bluuebunny/crossref_metadata_2025 huggingface dataset:
ON MODELLING BEACH PROFILE EVOLUTION
Authors: Karunarathna Harshinie , Reeve Dominic E , Spivack Mark
Published: October 2012

Behaviour-oriented beach evolution models are normally applied in a prognostic fashion, with model parameters and boundary conditions estimated from previous experience, other forecasts or from historic measurements. Here, we use observations of beach profiles to solve a cross-shore beach profile evolution equation in an inverse manner to determine key model parameters, cross-shore sediment diffusion coefficient and a time-varying source function. The data used to demonstrate the method are from Christchurch Bay in Dorset, United Kingdom. It was found that there is a significant contribution from diffusive processes to the morphodynamic variability of the beach profiles and that the development and disappearance of cross-shore coastal features such as upper beach berms and inter- and sub-tidal bars are well captured by the time-varying source function in the governing equation.
ON THE INITIATION OF NEARSHORE MORPHOLOGICAL RHYTHMICITY
Authors: De Schipper Matthieu Andreas , Ranasinghe Roshanka , Reniers Ad , Stive Marcel
Published: October 2012

Nearshore rhythmicity is often initiated in the period just after a storm where the subtidal bar is turned alongshore uniform. The initiation time as well as the length scales of the created rhythmicity varies from one storm period to another. Here we show that the post-storm wave conditions are related to the initiation of the morphological rhythmicity. Narrow-banded and long wave period, both proxies for swell waves, are often found to be present priorto the initiation of rhythmicity. Furthermore, numerical model computations illustrate that swell waves induce significantly larger wave group induced velocities on the bar. These findings imply that the arrival of swell waves can initiate and stimulate the nearshore morphological rhythmicity.
NUMERICAL MODEL OF CURRENT AND SEDIMENT TRANSPORT IN THE WAVE BOUNDARY LAYER
Authors: Zhu Yuliang , Ma Jing , Wang Hao
Published: October 2012

Mathematical model is one of the means to study of turbulent wave boundary layer. The paper analysis of the existing model, adopt a more reasonable boundary condition to establish a improved mathematical model of 1DV turbulent wave boundary layer using k-Îµ model. The paper recommends brief flow simulation and mainly introduced the simulation of the sediment concentration. The paper use the eddy-viscosity value which calculation by the mathematical model and the model of You Zaijin on time-invariant eddy-viscosity into the relationship about sediment diffusion coefficient and eddy-viscosity to calculate the sediment concentration. The calculation results turns out the way that use the eddy-viscosity value which calculation by the mathematical model into the relationship can obtain better timely sediment concentration value. When use the model simulates the time-invariant sediment concentration, the two ways have not many distinctions. It means the way that that use the eddy-viscosity value which calculation by the mathematical model into the relationship is feasible.
THE SIGNIFICANCE OF WAVE REFLECTION ON THE MORPHOLOGY OF INTERTIDAL MUDFLATS
Authors: Chellew Elizabeth , Rossington Kate , Townend Ian , Amos Carl , Richardson Stephen
Published: October 2012

The influence of seawalls in modifying the equilibrium form of a shoreline has previously caused extensive debate. A numerical model was used to predict the equilibrium form of muddy intertidal profiles, along a shoreline in Southampton Water, UK. It was found that the profile containing a seawall had a very different profile form to the undefended sites, and that this seawall profile could not be accurately represented in the model. The model was extended to include wave reflection from the seawall, producing a new prediction with a much improved resemblance of the observed profile. It was concluded that the likely cause of the different profile form at the site of the seawall in this case, is due incident and reflected wave interaction.
SUSPENDED-SEDIMENT-BASED BEACH MORPHOLOGY MODEL APPLIED TO SUBMERGED GROIN SYSTEM
Authors: Uno Yoshiyuki , Goda Yoshimi , Ono Nobuyuki
Published: October 2012

A beach morphology model based on sediment suspension and settlement is applied to a system of seven submerged groins, which have a function of reducing the speed of longshore currents and controlling beach erosion. Nearshore currents are computed with the PEGBIS model by Goda (2004) for directional random wave transformation, and beach morphology is estimated with the suspended sediment transport model by Katayama and Goda (2003) with a new suspension coefficient by Goda (2010). The computation indicates the efficacy of a submerged groin system for beach erosion control. Discussions are made on some aspects of the submerged groin system to be clarified through further investigations.
LONG-TERM EVOLUTION OF SAND AND GRAVEL BEACHES ON THE MIYAZAKI COAST
Authors: Sato Shinji , Kishimoto Shun , Hiramatsu Haruna
Published: October 2012

Long-term evolution of Miyazaki Coast was investigated in terms of four aspects, geology and geography,
comparison of shoreline in available maps and photographs, sediment retention analysis in watershed scale and sediment size as well as luminescence measurements of foreshore sediments. Geological and geographical analysis revealed steep topography in northern part and fluvial plain on the southern part. The total rate of sediment retention in reservoirs was found to be as much as 1.9 million m3/year. Historical shoreline retreat in the recent 200 years was significant in the northern region whereas severe erosion was developed in the last decades on the southern region close to the rivermouths of the Hitotsuse River and the Ooyodo River. The sand grain size and the thermoluminescence intensity were both found to decrease from north to south, implying the dominant direction of longshore sand transport is from north to south.
A METHODOLOGY TO SIMULATE MEDIUM TERM MORPHOLOGICAL CHANGES IN A PRACTICAL COMPUTING TIME
Authors: Jimenez Nestor , Mayerle Roberto
Published: October 2012

In this paper the assessment of the preliminary results of a methodology to enable predictions of medium-term morphodynamics accounting for the effects of storms is carried out. The methodology integrates the approaches based on a morphological acceleration factor and on the empirical orthogonal functions to account respectively for the morphological changes on the medium and short term. In a very simplified fashion, the effects of the storms are represented by a superposition of most relevant bathymetrical changes. The effectiveness of the methodology was assessed for a coastal stretch along the German Baltic Sea. The analysis of the simulations of morphodynamics for a period of 10 years showed that the method is able to predict volumetric changes along the coastal stretches reasonably well. However it fails to describe the spatial variation of the morphological changes near the coast. Sensitivity studies show also that the results are significantly affected by the set-up scheme of the methodology. Preliminary results during the assessment of the methodology gave clues about the evolution of the morphology of the German Baltic Sea coast. The methodology can be used as a practical tool for initial assessments of tendencies of morphological evolution. Obviously, in this investigation, the method proposed to account for to the storms is a simplified representation of the reality. In this regard, further research is needed to include a more realistic representation of the chronology taking into account their intensity.
MORPHODYNAMIC UPSCALING WITH THE MORFAC APPROACH
Authors: Ranasinghe Roshanka , Swinkels Cilia , Luijendijk Arjen , Bosboom Judith , Roelvink Dano , Stive Marcel , Walstra Dirkjan
Published: October 2012

The Morphological Acceleration Factor (MORFAC) approach for morphodynamic upscaling enables the simulation of long term coastal evolution. However the general validity of the MORFAC concept for coastal applications has not yet been comprehensively investigated. Furthermore, a robust and objective method for the a priori determination of the highest MORFAC that is suitable for a given simulation (i.e. critical MORFAC) does not currently exist. This paper presents some initial results of an ongoing, long-term study that attempts to rigorously and methodically investigate the limitations and strengths of the MORFAC approach. Based on the results of a numerical modelling exercise using the morphodynamic model Delft3D, the main dependencies and sensitivities of the MORFAC approach are investigated. A criterion (based on the CFL condition for bed form migration) for the a priori determination of the critical MORFAC is also proposed.
PREDICTING MOVABLE BED ROUGHNESS IN COASTAL WATERS
Authors: Humbyrd Chelsea Joy , Madsen Ole Secher
Published: October 2012

Accurately predicting movable bed roughness is essential to the analyses of transport processes, but when the bottom is rippled, as it commonly is in the coastal environment, characterizing the roughness is less straightforward than when the bottom is flat. The common method of predicting roughness, while effective, unnecessarily predicts ripple geometry and requires a model-dependent factor, which varies widely, relating ripple geometry and bottom roughness. We have therefore developed an alternative, more direct method of predicting bed roughness in the ripple regime: the wave energy dissipation factor is predicted from flow and sediment information and then any desired theoretical friction factor model is used to back-calculate the roughness. This paper describes the common and proposed methods of predicting roughness and presents results of preliminary testing of the methods with field data. Both methods adequately predict current velocities in wave-current field flows, with the proposed method yielding the smaller RMS-error of 3.1 cm/s. Remaining questions concerning the appropriate near-bottom orbital velocity required to describe field conditions must be resolved when additional field data becomes available.
MORPHOLOGICAL MODELING OF BAR DYNAMICS WITH DELFT3D: THE QUEST FOR OPTIMAL FREE PARAMETER SETTINGS USING AN AUTOMATIC CALIBRATION TECHNIQUE
Authors: Briere Christophe , Giardino Alessio , Van der Werf Jebbe
Published: October 2012

The modeling of bar dynamics is crucial for understanding coastal dynamics and shoreface nourishment evolution. Due to the complexity and variability of the physical processes involved, the formulations developed within the process-based numerical modelling system Delft3D for representing the forcing of the morphodynamic processes (waves, currents, sand transport) contain a high number of calibration parameters. Therefore, the setting up of any Delft3D computation requires a tedious calibration work, usually carried out manually and therefore by definition subjective. The aim of this work is the setting up of an automated and objective calibration procedure for Delft3D morphodynamic computations. A number of calibration parameters have been identified based on a careful sensitivity analysis. The calibration method named DUD (Does not Use Derivatives) is selected and coupled to a alongshore uniform Delft3D model. The validity of the implementation is shown based on synthetic tests (twin experiments). The validation test is carried out using field data collected at Egmond-aan-Zee (The Netherlands). This paper shows that the tool can be successfully used to calibrate Delft3D. However, further research is especially required to understand whether the computed parameters settings only simulate the best morphodynamic evolution of the bars or also describe properly the underlying physical processes.
MODELLING LONG TERM IMPLICATION OF CLIMATE CHANGE PROJECTION ON SHORE MORPHOLOGY OF NORTH NORFOLK, UK, COMBINING TOMAWAC AND SCAPE
Authors: Chini Nicolas , Stansby Peter , Walkden Mike , Hall Jim , Wolf Judith , Lowe Jason , Nicholls Robert
Published: October 2012

Assessment of nearshore response to climatic change is an important issue for coastal management. To predict potential effects of climate change, a framework of numerical models has been implemented which enables the downscaling of global projections to an eroding coastline, based on TOMAWAC for inshore wave propagation input into SCAPE for shoreline modelling. With this framework, components of which have already been calibrated and validated, a set of consistent global climate change projections is used to estimate the future evolution of an un-engineered coastline. The response of the shoreline is sensitive to the future scenarios, underlying the need for long term large scale offshore conditions to be included in the prediction of non-stationary processes.
MODELING LONG-TERM BEACH CHANGE UNDER INTERACTING LONGSHORE AND CROSS-SHORE PROCESSES
Authors: Hanson Hans , Larson Magnus , Kraus Nicholas C
Published: October 2012

This paper presents mathematical formulations and a new numerical model GenCade that simulates beach and dune change in response to cross-shore processes of dune growth by wind and dune erosion by storms, and by gradients in longshore sand transport that will also alter shoreline position. The berm plays a central role since the potential for sand to be transported to the dune by wind depends on berm width, and sand lost in erosion of the dune during storms will widen the berm. Morphologic equilibrium considerations are introduced to improve reliability of predictions and stability of the non-linear model. An analytical solution is given to illustrate properties of the model under simplified conditions. Sensitivity tests with the numerical solution of the coupled equations demonstrate model performance. Finally, the numerical model is applied to examine the consequences of groin shortening at Westhampton Beach, Long Island, New York, as an alternative for providing a sand supply to the down-drift beach. Results indicate that the sand will be released over several decades as the shoreline and dune move landward in adjustment to the new equilibrium condition with the shortened groins.
LONG TERM MORPHOLOGICAL MODELLING
Authors: Kristensen Sten Esbj¸rn , Deigaard Rolf , Taaning Martin Anders , Freds¸e J¸rgen , Dr¸nen Nils , Jensen Jacob Hjelmager
Published: October 2012

A morphological modelling concept for long term nearshore morphology is proposed and examples of its application are presented and discussed. The model concept combines parameterised representations of the cross-shore morphology, with a 2DH area model for waves, currents and sediment transport in the surf zone. Two parameterization schemes are tested for two different morphological phenomena: 1) Shoreline changes due to the presence of coastal structures and 2) alongshore migration of a nearshore nourishment and a bar by-passing a harbour. In the case of the shoreline evolution calculations, a concept often used in one-line modelling of cross-shore shifting of an otherwise constant shape cross-shore profile is applied for the case of a groyne and a detached breakwater. In the case of alongshore bar/nourishment migration an alternative parameterization is adopted. All examples are presented, analysed and discussed with respect to the question of realistic representation, time scale and general applicability of the model concept.
MEDIUM-TERM MORPHODYNAMIC MODELING OF MIXED MUD AND SAND IN THE
Authors: Witting Markus , Wehmeyer Christof , Niemeyer Hanz Dieter
Published: October 2012

A morphodynamic model for the Jadebusen basin based on the current DELFT3D model is established. With
morphological information such as qualitative measurements of SPM-concentration (Suspended Particular Matter) and
bottom change estimates as well as detailed surveys of a sand pit refilling process the model parameters for cohesive
transport (Partheniades 1965) are calibrated. Within a period of 8 month, which is condensed to a representative
period of 28 days for the modeling, almost 45% of the initial pit volume was refilled with mud. Despite the lack of
specific field measurements a setup of mud transport parameters can be defined, which allows further investigations of
sand pit locations in the Jadebusen basin. On major outcome is that critical erosion shear stresses for mud should be
spatially varied in order to account for the different consolidation states of the mud fraction. Furthermore the paper
addresses the problem of the initial grain size distribution for graded sediment transport. Wadden flat types are
characterized based on aerial observations which build the underlying information for a relocation model run.
MORPHOLOGY VARIABILITY IN THE VICINITY OF COASTAL STRUCTURES
Authors: Ritphring Sompratana , Tanaka Hitoshi
Published: October 2012

The morphology variability is carried out in this study by using the historical bathymetry data. Two study areas in which the vicinity of coastal structures are selected and make a comparative study, Sendai Port and Yuriage Port. Both are located in the Sendai Coast, northeast of Japan, with the similar incoming wave condition from SE and ESE direction. Sediment is trapped in front of Breakwater at Yuriage Port; on the contrary, the severe erosion occurs in the updrift side of Sendai Port. Consequently, these phenomena should be clarified by study on morphology variability. To overcome these aspects, it needs to analyze a long-term series data set and investigate the characteristics of morphological variability in order to well understand for the perspective of coastal management.
MORPHODYNAMIC MODELING OF THE MEDIUM-TERM MIGRATION OF A TIDAL CHANNEL USING PROCESS-BASED MODEL
Authors: Nguyen Diem , Etri Talal , Runte Karl-Heinz , Mayerle Roberto
Published: October 2012

This paper investigates the predictive capability of a morphodynamic model in capturing the development of a tidal channel on the German North Sea coast which experienced migration in the last few years. A depth-averaged version of a process-based model, Delft3D, is used. A description of the set-up, calibration and validation of the process-based models is presented. Field measurements with a dense spatial and temporal coverage were used for the development of the models. Results from the hydrodynamic and sediment transport simulations were in agreement with observations. The morphodynamic model simulations were speeded up with a morphological acceleration factor in conjunction with a representative period. Results of model calibration and validation covering periods of several years proved the capability of the model to reproduce the migration of the tidal channel. According to the standards usually adopted for checking the accuracy of morphodynamic models, the performance of the model presented here was quite good. The model ability in predicting the migration in the medium-term was found to be dependent primarily on the accuracy of the starting bathymetry, characteristics of the substrata and of the mud sediment fraction as well as on the selection of the representative period. A reduction in the rate of migration of the tidal channel is predicted from 2008 till 2010.
PREDICTION OF FORMATION OF DYNAMICALLY STABLE EBB TIDAL DELTA AND MEASURES FOR PREVENTING OFFSHORE SAND LOSS
Authors: Uda Takaaki , Serizawa Masumi , San-nami Toshiro , Ishikawa Toshinori
Published: October 2012

We developed a model for predicting the evolution of an ebb tidal delta based on the BG model, which was proposed by the present authors using the Bagnold concept of the equilibrium slope. Bathymetric changes around the inlet of Imagire-guchi between 1978 and 2005 were quantitatively analyzed to investigate the evolution of the ebb tidal delta and sand deposition offshore of the inlet. The model was applied to this inlet. The predicted bathymetric changes were in good agreement with the measured changes. Some measures for preventing the offshore sand loss were also considered by applying the model. The most effective measure was predicted to be cross-shore sand bypassing.
THREE-DIMENSIONAL NUMERICAL MODEL FOR SIMULATING THE ACCUMULATION PROCESS OF IMMERSED TUBE TANK OF HMZ BRIDGE
Authors: Wang Zhili , Geng Yanfen , Lu Yongjun
Published: October 2012

In this paper, the development and implementation of a three-dimensional, numerical sediment transport model, which is based on staggered C-unstructured grids in the horizontal direction and Z-level grids in the vertical direction, is delineated. The three dimensional model is discretized by semi-implicit finite volume method, in that the free-surface and vertical diffusion are semi-implicit, thereby removing stability limitations associated with the surface gravity wave and vertical diffusion terms. The remaining terms in the momentum equations are discretized explicitly by integral method. The model is closed physically and mathematically using the Mellor and Yamada level-2.5 turbulent closure submodel. The numerical model is used for simulation accumulation process of immersed tube tank of HMZ (Hong Kong-Macau-Zhuhai) bridge. The model is calibrated and its performance extensively assessed against on-site experiment.
EXPERIMENTAL STUDY ON BOTTOM TOPOGRAPHY CHANGE IN HARBOR DUE TO TSUNAMI
Authors: Sakakiyama Tsutomu , Matsuyama Masafumi , Yoshii Takumi
Published: October 2012

Bottom topography change due to tsunami was experimentally investigated using a rectangular harbor model in a 2-D wave flume. Water surface level and velocity field were obtained as well to discuss the external forces. Accumulation region was observed in the middle of the harbor inside. Formed was conical bed topography. Erosion was around the accumulated region and at the breakwater head as local scour. These topography changes were caused by the tsunami-induced vortices inside the harbor and at the breakwater head.
EVALUATION OF A PROPOSED CHANNEL ON CIRCULATION AND MORPHOLOGY CHANGE AT KAWAIHAE HARBOR AND PELEKANE BAY, HAWAII, USA
Authors: Li Honghai , Brown Mitch , Kraus Nicholas , Smith Thomas , Podoski Jessica
Published: October 2012

In an effort to improve the water quality and restore marine habitats in Pelekane Bay (PB), installation of a circulation channel was proposed with the intent of enhancing water circulation in PB through Kawaihae Deep Draft Harbor (KDDH) and flushing accumulated sediment out of PB. This study was conducted to investigate the hydraulics and sediment transport consequences of dredging such a channel. The coupled wave, flow, and sediment transport Coastal Modeling System (CMS) was applied during a non-storm and a typical winter (storms) time interval. CMS results were analyzed and compared between existing condition and channel alternatives. It was found that upon reaching PB, incident waves breaking induces higher water level from wave setup, whereas the breakwater at KDDH inhibits depth-limited breaking and setup, creating a differential in water surface elevation (WSE). The water level rise along the channel was calculated to be 0.01-0.03 m, with WSE in PB being higher. The differential wave setup, found for almost all wave conditions, produces water flow from PB to KDDH in the proposed channel. The temporally averaged along-channel current speed is calculated from 0.07 to 0.2 m/sec for the non-storm and storm conditions, respectively. Bay-to-harbor flows will move sediment into the channel, most of which is deposited within 120 m from PB. For the winter storm conditions, the maximum deposition in the channel was calculated to be approximately between 0.7 and 2.0 m among the different alternatives. More sand is deposited under the deeper channel alternatives. The channel or bay blockage appears under all channel alternatives before reaching the end of the simulation.
BED SHEAR STRESS IN UNSTEADY FLOW
Authors: Guard Paul Andrew , Nielsen Peter , Baldock Tom E
Published: October 2012

Standard engineering methods of estimating bed shear stress using friction factors can fail spectacularly in unsteady hydrodynamic conditions. This paper demonstrates this fact using direct measurements of bed shear stresses under irregular waves using a shear plate apparatus. The measurements are explained in terms of the influence of the horizontal pressure gradient and the shear stresses acting on the surface of the plate. The horizontal fluid velocity at the edge of the boundary layer and the water surface elevation and slope were also measured. The paper demonstrates that the water surface measurements can be used to obtain accurate estimates of the forces on the bed, by employing Fourier analysis techniques or an innovative convolution integral method. The experimental results indicate that an offshore bed shear stress may be recorded while the free stream velocity remains onshore at all times. This demonstrates the failure of the standard engineering friction factor method in this scenario, since negative friction factors would be required. Important questions are raised regarding the appropriate definition for the bed shear stress when the vertical gradient of the shear stress is large. It is shown that it is problematic to define a single value for a "bed† shear stress in the presence of a strong horizontal pressure gradient. It is also argued that the natural driver for any model used to predict bed shear stress is the pressure gradient (or its proxy the free stream acceleration), rather than the velocity. This allows for accurate calculation of both acceleration effects (more rapid acceleration leads to a thinner boundary layer and higher shear stress) and also the direct action of the horizontal pressure gradient.
PHYSICAL MODEL EXPERIMENTS ON RECLAMATION PROJECT OF FANGCHENG PORT
Authors: Zhao Xiaodong , Ma Jinrong , Wang Xiangming
Published: October 2012

Tidal flat reclamation works is an effective way to relieve the contradiction between supply and demand of land in the coastal region. The reclamation project in the bay will decrease tidal current velocities, change tidal currents field, then slowdown the water exchange in the bay ,which will influence water quality in the bay and increase sediment deposit at navigation channels. To study impacts of hydrodynamic environmental and sediment movement due to reclamation projects in Fangcheng Port, the physical model for tide-current and sediment was constructed in NHRI. The horizontal scale and vertical scale of the Fangcheng Port model is 1/660 and 1/100 respectively. The siltation in the bay and channels mainly caused by suspended load transport under the action of tidal currents and waves.The ability of water exchange in the bay is discussed by simulating sewage diffusion characteristics before and after reclamation projects in the bay. The physical model test results are shown the total tidal volume is decreased by 20% after the reclamation plan, of which 17.5% reduction in the East Bay, 2.5% in West Bay. The tidal currents field in the channel are discussed. The sedimentation rate increases 3-10cm/a in navigation channels and basins of Fangcheng Port.
LAGRANGIAN DROGUE-BASED DRIFTER FOR MONITORING SUSPENDED SEDIMENT TRANSPORT IN INTERTIDAL ENVIRONMENTS
Authors: Nishi Takahiro , Lemckert Charles , Hayashi Kentaro , Yamada Fumihiko
Published: October 2012

The in-situ Lagrangian-Acoustic Drogue (LAD) presented by Schacht and Lemckert (2007) for monitoring the temporal and spatial distributions of both the current and the suspended sediment concentration within the estuary environments has been modified to operate in the shallow water intertidal regions. The new drogue, called the LAD for Inter-Tidal environments (LAD-IT), is equipped with a Global Positioning System (GPS), a small Acoustic Doppler Current Profiler (ADCP) and nephelometer. The small ADCP, which did not have a bottom tracking facility, was used to maximize the range of depths the LAD-IT could operate over. The accuracy of a vertical current profile measured using the LAD-IT was examined through the laboratory experiments conducted at an outdoor stream pool in Kumamoto, Japan, with uni-directional flow conditions, and through the field experiments conducted within an intertidal zone of Ariake Sound in Kumamot, Japan, with multi-directional flow conditions. Under uni- directional flow conditions the current profile was measured within 7% accuracy by summing the surface current velocity calculated using GPS tracking and the relative current profile measured using ADCP. Under multi-directional flow conditions, such as those of tide and wind-induced wave fields, the current profile agreed within 5% accuracy. This was partly because both Eulerian and Lagrangian mass transport velocities under these conditions were on the order of 1cm/s, and thus the error value was very small. The temporal and spatial distributions of both the current velocity and the suspended sediment concentration were also measured using the LAD-IT on the Brisbane River, Australia under uni-directional flow conditions. The field observation results support the conventional concept of the suspended sediment as a vertical balance between downward suspended sediment settling and upward turbulent diffusion fluxes. The results indicate the LAD-IT is adequate for estimating the sediment settling velocity in the field.
A PROCESS-BASED APPROACH TO SEDIMENT TRANSPORT
Authors: Chu Ao , Wang Zhengbing , De Vriend Huib , Stive Marcel
Published: October 2012

A process-based model for the Yangtze Estuary is constructed to study the sediment transport in the estuary. The proposed model covers the entire tidal region of the estuary, the Hangzhou Bay and a large part of the adjacent sea. The dominant processes, fluvial and tidal, are included in the model. The calibration of the model against extensive flow, water level, salinity and suspended sediment data shows a good representation of observed phenomena. With the present calibrated and validated model, the residual flow field and the residual sediment transport field are obtained. The residual sediment transport pattern gives insight into the morphological behaviour of the mouth bars.
NUMERICAL MODELING OF MORPHODYNAMIC CHANGES IN THE JADE ESTUARY - GERMANY
Authors: Gelfort Almut , Ladage Florian , Stoschek Oliver
Published: October 2012

Based on a case study sediment transport was modeled numerically for the Jade estuary. Due to the construction of the JadeWeserPort the morphology in the area is undergoing a relocation. The study gives an overview on various studies undertaken as a consultant tool to help designers and decisions makers. A hydrodynamic as well as a morphodynamic numerical model was set up. Although the input data on the morphodynamic part was limited, the results showed that the tool at hand is capable of producing reliable results in the field of modeling sediment transport.
FORMATION OF DYNAMICALLY STABLE LAKESHORE UNDER SEASONALLY CHANGING WAVE DIRECTION
Authors: Ishikawa Toshinori , Uda Takaaki , San-nami Toshiro , Watanabe Shusuke
Published: October 2012

In the Ukishima region of Lake Kasumigaura, beach nourishment along with the construction of groins has been carried out to recover a sandy beach. After the beach nourishment, part of the nourishment sand was transported away from the beach, turning around the tip of the downcoast groin owing to the oblique wave incidence in winter. To enhance the stability of the beach, the groins were extended and a spur dike was constructed. To design these structures, a numerical simulation using the BG model was carried out, and the optimum shapes were determined by taking into account the seasonally changing wave direction. The effectiveness of the spur dike was numerically evaluated using the BG model.
EMPIRICAL RELATIONSHIP BETWEEN INLET CROSS-SECTIONAL AREA AND TIDAL PRISM: A RE-EVALUATION
Authors: Stive Marcel , Ji Liang , Brouwer Ronald L , Van de Kreeke Co , Ranasinghe Roahanka
Published: October 2012

The well-known empirical relationship between the equilibrium cross-sectional area of tidal inlet entrances (A) and the tidal prism (P), first developed by O'Brien (1931), has been extensively reviewed. Our theoretical investigations indicate that a unique A-P relationship should only be expected for clusters of inlets that are phenomenological similar (i.e. fairly similar hydrodynamic and morphological conditions), and that the exponent q in the A-P relation should be larger than 1. However, relevant published data available to date do not clearly support this theoretical finding. A re-analysis of the available data sets by Stive et al. (2009) indicated that they may not be sufficiently reliable to verify our theoretical finding with regard to q>1 due to the violation of the condition of phenomenological similarity, and possibly also due to violating the initial definitions given by O'Brien (1931) in estimating the tidal prism. The resolution of this issue is important because slightly different values of q result in significantly variable values for the equilibrium cross-sectional area of the tidal entrance. This may have significant implications in determining the true stable equilibrium entrance cross-sectional area. Here we present a re-analysis of the available data with a focus on determining the phenomenological dependencies of the A-P relationship. The available A-P data from the US Pacific, Atlantic and Gulf coasts (Jarrett, 1976 and Powell, 2003) have been re-scrutinized and categorized following the above mentioned phenomenological similarity criteria, viz. similar tidal range, similar sediment size, similar littoral transport and similar hydraulic radius. All together, some 20 different categories were considered and A-P relationships were obtained for each category. Generally, high correlations were found between the stable inlet predicted by each A-P relationship and the corresponding data. However, only in a limited number of categories were they significantly better than the correlations for the complete datasets. Finally, we point out that only in a number of categories the q value associated with the A-P relationship exceeded unity as suggested by the theoretical derivations. In the majority of categories the q value associated with the A-P relationship does not exceed unity. This is truly disappointing, and we have no physical explanation for this and consider this issue unresolved.
MODELING SHORELINE RESPONSE AND INLET SHOAL VOLUME DEVELOPMENT ON LONG ISLAND COAST, UNITED STATES
Authors: Hoan Le Xuan , Hanson Hans , Larson Magnus , Pham Thanh Nam
Published: October 2012

A new numerical model was developed to simulate regional sediment transport, shoreline response in the vicinity of tidal inlets, and inlet shoal volume growth based on the one-line model of shoreline change combined with the reservoir concept for volumetric evolution of inlet shoals. Sand bypassing onshore and sheltering effects on wave action from the inlet bar and shoals were taken into account. The model was applied to unique field data from the south coast of Long Island, United States, including inlet opening and closure. The simulation area extended from Montauk Point to Fire Island inlet, including Shinnecock and Moriches Inlets (Figure 1). A 20-year time series of hindcast wave data at three stations along the coast were used as input data to the model. Several types of sediment sources and sinks were represented, including beach fills, groin systems, jetty blocking, inlet bypassing, and flood shoal and ebb shoal feeding. The model simulations were validated against annual net longshore transport rates reported in the literature, measured shorelines, and recorded sediment volumes in the flood and ebb shoal complexes. Overall, the model simulations were in good agreement with the measured data.
EVALUATION OF INLET MANAGEMENT PRACTICES AT NAVIGATION INLETS IN SOUTHWEST FLORIDA, USA
Authors: Dabees Mohamed A , Moore Brett D
Published: October 2012

This paper describes numerical modeling of long-term evolution of inlet systems in southwest and central Florida. The paper discusses a general methodology developed following four case studies and application to the case study of Gordon Pass in southwest Florida. The case study of Gordon Pass demonstrates the importance of considering large temporal and spatial scales in evaluating morphologic response to inlet management practices. The results describe the evolution of Gordon Pass from 1930 to present. The analysis begins with natural conditions that existed before dredging or inlet modifications and investigates how inlet evolution can be influenced by navigation improvements and provide tools to evaluate alternatives.
COMPARATIVE ANALYSIS OF SUSPENDED SAND CONCENTRATION RECORDED WITH DIFFERENT TECHNIQUES IN A RIPPLED BED REGIME
Authors: Ahmari Alireza , Oumeraci Hocine , Gruene Joachim
Published: October 2012

Sediment entrainment processes due to the oscillatory flow above rippled and plane sea beds are fundamentally different. Whereas above plane beds the sheet flow or bed load regime dominates and the momentum transfer is primarily caused by turbulent diffusion, above a sea bed covered with long crested vortex ripples the well organised coherent vortex mechanisms induce sediment-laden lee vortices at the ripple crest, which will be detached from the bed ejected into the water column and finally shed when the flow reverses. To investigate the sediment entrainment processes above vortex ripples, a study was carried out in the Large Wave Flume (GWK) aiming firstly to find out the most appropriate measuring technique to determine the suspended sediment concentration both temporarily and spatially. and secondly to analyse the intra-wave sediment entrainment processes around a steep ripple.
AERIAL PHOTOGRAPH OF SENDAI COAST FOR SHORELINE BEHAVIOR ANALYSIS
Authors: Pradjoko Eko , Tanaka Hitoshi
Published: October 2012

The shoreline analysis around the Nanakita River mouth has been performed by utilizing aerial photographs to reveal the different behavior between left and right side of the river mouth. The shoreline on left side of river mouth has been moving more dynamically than the right side. The empirical orthogonal function (EOF) method is also applied on the shoreline data to reveal the behavior of shoreline change. The first mode of variability reflects the cross-shore movement which is shown by uniform advance and retreat movement along the beach. The shoreline change around the Nanakita River mouth is dominated by the cross-shore movement which is shown by around 80% contribution of first mode. The second mode of variability depicts the longshore sediment movement which is shown by different shoreline movement between left and right side of river mouth. The longshore movement only contributes around 10% to the shoreline change around the Nanakita River mouth. The second mode also reveals the influence of river mouth to the longshore sediment transport characterized by different shoreline response between left and right side.
SHORELINE ROTATION CAUSED BY LARGE-SCALE EXCAVATION OF REEF FLAT ON SANUR BEACH IN BALI
Authors: Endo Masatoshi , Kobayashi Akio , Uda Takaaki , Noshi Yasuhito , Onaka Susumu
Published: October 2012

In the southern part of Sanur Beach in Bali, beach erosion has occurred between groins after extensive beach nourishment, resulting in shoreline rotation between the groins. The cause of shoreline changes was investigated by field observations, including a bathymetric survey and the sampling of seabed materials, and numerical simulations of beach changes were carried out using Noshi et al.'s model. It was concluded that the shoreline rotation was triggered by the dredging of the reef flat, which caused a change in the wave direction on the reef flat due to the diffraction of waves.
NUMERICAL CALCULATION ON SHORELINE CONSERVATION IN MAJURO ATOLL, THE MARSHALL ISLANDS
Authors: Sato Daisaku , Yokoki Hiromune
Published: October 2012

Development of a numerical model for future estimation of morphological changes in Majuro atoll were carried out, and, at the same time, examination of beach nourishment for sustainable island conservation plan was examined by the developed model. Identified erosion and accretion area from calculated shoreline indicated that the northern tip of Laura and some areas in LongIsland had severe erosion until 100 years later as well as large accretion in northern part of the atoll. Three beach nourishment scenarios using eroded sediments, which were accreted in deep lagoon in northern part of atoll, were examined and they decreased 30% of accumulative erosion volume compared with the non-conservation result. This result shows that the beach nourishment is an effective option to sustainable island conservation plan in Majuro atoll.
SPATIAL AND TEMPORAL VARIABILITY OF LONGSHORE TRANSPORT ALONG GOLD COAST, AUSTRALIA
Authors: Splinter Kristen D , Golshani Aliasghar , Stuart Greg , Tomlinson Rodger
Published: October 2012

Spatial and temporal variability of longshore transport potential for a 35-km stretch of sandy coastline on the east coast of Australia is examined using a 25-year data set. Six-hourly offshore wave data is binned into yearly wave classes using a global k-means algorithm that accounts for wave height, period, and direction simultaneously. Wave class estimates are shoaled into the nearshore using MIKE 21 Spectral Wave (SW) model. Longshore transport is calculated using the formulas of Kamphuis (1991; 2002) and Bayram et al. (2007) and show good agreement with previously published estimates for the Gold Coast, suggesting the wave classification scheme sufficiently represents the variability in yearly wave data. Results show large temporal and spatial variability of transport potential along the coastline. Spatial variation is attributed to shoreline orientation and wave exposure, while temporal variability is significantly correlated with variations in the Southern Oscillation Index.
A FIRST INVESTIGATION INTO THE IMPACT OF VERY LARGE-SCALE OFFSHORE SAND MINING ALONG THE DUTCH COAST
Authors: Van der Werf Jebbe , Giardino Alessio , Mulder Jan , Stolk Ad
Published: October 2012

This paper investigates the impact of very large-scale offshore sand mining along the Dutch coast on waves, currents, sand transport rates and morphology. To this end, we simulate different extreme sand extraction trench geometries (depths between 1 and 17 m, volumes between 10 and 63 x 109 m3) with the process-based modelling system Delft3D. The simulations show that the waves become 0-20% higher, currents change with 0-0.3 m/s and transport rates with 10-80%. In general, the trench has a negative effect on the sand balance of coastal sections, especially near the narrow part of the deepening. The estimated trench impact on dune erosion during normative storm conditions with a frequency of occurrence of 1/10,000 yr is 5-10%. The impact of the deepening is generally seen to increase with depth.
ARTIFICIAL NOURISHMENT AND SAND BY-PASSING IN THE AVEIRO INLET, PORTUGAL - NUMERICAL STUDIES
Authors: Coelho Carlos , Silva Raquel , Veloso-Gomes Francisco , Rodrigues Luis
Published: October 2012

Artificial sand nourishment systems are a potential solution to mitigate erosion beach problems, having been applied in many cases around the world, especially in the U.S.A. and Australia. For the Aveiro inlet, the artificial sand by passing systems may be a good option, due to the availability of sediments accumulating at the north of the northern Aveiro inlet breakwater. A fixed artificial sand by-passing system can be proposed. However, fixed and continuous sand by-passing systems are the most expensive solutions. In order to reduce the economical aspect, periodic sand nourishment and semi-mobile systems are presented as an alternative. For those, different options of artificial nourishment can be proposed, depending on sediments volumes, location, distribution area, number of periodic operations, etc. Discussion about the results of the numerical simulations of shoreline evolution after different artificial nourishments scenarios at the southern part of the Aveiro inlet, in Portugal, is presented. Shoreline accretion/erosion rates, sediment transport volumes and profile sediment budgets have similar behaviors over time and along the coastal stretch, for all the tested scenarios. Generally, important coastal erosion can be mitigated with artificial nourishments and numerical modeling can help to improve the nourishments performance. For this open sandy coast, the sand nourishment simulations show better results near the deposit location for a period of time lower than 20 years. After that period, the nourishment effect is smaller. The southern profiles start benefiting with the nourishment after ten or more years.
FLOW DEPTHS AND VELOCITIES AT CREST AND LANDWARD SLOPE OF A DIKE, IN THEORY AND WITH THE WAVE OVERTOPPING SIMULATOR
Authors: Van der Meer Jentsje Wouter , Hardeman Bianca , Steendam Gosse Jan , Schuttrumpf Holger , Verheij Henk
Published: October 2012

Wave overtopping discharges at coastal structures are well described in the EurOtop Manual (2007), including the distribution of overtopping wave volumes. Each volume that overtops a dike or levee will have a certain flow velocity and depth record in time, often given by the maximum velocity and flow depth. This paper describes some further development of the theory on flow depth and velocities on the crest, but will also show an inconsistency with respect to the mass balance. The second part of the paper gives an analysis of measured values on real dikes, simulated by the Wave Overtopping Simulator. It gives also the method of "cumulative hydraulic load" to compare overtopping discharges for different wave conditions. A large wave height with less overtopping waves, but larger overtopping wave volumes, is more damaging than a small wave height with more, but smaller overtopping volumes, even if the overtopping discharge is similar. The reasons to develop the cumulative hydraulic load have been compared with the recently in the US developed method of erosional equivalence.
WAVE OVERTOPPING AND RUBBLE MOUND STABILITY UNDER COMBINED LOADING OF WAVES AND CURRENT
Authors: Eslami A. Sepehr , Van Gent Marcel R.A.
Published: October 2012

Coastal structures such as breakwaters are usually studied under wave loading only. However, at several locations also a current is present. For instance, breakwaters along intake and outfall channels of power plants and desalination plants, or structures in regions with important tidal currents, experience wave loading that can be affected by currents. Nevertheless, wave overtopping and rubble mound stability are usually studied under wave loading only; the effects of waves on wave overtopping and rock slope stability have been summarised in many empirical design formulae. None of the existing empirical relations account for the effects of currents on the wave loading and consequently on wave overtopping and rock slope stability. The effects of wave-current interaction on wave overtopping and rubble mound stability has not been quantified, other than that for mild currents these processes are dominated by waves. Therefore, the present study is focussed on wave loading in combination with a strong current. This study is based on physical model tests in a wave-current basin. The results show to what extent wave overtopping and rubble mound stability are affected by wave loading in combination with a current. Wave overtopping and the damage to rock slopes generally reduce due to the presence of a current compared to the situation without a current.