Along the Aceh-Andaman subduction zone, there was no historical precedent for an event the size of the 2004 Sumatra-Andaman tsunami; therefore, neither the countries affected by the tsunami nor their neighbours were adequately prepared for the disaster. By studying the geological signatures of past tsunamis, the record may be extended by thousands of years, leading to a better understanding of tsunami frequency and magnitude. Sedimentary evidence for the 2004 Sumatra-Andaman tsunami and three predecessor great Holocene tsunamis is preserved on a beach ridge plain on Phra Thong Island, Thailand. Optically stimulated luminescence ages were obtained from tsunami-laid sediment sheets and surrounding morphostratigraphic units. Single-grain results from the 2004 sediment sheet show sizable proportions of near-zero grains, suggesting that the majority of sediment was well-bleached prior to tsunami entrainment or that the sediment was bleached during transport. However, a minimum-age model needed to be applied in order to obtain a near-zero luminescence age for the 2004 tsunami deposit as residual ages were found in a small population of grains. This demonstrates the importance of considering partial bleaching in water-transported sediments. The OSL results from the predecessor tsunami deposits and underlying tidal flat sands show good agreement with paired radiocarbon ages and constrain the average recurrence of large late Holocene tsunami on the western Thai coast to between 500 to 1000 years. This is the first large-scale application of luminescence dating to gain recurrence estimates for large Indian Ocean tsunami. These results increase confidence in the use of OSL to date tsunami-laid sediments, providing an additional tool to tsunami geologists when material for radiocarbon dating is unavailable. Through an understanding of the frequency of past tsunami, OSL dating of tsunami deposits can improve our understanding of tsunami hazard and provide a means of assessing fu

TBA

Geoscience Australia conducted a survey of lakebed (benthic) nutrient fluxes in St Georges Basin, November 2003. The objectives were to: 1. determine the nature of nutrient cycling between the sediment and overlying water; and 2. determine the implications of benthic nutrient fluxes for water quality in the estuary. The relevance to management of this work is that it gives an indication of the susceptibility of the estuary to eutrophication from increased nutrient loads from the catchment. The key findings of the study were: - St Georges Basin was mesotrophic to eutrophic at the time of the survey (spring) based on relatively high respiration rates and O2 demand in the sediments measured by in situ benthic chambers. - Respiration rates were linked to phytoplankton biomass (mainly diatoms) where local fluvial discharge of dissolved nutrients created enhanced primary productivity in the water column, which in turn enhanced mineralisation rates. - St Georges Basin had comparatively low denitrification efficiencies (less than 60%). - St Georges Basin is likely to be prone to eutrophication and may have little tolerance for increases in nutrient and organic matter from the catchment due to the low denitrification efficiencies.

This study examined the geomorphology of the sea bed, the spatial distribution of the various sediment types and the geomorphic evolution of Cockburn Sound.

The Fitzoy Estuary is one of several macrotidal estuaries in tropical northern Australia that face ecological change due to agricultural activities in their catchments. The biochemical functioning of such macrotidal estuaries is not well understood in Australia, and there is a pressing need to identify sediment, nutrient and agrochemical pathways, sinks and accumulation rates in these extremely dynamic environments. This is particularly the case in coastal northern Queensland because the impact of water quality changes in rivers resulting from vegetation clearing, changes in land-use and modern agricultural practices are the single greatest threat to the Great Barrier Reef Marine Park. This report includes: 1 Aims and Research questions 2 Study Area 3 Climate and Hydrology 4 Geology 5 Vegetation and land use 6 Methods 7 Sampling strategy 8 Water column observations and samples 9 Bottom sediment properties 10 Core and bottle incubations 11 Data analysis 12 Results 13 Discussion 14 The roll of Keppel Bay in accumulating and redirecting sediment and nutrients from the catchment 15 Sediment biogeochemistry 16 Links between primary production, biogeochemistry and sediment dynamics: A preliminary zonation for Keppel Bay 17 Conclusions

A collaborative field trial of the Quester-Tangent View Series 5 single beam acoustic benthic mapping system was recently conducted in Wallis Lake by Geoscience Australia and Quester Tangent Corporation. The survey involved acquisition of the acoustic backscatter data from the northern channels and basins of Wallis Lake. Quester-Tangent software (IMPACT v3) was used to classify acoustic echograms that returned from the lake bottom into statistically different acoustic classes, using principal components analysis. Six acoustically different substrate types were identified in the Wallis Lake survey area. Ground-truthing was undertaken to identify the sedimentological and biological features of the lake floor that influenced the shape of the return echograms. For each sample, measurements were made of grain size, wet bulk density, total organic carbon, CaCO3 content, and mass of coarse fraction (mainly shell) material. Statistical cluster analysis and multi-dimensional scaling were utilised to identify any physical similarities between groups of ground-truthing sites. The analysis revealed four distinct and mappable substrate types in the study area. The degree of association between acoustic classes and measured sediment parameters was also quantified. Cluster and MDS analysis revealed that, based on the parameters measured, the six acoustic classes were not uniquely linked to the sediment groups, suggesting that factors other than the sediment parameters alone are influencing the acoustic signal. The spatial interpretation of the Wallis Lake Quester-Tangent data represents the first quantification of non-seagrass habitats in the deeper areas of the lake, and provides a useful indicatior of benthic habitat diversity and abundance. For future studies, a more quantitative measure of faunal burrow size and density, and also other sedimentary bedforms, is recommended.

Geoscience Australia conducted a survey to measure the benthic nutrient fluxes in Wallis Lake, during February 2003. The objectives were to: 1. measure the nutrient (and other metabolite) fluxes across the sediment-water interface at sites in Pipers Creek, Muddy Creek, Wallis Creek and in the Central Basin of Wallis Lake; 2. describe key processes controlling the nutrient fluxes across the sediment-water interface at each of the four sites; and 3. determine the trophic state and assess the estuarine condition of the four selected sites in Wallis Lake. The results of this recent summertime survey were compared to the observations made during the winter survey conducted in June, 2000. Pipers Creek and muddy Creek were similar in that they were both poorly flushed and close to nutrient discharges. These sites are at risk of experiencing eutrophic conditions. Wallis Creek had a high carbon loading, however the presence of seagrass and high denitrification efficiencies means this site remains in a 'good condition. Similarly, the Central Basin remains in a 'good' condition despite an increase in the carbon loading between winter and summer.

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No abstract available

An assessment of the potential impacts of climate change on coastal communities has been undertaken in collaboration with the Department of Climate Change and Energy Efficiency (DCCEE). This first-pass national assessment includes an evaluation of the exposure infrastructure (residential and commercial buildings, as well as roads and rail) to sea-level rise (SLR), storm surge and coastal recession. Some of the information contained in this report was included in the Department of Climate Change (now Department of Climate Change and Energy Efficiency) report "Climate Change Risks to Australia's Coast", published in 2009, and its supplement published in 2011.