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Explanations for the Upper Pleistocene extinction of megafauna from Sahul (Australia and New Guinea) remain unresolved. Extinction hypotheses have advanced climate or human-driven scenarios, in spite of over three quarters of Sahul lacking reliable biogeographic or chronologic data. Here we present new megafauna from north-eastern Australia that suffered extinction sometime after 40,100 (±1700) years ago. Megafauna fossils preserved alongside leaves, seeds, pollen and insects, indicate a sclerophyllous forest with heathy understorey that was home to aquatic and terrestrial carnivorous reptiles and megaherbivores, including the world’s largest kangaroo. Megafauna species diversity is greater compared to southern sites of similar age, which is contrary to expectations if extinctions followed proposed migration routes for people across Sahul. Our results do not support rapid or synchronous human-mediated continental-wide extinction, or the proposed timing of peak extinction events. Instead, megafauna extinctions coincide with regionally staggered spatio-temporal deterioration in hydroclimate coupled with sustained environmental change., The causes of the Upper Pleistocene megafauna extinction in Australia and New Guinea are debated, but fossil data are lacking for much of this region. Here, Hocknull and colleagues report a new, diverse megafauna assemblage from north-eastern Australia that persisted until ~40,000 years ago.

Hydraulic models used to simulate floods through riparian forests along rivers need to account for flow resistance caused by tree drag. Tree drag formulations have been developed for this p...

Kiacatoo Man, a large, rugged Aboriginal adult buried in the Lachlan riverine plains of southeastern Australia, was discovered in 2011. Laser‐ablation uranium series analysis on bone yielded a minimum age for the burial of 27.4 ± 0.4 ka (2σ). Single‐grain, optically stimulated luminescence ages on quartz sediment in which the grave had been dug gave a weighted mean age of 26.4 ± 1.5 ka (1σ). Luminescence samples from the grave infill and from sediment beneath the grave exhibit overdispersed dose distributions consistent with bioturbation or other disturbance, which has obscured the burial signal. The overlap between the minimum (U‐series) and maximum (luminescence) ages places the burial between 27.0 and 29.4 ka (2σ). Luminescence ages obtained from the channel belt of between 28 ± 2 and 25 ± 3 ka indicate that fluvial sedimentation was occurring before the Last Glacial Maximum, which is consistent with the broader geomorphic setting. Together, these results are internally and regionally consistent, and indicate that Kiacatoo Man was one of the more ancient individuals so far identified in Australia. His remains are important to our understanding of patterns of biological variation and other processes that have shaped people in the Murray‐Darling Basin through time.

The diffusive and nonspecific nature of nonpoint source contaminants such as sediment makes their management and mitigation challenging. Conventional source‐based tracing techniques for sediment simply apportion downstream sediment load to diffuse upstream sources classified by a limited number of source types including underlying rock type, land cover, and/or erosion process. Here, we develop a grid‐based sediment tracing technique that improves the precision of source contribution estimates and enhances the granularity of sediment source maps. We test the proposed technique using source and suspended sediment samples collected from the Emu Creek Catchment (911 km2), south‐east Queensland, Australia. Geochemical tracers were employed to distinguish sediments derived from the heterogenous and complex underlying rock types. Importantly, the proposed technique provided a greater spatial resolution of the sediment sources by assigning sediment contributions into grid sources rather than the area‐specific source types.

The novel application of the SediPump® sampling device to capture sufficient sediment mass from low concentration flood plume waters has enabled catchment source tracing of GBR flood plume sediment for the first time. Focused on the single largest exporter of sediment to the GBR, the Burdekin River, three wet season discharge events were sampled from 2017 to 2019 to characterise and trace flood plume suspended sediments using geochemistry, fallout radionuclides and clay mineralogy. Sampling targeted the end-of-river (EoR) flow hydrograph to capture contributing catchment sources, and flood plume samples from both the adjacent turbid primary waters and offshore secondary waters up to 160 km from the EoR. Analysis of EoR and plume sediment major element geochemistry indicates standard geochemical sediment tracing approaches cannot be applied to a large river catchment such as this, or across the catchment-marine continuum, where particle fractionation has occurred both within the catchment and across the salinity gradient from the river mouth. Further, the secondary plume sediments have also been affected by the addition of marine-sourced carbonate and biogenic silica. We show elemental ratios of the rare earth elements (REE) and thorium (Th) can be used as stable tracers across this continuum, and importantly, used to trace Burdekin plume terrigenous sediment transported >100 km’s from the river mouth back to its EoR REE/Th signal, which was unique for each of the three discharge events. These ratios were also used to trace this sediment to a major sub-catchment source. Additional fallout radionuclide 137Cs analysis of a sub-set of Burdekin EoR and plume samples also reveal sediment being transported in these GBR flood plumes are almost exclusively derived from sub-surface erosion processes.

Many tropical river systems have altered water quality due to human land use, impacting the biodiversity of freshwater and coastal ecosystems. Long-term, catchment-scale monitoring is needed to understand pollutant sources, controls, and trends. This 12-year study monitored baseflow and flood event nutrient and sediment concentrations, and estimated sediment loads across the Normanby Basin in northern Australia. Suspended sediment concentrations and yields were highest in upper catchment areas where cattle grazing occurred on erosion-prone sodic soils. Mid- and lower catchment rivers and floodplains were a sink for sediments and nutrients, trapping around 75% of suspended sediments during events. Clays (

In Australia the majority of tropical and subtropical regions lack any long-term (multi-decadal to centennial scale) instrumental climate records highlighting a need for alternatives such as proxy climate reconstructions. Despite this need, only a limited number of terrestrial proxy sources are available. Tree-rings provide one of the few options for climate reconstructions yet very little dendrochronological investigation has been undertaken as early assessments of tropical Australian species in the 1970s and 1980s indicated most species had short life-spans, poorly preserved timbers, or were compromised by having many ring anomalies. There has also been limited effort into understanding the growth-climate relationships of these trees with only a few studies undertaken targeting specific species that have unfortunately been heavily cleared from the region (eg. Toona ciliata). One exception noted in the early species assessment suggested that trees in the Araucariaceae family, a common tree family along the tropical Australian east coast, is longer lived than many other species in the region, contains growth rings which are annual in nature, and grows in response to climatic conditions.Here we describe the results from a stand of Araucaria cunninghamii trees located in Lamington National Park, a World Heritage listed rainforest in subtropical Southeast Queensland, Australia (a region known for experiencing extreme hydroclimatic events). Our assessment discovered the presence of false, faint, locally absent, and pinching rings. By combining traditional dendrochronological analysis (eg. crossdating) with more recent techniques such as age validation by bomb-pulse radiocarbon dating and tree-ring density analysis, a robust ring-width chronology from 1805-2014 was developed. Dendrometers installed on four trees at the Lamington site confirmed that tree growth was annual and that moisture sensitivity was driving growth. Further growth-climate analysis indicated that the strongest correlation to the tree-ring chronology was specifically related to drought conditions in the region. The strength of this response was compared to both local and regional spatial areas and to drought indices such as the self-calibrating Palmer Drought Severity Index (scPDSI), the Standardized Precipitation Evaporation Index (SPEI), and the long-term drought conditions shown by the Australian and New Zealand Drought Atlas (ANZDA). The combined analysis led to the development of a 200-year drought reconstruction for the region and demonstrates influences from both the El Niño Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO).

The identification of the sources of sediment is a key part of the management of waterways. This is typically achieved through the well‐established technique known as sediment source fingerprinting that uses tracers and statistical mixing models. Until recently, the approach for solving these mixing models has been dominated by frequentist methods. This review focuses on the growing interest in Bayesian methods for sediment fingerprinting and presents them as an alternative or complementary addition to the frequentist methods. Bayesian methods emphasize flexibility, for example, in the choice of probability distributions for tracers, inclusion of parameter probability terms, the choice of how to characterize tracer proportion, and the choice of fully or empirical Bayesian techniques. The Bayesian approach flexibly combines previous known and current information, to produce results that aim to accurately reflect the real‐world environment. Under the Bayesian paradigm, all model parameters are treated as random variables, and this allows all sources of variation to be explicitly communicated and modelled. Although there are considerable advantages to using a Bayesian approach for sediment tracing, there are some possible problems the practitioner should be aware of. These include computational issues and potential difficulties in choosing probability distributions to realistically represent model parameters. Though there are choices as to what Bayesian approach to implement (i.e., fully or empirical Bayesian), a fully Bayesian approach has been found to best retain fidelity to the Bayesian paradigm of treating all parameters as random variables. It has been recognized that the field of sediment source fingerprinting would greatly benefit from the development of a model that incorporates the tracer selection process into the modelling framework allowing for an all‐in‐one approach, and the flexibility of a Bayesian approach makes this development possible.

In Australia, there is a scarcity of high resolution hyrdoclimate reconstructions for the last several millennia. Fluvial-marine sediments offer a potential avenue for examining trends in freshwater input to coastal settings and, by inference, past hydroclimates. Here, major elemental geochemistry, δ13C and C:N ratios of organic matter, grain size and diatom species abundance, measured in a 4.4 m long sediment core collected from Moreton Bay, in east coast Australia, are used to infer the relative freshwater discharge of the adjacent catchment over the last ~1500 years. Reduced freshwater discharge into the Bay occurred from 630 to 1200 CE, especially between 1100 and 1200 CE. A broad increase in discharge is indicated after 1300 CE, extending to the present. The initial shift to the prolonged wet period coincides with both a decrease in the frequency of ‘dry’ El Nino events based on regional records from the austral Pacific, and a broad hemispheric-scale cooling trend. This record provides further insight into low amplitude climate variability in the Australian subtropics over the last 1000 years, supporting efforts in both forecasting current and future climates, and managing regional water resources. Importantly, instrumental records do not cover the full range of natural climate variability experienced in the region over the last 1000 years.

Concentrations of major and trace elements in freshwater fauna are often a reflection of local sediment chemistry. Biogeochemical profiles of freshwater species can be used to provide accurate and affordable assessments of species distribution, movement, and connectivity within river systems. Incorporating additional elements could significantly increase the precision and accuracy of population discrimination and movement analyses. To increase the variety of elements in biogeochemical tracing studies, we compared the concentrations of 38 major, trace, and rare earth elements (REEs) in bulk sediment (< 10 μm) and atyid shrimp from three rivers in South East Queensland, Australia. We determined which elements were correlated between sediment and shrimp samples and if these elements could distinguish different sample populations. This process identified elements that can directly associate shrimp with local sediment geochemical profiles. We found potassium (K), aluminum (Al), yttrium (Y), and the REEs cerium (Ce), lanthanum (La), and samarium (Sm) were spatially correlated between shrimp and sediment samples. Concentration ratios indicated K may be a relatively conservative tracer. Aluminum, REEs, and Y may undergo characteristic fractionation between sediment and shrimp tissue. Multivariate analysis indicated these elements could distinguish shrimp populations between sample sites. Results suggest that this small number of elements can link shrimp with specific rivers in accordance with local geochemistry, and thus may be valuable tracers with which to distinguish freshwater populations. As we measured bulk sediment concentrations, sampling these tracers is a relatively simplistic process that could be applied in a range of field conditions.

Almost all Australian tropical and subtropical regions lack annually-resolved long-term (multi-decadal to centennial scale) instrumental climate records. Reconstructing climate in these regions requires the use of sparse climate proxy records such as tree rings. Tree rings often archive annually-resolved centennial-scale climate information. However, many tropical and subtropical species have short life-spans, the timbers are poorly preserved, and there is a belief that the proxy records of these species are often compromised by ring anomalies. Additionally, for many species the relationship between climate (e.g. temperature and/or rainfall) and tree growth has not been established. These factors have led to tree-ring data being underutilized in the Australian subtropics. Trees in the Araucariaceae family, a common family in northern and eastern Australia, are both longer lived than many species in the Australian subtropics, present growth rings that are annual in nature, and their growth is known to vary with climate. In this study we examine two subtropical Araucariaceae species, Araucaria cunninghamii and Araucaria bidwillii, and quantify the relationship between their radial growth and climate variability. Ring anomalies including false, faint, locally absent, and pinching rings, are found to be present in these species, however, bomb-pulse radiocarbon dating of A. cunninghamii samples together with a whole tree approach helped to identify annual growth patterns despite such anomalous ring boundaries. Additionally, to determine which climate variables most influence growth in these species, dendrometers were installed at two locations in subtropical Southeast Queensland, Australia. We found that rainfall variability drives annual ring growth, while temperature constrains the onset and conclusion of the growth season each year. Our results demonstrate that through the use of A. cunninghamii and A. bidwillii trees which demonstrate annual growth in relation to climate variables there is potential to develop centennial scale climate reconstructions from the Australian subtropics. We provide recommendations on how to best identify ring anomalies in these species to help in the future development of long-term chronologies and climate reconstructions.

Eastern Australia is known to experience multi-decadal periods of flood and drought. Subtropical Southeast Queensland is one region where these devastating extreme events occur regularly yet a full understanding of their frequency and magnitude cannot be determined from the short duration ( 100 years) proxy rainfall information but locating suitable forest stands is difficult due to extensive land clearing by European settlers. Another factor deterring the use of trees as proxy data sources is that longer-lived species frequently contain anomalous rings, particularly faint rings, hindering their use for paleoclimate study. Here we present a method which overcomes the problems of identifying faint ring boundaries in trees by using X-radiographs and density patterns developed on the Itrax core scanner. We analysed 39 tree cores from 20 trees at a site in D'Aguilar National Park located just north of Brisbane city in Queensland, Australia. Each core had a 2 mm lath cut perpendicular to its rings which was then passed through an Itrax core scanner. The tree-ring boundaries were identified on the image by both the visual features in the radiograph and the change in density observed between rings. From this information we developed a tree-ring chronology. The chronology was checked using bomb-pulse radiocarbon dating on five trees to confirm the annual nature of the rings, and to correct dating errors in the chronology due to false rings which are common in this species. Climate response function analysis showed Austral annual rainfall (June–May) was the dominant environmental variable driving tree growth. Finally, a 69-year statistically significant reconstruction of Brisbane precipitation was produced showing that this non-destructive Itrax ring identification technique together with age validation by bomb-pulse radiocarbon dating is useful for dendroclimatological studies of trees with faint ring boundaries.

The Cooloola sand dunes are part of a series of aeolian parabolic dunes that stretch along the east coast of Australia. They form a chronosequence showing increasing weathering, soil formation and water erosion across six geomorphically recognized soil landscapes. These landscapes were recognized from air photographs and further refined on the basis of some 150 auger holes across the dunes. Data about the structure and floristics of the vegetation were collected at the same time. There is a significant body of literature about the Cooloola dunes but there are two areas that have not been satisfactorily considered. First the previous dating which gave inconsistent results has been superseded by single grain OSL dates and second Cooloola has not been considered in a regional context. Here we report the results of single grain optically stimulated luminescence (OSL) analyses for 31 samples for 21 sites across the geomorphic landscapes. The sites were selected near the apex of each dune as this represents the last depositional date and the least disturbed by sand movement. We recognized 10 units across the dunes on the basis of the dates available. The dune ages ranged from recent to 725 ka. The largest dunes at some 320 m high were dated at around 140 ka and these dunes carry the maximum vegetation biomass of this dunefield. Beyond this vegetation maximum the dunes had lost their parabolic shape due to prolonged weathering and erosion and the vegetation is greatly reduced in height and biomass. The depth to the soil B horizon gradually deepens with age to form giant podzols in the older dunes. The depth to the B horizon was remarkably consistent within the geomorphic landscapes across the length and breadth of the dunes. These studies place the Cooloola dunes in a unique position as the chronosequence is intact. The possible processes that lead to the formation of the dunes and the regional implications are discussed. Secondly, it shows the buildup and decline of the dune ecosystems and acts as a model for all ecosystems. Forest succession models which place less emphasis on soil development miss this important process.

This paper reports the results of jet tester experiments on soil samples of uniform properties which allow quantitative application of the new theory proposed in part 1 of these publications. This theory explores the possibly that a more adequate indicator of soil erodibility may be obtained by using the mass (and so volume) of soil eroded by the jet and the depth of scour penetration, rather than by using penetration depth alone, as assumed in the commonly-used data interpretation method. It is shown that scour geometry can be well described using a generalized form of the Gaussian function, defined by its standard deviation and maximum depth. Using a published expression for jet kinetic energy flux, the new theory divides this flux into that used to erode soil, and the remainder which is dissipated in a variety of ways. Jet experiments on a specially-prepared uniform soil sample are reported which provide the key to determining the spatial variability in the profile resistance to erosion offered by field soils. This resistance is expressed in the work required to erode unit mass of soil, denoted as J (in J/kg). The paper also gives results obtained on the profile variation in J for jet tests carried out at riverine sites on the upper Brisbane River, Queensland, Australia. As expected in most natural soil profiles, the results show an increase in J with depth in the profile. The soil resistance (J) is compared to the traditional interpretation of soil erodibility, (kd). The graphical comparison of these two indicators illustrates the inverse type of relationship between them which is expected from their respective definitions, but this relationship is associated with significant scatter. Possible reasons for this scatter are given, together with comments on jet tester experience in a wide variety of soil types. Copyright © 2017 John Wiley & Sons, Ltd.

A large proportion of the uncertainty surrounding catchment sediment budget modelling has been attributed to sediment supplied from riverbank erosion. Some of the variables influencing riverbank erosion are bend curvature, specific streampower, riparian vegetation, and in some instances sand and gravel extraction. The empirical relationship between these variables and observed riverbank erosion across 78 km of the Upper Brisbane River, Australia was investigated. No significant relationship was found between curvature, specific streampower and riverbank erosion. The role of riparian vegetation relative to sediment supply from riverbank erosion varied with spatial location, susceptibility of a reach to erosion, and human disturbance such as sand and gravel extraction. Despite not having data on substrate type the model described approximately 37% of the variation in observed riverbank erosion. It appears that inclusion of a management practice factor in riverbank erosion models is justified, where appropriate, and may improve model performance.

Gully and channel erosion are known to export large quantities of soil organic matter (SOM) to stream ecosystems. However, the implications for in-stream processing of SOM ultimately depend on its susceptibility to mineralization. We studied the influence of carbon (C) and nitrogen (N) lability on fine sediment organic matter mineralization following a high flow event in a small severely eroded headwater catchment in south-eastern Queensland, Australia. High-flow event stream water was incubated for 20 days under aerobic conditions in the dark, with four treatments: control, glucose enriched, glycine enriched, and glucose + glycine enriched. Destructive sampling was carried out at 0, 2, 6, 12, and 20 days to quantify different C, N, and phosphorus (P) fractions and specific UV absorbance (a proxy for aromaticity). Net C mineralization was very slow for all treatments with rates slowing markedly towards the end of the incubation. The addition of labile N did not significantly increase net C mineralization; however, net N mineralization significantly increased with the addition of labile C in the absence of labile N. We found increasingly larger net N mineralization relative to C towards the end of the incubation, even though initial substrate stoichiometry in the control indicated that N was the limiting element. Our results suggest that SOM mineralization is limited by C and not N bioavailability. One of the main implications of our study is that mineral N exported downstream in association with gully and channel eroded sediment has little influence on the in-stream processing of eroded organic C due to slow mineralization rates and fluxes in the water column. As a consequence, this mineral N would be available for generating primary productivity in downstream aquatic ecosystems.

Few Australian wetlands have persisted since the Last Glacial Maximum, with fewer still in existence through the entire last glacial cycle. The absence of wetlands, which itself indicates periods of moisture deficit, means there are few continuous climate and environmental change records covering this critical period. The lack of wetland persistence also raises the question of how plant and animal species that require permanent wetlands survived the last glacial cycle. Sixteen wetlands have been cored and dated on North Stradbroke Island (Minjerribah) – a large east Australian sand island – with basal dates reported from 10 sites for the first time. These wetlands range in age to over 200 000 years old, with six dating to the Last Glacial Maximum or earlier. There is no evidence of a stratigraphic discontinuity in the radiocarbon-based age–depth profiles, suggesting continuous deposition of highly organic sediment through the period covered by these ages (c. 40 ka). The persistence of these wetlands suggests that for much of the last 40 000 years, and for perhaps much longer, the regional moisture balance has been positive. Over the last glacial cycle, persistently wet conditions may have provided a refuge from regional drying, and thus contributed to the high genetic diversity of rainforest plants in the region. Vegetation and climate records from these sites will allow hypothesis testing about the drivers of both local and regional climate variability. Copyright © 2017 John Wiley & Sons, Ltd.

In Australia multi-decadal periods of floods and droughts have major economic consequences. Due to the short duration of Australian instrumental precipitation records it is difficult to determine the patterns of these multi-decadal periods. Proxy records can be used to create long-term rainfall reconstructions for regions which are lacking instrumental data. However, the spatial extent over which single site proxy records can be applied is poorly understood. Southeast Queensland (SEQ) is an area where tree-rings can be used to reconstruct long-term rainfall patterns but their regional representation is unknown. In this study the spatial variability in rainfall across SEQ is investigated from 1908-2007 using 140 instrumental rainfall stations. Pearson correlation analysis between stations is used to create groups at the r = 0.80, 0.85, and 0.90 correlation levels and then annual deviations from the mean are determined. These patterns indicate that rainfall is not uniform across SEQ but can be broken into two main spatially consistent groups. Each of these groups is broken down into several subgroups with higher correlation levels. Long-term streamflow records are found to be correlated to rainfall patterns local to the streamflow stations indicating that analysis of extreme events should consider spatial precipitation variability. Finally, the only currently available proxy rainfall reconstruction for the region, a 140-year Toona ciliata tree-ring width record from Lamington National Park, is compared to rainfall groups at different correlation levels across all of SEQ. The correlation between the reconstruction and the rainfall station groupings is best for the groups within which the tree-ring record is spatially located and this correlation improves as rainfall group correlation increases. Correlation is nearly non-existent for groupings located at a distance from the tree-ring site. These results demonstrate the importance of assessing the spatial variability of precipitation so that the spatial applicability of proxy records can be assessed.

Climatic forcing of fluvial systems has been a pre-occupation of geomorphological studies in Australia since the 1940s. In the Riverine Plain, southeastern Australia, the stable tectonic setting and absence of glaciation have combined to produce sediment loads that are amongst the lowest in the world. Surficial sediments and landforms exceed 140,000 yr in age, and geomorphological change recorded in the fluvial, fluvio-lacustrine and aeolian features have provided a well-studied record of Quaternary environmental change over the last glacial cycle. The region includes the Willandra Lakes, whose distinctive lunette lakes preserve a history of water-level variations and ecological change that is the cornerstone of Australian Quaternary chronostratigraphy. The lunette sediments also contain an ancient record of human occupation that includes the earliest human fossils yet found on the Australian continent. To date, the lake-level and palaeochannel records in the Lachlan-Willandra system have not been fully integrated, making it difficult to establish the regional significance of hydrological change. Here, we compare the Willandra Lakes environmental record with the morphology and location of fluvial systems in the lower Lachlan. An ancient channel belt of the Lachlan, Willandra Creek, acted as the main feeder channel to Willandra Lakes before channel avulsion caused the lakes to dry out in the late Pleistocene. Electromagnetic surveys, geomorphological and sedimentary evidence are used to reconstruct the evolution of the first new channel belt following the avulsion. Single grain optical dating of floodplain sediments indicates that sedimentation in the new Middle Billabong Palaeochannel had commenced before 18.4 +/- 1.1 ka. A second avulsion shifted its upper reaches to the location of the present Lachlan River by 16.2 +/- 0.9 ka. The timing of these events is consistent with palaeohydrological records reconstructed from Willandra Lakes and with the record of palaeochannels on the Lachlan River upstream. Willandra Lakes shows high inflows during the Last Glacial Maximum (similar to 22 ka), but their subsequent drying between 20.5 ka and 19 ka was caused by river avulsion rather than regional aridity. This case study highlights the benefits of combining fluvial with lacustrine archives to build complementary records of hydrological change in lowland riverine plains.

It has been argued that globally the extinction of many species of megafauna appears to coincide with the dispersal of modern humans, however, with the refinement of age ranges on megafauna specimens it has been revealed that many extinctions are in fact time-transgressive. This appears to be the case in Europe and Asia, and probably also the Americas. The argument over what mechanism was responsible for megafauna extinction in Australia, however, remains heavily contested. This contribution investigates the age of a single articulated megafauna specimen of Zygomaturus trilobus from the Willandra Lakes. The Willandra is unique in that it is the only Australian landscape with evidence for a) continual occupation by Aboriginal people from 50,000 years ago and b) the presence of megafauna. As people have occupied the Willandra since the period of initial colonisation, establishing the age range of this specimen provides a good test to determine if people drove megafauna into extinction soon after their arrival, or whether megafauna and people co-existed for a long period of time. Two independent dating techniques show that the fossil has a maximum age range based on OSL of 33.3–36.7kya and a minimum age range based on U-series at 32.4 ± 0.5kya. This specimen represents the youngest example of extinct megafauna reliably dated in Australia. Regardless of whether one accepts a short (47.5kya) or long (55kya) chronology for Aboriginal occupation of Australia, it would now appear that the second largest marsupial to ever exist was still present for a considerable time after the first arrival of Aboriginal people.

The spectral signature of individual quartz grains were measured using a high-sensitivity thermoluminescence imaging system based on a charge-coupled device (CCD) camera and custom optics. Luminescence emission behaviour was characterised for individual quartz grains (180–212 μm), with single grains shown to emit luminescence strongly across multiple signal bands. The spectral profiles of three quartz samples from contrasting geological contexts were then compared, with clear distinction in the spectral signatures of individual grains originating from single deposits within each provenance.

Dendroclimatology can be used to better understand past climate in regions such as Australia where instrumental and historical climate records are sparse and rarely extend beyond 100 years. Here we review 36 Australian dendroclimatic studies which cover the four major climate zones of Australia; temperate, arid, subtropical and tropical. We show that all of these zones contain tree and shrub species which have the potential to provide high quality records of past climate. Despite this potential only four dendroclimatic reconstructions have been published for Australia, one from each of the climate zones: A 3592 year temperature record for the SE-temperate zone, a 350 year rainfall record for the Western arid zone, a 140 year rainfall record for the northern tropics and a 146 year rainfall record for SE-subtropics. We report on the spatial distribution of tree-ring studies, the environmental variables identified as limiting tree growth in each study, and identify the key challenges in using tree-ring records for climate reconstruction in Australia. We show that many Australian species have yet to be tested for dendroclimatological potential, and that the application of newer techniques including isotopic analysis, carbon dating, wood density measurements, and anatomical analysis, combined with traditional ring-width measurements should enable more species in each of the climate zones to be used, and long-term climate records to be developed across the entire continent.

It is a substantial challenge to quantify the benefits which ecosystems provide to water supply at scales large enough to support policy making. This study tested the hypothesis that vegetation could reduce riverbank erosion, and therefore contribute to reducing turbidity and the cost of water supply, during a large magnitude flood along a 62 km riparian corridor where land cover differed substantially from natural conditions. Several lines of evidence were used to establish the benefits that vegetation provided to reducing eleven riverbank erosion processes over 1688 observations. The data and analyses confirmed that vegetation significantly reduced the magnitude of the riverbank erosion process which was the largest contributor to total erosion volume. For this process, a 1% increase in canopy cover of trees higher than five metres reduced erosion magnitude by between 2 and 3%. Results also indicate that riverbank erosion was likely to be affected by direct changes to the riparian corridor which influenced longitudinal coarse sediment connectivity. When comparing the impact of these direct changes on a relative basis, sand and gravel extraction was likely to be the dominant contributor to changed erosion rates. The locations where erosion rates had substantially increased were of limited spatial extent and in general substantial change in river form had not occurred. This suggests that the trajectory of river condition and increasing turbidity are potentially reversible if the drivers of river degradation are addressed through an ecosystem restoration policy.

A substantial body of literature exists on the influence of vegetation on flow resistance in rivers and floodplains. Research has shown that the quadratic drag force-velocity relationship used in boundary layer theory does not hold when flexible vegetation bends under the influence of drag. As such, a small number of drag force models that aim to account for reconfiguration of tree foliage have been developed. Drag force measurements for testing and parameterizing thesemodels are limited, especially for Australian riparian tree species. This paper presents work that is being undertaken to measure drag forces on Casuarina cunninghamiana (river she oak). The research aims to measure drag forces across a range of tree sizes and velocities to test published drag force models, and ultimately, to model flow resistance through monocultural stands of C. cunninghamiana. Initial experiments were undertaken on an estuary. A drag resistance frame was designed and constructed and attached to the side of a boat to measure drag forces. Since drag on rigid smooth cylinders is well established, initial experiments used rigid cylinders to test the experiment design. The results replicate expected drag coefficients for velocities greater than 1.0 m/s. At lower velocities, drag coefficients were high and substantial noise was encountered due to lateral vibration of the frame. This suggests that the drag resistance frame requires adaption to overcome vibrations that may have been amplified by resonance. Methods for estimating tree area and flexural rigidity are also presented. Near field LiDAR survey and photographic survey were used to estimate the frontal area of a sample tree. The relationship between pulling force and tree deflection for an in-situ tree was also recorded. The results suggest that, for the velocities tested in the drag experiments, drag forces on the sample tree would cause substantial bending of the tree stems. It is expected that the reconfigured tree frontal area will influence the drag force-velocity relationship, which will be investigated in future experiments measuring drag forces on trees.

Embayments and the biota they support are highly susceptible to disturbance within adjacent catchments. Examining the timing and magnitude of impacts arising from human-induced disturbance in these systems is often limited due to the absence of long-term monitoring. Moreton Bay in south-eastern Queensland is a shallow embayment that receives inflows from a 21220-km2 catchment. In this study, diatom abundances, pigment (chlorophyll-a, phaeopigments) and biogenic silica concentrations were evaluated in a composite sediment from central Moreton Bay to explore temporal trends in the photosynthetic community. The record extends from 1200 to 2011, incorporating the period of European settlement (c. 1840s) and rapid population growth and urbanisation of the catchment. The record shows that in central Moreton Bay bloom-forming marine diatoms (Thalassiosira, Thalassiothrix, Thalassionema) have increased in relative abundance since the mid-20th century, whereas the dominant benthic diatom (Paralia fenestrata) has declined. This transition most likely occurred in response to the compounding effects of increased delivery of nitrogen, fine sediments and pollutants to Moreton Bay as a consequence of changes in land use. The inferred historical decline in relative contributions of benthic microalgae to total primary production in central Moreton Bay has likely had wide-ranging ecological effects.

Drought-breaking floods pose a risk to coastal water quality as sediments, nutrients, and pollutants stored within catchments during periods of low flow are mobilized and delivered to coastal waters within a short period of time. Here we use subtidal surface sediment surveys and sediment cores to explore the effects of the 2011 Brisbane River flood on trace metals zinc (Zn), lead (Pb), copper (Cu), nickel (Ni), chromium (Cr), manganese (Mn), and phosphorus (P) deposition in Moreton Bay, a shallow subtropical bay in eastern Australia. Concentrations of Zn, Cu, and Pb in sediments in central Moreton Bay derived from the 2011 flood were the highest yet observed in the Bay. We suggest flushing of metal rich sediments which had accumulated on the Brisbane River floodplain and in its estuary during the preceding 10 to 40 years of low flows to be the primary source of this increase. This highlights the importance of intermittent high magnitude floods in tidally influenced rivers in controlling metal transport to coastal waters in subtropical regions.

Skeletal remains from a burial in New South Wales exhibit evidence of fatal trauma, of a kind normally indicative of sharp metal weapons, yet the burial dates to the mid thirteenth century—600 years before European settlers reached the area. Could sharp-edged wooden weapons from traditional Aboriginal culture inflict injuries similar to those resulting from later, metal blades? Analysis indicates that the wooden weapons known as ‘Lil-lils’ and the fighting boomerangs (‘Wonna’) both have blades that could fit within the dimensions of the major trauma and are capable of having caused the fatal wounds.

While sediment tracing has been typically applied to identify sediment sources that are difficult to measure by gauging (monitoring), it can also be useful in estimating relative sediment yields from gauged river catchments. The major and trace element composition of river sediments from eleven locations in the 130000 km2 Burdekin River catchment, northeastern Australia was analysed to examine relative contributions from upstream source areas in the 2011/12water year. Sediment tracing results are compared against estimates derived fromsediment load monitoring at three locations. Comparisons show that there is good agreement between tracing results and monitoring data at one of the tributary confluences. At the second site, notable contrastswere found between the load estimates from the monitoring and tracing data. At this site a large impoundment occurs between the upstream sampling/gauging sites for source sediments and the downstream sampling/gauging sites for target sediments. The contrast is likely caused by temporal variations in particle size distributions of suspended sediment fromeach river and differential trapping efficiencies in the impoundment for sediment derived fromthe different tributaries. In the absence of the detailed particle size data and trapping efficiency estimates, sediment tracing provides the unique opportunity to elucidate source contributions of the finer fractions of suspended sediment. At a third site, where there were recognised measurement gaps in the monitoring data during large discharge events, the relative load estimates fromthe tracing data provided a means of constraining the recognized uncertainty of monitored load estimates.We conclude that sediment tracing can be used as a valuable adjunct to monitoring data particularly in remote, large and data-sparse catchments. Both tracing results and monitoring data showthat the Upper Burdekin River and Bowen-Bogie Riverswere the dominant source of the b10 μm sediments being delivered to the GBR lagoon from the Burdekin River catchment in the 2011/12 water year. More substantial contribution from the Belyando-Suttor Rivers indicated by the tracing results than the monitoring data is attributed to preferential delivery of the 1–10 μm sediments through the impoundment and has uncovered a knowledge gap in sediment budgets in the catchment.

Human-driven alterations to freshwater ecosystems are leading to a global decline of river function and biodiversity. In our experience, managers want to be given many possible options to restore freshwater ecosystems that are workable within spatial, temporal, operational, and budgetary constraints of the system. Correspondingly, a new field for systematic river restoration planning has emerged through the use of well-established systems design concepts like multi-objective optimization and tradeoff analysis. In this article, we propose a decision framework for systematic river restoration planning where economic-environment systems design and tradeoff analyses are employed as a concurrent planning procedure before restoration interventions are implemented. Heuristic optimization and multi-criteria decision analysis methods are proposed to systematically design and objectively evaluate non-dominated economic-environment tradeoffs associated with restoration strategies within a watershed, and to provide a short-list of viable restoration alternatives to decision makers for negotiation and implementation. The proposed framework has the capacity to make science-based information and sophisticated decision support methods available for stakeholder deliberation. To illustrate the phases of the framework, we use a published case study of systematic restoration planning in South East Queensland, Australia.

Understanding processes that govern the transport and distribution of terrestrial sediments to and within bays is critical for interpreting the drivers of long-term changes in these ecosystems. On the east coast of Australia increased soil erosion and sediment delivery following extensive land clearing in the contributing catchments, associated with European settlement, is highlighted as a key driver of the decline of numerous nearshore habitats including seagrass meadows and in-shore coral reefs. Here we use optical, radiocarbon and radionuclide dating to estimate mass accumulation rates and type of terrestrial sedimentation in central Moreton Bay during the Holocene. We compare the long-term rates of infilling within the central basin with the recent past and show a 3–9 fold increase in sediment accretion over the last 100 years compared to the long term (last ∼ 1500 to 3000 yrs) average. Infilling during the Holocene is not spatially uniform, with preferential deposition occurring within the now submerged palaeochannels of the Brisbane and Pine rivers. We suggest that modern turbidity regimes in Moreton Bay are the result of the compounded effect of both a historical increase in fine sediment supply and a rapid decline in the effective storage capacity of the basin.

Freshwater ecosystems are declining under climate change and land-use change. To maximize the return on investment in freshwater conservation with limited financial resources, managers must prioritize management actions that are most cost-effective. However, little is known about what these priorities may be under the combined effects of climate and land-cover change. We present a novel decision-making framework for prioritizing conservation resources to different management actions for the conservation of freshwater biodiversity. The approach is novel in that it has the ability to model interactions, rank management options for dealing with conservation threats from climate and land-cover change, and integrate empirical data with expert knowledge. We illustrate the approach using a case study in South East Queensland (SEQ), Australia under climate change, land-cover change and their combined effects. Our results show that the explicit inclusion of multiple threats and costs results in quite different priorities than when costs and interactions are ignored. When costs are not considered, stream and riparian restoration, as a single management strategy, provides the greatest overall protection of macroinvertebrate and fish richness in rural and urban areas of SEQ in response to climate change and/or urban growth. Whereas, when costs are considered, farm/land management with stream and riparian restoration are the most cost-effective strategies for macroinvertebrate and fish conservation. Our findings support riparian restoration as the most effective adaptation strategy to climate change and urban development, but because it is expensive it may often not be the most cost-efficient strategy. Our approach allows for these decisions to be evaluated explicitly.

Sediment tracing using geochemical properties is an efficient way to identify the spatial sources of transported sediments delivered to waterways. Here, the contribution of soil sources to river bed sediments has been quantified in Emu Creek, a headwater catchment in south eastern Queensland, Australia. Soil samples were collected from the eight major rock types present in the catchment and were related to river bed sediments collected from eight sites along the main channel. Geochemistry, as characterized by 39 elemental concentrations, was measured using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Three particle size fractions were examined

Erosion of soil from catchments during floods can deliver large quantities of sediment to the coastal zone. The transformations and processes of nutrient release from catchment soils during flooding are not well understood. To test the hypothesis that catchment soils supply nutrients to the coastal zone, we examined nutrient release and transformation following wetting of soils formed from three distinct rock types (basalt, granite and sandstone) with fresh and marine water. The soil samples were collected from eroding areas of a subtropical river catchment. We simulated runoff, transport and deposition by tumbling the fine fraction of the soils in freshwater for three days and settling in seawater for four weeks. We also collected and incubated cores from an adjacent coastal bay and added a layer of catchment soil to simulate deposition of new sediment following flood plume settling. Dissolved nutrients were measured in both simulations. Basalt soils were relatively nutrient rich and released substantial quantities of organic and inorganic dissolved nutrients, particularly phosphate. However when soils were added to estuarine sediment cores and incubated, there was a net influx of phosphate from the overlying water. All soils continually released ammonium in both experiments, indicating that catchment soils may be an important source of ammonium to fuel productivity within the coastal zone. This study provides new insights into increased nitrogen availability in a nitrogen-depauperate coastal zone and identifies catchment geology as an important influence in coastal productivity through delivery of soil nitrogen to downstream estuaries.

The amounts and forms of soil phosphorus (P) follow predictable patterns during long-term pedogenesis, but have rarely been examined along subtropical chronosequences. We quantified changes in soil nutrient stocks, foliar nutrient concentrations, and the chemical forms of soil P along the Cooloola chronosequence, a series of coastal dunes spanning ca. 500,000 years of pedogenesis in subtropical Queensland. The total P stock in the upper 30 cm of the soil profile declined continuously with soil age, from 229–237 kg ha − 1 on the youngest soils (40 years old) to 24–28 kg ha − 1 on the oldest soils (195–> 460 ka). In contrast, total carbon (C) and nitrogen (N) stocks increased initially along the chronosequence and then declined in the oldest soils. As a consequence, soil N:P ratios increased continually throughout the sequence, from ≤ 4 on the youngest soils to 27–30 on the oldest soils. This indication of increasing biological P stress and ultimately P limitation was further supported by a decline in foliar P concentrations and increasing foliar N:P ratios of two common plant genera along the chronosequence. Sequential P fractionation revealed that although all forms of P declined during pedogenesis, young soils contained low concentrations of primary mineral P and relatively high concentrations of occluded P associated with secondary minerals, suggesting that the parent sand originated from strongly-weathered continental soils. We conclude that the Cooloola chronosequence is an important example of long-term ecosystem development under a subtropical climate, although the pre-weathered nature of the parent sand indicates that the sequence represents a modification of the Walker and Syers model of P transformations during pedogenesis.

Freshwater ecosystems are among the most diverse environments on Earth but also one of the most degraded and threatened due mainly to the intense human modification and exploitation. Despite the increase in funds devoted to rehabilitation of these systems little success has been reported so far. When planning for rehabilitation of catchments, stakeholders have to decide what combination of actions to implement and at which locations from a vast number of possible options. Often these activities are constrained by limited budgets. Here we apply the principles of systematic planning to rehabilitation, integrating erosion, sediment transport, ecological and economic objectives into the planning process to enhance the effectiveness of the rehabilitation plans and to support stakeholders in better understanding the effects of various objectives. We develop and apply a multi-objective approach to find a set of near-optimal trade-off solutions among a large number of candidate combinations of rehabilitation actions under sometimes competing objectives. We use a Pareto-optimal approach to store potentially useful combinations of rehabilitation actions (trade-offs) along the management objective gradients. Presenting those trade-offs as a function of the management objectives allow users to understand the commonalities and differences of various rehabilitation options when selecting different objectives. It is the learning from these relationships that classic optimisation approaches often lack. As proof of concept, we used an example rehabilitation project in South East Queensland (Australia) that aims to reduce sediment loads and improve the ecological health (measured as the EHMP index) of rivers while minimizing opportunity cost of rehabilitation plans. Opportunity cost is defined as the forgone economic value that would be compromised by the implementation of a rehabilitation plan. We found that our approach was efficient and effective in finding and systematically presenting promising trade-offs along different objective gradients (sediment reduction, ecosystem health and opportunity cost economics).

The response of river channels to land cover and land use changes in large areas of the tropics and subtropics is poorly documented. Arable agriculture and grazing was introduced to the subtropical catchment of the Brisbane River, Australia, by European settlers in the 1840s. This study examines subsequent changes to the morphology, sediments and vegetation of the Brisbane River in relation to the major drivers of channel change. Documentary evidence from pioneers, paintings, newspapers,maps, surveys, photographs, and instrumental flow records suggests that within 20 years of the introduction of sheep grazing, compaction and degradation of catchment soils and surface drainage produced a shift from perennial to seasonally ephemeral flow and channel incision in minor tributary valleys. The main channel remained stable until the 1850s in the Estuary, and until the 1890s in the middle reaches, where bank erosion increased average channel widths by 18%. Compared to rivers in temperate areas, the Brisbane River has been relatively resilient to changes in land use and land cover. Rates of lateral channel migration have been low since at least 1885, and the level of the channel bed has been stable since 1894. It is shown that the present-day compound channel is a pre-European form with dimensions adjusted to floods with decadal return periods. Increases in sediment supply associated with the incision of tributary streams and later, from widening of the main channel, is consistent with regional evidence for the predominance of channel erosion. This implies an ongoing channel adjustment to changes associated with European land use change.

Moreton Island and several other large siliceous sand dune islands and mainland barrier deposits in SE Queensland represent the distal, onshore component of an extensive Quaternary continental shelf sediment system. This sediment has been transported up to 1000 km along the coast and shelf of SE Australia over multiple glacioeustatic sea-level cycles. Stratigraphic relationships and a preliminary Optically Stimulated Luminance (OSL) chronology for Moreton Island indicate a middle Pleistocene age for the large majority of the deposit. Dune units exposed in the centre of the island and on the east coast have OSL ages that indicate deposition occurred between approximately 540 ka and 350 ka BP, and at around 96±10 ka BP. Much of the southern half of the island has a veneer of much younger sediment, with OSL ages of 0.90±0.11 ka, 1.28±0.16 ka, 5.75±0.53 ka and

Identifying of the sources, stores and pathways of sediments in a catchment is essential to accurately target management actions designed to reduce sediment delivery to receiving waters. Fingerprinting the source of sediment using geochemical properties has increasingly been accepted as an accurate approach for quantifying the contribution of different sources to river sediment discharge. In this study, we seek to examine the effect of particle size and location of the sources on their contribution to suspended sediments. Geochemical tracers (n = 41) were employed to calculate proportional contributions of sediment to Emu Creek, a predominantly pastoral catchment (911 km2) in south-eastern Queensland, Australia. The study focused on two high flow events (10- and 6-year return periods) and some lower flow events which occurred during the 18 months from October 2011 to March 2013. Source contributions were determined at eight spatially distributed sites in major tributaries and along the main channel of Emu Creek. Source determination at the in-stream sites was done using end member samples (based on the underlying rock type) collected upstream of the site of interest, thus indicating how different sources dominate at different locations downstream. To examine whether different size fractions shared similar provenances, three size fractions of both source and suspended samples including fine silt and clay (

We present the results of investigations into alluvial deposition in the catchment of the Normanby River, which flows into Princess Charlotte Bay (PCB) in the northern part of the Great Barrier Reef Lagoon. Our focus is on the fine fraction (< ~ 63 μm) of alluvial deposits that sit above the sand and gravel bars of the channel floor, but below the expansive flat surface generally referred to as the floodplain. Variously described as benches, bank attached bars or inset or inner floodplains, these more or less flat-lying surfaces within the macro-channel have hitherto received little attention in sediment budgeting models. We use high resolution LiDAR based mapping combined with optical dating of exposures cut into these in-channel deposits to compare their aggradation rates with those found in other depositional zones in the catchment, namely the floodplain and coastal plain. In total 59 single grain OSL dates were produced across 21 stratigraphic profiles at 14 sites distributed though the 24 226 km2 catchment. In-channel storage in these inset features is a significant component of the contemporary fine sediment budget (i.e. recent decades/last century), annually equivalent to more than 50% of the volume entering the channel network from hillslopes and subsoil sources. Therefore, at the very least, in-channel storage of fine material needs to be incorporated into sediment budgeting exercises. Furthermore, deposition within the channel has occurred in multiple locations coincident in time with accelerated sediment production following European settlement. Generally, this has occurred on a subset of the features we have examined here, namely linear bench features low in the channel. This suggests that accelerated aggradation on in-channel depositional surfaces has been in part a response to accelerated erosion within the catchment. The entire contribution of ~ 370 kilotonnes per annum of fine sediment estimated to have been produced by alluvial gully erosion over the last ~ 100 years can be accounted for by that stored as in-channel alluvium. These features therefore can play an important role in mitigating the impact on the receiving water of accelerated erosion.

Purpose The results of sediment source tracing in large river catchments depend on defined sources being adequately represented by the sampling and in subsequent numerical analysis. We hypothesise that surface soil concentrations of fallout radionuclides caesium-137 (137Cs) and lead-210 excess (210Pbex) are smaller at locations with higher soil erosion rate and that if this is not accounted for, then spatially random sampling gives a biased representation of surface soil delivered to rivers and biased source contribution estimates.

International audience; Purpose: Elevated sediment loads reduce reservoir capacity and significantly increase the cost of operating water treatment infrastructure making the management of sediment supply to reservoirs of increasing importance. Sediment fingerprinting techniques can be used to model the relative contributions of different sources of sediment accumulating in reservoirs. The goal of this research is to compare geological and statistical approaches to element selection for sediment fingerprinting modelling. Materials and methods: Time-integrated samplers (n=45) were used to obtain source samples from four major subcatchments flowing into the Baroon Pocket Dam in South East Queensland, Australia. The geochemistry of these potential sources were compared to sediment cores (n=12) sampled in the reservoir. Elements that provided expected, observed and statistical discrimination between sediment sources were selected for modelling with the geological approach. Two statistical approaches selected elements for modelling with the Kruskal-Wallis H-test and Discriminatory Function Analysis (DFA).In particular, two approaches to the DFA were adopted to investigate the importance of element selection on modelling results. A distribution model determined the relative contributions of difference sources to sediment sampled in the Baroon Pocket Dam. Results and discussion: Elemental discrimination was expected between one subcatchment (Obi Obi Creek) and the remaining subcatchments (Lexys, Falls and Bridge Creek). Six major elements were expected to provide discrimination. Of these six, only Fe2O3 and SiO2 provided expected, observed and statistical discrimination. Modelling results with this geological approach indicated 36% (+/- 9%) of sediment sampled in the reservoir cores were from mafic-derived sources and 64% (+/- 9%) were from felsic-derived sources. The geological and the first statistical approach differed by only 1% (σ 5%) for 5 out of 6 model groupings with only the Lexys Creek modelling results differing significantly (35%). The statistical model with expanded elemental selection differed from the geological model by an average of 30% for all 6 models. Conclusions: Elemental selection for sediment fingerprinting therefore has the potential to impact modeling results. Accordingly we believe it is important to incorporate both robust geological and statistical approaches when selecting elements for sediment fingerprinting. For the Baroon Pocket Dam, management should focus on reducing the supply of sediments derived from felsic sources in each of the subcatchments.

Coastal ecosystems can be degraded by poor water quality. Tracing the causes of poor water quality back to land-use change is necessary to target catchment management for coastal zone management. However, existing models for tracing the sources of pollution require extensive data-sets which are not available for many of the world’s coral reef regions that may have severe water quality issues. Here we develop a hierarchical Bayesian model that uses freely available satellite data to infer the connection between land-uses in catchments and water clarity in coastal oceans. We apply the model to estimate the influence of land-use change on water clarity in Fiji. We tested the model’s predictions against underwater surveys, finding that predictions of poor water quality are consistent with observations of high siltation and low coverage of sediment-sensitive coral genera. The model thus provides a means to link land-use change to declines in coastal water quality.

International audience; Tracing sediments back to their catchment sources using biogeochemical and physical fingerprints involves multiple assumptions. One of the most fundamental assumptions is that these fingerprints are consistent during sediment generation, transportation, and deposition processes. Accordingly, the biogeochemical fingerprints used to trace sediment must remain constant, during detachment and redistribution, or they must vary in a predictable and measurable way. One key challenge to this assumption is the sorting effect of particles by size during detachment, mobilization, transportation and deposition processes. Owing to the notable effect of particle size on sediment fingerprints, we believe it is important to review the main approaches used to address the effects of changes in particle size composition on sediment fingerprints. The two main approaches to addressing particle size impacts on fingerprint properties are: fractionation of source and sediment material to a narrow particle size range (e.g. isolation of

Sediment budget modeling has become a widely used management tool for setting priorities for natural resource management in Australia and globally. Two of the most widely used models in Australia, SedNet, and its more recent successor Source Catchments, rely on the Revised Universal Soil Loss Equation (RUSLE) to predict sediment production from hillslope erosion. In Australia, however, very little empirical data exists with which to test the hillslope sediment yields predicted by the RUSLE, particularly in the more remote savannah woodlands of northern Australia that are used by the cattle grazing industry. These savannah woodland landscapes comprise the vast majority of the catchment area draining into key ecological assets such as the Great Barrier Reef lagoon. In this paper we present the design and evaluation of a simple, low cost hillslope sediment trap (HST) that requires little to no maintenance across an entire wet season. It can consequently be deployed in remote, inaccessible areas to collect sediment generated through hillslope erosion processes as a means of testing predictions of erosion. Using these traps, it is possible to develop locally calibrated hillslope erosion models that will provide far more realistic predictions of erosion than have previously been employed. Laboratory flume evaluations of the HSTs also show that the traps will accurately sample the full particle size distribution of sediment mobilized on a given hillslope, with a suspended sediment (

Hillslope erosion rates have been estimated from models based on the widely used Revised Universal Soil Loss Equation (RUSLE) over large areas of Australia as a basis for catchment and river management. In this paper we present data from erosion plots in the Normanby catchment, Cape York, Australia. Extremely high rates of hillslope erosion are predicted in areas of the Normanby, producing extremely high modeled suspended sediment loads in streams which drain into the Great Barrier Reef (GBR) Lagoon. Using a novel, low budget sediment trap, total sediment yield is measured across the annual wet season (November to April) in 11 plots ranging in size from 0.1 to 1.9 ha. Total hillslope erosion rates (i.e., suspended and bed material load) measured within the four main geologies in the catchment, range between 0.03–256 kg/ha/yr. across two distinctly different wet seasons. These data are compared with the RUSLE modeled sediment yields determined for the same sites, for the same periods of time, using five different model formulations; two existing catchment scale models along with three plot scale formulations based on measured plot scale parameters. Modeled sediment yields using the first catchment scale model ranged from 4290 to 57,040 kg/ha/yr.; while the second catchment scale model predicted values of 730–9680 kg/ha/yr. Modeled yields using plot scale metrics together provided values ranging from 1550 to 331,700 kg/ha/yr. Depending on which modeled data are used, this represents an average ratio of over prediction by the RUSLE model (cf the measured rates for the same period) of between 12 and 13,300 times. We suggest that the over-prediction is due to four key reasons: 1) K factors have been incorrectly extrapolated from empirical data collected elsewhere on agricultural soils that vary greatly from the typical savannah rangeland soils; 2) the high stone content of the soils typically found on many of the savannah hillslopes is not adequately represented in either the C or K factor, 3) the model assumes that sediment supply is a linear function with time, when in fact the K factor (and hence supply) is likely to be non-linear though time—i.e. exhibiting supply exhaustion over an individual wet season or over the longer term (e.g. 103–104 years), and 4) the vegetative cover factors applied in previous modeling have used the late dry season C values, when the average cover factor across the wet season is significantly lower (where lower C factor = higher cover). We have derived new K factor values from our data for application in a new catchment model.

International audience; Understanding the sources of sediment, organic matter and nitrogen (N) transferred from terrestrial to aquatic environments is important for managing the deleterious off-site impacts of soil erosion. In particular, investigating the sources of organic matter associated with fine sediment may also provide insight into carbon (C) and N budgets. Accordingly, the main sources of fine sediment, organic matter (indicated by total organic carbon), and N are determined for three nested catchments (2.5 km2, 75 km2, and 3076 km2) in subtropical Australia. Source samples included subsoil and surface soil, along with C$_3$ and C$_4$ vegetation. All samples were analysed for stable isotopes (δ$^{13}$C, δ$^{15}$N) and elemental composition (TOC, TN). A stable isotope mixing model (SIAR) was used to determine relative source contributions for different spatial scales (nested catchments), climatic conditions and flow stages. Subsoil was the main source of fine sediment for all catchments (82%, SD = 1.15) and the main N source at smaller scales (55–76%, SD = 4.6–10.5), with an exception for the wet year and at the larger catchment, where surface soil was the dominant N source (55–61%, SD = 3.6–9.9), though contributions were dependent on flow (59–680 m3/s). C$_3$ litter was the main source of organic C export for the two larger catchments (53%, SD = 3.8) even though C4 grasses dominate the vegetation cover in these catchments. The sources of fine sediment, organic matter and N differ in subtropical catchments impacted by erosion, with the majority of C derived from C$_3$ leaf litter and the majority of N derived from either subsoil or surface soil. Understanding these differences will assist management in reducing sediment, organic matter and N transfers in similar subtropical catchments while providing a quantitative foundation for testing C and N budgets.