Measured probability distributions of shoreline elevation, swash height (shoreline excursion length) and swash maxima and minima from a wide range of beach types are compared to theoretical probability distributions. The theoretical distributions are based on assumptions that the time series are weakly steady-state, ergodic and a linear random process. Despite the swash process being inherently non-linear, our results indicate that these assumptions are not overly restrictive with respect to modeling exceedence statistics in the upper tail of the probability distribution. The RMS-errors for a range of exceedence level statistics (50, 10, 5, 2, and 1 percent) were restricted to <10 cm (and often <5 cm) for all of the swash variables that were investigated. The results presented here provide the basis for further refinement of coastal inundation modeling as well as stochastic-type morphodynamic modeling of beach response to waves. Further work is required, however, to relate the parameters of swash probability distributions to wave conditions further offshore.

There is growing global concern for the impact of increased fluvial sediment loads on tropical coral reefs and seagrass ecosystems. The Fitzroy River is a macrotidal, tide-dominated estuary in the dry tropics of central Queensland and is a major contributor of sediment to the southern Great Barrier Reef (GBR) lagoon. The estuary currently receives most of its sediment during large episodic flood events commonly associated with cyclonic depressions. The sediment dynamics of macrotidal estuaries and especially of wet-dry tropical systems, with intermittent flows and sediment discharge are poorly understood. Average annual sediment budgets for such a system are also difficult to estimate due to the sporadic nature of flood discharge events. Therefore we have estimated a long-term sediment accumulation rate of catchment-derived sediment trapped in the estuary using the Holocene stratigraphic sequence, determined from a series of sediment cores, dated with radiocarbon and optically stimulated luminescence (OSL), and integrated with industry borehole data. We estimate that 17,400 million tonnes (Mt) of river sediment has accumulated in the estuary during the last 8000 years. This suggests a minimum mean annual bulk sediment discharge of the Fitzroy River of 2000 kt yr-1. This estimated 2175 kilotonnes per year (kt yr-1) of bulk sediment is equivalent to 25% of the estimated average annual modern bulk sediment discharge of the Fitzroy River of 8800 kt yr-1, (Kelly and Wong, 1996) suggesting that the sediment trapping efficiency of the Fitzroy estuary during the Holocene has been approximately 25%. This implies that 75% of the river sediment has been exported from the estuary into Keppel Bay and the adjacent GBR lagoon during the Holocene. With minimal accommodation space left in the floodplain, modern sediment accumulation appears to be focussed around the mangroves and tidal creeks, which cover an area of 130 km2. Cores from the tidal creeks were dated using 137Cs, excess 210Pb, and OSL and display sedimentation rates of approximately 1.5 cm yr-1 for the last 45-120 years, or 1700 kt yr-1, and suggest a modern sediment trapping efficiency for the estuary of around 19%. These results provide useful insights into the long-term sedimentation and quantification of the sediment trapping efficiency of a subtropical macro-tidal estuary with episodic floods, where sediment trapping will vary seasonally and inter-annually.

The Australian Government, through the Department of Climate Change and Energy Efficiency, recognises the need for information that allows communities to decide on a strategy for climate change adaptation. A first pass national assessment of vulnerability to Australia's coast identified that considerable sections of the coast could be impacted by sea level rise. This assessment however, did not provide sufficient detail to allow adaptation planning at a local level. Accounting for sea level rise in planning procedures requires knowledge of the future coastline, which is still lacking. Modelling the coastline given sea level rise is complex, however. Erosion will alter the shores in varied ways around Australia's coastline, and extreme events will inundate areas that currently appear to be well above the projected sea level. Moreover, the current planning practice of designating zones with acceptable inundation risk is no longer practical when considering climate change, as this is likely to remain uncertain for some time. Geoscience Australia, with support from the DCCEE, has now conducted a more detailed study for a local area in Western Australia that was identified to be at high risk in the national assessment. The aim of the project was to develop a localised approach so that information could be developed to support adaptation to climate change in planning decisions at the community level. The approach included modelling a historical tropical cyclone and its associated storm surge for a range of sea level rise scenarios. The approach also included a shoreline translation model that forecast changes in coastal sediment transport. Inundation footprints were created and integrated with Geoscience Australia's national exposure information system, NEXIS, to develop impact assessments on building assets, roads and railways. Studies such as this can be a first step towards enabling the planning process to adapt to increased risk.

Coral reefs occur in shallow water with sea surface temperatures (SST) greater than 18ºC, extending beyond the tropics where warm currents enable their establishment [Hopley et al., 2007]. The southernmost reef in the Pacific Ocean occurs at Lord Howe Island (31° 30°S), fringing 6 km of the western margin of the island, with isolated reef patches on the north, west and eastern sides. The island is a Miocene volcanic remnant on the western flank of the Lord Howe Rise (foundered continental crust) formed of basaltic cliffs rising to 875 m, flanked by Quaternary eolianites [McDougall et al., 1981]. The reefs support 50-60 species of scleractinian corals, whose rates of growth are only slightly slower than in more tropical locations [Harriott and Banks, 2002]. However, carbonate sediments on the surrounding shelf are dominated by temperate biota, such as foraminifera and algal rhodoliths [Kennedy et al., 2002]. Prominent in mid shelf is a broad ridge-like feature that rises from water depths of 30-50 m, which we considered to be a relict coral reef that formerly encircled the island [Woodroffe et al., 2005, 2006]. This paper describes results of sonar swath mapping to determine the extent of the reef, and coring and dating that establishes its age and demise.

No abstract available

The coastal zone is arguably the most difficult geographical region to capture as data because of its dynamic nature. Yet, coastal geomorphology is fundamental data required in studies of the potential impacts of climate change. Anthropogenic and natural structural features are commonly mapped individually, with their inherent specific purposes and constraints, and subsequently overlain to provide map products. This coastal geomorphic mapping project centered on a major coastal metropolitan area between Lake Illawarra and Newcastle, NSW, has in contrast classified both anthropogenic and natural geomorphological features within the one dataset to improve inundation modelling. Desktop mapping was undertaken using the Australian National Coastal Geomorphic (Polygon) Classification being developed by Geoscience Australia and supported by the Department of Climate Change. Polygons were identified from 50cm and 1m aerial imagery. These data were utilized in parallel with previous maps including for example 1:25K Quaternary surface geology, acid sulphate soil risk maps as well as 1:100K bedrock geology polygon maps. Polygons were created to capture data from the inner shelf/subtidal zone to the 10 m contour and include fluvial environments because of the probability of marine inundation of freshwater zones. Field validation was done as each desktop mapping section was near completion. This map has innovatively incorporated anthropogenic structures as geomorphological features because we are concerned with the present and future geomorphic function rather than the past. Upon completion it will form part of the National Coastal Geomorphic Map of Australia, also being developed by Geoscience Australia and utilized in conjunction with Smartline.

The historical record reveals that at least five tsunamis generated by earthquakes and volcanic eruptions along the Sunda Arc have impacted the West Australian coast (1883, 1977, 1994, 2004 and 2006). We have documented the geomorphic effects of these tsunamis through collation of historical reports, collection of eyewitness accounts, analysis of pre- and post-tsunami satellite imagery and field investigations. These tsunamis had flow depths of less than 3 m, inundation distances of up to several hundred metres and a maximum recorded run-up height of 8 m. Geomorphic effects include off-shore and near-shore erosion and extensive vegetation damage. In some cases, vegetated foredunes were severely depleted or completely removed. Gullies and scour pockets up to 1.5 m deep were eroded into topographic highs during tsunami outflow. Eroded sediments were redeposited as sand sheets several centimetres thick. Isolated coral blocks and rocks with oysters attached (~50 cm A-axis) were deposited over coastal dunes however, boulder ridges were often unaffected by tsunami flow. The extent of inundation from the most recent tsunamis can be distinguished as strandlines of coral rubble and rafted vegetation. It is likely that these features are ephemeral and seasonal coastal processes will obscure all traces of these signatures within years to decades. Recently reported evidence for Holocene palaeotsunamis on the West Australian coast suggests significantly larger run-up and inundation than observed from the historical record. The evidence includes signatures such as chevron dunes that have not been observed from historical events. We have compared the geomorphic effects of historical tsunami with reported palaeotsunami evidence from Coral Bay, the Cape Range Peninsula and Port Samson. We conclude that much of the palaeotsunami evidence can be accounted for via more traditional geomorphic processes such as reef evolution, aeolian dune formation and archaeological site formation.

Geoscience Australia's Risk Research Group is using a variety of GIS coverages that span the Fremantle to Hillarys region of the Perth coastal system to assess the vulnerability of the Perth built environment to the potential impact of coastal erosion. Two fundamental questions are asked: whether there is accommodation space in the system that has the potential to act as a sink for eroded sediment, with or without a future sea level rise, and; whether the three-dimensional architecture of the shoreline facies precludes erosion given the current wave and storm climate. Morphological evidence suggest the Garden Island Ridge, up to and including Rottnest Island, has sheltered the coast from prevailing longshore currents. Little sedimentation has occurred in this sector, and consequently there is accommodation space for eroded sediment to be deposited below a level at which it has the capacity to be reworked onto the beach by fair-weather beach building processes. The shoreline geology of the Perth region is dominated by sand and limestone. Shear wave velocities measured through seismic cone penetrometer testing are used in conjunction with natural periods of vibration for the coastal sands to reconstruct the three-dimensional distribution of the erosion-resistant limestone. This reconstruction shows that the upper surface of the limestone is generally above sea level, suggesting the majority of the Perth coastal region is not at risk of significant erosion. At a number of localities, however, the contact between the limestone and the overlying sand is below sea level. These areas are prone to erosion resulting in significant risk to urban development.

Keppel Bay is a macrotidal environment that represents the interface of the large catchment of the Fitzroy River with the southern GBR continental shelf. In this study, we assessed the distribution of sediments and their depositional characteristics using a combination of sediment sampling, and acoustic (sonar) seabed mapping tools. Using statistical techniques, we classified the seabed sediments of Keppel Bay into five distinct classes, based on sediment grainsize, chemical composition, and modelled seabed hear stress (the influence of waves and tidal currents).

The Fitzroy catchment is the largest Queensland catchment discharging to the Great Barrier Reef (GBR) lagoon. Sediments and nutrients together with anthropogenic pollutants originating upstream in the catchment are discharged from the Fitzroy River via the Fitzroy Estuary (FE) and ultimately into Keppel Bay (KB). The estuary and the bay act as natural chemical reactors where the materials delivered undergo chemical and physical transformations before some are deposited and stored in the growing deltaic and beach areas, with the remainder transported eastward to the southern zone of the GBR lagoon.