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The influence of the El Niño-Southern Oscillation (ENSO) on NSW coastal storm severity was investigated by comparing the yearly mean Southern Oscillation Index, SOI, with the yearly averaged storm severity Ω measured at the NSW coast. It was found that Ω correlates well with SOI, i.e., Ω generally increases with SOI. The probability distributions of storm peak wave height and yearly mean SOI were also studied and were found to follow a Gumbel distribution. A simple linear relationship between extreme wave height and yearly mean SOI was then derived. At the NSW coast or at other coasts with similar wave climates, coastal recession and increased coastal damage may be expected in La Niña years, while beach recovery and reduced coastal threat may be expected in El Niño years. [ABSTRACT FROM AUTHOR]

The article discusses the bedload transport data from planebed and step pool reach types that are used to find out the grain size transport thresholds for chosen upland streams in southeast Australia. Structural deviation between the reach types let the effects of frictional losses from bedforms, microtopography and bed packing to be incorporated into the dimensionless critical shear stress value. Also included is a local sediment transport data in a regime model and applied to mountain streams to investigate whether empirical data improve the delineation of reach types on the basis of dimensionless discharge per unit width and dimensionless bedload transport.

Estuarine beaches are ubiquitous, yet understudied, coastal systems. The mixed hydrodynamic processes – such as combined tidal and wave forcing – and the influence of adjacent sedimentary features – such as flood-tide deltas (FTDs) – leads to complex morphodynamic processes. As such, the dynamics and evolution of these important coastal systems are poorly understood. This study synthesises a set of analyses conducted on an estuarine beach, in southeast Australia, over multiple temporal scales. Nearshore waves and currents were measured and used to determine the processes driving seasonal to yearly beach change between 2007 and 2010. These results were compared to decadal scale beach change determined from aerial photos between 1963 and 2006. We found the westward transport of sediment towards the inner estuary was the dominant nearshore process leading to erosion in the eastern regions of the beach (near the estuary entrance) and accretion in the west over yearly time scales. Cross-shore sediment transport occurred during winter storm swell conditions leading to erosion in more exposed sites and some limited accretion in sheltered zones, most likely due to sediment input from the flood-tide delta. However, severe storm swell events that propagated into the estuary led to a loss of sediment and erosion across the entire beach which was not recovered during the study period. It is likely that the erosion processes observed in the short- to medium-term (days to years) analyses are the conditions that led to the long-term shoreline retreat observed in the aerial photograph record. The long-term shoreline retreat since 1963 is likely a result of a negative sediment balance due to movement of the FTD and a lack of sediment input in the eastern regions of Shoal Bay. Shoreline retreat will likely continue unless increased sediment input occurs from marine sources or shoreline interventions are maintained. • Multi-scaled morphodynamics of an estuarine beach was investigated. • Beach rotation was observed driven by seasonal cross and long-shore processes. • Over 40 years of chronic storm driven erosion underlies seasonal beach dynamics. • Shoreline retreat is likely driven by a lack of sediment input from marine sources. [ABSTRACT FROM AUTHOR]

Numerical coastal erosion models are used by engineers to predict the magnitude of storm erosion at the coastline. In particular, the 'dry' region of the beach, extending landwards from the waterline to include the beach face, berm and dunes, is a particular focus of interest to managers, planners and other coastal practitioners. However, the choice of the most appropriate numerical model to predict subaerial beach erosion requires careful consideration of the strengths and limitations of each model, and the quality and quantity of field data available for both model calibration and prediction. While no model can perfectly replicate observed upper beach erosion, this study specifically assesses the quantity of field calibration data required to achieve optimum model performance for coastal storm erosion modelling applications. Two of the most commonly used, but differently formulated, coastal erosion profile models are compared: the process-based and more complex model XBeach, and the semi-empirical and significantly simpler model SBEACH. A rigorous calibration technique (the Generalised Likelihood Uncertainty Estimation) is applied to both models, using a comprehensive dataset of pre- and post-storm topographic measurements collected over four differing storm events at Narrabeen-Collaroy Beach in southeast Australia, as well as at two adjacent embayed beaches. When applying the two numerical models using their default parameters (i.e., with no model calibration), SBEACH was found to be the more skilful model and XBeach default parameters were found to have no predictive skill along this stretch of coastline. Once calibrated with detailed field observations obtained before and after a single storm event, XBeach validation skill rose considerably and provided predictions of subaerial beach profile change with greater skill (87% better Brier Skill Score on average for the same calibration data) than SBEACH. Overall XBeach model performance was found to marginally improve when field observations obtained from additional storm events were included in the calibration process, whereas SBEACH showed negligible improvement. A comparison was made of the options available for transferring previously-calibrated parameters to adjacent locations, finding spatial proximity to be the most sensitive indicator of model performance for a transferred parameter set. Due to the alongshore variability in pre-storm topography as well as wave exposure at the sites tested, the spatial coverage of data was more important for the calibration process than the magnitude of the individual storm(s) used for a specific calibration. The results of this study underscore the need for careful consideration of the available calibration field data when choosing and optimising coastal erosion models. • Default XBeach parameters were found to be non-skilful at coastal sites in southeast Australia. • The XBeach model outperformed the SBEACH model when one or more calibration storm event field datasets were available. • Collection of calibration pre- and post-storm field data at specific locations of interest was important. • Spatial proximity was found to be a good performance indicator of calibrated parameter values transferred to new locations. [ABSTRACT FROM AUTHOR]

Sennes, G., Castelle, B., Bertin, X., Mirfenderesk, H. and Tomlinson, R.B., 2007. Modelling of the Gold Coast Seaway tidal inlet, Australia. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 1086 – 1091. Gold Coast, Australia, ISSN 0749.0208 The Seaway entrance is a tidal inlet located on the Gold Coast (Queensland, Australia). Before the 80s, the entrance was highly variable in terms of inlet location and sand bar characteristics. The Seaway stabilisation with two training walls combined with an artificial sand bypassing system were completed in 1986 with the aims of fixing the entrance, maintaining a safe navigable channel, preventing shoreline erosion to the north and a buildup of sand to the south. Despite these training works, the dynamics of the Seaway is still poorly understood: channel infilling problems and navigation issues remain. For these reasons, the present study aims to develop a comprehensive model of the entrance to be used for further dredging and training work issues. The present investigation is carried out in two stages. The first stage is based on historic aerial photograph analysis of the Seaway before training works. It shows that the mouth was periodically driven northward by the longshore drift, with an average cycle time of 10 years. The second stage is based on numerical modelling after training works. Refined Delft3D modelling is undertaken with a 2DH approach on the Seaway area, taking into account the training walls and the sand bypassing system. This local model is coupled with MIKE21 implemented on a regional scale to provide accurate tide and flow forcing at the boundaries. After calibration, the analysis of flow patterns shows that the Gold Coast Seaway is ebb-dominated and that the more intense flow velocities are observed in the northern channel. Morphological evolution of the inlet is also investigated with a qualitative approach. Results indicate the pathways and rate of the sand movement within the tidal inlet in its current configuration and provide information about a planned 400 m extension of the southern training wall. A significant calibration work, involving sediment transport and bathymetry measurement, is required for the model to be used as a comprehensive tool for further dredging and dumping strategies within the entrance. [ABSTRACT FROM AUTHOR]

Kim, I.H and Lee, J.L., 2007. Changes in the sediment transport pattern after breakwater extension at Anmok Port, Korea. Journal of Coastal Research, SI 50, 1046 – 1050. Gold Coast, Australia, ISSN 0749.0208 The breakwater extension at Anmok Port has resulted in erosional stresses along the shoreline immediately south of the port. In this study, the downdrift affects caused by the breakwater extension are investigated through both analytical and numerical model approaches. The analytical approach is accomplished through littoral drift vectors which are estimated in this study from measured volumetric changes by using an inverse matrix. The model has five components including a parabolic equation for wave transformation from the deep ocean to the coastal region, depth-integrated shallow water equations for calculating coastal current, diffusion-advection equations for sediment transport and a mass conservation equation of bottom-layered sediments for predicting depth changes. Analyses of sand transport processes in the vicinity of Anmok Port resulted in the conclusion that a heavy eddy generated in a sheltered zone is the predominant erosion mechanics at the site and therefore, the bypassing system is considered as a necessary device in order to basically solve the concurrent problem such as heavy accumulation of sediments in a port entrance and the closure of a stream mouth in the east coast as well as the eroding problem. [ABSTRACT FROM AUTHOR]

Coughlan, C., Vincent, C.E., Dolphin, T.J. and Rees, J.M., 2007. Effects of tidal stage on the wave climate inshore of a sandbank. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 751 – 756. Gold Coast, Australia, ISSN 0749.0208 Modelling of the processes that link the movements of offshore sandbanks to erosion and accretion of neighbouring beaches was undertaken to improve understanding of the links between sandbanks and beaches in order to inform coastal management. The effect of varying tidal stage on the wave climate inshore of a sandbank was examined using the TELEMAC suite of numerical models. Longshore sediment transport was calculated using the CERC formula to investigate changes to the magnitude and pattern of coastal erosion/accretion according to tidal stage using waves from two of the most frequent directions. Tidal stage has a significant impact on the inshore wave climate, varying wave heights by up to 0.5 m and increasing tenfold the magnitude of the longshore sediment transport. Tidal elevation appears to play a more important role than the tidal currents, with wave heights and longshore sediment transport maximum at high water. The pattern of alongshore erosion and accretion varies more strongly with wave direction than tidal stage. [ABSTRACT FROM AUTHOR]

Vila-Concejo, A., Short, A.D., Hughes, M.G. and Ranasinghe, R., 2007. Flood-tide Delta Morphodynamics and Management Implications, Port Stephens, Australia. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 705 – 709. Gold Coast, Australia, ISSN 0749.0208 Port Stephens is a drowned river valley estuary located in SE Australia. Its flood-tide delta is part of the morphological transition between the wave-dominated open coast and the tide-dominated estuarine environment. The sand surface of the flood-tide delta is subject to episodic disturbance by large ocean waves that penetrate into Port Stephens. Moreover, the flood-tide delta is a dynamic feature that responds to variations in the forcing mechanisms. Shoal Bay, Nelson Bay and Jimmy's Beach located on both sides of the entrance have experienced severe erosion for the last 40 years, resulting in expensive shoreline management controls. The evolution of these beaches has been linked to the flood-tide delta morphodynamics. Most of the morphologic features in outer Port Stephens have undergone erosion processes during at least the last 40 years. Yacaaba Head seems to be the only morphologic unit that has undergone sedimentary accretion. Results from numerical models obtained by other authors found eastward directed sediment transport occurring on the eroding beaches. Field measurements and observations show westward sediment transport. Further studies to identify the sediment exchange mechanisms and controls are needed to clarify the morphodynamics of the outer part of Port Stephens. [ABSTRACT FROM AUTHOR]

Tsujimoto, G., Kakinoki, T., Hamaura Y., Shigematsu T. and Uno K., 2007. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 206 – 210. Gold Coast, Australia, ISSN 0749.0208 Sediment transport inside and outside a permeable submerged breakwater was examined in a laboratory experiment and a numerical calculation. The Macroscopic turbulence model, which has been applied for the thermal conduction in porous media, was used for the theoretical approach. A two- equation model for inside regions and 0- equation model was used for the outside region. Suspended sediment could be transported toward the onshore side due to two effects; vortex over sand ripples and the slope of a permeable breakwater. The amount of sediment deposited in the breakwater decreased gradually from the offshore to the onshore side during the experiment, while on the other hand decreasing rapidly in the numerical calculation. The surface profile over the submerged breakwaters could be reproduced excellently. [ABSTRACT FROM AUTHOR]