David J. Hanslow

Wave Setup at River Entrances

A study of alternatives including a shoreline evolution numerical modelization has been carried out in order to both diagnose the erosion problem at the beaches located between Cambrils Harbour and Pixerota delta (Tarragona, Spain) and select nourishment alternatives.

WATERTABLE OVERHEIGHT DUE TO WAVE RUNUP ON A SANDY BEACH

A special reflecting wall 12 m long and 2.1 m high was built off the beach at Reggio Calabria, and 30 wave gauges were assembled before the wall and were connected to an electronic station on land. It was possible to observe the reflection of wind waves generated by a very stable wind over a fetch of 10 Km. The experiment aimed to verify the general closed solution for the wave group mechanics (Boccotti, 1988, 1989), for the special case of the wave reflection.Significant features on Wadden Sea wave climate are evaluated in respect of the state of the art. Main emphasis was laid on an analysis of the governing boundary conditions of local wave climate in island sheltered Wadden Sea areas with extensions being sufficient for local wind wave growth. Explanatory for significant wave heights a reliable parametrization of local wave climate has been evaluated by using generally available data of water level and wind measurements.

Extreme coastal erosion enhanced by anomalous extratropical storm wave direction

Extratropical cyclones (ETCs) are the primary driver of large-scale episodic beach erosion along coastlines in temperate regions. However, key drivers of the magnitude and regional variability in rapid morphological changes caused by ETCs at the coast remain poorly understood. Here we analyze an unprecedented dataset of high-resolution regional-scale morphological response to an ETC that impacted southeast Australia, and evaluate the new observations within the context of an existing long-term coastal monitoring program. This ETC was characterized by moderate intensity (for this regional setting) deepwater wave heights, but an anomalous wave direction approximately 45 degrees more counter-clockwise than average. The magnitude of measured beach volume change was the largest in four decades at the long-term monitoring site and, at the regional scale, commensurate with that observed due to extreme North Atlantic hurricanes. Spatial variability in morphological response across the study region was predominantly controlled by alongshore gradients in storm wave energy flux and local coastline alignment relative to storm wave direction. We attribute the severity of coastal erosion observed due to this ETC primarily to its anomalous wave direction, and call for greater research on the impacts of changing storm wave directionality in addition to projected future changes in wave heights.

MEASURING WAVES WITH MANOMETER TUBES

A special reflecting wall 12 m long and 2.1 m high was built off the beach at Reggio Calabria, and 30 wave gauges were assembled before the wall and were connected to an electronic station on land. It was possible to observe the reflection of wind waves generated by a very stable wind over a fetch of 10 Km. The experiment aimed to verify the general closed solution for the wave group mechanics (Boccotti, 1988, 1989), for the special case of the wave reflection.Significant features on Wadden Sea wave climate are evaluated in respect of the state of the art. Main emphasis was laid on an analysis of the governing boundary conditions of local wave climate in island sheltered Wadden Sea areas with extensions being sufficient for local wind wave growth. Explanatory for significant wave heights a reliable parametrization of local wave climate has been evaluated by using generally available data of water level and wind measurements.

Regional Scale Coastal Mapping to Underpin Strategic Land Use Planning in Southeast Australia

ABSTRACT Hanslow D.J.; Dela-Cruz J.; Morris B.D.; Kinsela M.A.; Foulsham E.; Linklater M., and Pritchard T.R., 2016. Regional scale coastal mapping to underpin strategic land use planning in southeast Australia. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 987–991. Coconut Creek (Florida), ISSN 0749-0208. In the current study we develop spatial data to inform strategic land use and coastal planning which considers coastal hazards and the protection, maintenance and in some cases, restoration of our waterways. The benefits of sustainable coastal development underpinned by a well-established understanding of coastal processes and our ability to avoid negative impacts from inappropriate placement of development are well understood. With climate change and increasing use of coastal systems there is increasing need to identify and manage both current and possible future risk exposure. Mapping is undertaken to allow upfront identification of risks and benefits associated with potential future land use as well fundamental data to help inform coastal assessments. This will help ensure impacts on the coastal environment are minimised and impacts on proposed development from coastal hazards are avoided. The study has several parallel components addressing estuarine water quality and ecosystem health, sea level rise inundation, coastal erosion and sediment/geomorphic setting. Additional benefits of the project include risk based assessment to enable prioritisation of effort to address existing development which is either exposed to coastal hazards or having an impact on coastal waterways.

A Flexible Approach to Forecasting Coastline Change on Wave-Dominated Beaches

ABSTRACT Kinsela, M.A., Morris, B.D., Daley, M.J.A. and Hanslow, D.J., 2016. A Flexible Approach to Forecasting Coastline Change on Wave-Dominated Beaches. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 952–956. Coconut Creek (Florida), ISSN 0749-0208. Standard methods of predicting coastline change typically rely on the analysis and extrapolation of historical trends, or simple geometric rules that consider the response of idealised coastal morphology to environmental change – e.g. the Bruun rule of coastline retreat due to sea level rise. In practice, predictions based on such methods are often challenged, due to the limited capacity to characterise natural geomorphic complexity, and consequently, the inability to satisfy restrictive assumptions. While statistical simulation methods offer a means to manage uncertainty in environmental forcing, datasets, and predictive models, the continued reliance on simple geometric rules introduces unnecessary error into forecasts. The increasing coverage and detail of geomorphic datasets, provided by modern remote sensing techniques (e.g. LiDAR, GPR), means that more rigorous approaches are now achievable in many settings. This paper presents a simple yet flexible approach to forecasting coastline change on wave-dominated beaches. The method combines a Monte Carlo simulation approach with a volumetric coastline response model that features a parameterised sediment budget. Model complexity reflects the levels of topographic and geomorphic data typically available for beaches in southeastern Australia, allowing for the sediment budget parameterisation to be broad or refined. A volumetric implementation of all components of coastline variability and change ensures that forecasts are sensitive to the complex coastal geomorphology of individual beaches. Application of the method demonstrates the sensitivity of forecast coastline change to three-dimensional beach and dune morphology, irregular substrates comprising mixed hard and soft materials, and complex shoreface surfaces featuring submerged reef structures.

WAVE SETUP AND OTHER TIDAL ANOMALIES IN COASTAL RIVERS

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.

Evaluation of Runup Characteristics on the NSW Coast

ABSTRACT Morris, B.D., Foulsham, E., Laine, R., Wiecek, D. and Hanslow, D., 2016. Evaluation of run-up characteristics on the NSW coast. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1187–1191. Coconut Creek (Florida), ISSN 0749-0208. Communities and infrastructure along the coast of New South Wales, Australia, are vulnerable to coastal inundation from the combined impacts of ocean tides, storm surge, wave setup, wave run-up and wave overtopping. The focus of the current work is to examine the potential for coastal inundation on beaches and dunes on the open coast of NSW through the evaluation of wave run-up. To achieve this we combine information on tides, surge and wave runup to examine dune overtopping potential. The study utilises data from the NSW wave and ocean tide gauge network and an extensive set of beach profile and grainsize data covering over 200 beaches as well as available photogrammetry and LiDAR data. Ocean still water level and design nearshore wave conditions are used together with beach slope data to calculate wave run-up height. Choice of appropriate wave run-up formulation is evaluated through the use of available long term datasets from Narrabeen and Moruya. Geographical variability in relevant beach/dune characteristics including beach slope and dune height are examined using survey (RTK-GPS), photogrammetry and LiDAR data. Overtopping potential for various design events (e.g. 5y, 20y, 100y storms) is examined through the overlay of predicted run-up heights on high resolution digital elevation models at each pilot study site.

A Regional Scale Approach to Assessing Current and Potential Future Exposure to Tidal Inundation in Different Types of Estuaries

Broad scale assessments of impacts associated with sea level rise have mainly been undertaken using ocean water level data from tide gauges located in harbours and ports assuming that these can be applied directly in mapping inundation throughout estuaries. On many coasts, however, exposure to sea level rise comes about through inundation adjacent to rivers and estuaries, in many instances far from the ocean. In this study, we examine the potential impacts of sea level rise within the diverse estuaries of South East Australia. We use an extensive and long-term water level data set, which show that water levels within the different types of estuaries vary from ocean water levels. We map potential inundation scenarios for each estuary using an approach which improves on the commonly used bath tub method by allowing for variation in tidal processes both between and along estuaries. We identify considerable exposure to future sea level rise, and variable suitability of the bath tub method within different estuaries. Exposure is particularly high around tidal lake systems, where reduced tidal ranges have allowed development to occur in relative proximity to present sea level, and around larger coastal rivers, which feature extensive low-lying plains exposed to potential inundation.

Impact of river training walls on adjacent beaches, Ballina, New South Wales, Australia

River and inlet training walls have been built at scores of locations along the NSW coast. This study examines the impact of training walls built at the Richmond River mouth, Ballina, over the period 1889 to 1991 on the adjacent beach systems. GIS analysis of 2 bathymetric maps and photogrammetric analysis of 6 aerial photo sets were used. The position of the shoreline and contours and their temporal changes for each profile were determined to identify accretional and erosional patterns. Spatial variations in the pattern were then used to assess the impact of training walls.The impact of training wall can be divided into three types: (1) accretion in updrift and erosion in downdrift; (2) accretion on both sides of the training wall, and (3) accretion on both sides near the training wall, but erosion on both sides away from the training wall. South Ballina beach and Lighthouse beach exemplify the second type. The impact of training wall varies linearly with the distance from the wall.