SE Australia Research Articles

A simple equilibrium model for predicting shoreline change

This contribution describes the development, calibration and verification of a 1-D behaviour-orientated shoreline prediction model. The model primarily encapsulates shoreline displacement forced by wave-driven cross-shore sediment transport. Hysteresis effects are shown to be important and are included in the model, whereby present shoreline change is influenced by past hydro-/morpho-dynamic conditions. The potential magnitude of shoreline change increases with incident wave power and the degree of disequilibrium. The latter disequilibrium term (Ωeq−Ω) is expressed in terms of the time-evolving equilibrium (Ωeq) and instantaneous (Ω) dimensionless fall velocities and dictates the direction of shoreline movement. Following Wright et al. (1985) the equilibrium fall velocity is defined as a function of the weighted antecedent conditions and is a proxy for the evolving beach state. The decay rate of the weighting function used to compute Ωeq is a model free parameter determined by calibration against measured data, which physically reflects the degree of observed ‘memory’ of the system. The decay in amplitude of this weighting function with time is controlled by a ‘memory decay’ term (ϕ), where the weighting reaches 10%, 1% and 0.1% at ϕ, 2ϕ and 3ϕ days prior to the current calculation time. The model is applied to two multi-year (6+ years) data sets incorporating hourly wave and weekly shoreline measurements, from two contrasting energetic sites in SE Australia. The first is the relatively dissipative, straight Gold Coast (QLD) and the second is a more intermediate embayed beach at Narrabeen (NSW). The model shows significant skill at hindcasting shoreline change at both sites, predicting approximately 60% of the total shoreline variability. The Gold Coast shoreline is dominated by a strong seasonal signal. Conversely, at the Narrabeen embayment, shoreline variability (and morphology) is more dynamic, responding at storm frequency. Evidence suggests that there is a strong coherence between the shoreline position and morphodynamic state and that both have response times characterised by ϕ. It is hypothesised that optimised ϕ values in the shoreline model physically relate to the efficiency of sediment exchanges between the shoreface and offshore bars and the prevalence of one- or two-dimensional horizontal circulation. The general success of this new shoreline model for hindcasting the observed shoreline behaviour at two distinctly different open-coast sites suggests that this approach may be suitable for broader application.

Hydrological ensemble prediction systems

Hydrological ensemble prediction systems

Using 3H and 14C to constrain the degree of closed-system dissolution of calcite in groundwater

This study uses 3H concentrations, 14C activities (a14C), 87Sr/86Sr ratios, and δ13C values to constrain calcite dissolution in groundwater from the Ovens catchment SE Australia. Taken in isolation, the δ13C values of dissolved organic C (DIC) and 87Sr/86Sr ratios in the Ovens groundwater imply that there has been significant calcite dissolution. However, the covariance of 3H and 14C and the calculated initial 14C activities (a014C) imply that most groundwater cannot have dissolved more than 20% of 14C-free calcite under closed-system conditions. Rather, calcite dissolution must have been partially an open-system process allowing 13C and 14C to re-equilibrate with CO2 in the unsaturated zone. Recognising that open-system calcite dissolution has occurred is important for dating deeper groundwater that is removed from its recharge area in this and other basins. The study is one of the first to use 14C and 3H to constrain the degree of calcite dissolution and illustrates that it is a valuable tool for assessing geochemical processes in recharge areas.

Tracing hydrological variability and isotopic composition of waters from surface to cave at the Wellington Caves in SE Australia: Paleoclimate implications

Tracing hydrological variability and isotopic composition of waters from surface to cave at the Wellington Caves in SE Australia: Paleoclimate implications

호주 남동부 Otway 해안의 후기 신제3기 및 제4기 융기 운동(I): 제4기 해안단구 발달 및 지층서

본 연구는 호주 남동부 Victoria 남부 해안을 따라 발달하고 있는 Otway 산맥 일대에서 지난 5 Ma 동안의 신기지체구조 운동의 성격을 해안 산악 지역을 따라 분포하고 있는 해안단구의 발달상을 통해 밝히고 있다. OSL 연대 측정으로부터 얻은 저위 해안단구면의 융기율은 판 내부 구조운동의 영향이 현생 지형 발달에 미치는 결과를 명확히 보여주고 있다. 또한 본 연구는 제4기 해안단구와 플라이오세 고해수준 기록 간의 층서적 관계를 통해 후기 신제3기 이후에 나타나는 지구조 운동의 변화적 속성을 밝히고 있다. 이와 같은 후기 신제3기 이후 가속화된 지구조 운동 반응은 호주-태평양판의 이동성의 변화와 이에 따른 경계 응력의 증가가 대륙 내부 응력 수준에도 영향을 미친 결과로 이해된다. This study investigates a neotectonic context of the past 5 Ma for the Otway Ranges along the southern Victoria coast, SE Australia by evaluating the distribution and development of marine terraces along the mountainous coastal area. Uplift rate derived from low terrace deposits using OSL dating method is determined to evaluate the extent to which mild intraplate tectonism has the capability to influence the geomorphic evolution of continental interiors. This study also investigates the stratigraphic relationship between Quaternary marine terraces and Pliocene strandlines, which suggests a change of tectonic activity in the Late Neogene. The intensified tectonic response is well addressed in terms of an increase of the Australian intraplate stress level due to the change of relative motion and increased forces in the boundary between the Australian and Pacific plate.

호주 남동부 Otway 해안의 후기 신제3기 및 제4기 융기 운동(II): 암석권 휨 현상에 의한 대륙 지각의 융기

본 연구는 호주 남동부 지역 Otway 산맥 일대에서 확인되는 신기 지체구조 운동의 성격과 매커니즘을 규명하기 위해 현상적 융기 패턴과 중력이상 및 현생 응력 체계 등의 지구물리 자료간의 상관관계를 분석하였다. Otway 산맥의 융기축은 높은 중력값을 보이는 지역과 일치하는 반면 주변의 두꺼운 제3기 퇴적층 지역은 낮은 중력값을 보이는 지역과 일치하고 있어 높은 중력값의 이상 구간은 제3기 퇴적층 지역에 의해 구분되는 형태를 보여주고 있다. 한편 단층, 습곡 활동으로 특징되는 연구 지역 일대의 지질 구조 및 분포 패턴은 호주 남동부 지역의 현생 응력 체계와 잘 일치한다. 지형 고도와 중력 간의 양의 상관관계는 가설적으로 연구 지역 일대의 융기 운동이 대규모(<TEX>$10^2$</TEX> km 대)의 암석권 휨 현상에 의해 발생하고 있음을 보여주고 있으며, 판 경계 응력에 의한 암석권 내 기존 약대들의 재활성화는 이러한 대규모 변형 양식에 있어 중요한 역할을 담당하고 있는 것으로 판단된다. The relationship between tectonic uplift and geophysical analysis of gravity anomalies and the in-situ stress fields in the Otway Ranges, SE Australia is addressed in this study to understand the nature and possible mechanism for the neotectonic movements. The uplift axis of the ranges is coincident with the regional Bouguer gravity highs whereas thick Tertiary sedimentary successions are highly correlated with the gravity lows along the basin rift geometry. This result suggests that the gravity highs are separated by the thick Tertiary sedimentary successions. Regional structural trends associated with faults and foldings of the deformed surfaces are consistent with the prevailing NW-SE <TEX>$S_{Hmax}$</TEX> trend in this part of the continent. The anomalously positive correlation between topography and Bouguer gravity fields suggests possibly a lithospheric flexural deformation mode at a long wavelength (order of <TEX>$10^2$</TEX> kms) in the region. It also suggests that the reactivation of pre-existing lithospheric structures driven by plate boundary forces plays a key role in this mode.

HadISD: a quality-controlled global synoptic report database for selected variables at long-term stations from 1973–2011

Abstract. This paper describes the creation of HadISD: an automatically quality-controlled synoptic resolution dataset of temperature, dewpoint temperature, sea-level pressure, wind speed, wind direction and cloud cover from global weather stations for 1973–2011. The full dataset consists of over 6000 stations, with 3427 long-term stations deemed to have sufficient sampling and quality for climate applications requiring sub-daily resolution. As with other surface datasets, coverage is heavily skewed towards Northern Hemisphere mid-latitudes. The dataset is constructed from a large pre-existing ASCII flatfile data bank that represents over a decade of substantial effort at data retrieval, reformatting and provision. These raw data have had varying levels of quality control applied to them by individual data providers. The work proceeded in several steps: merging stations with multiple reporting identifiers; reformatting to netCDF; quality control; and then filtering to form a final dataset. Particular attention has been paid to maintaining true extreme values where possible within an automated, objective process. Detailed validation has been performed on a subset of global stations and also on UK data using known extreme events to help finalise the QC tests. Further validation was performed on a selection of extreme events world-wide (Hurricane Katrina in 2005, the cold snap in Alaska in 1989 and heat waves in SE Australia in 2009). Some very initial analyses are performed to illustrate some of the types of problems to which the final data could be applied. Although the filtering has removed the poorest station records, no attempt has been made to homogenise the data thus far, due to the complexity of retaining the true distribution of high-resolution data when applying adjustments. Hence non-climatic, time-varying errors may still exist in many of the individual station records and care is needed in inferring long-term trends from these data. This dataset will allow the study of high frequency variations of temperature, pressure and humidity on a global basis over the last four decades. Both individual extremes and the overall population of extreme events could be investigated in detail to allow for comparison with past and projected climate. A version-control system has been constructed for this dataset to allow for the clear documentation of any updates and corrections in the future.

Poverty, Work and Social Networks: The Role of Social Capital for Aboriginal People in Urban Australian Locales

In this article, I present the key findings from a project entitled “The Social Context of Indigenous Poverty”. The research involved a series of interviews with Aboriginal people in urban SE Australia on issues of poverty, social capital and social exclusion. In the article I draw together Aboriginal perspectives on the meaning of poverty to reflect on the relevance of social capital concepts for understanding Aboriginal economic disadvantage and hence, the merits of policy framed in these terms.

Effects of the March 2011 Japanese Tsunami in Bays and Estuaries of SE Australia

On 11 March 2011 a subsea earthquake off the north-eastern coast of Honshu Island, Japan generated a huge tsunami which was felt throughout the Pacific. At the opposite end of the Pacific Ocean, on the south-east coast of Australia, multiple reflections, scatterings and alternate pathways lead to a prolonged and complicated response. This response was largely unaltered in crossing the continental shelf but was then transformed by bay resonances and admittances. These effects are described using data from tide recorders sparsely spread over 1,000 km of the coast. Some new adaptations and applications of time-series analysis are applied to separate tsunami waves that have followed different pathways but contain the same spectral components. The possible types of harbour response are classified and illustrated. Despite its small height in this region, the tsunami put several swimmers at serious risk and generated strong harbour oscillations, which should be considered when generating future warnings.

Connectivity, genetic structure and stress response of Phragmites australis: Issues for restoration in a salinising wetland system

Plant condition, analysed using fluoroscopy and morphological characteristics and, genetic structure using microsatellite markers and chloroplast DNA sequences was studied in Phragmites australis in the Gippsland coastal wetlands, SE Australia. Gene flow appeared regular and widespread between populations of P. australis in the Gippsland Lakes with some local genetic structure and no clear association with salinity. There was no genetic evidence of either salt tolerant or introduced variants.

Environmental controls on the nitrogen-fixing cyanobacterium Nodularia spumigena in a temperate lagoon system in SE Australia

Environmental controls on the nitrogen-fixing cyanobacterium Nodularia spumigena in a temperate lagoon system in SE Australia

Depths of Modern Coastal Sand Clinoforms

Abstract Clinoforms are classical geological features. Examples in the rock record or in seismic reflection data that originally formed in shallow water can potentially help to locate paleo–sea level, but their precise links with sea level need to be established using modern examples before such inferences can be made accurately. Some near-shore areas of high wave energy and steep coasts host sand bodies with upwards-convex surfaces. These clinoforms have been suggested to have been created from sand exported from the upper shoreface during stormy conditions, and deposited at depths where wave action diminishes below the threshold of motion (Field and Roy 1984; Hernandez-Molina et al. 2000). We have compiled the shapes of these bodies in a variety of wave environments in order to test this idea. The interpreted depths at which the sand surface steepens (i.e., the clinoform rollover) vary from 21 m off southern California to deeper than 50 m off SE Australia. To assess the link with wave action, rollover depths were compared with adjacent deep-water wave properties over the period 1992–2001 in the ERA-40 reanalysis dataset. Rollover bed shear stresses were computed from properties representing average wave conditions and from properties associated with upper–percentile conditions. Stresses were found to reach 0.1–0.5 Pa during upper 5-percentile wave conditions, exceeding the sediment threshold of motion estimated from reported grain-size data. Sediment to below the rollover is therefore mobile during extreme wave conditions.

Detrital zircon evidence for the linkage of the South China block with Gondwanaland in early Palaeozoic time

AbstractLA-ICP-MS U–Pb dating of Lower Devonian detrital zircon samples from three representative sections in the South China block yields dominant Grenvillian and Pan-African populations, similar to the age distribution of early Palaeozoic samples from Gondwana, the Tethyan Himalaya and West Australia, in particular. Hf isotopic compositions indicate the contributions of juvenile crust at 1.6 Ga and 2.5 Ga, and bear a resemblance to their counterparts from SE Australia and West Antarctica, revealing the mixed origin of the Pan-African and Grenvillian grains from juvenile magmas and melting of pre-existing crustal rocks. These results suggest that the South China block should be considered an integral part of East Gondwana in early Palaeozoic time, rather than a discrete continental block in the Palaeo-Pacific or a fragment of Laurentia.

Assessing size, abundance and habitat preferences of the Ocean Perch Helicolenus percoides using a AUV-borne stereo camera system

Traditional fishery resource assessment methods using trawl gear are unable to sample rocky substratum and are prone to underestimating the biomass of species having partial or strong association with rocky reefs. This study successfully used an Autonomous Underwater Vehicle (AUV) and image-yielding methods to estimate size, abundance and habitat preference of an abundant and commercially important ‘rockfish’ – the Ocean Perch (Helicolenus percoides) – in rocky habitats on the continental shelf off Tasmania, SE Australia. More than half (53%) of the Ocean Perch observed were photogrammetrically measured with known accuracy using a stereo camera system yielding length-frequency distributions. Observations of juvenile and adult H. percoides across a depth gradient showed that adults preferred rocky substrates over soft substrates, whereas juveniles preferred soft substrate over hard substrate. We found a positive relationship between rockfish abundance and increasing depth in most habitat types. These results demonstrate the utility of image-based methods for determining size composition and habitat preferences of some reef-associated species. However, there is scope to improve image-based methods using length estimation procedures that enable higher proportions of individuals to be measured (compared to the proportion achieved in this study), and by incorporating automated image annotation to decrease image analysis times, particularly when examining species/habitat relationships. The importance of analytical procedures that account for autocorrelation in non-independent image data on habitats and associated species is discussed. We conclude that rapidly maturing image-based observational methods have potential utility in complementing fishery stock assessments of some reef-associated species. Image-based methods are also well-suited to simultaneously provide additional quantitative measures of benthic habitats, invertebrate fauna and fishery environments.

Available soil phosphorus, phosphorus buffering and soil cover determine most variation in phosphorus concentration in runoff from pastoral sites

Phosphorus (P) runoff from agricultural land contributes to elevated P concentrations in surface water. Although P concentrations in runoff are often higher when soil P is increased, attempts to quantify this relationship in field studies have been inconclusive, either because of confounding within experiments or methodological differences between experiments. The present study attempted to address these issues using simulated rainfall at 15 pastoral locations with varied lithology, land-use intensity, plant cover and soil-P properties in SE Australia, at a total of 38 on-farm sites, each with paired plots. At 27 sites, one of each pair was covered with 70 % shade-cloth to reduce rainfall energy. Although these were uncultivated pastoral sites and surface soil erosion rates were all relatively low, eroded surface soil had sufficiently high concentrations of P to make a major contribution to total P in runoff from some sites, even when plant-available soil P was low. We conclude that greater vegetative cover is required to manage P in runoff than to manage soil erosion. When soil was adequately protected against erosion by either high vegetative cover or shade-cloth, greater than 90 % of the variation in both dissolved reactive P and total P was explained by two commonly measured soil variables: soil-test P (bicarbonate extract) and P-buffering index (where P was in the range where plants may respond to fertiliser). It appears that available soil P can be raised with fertiliser to improve agronomic production without fear of significantly increasing P losses in runoff provided soil test P remains below the agronomic critical concentration defined by the soil P-buffering index. These findings have broad relevance for environmental risk assessment and management where the data required for more complex procedures are unavailable.

Phytoplankton assemblages of two intermittently open and closed coastal lakes in SE Australia

Species composition and biomass of phytoplankton assemblages of a heavily impacted lake (Lake Illawarra) and a less impacted lake (Burrill Lake) in the South-Eastern region of Australia were compared based on bimonthly samples from three sites in each lake collected between April 2005 and April 2007. Lake Illawarra was generally characterized by higher nutrient concentrations and lower salinity than Burrill Lake. Phytoplankton assemblages displayed significant differences between the two lakes in terms of the dominant species composition and patterns of seasonal change rather than biomass. Diatoms were the dominant species in Lake Illawarra on most sampling occasions. In contrast, dinoflagellates (including toxic species) dominated in Burrill Lake during most seasons. Seasonal succession of phytoplankton in the two lakes did not follow the strict spring maximum that is generally observed in temperate waters. In Burrill Lake, maximum phytoplankton biomass often occurred in winter, while the maximum biomasses in Lake Illawarra occurred in autumn, winter and spring. The significant difference of nutrient structure between two lakes and warm temperate regime was regarded as important factors to affect these results. The results suggested care should be taken when relying on estuary health “indicators”, such as chlorophyll a, rather than more detailed investigations of phytoplankton species compositions.

Robust chronological reconstruction for young speleothems using radiocarbon

We have studied two young speleothems, SC4 from Smiths Cave (Christmas Island, eastern Indian Ocean) and WM7 from Wollondilly Cave (Wombeyan caves, SE Australia). Attempts to date these speleothems by the Th/U method have proved unsuccessful with some age reversals for SC4 due to multiple sources of non-authigenic Th. This method has also resulted in imprecise ages for WM7 because of low U concentrations (<10 ppb) and consequently very low levels of authigenic 230Th relative even to the very low levels of detrital 230Th present. Here, we present an alternative method for reliable dating of these young speleothems using radiocarbon. Approximately 100 carbonate samples from SC4 and WM7 were analysed for 14C by accelerator mass spectrometry (AMS). The AMS results indicate that bomb 14C was evident in the youngest parts of both stalagmites. Two different approaches were used to estimate dead carbon fraction (DCF) values for these stalagmites for the pre-bomb period. For SC4, the DCF values were estimated based on the timing of 14C dates for that period determined by high-resolution δ18O recorded in the speleothem, and the timing of the onset of bomb 14C. For WM7, a “maximum” range of pre-bomb DCF was determined. Chronologies of these speleothems were built based on a dense sequence of DCF-corrected ages using three different age-depth models: Clam (Classical method), and Bacon and OxCal (Bayesian statistical approach). Good agreement between these age-depth models were observed indicating that the top 170 mm of SC4 and the top 50 mm of WM7 grew during the past 550–750 years and 1360–1740 years, respectively.

Stand dynamics and spatial patterns across varying sites in the invasive Lantana camara L. (Verbenaceae)

As with many invasive plant species, little is known of the population spatial patterns and stand dynamics of Lantana camara L. (Verbenaceae)—a thicket-forming weed of worldwide significance in managed and conservation lands, including coastal and inland habitats of Eastern Australia. Consequently, we mapped and followed annually for 3 years the demographic fate of more than 2000 Lantana individuals at sites with four land-uses (hoop pine plantation, cattle farm, and two eucalyptus forests with occasional grazing and periodic burning regime, respectively) in Queensland, SE Australia. Populations exhibited plant size distributions that were continuous (i.e., of L or symmetric type) and unimodal, except the farm population where bimodality was observed. Newly established plants could be reproductive within one growing season at ~50 cm in height, especially where environmental resources were not limiting. Density had an appreciable effect on the weed’s reproductive capacity and growth, but not on survival. Established and newly recruited individuals were aggregated but the degree of aggregation decreased with plant size. However, in the sites that had experienced burning or mechanical clearing, Lantana seedling/juvenile recruitment assumed negative association (spatial displacement) in relation to established individuals. The findings of this study agree with the notion that ecological processes often leave characteristic spatial signatures, which if interpreted using appropriate hypotheses can help to ascertain factors responsible for the observed spatial patterns and stand dynamics.

Impacts of recreational boating activities on the seagrass Posidonia in SE Australia

In SE Australia, the seagrass Posidonia australis is mostly restricted to isolated populations in estuaries and bays, and meadows in Sydney metropolitan estuaries have recently been listed by the NSW Government as threatened with extinction. While large developments impacting on seagrasses are now mostly controlled by environmental legislation, small-scale impacts remain and can lead to fragmentation across large areas. Here, damage to Posidonia meadows caused by boat moorings, propeller scouring and related recreational boating activities has been investigated using easily accessed aerial photography. While individual impacts were often small, in some locations large areas were affected and significant fragmentation of the seagrass landscape was observed and suggests urgent management action is required. The widespread availability of remote sensed data through tools such as Google Earth (©) should lead to greater community awareness of local changes in seagrassses meadows and could be used to improve the management of these smaller scale impacts.

Early-mid Cretaceous tectonic evolution of eastern Gondwana: From silicic LIP magmatism to continental rupture

The Early–mid Cretaceous marks the confluence of three major continental-scale events in eastern Gondwana: (1) the emplacement of a Silicic Large Igneous Province (LIP) near the continental margin; (2) the volcaniclastic fill, transgression and regression of a major epicontinental seaway developed over at least a quarter of the Australian continent; and (3) epeirogenic uplift, exhumation and continental rupturing culminating in the opening of the Tasman Basin c. 84 Ma. The Whitsunday Silicic LIP event had widespread impact, producing both substantial extrusive volumes of dominantly silicic pyroclastic material and coeval first-cycle volcanogenic sediment that accumulated within many eastern Australian sedimentary basins, and principally in the Great Australian Basin system (>2 Mkm3 combined volume). The final pulse of volcanism and volcanogenic sedimentation at c. 105–95 Ma coincided with epicontinental seaway regression, which shows a lack of correspondence with the global sea-level curve, and alternatively records a wider, continental-scale effect of volcanism and rift tectonism. Widespread igneous underplating related to this LIP event is evident from high paleogeothermal gradients and regional hydrothermal fluid flow detectable in the shallow crust and over a broad region. Enhanced CO2 fluxing through sedimentary basins also records indirectly, large-scale, LIP-related mafic underplating. A discrete episode of rapid crustal cooling and exhumation began c. 100–90 Ma along the length of the eastern Australian margin, related to an enhanced phase of continental rifting that was largely amagmatic, and probably a switch from wide–more narrow rift modes. Along-margin variations in detachment fault architecture produced narrow (SE Australia) and wide continental margins with marginal, submerged continental plateaux (NE Australia). Long-lived NE-trending cross-orogen lineaments controlled the switch from narrow to wide continental margin geometries.