bluuebunny/crossref_metadata_2025 huggingface dataset:
NUMERICAL MODELING OF COASTAL INUNDATION AND SEDIMENTATION BY STORM SURGE, TIDES, AND WAVES AT NORFOLK, VIRGINIA, USA
Authors: Li Honghai , Lin Lihwa , Burks-Copes Kelly A.
Published: December 2012

A nearshore hydrodynamic and sediment transport model was developed to simulate synthetic storms with design SLR scenarios surrounding the military installations in Norfolk, Virginia. Foreseeable risk and effect of storm surge damage accompanied by waves, tides, and Sea Level Rise (SLR) were examined. The final results include the evaluation of impacts for five SLR (0.0, 0.5, 1.0, 1.5, and 2.0 m) and three storm conditions (50-yr, 100-yr return tropical storms, and a winter storm). Associated with the storm surge and SLR, extensive inundation will occur at the Naval Station Norfolk, approximately 70-80% of the Naval Station Norfolk under the 2-m SLR scenario. The calculated morphology changes indicate that the sediment movement mostly occurs in the navigation channels and the maximum depth changes are more than 3.0 m along the channels. The bed volume changes show that the storms induce a net volume loss within the channel area, an indication of channel flushing in the study area.
INFLUENCE OF NON-LINEAR WAVES AND UNDERTOW IN SANDBAR DEVELOPMENT
Authors: Abreu Tiago , Sancho Francisco , Silva Paulo A.
Published: December 2012

As waves propagate from deep into shallow waters, they begin to interact with the sea floor and undergo through several changes due to non-linear effects. These interactions cause the waves to transform and become non-linear as they decelerate and finally break. These local nonlinearities are reflected on the near-bed oscillatory flow and are inextricably linked to sediment transport, causing erosion-accretion patterns and bar migration. In this work the ability of a practical transport model that includes the effects of velocity and acceleration skewness in the time-varying bed shear stress (Abreu et al., 2011) is assessed to predict sediment transport rates under oscillatory flows and currents. The results are compared with two different data sets obtained under sheet flow conditions, showing a good agreement with the measurements. Moreover, its performance to the undertow and to non-linear characteristics is further assessed. The practical sediment transport model is coupled to a simple bed-evolution model, enabling to evidence the relative strength of mechanisms associated with the wave and current induced sand transports. The results show that the formation of the bar and its migration is affected by a new term introduced in the bed shear stress predictor. This time-varying term accounts for the shape of the wave and is described through two non-linear parameters recently proposed in Abreu et al. (2010).This work provides further insights in the correct prediction of sediment transport modeling and sandbar developments, due to the combined influence of non-linear waves with undertow currents.
WAVE FLUME-BASED EVALUATION OF SUSPENDED SAND TRANSPORT IN BREAKING WAVES
Authors: Otsuka Junichi , Watanabe Yasunori
Published: December 2012

In this study, suspended sediment concentration and velocity in surf zones was measured in a small-scale wave flume with three breaker types (plunging, spilling and intermediate) using an optical concentration sensor and an ultrasonic velocity profiler (UVP). The sediment pickup rate was also calculated from the depth-averaged concentration and the wave energy flux dissipation rate. In plunging breakers, relatively large amounts of sediment are suspended in the transition region due to strong three-dimensional turbulent flows generated by large-scale vortices. In spilling breakers, sediment concentration is lower than that seen in plunging breakers because smaller- scale vortices typically develop below the water surface in the transition region. Concentrations in both breaker types remain at lower levels in bore regions because the vortices fully develop into weak turbulent bores. Comparison in the same range of wave energy flux dissipation rates showed that the sediment pickup rates in these small-scale experiments were approximately 103 times greater than those calculated by Goda (2010) using various data compiled from large-scale experiments and field observations.
APPLICABILITY OF SUSPENDED SEDIMENT CONCENTRATION FORMULAE TO LARGE-SCALE BEACH MORPHOLOGICAL CHANGES
Authors: Jayaratne Ravindra , Takayama Yasufumi , Shibayama Tomoya
Published: December 2012

Study of beach morphological changes under storm conditions and its prediction capability are of paramount importance in coastal zone management. Seabed sediment is picked up violently in and outside the surf zone due to suspension mechanisms, therefore a considerable amount of sand is transported in coastal waters due to such mechanisms. For the construction of an accurate beach morphological model, it is necessary to elucidate the sediment suspension and to introduce it properly into the modelling of sediment transport. Jayaratne and Shibayama (2007) developed a complete set of explicit theoretical formulae to predict the time-averaged concentration on sandy beaches due to three suspension mechanisms: a) vortical motion over wave-generated sand ripples, b) from sheet flow, and c) turbulent motion under breaking waves. The present paper focuses on the development of a quasi-3D beach deformation model using the sediment concentration models of Jayaratne and Shibayama (2007), the bed load model of Watanabe (1982), the wave propagation model of Onaka et al. (1988), the nearshore current model of Philips (1977) and the undertow model of Okayasu et al. (1990) to predict the large-scale morphodynamics of sandy beaches. The predicted beach profiles and total sediment transport rates were compared with two sets of large-scale laboratory experimental data [Kajima et al. (1983); Kraus and Larson (1988)] and Seisho beach at Kanagawa Prefecture, Japan. It can be concluded that the present numerical model is capable of predicting sediment transport direction, on-offshore sand bar formation and the general trend of the beach profiles of large-scale erosive- and accretive-type sandy beaches to a satisfactory level.
MEASUREMENT AND MODELING OF THE INFLUENCE OF GRAIN SIZE AND PRESSURE GRADIENTS ON SWASH ZONE SEDIMENT TRANSPORT
Authors: Othman Ilya Khairanis , Baldock Tom E. , Callaghan David P.
Published: December 2012

The paper examines the dependency between sediment transport rate, q, and grain size, D, (i.e. qâˆDp) in the swash zone. Experiments were performed using a dam break flow as a proxy for swash overtopping on a mobile sediment beach. The magnitude and nature of the dependency (i.e. p value) is inferred for different flow parameters; the initial dam depth (or initial bore height), do, the integrated depth averaged velocity, âˆ«u3 dt, and against the predicted transport, qp using the Meyer-Peter Muller (MPM) transport model. Experiments were performed over both upward sloping beds and a horizontal bed. The data show that negative dependencies (p0) are obtained for âˆ«u3 dt. This indicates that a given do and qp transport less sediment as grain size increases, whereas transport increases with grain size for a given âˆ«u3 dt. The p value is expected to be narrow ranged, 0.5â‰¤ pâ‰¤-0.5. A discernible difference observed between the measured and predicted transport on horizontal and sloping beds suggests different modes of transport. The incorporation of a pressure gradient correction, dp/dx, using the surface water slope (i.e. piezometric head), in the transport calculation greatly improved the transport predictions on the horizontal bed, where dp/dx is positive. On average, the incorporation of a pressure gradient term into the MPM formulation reduces qp in the uprush by 4% (fine sand) to 18% (coarse sand) and increases qp over a horizontal bed by 1% (fine sand) to two orders of magnitude (coarse sand). The measured transport for fine and coarse sand are better predicted using MPM and MPM+dp/dx respectively. Poor predictions are obtained using Nielsen (2002) because the pressure gradient in the uprush is of opposite sign to that inferred from velocity data in that paper. It is suggested that future swash sediment transport models should incorporate the grain size effect, partly through the pressure gradient, although the dp/dx influence is small for fine sands because of the grain size scaling contained in the stress term.
LITTORAL TRANSPORT MODELING FOR OCEAN BEACH AND SAN FRANCISCO BIGHT, CALIFORNIA
Authors: Lin Lihwa , Li Honghai , Wu Frank , Andes Lisa
Published: December 2012

This paper presents the littoral sediment transport numerical modeling effort of simulating physical processes of high energy coastline, including inlet and coastal zone, at Ocean Beach and San Francisco Bight, California. The study site is dominated by strong tidal current and breaking wave-induced longshore current. The numerical models for waves, currents, water levels, and sediment transport are provided by the Coastal Modeling System developed at the US Army Engineer Research and Development Center. The water level, current, wave, sediment, and bathymetric data collected by the US Army Engineer District, San Francisco, and USGS in recent years are assembled and utilized for model calibration and validation. One main effort of the study is to demonstrate the beneficial use of dredged clean material from the ship channel maintenance for onshore beach nourishment and nearshore berm placement at Ocean Beach to remediate the chronicle erosion threatening the structural integrity of the adjacent Great Highway. The modeling effort is intended to guide future dredging activities, dredged material placement site selection and evaluation, beneficial use of dredged material for nearshore and onshore beach nourishment for shore and beach protection. The model result can support and improve decision making for regional and local sediment management, enhance cross-mission benefit, and ultimately reduce the dredging project life-cycle costs.
WHAT DETERMINES THE WAVELENGTH OF SELF-ORGANIZED SHORELINE SAND WAVES?
Authors: Falqués Albert , Van den Berg Niels , Ribas Francesca , Caballeria Miquel
Published: December 2012

Shoreline undulations extending into the bathymetric contours with a length scale larger than that of the rhythmic surf zone bars are referred to as shoreline sand waves. Many observed undulations along sandy coasts display a wavelength in the order 1-7 km. Several models that are based on the hypothesis that sand waves emerge from a morphodynamic instability in case of very oblique wave incidence predict this range of wavelengths. Here we investigate the physical reasons for the wavelength selection and the main parametric trends of the wavelength in case of sand waves arising from such instability. It is shown that the existence of a minimum wavelength depends on an interplay between three factors affecting littoral drift: (A) the angle of wave fronts relative to local shoreline, which tends to cause maximum transport at the downdrift flank of the sand wave, (B) the refractive energy spreading which tends to cause maximum transport at the updrift flank and (C) wave focusing (de-focusing) by the capes (bays), which tends to cause maximum transport at the crest or slightly downdrift of it. Processes A and C cause decay of the sand waves while process B causes their growth. For low incidence angles, B is very weak so that a rectilinear shoreline is stable. For large angles and long sand waves, B is dominant and causes the growth of sand waves. For large angles and short sand waves C is dominant and the sand waves decay. Thus, wavelength selection depends on process C, which essentially depends on shoreline curvature. The growth rate of very long sand waves is weak because the alongshore gradients in sediment transport decrease with the wavelength. This is why there is an optimum or dominant wavelength. It is found that sand wave wavelength scales with Î»0/Î² where Î»0 is the water wave wavelength in deep water and Î² is the mean bed slope from shore to the wave base.
LONG-TERM NEARSHORE BATHYMETRY EVOLUTION FROM VIDEO IMAGERY: A CASE STUDY IN THE MIYAZAKI COAST
Authors: Liu Haijiang , Arii Makoto , Sato Shinji , Tajima Yoshimitsu
Published: December 2012

A four-year evaluation of the nearshore morphology based on video imagery was conducted in the Miyazaki coast, Japan. An automatic nearshore bathymetry mapping technique was developed based on the linear wave dispersion relationship, in which the wave phase velocity was estimated from the cross-correlation of neighboring pixels' brightness time series. Bathymetry estimation was carried out at both low and high tide levels of each day and integrated over a 7-day period which includes both the neap and spring tides. Model validation shows the present technique reproduced the ground truth data fairly well with a bias generally less than 0.3 m in the surf zone. In total, 88 bathymetry data were obtained within the investigation period. Subsequently, a two dimensional Empirical Orthogonal Function (EOF) analysis was applied to the time series of the obtained nearshore bathymetry data in order to investigate their long-term morphological behavior. Results from the first three modes of the EOF analysis represent the bathymetry variation from the nearshore response due to the cross-shore processes. The first mode reveals the coastal erosion occurred during the study period with a net loss of sand volume in the target region. Erosion was severe before December 2008, especially in the offshore region, and mitigated afterwards resulting a relatively equilibrium stage for the mean beach profile. The second mode shows the mean beach profile rotated in an anti-clockwise direction around a cross-shore location of 50 m away from the present shoreline, which led to a milder beach slope in the study period. The third mode represents the cross-shore movement of the longshore bar. Higher modes of the EOF analysis, such as fourth, fifth and sixth modes, correspond to the bathymetry variation due to the longshore sediment movement which frequently changed its direction as indicated from a number of nodal points in the relevant temporal eigenfunction distribution. Based on the EOF analysis, it is also confirmed that the nearshore morphological process in the target area was predominant by the cross-shore sand movement.
PREDICTION OF BEACH EROSION CAUSED BY REDUCTION OF FLUVIAL SAND SUPPLY DUE TO EXCESS SAND MINING AND BEACH RECOVERY AFTER PROHIBITION OF MINING
Authors: San-nami Toshiro , Uda Takaaki , Ohashi Norikazu , Iwamoto Hitoshi , Serizawa Masumi , Ishikawa Toshinori , Miyahara Shiho
Published: December 2012

Long-term topographic changes since 1968 along the entire Shizuoka and Shimizu coasts including a 17 km stretch extending between the Abe River mouth and the tip of the Mihono-matsubara sand spit were investigated. Beach erosion of these coasts was triggered by the decrease in sediment supply from the Abe River due to excessive riverbed mining until 1967. After 1982/1983, natural sand supply from the river increased and accretion occurred on these coasts. Measured topographic changes were reproduced using the contour-line-change model considering changes in grain size. Not only the movement of the sand body but also the shoreline and bathymetric changes were numerically reproduced. The calculated results were in good agreement with the measured topographic changes.
FIELD INVESTIGATION OF SIZE DISTRIBUTION OF SUSPENDED SEDIMENT USING LISST-100
Authors: Kuriyama Yoshiaki , Suzuki Takayuki , Yanagishima Shin-ichi , Uzaki Ken-ichi , Ishino Yoshio , Sakamoto Hikari
Published: December 2012

To investigate size distributions of suspended sediments in the surf zone, a field measurement using LISST (Laser In-Situ Scatter and Transmissometer) was conducted at Hasaki, Japan. The time series of suspended sediment concentration (SSC) for a grain size in the sand range (63 to 500 ï­m) had strong correlations with those for other sand grain sizes, and the strong correlations were also observed in the silt range (2.5 to 28 ï­m). However, at zero time lag, the time series of SSC for sand grain sizes had little correlations with those for silt sizes. With considering time lag, the time series of SSC for sand sizes had weak correlations with those for silt sizes, but which time series lagged behind the others, sand particles or silt particles, was not clear. When the total SSC CLISST was larger than 0.2 g/l, the median sediment diameter d50 was scattered around 185 ï­m. However, at CLISST < 0.2 g/l, d50 increased as CLISST increased. With the increase in d50 from 150 to 200 ï­m, the sorting coefficient decreased from 2.4 to 1.2 and the skewness increased from 0.7 to 1.0.
EVALUATION OF NOURISHMENT SCHEMES BASED ON LONG-TERM MORPHOLOGICAL MODELING
Authors: Grunnet Nicholas , Kristensen Sten Esbj¸rn , Dr¸nen Nils , Deigaard Rolf , Tessier Caroline , Forain Nicolas
Published: December 2012

A recently developed long-term morphological modeling concept is applied to evaluate the impact of nourishment schemes. The concept combines detailed two-dimensional morphological models and simple one-line models for the coastline evolution and is particularly well suited for long-term simulation. This hybrid concept is here applied to study the decadal morphological evolution of several nourishment scenarios in Dunkirk, France. The morphological simulations successfully allowed identifying the impact of beach versus shoreface nourishment scenarios on the background morphological behavior of the study site. This study strongly indicates that the hybrid model may be used as an engineering tool to predict shoreline response following the implementation of a nourishment project
FINAL DESIGN OF THE NAGS HEAD BEACH NOURISHMENT PROJECT USING A LONGSHORE NUMERICAL MODEL
Authors: Kaczkowski Haiqing Liu , Kana Timothy W
Published: December 2012

Nags Head, located at the northeastern part of North Carolina in the U.S., has sustained chronic erosion over the past 50 years. In 2005, Coastal Science & Engineering (CSE) was retained by the town of Nags Head to develop an interim beach restoration plan. Profile volume change was used in the planning and preliminary design of the project, and longshore and cross-shore numerical models were used in the final design to refine the preliminary nourishment plan and increase potential longevity of the project. This paper focuses on the key factors of the longshore numerical model setup for the project. These include model selection, input data and parameters, model calibration, and applications under different design alternatives. The Generalized Model for Simulating Shoreline Changes (GENESIS) was used in this study to evaluate shoreline evolution under normal wave conditions during various stages of the design life following the beach nourishment project. The model was used to identify the potential occurrence of erosional hotspots and to optimize the nourishment design so that the effects of such hotspots could be avoided or minimized where possible. Model results were also used to evaluate the impact of borrow area dredging on longshore transport in the project area and the impact of nourishment on shoaling in the adjacent inlet. The project encompasses 10.11 miles (mi) (16.28 kilometers-km) of ocean shoreline, and the design nourishment volume is based on the total permitted volume of 4 million cubic yards (cy) (3 million cubic meters-m³). [Note: As-built length was 10.0 mi and volume was 4.615 million cubic yards.] The final design has fill densities varying from north to south in relation to historical erosion rates and model projections. The average fill density is 75 cubic yards per foot (cy/ft) (188 m³/m) and ranges from 38 cy/ft to 150 cy/ft (95 m³/m to 375 m³/m). In conclusion, it is shown that the numerical model selected in this study was capable of predicting the overall performance of the large scale beach nourishment project in Nags Head as well as the performance at a particular location within or adjacent to the project, and its design methods can offer guidance to future projects.
NUMERICAL SIMULATION OF THREE-DIMENSIONAL SEGMENTATION OF ELONGATED WATER BODY USING BG MODEL
Authors: Uda Takaaki , Serizawa Masumi , Miyahara Shiho
Published: December 2012

In a slender water body with a large aspect ratio, the angle between the direction normal to the shoreline and the wave direction exceeds 45°, resulting in the emergence of cuspate forelands and the subdivision of a lake, because wind fetch along the principal axis becomes long. In this study, the BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept) was applied to this problem. The 3-D subdivision process of a long slender water body was predicted.
MODELLING OF THE IMPACT OF A WAVE FARM ON NEARSHORE SEDIMENT TRANSPORT
Authors: Gonzalez Raul , Zou Qingping , Pan Shunqi
Published: December 2012

This paper presents the results from an integrated modelling system investigating the effects of a wave farm on nearshore sediment transport. Wave Hub project is a large scale demonstration site for the development of the operation of arrays of wave energy generation devices located at the southwest coast of the UK where multiple field measurements took place. The two-way coupled SWAN and ROMS models with nested modelling system were set up at the Wave Hub site and run with and without a wave farm. The model results show that the presence of the wave farm has significant impacts on the nearshore circulation, bed shear stresses and sediment transport. The morphological changes are also altered by the wave farm. The study is the key element for the wave resource characterization and environmental impact assessment of the wave farm.
TWEED RIVER ENTRANCE AND BYPASS SEDIMENT DYNAMICS
Authors: Cox Ron , Howe Daniel
Published: December 2012

A sediment budget analysis model was applied to the Tweed River entrance, and was used to evaluate different coastal management scenarios. Construction of training walls at the Tweed River entrance resulted in the accretion prior to 1994 of an estimated 7 million m3 along Letitia Spit, New South Wales (to the south), and erosion of beaches at the Gold Coast, Queensland (to the north). The Tweed River Entrance Sand Bypassing Project (TRESBP) was established in 1994 and is responsible for bypassing sand from south to north, through dredging campaigns and a permanent bypass jetty. The Inlet Reservoir Model was developed by Kraus (2000) as a tool to analyse morphology changes at inlets. The inputs for the model were the estimated monthly longshore sediment transport rate, and the monthly pumping and dredging volumes from the TRESBP. Side-scan sonar surveys of the entrance bathymetry were used to validate the model over the period from 2000 to 2009. The validated model was used to examine bypass pumping strategies to manage the Letitia and Gold coast beaches, maintain navigability and minimise dredging costs. According to the model results, annual bypass pumping needs to be less than 325,000 m3 to manage the recovery of the Letitia Spit shoreline, and annual dredging of approximately 125,000 m3 is required to maintain full navigability in the Tweed River entrance.
THE BRANCHING CHANNEL NETWORK IN THE YANGTZE ESTUARY
Authors: Wang Zheng Bing , Ding Pingxing
Published: December 2012

The channels in the Yangtze Estuary have an ordered-branching structure: The estuary is first divided by the Chongming Island into the North Branch and the South Branch. Then the South Branch is divided into the North Channel and South Channel by the Islands Changxing and Hengsha. The South Channel is again divided into the North and South Passage by the Jiuduansha Shoal. This three-level bifurcation and four-outlet configuration appears to be a natural character of the estuary, also in the past (Chen et al., 1982), although the whole system has been extending into the East China Sea in the southeast direction due to the abundant sediment supply from the Yangtze River. Recently, the natural development of the system seems to be substantially disturbed by human interferences, especially the Deep Navigation Channel Project. For the understanding of the behaviour of the bifurcating channel system in the estuary we present analysis on two aspects: (1) the equilibrium configuration of river delta distributary networks, and (2) influence of tidal flow on the morphological equilibrium of rivers. Based on the analyses we conclude that the branching channel structure of the Yangtze Estuary can be classified as tide-influenced river delta distributary networks. Its basic structure is the same as in case of river dominated delta. The empirical relations describing the basic features of the river-dominated distributary delta networks can be explained by theoretical analysis, although they are not fully satisfied by the Yangtze Estuary because of the influence of the tide. Two major influences of the tide are identified, viz. increasing the resistance to the river flow into the sea and increasing the sediment transport capacity. As consequence of these two influences the cross-sectional area of the river/estuary increases in the seawards direction and the bed slope decreases. The insights from the analyses are helpful for the understanding of the impact of the Deep Navigation Channel Project on the large scale morphological development of the estuary.
LONG TERM EVOLUTION OF BALTIC SEA SANDY BEACH FORCED BY WINTER NORTH ATLANTIC OSCILLATION (NAOWI)
Authors: Grzegorz Rozynski , Szmytkiewicz Piotr
Published: December 2012

The study examines a hypothesis on the coupling between Winter North Atlantic Oscillation (NAOWI) and hydro- and morphodynamics of a sandy beach with multiple bars, situated at a Baltic Sea coastal segment in northern Poland. Identification of coincident long-term periodic patterns of shoreline variability and NAOWI is a strong argument for the existence of such a coupling, because the Baltic Sea is purely non-tidal and shoreline evolution is driven entirely by waves. Interestingly, similar periodic patterns were also found in the reconstructed long-term winter wave climate (hourly retrieved significant wave height between 1958 - 2001). Therefore, the hypothesis received a strong and comprehensive statistical footing. It highlights the fact that long-term periodic changes in winter energy fluxes from air through waves to the beach remain imprinted in shoreline evolution. Hence, any climate change driven modifications of global meteorological patterns, such as NAOWI, may have vital implications for Baltic Sea beaches in coming decades.
OFFSHORE SAND DISCHARGE CAUSED BY CONSTRUCTING COASTAL STRUCTURES ON A STEEP COAST WITH A LARGE SHORELINE CURVATURE
Authors: Miyahara Shiho , Uda Takaaki , Serizawa Masumi , Watanabe Shusuke
Published: December 2012

A groin or a detached breakwater was installed at a cuspate foreland formed on a coast with an abrupt change in coastline orientation and the effect of obstructing longshore sand transport was investigated. The results of the experiment were reproduced using the BG model (a 3-D model for predicting beach changes based on Bagnold's concept). The beach changes around the structures installed at the cuspate foreland were successfully predicted and the experimental and numerical results were in good agreement. The differences between the effects of the groin and detached breakwater in controlling longshore sand transport and the offshore sand discharge caused by constructing such coastal structures on a steep coast were successfully explained.
THE INFLUENCE OF CALCARENITE LIMESTONE REEFS ON BEACH EROSION AND RECOVERY, FROM SECONDS TO YEARS
Authors: Gallop Shari L. , Bosserelle Cyprien , Pattiaratchi Charitha B. , Eliot Ian , Haigh Ivan D.
Published: December 2012

Mechanisms through which natural rock and coral landforms interact with waves, currents, sediment transport and beach morphology are still poorly understood. Therefore, interactions between sediment transport and calcarenite limestone landforms at Yanchep Lagoon in southwestern Australia were investigated over a cascade of spatial and temporal scales: from single waves, through sea breeze and storm events, to seasonal and inter-annual variability. The hypotheses that were confirmed included: (1) hard landforms with higher elevations relative to sea level are more likely to reduce beach erosion but also to inhibit recovery; and (2) the placement and continuity of landforms in the nearshore can generate current jets, and hence local sediment sources and sinks. These hypotheses were consistently confirmed at all scales, however results show that to fully explain changes at broader scales (such as inter-annual and seasonal changes) an understanding at finer scales (such as during sea breezes, storm event and single waves) was necessary.
USE OF DIGITAL HOLOGRAPHIC CAMERAS TO EXAMINE THE MEASUREMENT AND UNDERSTANDING OF SEDIMENT SUSPENSION IN THE NEARSHORE
Authors: Conley Daniel , Buscombe Daniel , Nimmo-Smith Alex
Published: December 2012

We present results from a 3-week field experiment measuring surf-zone flows and sediment transport on a steep energetic beach in the south-west UK, including the first reported deployment of an in-line holographic camera ('holocam') in the surf zone, co-located with various optical backscatter sensors and an acoustic backscatter sensor (ABS). The extensive data set provides perhaps a unique opportunity to examine the performance of optical and acoustic backscatter instruments in a wide range of conditions including bubbly flows, as well as some fundamental aspects of sediment suspension processes such as the near-bed size-distribution of suspended sediment. The holocam, deployed with a 1.3cm cubic sample volume approximately 10cm above the bed, provides in-focus well-resolved images of the instantaneous suspended load, making it possible to determine highly-accurate estimates of the concentrations of mineral sand grains, bubbles and organic particles, and their size distributions. Instantaneous estimates of sediment concentration from the ABS compare poorly with the equivalent measure from the holocam. This could be due to various factors such as spatial decorrelation or acoustic insensitivities at larger grain sizes. However, the ABS does a very good job at estimating burst-averaged suspended sediment concentrations when bubble concentrations are low (less than 1ml/l). The error in ABS concentrations (as compared against holocam) appears to be related to relative bubble concentration. The OBS is even more sensitive to bubbles. Suspended sediment grain size distribution is skewed towards the finer grain sizes but shifts to the larger sizes with increased flow intensity.
BEHAVIOR OF THE BEACHES ON THE NORTH OF SPAIN
Authors: Lechuga Antonio , De la Peña Jose , Anton Ana , Diez Galo
Published: December 2012

This study is an analysis about morphological problems, due to anthropic or other causes. We carried out the behavior and evolution of ten beaches on the North Coast of Spain, in order to see if climate change was involved. To do this, it was necessary to consider data from Cantabrian sea buoys during fifteen years. Besides we made use of, maps, nautical charts and bathymetric records. We applied a kind of parameters to measure the energy including on each beach, so to be able to compare therm.
INFLUENCE OF INLET / SHOAL COMPLEX ON ADJACENT SHORELINES VIA INLET SINK METHOD
Authors: Legault Kelly Rankin , Beck Tanya , Engle Jason
Published: December 2012

The region of influence of the inlet on the adjacent shoreline was determined via examination of the inlet's net sink effect. The net sink effect, or volumetric impact, was computed by adding the volume (or rate) of net sand accumulation within the inlet's channels and shoals with the cumulative volumetric losses on adjacent shorelines to conserve sediment mass after accounting for the volumes either added to adjacent beaches or removed from the ebb shoal by means of nourishment and sediment mining. Volume change of the beaches and ebb shoal complex was computed within a geospatial framework consisting of Regional Mapping and Analysis Program (RMAP), ArcGIS and the Surface-water Modeling System (SMS). Inlet-adjacent cumulative volume changes were then examined to discern the minimum distance away from the inlet along which this volumetric impact was manifest. The alongshore influence of the inlet as determined by the inlet sink method for the 1999-2010 time period was found to be 7.4 miles to the north and 5.5 miles to the south. The inlet sink effect for St. Augustine Inlet is 278,000 cu yd/year, balanced by 99,000 cu yd/yr of erosion from the north beaches and 179,000 cu yd/yr of erosion from the south beaches. If managed properly, the inlet could serve as a valuable, long-term resource for the beaches of St. Johns County within the bounds of its sink effect.
PREDICTION OF BEACH CHANGES AROUND ARTIFICIAL REEF USING BG MODEL
Authors: Fujiwara Hiroaki , Uda Takaaki , Onishi Toshiaki , Miyahara Shiho , Serizawa Masumi
Published: December 2012

On the Kaike coast, one of the twelve detached breakwaters was converted into an artificial reef. After the conversion, the tombolo behind the structure was reduced in size because of the generation of shoreward currents on the artificial reef, and severe scouring occurred at the opening between the artificial reef and the existing detached breakwater owing to the development of rip currents. To investigate this, the BG model (a 3-D model for predicting beach changes based on Bagnold's concept) proposed by Serizawa and Uda was improved to include the effect of not only waves but also strong nearshore currents. Also, the increase in the depth of closure due to currents was considered in the model. The predicted and measured beach changes around an artificial reef were in good agreement.
FIELD MEASUREMENTS OF SHEET FLOW SEDIMENT TRANSPORT IN THE SWASH ZONE
Authors: Lanckriet Thijs , Puleo Jack A. , Masselink Gerd , Turner Ian , Conley Daniel , Blenkinsopp Chris , Russell Paul
Published: December 2012

A newly developed Conductivity Concentration Profiler (CCP), capable of rendering a 29-point sediment concentration profile at 1 mm vertical resolution, was deployed on a macrotidal beach in Perranporth, UK, as part of a comprehensive field study on swash zone hydrodynamics and sediment transport. Initial field results show the occurrence of sheet flow during both the uprush and backwash phases of the swash cycle. Concentration profiles in the sheet flow layer are approximately linear, with a power-law tail at the top of the layer. The data suggest that shear stresses are the dominant forcing for sediment mobilization, but pressure gradients provide a secondary mobilization mechanism.
ASSESSING SHORELINE CHANGE USING SATELLITE-DERIVED SHORELINES IN PROGRESO, YUCATÁN, MÉXICO
Authors: Garcia-Rubio Gabriela , Huntley David , Russsell Paul
Published: December 2012

Assessment of shoreline change during a six-year period using Satellite-Derived Shorelines (SDS) was carried out in Progreso, Yucatán, México. Confidence bounds for the SDS were defined based on the deviation between quasi-simultaneous in situ shoreline measurements and SDS. The main objective of this paper is to show that optical satellite images are a valuable resource to study shoreline change covering large geographical scales (>10km), as well as short (5 years) temporal scales. This approach can be particularly useful for those areas with a lack of shoreline records. The results presented here show that detection of differences between seasons and years is achievable using SDS. Furthermore, rates of change are also possible to assess.
NUMERICAL SIMULATION STUDY ON DEPOSITION DOWNSTREAM ESTUARINE SLUICE
Authors: Dou Xiping , Zhang Xinzhou , Wang Xiangming , Wang Jinhua
Published: December 2012

In order to resist tides and salt intrusion, there have been more than 300 tidal gates built at many river estuaries in China since 1960s. However, the serious deposition occurred at a lot of gates due to the changes of hydrodynamic and sediment conditions and lack of discharge from the rivers. At present, the research is mainly to analyze the reasons for siltation downstream gates and the measures of dredging. It is not enough for study on distribution simulation of deposition downstream sluice. Studies have shown that 2D numerical model cannot reflect the distribution of sediment siltation downstream gates. Therefore, it needs to develop 3D sediment numerical model for deposition prediction. In this paper, combined the feasibility study of a tidal gate at Mulanxi River, a physical model and 3D numerical model of sediment siltation downstream gate are conducted.
INFLUENCE OF DAMAGED GROINS ON NOURISHED SEASHORE
Authors: Ostrowski Rafal , Pruszak Zbigniew , Schönhofer Jan , Szmytkiewicz Marek , Szmytkiewicz Piotr
Published: December 2012

The system of timber palisade groins can be very helpful as a measure coexisting with artificial nourishment and increasing the lifetime of beach fills. To this end, good condition of groins and their permanent contact with land is necessary. On the basis of theoretical modelling and field surveys a conclusion has been formulated that coexistence of complete groins with artificial shore nourishment causes that about 30% less sediment is washed away from the nearshore zone than for beach fill without groins.
A COMPREHENSIVE SEDIMENT BUDGET FOR THE MISSISSIPPI BARRIER ISLANDS
Authors: Walstra Dirk-Jan , De Vroeg J. , Van Thiel de Vries J. , Swinkels C. , Luijendijk A. , De Boer W. , Hoekstra R. , Hoonhout B. , Henrotte J. , Smolders T. , Dekker F. , Godsey E.
Published: December 2012

In order to conceive any realistic plan for post-Katrina island restoration, it is necessary to understand the physical processes that move sand along the littoral drift zone off the coast of Mississippi. This littoral zone influences the character of the Mississippi barrier islands as they exist in an ever changing cycle. To help in this understanding, a sediment transport model was conducted to establish a current sediment budget for the islands. This study evaluated the existing regional sediment transport magnitudes and directions for the Mississippi and Alabama barrier islands fronting Mississippi Sound including daily conditions and hurricanes. A method was developed to incorporate all relevant hurricanes from 1917 to 2010 in the analysis. For the long term average net longshore transport along the southern shorelines of the barriers (i.e. exposed to the Gulf of Mexico), the contribution of year-averaged conditions and hurricanes are of similar order of magnitude, although the mean annual percentage occurrence of hurricanes is no more than about 3%. Along the northern shores (Mississippi Sound side) the transport is considerably smaller and the contributions of cold fronts and hurricanes to the sediment transports are more or less equal. For the year-averaged conditions (excluding hurricanes) a westward directed net transport is found. The net effect of the historic hurricanes is also westward in direction. However, for individual hurricanes (e.g. Camille and Katrina) the net transport along Ship Island can be directed eastward due to the dominance of ebb flows after the eye of the hurricane had passed.
SPATIOTEMPORAL ANALYSIS OF VARIATIONS OF CERTAIN MORPHOLOGICAL BEACH FORMS
Authors: Pruszak Zbigniew , Schönhofer Jan , RóÅ¼yÅ,,ski Grzegorz
Published: December 2012

The study is focused on spatiotemporal shoreline variability at a beach with a wide surf zone featuring 3-5 bars based on field observations done between 1983-2008 in the south Baltic Sea. The implementation of various analyses from simple geometry, through spectral analysis up to Discrete Wavelet Transform (DWT) allowed for a synergistic description of simultaneous shoreline and dune foot variability in space and time. The results include meso-scale and long-term phenomena with time scales from several months to many years and spatial scales ranking between a few hundred meters up to several kilometers.
CONTRASTING STORM IMPACTS ON GRAVEL BEACHES - EXAMPLES FROM SOUTH ENGLAND
Authors: Poate Tim , McCall Robert , Masselink Gerd , Russell Paul , Davidson Mark
Published: December 2012

Topographic surveys are used to assess response characteristics of eight gravel beaches to storm conditions across the south of England. Using profile volumes, pre- and post-storm, from surveys undertaken within a short temporal interval a quantitative assessment of beach response to corresponding wave conditions has been undertaken. Wide disparity in site response is found with contrasting accretionary and erosive behaviour observed un-correlated with nearshore hydrodynamics. In addition predictive runup corresponds poorly with measured effective runup.
INFLUENCE OF THE WAVE REGIME IN COASTAL SEDIMENT BUDGET: PRESENT AND FUTURE SCENARIOS
Authors: Plecha Sandra , Lopes Carina L. , Bruneau Nicolas , Ribeiro Nuno A. , Silva Paulo A. , Fortunato André B. , Dias João M.
Published: December 2012

The wave regime has a strong influence on the sediment transport in coastal systems. Modifications in wave regime induced by climate changes can influence the sediment dynamics of those coastal systems. To access wave regime changes it is crucial to analyse the future modifications in the wave height, period and direction. This work aims to analyse the influence of a future wave regime in the sediment budget of a coastal lagoon inlet and at the nearshore adjacent coast. To achieve this goal a morphodynamic modelling system was used, forced by present and future waves, corresponding to a typical year of present and future wave climates. A methodology to determine a typical year of each climate was developed based on the determination of correlation coefficients between each climate and corresponding year data. The comparison between present and future wave climates evidences that wave period and height are in general similar for both climates, and confirms the anticlockwise rotation of waves in the future. The morphodynamic simulations revealed analogous results for both wave climates, resulting in similar patterns for the residual sediment fluxes, but slightly more intense in the present. The consequent bathymetric changes show that the deposition trend presently observed offshore the inlet tends to increase for future waves climate. The transport budgets were also analysed for both wave regimes, evidencing that the alongshore transport slightly decreases (~1%) for future waves.
MORPHOLOGICAL MODELLING OF THE RESPONSE TO A SHIPWRECK - A CASE STUDY AT CAPE TOWN
Authors: Kristensen Sten Esbj¸rn , Deigaard Rolf , Dr¸nen NIls , Fredsoe J¸rgen , Luger Stephen
Published: December 2012

A simulation of the morphological development and degrade of a salient behind a shipwreck located north of Cape Town, South Africa is presented. The morphological model is based on a hybrid morphological model concept which combines a 2D coastal model for calculating sediment transport with a simplified 1D morphological evolution model for the coastline. The model concept is applied to the case study in order to show how the modelling concept may be applied to real coastlines with general bathymetric features. The results show that the model captures the overall morphological response fairly well without the need for extensive calibration which is often required by traditional 2D morphological models. This is attributed by the authors to the fact that the sediment transport description is based on a process based model that captures the most important features, while neglecting the often challenging description of the cross-shore sediment transport.
DEPTH OF CLOSURE DETERMINATION IN THE VICINITY OF COASTAL STRUCTURE
Authors: Widyaningtias Widyaningtias , Tanaka Hitoshi , Kanayama Susumu
Published: December 2012

This study is conducted to analyze the effect of coastal structure to depth of closure variation. Analysis on time series bathymetry data has been applied to determine location of depth of closure. The deviation of bathymetry profile changing is also considered. Furthermore, longshore variation of depth of closure is proposed. The hydrodynamic conditions are simulated using Boussinesq model derived by Peregrine (1967). This model is applied considering its applicability to observe non-linear and dispersion phenomenon while wave propagates to the shoreline. The simulation is carried out under regular wave assumption with 20% wave height in deep area is applied as representative wave. The simulation results are obtained in term of surface water level, bottom velocity in x and y direction and current velocity. The result is utilized to calculate maximum bottom velocity just outside boundary layer. To observe sediment movement along the coast, maximum shear stress is calculated under wave-current combined motion. Dimensionless Shields parameter is also assessed. The simulation results are depicted in spatial map. Furthermore, the effect of coastal structure to depth of closure variation is confirmed using hydrodynamic conditions.
METHOD TO PREDICT LONG TIME SPAN OF SCOUR AROUND OFFSHORE WIND TURBINE FOUNDATIONS
Authors: Dixen Martin , Lohmann Iris Pernille , Christensen Erik Damgaard
Published: December 2012

A new method to predict scour development around offshore structures has been developed. The method has been tested on a monopile. The method consists of table of scour rates, which is used to predict the scour development around the structure at different stages of the scour hole. The scour rate tables have been made based on full 3D numerical simulations of the flow and sediment transport for fixed configurations of the scour hole. When changing the governing parameters which are causing the scour development around the structure, the erosion rate or backfilling rate can be calculated from the mass balance of the sediment. This leads to the scour rates tables that are used to analyses the development of the scour hole under different current conditions. The method has been tested against experimental scour data and showed very promising results.
INTERTIDAL FINGER BARS AT EL PUNTAL SPIT, BAY OF SANTANDER, SPAIN
Authors: Garnier Roland , Medina Raúl , Pellón Erica , Falqués Albert , Turki Imen
Published: December 2012

We indentify the presence of an intertidal finger bar system in the swell-protected beaches of El Puntal Spit (Bay of Santander, Spain). The Horus video monitoring system allows us to perform a 2 year survey (June 2008- June 2010). We found that the bar system persists during the survey period with a wavelength of about 25 m and an oblique orientation with respect to the shore. Moreover, the analysis of the position of a particular bar (Bar 10) shows a movement characterized by a net migration to the west and a faster oscillation to the east or the west. Preliminary climate data analysis and morphological model results show that tide seems to be a forcing in the motion of the bars but also wind and waves generated by the wind probably affects the bar dynamics.