isle, Louisiana, in relation to the implementation of a detached breakwater field completed in 1999. Eight sets of aerial photographs and digital ortho photo quarter quadrangle mosaics ranging from 1973 to 2004 were analyzed to establish pre- and postconstruction shoreline trends. Preconstruction, the island experienced persistent growth at its downdrift end. Postconstruction, this accretion ceased, and the downdrift end of the island began to experience erosion. The area landward of the breakwater field was accretionary before construction and became stable, whereas accretion increased in the area immediately updrift of the breakwater field. Two key design parameters, breakwater length and distance from the shoreline, were used to assessthe potential for the formation of salients. Results from an engineering model suggest that the breakwaters were constructed too far offshore for this typical response to occur. Nonetheless, results of the air photo analysis indicate a marked change in shoreline migration trends following construction of the breakwater field. [ABSTRACT FROM AUTHOR]

Fire Island, New York, is a 50-kilometer-long barrier island that has remained positionally stable without any formation of breach inlets for nearly 200 years. Some researchers have attributed its stability to a major supply of sand moving onshore from relatively deep water (i.e., >10 m depths). Others have demonstrated via sediment budgets that the principal sand sources at decadal to century time scales are littoral sediments derived from eroding beaches, bluffs, and cannibalization of inlet shoals in shallower depths (i.e., ⩽10 m). Published sediment budgets indicate that the quantity in question is of the order 105 m3/yr. The possibility that this deep-water source of sand is significant, active, and persistent at decadal to century time scales has led to reluctance to mine deep-water shoals for beach nourishment of Fire Island. Herein, the authors review five factors related to the potential for a significant deep-water sand source in this setting: (1) spatial and temporal frames of reference necessary for this flux of sand; (2) studies of scour and sediment transport over offshore features; (3) sediment size distribution across the foreshore; (4) depth of closure (DOC); and (5) contribution of abandoned inlet shoals. The authors conclude that evidence for an onshore flux of sediment (i.e., order of 105 m3/yr) is lacking and suggest that reluctance to mine the offshore for beach nourishment is unfounded. [ABSTRACT FROM AUTHOR]

Abstract: The application of an integrated data analysis and modeling scheme reveals that decadal-scale shoreline evolution along a U.S. Pacific Northwest littoral cell is highly dependent on both sediment supply and wave climate variability. In particular, accurate estimates of (Columbia River) sediment supply and sediment feeding from the lower shoreface are critical components of balancing the barrier beach sediment budget and are therefore essential to making sensible shoreline change hindcasts and forecasts. A simple deterministic one-line shoreline change model, applied in a quasi-probabilistic manner, enables evaluation of the influence of sediment supply and wave climate variability through simulation of historical shoreline change. Through iteration, a range of realistic scenarios are developed to constrain decadal-scale shoreline change predictions. Modeled shoreline changes are significantly sensitive to directional changes in the incident waves, and therefore sensitive to the occurrence of interannual climatic fluctuations such as major El Niño events. A predicted increase in the intensity of the east Pacific wave climate (1.0m increase in significant wave height in 20yr) affects forecast shoreline positions only when this increase occurs during the winter storm season. However, the effect of this increase in storm power during any given year is small relative to the impact of major El Niño events. The model has significant skill in decadal-scale hindcasts suggesting that alongshore gradients in sediment transport dominate coastal change at this scale at this site. However, both data and model results suggest that net onshore feeding from the lower shoreface is responsible for approximately 20% of the decadal-scale coastal change. Field measurements and poor model skill at annual scale indicate that cross-shore processes likely dominate coastal change at shorter time scales. [Copyright &y& Elsevier]

Abstract: Blooms of Dinophysis spp. associated with lipophilic shellfish toxin outbreaks are common in Northwestern Iberia waters from spring to autumn. Blooms of Dinophysis acuta are very seasonal (late summer-early autumn); they start earlier in Northern Portuguese waters during the upwelling season, and reach their maximum values in the Galician Rías during downwelling events at the end of the upwelling season. There is controversy about whether sudden increases in cell concentrations in the rías result from cross-shelf transport of populations previously established in adjacent shelf waters, or are due to longshore transport that brings populations located off Portugal to the North. In 2005, record concentrations of D. acuta were observed in Portuguese waters (14×104 cellL−1) off Aveiro in early September, while concentrations off the Galician coast were very moderate (102–103 cellL−1). During the autumn transition from upwelling- to downwelling-favourable winds, D. acuta declined abruptly off Portugal while the annual maximum (up to 22×103 cellL−1) was found in the Galician Rías. A new approach was used that combined physical observations (SST, current measurements); weekly observations from monitoring programmes in Galicia and Portugal; weekly division rate (μ min ) estimates of D. acuta in Ría de Vigo, together with monthly transects and additional ad hoc sampling in the Ría. During August and early September, division rates were high in Ría de Vigo but concentrations were low, whereas higher SST values in Portugal (a proxy for thermal stratification) seemed to promote the build up of high densities of D. acuta. During the last week of October and the first week of November, populations declined, whereas in Galicia, maximum concentrations were reached while division rate estimates were almost zero. Results presented here confirm that increased numbers in the Galician Rías are not due to intrinsic growth but to physically driven accumulation; a simple cell concentration budget calculated during the accumulation period suggests that the high net growth observed during downwelling, in the absence of cellular division, must be due to cells imported by longshore transport. [Copyright &y& Elsevier]

Abstract: The shape, dimensions and growth rate of an accumulating sandy spit is investigated by a theoretical and experimental study. The idealised case of a spit growing without change of form under a constant wave forcing is considered. The longshore wave-driven sediment transport is taken to be dominant in the formation of the spit. The shape of the spit is first described by an analytical one-line model for the coastline development and by a simple littoral drift model. The analytical model is valid for a spit with so large dimensions, that quasi-uniform conditions can be applied. It is found that with this assumption the dimensions of the spit cannot be determined. The width and shape of a finite spit is therefore determined from simulations with an area model for the wave-driven current and sediment transport along the spit. In this case the curvature effects from the spit on the longshore sediment transport (inertia of the longshore current, wave focussing) are includes. Several solutions for a uniformly growing spit may exist, and it is assumed that the fastest growing spit is the one to emerge. The simulations indicate the width of the spit to be proportional to the width of the surf zone. In experiments conducted in a wave tank an accumulating spit was formed at the down-drift end of a uniform stretch of coast exposed to waves approaching at an angle. The spit approached equilibrium dimensions when a constant wave climate was applied. The radius of curvature of the spit varied according to the height of the incoming waves. [Copyright &y& Elsevier]

Abstract: This study investigates the annual and inter-annual longshore transport at a high-energy dissipative beach (St. Trojan, SW Oléron Island, France), over the period 1997–2006. This study is divided in two parts: (1) a short-term study, based on field measurements carried out during, low, moderate and high-energy swell conditions, and permitting to calibrate a wave propagation model and both empirical longshore sediment transport formulas and a hydro-sedimentary numerical model; and (2) a long-term study, combining global optimization methods using WAVEWATCH III (WW3) model outputs and wave numerical modelling to define the nearshore wave climate and then to compute the annual and inter-annual longshore transport. A good agreement between the different methods was obtained and values for the annual longshore transport ranged from about 50,000±20,000m3/yr to 140,000±30,000m3/yr. The net annual longshore transport displayed an inter-annual variability, whereas values were always 3–10 times less than those proposed in previous studies. Such differences point out the necessity of calibrating empirical transport formulas and computing accurately the nearshore wave climate. The relatively low values for the net annual longshore transport were explained by a weak contribution of the most energetic swells, which systematically approach the shore with a frontal obliquity and also generate episodes of reverse transport. The methodology itself was also discussed, pointing out the limitations of this study but also the advantages of using WW3 data and simplified wave climates. [Copyright &y& Elsevier]

Deep-water sands form a new frontier for marine geology and petroleum exploration, but how does sand reach the deep sea? Existing geological models predict that deep-water sands are mainly supplied from rivers during times of low sea level, or by incision of canyons into the shelf to tap river or longshore-transport sand sources. Here, we demonstrate that at high sea level, southeast Australian deep-water sands are delivered by a wave-driven coastal transport system, interacting with estuarine ebb tidal flows, that transports sand over the shelf edge at a change in margin orientation. Discovery of this new process results from an investigation that combines multibeam acoustic, microfaunal, zircon and luminescence dating, oceanographic, Landsat, remotely operated vehicle, and sediment property methods. Our longshore transport-driven model is capable of forecasting new locations for deep-water sand deposits in a predictive paleoclimatic and paleotectonic setting. [ABSTRACT FROM AUTHOR]

Abstract: The morphology, hydrodynamics and sediment transport processes of a multi-barred macrotidal beach were surveyed over 21 semi-diurnal tides, the first eight of which were dominated by storm conditions with offshore wave heights ranging from 1.2 to nearly 3.5 m. The hydrodynamic conditions prevailing over the intertidal beach showed a rapid response to these storm conditions, notably through strong longshore currents that attained peak velocities of 1.6 m s−1, i.e. over three times the peak spring tide velocities of tide-generated longshore currents during calm conditions. The bars showed no cross-shore migration during the storm events. Morphological mapping of the beach, tracer dispersal patterns, and calculations of potential sand transport rates using the energetics-based model of Bailard [Bailard, J.A., 1981. An energetics total load sediment transport model for a plane sloping beach. J. Geophys. Res., 86, 10938–10954.] showed significant longshore sand transport, as well as longshore migration of an intertidal drainage channel. These longshore movements were bi-directional, responded to changes in incident wind and wave directions, and involved wave stirring, coupled with longshore advection of sand along the bar crests in particular. Strong trough and cross-shore channel flows also led to the longshore migration of crescentic dunes. The longshore sediment movements were embedded in a cross-shore gradient associated with increasing overall profile mobility from the lower to the upper beach in response to wave shoaling and post-breaking processes, assessed through examination of the relative wave height Hs h−1, based on the relationship between significant wave height (Hs) and water depth (h). Longshore sediment transport is a characteristic feature of the long-term evolution of Wissant Bay, which is dominated by a net northeastward residual sand transport within a bay sediment cell characterised by significant updrift erosion and downdrift accumulation. Longshore transport should be considered as an essential element of the morphodynamics of bar-trough beaches subject to large tidal ranges and significant wind stress, but there is a need for a better understanding of the role of wind stress on longshore currents in the shallow intertidal zone of these beaches. [Copyright &y& Elsevier]

Abstract: Newly acquired high-resolution Chirp sonar profiles reveal a unique Yellow River-derived, alongshore distributed, bidirectional (landward and seaward) across-shelf transported, omega-shaped (“Ω”) distal subaqueous deltaic lobe deposited around the eastern tip of the Shandong Peninsula in the Yellow Sea. This clinoform deposit directly overlies the postglacial transgressive surface, featured by convex-up seafloor morphology, up to 40 m thick locally. Radiocarbon-14 dates from the underlain pre-Holocene and transgressive sediments indicate this distal lobe has formed since the middle-Holocene highstand under a relatively stable sea level. This along-shelf distributed distal clinoform has been deposited mainly by the resuspended Yellow River sediments carried down by the coastal current, interacting with the local waves, tides and upwelling. Collectively, over the past 7000 years, nearly 30% of the Yellow River-derived sediment has been re-suspended and transported out of the Bohai Sea into the Yellow Sea. Overall, the Yellow River-derived sediment could reach the −80 m water depth in the central South Yellow Sea, about 700 km from the river mouth; in contrast, a very small fraction of the modern riverine sediment could escape the outer shelf or reach the Okinawa Trough. [Copyright &y& Elsevier]

Abstract: Cobble transport is investigated on a mixed sand-and-gravel beach on the high-energy Oregon coast using Radio Frequency Identification technology (RFID) to detect Passive Integrated Transponder (PIT) tags inserted in the gravels. PIT tags are glass-encapsulated transponders that are activated when an antenna passes near them, with each tag characterized by its own unique identification number. The tags are sealed within the cobbles, minimizing any effect on the hydrodynamic character of the particles. The tags draw power from the antenna itself, and have a potential lifespan of up to 50 years. PIT tags are simple to use and inexpensive, permitting the release and tracking of large numbers of gravel particles. As a result, PIT tags have tremendous potential for examining the complexities of particle movement and the parameters that control their distribution on the beach. Our experiments have been conducted at Cape Lookout State Park on the northern Oregon coast, on a composite beach where a seasonally variable sand beach fronts a mixed sand-and-gravel beach, with the latter impacted by waves only during the winter when the sand beach is cut back. A total of 400 cobble tracers have been released at five different locations. Subsequent monitoring of the gravel tracers revealed that they can be detected up to 1 m below the surface of the beach using a 1.0 m diameter antenna, and up to 0.5 m below the surface using a smaller 0.3 m diameter antenna, while their positions were determined using a Trimble 5700/5800 RTK-DGPS survey system. Gravel tracer recovery rates were found to vary significantly between the different release points, from as high as 90% recovery after 8 months, to a low of 18% after 17 months. The lowest recovery rates are thought to be due to the extent of aggradation of the sandy beach during the summer, partially covering the gravel berm and burying the tracer particles to depths where they could not be detected by the antennas used with our RFID system. Relocation of the gravel tracers has revealed a predominant northward migration of the cobbles, and locally demonstrate a strong cross-shore transport (both upslope and downslope movements). Initial attempts to examine the relationship between the transport distances and particle sizes and shapes have thus far revealed that the larger gravels are tending to outrun the smaller particles. This is despite the fact that both small and large particles were found to be capable of being transported both short and long distances. In contrast, our results revealed no relationships between particle shape and distance moved. In time, it is expected that the PIT tag tracers may begin to yield more definitive patterns of sorting. The results did highlight that the gravel movement occurs predominantly near the sand/gravel beach junction on the profiles, a region dominated by a higher incidence of wave breaking and strong swash activity. Finally, our analyses revealed the potential for using PIT tags to provide field assessments of the abrasion rates of gravel particles, having already found measurable degrees of weight loss to abrasion in our experiments. [Copyright &y& Elsevier]

Abstract: Gravel and cobble transport measurements were obtained by particle tracing experiments from a mixed sand, gravel and cobble beach at the head of a crenulate-shaped shoreline, Half Moon Bay in Grays Harbor, Washington. The direct measurements and results provide insight regarding the differential transport of gravel and cobble sized material on mixed-sediment beaches. The results are of relevance to the development of both predictive formulae for coarse-grained sediment transport and guidance for practical gravel and cobble beach design. Net alongshore transport of gravel and cobble is generally several times greater than the net cross-shore transport at Half Moon Bay. Larger and smaller particles both move preferentially alongshore; however, smaller particles tend to move across-shore more than larger particles. Particle transport distance during a tidal cycle increases with particle size (or mass) up to a point, beyond which the particle transport rate begins to decrease with increasing size. The direct relationship between transport rate and particle size may reflect the selective entrainment and the rejection (or overpassing) of larger particles, which are more exposed to fluid forces on the beach surface than smaller particles, which are sheltered within the matrix of larger particles, as well as the higher susceptibility to burial of smaller particles. The decrease in transport rate for the largest sizes may reflect the limited competency of the fluid forces to transport larger and heavier particles under the observed conditions. The direct transport measurements are consistent with the overall particle size and shape distributions observed on this crenulate-shaped inner bank beach whereby the larger and flatter particles have tended to outrun the smaller and more spherical particles in the downdrift direction. [Copyright &y& Elsevier]

Measurements of longshore sediment transport rate were conducted on a reflective to intermediate sandy beach during energetic sea breeze activity. The suspended load transport was obtained with optical backscatter sensors, current meters, and streamer traps, whereas the total load rate was measured with fluorescent sand tracer. The streamer trap measurements revealed an exponential vertical distribution of the suspended sediment flux, with the degree of vertical mixing decreasing in the onshore direction. A continuous time series of longshore suspended sediment flux across the surf zone was obtained by combining streamer trap measurements with data collected with surf zone instruments. Comparison of the suspended longshore flux with the total longshore flux derived from the dispersal of fluorescent tracer indicated that the relative contribution of suspended load to total load was ca. 35%. The movement of sand tracer further demonstrated that nearshore sediments were transported obliquely across the surf zone, challenging our conventional view of dividing nearshore sediment transport into cross-shore and longshore components. Sand tracer was found to move onshore as well as offshore, indicating a bi-directional sediment exchange between outer surf zone and swash zone. Equations from previous studies predicted the suspended longshore transport rate rather well, but underestimated the total longshore transport rate by a factor of two. The Kamphuis formula underestimated both suspended and total longshore transport rates. [ABSTRACT FROM AUTHOR]

Abstract: Formulae for bedload transport of sediments in conditions characteristic of coastal waters are developed from principles of physics. They cover driving forces of: current alone, current plus symmetrical waves, current plus asymmetrical waves, asymmetrical waves alone, and integrated longshore transport. In each case the transport is given as one or more analytical functions of the basic input variables. The formulae are tested against laboratory and field data, and give predictions that lie within a factor of 2 of the measured values for between 47% and 91% of the data, depending on the driving force. The formulae are suited to practical application in coastal waters, especially for transport of coarse materials such as shingle, and also for the bedload component of transport of sand. [Copyright &y& Elsevier]

Spatially and temporally high-resolution video imagery was combined with traditional surveyed beach profiles to investigate the evolution of a rapidly eroding beach nourishment project. Upham Beach is a 0,6-km beach located downdrift of a .structured inlet on the west coast of Florida. The beach was stabilized in seaward advanced position during the 1960s and has been nourished every 4-5 years since 1975. During the 1996 nourishment project, 193,000 m² of sediment advanced the shoreline as much as 175 m. Video images were collected concurrent with traditional surveys during the 1996 nourishment project to test video imaging as a nourishment monitoring technique. Video imagery illustrated morphologic changes that were unapparent in survey data. Increased storminess during the second (El Niño) winter after the 1996 project resulted in increased erosion rates of 0.4 m/d (135,0 m/y) as compared with 0,2 m/d (69.4 m/y) during the first winter. The measured half-life, the time at which 50'7( of the nourished material remains, of the nourishment project was 0,94 years. A simple analytical equation indicates reasonable agreement with the measured values, suggesting that project evolution follows a predictable pattern of exponential decay. Longshore planform equilibration does not occur on Upham Beach, rather sediment diffuses downdrift until 100% of the nourished material erodes. The wide nourished beach erodes rapidly due to the lack of sediment bypassing from the north and the stabilized headland at Upham Beach that is exposed to wave energy. [ABSTRACT FROM AUTHOR]

This work provides a general hydrodynamic circulation model that can be used to understand density driven flows, which may arise in the case of suspension of fine-grained materials. The research is expected to provide a better understanding of the characteristics of spatial and temporal variability of current, which is associated with the period of ebb and flood tidal cycles.The model development includes extending the existing three-dimensional (3D) ADCIRC model with (1) baroclinic forcing term and (2) transport module of suspended and soluble materials. The transport module covers the erosion, material suspension and deposition processes for cohesive type sediment. In the case of an idealized tidal inlet in stratified water, the inclusion of baroclinic term can demonstrate the prevailing longshore sediment transport. It is shown that the model has application to the transport of the cohesive sediments from the mouth of the Mississippi River along the north shore of the Gulf of Mexico towards and along the Texas coast. [Copyright &y& Elsevier]

Sorting of sediment on a beach under wave action takes several forms. Stratified layers of finer and coarser sediment, which depend on wave climate, grain size and beach slope are formed. This complex problem can be simplified by defining the cross-shore and longshore sorting according to the angle between the breaking wave and the coast. In the present study, longshore distribution of sediment as well as corresponding beach profiles was measured in a wave basin. Three-dimensional hydraulic model experiments were performed with regular waves. Eighteen sets of experiments performed in longshore sorting mechanism using two different sand beds. The sorting of the bed material and the formation of armour coats along the beach were defined by grain size distributions and dimensionless parameters for sandy beaches.The rate of sediment transport with grain size sorting was measured in a wave basin. A method introduced sorting process was presented in this study. The sediment rate based on sorting mechanism was also discussed with known methods. It has been found that the non-uniformity of the grain size and hence sorting of the beaches play a very important role in the sand transport due to wave motion in a similar way to the case of steady flow in alluvial channels. [Copyright &y& Elsevier]

The sediment budget of Hanalei Bay on the north shore of Kauai was calculated using sedimentological and geophysical methods. The calculations of the budget subsequently allowed an interpretation of the Holocene history of the bay.The bay sediments are easily separated into marine (carbonate) and terrigenous (siliciclastic) grains. Surficial sediments are dominated by carbonate grains (∼70%) of coralline algae, coral, and mollusc fragments as well as foraminifera, Halimeda, bryozoa, and echinoderm tests. However, siliciclastic grains (e.g. olivine, plagioclase, volcanic lithics) from the Hanalei River watershed draining shield volcanic highlands are the most common individual grain type (∼27%) and form a zone of high concentration from the mouth of the Hanalei River into the center of the bay.Flooding in the bay by the post-glacial sea-level rise began soon after 11.7 kyears. The resulting marine environment caused the net deposition of 45.5±1.5×106 m3 of sediment in the bay and approximately 33.7±11.2×106 m3 of sediment on the Hanalei coastal plain. The total volume of carbonate sediment stored in the bay and coastal plain is greater than the volume likely to have been produced exclusively within the bay during the same time. Calculations indicate that approximately 2490 m3 year−1 have been imported into the bay or coastal plain and deposited since 11,700 years ago. The majority of this sediment influx is likely delivered from the east by the strong tradewind-driven littoral currents that characterize Kauai''s north shore. Net carbonate sediment deposition in Hanalei Bay peaked at a rate of 15,500 m3 year−1 between 5000 and 3000 years ago (when sea level may have been 2 m above present) diminishing to 3890 m3 year−1 from 1000 years ago to the present. This influx is likely to have played a significant role in the mid to late Holocene progradation of the Hanalei shoreline. [Copyright &y& Elsevier]

The harbour of Fortaleza (Ceará - Brazil) is facing infilling processes by sand and fine-grained sediments. The influx of sand into the harbour resulted in the generation and growth of an internal beach (Praia Mansa), located on the sheltered side of the main jetty (Titan). Two tracer studies were performed in the harbour vicinity in order to understand sand transport patterns around the jetty and inside the harbour. For this purpose 1,410 kg (experiment FORT I), and 420 kg (experiment FORT II) of dyed sand were released from a boat at depths between 3.5-5 and 6-11 m below mean sea level, respectively. For FORT I a series of 23 surveys were carried out over a period of two months, including the collection of about 1,000 samples. Detailed maps of sand transport and dispersion were obtained for each survey. During the FORT II experiment only 45 samples were collected at different surveying days, giving an idea of the broad sediment dispersion patterns. The general tracer dispersion and transport pattern observed at FORT II proved that the sediment arriving to the main jetty arrives by littoral drift from the Futuro beach, after bypassing the Titanzinho groin. The analysis of FORT I maps showed that the sand moved along the external part of the Titan jetty at rates about 30 m/day. Subsequently, due to wave refraction and diffraction around the jetty tip, the tracer started to be transported towards the internal part of the harbour. The computed average displacement rate of the tracer head was about 5 m/day. The last survey, 58 days after the tracer release, shows the existence of dyed sand inside the harbour, at the nearshore portion of Praia Mansa beach. This confirms that Praia Mansa is still slowly but continuously accreting, by addition of sediment transported around the jetty. The results also demonstrate the durability and the effectiveness of dyed sands for the study of sediment transport and harbour infilling. [ABSTRACT FROM AUTHOR]

An unusual longshore grain size 'variation series' is examined on North Beach, Kaikoura, for two related reasons: To identify the processes that have been responsible for creating the sediment pattern and; to establish whether there is a relationship between these processes and an erosion problem on the Kaikoura township foreshore. A study of North Beach over 30 years ago revealed an unusual curvilinear grain size pattern that phased in a regular fashion from gravel to sand alongshore, but how such a pattern formed was unknown. Research conducted by the author over three decades later reveals that this same pattern still exists in the beach. Sixty-four surface sediment samples were analysed and modeled by a range of techniques that enabled a thorough examination of the sediment characteristics of the beach. The distinctive longshore variation series is explained fundamentally as two linear grain size series occurring one after the other, and is a combination of modern and relict features. Previously it has been assumed that the Hapuku River has supplied all the sediments to North Beach by a simple southward drift of gravels and sands. Whilst this is partly true, it was determined that a second source, the Kowhai River was also active in the past, contributing materials to the southern part of the shoreline. Sediments from this old source are still present in the beach, preserved by a unique combination of local geomorphological features, and are in effect relict. The Kowhai River has since migrated further south, and this in combination with a recent period of tectonic uplift has caused sediment starvation and subsequent erosion of the township foreshore. Essentially, this links the processes responsible for the longshore sediment grain size pattern with the erosion problem. These findings highlight the importance of source area characteristics and challenge a common assumption that because beaches are dynamic systems, sediment patterns on them must reflect contemporary hydrodynamic processes. [ABSTRACT FROM AUTHOR]