bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTS OF WAVE BREAKING AND BEACH SLOPE ON TOE SCOUR IN FRONT OF A VERTICAL SEAWALL
Authors: Zou Qingping , Peng Zhong , Lin Pengzhi
Published: December 2012

Scour in front of coastal structures is a major threat to structural stability and safety of properties behind. In this study, a Reynolds Averaged Navier-Stokes Solver (RANS) is combined with a Volume of Fluid (VOF) (RANS-VOF) surface capturing scheme to investigate the wave interactions with a Seawall and its adjacent sea bed. The main objective is to investigate the effects of wave breaking and beach slope on toe scour in front of a vertical wall.
INVESTIGATING THE RECESSION PROCESS OF COMPLEX SOFT CLIFF COASTS: AN ISLE OF WIGHT CASE STUDY
Authors: Carpenter Natasha Elizabeth , Stuiver Caroline , Nicholls Robert , Powrie William , Walkden Mike
Published: December 2012

Understanding future retreat rates of soft rock cliffs is important for a range of coastal management activities, particularly when considering the impacts of climate change. One key method is process-based numerical modeling. However, this technique is still in its early stages and consequently the process of cliff recession is typically over-simplified. This paper reviews the application of the SCAPE (Soft Cliff and Platform Erosion Model) to a varied geological frontage on the south west coast of the Isle of Wight. Evaluation of the 2D model has been undertaken through validation of the output model profiles compared with measured and field data observations. The results have identified the importance of vertical variations in rock strength within the cliff system, which has a strong influence on recession rates, cliff morphology and the development of emergent features. Evaluation of the model has also highlighted the importance of translating cliff base retreat into an appropriate cliff top position, which defines the extent of the erosion hazards, and hence is of more practical use (e.g., land-use planning). This requires more consideration of the role of terrestrial processes within the cliff recession process.
STATISTICAL PREDICTION OF COASTAL AND ESTUARINE EVOLUTION
Authors: Magar Vanesa , Gross Markus S. , Probert George , Reeve Dominic E. , Cai Yuzhi
Published: December 2012

This paper presents a novel data-driven methodology based on empirical orthogonal teleconnections (EOTs) to analyse and forecast the evolution of coastal navigational channels near the mouth of the Exe estuary, UK. This is the first time EOTs are used in coastal morphodynamics. Therefore, particular emphasis is placed on the comparison of EOTs with the well established empirical orthogonal functions (EOFs) method. EOTs and EOFs are used with a series of 14 surveys, taken approximately every 8 months, covering the period between January 2001 and February 2010. The skill of the methods in producing accurate bathymetric one-step forecasts for February 2010 is analyzed and compared with one-step forecasts based on the raw data. It is found that, provided the order of the autoregressive forecast method is chosen appropriately, EOTs and EOFs are better than the raw data and EOTs outperforms than EOFs. This is attributed to the fact that EOTs, without the orthonormality restriction for the temporal eigenfunctions required in EOFs, capturing the temporal patterns within the data more accurately than EOFs.
CHRONIC BEACH EROSION INDUCED BY COASTAL STRUCTURES IN CHELEM, YUCATÁN
Authors: Lira-Pantoja María Alejandra , Torres-Freyermuth Alec , Appendini Christian Mario , Fernández Diana Carolina , Salles Paulo , Mendoza Ernesto Tonatiuh , López José , Pedrozo-Acuña Adrián
Published: December 2012

The Yucatan coastline has been experiencing beach erosion during the past few decades; the erosion has reached critical points at some locations such as the Chelem beach, located near the Progreso Pier. Despite this problem, only few studies have been devoted in order to investigate the role of coastal structures on explaining the high erosion rates reported at this location. Therefore, the aim of this work is to evaluate the effects of the Progreso Pier on the wave transformation and alongshore sediment transport in the study area. Field surveys were conducted in a monthly basis in order to estimate the erosion rates and wave conditions with an ADCP installed at 8 m water depth. The field information confirmed the high erosional trends (O(1)m/year) that explain coastal infrastructure damage and property losses. The wave measurements were employed as the forcing of a wind-wave numerical model (MIKE 21 SW). The numerical model is implemented in the study area for two different scenarios, with and without the pier; this was to estimate nearshore wave conditions. Subsequently, the nearshore wave climate at 5 m water depth is employed for the calculation of alongshore sediment transport rates in 5 points that are representative of the littoral drift along the study area. The modeling results show that the pier acts as a large scale wave-sheltering structure that induces important alongshore sediment transport gradients under mean wave conditions, decreasing the capacity of the waves to recover the beach. On the other hand, during winter storms, when the direction of the waves is from the NNW, the structure does not seem to play an important role on wave transformation into the study. As a result, the Progreso Pier enhances beach erosion in the Chelem area by inducing algonshore gradients in sediment transport and decreasing the beach recovery capability
PILOT PROJECT SAND GROYNES DELFLAND COAST
Authors: Hoekstra Roderik , Walstra Dirk-Jan R. , Swinkels Cilia S.
Published: December 2012

In October and November 2009 a pilot project has been executed at the Delfland Coast in the Netherlands, constructing three small sandy headlands called Sand Groynes. Sand Groynes are nourished from the shore in seaward direction and anticipated to redistribute in the alongshore due to the impact of waves and currents to create the sediment buffer in the upper shoreface. The results presented in this paper intend to contribute to the assessment of Sand Groynes as a commonly applied nourishment method to maintain sandy coastlines. The morphological evolution of the Sand Groynes has been monitored by regularly conducting bathymetry surveys, resulting in a series of available bathymetry surveys. It is observed that the Sand Groynes have been redistributed in the alongshore, mainly in northward direction driven by dominant southwesterly wave conditions. Furthermore, data analysis suggests that Sand Groynes have a trapping capacity for alongshore supplied sand originating from upstream located Sand Groynes. A Delft3D numerical model has been set up to verify whether the morphological evolution of Sand Groynes can be properly hindcasted. Although the model has been set up in 2DH mode, hindcast results show good agreement with the morphological evolution of Sand Groynes based on field data. Trends of alongshore redistribution of Sand Groynes are well reproduced. Still the model performance could be improved, for instance by implementation of 3D velocity patterns and by a more accurate schematization of sediment characteristics.
MODELING BEACH PROFILE EVOLUTION - A STATISTICAL-PROCESS BASED APPROACH
Authors: Pender Douglas , Karunarathna Harshinie
Published: December 2012

This paper presents a new combined statistical-process based approach for modeling storm driven, cross-shore beach profile response. The approach discussed here involves combining detailed statistical modeling of offshore storm data and a process based morphodynamic model (XBeach), to assess the medium to long-term morphodynamic response of cross-shore beach profiles. Up until now the use of process-based models has been curtailed at the storm event timescale. This approach allows inclusion of the post-storm recovery, in addition to individual event impacts, thus allowing longer-term predictions. The calibration of XBeach for modeling, both, storm induced erosion and post- storm recovery, taking Narrabeen Beach, NSW, Australia as a case study; and the approach used to combine XBeach with the statistical framework to develop the approach are discussed.
LONG-TERM PREDICTION OF BEACH PROFILE AND SEDIMENT GRAIN SIZE CHARACTERISTIC AT LOW ENERGY BEACH
Authors: Tsujimoto Gozo , Tamai Masahiro , Yamada Fumihiko
Published: December 2012

Artificial sandy beach profiles and vertical distributions of sediment grain size were measured monthly along two cross-shore lines at Azure Maiko Beach for 2 years. All measured profiles and vertical distributions are approximated using quadratic profiles. To interpret temporal variations of these profiles, six parameters are introduced. Principle component analysis was applied to evolution of the six parameters to detect major variation modes. Relationships between the detected modes and external forces, wave height and tidal level are expressed using multiple linear regression analysis. The first mode was found to be caused by tidal oscillations and the second by energetic wave motions. Long-term prediction of the modes is examined using these regression results.
GRAVEL BEACH PROFILE EVOLUTION IN WAVE AND TIDAL ENVIRONMENTS
Authors: Jamal Mohamad Hidayat , Simmonds David J. , Magar Vanesa
Published: December 2012

This paper reports progress made in modifying and applying the X-Beach code to predict and explain the observed behaviour of coarse grained beaches. In a previous study a comparison of beach profile evolution measured during large scale experiments under constant water level with numerical model simulations was made. This placed particular emphasis on the tendency for onshore transport and profile steepening during calm conditions (Jamal et al., 2010). The present paper extends that investigation to study the influence of the advection of surf processes induced by tidal water level variations effects, on gravel beach profile evolution. The parameter values and numerical model used in the simulation is similar to that presented previously. It is assumed that, to good approximation, the groundwater interface inside the beach follows the tidally modulated water level. The results obtained from the model shows that the model provides reasonable simulations of beach profile change in a tidal environment. In comparison with simulations under stationary water levels, a larger berm is produced in agreement with literature. Finally, good agreement is obtained between the model simulations and an example of field observations from a beach at Milford on Sea, UK. Further developments are outlined for future work.
A MODEL OF BEACH PROFILE EVOLUTION INCLUDING WAVE-UNDERTOW INTERACTION
Authors: Zhang Chi , Zheng Jinhai , Sui Titi , Demirbilek Zeki , Lin Lihwa
Published: December 2012

A numerical model of beach profile evolution is developed to study the onshore and offshore sandbar migration under different wave conditions. The integrated model consists of wave model, roller model, flow model, sediment transport model and bed evolution model. In particular, the interaction between waves and wave-induced undertow current is considered in the flow model. This is achieved by adding a mean pressure gradient term into the firs-order momentum balance equation of flow. A simple empirical method is also introduced to describe the variation in eddy viscosity during one wave cycle. A preliminary application of the present model shows good agreements of both onshore and offshore sandbar migration phenomenon with the laboratory observation. It is found that the offshore sandbar migration is dominated by undertow while wave affects the transport rate. For the onshore sandbar migration, although sediment transport is mainly driven by wave and the undertow is weak, the transport pattern is considerably modified by undertow. It is shown that the combined effects of wave and undertow are important in beach profile evolution.
INFLUENCES OF CLIMATE CHANGE ON BEACH PROFILE
Authors: Hayashi Kentaro , Mori Nobuhito , Mase Hajime , Kuriyama Yoshiaki , Kobayashi Nobuhisa
Published: December 2012

The influences of climate change due to global warming have been estimated on not only sea level rise but also wave characteristics such as height or energy flux. In this study, the characteristics of medium and long term beach profile change is investigated based on the observed beach profile data at HORS for past 24 years and the relationship between the wave characteristics observed at Kashima port and the climate indexes. In order to estimate the influences of the medium and long term wave characteristic change, a theory is introduced based on equilibrium beach profile with wave parameter, which is theoretically based on sediment characteristic. Moreover, the validation of the theory is evaluated based on the observed beach profile data and wave data.
AN ANALYSIS OF CROSS-SHORE PROFILE EVOLUTION OF A SAND AND A COMPOSITE SAND-GRAVEL BEACHES
Authors: Karunarathna Harshinie , Horrillo-Caraballo Jose , Ranasinghe Roshanka , Short Andrew , Reeve Dominic
Published: December 2012

In this paper, cross-shore morphodynamic evolution of a sand and sand-gravel composite beach, are compared and contrasted used historic surveys of beach profiles. The differential behavior of cross-shore morphodynamics at a range of time scales covering event-scale dynamics up to intra-annual scale variability are investigated and discussed. The application of equilibrium concept to both beach types is explored through Dean's equilibrium profile and Vellinga's beach erosion profile. Variability of cross-shore profile dynamics are quantified and discussed through bulk statistical analysis. Multi-scale morphodynamic trends are determined using Empirical Orthogonal Eigenfunction (EOF) analysis. The above analysis enables to recognise failure mechanism of each beach type during a storm.
COMPARISON OF SEDIMENT TRANSPORT MODELS WITH IN-SITU SAND FLUX MEASUREMENTS AND BEACH MORPHODYNAMIC EVOLUTION
Authors: Cartier Adrien , Larroudé Philippe , Héquette Arnaud
Published: December 2012

The aim of this study is to set up a procedure of linking of three codes to be able to simulate realistic coastal sediment transport and associated morphological change. In order to calibrate sediment transport formulae, comparisons of our simulations were carried out with in-situ data of sand transport measured on macrotidal beaches of northern France on the shore of the English Channel and Dover Strait. This technique of simulation was then used to compare and investigate the efficiency of several sediment transport models on the site of Sète (microtidal beach on the Mediterranean coast) during two storms events.
SAND TRANSPORT IN THE SWASH ZONE IN LOW-ENERGY WAVE CONDITIONS
Authors: Silva Paulo Alves , Abreu Tiago , Sancho Francisco , Ferreira Oscar , Bezerra Maria , Ferreira Luis , Rocha Mariana , Fortes Conceicao J.
Published: December 2012

The interaction between waves and morphological changes at the beach face under low wave-energy conditions is examined from data obtained during a field survey at Praia de Faro (Algarve, Portugal). This work describes and analyses measurements of swash velocities acquired with current-meters, water surface elevation obtained with pressure transducers and topographic surveys undertaken during the field campaign. Estimations of sand transport rates are calculated considering different empirical formulations, and the results are then compared against the transport rates deduced from topographic measurements. A representative swash velocity time series based on the non-linear formulation of Abreu et al. (2010) is derived to study the dependence of the bed shear-stress skewness on the tidal phase and how this can affect sediment transport in the swash zone.
SCHMIDT NUMBER OF SAND SUSPENSIONS UNDER OSCILLATING GRID TURBULENCE
Authors: Buscombe Daniel , Conley Daniel
Published: December 2012

In many models of sand suspension under waves, the diffusivity of sediment is related to the diffusivity of momentum by the inverse of the turbulent Schmidt number. The value and parameterization of this number has been the topic of much research, yet a lack of consensus has led to ad hoc adjustments in models of turbulent sediment suspensions, with apparently little physical justification. In order to study sediment diffusivity we conducted laboratory experiments to generate gradient-only sediment diffusion. Concentrations of sand suspended by near-isotropic turbulence generated by an oscillating grid, together with detailed velocity measurements, were used to calculate vertical profiles of the Schmidt number with a range of grain sizes and flow conditions. Initial results suggest that momentum diffusivity is greater than sediment diffusivity, and that the ratio of the two scales with grid Reynolds number. Ongoing work will ascertain whether an apparent grain size dependence could instead be explained by two-way feedbacks between sediment and turbulence.
A 3D SEDIMENT TRANSPORT MODEL FOR COMBINED WAVE-CURRENT FLOWS
Authors: Ma Peifeng , Madsen Ole Secher
Published: December 2012

Accurate prediction of current velocity and bottom shear stress, which both can be significantly influenced by wind waves, is essential for sediment transport predictions in the coastal environment. Consequently wind-wave effects must be taken into account in a numerical sediment transport model for application in coastal waters. In the present study, elements of a large-scale 3D numerical coastal circulation and sediment transport model are developed to predict net, i.e. the wave-period-averaged, sediment transport rates. The sediment transport components considered are (i) bed-load transport; (ii) mean suspended load sediment transport within the wave boundary layer, which is obtained from an analytical solution; and (iii) suspended load sediment transport above the wave bottom boundary layer, which is obtained from a numerical model. In all model components wind wave effects are accounted for through simple analytical models. Thus, the roughness prescribed for the hydrodynamic part of the numerical coastal circulation model is the apparent roughness, i.e. the roughness experienced by a slowly varying current in the presence of waves. Similarly, the reference concentration specified for the sediment transport part of the numerical model is obtained from analytical solutions for suspended sediment concentrations within the combined wave-current bottom boundary layer. Stratification effects caused by suspended sediment are included in the large-scale numerical sediment transport model. Results of idealized tests suggest that wind wave effects can be pronounced, e.g. in some typical coastal scenarios sediment can only be mobilized when wind waves are present and accounted for. It is also shown that stratification can significantly affect suspended sediment transport rates of fine sediments.
COUPLED 3D MODELING OF TURBIDITY MAXIMUM DYNAMICS IN THE LOIRE ESTUARY, FRANCE
Authors: Walther Regis , Schaguene Julien , Hamm Luc , David Eric
Published: December 2012

Comprehensive 3D modeling efforts to understand salt intrusion and fine sediment dynamics in the Loire estuary started in 2006 and first results about the role of fluid mud on the hydrodynamic circulation through the bottom roughness was reported by Hamm and Walther during ICCE 2008. Recent progress since 2008 includes a) the coupling between the three modules (hydrodynamic, salinity, fine sediment transport) in order to let the fluid mud control the bottom roughness, b) the improvement of the vertical turbulence model enabling to reproduce strong stratifications observed during neap tides, c) a new empirical consolidation model calibrated against lab measurements and including the quantification of the erosion rate over a large range of bed dry densities and d) a new parameterization of the settling velocity function of the turbulence level of the flow. These developments have been validated over a period of five months in winter against field measurements of salinity and turbidity acquired through a permanent network of fixed sub-surface turbidimeters established in 2007. Additional validation against bathymetric measurements of the position of the fluid mud layer in the navigation channel is also presented.
QUANTIFYING NEARSHORE MORPHOLOGICAL RECOVERY TIME SCALES USING ARGUS VIDEO IMAGING: PALM BEACH, SYDNEY AND DUCK, NORTH CAROLINA
Authors: Ranasinghe Roshanka , Holman Rob , De Schipper Matthieu , Lippmann Tom , Wehof Jennifer , Duong Trang Minh , Roelvink Dano , Stive Marcel
Published: December 2012

Time scales of post-storm nearshore morphological recovery and physical processes governing these time scales are poorly understood at present. The ability to predict nearshore morphological recovery time scales based on pre-, during- or post-resetting storm conditions is an essential requirement for building and validating scale aggregated models that operate at macro- and higher spatio-temporal scales. In this study, quality controlled ARGUS video derived beach states at Palm Beach, Sydney (4 years) and Duck, NC (2 years) and concurrent wave data are analysed to quantify the nearshore morphological recovery time scales (Tmr) and to determine the physical processes that may govern Tmr. The results show that Tmr is of the order of 5-10 days at these two beaches. Tmr is moderately positively correlated with the averaged longshore current over the 3 days immediately after the resetting storm, indicating that it might be possible to develop a predictor for Tmr based on wave conditions immediately after the resetting storm. Weak correlations are present between Tmr and several pre-storm, during-storm and post-storm parameters at the two sites. However, these correlations are inconsistent between the two sites. A thorough analysis employing long-term beach state and wave data at several different study sites is required to fully understand this phenomenon.
SHOREWARD SAND TRANSPORT OUTSIDE THE SURFZONE, NORTHERN GOLD COAST, AUSTRALIA
Authors: Patterson Dean
Published: December 2012

To date, no suitable theoretical basis has been derived to predict with reliable accuracy the shoreward sand transport under waves in the deeper water outside the surf zone. This is important for understanding the rate of recovery of beaches after major storm erosion and, in some circumstances, to quantify net shoreward supply of sand to the shoreline from the active lower shore-face below the depth of storm erosion bar development. Even a relatively low rate of long term shoreward net supply may contribute to shoreline stability where it offsets a gradient in the longshore sand transport that would otherwise lead to recession. This paper outlines the results of analysis of a 41 year dataset of beach and nearshore profile surveys to quantify annual average rates of shoreward net sand transport in 6-20m water in an area where the profiles are not in equilibrium due to the existence of a residual river mouth ebb delta bar lobe. Additionally, an empirical adaptation of the sheet flow relationship of Ribberink and Al-Salem (1990) to provide for the effects of ripples has been derived from large wave flume data and correlates well with the measured Gold Coast transport rates. These have been applied to a new coastline modelling system developed as part of research into the long term evolution of Australia's central east coast region in response to sea level change and longshore sand transport processes, which combines the one-line concept of shoreline profile translation within the zone of littoral sand transport with cross-shore profile evolution across the deeper shore-face profile below that zone. It demonstrates the importance of providing for both the shoreward supply from the continental shelf and the varying profile response time-scale across the shore-face in predicting shoreline evolution.
RE-ASSESSMENT AND UPDATE OF BULK LONGSHORE SEDIMENT TRANSPORT FORMULAS
Authors: Mil-Homens João , Ranasinghe Roshanka , Van Thiel de Vries Jaap , Stive Marcel
Published: December 2012

Longshore sediment transport (LST) is one of the main drivers of beach morphology. Bulk LST formulas are routinely used in coastal management/engineering studies to assess LST rates and gradients. Over 50 years of research has resulted in several bulk LST formulas that have been tested with varying levels of rigor. In this study, the predictive skill of one of the most recent bulk LST formulas (Bayram et al., 2007) is evaluated. The calibration coefficients in the formula are improved using a least-squares optimization algorithm, resulting in a significant improvement in predictive skill. The generality of the improved formula is verified via the statistical methods of bootstrapping and cross-validation.
NONUNIFORM ALONGSHORE SEDIMENT TRANSPORT INDUCED BY COASTLINE CURVATURE
Authors: López-Ruiz Alejandro , Ortega-Sánchez Miguel , Baquerizo Asunción , Navidad David , Losada Miguel ngel
Published: December 2012

This work proposes an expression for the alongshore sediment transport and a one-line type model to analyze the importance that the curvature of the shoreline and the bathymetric contours, and the associated alongshore wave energy gradients have in the evolution of the coastline and in the development of shoreline undulations. This model characterizes the alongshore wave energy gradients by means of the surf zone width variations and does not make any restriction on the shoreline curvature. The shoreline undulations of two different types of coast are investigated: a curvilinear coast in a prograding spit front, and an erosional stretch of coast adjacent to a river mouth. The results for the first one are in good agreement with observations. For the erosional coast good qualitative results are obtained, although a more intensive study is required.
SCOUR DEVELOPMENT IN COMPLEX SEDIMENT BEDS
Authors: Porter Kate Emily , Simons Richard , Harris John , Ferradosa Tiago Fazeres
Published: December 2012

Offshore windfarms are often situated in complex sediment beds made up of layers and mixtures of sands, gravels and clays. However, little is known about how these types of sediment beds actually affect the scour process. Therefore, a series of laboratory tests were conducted to test simplified cases of layered and mixed sediment beds, as a basis for improving understanding of scour in complex situations. Two sands were used in the tests; one fine and one coarse with 0.2 and 0.6mm respective median grain sizes. In the layered case with fine sand as the upper layer, it was found that scour development in the underlying coarse sand was enhanced compared to scour in a uniform bed of the coarse sand. In the mixed case the shape of the scour curve was significantly altered as were the time to equilibrium and equilibrium scour depth.
MODELLING DUNE EROSION, OVERWASH AND INUNDATION OF BARRIER ISLANDS
Authors: Hoonhout Bas , Van Thiel de Vries Jaap
Published: December 2012

Physical model experiments are performed at Deltares to investigate the morphological response of barrier islands on extreme storm events. The experiments included dune erosion, overwash and inundation regimes. Extensive measurement techniques made detailed comparison with numerical models possible. This paper describes the comparison between the physical model results and the numerical morphodynamic model XBeach. It appeared that XBeach simulates the main characteristics in hydro- and morphodynamics at profiles with shallow foreshores, which are characteristic for barrier islands, well. However, the absolute results of especially the overwash experiments still do not agree with the measurements. It is expected that several generic issues regarding small-scale physical model experiments are of influence here. Nevertheless, calibration of the XBeach model seems to be necessary for shallow profiles. Especially the calibration of the wave characteristics on the shallow foreshore, related to the morphodynamics is far from trivial.
ADAPTATION OF A BOUSSINESQ WAVE MODEL FOR DUNE EROSION MODELING
Authors: Droenen Nils , Deigaard Rolf
Published: December 2012

In the present paper we consider the adaptation of the Boussinesq wave model MIKE21 BW to the case of dune ero-sion. The process of dune front erosion and redistribution of the eroded dune material was described by two separate models. Erosion was modeled as an effect of direct impact from wave fronts on the dune front and subsequently slumping. Redistribution of the slumped material was modeled using a simple power law model connecting the depth integrated flow velocity with the local sediment transport. The paper presents three model tests. First the model was tested against Deltaflume experiment T01 showing a good overall agreement. Then the model was run for a number of numerical test cases: 1) Sensitivity to main parameters and 2) the effect of adding sand to the dune foot as a mean to protect the erosion.
DUNE EROSION PHYSICAL, ANALYTICAL AND NUMERICAL MODELLING
Authors: D'Alessandro Felice , Tomasicchio Giuseppe Roberto , Musci Fausta , Ricca Andrea
Published: December 2012

The present paper provides an overview of the large-scale physical model experiments performed at the Canal d'Investigaciò i Esperimentaciò Marìtima (CIEM), Laboratori d'Enginyeria Marìtima (LIM), Universitat Politècnica de Catalunya (UPC), Barcelona, within the EU-Hydralab III Integrated Infrastructure Initiative. The model tests have been carried out in a flume with a sandy dune exposed to a combination of water levels and wave conditions. Different regimes of wave attacks on the sandy/beach dune system have been investigated; in particular, the study provides a unique set of large-scale physical data concerning the storm waves induced dune overwash (Tomasicchio et al. 2011a; Tomasicchio et al.2011b). The effects of various "load parameters† on the dune erosion process generation, including dune recession rates in terms of the retreat of the dune face, Î"x, and the eroded volume, Î"V, have been investigated and discussed. The laboratory data sets have been adopted to calibrate and verify the analytical model proposed by Larson et al. (2004) in order to calculate the values of Î"V at specific time intervals. Furthermore, the profile measurements have been used to calibrate and verify the numerical model C-SHORE (Kobayashi et al. 2007) predicting the beach-dune profile modifications over the near-shore region (Tomasicchio et al. 2011a; Tomasicchio et al.2011b).
WAVE OVERWASH OF VEGETATED DUNES
Authors: Gralher Christine , Kobayashi Nobuhisa , Do Kideok
Published: December 2012

Sand dunes play a significant role during coastal storms by absorbing the impacts of storm surge and high waves. Therefore, rapid profile changes and destruction of sand dunes, which may be caused by wave-induced overwash, lead to an increased flood risk landward of dunes. The effects of vegetation on dune erosion and overwash during storm events, however, have never been studied. This study is based on a laboratory experiment investigating the effects of woody plants on dune erosion and overwash of high and low dunes. During the five tests conducted foredune scarping was observed for the three high dune tests but did not occur for the two low dune tests. A narrow vegetation placed on the steep backdune of the high dune did not reduce wave overtopping and sand overwash. However, the wide vegetation figuration, which covered the backdune and foredune, reduced foredune scarping, prevented wave overtopping initially and reduced sand overwash after the initiation of wave overtopping for the high
dune. It also slowed down the erosion process of the low dune significantly by retarding wave uprush and reducing wave overtopping and overwash.
OPERATIONAL FORECASTING OF BEACH MORPHODYNAMICS. RELIABILITY AND PREDICTIONS LIMITS
Authors: Sánchez-Arcilla Agustín , Gracia Vicenç , Grifoll Manel , Garcia Manuel , Pallarés Elena
Published: December 2012

.The paper presents a nested and coupled modelling suite including meteorological, waves, currents and morphodynamics sub-routines. The sequence has been applied to two distinctive beaches along the Catalan coast in the Spanish Mediterranean. Models and observations from two intensive campaigns have been compared to establish the accuracy and reliability of morphodynamic simulations, with the aim to determine uncertainty intervals and to assess the suitability of using such a modelling tool for reducing storm induced risks in beach management
A NEW CONCEPTUAL MODEL FOR AEOLIAN TRANSPORT RATES ON BEACHES
Authors: De Vries Sierd , Stive Marcel , Van Rijn Leo , Ranasinghe Roshanka
Published: December 2012

In this paper a new conceptual model for aeolian sediment transport rates is presented. Traditional sediment transport formulations have known limitations when applied to coastal beach situations. A linear model for sediment transport rates with respect to wind speed is proposed and supported by both data and numerical model simulations. The presented model does not solve complex wind fields and is therefore very easily applicable. Physical principles such as the presence of a threshold velocity and interaction with the bed surface are yet to be implemented before the model can be used for predictive purposes.
AN ENERGETIC TYPE MODEL FOR THE CROSS-SHORE DISTRIBUTION OF TOTAL LONGSHORE SEDIMENT TRANSPORT
Authors: Baykal Cuneyt , Ergin AyÅŸen , Guler IÅŸıkhan
Published: December 2012

This paper presents an energetic-based simple approach for the computation of cross-shore distribution of total longshore sediment transport (LST) rates. The proposed approach (Baykal 2012) follows similar assumptions with the given formula of Bayram et al. (2007) for the total LST rate (Qlst,t) across the surf zone and is applied to investigate the relation between the rate of dissipation in wave energy flux due to wave breaking and total longshore sediment flux using the available laboratory measurements of Wang et al. (2002) and Gravens and Wang (2007) and the field measurements carried out at Duck site, North Carolina, USA between years 1995-1998 (Miller 1999). The proposed approach is also compared with some of the available distributed total load models. From the comparative studies, it is found that the proposed approach shows good agreement with both the laboratory and field measurements, using a single empirical constant, both qualitatively and quantitatively, especially for the cases where the wave conditions are highly energetic (both for plunging and spilling type breakers) and the suspended load is the main mode of sediment transport in the surf zone.
APPLYING AN ANALOGUE FOR A CONCEPTUAL MODEL FOR THE DEVELOPMENT OF A MEGA NOURISHMENT
Authors: Achete Fernanda , Luijendijk Arjen
Published: December 2012

This paper discusses the effectiveness of a mega-nourishment project. Mega-nourishment is a new technology for beach nourishment that has recently been developed. It arises as an alternative to beaches where a structural erosion problem is observed and there is the need for continuously nourishments works. A pilot project was implemented near The Hague (The Netherlands) in October 2011, called the Sand Engine [Mulder 2000], however the impacts of such project are widely unknown. From this perspective the study of a natural coastal area that was subjected to similar conditions can generate know how about the impacts of such a project. One of these natural examples is Ameland: one of the Frisian Islands in the Wadden Sea. Ameland experienced large natural nourishment coming from the ebb tidal delta. The nourishment shape and magnitude were in the same order of magnitude of to the Sand Engine project, leading to a comparison point. In the Ameland case this nourishment occurred on 1990`s and on 1993 achieved a similar shape to the Sand Engine pilot project and currently almost all the sediment is already spread. So from the natural case we can assume that the Sand Engine is going to take around 2 decades to spread all the nourished sediment, a special care should be taken in the down-drift coast to avoid early erosion.
COMPARISON OF 2D AND 3D LARGE SCALE MORPHOLOGICAL MODELING OF OFFSHORE WIND FARMS USING HPC
Authors: Christie Elizabeth , Li Ming , Moulinec Charles
Published: December 2012

The rapidly developing offshore wind farm sector has increased the need to understand if wind farm placement and design has any impact on large scale coastal processes. This paper looks at high resolution hydrodynamic and morphological modeling of offshore wind farms in both 2D and 3D to determine whether either model is capable of representing complex flow patterns around monopile structures and subsequent sediment transport.
A LONG-TERM EQUILIBRIUM BEACH PLANFORM MODEL FOR COASTAL WORK DESIGN
Authors: Cánovas Verónica , Medina Raúl
Published: December 2012

Traditional models usually allow fitting the equilibrium beach planform of crenulated beaches knowing wave climate characteristics at a control point. However, sometimes there are shoals or bars in the surf zone which affect surf zone dynamics and longshore sediment distribution, and it is difficult to take into account these elements using those traditional models. A long-term equilibrium beach planform model is proposed here based on sediment transport equations. This model takes into account the sediment transport due to oblique wave incidence and that due to wave height gradient. Two case studies have been studied: a simple pocket beach and a beach which is sheltered by a sandstone bar. Results show the model fits reasonably well the equilibrium beach planform to the shorelines of those beaches. This model is more suitable than traditional models when there are elements affecting surf zone dynamics.
SEDIMENT- AND MORPHODYNAMICS OF SHOREFACE NOURISHMENTS ALONG THE NORTH-HOLLAND COAST
Authors: De Sonneville Ben , Van der Spek Ad
Published: December 2012

The Dutch coastal maintenance policy which was implemented in 1990 aims at fighting structural erosion by nourishing sand. Initially, the beaches were nourished. The lifetime of these beach nourishments turned out to be relatively short (~2 yrs), especially at identified erosion 'hotspots' along the North-Holland coast (e.g. Egmond aan Zee). Therefore, from 1999 on, an alternative approach was considered, in which beach nourishments were combined with large nourishments on the shoreface (seaward of the outer breaker bar). In recent years, the evolution of individual shoreface nourishments was analyzed on a spatial scale of kilometres and a temporal scale of years, with a focus on their cross-shore development (e.g., Van Duin et al., 2004). In these studies, their alongshore interaction received little attention. The main objective of the present study is to investigate the evolution and lifetime of five large (~1-2 million m3) shoreface nourishments applied between 1999 and 2005 on a spatial scale that includes the larger part of the North-Holland coast (~40km). The analysis of bathymetrical data shows that all five shoreface nourishments evolved into new outer bars with deep troughs on their landward side, that temporarily interrupted the 'autonomous' cyclic offshore migration of breaker bars (e.g. Wijnberg, 1995). Alongshore, the nourishment placed at Camperduin in 2002 connected to the existing outer bar, while the nourishments placed at Egmond aan Zee and Bergen in 1999 and 2000 respectively, remained isolated. The 2004 Egmond and 2005 Bergen nourishments interconnected into a long bar. At Camperduin, the newly formed outer bar remained quite stable in the years after its placement. The bars resulting from the 1999 Egmond aan Zee and 2000 Bergen nourishments, however, almost fully disintegrated within five years, while the interconnected bar of the 2004 and 2005 nourishments is still largely intact after 5 years. The results suggest that the effectiveness of shoreface nourishments is influenced by their shore-parallel length and their ability to connect to surrounding (natural or nourishment) bars. The observed morphodynamic patterns suggest that the 'lost' sand is mainly redistributed to the breaker zone, and further transported alongshore.
LAG EFFECTS IN MORPHODYNAMIC MODELLING OF ENGINEERING IMPACTS
Authors: Knaapen Michiel A.F. , Kelly David M.
Published: December 2012

This paper details the extension of the sediment transport and morphology model SISYPHE to include a lag term within the bed exchange source term of the, depth-averaged, continuity of sediment concentration equation. This lag term represents the time it takes for a sediment concentration profile to adapt to spatial or temporal changes in the flow. The inclusion of a lag term means that the settling velocity is no longer the only scaling factor for the exchange of sediment between the water and the bed. The modified sediment transport and morphodynamics model is tested against field data from the Thames estuary (UK) and on the morphodynamic development of a dredged trench in flume experiments. It is illustrated that the lag factor introduced is essential to model the sediment transport and morphodynamics, especially when considering engineered situations, where the bed is out of equilibrium with the flow conditions. Moreover, with this lag factor included, there is evidence that SISYPHE can be used for morphodynamic modeling of engineered situations.
SEDIMENT TRANSPORT AT THE BOTTOM OF SEA WAVES
Authors: Vittori Giovanna , Blondeaux Paolo
Published: December 2012

The flow in the wall boundary layer generated close to the sea bottom by the propagation of a monochromatic surface wave is determined by considering small values of both the wave steepness and the ratio between the thickness of the boundary layer and the local water depth. Depending on the hydrodynamic conditions, the sea bottom can be plane or rippled. The geometrical characteristics of the bottom forms are predicted using empirical formulae and, then, the bedforms are assumed to behave as a bottom roughness, the size of which is related to the size of the ripples. The bottom boundary layer is assumed to be turbulent and the flow field is computed by means of a two-equation turbulence model. Then the sediment transport is evaluated. The bed load is obtained using an empirical relationship. The suspended load is determined by computing the sediment flux, once the spatial and temporal distribution of sediment concentration is determined. A comparison of the model findings with the experimental results supports the approach.
INVESTIGATION OF THE SWASH ZONE EVOLUTION AT WAVE TIME SCALE
Authors: Astier Jessica , Astruc Dominique , Lacaze Laurent , Eiff Olivier
Published: December 2012

The present work is dedicated to the study of the swash zone bed evolution at a high temporal and spatial resolution to investigate single-wave to wave-group time scales. The measurements are obtained in a large scale wave flume with a 1/15 sloping beach of well-sorted sand (d50 = 250 ï­m). The wave regime considered is a random Jonswap spectrum (peak enhancement factor ï§ = 3.3, significant wave height HS = 0.53 m and peak period Tp = 4.14 s). A stereoscopic technique (Astruc et al., 2012) has been used to measure the sand bed evolution in the swash zone over a 3×2 m² area. This experiment allows us to capture the swash dynamics and the bottom evolution at the different temporal scales. The results prove the strong correlation between wave forcing and swash zone response over the entire experiment, even if the bottom evolves. At shorter time scales, we can observe the signature of gravity and infragravity waves. We showed that at both time scales, the erosion process exhibits a strong variability in time as accretion and erosion events are observed. The spatial variability of the bottom evolution is stronger at gravity than at infragravity time scales. These results reinforce the now-admitted idea that the mean evolution of the sand bed in the swash zone is the result of several events of a very different nature, which themselves depend on the details of the swash hydrodynamics.
BEACH MEMORY
Authors: Turki Imen , Medina Raul , Gonzalez Mauricio
Published: December 2012

A new concept of beach memory is investigated in this research. Using a Beach Evolution Model developed for beach rotation, we define a function of beach memory able to describe the weight of the preceding wave conditions and their contribution in the current beach response. The time beach memory time is also defined as the period of time required for the beach memory function to be dissipated in the previous time to negligible values. The Beach Memory Function and the Beach Memory Time can be used to determine the influence of the preceding energy in the current coastal changes. Both new concepts were applied to quantify the Weighted Energy Flux Direction required for the beach planform to be estimated based on the parabolic approximations. Modeled results reproduce successfully observed planform positions.
APPLICATION OF A NEW SAND TRANSPORT FORMULA WITHIN THE CROSS-SHORE MORPHODYNAMIC MODEL UNIBEST-TC
Authors: Van der Werf Jebbe , Nomden Harm , Ribberink Jan , Walstra Dirk-Jan , Kranenburg Wouter
Published: December 2012

In this paper, we have implemented and tested the new SANTOSS sand transport formula with the cross-shore morphodynamic model UNIBEST-TC using data from the LIP and Grasso wave flume experiments. It is shown that the total net sand transport is a delicate balance between wave- and current-related transport in the wave boundary layer (which can be on- or offshore-directed) and offshore-directed current-related suspended load above it. The change from onshore to offshore net transport for the two Grasso cases was reproduced by the SANTOSS model and seems to be due to the increasing importance of phase-lags between intra-wave velocities and sand concentrations. More generally, measured net sand transport rates are reasonably well reproduced by the SANTOSS formula outside the surf zone if orbital velocities and ripple heights are predicted correctly and phase-lags between velocities and suspended sand concentrations are accounted for.
SEDIMENT SORTING AND BEACH MORPHOLOGY UNDER PLUNGING WAVE BREAKING
Authors: Pedrozo-Acuña Adrián , Resendiz Diana , Mendoza Edgar , Silva Rodolfo
Published: December 2012

This paper presents an experimental investigation into the response of coarse-grained beaches under the action of plunging wave breaking. Beach profile results allowed the identification of three main morphological responses. These are: a beach profile which presented the generation of a clear step below the SWL; a beach shape that did not form any beach step; and a beach face which evolved a bar-like step. Additionally, high-resolution velocity measurements illustrate the prevailing hydrodynamic conditions in the surf-swash transition zone. These results were validated with ADV measurements collected at two cross-shore locations. Through Euler's equation the pressure field was associated to the total acceleration in the fluid, allowing a careful assessment of the contribution of each the acceleration terms to the resulting momentum balance. In the region close to the impact point, the magnitude of the local acceleration under the plunging waves is insignificant, while at the same location the role of advective terms cannot be overlooked. Results indicate the relevance of including advection processes for the accurate calculation of sediment transport under the action of plunging breakers across the nearshore zone.