Morphodynamic variability of surf zones and beaches: A synthesis

Brazilian Journal of Oceanography, 2007

Wave action in sandy beach surf zones and its influence on species composition were evaluated at three sites at Pontal do Paraná, Paraná State, between June/2004 and May/2005. At each sampling site, five hauls were performed monthly using a 15 m long, 2.6 m height beach seine with a 5 mm mesh-size. Samplings were carried out at low water spring tides during daylight. A total of 26,866 fishes were collected, amounting to a total weight of 84,838 kg, which were distributed amongst 28 families and 63 taxa. Multi- and univariated methods used indicated that sheltered and moderately exposed beach samples had similar ichthyofaunal composition, being clupeids and engraulids the most abundant at these beaches. Although abiotic factors differed significantly between beaches, depth appears to exert the major influence on ichthyofauna structure by providing less turbulent waters which might have permitted shoals maintenance. Conversely, exposed beach samples differed largely from the other beaches and were influenced primarily by wave height and salinity variables. These were displayed at CCA diagram and through the occurrence of P. virginicus, M. littoralis and T. goodei.

International Journal of Geographical Information Science, 2010

This article presents an object-based conceptual framework and numerical algorithms for representing and analyzing coastal morphological and volumetric changes based on repeat airborne light detection and ranging (LiDAR) surveys. This method identifies and delineates individual zones of erosion and deposition as discrete objects. The explicit object representation of erosion and deposition zones is consistent with the perception and cognition of human analysts and geomorphologists. The extracted objects provide ontological and epistemological foundation to localize, represent, and interpret erosion and deposition patches for better coastal resource management and erosion control. The discrete objects are much better information carriers than the grid cells in the field-based representation of source data. A set of spatial and volumetric attributes are derived to characterize and quantify location, area, shape, orientation, depth, volume, and other properties of erosion and deposition objects. Compared with the conventional cell-by-cell differencing approaches, our object-based method gives a concise and high-level representation of information and knowledge about coastal morphological dynamics. The derived attributes enable the discrimination of true morphological changes from artifacts caused by data noise and processing errors. Furthermore, the concise object representation of erosion and deposition zones facilitates overlay analysis in conjunction with other GIS data layers for understanding the causes and impacts of morphological and volumetric changes. We have implemented a software tool for our object-based morphological analysis, which will be freely available for the public. An example is used to demonstrate the utility and effectiveness of this new method.

Sociedade & Natureza (online), 2010

In oceanic beaches of Rio de Janeiro drowning accidents are identified as a major public security problem in recreational environments. The number of rescues of bathers in these beaches reaches 5000 per year. The aim of this study is to identify critical morphodynamic beach conditions on the surfzone that represent hazards and can expose bathers to the risk of drowning and other associated injuries. These hazards are breaking waves, surfzone bottom topography and the formation of longshore and rip currents, named here as nearshore circulation cell. These are a result of physical interaction between hydrodynamic marine conditions promoted by waves with the adjustment of the sandy bottom topography on the surfzone, and while people use these beaches as a recreational place, this can promote unsafely conditions for most swimmers. The evaluated hypothesis is that previous identification of hazardous beach conditions, which can be made by the identification of modal wave climate, and the morphodynamic response of each beach for the input of wave energy, can generate differentiated conditions along the beaches and even along the same beach. Morphodynamic analysis can identify several hazards and. rescue data can be used to identify areas where the most accidents take place and areas of high concentration of bathers. The result reached is a forecasting guide of hazardous beach conditions, which correlates breaking wave height, tidal oscillations and morphodynamic beach states.

Italian Journal of Zoology, 2010

Meiofauna assemblages of three Italian Marine Protected Areas (MPAs), Miramare (Trieste, Friuli-Venezia Giulia), Porto Cesareo (Lecce, Apulia) and Capo Caccia (Sassari, Sardinia), were investigated. Sediment samples were collected during summer 2005 in the shallow subtidal (1-4 m depth). The meiofauna was primarily represented by Nematoda and Copepoda. The results showed that significant differences in meiofauna communities abundances were found among the three Italian MPAs, and in particular between Capo Caccia and Porto Cesareo (3840 ± 422 SE individuals·10 cm -2 at Miramare, 5716 ± 857 SE ind.·10 cm -2 in Porto Cesareo, and 1063 ± 289 SE ind.·10 cm -2 in Capo Caccia). These differences were mainly due to a clear change in nematodes and copepods abundances in the two MPAs. Meiofauna diversity was not significantly different among the three MPAs. The analysis on nematode communities showed a dominance of deposit feeders in Porto Cesareo (Anoplostoma, Daptonema and Theristus), while in the marine reserves of Miramare and Capo Caccia epigrowth feeding nematodes, and predators/omnivores were dominant (Mesacanthion, Marylynnia). The results reported here represent a new contribution to the knowledge of the Mediterranean meiofauna and nematode assemblages structure and composition.

Earth Surface Processes and Landforms, 2010

Crescentic sandbars and rip channels along wave-dominated sandy beaches are relevant to understand localized beach and dune erosion during storms. In recent years, a paradigm shift from hydrodynamic template models to self-organization mechanisms occurred to explain the formation of these rhythmic features. In double sandbar systems, both the inner-and outerbar rip channels and crescentic planshapes are now believed to be free instabilities of the nearshore system arising through selforganization mechanisms alone. However, the occasional occurrence of one or two inner-bar rip channels within one outer-bar crescent suggests a forced, morphologically coupled origin. Here we use a nonlinear morphodynamic model to show that alongshore variability in outer-bar depth, and the relative importance of wave breaking versus wave focussing by refraction across the outer bar, is crucial to the inner-bar rip channel development. The coupling patterns simulated by our model are similar to those observed in the fi eld. Morphological coupling requires a template in the morphology (outer-bar geometry) which, through the positive feedback between fl ow, sediment transport and the evolving morphology (that is, self-organization) enforces the development of coupling patterns. We therefore introduce a novel mechanism that blurs the distinction between self-organization and template mechanisms. This mechanism may also be extended to explain the dynamics of other nearshore patterns, such as beach cusps. The impact of this novel mechanism on the alongshore variability of inner-bar rip channels is investigated in the companion paper.

Marine Ecology, 2014

The spatial and temporal patterns within the surf zone epibenthic assemblages were studied in a coastal fringe of Argentina to determine whether assemblage compositions, abundance, species richness and diversity vary spatially and temporarily. Sampling was conducted seasonally in two sandy beaches over 2 years with a benthic sledge used to collect the fauna in the upper centimeters of soft bottom sediments and the epifauna on the sediment surface. Physical variables were measured in the same coastal sites where biological sampling was conducted. A total of 58 morphospecies were collected. Peracarid crustaceans were the most abundant group. The mysid Pseudobranchiomysis arenae (new genusnew species) (29.73 AE 17.79 ind. per sample) and the isopod Leptoserolis bonaerensis (51.54 AE 22.35 ind. per sample) were the most abundant and common species and were present regularly throughout the sampling period. Differences in the surf zone community composition were found between the beaches; these differences could be related to variation in physical parameters such as sand grain size and wave climate, indicating the possible influence of the morphodynamic state of the beaches on the epibenthic assemblages. A seasonal abundance trend was detected, reflecting the changes in abundance of the two dominant species; the richness pattern was not easily detectable due to the sporadic appearance of non-resident species in the surf zone, probably due to different causes, including dispersion by entry of water from surrounding areas, littoral currents and storms. The surf zone studied presents a complex and dynamic epibenthic community that appears to be influenced by the morphodynamic state of the beach and the dynamic of non-resident species.

Estuaries and Coasts, 2011

Sea turtles are highly susceptible to plastic ingestion and entanglement. Beach debris were surveyed along the most important sea turtle nesting beaches in Brazil (Costa dos Coqueiros, Bahia State). No significant differences among developed and undeveloped beaches were observed in terms of total number of items. Local sources (tourism activities) represented 70% of debris on developed beaches, where cigarette butts, straws, paper fragments, soft plastic fragments, and food packaging were the most abundant items. Non-local sources (domestic and fishing activities) accounted for about 70% of debris on undeveloped beaches, where the most abundant items were rigid plastic fragments, ropes, soft plastic fragments, caps, and polystyrene. The projected surface area of beach debris did not vary among developed and undeveloped beaches. Overseas containers accounted for about 25% of regional plastic pollution, implying that international pollution prevention agreements are not being respected off the Brazilian coast.

Ocean Dynamics, 2011

A large multi-institutional nearshore field experiment was conducted at Truc Vert, on the Atlantic coast of France in early 2008. Truc Vert'08 was designed to measure beach change on a long, sandy stretch of coast without engineering works with emphasis on large winter waves (offshore significant wave height up to 8 m), a threedimensional morphology, and macro-tidal conditions. Near-shore wave transformation, circulation and bathymetric changes involve coupled processes at many spatial and temporal scales thus implying the need to improve our knowledge for the full spectrum of scales to achieve a comprehensive view of the natural system. This experiment is unique when compared with existing experiments because of the simultaneous investigation of processes at different scales, both spatially (from ripples to sand banks) and temporally (from single swash events to several spring-neap tidal cycles, including a major storm event). The purpose of this paper is to provide background information on the experiment by providing detailed presentation of the instrument layout and snapshots of preliminary results.

Journal of Geophysical Research, 2011

Video measurements of wave runup were collected during extreme storm conditions characterized by energetic long swells (peak period of 16.4 s and offshore height up to 6.4 m) impinging on steep foreshore beach slopes (0.05 -0.08). These conditions induced highly dissipative and saturated conditions over the low-sloping surfzone while the swash zone was associated with moderately reflective conditions (Iribarren parameters up to 0.87). Our data support previous observations on highly dissipative beaches showing that runup elevation (estimated from the variance of the energy spectrum) can be scaled using offshore wave height alone. The data is consistent with the hypothesis of runup saturation at low frequencies (down to 0.035 Hz) and a hyperbolic-tangent fit provides the best statistical predictor of runup elevations.

Méditerranée, 2007

Journal of Geophysical Research: Earth Surface, 2014

Coastal zone management requires the ability to predict coast-14 line response to storms and longer-term seasonal to inter-annual variability 15 in regional wave climate. Shoreline models typically rely on extensive his-16 torical observations to derive site-specific calibration. To circumvent the chal-17 lenge that suitable data sets are rarely available, this contribution utilizes 18 twelve 5+ year shoreline data sets from around the world to develop a gen-19 eralized model for shoreline response. The shared dependency of model co-20 efficients on local wave and sediment characteristics is investigated, enabling 21 the model to be recast in terms of these more readily measurable quantities.

Iheringia. Série Zoologia, 2009

Composition and spatio-temporal variability of meiofauna community on a sandy beach in the Amazon region (Ajuruteua, Pará, Brazil). The present study investigates the spatio-temporal changes in the meiofauna community along the intertidal zone of Ajuruteua Beach, State of Pará, Brazil. Samples were collected during spring tides at different levels of the beach face every two months from April 2003 to February 2004. The material was sampled using a cylindrical corer (3.14 cm 2 ) and fixed with 5% saline formalin. In the laboratory, samples were sieved through a 0.063 mm mesh screen and the retained organisms were identified at higher taxonomic levels, counted and preserved in ethanol 70%. Meiofauna was composed of eight groups: Turbellaria, Nematoda, Tardigrada, Polychaeta, Oligochaeta, Acari, Copepoda and nauplius (Copepoda). Nematoda was the dominant group, representing 74% of total organisms, followed by Copepoda (19%). A clear faunal zonation was observed on three lines parallel to the shoreline, which showed significant differences in abundance, richness and density of the main taxonomic groups. The mean density was lowest in April and highest in December. The highest densities and richness were recorded in the mid intertidal zone, while the lowest values were recorded in the upper and lower intertidal zones. Meiofauna community was most rich and abundant during the dry months, although differences were not significant between climatic periods. The main factors involved in the spatio-temporal variations of meiofauna were wave and tidal action and salinity fluctuations.

Marine Geology, 1995

Beaches and barriers on many mid-to high-latitude coasts comprise mixtures of fine and coarse elastic materials forming a distinctive morphodynamic environment. In many cases, the sediments are derived primarily from limited glacigenic deposits and the coasts are considered paraglacial. Over relatively long time scales (decades to centuries), coarse-elastic barriers on such coasts show evidence of self-organisation through large-scale morphological evolution and facies differentiation. This process involves gradual reworking, partitioning, and textural sorting of material toward transport minima. Long intervals of slow evolution are punctuated by episodes of rapid reorganisation, involving breakdown of stable barrier structures and facies patterns, remixing of sediment, and accelerated migration of transgressive systems. Drift-aligned systems develop longshore cell structure, sometimes leading to breaching and segmentation, and may evolve toward progressively greater swash alignment under appropriate circumstances. Swashaligned systems may experience catastrophic transformation when appropriate environmental triggers lead to threshold exceedance in the morphodynamics of the shore system. Adjacent barriers may show quite different behaviour, depending on the antecedent states of individual coastal cells. While appropriate parameterisations and sediment budget formulations allow us to model the long-term evolution of some barrier structures, the non-linear dynamics that appear to dominate large-scale behaviour may limit predictability. The identification of stability threshold criteria remains an important research priority.

Environmental Geology, 2008

This work presents the results of a beachmonitoring program carried out in the Bay of Cadiz (SW Spain), which consists of urban, natural and nourished beaches. In the present study, 24 topographic profiles have been monthly monitored during the 1996-1998 period, in order to draw the morphodynamic behavior of this coast and the general characterization of short-term coastal trends. This way, total volumetric budgets have been calculated for each beach profile in order to group beaches in different erosive/accreting sectors. Studied beaches recorded both erosion and accretion: the greatest accretionary trends have been observed at Aguadulce, La Costilla and Rota beaches, with values ranging from 30 to 70 m 3 /m. The largest erosion episodes have been recorded in the southernmost end of Valdelagrana spit, with values over 50 m 3 /m, and in Rota and Vistahermosa, after nourishment works. Main erosion and accretion pathways have been related to the existence of natural and human structures, which blocked the longshore drift suggesting the existence of littoral cells.

Ocean Dynamics, 2012

The study aims to calibrate/validate and apply the dune-erosion model, XBeach, in order to predict morphological response to storm events along a meso-tidal, steeply sloping beach. More than 10,000 XBeach calibration runs, including different model parameters and erosion events, were compared with measurements of beach-profile response to storm conditions. Off-shore wave and tidal measurements were used as input for a SWAN wave model, which was used to provide wave conditions to XBeach. The results indicate that using XBeach to predict beachprofile morphodynamic response during storm events on steeply sloping intermediate-to-reflective beaches may be more demanding than for dissipative beaches and that the default model setup can overestimate dune/beach-face erosion. The performance of the model after calibration was satisfactory, with Brier Skill Scores from 0.2 to 0.72. XBeach was found to be more sensitive to input parameters such as the beach-face slope and the surf similarity parameter ξ (especially for values ξ>0.6). The calibrated XBeach setup was used for simulations of storm scenarios with different return periods (5, 25, and 50 years), and the simulations highlighted the fragility of the dune field and the potential for storm-induced dune retreat, lowering, and overwash in the study area. Finally, the nested SWAN/ XBeach models were forced by an existing operational wave-forecast WAVEWATCH-III/SWAN model, operated by the Portuguese Hydrographic Institute to generate daily forecasts of storm impact and serve as a prototype-case for an early warning system for storm hazard mitigation.

Ocean Dynamics, 2011

This study discusses site-specific system optimization efforts related to the capability of a coastal video station to monitor intertidal topography. The system consists of two video cameras connected to a PC, and is operating at the meso-tidal, reflective Faro Beach (Algarve coast, S. Portugal). Measurements from the period February 4, 2009 to May 30, 2010 are discussed in this study. Shoreline detection was based on the processing of variance images, considering pixel intensity thresholds for feature extraction, provided by a specially trained artificial neural network (ANN). The obtained shoreline data return rate was 83%, with an average horizontal cross-shore root mean square error (RMSE) of 1.06 m. Several empirical parameterizations and ANN models were tested to estimate the elevations of shoreline contours, using wave and tidal data. Using a manually validated shoreline set, the lowest RMSE (0.18 m) for the vertical elevation was obtained using an ANN while empirical parameterizations based on the tidal elevation and wave run-up height resulted in an RMSE of 0.26 m. These errors were reduced to 0.22 m after applying 3-D data filtering and interpolation of the topographic information generated for each tidal cycle. Average beach-face slope tan(β) RMSE were around 0.02. Tests for a 5-month period of fully automated operation applying the ANN model resulted in an optimal, average, vertical elevation RMSE of 0.22 m, obtained using a one Responsible Editor: Pierre-Marie Poulain This article is part of the Topical Collection on Multiparametric observation and analysis of the Sea tidal cycle time window and a time-varying beach-face slope. The findings indicate that the use of an ANN in such systems has considerable potential, especially for sites where long-term field data allow efficient training.

Meteorology and Atmospheric Physics, 2014

Ground-based aerosol instrumentation covering particle size diameters from 25 nm to 32 lm was deployed to determine aerosol concentration and cloud condensation nuclei (CCN)-activation properties at water vapor supersaturations in the range of S = 0.20-1.50 % in the remote Brazilian northeast semi-arid region (NEB) in coastal (maritime) and continental (inland) regimes. The instruments measured aerosol number concentration and activation spectra for CCN and revealed that aerosol properties are sensitive with respect to the sources as a function of the local wind circulation system. The observations show that coastal aerosol total number concentrations are above 3,000 cm -3 on average, exhibiting concentration peaks depending on the time of the day in a consistent daily pattern. The variation on aerosol concentration has also influences on the fraction of particles active as CCN. At 1.0 % water vapor supersaturation, the fraction can reach as high as 80 %. Inland aerosol total concentrations were about 1,800-1,900 cm -3 and did not show much diurnal variation. The fraction of particles active as CCN observed inland depend on the history of the air masses, and was much higher when air masses were originated over the sea. It was found that (NH 4 ) 2 SO 4 and NaCl are the major soluble inorganic fraction of the aerosols at the coast. The major fraction of NaCl was present in the coarse mode, while ammonium sulfate dominates the inorganic fraction at the submicron range, with about 10 % of the total aerosol mass at 0.32 lm. Inorganic compounds are almost absent in particles with sizes around 0.1 lm. The study suggests that the air masses with high concentration of CCN originate at the sea. The feasible explanation lies in the fact that the NEB's beaches have a particular morphology that produces a wide surf zone and creates a large load of aerosols when combined with strong and permanent winds of the region.

Earth Surface Processes and Landforms, 2014

Proxies, such as changes in beach profiles and shoreline positions, are commonly used in management and research for estimating changes in subaerial beach volume; however, the accuracy of these proxies across increasing time scales and complex morphologies is unclear. Volume changes associated with along-beach morphologic variability may not be captured well by changes in profiles, while volume changes associated with across-beach morphologic variability may not be captured well by measuring shoreline change. This study assesses the impacts of morphologic variations, associated with beach cusps and nourishment material, on volume change estimates from profiles and shoreline change at 0.5 to 3.5 year time periods. Results indicate that profiles spaced ≥ 150 m apart and the shoreline-change proxy will likely estimate volume change inaccurately over periods ≤ 1 year at beaches that are consistently eroding or accreting and contain cusps. However, over longer time periods (1-3.5 years), estimates of volume change from both proxies improved at those types of beaches. Volume changes at the edges of nourishment areas are not captured well by profiles. When the nourishment material is graded to a ramped morphology, which minimizes across-beach morphologic variability, the shoreline-change proxy does accurately estimate volume changes. Both proxies estimate volume changes inaccurately at beaches where volume changes oscillate between erosion and accretion on both short and long time scales because the magnitude of small-scale changes in volume from the formation and erosion of morphologic features, such as cusps and berms, will always be similar to the longer-term net volume change. This study suggests that decadal records of shoreline change, which are commonly developed using aerial photography, can be used to help identify the best proxy for estimating volume change; however, recent anthropogenic modifications that impact patterns of beach sedimentation, including nourishment, terminal groins, and inlet-channel dredging, makes decadal records less useful.

Solutions to Coastal Disasters '02, 2002

The intertidal beach profile of a low-energy microtidal beach was monitored at regular intervals for a period of six months over the winter season 2000-2001. In addition to that, selected surveys were undertaken following medium energy (H s <1.5 m) events known to generate beach changes in the area (E-SE winds). The response of the beach to these events was modeled using the convolution method, simulating the response of the profiles as surveyed immediately before the event. The model generally does not represent correctly the observed evolution of the beach above Mean Sea Level (MSL), possibly because the effect of storm surges was not included. On the other hand, the performance of the model is better for the submerged beach. A simulation of the impact of the 1-year wave event was undertaken, using the surveyed profile that seemed the most stable. The underwater changes underline a flattening of the lower shoreface, but the intertidal bar maintains its shape and erosion of the dune face is limited. This underlined the important role of the dune-trough-bar system in protecting the back-barrier environment, although its behavior under a consistent storm surge remains to be studied. Finally, a longer term (10 years) evaluation of profile response was undertaken using the Bruun's Rule, considering a worst-case scenario of Relative Sea Level Rise of 13.4 mm/year, which is locally controlled by subsidence. A shoreline retreat of 7.4 m is forecasted for the next 10 years. Once again, the largest impact is predicted for the system where the dune-bar system is not fully developed.

Geographical Research, 2012

Waves are an important process responsible for the initiation and subsequent development of intertidal shore platforms. However, few field studies to date have described wave processes on shore platforms. A field experiment was conducted using an across-shore array of wave gauges, including a directional sensor, on a near-horizontal platform at Mahia Peninsula, North Island, New Zealand. Results show that the platform is very efficient in filtering wave energy at gravity wave frequencies (>0.05 Hz), with 40-80% reduction in wave height measured across the 140 m wide platform. By contrast, infragravity waves are present on the platform and increase in magnitude towards the cliff toe. Directional wave analysis indicates that wave reflection is mainly restricted to infragravity wave frequencies, demonstrating the differences in gravity and infragravity wave behaviour on the platform studied. Results indicate that, under fair weather conditions, the role of waves as an agent of cliff toe erosion is likely to be limited at present, although they are probably important for removing sediments accumulated at the cliff toe. The observed increase in infragravity wave energy towards the cliff toe implies that these long-period waves may be important geomorphic agents on shore platforms.

Journal of Geophysical Research, 1998

Méditerranée, 2007

Journal of Geophysical Research, 2002

1 ] Wave and current measurements are presented from a set of laboratory experiments performed on a fixed barred beach with periodically spaced rip channels using a range of incident wave conditions. The data demonstrate that the presence of gaps in otherwise longshore uniform bars dominates the nearshore circulation system for the incident wave conditions considered. For example, nonzero cross-shore flow and the presence of longshore pressure gradients, both resulting from the presence of rip channels, are not restricted to the immediate vicinity of the channels but instead are found to span almost the entire length of the longshore bars. In addition, the combination of breaker type and location is the dominant driving mechanism of the nearshore flow, and both are found to be strongly influenced by the variable bathymetry and the presence of a strong rip current. The depth-averaged currents are calculated from the measured velocities assuming conservation of mass across the measurement grid. The terms in both the cross-shore and longshore momentum balances are calculated, and their relative magnitudes are quantified. The cross-shore balance is shown to be dominated by the cross-shore pressure and radiation stress gradients in general agreement with previous results, however, the rip current is shown to influence the wave breaking and the wave-induced setup in the rip channel. Analysis of the longshore balance shows that the overall strength of the longshore feeder currents is governed by a balance between longshore pressure gradient forcing and an opposing radiation stress gradient. In addition, the longshore feeder currents show maxima in the bar trough region, providing experimental evidence that longshore pressure gradients can shift longshore current maxima shoreward from the bar crest. Finally, since the longshore radiation stress gradient in the surf zone is governed by the amount of wave dissipation on the rip current, there exists a positive feedback mechanism whereby a strong rip current can weaken the radiation stress gradient opposing the feeder currents and lead to even stronger feeder currents and rips.

Marine Ecology, 2008

an evolutionary perspective marine ecology

Environmental Monitoring and Assessment, 2011

The INSHORE system (INtegrated System for High Operational REsolution in shore monitoring) is a land-base survey system designed and developed for the specific task of monitoring the evolution in time of sandy shores. This system was developed with two main objectives: (1) to produce highly accurate 3D coordinates of surface points (in the order of 0.02 to 0.03 m); and (2) to be extremely efficient in surveying a beach stretch of several kilometres. Previous tests have demonstrated that INSHORE systems fulfil such objectives. Now, the usefulness of the INSHORE system as a survey tool for the production of Digital Elevation Models (DEMs) of sandy shores is demonstrated. For this purpose, the comparison of DEMs obtained with the INSHORE system and with other relevant survey techniques is presented. This comparison focuses on the final DEM accuracy and also on the survey efficiency and its impact on the costs associated with regular monitoring programmes. The field survey method of the INSHORE system, based on profile networks, has a productivity of about 30 to 40 ha/h, depending on the beach surface characteristics. The final DEM precision, after interpolation of the global positioning system profile network, is approximately 0.08 to 0.12 m (RMS), depending on the profile network's density. Thus, this is a useful method for 3D representation of sandy shore surfaces and can permit, after interpolation, reliable calculations of volume and other physical parameters.

Marine Geology, 1995

Recent work has advanced our understanding of mixed sand-gravel littoral systems in glaciated regions. New insights include the nature and causes of coastal instability and conditions for preservation of Holocene barrier deposits on paraglacial shelves. The best-preserved relict barrier structures recognized on the inner shelf of southeastern Canada are interpreted as postglacial lowstand deposits, initiated under stable to slowly rising relative sea level in areas of substantial shelf relief. A largely intact early-Holocene gravel foreland survives at 38 m present water depth, its preservation attributed in part to sediment volume and a partially protected location. The mechanism by which this structure was abandoned and overstepped is unclear, but may be related to accelerating sea-level rise. In some cases, barriers keep pace with sea-level rise for some time before being overstepped or reworked landward. The duration and extent of preservation depend in part on the deposit volume, as smaller accumulations are consumed and reworked more quickly. Deposit volume is a function of sediment supply, accommodation space, and headland spacing, among other factors. Where barriers are small and thin, beach sediments, overtaken by the transgression, may be smeared across the shoreface in a thin post-transgressive veneer. In such settings, as along the Eastern Shore of Nova Scotia, the only coastal units preserved on the shelf are back-barrier estuarine facies in flooded-valley depressions. Differential preservation is governed by shelf relief and accommodation space, coastal alignment and compartmentalisation, sediment supply and barrier volume, rate and acceleration of sea-level rise, wave energy and potential for sediment reworking on the inner shelf.

Environmental Fluid Mechanics, 2013

We present a numerical model based on the hydro-morphodynamical coupling to study coastal sandbar migration. In order to improve both nonlinear and dispersive wave processes in relatively shallow water, we developed a finite element model based on the Legendre polynomials and on the Extended Boussinesq model. This model reproduces the propagation of wave trains with a high degree of accuracy on a greater range of depths than the standard Boussinesq models. We also implemented the Total Variation Diminishing schemes to improve the quality of the computed hydrodynamic fields, especially in areas where sharp flow gradients occurred. The coupled morpho-hydrodynamical model is then used to simulate the migration of real sandbars observed at Rousty beach (Mediterranean French coast). For verification the model results are compared with field measurements obtained from a small-scale field campaign carried out over two years at Rousty beach, and the results of this comparison are thoroughly discussed and analyzed.

Continental Shelf Research, 1996

AbstractmAn initially uniform longshore current on a plane erodible beach is considered and a linear stability analysis of the bed-flow system is performed in order to investigate the growth of alongshore periodic topographic features such as transverse or oblique bars. A numerical model based on the shallow water equations and a simple sediment transport formula is used. For a wide range of parameters instability is found, leading to the growth of large-scale topographic features (lengthscale of the order of the current width) downflow progressing. The growth rates and the dominant unstable mode depend mainly on R = cdl fl parameter, where c d is the bottom friction coefficient and fl is the beach slope. For a small R, say less than 0.1, instability is very weak, probably negligible. For R between 0.1 and 0.7 instability increases with R, leading typically to a quite simple transverse bars pattern. A further increase in R produces a far more complicated behaviour where complex patterns with downcurrent oriented oblique bars, bumps and holes can be dominant. In this region growth rates may either decrease or increase with R depending on the beach slope and the maximum Froude number of the basic flow, F. Usually, the most complex behaviour is found for gently sloping beaches. The physical mechanism of the instability is found to lie on the disturbances of potential vorticity caused by topographically induced differences in bottom friction. In this sense it is similar to the alternate bars growth in a river rather than the dunes or antidunes occurrence for 1D channel flow. The predictions of the model compare well with the available experimental data. The alongshore wavelength, 2, typically of the order of one to four times the width of the current, is close to four times for the most common values of R. The typical growth time is proportional to it 2 and for a wavelength of 100 m can be of the order of one day, depending on the sediment transport rate. The migrational speed is inversely proportional to 2, in accordance to earlier field data reported by Sonu [(1969) Collective movement of sediment in littoral environment.

Diversity and Distributions, 2014

Aim Spatially-explicit trends in species richness and endemism on sandy shores are quantified to assess representation of beach ecosystems in existing reserve networks. Also, the relative importance of different drivers of species distributions are compared through species distribution modelling. Location The South African beaches are among the best-studied in the world, providing sufficient biological data for the analyses. There is also a well-established coastal protected-area network that putatively provides moderate protection to nearly all beach habitats.

Marine Georesources & Geotechnology

The cross-shore profile and the textural distribution of foreshore sediments of Ganpatipule beach along Maharashtra coast covering two annual cycles are examined. Ganpatipule beach depicts erosion and accretion of the berm, reduction and widening of foreshore widths during the monsoon (June-September) and post-monsoon (October-May), respectively with net sediment accretion during the study period due to the changes in the wave characteristics. A direct correlation is observed between the median sediment grain size and beach-face slopes signifying high wave energy ensuing to a gentle to very gentle slope. The sediments are mainly medium grain size, moderately well sorted, bimodal, very fine skewed to very coarse skewed and very platykurtic to very leptokurtic in nature. The binary plots of the textural parameters (mean, skewness, kurtosis, and standard deviation) depicted a characteristic beach environment of deposition. The study shows that the sediment is concentrated in the environment of rolling and bottom suspension. The study on grain size distribution of sediments could be used to assess the wave energy condition prevailing along the coastal area.

Anais da Academia Brasileira de Ciências, 2010

The coastal sedimentation model in the Doce River mouth and surroundings extends beyond the hydraulic jetty effect created by its stream-flow. During flooding, marine sediments transported by longshore currents are retained on the updrift side, causing strandline progradation. As the longshore current direction varies, local depositional and erosional effects can be produced and identified laterally within beach profiles from north and south of the Doce River mouth area. Sedimentological studies carried out in this river, beach and adjacent inner continental shelf sands showed that, at present, the influence of Doce River sediments is restricted to the area surrounding its mouth. Meanwhile, beach morphodynamic stages and present-day coastal-plain processes of sedimentation are directly affected by the Doce River discharge as a natural continuation of the Quaternary geological evolution of the area.

Brazilian Journal of Oceanography

Wave-dominated embayed beaches on irregular rocky coastlines are highly appreciated for their landscapes and tourism potential. Yet our understanding about the interaction of the oceanographic processes with the geological inheritance in this type of beaches still needs further investigation to better understand their natural balance. In this study, we apply the classical approach of morphodynamics to describe for the first time the variations in the Boiçucanga beach morphology, an embayed beach located in São Sebastião City on an irregular rocky coastline that is well known for its beautiful beaches embedded in the valleys of Serra do Mar. Field surveys were performed over 15 months, between April 2008 and September 2009, seeking to evaluate the interactions among the morphology, sediments and hydrodynamic characteristics at Boiçucanga. All data generated during the field surveys have supported the application of the following morphodynamic models: Classification of morphological b...

Geosciences

In this study a video-monitoring system was used to analyze the presence of mesoforms during a time period of five years in the urban beach of La Victoria, Cádiz, Spain. This technique allowed the generation of plan views using an improved version of ULISES software. The presence and spatiotemporal variability of the most common mesoforms, such as bars and cusps, was identified in all the plan views. Furthermore, the morphodynamic state of the beach was investigated in combination with local hydrodynamic data. The cusp systems were also studied by means of wavelet analyses and different theories on cusps formation were tested. The presence of the investigated features was related to the wave energy and its seasonal variations. The behavior of the mesoforms demonstrated the important role of a subtidal rocky outcrop in the nearshore processes. The results also show that bars and cusps as indicators of the nearshore processes are a useful tool for the macroscopic analysis of surf zone...

Journal of Marine Science and Engineering

A field experiment was conducted at a tropical microtidal intermediate sandy beach with a low tide terrace (Nha Trang, Vietnam) to investigate the short-term swash-zone hydrodynamics and morphodynamics under variable wave conditions. Continuous 2D Lidar scanner observations of wave height at the lower foreshore, subsequent run-up and swash-induced topographic changes were obtained. These data were complemented by detailed real-time kinematic GPS topographic surveys. Variable wave and tide conditions were experienced during the field experiment with relatively large swell waves (offshore significant wave height, Hs = 0.9 m to 1.3 m; peak wave period, Tp = 8 to 12 s) concomitant with spring tides at the beginning of the period, followed by mild wind waves (offshore Hs under 0.5 m and Tp 5 s) and neap tides. This resulted in the following morphological sequence: berm erosion followed by rapid neap berm reformation and beach recovery within a few days. New insights into the link between...

Water

To develop beach engineering, the submerged structure’s primary physical functions have to be understood. This study focuses on submerged structures in order to understand the strategy of reduced wave energy, stabilizing the shoreline and not generating erosion or adversely modifying coastal processes. Important developments have been made since the 1990s, taking into account the functions of recreational amenity. However, non-dimensional models cannot explain the physical mechanisms that generate accretion or erosion morphological features in the lee of the submerged structure. The present study aims to collaborate with the understanding of the mechanism of beach response to a submerged structure. For this, 26 surveys were made using topographic, Lagrangian, and Eulerian hydrodynamic measures during one seasonal cycle of a beach system from Rio de Janeiro (Brazil) with a natural submerged reef or rocky bank V-shape in the plan. This beach system is energetic and intermediate when r...

Journal of Marine Science and Engineering

Accurate wave runup estimations are of great interest for coastal risk assessment and engineering design. Phase-resolving depth-integrated numerical models offer a promising alternative to commonly used empirical formulae at relatively low computational cost. Several operational models are currently freely available and have been extensively used in recent years for the computation of nearshore wave transformations and runup. However, recommendations for best practices on how to correctly utilize these models in computations of runup processes are still sparse. In this work, the Boussinesq-type model BOSZ is applied to calculate runup from irregular waves on intermediate and reflective beaches. The results are compared to an extensive laboratory data set of LiDAR measurements from wave transformation and shoreline elevation oscillations. The physical processes within the surf and swash zones such as the transfer from gravity to infragravity energy and dissipation are accurately acco...

Frontiers in Marine Science, 2016

Journal of African Earth Sciences, 1988

Unlike the mechanisms and seasonality in scale of beach changes, very little is known about the routes of beach response to littoral processes essential in a variety of coastal studies. From continuous monitoring of littoral processes during a storm season and measurements of dimensions of some geomorphic elements at seven sectors of the Victoria Beach, nine possible routes of beach response have been defined and tentatively related to magnitude of beach changes observed. The beach response routes are distinguished by the variability or stability in monthly maximum height of berm scarp and beach face slope when compared with previous dimensions. Both geomorphic elements exist as inheritance of the antecedent wave-state. Besides beach sector 7, all others persistently retrograded. Monthly maximum linear and volumetric rate of retrogression were 2.76 m and 0.76 m 3 per metre of beach length respectively. Compared with the preceding calmer coastal condition, retrogression rate was generally greater by a factor of nine at most sectors during the study period. The highest volumetric rate of retrogression evident at sector 3 was associated with the bimodal occurrence of route 4 (reduced values of scarp height and beach face slope) and route 6 (same scarp height and steeper slope). Beach response route 3 modally represented at sectors 2 and 7 indicates low rate of retrogression. The short duration of investigation and the non-representation of some routes are major constraints to the complete ranking of the latter on a severity scale of beach retrogression.

Ocean Dynamics, 2014

Spatial patterns of multi-decadal shoreline changes in two microtidal, low-energetic embayments of southern Sealand, Denmark, were explained by wave energy flux distributions. The first site is a barrier system attached to a moraine island. The system is characterized by an alignment of the barrier through alongshore alternating directions of barrier spit progradation and cross-shore translation of small barrier islands in a bidirectional wave field. The other site consists of a recurved spit adjacent to a cliff coast. This spit experiences shoreline rotation through proximal erosion and distal lateral accretion in a unidirectional wave climate. Multi-decadal shoreline changes were coupled with a slope-based morphological coastal classification and with the alongshore variability of the directional distribution of wave energy fluxes to outline potential sediment sources and sinks.

Neotropical Ichthyology, 2014

A comparative study involving three mesotidal beaches from reflective to estuarine states was conducted between October 2010 and September 2011 in the estuary of Mamanguape River, northeastern Brazil. The aim was to test for differences in fish assemblages along a morphodynamic continuum, particularly the effects of wave action. In total, 3,732 fish from 71 species were examined; Rhinosardinia bahiensisand Atherinella brasiliensisdominated the estuarine beach, whereas Trachinotus carolinus dominated the reflective beach. Fish assemblages were structured by spatial differences among the sites, and overall abundance, richness and biomass demonstrated a clear increasing trend from the reflective to the estuarine beaches, indicating a primary influence of wave exposure in the measured parameters. The Mamanguape River estuary plays a crucial ecological role as a nursery for several species that depend on its resources and have adapted to the high variability of its physical and chemical ...

Revista Brasileira de Oceanografia, 2000

A morfologia das praias é reflexo da ação hidrodinfunica com o tipo de sedimento disponível. Esta int~ação se dá a partir da base de ação das ondas, tornando-se mais efetiva na zona de arrebentação onde a energia é dissipada, originando wna zona de surfe que se estende em direção à linha de costa até Q limite do espraiamento na face de praia. O objetivo deste trabalho é apresentar as características morfodinâmicas do litoral NE do Estado do Rio de Janeiro, baseando-se na análise da variação espaço Hemporal de perfis de praia, na morfologia da plataforma continental e em fotos aéreas. Os perfis de praia foram levantados durante cinco anos pela PETROBRÁS S/A, em oito estações ao longo do litoral. O comportamento morfodinâmico distinto de setores do litoral estudado é função do padrão de ondas e direção da linha de costa, morfolQgia da plataforma interna controlando a extensão da zona de surfe e o número de zonas de arrebentação, características dos sedimentos e gradiente da face de pr...

Remote Sensing

Satellite remote sensing is a valuable tool for coastal management, enabling the possibility to repeatedly observe nearshore sandbars. However, a lack of methodological approaches for sandbar detection prevents the wider use of satellite data in sandbar studies. In this paper, a novel fully automated approach to extract nearshore sandbars in high–medium-resolution satellite imagery using a GIS-based algorithm is proposed. The method is composed of a multi-step workflow providing a wide range of data with morphological nearshore characteristics, which include nearshore local relief, extracted sandbars, their crests and shoreline. The proposed processing chain involves a combination of spectral indices, ISODATA unsupervised classification, multi-scale Relative Bathymetric Position Index (RBPI), criteria-based selection operations, spatial statistics and filtering. The algorithm has been tested with 145 dates of PlanetScope and RapidEye imagery using a case study of the complex multipl...

Water

This paper describes a set of experiments undertaken at Universitat Politècnica de Catalunya in the large wave flume of the Maritime Engineering Laboratory. The purpose of this study is to highlight the effects of wave grouping and long-wave shortwave combinations regimes on low frequency generations. An eigen-value decomposition has been performed to discriminate low frequencies. In particular, measured eigen modes, determined through the spectral analysis, have been compared with calculated modes by means of eigen analysis. The low frequencies detection appears to confirm the dependence on groupiness of the modal amplitudes generated in the wave flume. Some evidence of the influence of low frequency waves on runup and transport patterns are shown. In particular, the generation and evolution of secondary bedforms are consistent with energy transferred between the standing wave modes.

Water

Tourism in coastal areas is becoming increasingly important in Integrated Coastal Zone Management (ICZM) as an integrated approach that balances the requirements of different tourist sectors. This paper analyzes ICZM in continental Ecuador and the Galapagos Islands from the perspective of the 3S tourism, and presents its strengths, weaknesses, opportunities and threats (SWOT). The methodology used was based on a literature review of ten aspects of the highest relevance to ICZM, i.e., Policies, Regulations, Responsibilities, Institutions, Strategies and Instruments, Training, Economic Resources, Information, Education for Sustainability, and Citizen Participation. The results highlight four aspects as strengths (Policies, Responsibilities, Institutions and Citizen Participation), while the most notable weaknesses were Regulations and Education for sustainability. Strategies and Instruments, as well as Information, were identified as opportunities to stand out. The main threats were E...

Journal of Marine Science and Engineering

Coastal area constitutes a vulnerable environment and requires special attention to preserve ecosystems and human activities therein. To this aim, many studies have been devoted both in past and recent years to analyzing the main factors affecting coastal vulnerability and susceptibility. Among the most used approaches, the Coastal Vulnerability Index (CVI) accounts for all relevant variables that characterize the coastal environment dealing with: (i) forcing actions (waves, tidal range, sea-level rise, etc.), (ii) morphological characteristics (geomorphology, foreshore slope, dune features, etc.), (iii) socio-economic, ecological and cultural aspects (tourism activities, natural habitats, etc.). Each variable is evaluated at each portion of the investigated coast, and associated with a vulnerability level which usually ranges from 1 (very low vulnerability), to 5 (very high vulnerability). Following a susceptibility/vulnerability analysis of a coastal stretch, specific strategies m...

Journal of Marine Science and Engineering

Through the study of three wreck sites over the Methoni Bay (Greece), this article presents the benefits of spatio-temporal integration and correlation of marine geophysical data in a common three-dimensional (3D) geographical platform for analysis, and visualisation of shipwreck ruins and for interpretation of physical processes over wreck sites. The integration of 3D datasets has been proven to support identification of archaeological features over and under the seafloor, evaluation of the wreck structure state, and assessment on the wrecking event and the wreck site arrangement at that time, due to interactive cross-examination of datasets acquired in separate planes. Data synthesis is fundamental for 3D digital reconstruction of scattered and partially buried shipwreck ruins in complex geology as every dataset acts as interpretive and complimentary to each other. It is also shown that data synthesis highlights the signatures of physical processes over the wreck sites, and the in...

Journal of Marine Science and Engineering

The present study focuses on the long-term multi-year evolution of the shoreline position of the Nha Trang sandy beach. To this end an empirical model which is a combination of longshore and cross-shore models, is used. The Nha Trang beach morphology is driven by a tropical wave climate dominated by seasonal variations and winter monsoon intra-seasonal pulses. The combined model accounts for seasonal shoreline evolution, which is primarily attributed to cross-shore dynamics but fails to represent accretion that occurs during the height of summer under low energy conditions. The reason is in the single equilibrium Dean number Ωeq of the ShoreFor model, one of the components of the combined model. This equilibrium Dean number cannot simultaneously account for the evolution of strong intra-seasonal events (i.e., winter monsoon pulses) and the annual recovery mechanisms associated with swash transport. By assigning a constant value to Ωeq, when the surf similarity parameter is higher th...

Estuaries and Coasts

Surf zones, regions of breaking waves, are at the interface between the shore and coastal ocean. Surf zone hydrodynamics may affect delivery of phytoplankton subsidies to the intertidal zone. Over a month of daily sampling at an intermediate surf zone with bathymetric rip currents and a reflective surf zone, we measured surf zone hydrodynamics and compared concentrations of coastal phytoplankton taxa in the surf zones to concentrations offshore. At the intermediate surf zone,~80% of the variability in the concentration of coastal phytoplankton taxa within the surf zone was explained by their variation offshore; however, concentrations were much higher and lower than those offshore in samples from a bathymetric rip current and over the adjacent shoal, respectively. Hydrodynamics at this intermediate surf zone did not hinder the delivery of coastal phytoplankton to the surf zone, but the bathymetric rip current system appeared to redistribute phytoplankton concentrating them within eddies. At the reflective shore, we sampled surf zones at a beach and two adjacent rocky intertidal sites. Concentrations of typical coastal phytoplankton taxa were usually an order of magnitude or more lower than those offshore, even when offshore samples were collected just 20 m beyond the breakers. The phytoplankton assemblages inside and outside the surf zone often appeared to be disconnected. Surf zone hydrodynamics at the steep, reflective shore coupled with low phytoplankton concentrations in near-surface water appeared to limit delivery of phytoplankton subsidies to the surf zone. Surf zone hydrodynamics may be a key factor in the alongshore variation in phytoplankton subsidies to coastal communities.

Remote Sensing

Increasingly used shore-based video stations enable a high spatiotemporal frequency analysis of shoreline migration. Shoreline detection techniques combined with hydrodynamic conditions enable the creation of digital elevation models (DEMs). However, shoreline elevations are often estimated based on nearshore process empirical equations leading to uncertainties in video-based topography. To achieve high DEM correspondence between both techniques, we assessed video-derived DEMs against LiDAR surveys during low energy conditions. A newly installed video system on a tidal flat in the St. Lawrence Estuary, Atlantic Canada, served as a test case. Shorelines were automatically detected from time-averaged (TIMEX) images using color ratios in low energy conditions synchronously with mobile terrestrial LiDAR during two different surveys. Hydrodynamic (waves and tides) data were recorded in-situ, and established two different cases of water elevation models as a basis for shoreline elevations. DEMs were created and tested against LiDAR. Statistical analysis of shoreline elevations and migrations were made, and morphological variability was assessed between both surveys. Results indicate that the best shoreline elevation model includes both the significant wave height and the mean water level. Low energy conditions and in-situ hydrodynamic measurements made it possible to produce video-derived DEMs virtually as accurate as a LiDAR product, and therefore make an effective tool for coastal managers.

2020

Longshore sediment transport (LST) acts on beach morphodynamics on distinct temporal scales, being fundamental over sediment budget, and, so over the dynamic balance of coastlines. This study determined the most adequate methodology to estimate rates of non-cohesive sediments (from fine sand to gravel) transported by longshore currents, in the surf zone, under different meteoceanographic conditions, at the southern coast of Rio Grande do Sul (RS), Brazil. The methods proposed by CERC (Shore Protection Manual, Coastal Engineering Research Center (CERC), US Army Corps of Engineers Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, 1984), Kamphuis (J Waterw Port Coast Ocean Eng 117(6):624–640, 1991), Bayram et al. (Coast Eng 54:700–710, 2007) and Van Rijn (Coast Eng 90:23–33, 2014) were tested through the comparison with data collected with streamer traps, as well as through statistical tests. Van Rijn (2014) was elected the most suitable approach for all be...

Remote Sensing

Coastal evolution occurs on a wide range of time-scales, from storms, seasonal and inter-annual time-scales to longer-term adaptation to changing environmental conditions. Measuring campaigns typically either measure morphological evolution on a short-time scale (days) with high frequency (hourly) or long-time scales (years) but intermittently (monthly). This leaves an important observational gap that limits morphological variability assessments. Traditional echo sounding measurements on this long time-scale and high-frequency sampling require a significant financial injection. Shore-based video systems with high spatiotemporal resolution can bridge this gap. For the first time, hourly Kalman filtered video-derived bathymetries covering 1.5 years of morphological evolution with an hourly resolution obtained at Porhtowan, UK are presented. Here, the long-term hourly dataset is used and aims to show its added value for, and provide an in-depth, morphological analyses with unprecedente...

APAC 2019, 2019

Systematic monitoring of nearshore area provides useful information on sandy beaches over a wide range of temporal and spatial scales. In this study, accordingly, a simple local remote sensing system is developed to monitor the morphological variations of sandy beaches. This monitoring system consists of acquisition of geo-referenced video image of nearshore area from a small UAV (Unmanned Aerial Vehicle) and subsequent image analysis. Owing to the rapid development of information technology, high resolution photographic images of sea surface can be easily recorded at favorable location in a cost-efficient way. The subsequent quantification of morphological changes is carried out based on bright intensity patterns. First, the video images are converted to successive snapshots and rectified. After removing the small oscillations through semi-automatic identification of Ground Control Points (GCPs), the time-stack images of bright intensity variations are constructed for a series of c...

Acta Oceanologica Sinica, 2016

Beach morphodynamic classifications have achieved extensive acceptance in foreign coastal geomorphological studies. Three beaches located in different zones of a headland-bay coast are classified according to a dimensionless fall parameter, a relative tide range parameter and a dimensionless embayment scaling parameter. Synchronous data, including wave, tide, sediment and beach morphology, are respectively collected from the tangential beach, the transitional beach and the shadow beach of the Shuidong Bay during each spring tide for 16 successive months. The research results indicate that (1) the beach in the tangential zone falls between two major categories which are low tide terrace beaches with rips and barred beaches; the beach in the transitional zone exhibits two main types which are low tide bar/rip beaches and barred dissipative beaches; and the beach in the shadow zone mainly mirrors dissipative states with presence or absence of bars; and (2) the sequential changes and differences of beach states in different coastal zones reflect spatial and temporal variabilities of the headlandbay coast, totally meeting the actual measured beach morphology changes, showing that studies on wavedominated, meso-macrotidal beaches need to consider the influences of the tides. Meanwhile, the research mainly provides a framework about beach state studies, due to different beach states with different erosion patterns, which requires the need to strengthen the researches in this respect, in order to further enrich theoretical basis for a beach topography evolution, beach morphodynamic processes and beach erosion prevention in China.

2021

This paper presents the observed morphological evolution of a multilevel beach cusp system in Long Strand, Co. Cork, Ireland. The surveys were carried out with an Unmanned Aerial Vehicle (UAV) system between March and September 2019. From this site, three levels of beach cusps on the beachface (i.e., lower beach level, mid beach level and upper beach level), and critical cusp parameters are reported, including cusp spacing, cusp elevation, cusp depth, and cusp amplitude. Thus far, such an extensive dataset has not previously been reported in the literature from a single site. The evolution of the different cusp parameters is then linked with the hydrodynamics in the study area, and new prediction theories are proposed for the different cusp parameters. The Lower beach level cusps (1 &lt; z &lt; 2.5 m Irish Transverse Mercator (ITM)) changed with every tide and appeared when surf-similarity parameter-ξ0 &lt; 1.55. These cusps had a mean cusp spacing of λmean = 11.09 m, which are clos...

Journal of Maps, 2017

This paper presents a detailed (1:4000) geomorphological, sedimentological and ecological map of a Mediterranean microtidal wave-dominated beach system and adjacent inner shelf. This map is an innovative cartographic product that integrates a range of processes of present and past timeframes. It is part of a larger cartography on the coastal geomorphology of Sardinia (Italy) aiming to facilitate coastal management practices and future scientific research. The study area is located in SW Sardinia (Italy), and focuses on Porto Pino beach, an important tourist destination of semi-pristine nature, facing environmental pressures common to many coastal Mediterranean settings. In this context, the main human impact on coastal dune habitats is described and a full environmental characterization of the beach system is presented.

Journal of Marine Science and Engineering, 2020

To relate hydrodynamic forcing and topographic response for a tide-dominated sandy beach, extensive field measurements were carried out in the intertidal zone. Hydrodynamics and beach topography were monitored during a total of 12 weeks at two different study sites: one with a featureless intertidal zone and one with intertidal bars. The results of both study sites indicate that the intertidal beach grows when wave steepness is small, whereas it erodes when wave steepness is large. Spring-neap variations in tidal current direction heavily distort this trend: strong spring tidal currents transport sediment away from the beach, resulting in enhanced erosion. Tide-induced beach volume changes are on the same order of magnitude as wave-induced changes. Besides waves and tides, the effect of variations in the amount of sediment supply is substantial, with enhanced accretion when the sediment supply is large. The effect of variations in sediment supply on the intertidal beach topography i...

Journal of Sea Research, 2013

The suprabenthos is considered a major food resource for some fish and birds. Moreover, it plays a key role in the food chain and in nutrient regeneration in the surf zone. The aim of this study was to determine the factors that regulate this fauna and the differences between the suprabenthic groups, to study the possibility of seasonal variations and to compare these results with those of other studies conducted in Europe. A study and geographical comparison was conducted of the temporal patterns of the suprabenthos in the swash zone at two sandy beaches on the NE Atlantic coast (Altar and Ladeira beaches) in the NW of Spain. The study was carried out from September 2005 to August 2007 (24 months). To study the fauna, 60 m 2 was sampled monthly with a suprabenthic sledge, and a total of 101 species belonging to Peracarida and Decapoda were recorded. Total densities ranged from 0.42 ind•m -2 to 178.75 ind•m -2 . Ladeira beach showed higher densities and species richness than Altar beach, and the biocoenosis showed a different dynamic over the 24 months and between years and locations. These results indicate that there is no clear seasonality in the dynamic of suprabenthic species, although the variance of Peracarida orders was explained in diverse degree by environmental variables. The environmental models implemented explained between 27.7% and 93.8% of the faunal data, and hydrodynamic factors and daily global irradiance were selected as the best factors to explain the temporal variations.

Marine Geology, 1987

Antia, E.E., 1987. Preliminary field observations on beach cusp formation and characteristics on tidally and morphodynamically distinct beaches on the Nigerian coast. Mar. Geol., 78: 23-33. Between November, 1984 and December, 1986 observations of cusps were made on some tidally and morphodynamically distinct beaches on the Nigerian coast with a view to assess their origin, conditions for formation, distribution, dimensional and textural characteristics. No conclusive evidence can be forwarded at present with respect to their origin. Nevertheless, after formation, subsequent development and destruction are effected by swash action. Field examination of most of the commonly cited cusp-dependent parameters indicates cusp existence and extinction to be primarily controlled by foreshore slope. Two levels of cusps were typical of the coarse to mediumgrained, reflective and microtidal beaches of Badagry and Victoria. The lower-level cusps were consistently absent on the above beaches when mid-tide level slope exceeded 13 ° and 15 ° , respectively. On the contrary, the fine-grained, mesotidal and largely dissipative beach at Ibeno depicted only a single set of cusps which were consistently extinct on slopes less than 3 °. Cusps were most prevalent during calm coastal condition (November-January) and on foreshore segments depicting reflective beach-state. The regularity of cusp spacing was noted to improve with increase in beach reflectivity. The coarser beaches showed higher cusp relief while cusp length was longer on the fine-grained beach. In general, the spacing, slope, grain-size statistics and permeability of cusps noted in this study conform with those of earlier investigators on other beaches. Temporal changes in dimensional characteristics of cusps are considered essential for evaluating the potentials of cusps as signatures of beach and surf-zone morphodynamics. The above defines the direction of further studies.

Protocolos para o monitoramento de habitats bentônicos costeiros - Rede de Monitoramento de Habitat Bentônicos Costeiros - ReBentos, 2015

Coasts, 2021

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

RBRH, 2019

This work aims to focus on proposals that could stimulate the development of small scale integrated devices for the global challenge to provide electric energy from renewable alternative resources without major interventions. It presents an evaluation of a small-scale wave energy extraction system that can be installed in marine near shore structures, such as fishing piers. The system is characterized by a small oscillating-water-column (OWC) converter composed by tubes tied to the pillars of the structure. A mathematical model of the OWC device was developed. The model relies on two main components. The first uses linear wave theory to describe the water level variation inside the tube as a result of a wave passing by. The second considers the air flux converted to mechanical torque using Wells turbine equations. The simulations were carried out for different water depths and wave parameters, to evaluate the ratio between the input and output energy throughout the year. For the cas...

Natural Hazards, 2020

Rip currents are one of the most significant environmental hazards for beachgoers and are of interest to coastal scientists. Several studies have been conducted to understand rip current dynamics, and several approaches for rip hazard assessment have been proposed. In general, the purpose is to provide knowledge and tools to support authorities and lifeguards in rip current risk prevention. This study proposes the application of an expeditious methodology to evaluate rip current hazard and risk, based on probability theory. The tested area was located along the Alassio beach, a renowned tourist destination located on the western Ligurian coast (NW Italy). A coastal video-monitoring system was used for rip currents individuation, whereas wave data were collected thanks to an oceanographic buoy managed by Regione Liguria. In detail, a yearly analysis was performed to identify the correspondence between rip currents and wave parameters data. The results showed that rip currents occur, ...

Marine Ecology, 2017

The size of bottom-up subsidies, food and larvae, from the ocean has a profound impact on inter-tidal communities and populations. Alongshore variations in subsidies are attributed to variation in coastal conditions, but also might be due to variations in surf-zone hydrodynamics. We tested this hypothesis by comparing surf-zone phytoplankton concentrations to surf-zone hydrodynamics as indicated by the width of the surf zones. To minimize the potential effects of alongshore variation in phytoplankton abundance in the coastal ocean, we sampled closely spaced sites (median separation 1 km) over short periods (3 days). Surf-zone concentrations of coastal phytoplankton taxa (e.g. Chaetoceros spp., Pseudo-nitzschia spp. and dinoflagellates) varied with surfzone width; 65% to 94% of the variability in their concentration is explained by surfzone width. Where surf zones were narrow and more reflective, phytoplankton concentrations were one to several orders of magnitude lower than in wider, more dissipative surf zones. The most closely spaced stations were 30 m apart, but represented distinct habitats-a reflective and a more dissipative surf zone. Phytoplankton concentrations in the reflective surf zone were an order of magnitude or more lower than in the adjacent more dissipative surf zone. A reanalysis of a published study on phytoplankton subsidies found similar results. Alongshore variation in surf-zone hydrodynamics appears to be an important driver of phytoplankton subsidies to the inter-tidal zone.

Brazilian Journal of Oceanography, 2017

Sandy beaches are dynamic ecosystems with strong interaction of sediments, waves and tidal energy, with marked effects on benthic assemblages. Although there are numerous efforts in understanding spatial-temporal variation of benthic macrofauna on sandy beaches along the southern and southeastern Marine Ecoregions in Brazil, there is poor sampling along beaches of the Eastern Marine Ecoregion (EME). Here we examined spatial and temporal scales of variability in benthic macrofauna (&gt; 500 µm) through a hierarchical sampling of two dissipative sandy beaches within the EME between two seasons (winter 2011 and summer 2012). We tested the hypothesis that spatial changes (i.e., meters to hundreds of meters scales) in the structure of benthic assemblages will be more pronounced compared to the weak seasonal fluctuations at this tropical region. We found weak temporal and spatial changes in sediment grain size and beach slope, but differences in macrofaunal assemblages were evident. Contr...

Journal of Marine Science and Engineering, 2020

For observation on the influence mechanism of environmentally and aesthetically friendly artificial submerged sand bars and reefs in a process-based way, a set of experiments was conducted in a 50 m-long flume to reproduce the cross-shore beach morphodynamic process under four irregular wave conditions. The beach behavior is characterized by the scarp (indicating erosion) and the breaker bar (indicating deposition), respectively, and the scarp location can be formulated as a linear equation regarding the natural exponential of the duration time. Overall, main conclusions are: (1) the cross-shore structure of significant wave height and set-up is mainly determined by the artificial reef (AR); (2) the cross-shore distribution of wave skewness, asymmetry, and undertow (indicating shoaling and breaking) is more affected by the artificial submerged sand bar (ASB); (3) the ASB deforms and loses its sand as it attenuates incident waves, which leads to a complex sediment transport pattern; ...

PLOS ONE, 2016

Empirical patterns that emerge from an examination of food webs over gradients of environmental variation can help to predict the implications of anthropogenic disturbance on ecosystems. This "dynamic food web approach" is rarely applied at the coastal margin where aquatic and terrestrial systems are coupled and human development activities are often concentrated. We propose a simple model of ghost crab (Ocypode quadrata) feeding that predicts changing dominant prey (Emerita talpoida, Talorchestia sp., Donax variablis) along a gradient of beach morphology and test this model using a suite of 16 beaches along the Florida, USA coast. Assessment of beaches included quantification of morphological features (width, sediments, slope), macrophyte wrack, macro-invertebrate prey and active ghost crab burrows. Stable isotope analysis of carbon (13 C/ 12 C) and nitrogen (15 N/ 14 N) and the SIAR mixing model were used to determine dietary composition of ghost crabs at each beach. The variation in habitat conditions displayed with increasing beach width was accompanied by quantifiable shifts in ghost crab diet and trophic position. Patterns of ghost crab diet were consistent with differences recorded across the beach width gradient with respect to the availability of preferred micro-habitats of principal macro-invertebrate prey. Values obtained for trophic position also suggests that the generalist ghost crab assembles and augments its diet in fundamentally different ways as habitat morphology varies across a highly dynamic ecosystem. Our results offer support for a functional response in the trophic architecture of a common food web compartment (ghost crabs, macro-invertebrate prey) across well-known beach morphologies. More importantly, our "dynamic food web approach" serves as a basis for evaluating how globally widespread sandy beach ecosystems should respond to a variety of anthropogenic impacts including beach grooming, beach re-nourishment, introduction of non-native or feral predators and human traffic on beaches.

Irish Geography, 1990

Shoreline erosion is an environmental issue in main parts of Ireland. This paper reports on a detailed study of shoreline change al sixteen beach sites from the mouth of Lough Foyle (Magilligan) in Co. Londonderry to Larne in Co. Antrim, a distance of 135km. Apart from a short stretch of coast (c. 4km) around the mouth of the River Bann. the entire coast is receding, although the rales of change and the reasons for such changes vary considerably. The most rapid erosion (up to 3.5 in/year) is occurring on the northwest coast of Mugilligan. probably as part of a lone-term natural adjustment of the shoreline to secular climate and sea-level changes. Elsewhere, average erosion rates are much longer, often less than 0.25 in year, although this rate approaches I m year on those beaches (Cushendall and Cushcndun) that are. or have been, used for sand and gravel extraction. In many places shoreline changes have resulted from human activities, including the building of seawalls, jetties ami piers. At Portrush and Carnlough the beach level has fallen dramatically in front of the seawall. Both inshore dredging and the regulation of cross-shore stream discharge have affected shoreline stability in some areas, for example Portstewart and Ballycastle. Overall the causes ol erosion arc often intermixed, and prediction of future trends is difficult.

Frontiers in Marine Science

Recently, studies have been conducted that long-term changes in shoreline position can be sufficiently interpreted using an ordinary differential equation that includes only erosion and recovery processes. Here, the erosion process term is given as a function of the breaking wave energy, which causes the shoreline to retreat to the ultimate erosion position by the incoming wave energy. The recovery process term is given as a function of the concentration of suspended sediment and allows it to recover to its shoreline position. Therefore, in this study, we propose a numerical technique that simulates long-term changes in the beach profile by extending the ordinary differential equation to be applied to the change in seabed constituting the beach profile by applying the parabolic equation of the equilibrium beach profile of the surf zone. This model also consists of a term that allows the beach profile to converge to the equilibrium beach profile due to the breaking wave energy and an...

Reviews of Geophysics, 2015

2019

Remote Sensing

The creation and protection of surfing breaks along populated coastlines have become a consideration for many councils and governments as surfing breaks are a major driver of tourism. To assess the surf amenity of surfing breaks, a quantitative and objective assessment method is required. A new wave peel tracking (WPT) method has been developed using a shore-based camera to assess surf amenity by measuring and quantifying potential surfing ride rate, length, duration, speed and direction on a wave-by-wave basis. The wave peel (or “curl” below the wave peak) is the optimal surfing region on a wave, and each wave peel track represents a surfable ride. Wave peel regions are identified, classified and tracked using traditional and machine learning-based computer vision techniques. The methodology is validated by comparing the rectified wave peel tracks with GPS-measured tracks from surfers in the wave peel regions. The WPT methodology is evaluated with data from a reef and adjacent natu...

Regional Studies in Marine Science

The concept of Ecological Integrity (EI) refers to the capacity of a place to sustain and maintain the biota in such conditions that allows it to function as a balanced, integrated and adaptive system, and can be derived by comparing present vs. past or spatial reference baseline conditions. Here we assess the EI of Playa El Rivero (34 • 2'29.35"S, 53 • 32'21.14"W) in Punta Del Diablo resort, Uruguay. This 600 m-length, previously unstudied sandy beach is one of the main attractions of the resort, receiving thousands of tourists during summer. Accordingly, conspicuous human impacts are concentrated in the more dissipative end of the beach. In order to derive EI values, a large number of indicators (n=20), including population and community level univariate descriptors for benthic macrofauna, as well as direct indicators of EI (AMBI, M-AMBI and Buckland indices) were assessed and integrated. The distribution of population and community level variables were compared across the along-shore axis with the expected distribution under the Swash Exclusion Hypothesis (SHE) and the Habitat Harshness Hypothesis (HHH), which predict a decrease in richness, biomass and abundance from reflective to dissipative conditions. To derive a global value, an EI value was calculated for population and community levels as well as according to direct impact indicators. EI thus ranged from 1 (no measurable or significant impacts) to 0 (completely dysfunctional system). Integrating all types of indicators, a value of 0.76 was obtained for the beach under study. This value integrates both chronic and putative ''press'' disturbance occurring during the high tourist season in the period under study and suggests a sub-optimal state (ca. 20% reduction) of the health of the system studied, probably related to the sum of chronic anthropogenic impacts that the beach arc presents. This value is considered as an objective (but probably conservative) reference point in order to evaluate the effectiveness of future management measures.

PeerJ

Classification of beaches into morphodynamic states is a common approach in sandy beach studies, due to the influence of natural variables in ecological patterns and processes. The use of remote sensing for identifying beach type and monitoring changes has been commonly applied through multiple methods, which often involve expensive equipment and software processing of images. A previous study on the South African Coast developed a method to classify beaches using conditional tree inferences, based on beach morphological features estimated from public available satellite images, without the need for remote sensing processing, which allowed for a large-scale characterization. However, since the validation of this method has not been tested in other regions, its potential uses as a trans-scalar tool or dependence from local calibrations has not been evaluated. Here, we tested the validity of this method using a 200-km stretch of the Brazilian coast, encompassing a wide gradient of mor...

Climate Change Management, 2020

Over the last decades, the Mediterranean coasts have experienced intense development, mainly due to the growing role of tourism, maritime trade, and energy industry. This situation has favoured a rapid expansion of urban coastal settlements and infrastructures, thus producing negative effects, such as an irreversible reshaping of the littorals, a transformation of their natural resources, and a decrease of their resilience. At present, climate change is worsening this condition by causing modifications on both weather and hydrodynamic processes. In this respect, the past and present impacts of climate change on the morphological stability of the Mediterranean coasts and their effects on tourism have been recently analysed. Data interpretation has shown that the littorals differently respond to this occurrence in relation to their characteristics and to local weather and hydrodynamic conditions. The results have proved that erosion and flooding are two major threats to the preservation of the coasts; they are endangering the beach-based tourism mainly causing land loss and serious damages to human settlements and activities. As in the Mediterranean coasts population is growing and social and economic interests are increasing, the implementation of flood and coastal erosion risk management strategies is necessary to face future challenges related to climate change and to increase coastal resilience. Introduction: Present Conditions of the Mediterranean Coasts Mediterranean coasts are among the most threatened ones in the world. Over the last decades, they have undergone intense development, mainly due to the growing role of tourism and recreational activities, maritime trade, industry, agriculture, and fishing. These conditions have produced a rapid poorly planned urbanization and an overexploitation of coastal resources that have been responsible for a number of negative impacts, such as a remarkable irreversible reshaping of the littorals,

Water Resources Research, 2013

Intertidal zones are spatially complex and temporally dynamic environments. Coastal groundwater discharge, including submarine groundwater discharge, may provide stabilizing conditions for intertidal zone permeable sediments. In this study, we integrated detailed time series temperature observations, porewater pressure measurements, and two-dimensional electrical resistivity tomography profiles to understand the coupled hydraulic-thermal regime of a tropical sandy intertidal zone in a fringing coral reef lagoon (Rarotonga, Cook Islands). We found three heating patterns across the 15 m study transect over tidal and diel periods: (1) a highly variable thermal regime dominated by swash infiltration and changes in saturation state in the upper foreshore with net heat import into the sediment, (2) a groundwater-supported underground stable, cool region just seaward of the intertidal slope break also importing heat into the subsurface, and (3) a zone of seawater recirculation that sustained consistently warm subsurface temperatures that exported heat across the sediment-water interface. Simple calculations suggested thermal conduction as the main heat transport mechanism for the shallow intertidal sediment, but deeper and/or multidimensional groundwater flow was required to explain temperature patterns beyond 20 cm depth. Temperature differences between the distinct hydrodynamic zones of the foreshore site resulted in significant thermal gradients that persisted beyond tidal and diel periods. The thermal buffering of intertidal zones by coastal groundwater systems, both at surface seeps and in the shallow subsurface, can be responsible for thermal refugia for some coastal organisms and hotspots for biogeochemical reactions.

Journal of Marine Science and Engineering, 2021

Long-term (&gt;decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyz...

Journal of Geophysical Research: Earth Surface, 2021

 Ensemble-based simulations of future shoreline evolution to 2100, including sea-level rise driven erosion, are performed and analysed  Future shoreline projections uncertainties are initially controlled by modelling assumptions and after 2060 by sea-level rise uncertainties  The choice of wave-driven equilibrium modelling approach and incident wave chronology are critical to short/mid-term shoreline projections

Coastal Engineering

Coastal communities are currently facing the challenge of climate change and coastal retreat. While scientists are moving towards ensemble-modelling approaches to address uncertainties on shoreline evolution predictions, they rarely account for the stochastic nature of wave conditions across a variety of temporal scales (e.g., daily, weekly, seasonal, and interannual). In this contribution, we investigate the effects of the inherent variability of wave conditions on past and future multi-decadal shoreline evolution at the, cross-shore transport dominated, beach of Truc Vert (France). Using a climate-based wave emulator and variance decomposition method, we address the relative impacts of uncertain wave chronology, sea-level rise and model free parameters on modelled shoreline change, while accounting for possible correlations and interactions among the input variables. This work is done for two different wave-driven equilibrium models. The results show that the equilibrium shoreline models respond differently to the ensemble wave forcing, with strong implications on the long-term variability of modelled shoreline. We find that the modelled shoreline variance is primarily driven by the uncertain wave chronology until mid-21 st century, while the uncertainties on future sea-level rise become dominant after 2060 in all the simulated scenarios. We also found that interactions and correlations among the uncertain variables can affect the estimation of shoreline predictions uncertainties. Finally, we provide a perspective on the application of non-stationary wave-related model parameters as future research avenue for understanding uncertainties in modelled shoreline.

Geographical Research, 2012

A seminal publication by Wright and Thom on coastal morphodynamics followed by a detailed yet expansive range of beach field experiments resulted in the publication of Wright and Short, which presented a fresh morphodynamic approach to the study of beaches. The development of the morphodynamic approach to coastal systems had its origin at Louisiana State University in the 1960-1970s, where Thom, Wright, and Short were students during this period. On their respective returns to Australia in the 1970s, they utilised the vast Australian coastal environment to apply this approach across a wide range of coastal settings and time frames developing the now universal wave-dominated beach model, followed later by tide-modified and tide-dominated beach models, as well as a fresh approach to dunes, barriers, estuaries, and the shoreface. This paper reviews the emergence of the morphodynamic approach in Australia and its subsequent impacts.

Journal of Geophysical Research, 2011

Over 30 years of wave and beach survey data at Collaroy-Narrabeen Beach in southeast Australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross-shore sediment exchange or shoreline rotations due to alongshore exchange between the beach's extremities. Offshore wave data are derived from both buoy measurements and ERA-40 reanalysis data. EOF analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability (60% of variability) is an onshore-offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end. This mode is primarily associated with variability in wave energy/storms, which by the nature of the wave climate of this region chiefly occurs from the south-southeast. The secondary mode of shoreline variability (26% of variability) is a rotational signal between either end of the beach, which coincides with 24% of the offshore wave climate shifting between the south-southeast and east as well as changes in the wave period and wave energy/storms. A distinct annual cycle is identified in this rotation signal. It is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross-shore sediment exchange processes.

Marine Geology, 1985

Data on rip spacing, persistence, and types were collected over 19 months under a wide range of wave conditions on a 3.6-km long beach bordering the Tasman Sea. Results show that rips are typical of moderate-to-high wave conditions on intermediatetype beaches. Rip types include erosion rips associated with rising seas and beach erosion, highly variable in persistence and location, widely-spaced, and increasing in intensity until a fully dissipative state is attained; mega rips (large-scale) topographically-controlled erosion rips; and accretion rips associated with stable or falling wave conditions and beach accretion, less intense and more closelyspaced and more spatially and temporally stable.

Scientific data, 2016

Long-term observational datasets that record and quantify variability, changes and trends in beach morphology at sandy coastlines together with the accompanying wave climate are rare. A monthly beach profile survey program commenced in April 1976 at Narrabeen located on Sydney&#39;s Northern Beaches in southeast Australia is one of just a handful of sites worldwide where on-going and uninterrupted beach monitoring now spans multiple decades. With the Narrabeen survey program reaching its 40-year milestone in April 2016, it is timely that free and unrestricted use of these data be facilitated to support the next advances in beach erosion-recovery modelling. The archived dataset detailed here includes the monthly subaerial profiles, available bathymetry for each survey transect extending seawards to 20 m water depth, and time-series of ocean astronomical tide and inshore wave forcing at 10 m water depths, the latter corresponding to the location of individual survey transects. In addi...

Journal of Ocean Engineering and Marine Energy, 2014

To allow for effective and sustainable coastal management and planning it is important to have the tools available to estimate extreme beach erosion levels. This paper, therefore, presents an evaluation of methods available for quantifying extreme beach erosion. Previous common practice is the use of a single benchmark (1 in N year) event to estimate the corresponding extreme erosion level. The limitations of this approach led to the development of more sophisticated temporal simulation frameworks providing robust statistical quantification of extreme beach erosion. These developments have resulted in a number of follow on studies to progress the methodology in line with a range of coastal morphodynamic modelling approaches. The discussion presented here, begins with basic empirical techniques and progresses up to those conducted using the most up-todate morphodynamic models. Each methodology is applied to Narrabeen Beach, NSW, Australia, to compare and assess their suitability. The development of these methodologies is a relatively new topic, meaning that there is much scope for further progression. Although the use of state-of-the-art morphodynamic models is shown to give a good representation of erosion volumes, their impracticalities seem to outweigh

Earth Surface Processes and Landforms, 2018

The Canary Islands form a volcanic archipelago in which a WE chain of progressively older and less active islands can be observed. In the Canary Islands, unlike most hotspot archipelagos, certain geodynamic peculiarities have promoted longer periods of island survival, exceeding 20 My. This factor makes these islands a suitable context for this work, which aims to analyze extensively the coastal geomorphic structure on islands with different development states. For this, three islands in different volcanic phases were selected: La Palma (1.8 My), Gran Canaria (14.5 My) and Fuerteventura (22.6 My). An ad hoc landform-based hierarchical taxonomy was designed to analyse the coastal geomorphic structure of the three islands. Based on a multi-sourced analysis in GIS and field recognition, a comprehensive cartographic database was collected using the CDS method as a feature abundance proxy. Three different aspects of the geomorphological structure were compared and related between the islands: (i) composition, (ii) abundance and (iii) diversity. Through their comparison, we attempt to explore geomorphological aspects of coastal evolution over geological spatiotemporal scales. Composition was explored analyzing the distribution of the feature's longshore frequencies (p). Abundance, by metrics of Local abundance (N∩) and Whole density (NU). Diversity, through four indices: Normalized Richness (S) and Margalef index (M) to estimate richness; Simpson (D) and Shannon (H') indices to estimate evenness. We identified a systematic transformation in the dominant landform composition and a systematic trend in increasing geomorphological abundance and diversity from younger to older islands. The results show a long-term structural pattern defined by the increase in coastal geomorphic complexity (abundance and diversity) over geological time, as the coasts evolve from predominantly rocky-erosive to increasingly clastic-depositional environments. This This article is protected by copyright. All rights reserved. long-term geomorphological pattern may be a general aspect of hot-spot island archipelagos, which can bring a new perspective to the knowledge of their coastal evolution.

Journal of Marine Science and Engineering

The macrofauna in the intertidal zone of sandy beaches provides the trophic connectivity between land and sea, by linking microbiome, meiofauna, and megafauna, representing a food source for several terrestrial animals, including shorebirds and mammals. However, the macrozoobenthos in urbanised beaches is subjected to intense disturbances, such as breakwater barriers and tourism, which limit or impede the energy transfer from the marine to the terrestrial habitats. Because the information about diversity and abundance of the macrozoobenthos of the intertidal zone on the Mediterranean sandy coasts is scant, the main objective of this study is to increase the knowledge on the macrofauna living in this habitat and to identify taxa sensitive to cumulative human-induced stresses. To achieve this purpose, the structure and dynamics of macrozoobenthic communities from (1) a highly frequented beach characterized by breakwater barriers and (2) a marine protected area (MPA) in the Adriatic Se...

Earth System Science Data, 2018

Assessing the impact of changes on the environment driven by natural or anthropogenic forcers includes the comparison between antecedent and post-event conditions. The latter is particularly relevant in order to better understand to which extent those changes actually impact or alter a particular environment and associated services and to determine the resilience of a system. In this regard, it becomes essential to create or provide databases to inform about baseline conditions. Here, we present a database that integrates surficial sediment samples collected and analysed for textural characterization within the framework of a series of research projects over circa 20 years. Collected samples along the southwestern Atlantic margin of the Iberian Peninsula extend from estuaries and beaches to the adjacent continental shelf. For the case of the more dynamic environments, namely coastal sandy barriers, samples were repeated over time in order to capture the intrinsic variability of the system. Examples of the utility of this data set for a variety of purposes and environments are also included within this paper through three examples. Therefore, here we show the added value of the database as it can be used to assess the impact of a particular event or activity at an estuary by providing baseline conditions, evaluate the continental shelf sediment suitability for nourishment activities, or contribute to the understanding of the morphodynamics and classification of beaches. Finally, it is worth stating the importance of such databases to analyse medium-to long-term variability as the one induced by sea level rise, changes in storminess, or human activities. The open-access data presented here are at

Journal of Marine Science and Engineering

Beach slope is a critical parameter to, e.g., beach safety, wave reflection at the coast and longshore transport rate. However, it is usually considered as a time-invariant and profile-average parameter. Here, we apply a state-of-the-art equilibrium model to hindcast beach slope variability from the time scales of days to years at the high-energy meso-macrotidal sandy beach of Truc Vert, southwest France. We use 9 years of bimonthly beach surveys to compute beach slope time series at different elevations. Results show that beach slope exhibits an equilibrium response with contrasting behaviors along two distinct areas of the beach profile. From 0 to 2 m above mean sea level, which is located under the berm crest, a slope response predominantly at the storm time scale is observed. The beach slope steepens under low energy waves, with the equilibrium model explaining up to 40% of the observed beach slope variability. In contrast, from 2.5 to 4 m above mean sea level, which is above th...

Sedimentology, 1993

Short term variability in delta form and process can be partly explained by the relative strength of hydraulic parameters such as river discharge, discharge variability, wave energy flux and tidal range. However, the calibre or grain size is also important. The amount, mode of transport and grain size of the sediment load delivered to a delta front have a considerable effect on the facies, formative physical processes, related depositional environments and morphology of the deltaic depositional system. The available grain size influences (1) the gradient and channel pattern of the fluvial system on the delta plain; (2) the mixing behaviour of sediment as it discharges into the ambient basin waters at the river mouth; (3) the type of shoreline, whether reflective or dissipative, and its response to both wave energy and tidal regime; and (4) the deformation and resedimentation processes on the subaqueous delta front. Long term aspects of deltaic sedimentation, including a few generalized relationships between sediment supply and physiographic setting, are briefly introduced. The need for further detailed research on modern and ancient deltaic dispersal systems is emphasized, and specific suggestions are given for future research.

Remote Sensing, 2019

Fixed video camera systems are consistently prone to importune motions over time due to either thermal effects or mechanical factors. Even subtle displacements are mostly overlooked or ignored, although they can lead to large geo-rectification errors. This paper describes a simple and efficient method to stabilize an either continuous or sub-sampled image sequence based on feature matching and sub-pixel cross-correlation techniques. The method requires the presence and identification of different land-sub-image regions containing static recognizable features, such as corners or salient points, referred to as keypoints. A Canny edge detector ( C E D ) is used to locate and extract the boundaries of the features. Keypoints are matched against themselves after computing their two-dimensional displacement with respect to a reference frame. Pairs of keypoints are subsequently used as control points to fit a geometric transformation in order to align the whole frame with the reference ima...

Journal of Geophysical Research: Oceans, 2020

We analyze Eulerian and Lagrangian measurements of wave-induced circulation collected during a 3-week field experiment at a high-energy mesotidal barred beach with the presence of a 500-m headland and a submerged reef. Small changes in wave and tide conditions were found to largely impact circulation patterns. Three main regimes were identified depending on offshore wave obliquity: (1) Under shore-normal configuration, the flow was dominated by cross-shore motions, except for moderate waves at low tide, with the presence of a quasi-steady circulation cell on the reef. (2) Under shadowed configuration, an onshore-directed current flowing away from the headland and a weak oscillating eddy were present outside and inside the shadow region, respectively. (3) Under deflection configuration, a deflection rip flowing against the headland and extending well beyond the surf zone was present, with activity maximized around low tide for moderate waves. Under 4-m oblique waves, the deflection rip was active regardless of the tide with mean depth-averaged velocities up to 0.7 m/s 800-m offshore in 12-m depth, with energetic low-frequency fluctuations. Our results emphasize the ability of deflection rips to transport materials far offshore, suggesting that such rips can transport sediment beyond the depth of closure. This study indicates that a wide variety of wave-driven circulation patterns can occur and sometimes coexist on beaches with prominent geological settings. Changes in the dominant driving mechanism can occur as a result of small changes in wave and tide conditions, resulting in more spatially and temporally variable circulation than along open sandy beaches. Plain Language Summary Most field experiments about wave-induced circulation patterns have been conducted along open sandy beaches, while experiments in geologically constrained environments are scarce. We performed intensive field measurements at a high-energy beach with the presence of a 500-m headland and a submerged natural reef. Three main circulation patterns were identified depending on the offshore wave obliquity. For shore-normal waves, cross-shore motions dominated the nearshore region, while oblique wave configurations resulted in more complex horizontal circulation. In particular, under intense headland-directed longshore current, the flow was deflected seaward against the headland. This deflection resulted in an intense seaward flowing jet (deflection rip) extending well beyond the surf zone edge, particularly during storm conditions. Such findings highlight the ability of these deflection rips to dominate water and sediment exchanges between the nearshore and the inner shelf region. Our study further outlines the more spatially and temporally variable circulation patterns occurring along geologically constrained beaches compared to open sandy beaches, ranging from small recirculating cells across the reef to a large deflection rip extending hundreds of meters beyond the surf zone.

Remote Sensing

This paper examines the potential of an optical flow video-based technique to estimate wave-filtered surface currents in the nearshore where wave-breaking induced foam is present. This approach uses the drifting foam, left after the passage of breaking waves, as a quasi-passive tracer and tracks it to estimate the surface water flow. The optical signature associated with sea-swell waves is first removed from the image sequence to avoid capturing propagating waves instead of the desired foam motion. Waves are removed by applying a temporal Fourier low-pass filter to each pixel of the image. The low-pass filtered images are then fed into an optical flow algorithm to estimate the foam displacement and to produce mean velocity fields (i.e., wave-filtered surface currents). We use one week of consecutive 1-Hz sampled frames collected during daylight hours from a single fixed camera located at La Petite Chambre d’Amour beach (Anglet, SW France) under high-energy conditions with significan...

Remote Sensing

Although geologically constrained sandy beaches are ubiquitous along wave-exposed coasts, there is still a limited understanding of their morphological response, particularly under storm conditions, which is mainly due to a critical lack of nearshore bathymetry observations. This paper examines the potential to derive bathymetries from video imagery under challenging wave conditions in order to investigate headland control on morphological beach response. For this purpose, a video-based linear depth inversion algorithm is applied to three consecutive weeks of frames collected during daylight hours from a single fixed camera located at La Petite Chambre d’Amour beach (Anglet, SW France). Video-derived bathymetries are compared against in situ topo-bathymetric surveys carried out at the beginning and end of the field experiment in order to assess the performance of the bathymetric estimates. The results show that the rates of accretion/erosion within the surf zone are strongly influen...

Remote Sensing

Previously, paired spits have been described at the mouths of bays, estuaries, and deltas. This study analyzed the worldwide distribution and morphodynamic patterns of paired spits located at the mouths of interdistributary bays of deltas (three systems) and within coastal channels (24 systems). The methodology was based on the detailed analysis of satellite images, nautical charts, and tidal-range databases. The paired spits found were mainly located on microtidal coasts at high or mid latitudes. Waves were the main factor controlling convergent progradation and breaching of the spits, while the hydraulic blockage for the development of these paired spits was mainly due to tide-induced currents, as well as minor fluvial outlets in the interdistributary bays. Three morphodynamic patterns were identified: (i) stable, with low progradation rates, generally without breaching or degradation of any of the spits; (ii) stationary, with high progradation rates, alternating degradation or br...

Natural Hazards, 2021

Rip currents represent significant hazards to swimmers all around the world. The danger arises when a misinformed swimmer uses an inadequate strategy to escape the rip, such as fighting the current directly. This can lead to fatigue, panic, and in some cases drowning. There exists a range of strategies put forward by experts (both lifeguards and scientists) to escape rip currents. However, these recommendations are based on a limited number of scientific studies and there is still much discrepancy surrounding the best strategy to escape a rip. Thus, here we present a simple, physics-based theoretical model aimed at assessing different escape strategies in terms of their associated ‘energetic cost’ (in work and power) for any given rip current and swimmer’s proficiency level. Many combinations of swimmers and rips are considered, including both idealised and a realistic rip current. Our quantitative results back the common knowledge that swimming against the rip (which is strongly di...

Drones, 2019

This study presents an analysis of shoreline change on reef islands using unmanned aerial vehicle (UAV)-derived orthomosaics and digital surface models (DSMs) collected on Sipadan Island, Sabah, Malaysia, and Sasahura Ite Island, Isabel Province, Solomon Islands. The high resolution of UAV-derived orthomosaics enabled changes in the position of the base of beach to be detected with confidence. The accuracy of the UAV-derived DSMs was assessed against equivalent topographic profiles via root-mean-square error, and found to be &lt;0.21 m in all but one case; this demonstrates the potential for using UAV-derived DSMs to interpret three-dimensional island beach morphology and detect patterns of geomorphic change. The correlation between planimetric and volumetric change along selected beach transects was also investigated and found to be variable, indicating that a multifaceted approach including both planimetric (two-dimensional) and volumetric (three-dimensional) metrics is of value w...

Earth Surface Processes and Landforms, 2016

The results from three years of surveying and monitoring a dynamic foredune and dunefield restoration effort on Vancouver Island, Canada is presented. Complete removal of foredune vegetation occurred in three phases spaced a year apart in an effort to control invasive Ammophila spp. The collection of airborne LiDAR, orthophotographs, and bimonthly topographic surveys provided a means to quantify and examine sediment budgets and geomorphic responses. Three survey swaths, corresponding with each phase of vegetation removal, were established to provide detailed topographic coverage over the impacted beach, foredune, and dunefield landscape units. The swath corresponding with the first phase of removal recorded a positive sediment budget of 1•3 m 3 m À2 after three years. A control swath, with data collected for a year prior and two years following removal, exhibited a distinct pulse of sediment delivery into the dunefield unit with a maximum gain of 0•03 m 3 m À2 pre-removal compared to 0•11 m 3 m À2 post-removal. Vegetation analysis zones, associated with each of the three swaths, demonstrate a range of vegetation responses due to variation in the vegetation removal and subsequent re-invasion or removal methods employed. The first site to be cleared of vegetation, received ongoing invasive re-growth control, and three years following removal vegetation cover dropped from 57% in 2009 to 13% in 2012 (À44%). An adjacent site was cleared of vegetation two years later (only one year of recovery) but experienced rapid Ammophila re-invasion and percent cover changed from 61% in 2009 to 26% in 2012 (À35%). The data presented provides insights for improving the application of sediment budget monitoring in dynamic restorations and discusses the potential for detailed spatial-temporal survey data to improve our understanding of meso-scale landscape morphodynamics following foredune disturbance. Overall, the vegetation removal treatments reduced the extent of invasive grass and increased dunefield mobility and dynamic activity.

Ocean Dynamics, 2014

The occurrence and characteristics of transverse finger bars at Surfers Paradise (Gold Coast, Australia) have been quantified with 4 years of time-exposure video images. These bars are attached to the inner terrace and have an oblique orientation with respect to the coastline. They are observed during 24 % of the study period, in patches up to 15 bars, with an average lifetime of 5 days and a mean wavelength of 32 m. The bars are observed during obliquely incident waves of intermediate heights. Bar crests typically point toward the incoming wave direction, i.e., they are upcurrent oriented. The most frequent beach state when bars

Estuaries and Coasts, 2019

The extent and distribution of benthic geologic habitats on the upper shoreface (from the shoreline extending offshore to > 10-m water depth) was mapped along the 33-km-long Rhode Island south shore (RISS) in 2015-2016 using a combination of highresolution side-scan sonar, seismic reflection profiles, surface sediment samples, and underwater video imagery. Modern (Holocene) sediment is contained largely in the shoreface depositional platform (SDP), the constructional, seaward sloping portion of the upper shoreface extending from the intertidal beach, offshore. The SDP varies in thickness and width along the RISS, with a mean thickness of 0.7 m and a mean width of 260 m. Maximum thickness (< 3 m) and width (750 m) was adjacent to a 1-km-long jetty system, supporting a net easterly longshore sediment transport along the RISS. The distribution and type of sedimentary environments on the uppermost shoreface here is largely related to the antecedent (glacial) geology. No clear correlation exists between decadal-scale shoreline change and the volume of sediment in the SDP, removing a potential metric for modelling shoreline change here and potentially for other glaciated shorefaces. The complex nature of the shoreface along the RISS, with abundant cobble to boulder gravel outcrop, makes the concept of an equilibrium profile here problematic at best.

Continental Shelf Research, 2021

Ripples and small-scale bedforms are ubiquitous in shallow water environments under the combined action of currents and waves. Small scale processes linked to their formation and migration are interconnected with sediment transport at larger scales (e.g. tens of metres to kilometres), both resulting in and being affected by large scale sediment transport and geomorphological evolution. The lower shoreface provides a key link between coasts and continental shelves, but the contribution of ripples and small-scale bedforms to sediment transport in this region has yet to be fully addressed. This work presents a study of sediment dynamic processes on the lower shoreface in the presence of small-scale bedforms. Observations were made during the winter of 2017 on the lower shoreface of Perranporth Beach, which is in the south west of the UK and exposed to Atlantic waves. The analysis of morphological expressions and the variability of ripples under waves, currents and wave-current conditions are assessed. Ripple morphology and associated dynamics are analysed for their potential contribution to the exchange of sediment between the lower and the upper shoreface. In the present study it was observed that even though ripples were evolving depending on the wave-current forcing, little ripple migration was observed due to low wave skewness. The implication is that ripple migration and bedload transport are only a small contribution to onshore sediment transport under low to moderate energy conditions. However, during more energetic conditions, ripples were washed out and the wave skewness increased, resulting in onshore sediment transport under a sheet flow regime. This suggests that ripple formation and migration can have little impact on the crossshore supply of sediment from the lower shoreface to the upper shoreface and that more energetic wave conditions are required to significantly transport sediment towards the beach.

Estuaries and Coasts

Surf zone hydrodynamics influences the delivery of coastal phytoplankton and detritus food subsidies to shore. Variation in surf zone hydrodynamics can cause phytoplankton concentrations to be higher at dissipative than reflective surf zones, altering both the quantity and quality of food for intertidal suspension-feeders. To assess if surf zone-dependent food availability influences suspension-feeder diets, we out-planted Mytilus californianus mussels for a 5-month common garden experiment at sites with dissipative and reflective surf zones at Cape Arago, Oregon. Stable isotopes, gravimetric lipid weights, and fatty acid trophic biomarkers of extracted abductor muscles were used to examine possible diet differences between mussels grown at dissipative and reflective sites. Both δ15N‰ and δ13C‰ values varied significantly between dissipative and reflective surf zone types, but there was no difference in gravimetric lipid weight between surf zone types. The multivariate fatty acid composition of mussels from dissipative and reflective sites differed; mussels at dissipative sites had a higher proportion of fatty acids indicative of diatoms in their diet (e.g., 16:1ω7, 20:5ω3), whereas mussels at reflective sites had a higher proportion of fatty acids indicative of dinoflagellates (e.g., 22:6ω3). Aspects of our stable isotope and fatty acid data suggest trophic subsidies to mussels were influenced by surf zone hydrodynamics.

Coastal Engineering, 2021

Multipurpose Artificial Reefs (MPARs) are structures that may provide aesthetically acceptable coastal protection and improve recreational outcomes. Twenty years after construction of the first MPAR, Narrowneck reef on the Gold Coast of Australia, most of the available literature is still focused on the planning, design and construction of such structures and peer-reviewed publications on their post-construction monitoring, interaction with sediment transport and impacts on coastal morphology are lacking. The aim of this paper is to evaluate how does Narrowneck reef influence the sediment transport, and morphological changes around the anthropogenic structure, two decades after construction. To do so, a combination of ten high spatial resolution topo-bathymetric surveys from the top of the dune to the 10 m depth captured over 21 months and a series of 60 simulations using a calibrated numerical model were used. Our results demonstrate that: although not expected during design or reported in similar structures, sand can bypass the MPAR around its offshore end; under oblique waves, the longshore currents are deflected as they pass the reef, resulting in a shadow zone on the downdrift side where sand deposits; the bar crest tends to be higher on the reef's updrift side compared to downdrift, indicating that the MPAR can act as a store for sediments, as initially designed. Furthermore, the MPAR can act to stabilise the bar as it moves onshore with a downdrift offset of the inner bar as a result of low oblique wave incidence. The results presented here demonstrate that the short-term response to the MPAR twenty years after construction is more closely related to the deflection of longshore currents as they encounter the reef than to the dissipation of wave energy. This is because MPARs are designed to dissipate just enough wave energy so that they can achieve their recreational goal (surfing).

Water, 2017

This paper assesses the morphological storm-event impact, seasonal cycles, trends of wave forcing, and beach's response at the coastal area of Grand Popo, Benin. Three and a half years' worth of data were collected from 2013 to 2016, using a video system calibrated with field data collected during a 10 day experiment. A comparison was carried out with Wavewatch III IOWAGA wave hindcast data. The along-shore-averaged shoreline position exhibited a seasonal pattern, which was related more to the average wave height than the average storm intensity. Storms occur in austral winter (June, July, August, and September). Based on 12 storms, the results revealed that the average storm duration was 1.6 days, with a mean erosion of 3.1 m. The average post-storm beach recovery duration was 15 days, and the average recovery rate was 0.4 m/day. The impact of storms was more or less amplified depending on the eroding and accreting periods of the wave climate. There was an inter-annual eroding trend of about −1.6 m/year, but the causes of this trend could not be explained.

Journal of Marine Science and Engineering, 2019

Although coastal morphology results essentially from underwater sediment transports, the evolution of underwater beach profiles along the diverse coastlines of the world is still poorly documented. Bathymetry inversion from shore-based video cameras set forth a more systematic evaluation and is becoming more commonly used. However, there are limitations to this profiling method that are insufficiently assessed, undermining confidence in operational applications. In this paper, we investigate the daily evolution of a low tide terrace (LTT) in Nha Trang beach, Vietnam, under strong seasonal forcing: from weak wind waves during summer monsoon to moderate waves during winter monsoon. A new error estimation for depth inversion is presented based on tidal evaluation. The method compares video-based estimate and direct measurement of tidal amplitudes to provide a quality criterion. It reveals three types of errors, the main one being a deep water error associated with physical limits-loss of celerity-bathymetry relationship in deep water. This error is dependent on wave period and thus has a strong seasonal pattern in Vietnam. It is generally detrimental to depth inversion where wind waves are dominant (in summer here). On the contrary, the second error type is larger for larger waves and is located at breakpoint, altering wave detection. The last error type is due to nonlinear effects and wave setup in shallow water. After removing the faulty data, we finally present the first reliable three-year time-series of a beach profile in Nha Trang, Vietnam. A main result is the overall stability demonstrated for the LTT beach, with rapid exchange of sediment between the terrace and the upper beach during typhoons, monsoon events or seasonal cycles. These tropical environments may provide faster beach recovery compared with mid-latitude configurations.

Journal of Geophysical Research: Earth Surface, 2012

A morphodynamic model has been applied to explain the characteristics of transverse sandbars observed in the inner surf zone of open beaches. The model describes the feedback between waves, rollers, depth‐averaged currents and bed evolution, so that self‐organized processes can develop. The modeled bar characteristics, i.e. wavelength (30–70 m), crest orientation (up‐current) and the e‐folding growth time (about 12 hr) are in good agreement with those of observed transverse bars at Noordwijk beach, the Netherlands, but modeled migration speeds (tens of meters per day), turn out to be a factor 2 larger than those observed. The wavelength increases with the distance between the shoreline and the peak of the longshore current and the migration speed is correlated with the maximum longshore current. The model also explains why transverse bar formation at Noordwijk occurs for obliquely incident waves of intermediate heights. Realistic positive feedback leading to formation of up‐current ...

Scientific Reports, 2022

Wildfire and post-fire rainfall have resounding effects on hillslope processes and sediment yields of mountainous landscapes. Yet, it remains unclear how fire-flood sequences influence downstream coastal littoral systems. It is timely to examine terrestrial-coastal connections because climate change is increasing the frequency, size, and intensity of wildfires, altering precipitation rates, and accelerating sea-level rise; and these factors can be understood as contrasting accretionary and erosive agents for coastal systems. Here we provide new satellite-derived shoreline measurements of Big Sur, California and show how river sediment discharge significantly influenced shoreline positions during the past several decades. A 2016 wildfire followed by record precipitation increased sediment discharge in the Big Sur River and resulted in almost half of the total river sediment load of the past 50 years (~ 2.2 of ~ 4.8 Mt). Roughly 30% of this river sediment was inferred to be littoral-grade sand and was incorporated into the littoral cell, causing the widest beaches in the 37-year satellite record and spreading downcoast over timescales of years. Hence, the impact of fire-flood events on coastal sediment budgets may be substantial, and these impacts may increase with time considering projected intensification of wildfires and extreme rain events under global warming. Wildfire is an important factor in hillslope erosion and sediment yields of mountainous and forested rivers worldwide 1,2. Fires liberate soil materials from hillslopes through dry ravel, inhibit rainwater infiltration of soils, and increase the likelihood of soil erosion during subsequent rainfall, all of which increase sediment transport to and through rivers. Yet not all wildfires induce similar geomorphic responses. Factors that control post-fire responses include soil burn severity, basin slope, post-fire rainfall intensities and timing, and downslope floodplain morphology 1-4. Climate change is increasing the size, intensity, and frequency of wildfires throughout the world 5,6 , while concurrently increasing the likelihood for extreme rainfall such that burned areas are at greater risk of experiencing rain intensities exceeding thresholds for debris flow and other sediment mobilization processes 7-9. These evolving conditions are expected to increase fire-related sediment yields and alter downstream riparian habitats in the future 10-12. Although there is increased understanding of the role of wildfire in terrestrial and fluvial systems, little is known about wildfire's role on downstream coastal landforms. Several challenges exist in linking upslope processes to coastal morphodynamics, including the infrequent nature of wildfire (recurrences are historically 10-100 years, although frequency is expected to increase in warmer climates 1,5,12), the complexities and variability of sediment transport through wildfire-affected landscapes 1,3,13-15 , the inherent variability of beach widths due to oceanic processes 16 , and the general scarcity of shoreline position and beach topographic monitoring to determine coastal effects 17,18. Although both geologic records and the coastal waters, sediments, and ecosystems near burned watersheds provide evidence that wildfires influence sediment delivery to the coast 19-22 , there is no general geomorphic understanding about the role of periodic sediment production from wildfire on coastal landforms. Coastal landforms throughout the world are encountering multiple stressors such as accelerating sea-level rise and modified sediment budgets 23-26. Thus, a better understanding of fluvial sediment inputs to beaches, marshes, deltas, and other coastal landforms is needed 27-30. Wildfire is not the only factor influencing fluvial sediment discharge to the coast. Other human impacts such as agricultural development and dam construction have modified rates and characteristics of fluvial sediment discharge for decades to millennia, and coastal impacts from these changes are especially evident in the world's larger deltas 24,27,31-35. However, as wildfire can dictate watershed sediment discharge, particularly for small, steep coastal watersheds 1,4,12 , it deserves more attention with respect to coastal sediment budgets and the future vulnerability of coastal landforms. The development of

2022

Ongoing sea-level rise has brought renewed focus on terrestrial sediment supply to the coast because of its strong influence on whether and how long beaches, marshes and other coastal landforms may persist into the future. Here, we summarise findings of sediment discharge from several coastal rivers, revealing that infrequent, large-magnitude events have disproportionate influence on the morphodynamics of coastal landforms and littoral cells. These eventdominated effects are most pronounced for small, steep mountainous rivers that supply beach and wetland sediment along the world's active tectonic margins, although infrequent events are important drivers of sediment discharge for rivers worldwide. Additionally, extreme events (recurrence intervals of decades to centuries) that follow wildfires, earthquakes, volcanic eruptions, extreme precipitation ormost notablycombinations of these factors can redefine coastal sediment budgets and morphology. Some of these extreme events (e.g., wildfires plus rainfall) are increasing in magnitude and frequency under modern climate warming, with the likely result of increasing sediment flux to affected coastlines. Climate change is also altering watershed processes in both high latitudes and high altitudes, resulting in increased sediment supply to downstream catchments. We conclude that sediment inputs to coastal systems are highly variable with time, and that the variability and trends in sediment input are as important to characterise as long-term averages. Impact statement The future of the world's coasts will be influenced by ongoing sea-level rise and forthcoming storms, which will combine to increase the likelihood for coastal flooding and erosion. However, many coastal settings receive natural supplies of sediment from adjacent rivers and landscapes, and these sediments can physically build up coastal landforms and reduce the potential for erosion and flooding. It is very important to better understand sediment delivery to the coast, as this is one of the key factors in assessing coastal climate change impacts. The delivery of new sediment to the coast commonly has long intervals with very little sediment discharged punctuated by brief events with tremendous sediment discharge. These sediment input events are generally caused by disturbances in the landscape, which can include wildfires, earthquakes, heavy rainfall, volcanic eruptions and human impacts. Over decades to centuries, infrequent, high-magnitude sediment input events can be responsible for most of the sediment that exists along the coast. Climate change has the potential to increase sediment discharge to some coastal settings because of its imminent effects on wildfire, heavy rainfall and the extent of frozen areas within high altitudes and in polar regions. Because of this, there is an increased need to understand the amount of sediment input to coastal regions both now and in the future. Teams of scientists will be needed to monitor and predict future sediment inputs with an eye on better understanding how the coast will respond to climate change.

Scientific Reports

Shoreline position is a key parameter of a beach state, often used as a descriptor of the response of the system to changes in external forcing, such as sea-level rise. Changes in shoreline position are the result of coupled hydrodynamic and morphodynamic processes happening in the nearshore and acting at different temporal scales. Due to this complexity, methodologies aimed at reproducing shoreline evolution at decadal time scale require many simplifications. Simpler methods usually consider an equilibrium beach profile whose shape depends only on beach morphology, and whose location varies depending on incoming forcing. Here, we derive a general equation for shoreline evolution using equilibrium beach profiles. We particularize it based on several common assumptions, and evaluate changes on shoreline position caused by sea-level rise, combined with simultaneous wave and high-frequency sea-level forcing. We compare our model against other analytical equilibrium beach profile-based ...

Journal of Marine Science and Engineering, 2017

Understanding the role of beach morphology in controlling wave overtopping volume will further minimise uncertainties in flood risk assessments at coastal locations defended by engineered structures worldwide. XBeach is used to model wave overtopping volume for a 1:200 year joint probability distribution of waves and water levels with measured, pre-and post-storm beach profiles. The simulation with measured bathymetry is repeated with and without morphological evolution enabled during the modelled storm event. This research assesses the role of morphology in controlling wave overtopping volumes for hazardous events that meet the typical design level of coastal defence structures. Results show that disabling storm-driven morphology under-represents modelled wave overtopping volumes by up to 39% under high H s conditions and has a greater impact on the wave overtopping rate than the variability applied within the boundary conditions due to the range of wave-water level combinations that meet the 1:200 year joint probability criterion. Accounting for morphology in flood modelling is therefore critical for accurately predicting wave overtopping volumes and the resulting flood hazard and to assess economic losses.

Physical Oceanography, 2011

Beach morphology relates the mutual adjustment between topography and fluid dynamics. The morphological makeup of beach systems is not accidental because the arrangement and association of forms occur in an organized contextual space and time. Since the classification derived by Wright and Short (1983) obtained from the analysis of the evolution in a number of Southern Tamilnadu beach sites, beach systems are comprehended in terms of three-dimensional morphodynamic models that include quantitative parameters (wave breaking height, sediment fall velocity, wave period and beach slope) and boundary conditions for definable form-processes association (e.g. presence or absence of bars as well as its type). This has lead to the classification of beaches into three main categories relating the beach state observations with the physical forcing (Short, 1999) dissipative, intermediate (from the intermediate-dissipative domain to the intermediate-reflective domain) and reflective modes. Morphodynamic classification of beach types was based on the equations of Wright & Short (1984) (Dimensionless fall velocity-Dean Parameter).

Chemistry and Ecology, 2020

This paper reports the results of an integrated atmospheric and wave run-up forecasting system, validated with in situ measured data, for the coastal site of Bagnoli, inside the Gulf of Pozzuoli, in the Thyrrenian Sea. A modelling chain consisting of Weather Research and Forecasting model, Wave Watch 3 model and a runup calculator was used to obtain the Ru 2% levels on the beach of Bagnoli, in the framework of the rehabilitation project of the industrial site. Hindcasted waves were validated with observed ones in intermediate depth, while run-up excursions were validated using video-monitoring system located on the beach. The run-up observations were obtained by time stack images analysed using video-monitoring system. An error compensation algorithm was implemented for the correction of the systematic deviations from the DGPS more precise measurements. Among the different schemes chosen for wave run-up prediction, the one of Stockdon et al. [Empirical parameterization of setup, swash, and runup. Coast Eng. 2006;53(7):573-588] was found to be outperforming in matching with the observed run-up levels. This result was expected because of the structure of this formula, which takes into account both the setup and swash run-up contributions.

Ocean Modelling, 2021

Short waves are of key importance for nearshore dynamics, particularly under storms, where they contribute to extreme water levels and drive large morphological changes. Therefore, it is crucial to model accurately the propagation and dissipation of storm waves in the nearshore area. In this paper, field observations collected in contrasted environments and conditions are combined with predictions from a third-generation spectral wave model to evaluate four formulations of wave energy dissipation by depth-induced breaking. The results reveal a substantial over-dissipation of incident wave energy occurring over the continental shelf, resulting in a negative bias on significant wave height reaching up to 50%. To overcome this problem, a breaking coefficient dependent of the local bottom slope is introduced within depth-induced breaking models in order to account for the varying degrees of saturation naturally found in breaking and broken waves. This approach strongly reduces the negative bias observed in the shoreface compared to default parameterizations, yielding significant improvements in the prediction of storm waves. Among the implications of this study, our new parameterization of the breaking coefficient results in systematically increased predictions of the wave setup near the shoreline compared to the default parameterization. This increase reaches a factor 2 for gently sloping beaches.

Coasts

This study investigates the shoreline dynamics of a Caribbean reef-lined beach by utilizing a long-term satellite dataset spanning 75 years and a short-term, high-frequency dataset captured by a fixed camera over 3 years. An array of statistical methods, including ARIMA models, are employed to examine the impact of storms and potential cyclical influences on the shoreline dynamics. The findings indicate that significant storm events trigger a substantial retreat of the vegetation limit, followed by a slow recovery. Given the current frequency of such major events, complete recovery may take several decades, resulting in a minor influence of cyclones on the long-term erosion trend, which remains moderate. The short-term shoreline evolution is primarily driven by the annual cyclicity of the still water level, which generates an annual oscillation—an insight not previously reported. In the context of climate change, alterations to sea-level rise and cyclone frequency could disrupt the ...

Journal of Maps, 2016

The aim of this study is to present a new morphodynamic map (1:10,000 scale) of a wavedominated sector of a Mediterranean ria-type coast (NE Sardinia, Italy). The area has been studied since 1995 with respect to its geomorphological and sedimentological processes. Our map is produced using topographic-bathymetric, textural and compositional data collected during different surveys conducted from 1995 to 2014. The Main Map shows forms, processes and deposits of the coastal belt, as well as the main geological outcrops, structural elements and the areal distribution of seagrass, mainly Posidonia oceanica (L.) Delile and Caulerpa prolifera (Forsskaal) Lamouroux. The map is useful for beach management purposes. It is noteworthy that the role of P. oceanica in the littoral area is twofold: (1) acts as a barrier to siliciclastic material from the backshore; and (2) a producer of biogenic/bioclastic sediment. Based on side-scan sonar images, the P. oceanica meadow appears to be threatened by direct mechanical damage caused by boat anchoring and mooring activities. The human impact on dune habitats has also been recognized and is related to pedestrian and vehicular transit, boat storage and infrastructure for bathing.

Geophysical Research Letters, 2021

The existing theory for shore‐transverse rhythmic sand bars relies on morphodynamic instabilities involving the wave‐driven longshore current and rip currents. Intriguingly, transverse finger bars are common on coasts with sediment excess, something not related to those currents. Here we show that, if the actual beach profile is above the equilibrium profile, cross‐shore transport can induce an instability triggered by onshore transport together with wave refraction by the emerging bars. We use a numerical model that filters out the dynamics associated to longshore and rip currents but includes a simplified version of cross‐shore transport and is able to reproduce the formation of shore‐transverse bars. The alongshore spacing scales with the wavelength of the incident waves and the cross‐shore extent is approximately equal to the distance from shore to the depth of closure. The modeled bars compare qualitatively well with observations at El Trabucador back‐barrier beach (Ebro delta,...

Natural Hazards and Earth System Sciences, 2022

The majority of drowning deaths on Australian beaches occur significant distances away from lifeguard services. This study uses results of 459 surveys of beachgoers at five beaches unpatrolled by lifeguards in New South Wales, Australia, to improve understanding of who visits these beaches and why, and to identify risk factors associated with their beach safety knowledge and behaviour. Many unpatrolled beach users were infrequent beachgoers (64.9 %) with poor rip current hazard identification skills, who did not observe safety signage that was present, and yet intended to enter the water to swim (85.6 %) despite being aware that no lifeguards were present. The survey found that the main reasons why beachgoers visited unpatrolled beaches were because they were conveniently close to their holiday accommodation, or they represented a quieter location away from crowds. Future beach safety interventions in Australia need to extend beyond the standard "swim between the flags" message in recognition that many Australian beaches will remain unpatrolled, yet still frequented, for the foreseeable future. Future beach safety interventions for unpatrolled beaches should be tailored towards the varied demographic groups of beach users. Author contributions. LU, MDH, RWB conceptualized the research and developed the survey. LU, WK, RWB conducted survey fieldwork. LU was responsible for data curation, investigation, and, together with WK, conducted formal data analysis. LU created the figures and the original draft that were reviewed and edited by WK, JCL, MDH, and RWB. RWB supervised the study.

Journal of the Royal Society, Interface / the Royal Society, 2015

Biophysical feedbacks between vegetation and sediment are important for forming and modifying landscape features and their ecosystem services. These feedbacks are especially important where landscape features differ in their provision of ecosystem services. For example, the shape of coastal foredunes, a product of both physical and biological forces, determines their ability to protect communities from rising seas and changing patterns of storminess. Here we assessed how sand supply and changes in vegetation over interannual (3 year) and decadal (21 year) scales influenced foredune shape along 100 km of coastline in the US Pacific Northwest. Across 21 years, vegetation switched from one congeneric non-native beachgrass to another (Ammophila arenaria to A. breviligulata) while sand supply rates were positive. At interannual timescales, sand supply rates explained the majority of change in foredune height (64-69%) and width (56-80%). However, at decadal scales, change in vegetation ex...

Scientific Reports, 2014

The paper is devoted to the analysis of the shape of the swash edge line. Formation of the swash boundary is treated as an interfacial phenomenon. The simplest quantitative characteristic of the roughness of interface is its width w, defined as the root-mean-square fluctuation around the average position. For rough interfaces, the scaling with size of the system L is observed in the form w(L) / L f . The concept of scaling supplies a simple framework for classifying interfaces. It is suggested that the fine structure of the swash boundary results from the combined action of the pinning force applied by random defects of the beach and elasticity of distorted swash boundary. The roughness of the swash front was studied at the Mediterranean Sea coast for uprush and backwash flows. Value of exponent f for receding swash front line was 0.64 6 0.02, when in the case of advancing swash the value 0.73 6 0.03 was calculated. The scaling exponent established for the receding phase of the swash is very close to the values of the exponent established for the roughness of the triple line for water droplets deposited on rough surfaces, crack propagation front in Plexiglas, and for the motion of a magnetic domain walls. T he physics of swash, i.e. a layer of water that washes up on the beach after an incoming wave has broken, is complicated and intriguing. It includes perplexing hydrodynamic and sediment transport events 1-4 . The coastal strip is a highly dynamic zone and may include features with the dimensions ranging from microns to kilometers. Beach cusps are often arising in the swash zone presenting obstacles to the propagation of a wave front and promoting its breakdown 1-4 . In our paper, we address the roughness of the moving swash boundary at which a beach, water and air meet. The roughness of the swash edge is characterized by a scaling law that relates the statistical width w of the boundary (i.e. the root-mean-square fluctuation of the edge line around its average position) to its length L via w(L) / L f law 5-10 . We treat the behavior of this boundary as an interfacial phenomenon, without going into details of the formation of edge waves and beach cusps, covered broadly in literature 1-4 . This ''crude'' approach turns out to be productive and reveals the resemblance of the swash line to a broad diversity of effects arising from the random pinning of moving boundaries . Swash consists of two phases: uprush (onshore flow) and backwash (offshore flow). We concentrate mainly on backwash (offshore flow), when water recedes along the beach face. The receding water front is pinned by randomly distributed obstacles, produced by the beach and constituting the roughness of the swash edge line. It is plausible to suggest that the fine structure of the swash edge line results from the combined action of the pinning force applied by defects of the beach and the elasticity of the distorted swash boundary. The problem is common for a number of physical systems comprising interfaces moving in a disordered medium; for example, self-affine crack propagation 5-6 , wet front propagation and movement of interfaces between immiscible liquids in porous media , height distribution of growing surfaces , and growth of magnetic domain walls in disordered media 12 . However, the most investigated situation of interfaces moving over a disordered system of obstacles is the displacement of the triple (three-phase) line at which water, vapor and a rough (or chemically heterogeneous) surface meet . The shape of a triple line disturbed by the presence of random heterogeneities on the solid surface may be derived by a solution of the Laplace equation with the boundary conditions of the Young equation. With some simplifications, this is given by Shanahan 18 and de Gennes 19 . The simplest quantitative characteristic of an interface is its width w, defined as the root-mean-square fluctuation around an average position. For rough interfaces, scaling with size of a system L is observed, which is expressed in the form meaning that the average width w grows as the size L is increased. The concept of scaling introduced in the field of interfaces by Family and Vicsek 20,21 gave a simple framework for classifying interfaces in various processes. Scaling