Dr Rafael Carvalho

A preliminary sediment budget for the sandy shores flanking the entrance to Western Port, a large bay in Australia, was formulated using a comparison between two Digital Surface Models (DSMs) with a 30-year interval and auxiliary shoreline data. The 1977 DSM was generated from ten aerial photographs using Structure-from-Motion (SfM) photogrammetry. Assessment of its accuracy obtained an RMSE of 0.48 m with most of the independent points overpredicting or underpredicting elevations by less than 0.5 m following manual point cloud cleaning. This technique created a 7.5 km2 surface with a Ground Sampling Distance of 34.3 cm between two coastal towns separated by a narrow channel. Comparison of the 1977 DSM to a second, light detection and ranging (LiDAR)-derived DSM from 2007 showed that a volume of ~200,000 m3 of sediment (above Mean Sea Level) was deposited at Newhaven Beach on Phillip Island, while, during the same period, ~40,000 m3 of sediment was lost from the mainland beaches of San Remo, on the eastern side of the channel. Shoreline positions extracted from aerial photographs taken in 1960 and a nautical chart published one century earlier indicate that the progradation experienced at Newhaven Beach has been possible due to provision of sediment via destabilisation of the vegetation covering the updrift Woolamai isthmus on the southeast coast of Phillip Island, whereas the retreat observed at San Remo Beach since 1960 can be attributed to the natural dynamics of the entrance, which appears to favour flood-dominance on the western side and ebb-dominance on the eastern side. While a more comprehensive balance of volumes entering and exiting the area would specifically benefit from volumetric assessments of the subaqueous part of the entrance, the general usefulness of quantifying coastal change using SfM and historical photographs is demonstrated.

Previous research utilising water level observations and hypsometric data has suggested that intertidal areas exert some control on main channel flow dynamics in estuaries, lagoons and tidal creeks. This has been demonstrated in more detail for saltmarsh and mangrove creeks utilising measurements of tidal velocity. However, understanding of relationships between tidal hydrodynamics and intertidal wetlands is still lacking for mature barrier estuaries. Improved understanding of hydrodynamics in these systems, as well as potential interactions with tidal wetlands, may facilitate their effective management and modelling. This study investigates relationships between main channel hydrodynamics and vegetated intertidal wetlands at Minnamurra River estuary, southeast Australia, using observations of tidal dynamics and wetland inundation regime. Tidal data was collected over five spring-neap cycles utilising tidal gauges and drag-tilt flow meters at six locations in the estuary's main channel, and 14 pressure transducers along three wetland transects. Comparison of stage-velocity plots and hypsometric curves indicates that estuarine flow dynamics were spatially variable and strongly influenced by the geomorphology of intertidal wetlands in the upper estuary, where water surface gradients developing during flood and ebb phases created velocity pulses. Spatiotemporal analysis of tidal asymmetry showed variability along the estuary, as well as between spring and neap conditions. The estuary studied displayed an ebb-dominated deeper main channel (velocity asymmetry) surrounded by wide shallow flood-dominated margins, indicating that caution should be adopted when interpreting an estuary's tidal asymmetry using a single asymmetry characteristic. Overall, results presented here demonstrate a strong connection between estuarine hydrodynamics and vegetated intertidal wetlands, which implies that integrated approaches considering estuarine hydrodynamics and vegetated intertidal wetlands simultaneously are required to manage and model mature barrier estuaries.

A sediment compartment approach is an appropriate framework within which to undertake planning and management of coastal environments, and a hierarchical scheme has been adopted by several state governments in Australia. This study applies a geospatial comparison of terrain modelling to estimate decadal-scale sediment transfer in a closed wave-dominated coastal compartment in southeastern Australia. The Shoalhaven River, one of the larger rivers in southern New South Wales, drains from a temperate catchment of 7151 km2 into Shoalhaven Bight, a secondary compartment. The river has infilled the barrier estuary at its mouth in recent millennia, and delivers sediment that nourishes a well-developed strandplain to its north. We estimate sediment yield from the heterogeneous catchment based on deposition between 2003 and 2014 bathymetric surveys in a reservoir formed as a result of dam construction. Delivery of ~86,000 m3/y to the estuarine channel was calculated, adopting a known trap efficiency at the dam, augmented by sediment from a further unmodified tributary. Volumetric change of the estuary and adjacent nearshore was determined by comparison of surveys in 1981 and 2006. A complex pattern of estuarine surficial sediments reflects modification of the river's natural course, which is now artificially diverted to exit at Crookhaven Heads. During major flood events, the river intermittently discharges material to the shoreface at Shoalhaven Heads, its former mouth, which is impounded again by deposition of a sandy berm in the months following such storms. Between 1981 and 2006, at least 1,020,000 m3 was added to the estuary, and 1,065,000 m3 of sand was discharged to the shoreface. Sand sourced from the Shoalhaven River is retained within the northernmost of three tertiary compartments, Seven Mile Beach, as cliffed headlands and rocky reefs restrict along-shore sediment contributions from the south and inhibit leakage to the north. Balance of the budget based on shoreline accretion during 41 years is consistent with cross-shore transport and an ongoing shoreface supply rate of 1¿2 m3/m/y. Although a number of uncertainties constrain the final sediment budget, with complex patterns of erosion or accretion in response to natural events or engineering interventions, this preliminary study indicates the potential for deriving decadal-scale estimates of sediment pathways and transfer rates using geospatial analysis of terrain changes, which can provide a basis for planning and management actions.

Holocene regressive strandplains that preserve a series of former shorelines are extensive on coasts that were remote from major Pleistocene ice sheets (for example, Australia and Brazil), whereas transgressive barrier islands are typical in glacial forebulge regions (for example, North America and Europe). In strandplains, the regressive phase of strandline development was preceded by a transgressive phase during the final stages of postglacial sea-level rise. This study examines the turnaround from transgression to regression through chronostratigraphic description of three barrier systems in south-eastern Australia: Seven Mile Beach, Bengello Beach and Pedro Beach. The authors reconstruct geomorphic and depositional histories using ground-penetrating radar and vibracores along transects across the landwardmost ridges, and optically-stimulated luminescence and radiocarbon dating. At the Seven Mile Beach barrier system, extensive washover deposits are preserved that include distinctive, landward-directed, flame-shaped washover fans along the bayside shoreline of the landwardmost ridge. Landward-dipping ground-penetrating radar reflections in radargrams provide evidence of the culmination of the transgressive phase and transition into the regressive phase dominated by progradation, evidenced by the change to seaward-dipping reflections. A similar progradational plain formed at the Bengello Beach barrier system, but transgressive deposits are largely absent at the site investigated, where an eroded headland created limited accommodation space until sand supply was sufficient for progradation. The Pedro Beach barrier system depositional history is more complex. There, a smaller embayment filled rapidly during the mid-Holocene, and transgressive sands were deposited as sea level reached its present level and impounded a wetland. Accommodation space in the embayment was filled by ca 4000¿years ago. Overall, results indicate that the Holocene turnaround transition occurred between 8400 and 7000¿years ago, and was preserved at the landward margin of these three strandplains. Holocene morphostratigraphy differs among sites primarily as a function of sea level, sediment supply and antecedent topography.

Technological advances have reinvigorated the aerial photogrammetric technique using both historical and contemporary imagery, and fostered new perspectives in geomorphology studies. On sandy beaches, however, the dynamic processes, the lack of tonal contrast and reduced texture, make the application of photogrammetry extremely more difficult than in most other landscapes. This study quantifies decadal volumetric changes along the beaches of the Great Ocean Road, Australia, using improved digital surface models (DSMs) derived from structure-from-motion (SfM) photogrammetry applied to historical archives and a contemporary unmanned aerial vehicle survey. Alongside surficial sediment analysis, this approach demonstrates the potential to relate present-day to historical morphological changes at sandy beaches worldwide. The discussion highlights the influence of photographic scale, lens distortions, ground control points in segmented blocks, and the use of shoreline as a proxy of volumetric change. DSMs were derived using datasets obtained in 1946, 1966, 1971, 1977, 1986 and 2019, and compared to a 2007 light detection and ranging (LiDAR)-derived DSM. The emerging approach produced suitable DSMs for volumetric analysis, except for the 1946 dataset, which had the smallest scale and was significantly vertically offset. Volumetric losses of up to 60 m3/m of beach length were calculated for parts of Mounts Bay between 1977 and 2007, and up to 21 m3/m in recent years. At Apollo Bay, the construction of the port in the early 1950s significantly impacted the natural longshore drift to the beach. The adjacent stretch of coastline accreted at a rate of ~35 m3/m between 1966 and 2007, as a function of dredge disposal and changes in sediment transport, whereas a maximum volumetric loss of ~47 m3/m was detected further north between 1977 and 2007. A volume of ~71,330 ± 15,200 m3 was lost from the system from 2007 to 2019, despite the continued deposition along the northern section of the beach.

Shipping has been of critical importance for European colonisation and development in many parts of the world. These required the charting of safe shipping approaches, which gradually evolved into our modern nautical charts. Colonial charts provide an unique historical perspective and are of global scientific relevance for understanding the sedimentary dynamics and quantifying human alterations in the coastal zone. In areas where significant changes occurred, volumetric differences can be calculated providing a relative degree of certainty, whereas in broader areas the uncertainties are greater than the volumetric changes. In this study we looked at bathymetric and shoreline change since the mid 19th century based on information available on historical charts. We compared lead line soundings to contemporary Multibeam Echosounding (MBES) bathymetry and Light Detection and Ranging (LiDAR) data at four locations along the swell-dominated west coast of Victoria, Australia. Shorelines extracted from these charts were also used in conjunction with aerial photography and satellite imagery to show how changes following the construction of coastal infrastructure has affected natural processes of sediment transport and had long-term impacts on the adjacent coastline. We demonstrate how the construction of the port of Portland breakwaters trapped approximately 1,450,000 ± 550,000 m3 of sand, an equivalent amount of material eroded from the downdrift coastline; the closing of the southwest passage and the construction of the training walls of Port Fairy reduced the availability of sand to East Beach; the viaduct and breakwater construction at Warrnambool created a sand trap that accumulated 1,028,181 ± 575,613 m3 of sand, which made the shoreline prograde fast and reduced the harbour depth; and the dredging required to maintain the port of Apollo Bay created new land with the deposition of 291,712 ± 265,203 m3 of sand adjacent to the disposal area but caused erosion further downdrift.

Warnings issued by meteorological or oceanographic agencies are a common means of allowing people to prepare for likely impactful events. Quantifying the relationships between ocean conditions and coastal impacts, such as shoreline change or flooding of coastal assets (e.g. flooded access points, overtopping of sea walls) is crucial for developing operational coastal hazard warnings. Existing studies have largely omitted empirical data, relying on modelling to estimate total water levels and impact potentials. It is well documented that site-specific conditions influence local morphodynamics and as such, detailed data related to the physical environment is a necessary component of these existing approaches. The capacity to collect these data is not always available, however, and so an alternative approach that does no rely on detailed modelling may be necessary in some instances to identify the conditions that lead to coastal impacts. We propose an alternative empirically based approach for isolating oceanic conditions that are conducive to impact along open coasts, using two case studies from Victoria, southeast Australia: Port Fairy and Inverloch. Oceanic conditions were defined using data obtained from a WAVEWATCH III (WW3) model hindcast, assessed against newly installed wave buoys, which evidenced variation in mean conditions between the two sites. We coupled impact-based data derived from citizen-science and social media to modelled and observational data, to identify the oceanic conditions that led to impacts. We found heterogeneity in the response of the case study locations to deviations from the local mean wave characteristics and still water levels. This paper demonstrates an approach through which impact-based thresholds for erosion could be developed for management applications and early warning systems.

Sandy beaches are highly dynamic systems which provide natural protection from the impact of waves to coastal communities. With coastal erosion hazards predicted to increase globally, data to inform decision making on erosion mitigation and adaptation strategies is becoming critical. However, multi-temporal topographic data over wide geographical areas is expensive and time consuming and often requires highly trained professionals. In this study we demonstrate a novel approach combining citizen science with low-cost unmanned aerial vehicles that reliably produces survey-grade morphological data able to model sediment dynamics from event to annual scales. The high-energy wave-dominated coast of south-eastern Australia, in Victoria, is used as a field laboratory to test the reliability of our protocol and develop a set of indices to study multi-scale erosional dynamics. We found that citizen scientists provide unbiased data as accurate as professional researchers. We then observed that open-ocean beaches mobilise three times as much sediment as embayed beaches and distinguished between slowed and accelerated erosional modes. The data was also able to assess the efficiency of sand nourishment for shore protection. Our citizen science protocol provides high quality monitoring capabilities, which although subject to important legislative preconditions, it is applicable in other parts of the world and transferable to other landscape systems where the understanding of sediment dynamics is critical for management of natural or anthropogenic processes.

Progradation of the Quaternary Gilbert River megafan and Holocene delta, located in the low gradient intracratonic basin and epeiric sea of the Gulf of Carpentaria, Australia, has been enhanced by the slight fall in sea level during the late Holocene. The monsoonal floods and channel avulsions on the megafan have controlled the rate of progradation and supply of sediment to the delta front. The mixed-influence delta can be classified as a tide dominated, fluvially influenced and wave affected (Tfw) delta. Palaeogeographic reconstruction of the Gilbert River megafan, delta and palaeoshorelines was created through GIS analysis of beach and chenier ridges combined with field observations, previous cross-section data, and radiocarbon and thermoluminescence dating. Progradation rates on the Gilbert River delta are about 0.85 to 0.9 m/yr in the northern and central parts of the delta and increase to 1.8 m/yr in the southern part of the delta. Sedimentation rates vary from 0.2 to 1.0 mm/yr with a total Holocene delta volume of about 9.4 × 109 m3 and a sediment supply rate of ~1 Mm3/yr. The low sediment supply rate is characteristic of most Australian river systems but is about two orders of magnitude less than on many of the larger Southeast Asian deltas. The low onshore and offshore accommodation space on the Gilbert and Mitchell River deltas is a function of the epeiric sea setting of these deltas, and hence the thin succession of Holocene sediments on these deltas also represent a significant difference from most Southeast Asian deltas.

Historical aerial photographs are an invaluable tool in shoreline mapping and change detection in coastal landscapes. We evaluate the extent to which structure-from-motion (SfM) photogrammetric methods can be applied to quantify volumetric changes along sandy beaches, using archival imagery. We demonstrate the application of SfM-derived digital surface models (DSMs) at East Beach and Lady Bay in southwest Victoria, Australia, using photographic datasets taken in 1969, 1977 and 1986, and compare them to LiDAR-derived DSMs acquired at both sites in 2007. The SfM approaches resulted in two entire and two partial suitable DSMs out of six datasets. Good-quality DSMs were spatially continuous with a good spread of ground control points (GCPs) near the beach at Lady Bay, whereas unsuitable DSMs were mostly restricted by poor distribution and number of GCPs in spatially segmented areas of East Beach, due to limited overlapping of images, possible poor quality of GCPs and also the propagation of errors in the derived point clouds. A volume of approximately 223 000 ± 72 000 m3 was deposited at Lady Bay between 1969 and 2007, despite minimal erosion observed near the breakwater. The partially suitable dataset of East Beach indicated that beach erosion of at least 39 m3¿m-1 occurred immediately to the east of the seawall after 1977. We also discuss the drawbacks and strengths of SfM approaches as a benchmark of historical erosion assessments along sandy beaches. © 2020 John Wiley & Sons, Ltd.

The Shoalhaven River in southern New South Wales (NSW) drains a catchment of ~7000 km2, forming a barrier estuary at its mouth with a prograded strandplain to its north. Previous coring and dating across the floodplain and adjacent strandplain indicate progressive infill of the estuarine basin over the past 7000 years. Over this time the system transitioned from a wave-dominated estuary to a wave-dominated delta. The Shoalhaven River appears to have initially discharged to the sea at Crookhaven Heads, until it adopted a more direct route through an intermittently open mouth at Shoalhaven Heads; construction of Berrys Canal in 1822 now permanently links the Shoalhaven River to the adjacent smaller Crookhaven River. Airborne LiDAR reveals details of topography of prominent levees and meander scroll bars that flank the lower reaches of the river and beach/foredune ridges to the north. Sedimentological and mineralogical characteristics of modern sediment samples collected from the river channel, the beach, and the barrier reveal that the Shoalhaven River is dominated by quartz sand along its predominantly straight course through the infilled estuarine plains. This is in contrast to the tripartite classification of sedimentary depositional environments, comprising sandy fluvial delta, central mud basin, and sandy marine barrier, that characterised the initial wave-dominated estuary 7000 years ago, and is typical of most barrier estuaries in NSW. Grain size decreases downstream and sands have a higher feldspar content, and angularity, than is typical of marine sand that has been reworked in the nearshore. This fluvially-derived component is delivered to the coast intermittently by floods that re-open Shoalhaven Heads, as shown by retrospective analysis of aerial photography and satellite imagery. Grain size decreases with distance alongshore from the river mouth indicating that these sands are transported north by longshore drift to augment a gradual onshore delivery of sand within this coastal compartment. Scanning electron microscopy of selected grains implies that this fluvial sand has been contributing to incremental formation of beach ridges for much of the past 3000 years since the estuarine basin has been largely infilled, with a slight detectable acceleration in the rate of progradation.

This study demonstrates how a large-scale satellite-derived dataset can be used to investigate statistically robust trends in shoreline position over a 31-year period from 1987 to 2017, at a regional scale. Regional patterns of shoreline behaviour are important for resolving consistent or, alternatively, dissimilar patterns of past shoreline change. Such patterns are best explored using temporally frequent and spatially extensive datasets. Here we analyse satellite-derived shorelines to identify spatial patterns of hotspots of coastline change on the wave-exposed coast of Victoria in south-east Australia where rates of change exceed 0.5 m yr-1. Analysis of shoreline position changes at a 50 m alongshore interval along 900 km of the 1230 km coastline reveals a number of distinct behaviours related to coastal type (rock vs sand coast), landform, shoreline orientation and/or anthropogenic drivers of change. Overall the results show that statistically significant change in shoreline position has affected only a relatively small proportion of the study region over the last 31 years; that the proportion and rate of progradational and recessional change is similar; and that change is localised but dispersed widely along the Victorian coast. Coasts located at the entrances to large tidal inlets have shown the greatest change. The association of hotspots with embayed sandy beaches and adjacent to headlands points to the importance of geological control on shoreline behaviour. Consistent with other regional scale studies of shoreline change, this study found little regional coherence in shoreline behaviour. Instead change is predominately attributed to local factors such as the geological framework of the coast, localised hydrodynamic conditions and anthropogenic influences. Collectively, these results indicate that there is strong geologic control on shoreline erosion in Victoria due to the high diversity of landforms along the coastline; and that further analysis is required to tease out the seasonal to interannual sensitivities to changes in the historical wave climate and the secondary interaction of sediment supply for headlands and hydrodynamics for tidal inlets.

Changes to coral reef landscapes are driven by regional processes that are unique to particular localities, yet much of our global knowledge about how landscape changes manifest in coral reef environments is generalised from work undertaken on the Great Barrier Reef. We compare observations of 45 years of change on sand cays and mangroves associated with low wooded islands in Australia and Indonesia. We draw on field observations from ground referencing campaigns, alongside remote sensing technology, including satellite images and unmanned aerial vehicle campaigns. Four low wooded island sites are compared: two in the Great Barrier Reef (GBR), Australia (Nymph Island and Two Isles) and two in the Spermonde Archipelago, Indonesia (Sabangko and Tanakeke Island). The Spermonde and GBR sites can be distinguished in relation to the process regimes that entrain, distribute and deposit sediments on the reef surface thereby providing a substrate for further mangrove colonisation, particularly the presence or absence of cyclones as a key determinant of sediment transport. The influence of human populations inhabiting these sites is also an important control on their geomorphology. In the Spermonde Archipelago, local communities have altered sand cays through the development of infrastructure and converted mangroves to shrimp farms, while sand cays and mangroves have remained largely unaltered by humans on the GBR. This comparative evaluation of changes to sand cays and mangrove forest across low wooded islands emphasises the importance of considering changes within the context of their local geographic setting, inclusive of natural environmental and anthropogenic drivers of change.

Leach, C.; Kennedy, D.M.; Carvalho, R.C., and Ierodiaconou, D., 2020. Predicting compartment-scale climate change impacts related to Southern Ocean wave forcing: Port Fairy, Victoria, Australia. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1157-1161. Coconut Creek (Florida), ISSN 0749-0208. On the southern coast of Australia one of the principle impacts of climate change will be a change in wave magnitude and direction resulting from intensification of the Southern Ocean storm systems. In Victoria, Australia, this is likely to cause significant change in sediment dynamics and possible shoreline re-orientation. In this paper, Port Fairy (western coast of Victoria) is used as a case study to explore the sensitivity of this embayment to changing wave climate conditions. Bed level change rates and spatially variable sediment transport rates are investigated. The results indicate that a southerly shift in the wave climate could intensify sediment transport processes and erosional patterns in this area.

We evaluate three approaches to mapping vegetation using images collected by an unmanned aerial vehicle (UAV) to monitor rehabilitation activities in the Five Islands Nature Reserve, Wollongong (Australia). Between April 2017 and July 2018, four aerial surveys of Big Island were undertaken to map changes to island vegetation following helicopter herbicide sprays to eradicate weeds, including the creeper Coastal Morning Glory (Ipomoea cairica) and Kikuyu Grass (Cenchrus clandestinus). The spraying was followed by a large scale planting campaign to introduce native plants, such as tussocks of Spiny-headed Mat-rush (Lomandra longifolia). Three approaches to mapping vegetation were evaluated, including: (i) a pixel-based image classification algorithm applied to the composite spectral wavebands of the images collected, (ii) manual digitisation of vegetation directly from images based on visual interpretation, and (iii) the application of a machine learning algorithm, LeNet, based on a deep learning convolutional neural network (CNN) for detecting planted Lomandra tussocks. The uncertainty of each approach was assessed via comparison against an independently collected field dataset. Each of the vegetation mapping approaches had a comparable accuracy; for a selected weed management and planting area, the overall accuracies were 82 %, 91 % and 85 % respectively for the pixel based image classification, the visual interpretation / digitisation and the CNN machine learning algorithm. At the scale of the whole island, statistically significant differences in the performance of the three approaches to mapping Lomandra plants were detected via ANOVA. The manual digitisation took a longer time to perform than others. The three approaches resulted in markedly different vegetation maps characterised by different digital data formats, which offered fundamentally different types of information on vegetation character. We draw attention to the need to consider how different digital map products will be used for vegetation management (e.g. monitoring the health individual species or a broader profile of the community). Where individual plants are to be monitored over time, a feature-based approach that represents plants as vector points is appropriate. The CNN approach emerged as a promising technique in this regard as it leveraged spatial information from the UAV images within the architecture of the learning framework by enforcing a local connectivity pattern between neurons of adjacent layers to incorporate the spatial relationships between features that comprised the shape of the Lomandra tussocks detected.

Estuaries on wave-dominated coasts generally comprise three sedimentary environments: fluvial sands and gravels derived from the catchment; marine sands characteristic of the beaches and nearshore; and silts and clays that accumulate in the sheltered central basin. Estuarine transition to deltaic form occurs when geomorphological maturity is achieved during coastal evolution. Sedimentary plains become infilled and a narrow channel connects the catchment and facilitates the transport of fluvial sediments to the coast. Here, we present modern sedimentary data that supports the idea that the wave-dominated Shoalhaven system in southeastern Australia has transitioned from an estuary to delta, transporting fluvial sediments to the modern adjacent beach and contributing to coastal progradation. A total of 141 bed channel and swash zone samples were collected from the estuarine channel of the Shoalhaven River and the adjacent Comerong Island and Seven Mile Beach, respectively. Surficial sediments were subject to grain size analysis, whereas random quartz grains from selected samples were used to indicate a qualitative degree of weathering using a scan electron microscopy (SEM). Additionally, selected samples were examined for mineralogical composition using x-ray diffraction (XRD) to provide understanding of sediment transport and provenance. The dataset, one of the most comprehensive modern sedimentary coastal records in Australia, can be used to understand the sediment dynamics and support a diverse range of coastal management decisions. The experiment design and analyses also serve as a model that can be replicated elsewhere to better understand fluvial delivery of sediments to the coast. The dataset and analyses presented here support the research article entitled ¿Evolution from estuary to delta: alluvial plain morphology and sedimentary characteristics of the Shoalhaven River mouth, southeastern Australia¿ [1], to which readers should refer to for interpretation.

Prograded barriers are depositional coastal landforms which have the potential to reveal changes in the primary drivers of coastal evolution within their varied morphology. Beach ridges and intervening swales preserve paleoenvironmental records of coastal processes, relative sea level and storm events. Optically stimulated luminescence (OSL) dating of quartz grains, airborne LiDAR-derived morphology, and sediment texture and mineralogy reveal four different periods of morpho-sedimentary progradation history in the Shoalhaven barrier system in southeastern Australia. The barrier is composed of approximately 40 ridges that occupy an area of 15.2 km2, comprising an estimated sand volume of approximately 88,000,000 m3 above mean sea level. OSL dating of ten samples taken from a 940-m long transect across the Holocene system indicated that the barrier prograded at a slow rate of approximately 0.12 m/yr from 6130 ± 330 to 2400 ± 130 years ago and subsequently at a higher rate of 0.22 m/yr until 600 ± 130 years ago. More recently, an increase in historical accumulation and progradation rates has favoured development of an anomalously high foredune fronting the system with the formation of lower ridges in the past two centuries. Increasing angularity and feldspar content observed via Scanning Electron Microscope (SEM) and determined using X-ray Diffraction (XRD) analysis, respectively, imply a transition in sediment supply. Progradation has been sustained through delivery and reworking of marine sediments from offshore following the marine transgression, subsequently augmented by fluvial sands discharged to the coast by the Shoalhaven River. The adjustment in progradational rates and sediment provenance influenced the morphology and spacing of individual ridges and the regressive system as a whole. Average progradation rates for the Shoalhaven barrier, revised from those previously reported using radiocarbon dating, are considered lower than most of barriers studied in similar coastal environments around Australia, indicating the different ways that similar progradation systems have evolved.

There has been an increase in drownings over recent decades in Australia, particularly among rock fishers swept from the edge of rock platforms. Platform morphology is central to understanding what makes one stretch of coastline more hazardous than another. This paper describes the development of an easily replicable site-specific risk index for rock platforms along the Illawarra coast, southeastern Australia. It can be applied to other microtidal wave-dominated coasts where airborne topographic LiDAR data are available, without requiring nearshore bathymetric data. The index is designed to assess the relative risk of being washed into the sea and will assist coastal managers in an effort to reduce the number of injuries and drowning incidents. The approach is based on subdivision of the terrestrial seaward edge of platforms into segments, classified according to mean elevation, orientation and edge type, to model different hazard scenarios. These are combined with the popularity of individual fishing locations, assessed during fieldwork, to estimate risk. Results of 620 segments from 26 rock platforms indicate that most of these platforms lie above high tide level and that approximately 3/4 of them are of type A (ramped) edge morphology and oriented at an angle facing northeast to southeast quadrants. The most hazardous segments for southeasterly wave scenarios are concentrated along sections of the platforms between Coalcliff and Austinmer, Woonona, Port Kembla south and Red Point. The southern sections of Red Point platform were considered the most risky of all due to fishing popularity.

Static and dynamic flood models differ substantially in their complexity and their ability to represent environmental processes such as storm tide or riverine flooding. This study analysed spatial differences in flood extent between static (bathtub) and dynamic flood models (Delft3D) in estuarine environments with different morphology and hydrodynamics in order to investigate which approach is most suitable to map flooding due to storm surges and river discharge in estuarine environments. Time series of observed water levels and river discharge measurements were used to force model boundaries. Observational data, such as tidal gauge and water level logger measurements, satellite imagery and aerial photography, were used to validate modelling results. Flood extents were calculated including and excluding river discharge to quantify and investigate its effect on the mapping of flooding. Modelling results indicate that the mature estuarine system, which has largely infilled broad flood plains, requires a consideration of bottom friction and riverine discharge through dynamic modelling techniques, whereas static models may provide an alternative approach to map flooding at low cost and low computational expense in young lake-like estuarine systems that have not been infilled with sediments. Our results suggest that estuarine classifications based on geomorphological characteristics can potentially guide flood risk assessments in estuarine environments.

This study presents an analysis of shoreline change on reef islands using unmanned aerial vehicle (UAV)-derived orthomosaics and digital surface models (DSMs) collected on Sipadan Island, Sabah, Malaysia, and Sasahura Ite Island, Isabel Province, Solomon Islands. The high resolution of UAV-derived orthomosaics enabled changes in the position of the base of beach to be detected with confidence. The accuracy of the UAV-derived DSMs was assessed against equivalent topographic profiles via root-mean-square error, and found to be <0.21 m in all but one case; this demonstrates the potential for using UAV-derived DSMs to interpret three-dimensional island beach morphology and detect patterns of geomorphic change. The correlation between planimetric and volumetric change along selected beach transects was also investigated and found to be variable, indicating that a multifaceted approach including both planimetric (two-dimensional) and volumetric (three-dimensional) metrics is of value when analysing reef-island change. However, interpretations of UAV-derived data must carefully consider errors associated with global positioning system (GPS) positioning, the distribution of ground control points, the chosen UAV flight parameters, and the data processing methodology. Further application of this technology has the potential to expand our understanding of reef-island morphodynamics and their vulnerability to sea-level rise and other stressors.

Rock platforms are dangerous environments commonly subject to high wave energy on the open coast. Platform morphology is central to understanding what makes one stretch of coastline more hazardous than another, and it can be used to create site-specific morphological exposure hazard indices to assess the relative risk of being washed into the sea, assisting coastal managers in an effort to reduce the number of injuries and drowning incidents. This paper describes the use of an unmanned aerial vehicle (UAV) to derive morphological parameters for two data-poor rock platforms along the Illawarra coast of southern New South Wales, to fill the gap using an easily replicable site-specific hazard index, developed previously, that can be applied to other microtidal wave-dominated settings. The approach is based on the subdivision of the terrestrial seaward edge of platforms into segments, classified according to mean elevation, orientation and edge type, to model different weighting scenarios of predominant southeasterly and northeasterly wave direction. UAV-derived results were deemed satisfactory for all study sites, and a comparison of results derived from LiDAR for two platforms suggested that UAV data can be successfully used to guide risk policy on rock coasts, despite differences in the delimitation of the seaward edge due to tidal level during survey acquisition.

Many previous modelling studies have considered storm-tide and riverine flooding independently, even though joint-probability analysis highlighted significant dependence between extreme rainfall and extreme storm surges in estuarine environments. This study investigates compound flooding by quantifying horizontal and vertical differences in coastal flood risk estimates resulting from a separation of storm-tide and riverine flooding processes. We used an open-source version of the Delft3D model to simulate flood extent and inundation depth due to a storm event that occurred in June 2016 in the Shoalhaven Estuary, south-eastern Australia. Time series of observed water levels and discharge measurements are used to force model boundaries, whereas observational data such as satellite imagery, aerial photographs, tidal gauges and water level logger measurements are used to validate modelling results. The comparison of simulation results including and excluding riverine discharge demonstrated large differences in modelled flood extents and inundation depths. A flood risk assessment accounting only for storm-tide flooding would have underestimated the flood extent of the June 2016 storm event by 30 % (20.5 km2). Furthermore, inundation depths would have been underestimated on average by 0.34 m and by up to 1.5 m locally. We recommend considering storm-tide and riverine flooding processes jointly in estuaries with large catchment areas, which are known to have a quick response time to extreme rainfall. In addition, comparison of different boundary set-ups at the intermittent entrance in Shoalhaven Heads indicated that a permanent opening, in order to reduce exposure to riverine flooding, would increase tidal range and exposure to both storm-tide flooding and wave action.

Sea-level rise (SLR) will affect the hydrodynamics and flooding characteristics of estuaries which are a function of the geomorphology of particular estuarine systems. This study presents a numerical modelling of coastal flooding due to drivers such as spring-tides, storm surges and river inflows and examines how these will change under sea-level increases of 0.4 m and 0.9 m for two estuaries that are at different geomorphological evolutionary stages of infill. Our results demonstrate that estuarine response to SLR varies between different types of estuaries, and detailed modelling is necessary to understand the nature and extent of inundation in response to SLR. Comparison of modelling results indicates that floodplain elevation is fundamental in order to identify the most vulnerable systems and estimate how inundation extents and depths may change in the future. Floodplains in mature estuarine systems may drown and experience a considerable increase in inundation depths once a certain threshold in elevation has been exceeded. By contrast, immature estuarine systems may be subject to increases in relative inundation extent and substantial changes in hydrodynamics such as tidal range and current velocity. The unique nature of estuaries does not allow for generalisations; however, classifications of estuarine geomorphology could indicate how certain types of estuary may respond to SLR.

Carbonate production on coral reefs is responsible for the provision of beach sands, for the maintenance of seawater chemical balances and for the growth of reef structure and associated habitat complexity. Key carbonate producers including hard coral, crustose coralline algae, foraminiferal sand and Halimeda were mapped from satellite imagery (spatial resolution 2.5 m, mean overall accuracy = 81%) and an upscaling model was applied to estimate carbonate production. A sensitivity analysis was conducted to evaluate the influence of employing different calcification rates for live coral on the upscaling model. Contemporary coral reef carbonate production for the 21 reef platforms of the Capricorn-Bunker Group (southern Great Barrier Reef) is estimated to be between 489,000 and 659,000 t per year based on seawater chemistry, community composition, calcification rates and reef structural complexity (rugosity). The upscaling model was relatively insensitive to different parameterisations of live coral calcification employed, probably due to live coral being a relatively minor contributor by area (approximately 18% of total reef area throughout the study region). This suggests regional scale seafloor characteristics, such as percentage of area dominated by substrates prone to dissolution (e.g. coral rubble), have a strong bearing on calcium carbonate production and need to be given greater consideration The upscaling framework presented provides a new method for quantifying regional carbonate production that could be applied globally, and provides a valuable baseline against which future changes to carbonate production in this region can be assessed.

Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as ¿tracers¿ to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of appendages results in a decrease in Mg/Ca. BSE imaging and WDS elemental mapping provided evidence for cementation, facilitated by microbial-boring as the primary cause of increasing Sr/Ca. These novel proxies hold advantages over taphonomic measures and further provide a rapid method to infer sediment transport pathways within back-reef environments.

Linking surficial sediment patterns in reef environments to the processes that underlie their depositional dynamics enables predictions to be made of how environmental changes will influence reef-associated sedimentary landforms, such as islands and beaches. Geomorphic linkages between sediment deposition patterns and the biophysical processes that drive them are often poorly resolved, particularly at broad landscape scales where tangible statements can be made about structural changes to landforms. The present study applies geospatial techniques to link patterns in reef sediment dynamics at Lady Musgrave Island to the underlying processes driving them. In situ calcification is characterized by developing a high resolution map of the surficial calcium carbonate producing communities inhabiting the reef platform, and associated sediments across the reef flat are analysed for grain size, kurtosis, sorting and threshold bed shear stress to explore transport pathways across the reef flat and lagoon. Wave energy is modelled across the entire reef platform as a potential driver of sediment dynamics, and morphometric linkages are empirically defined between wave energy and grain size. Findings indicate that carbonate sediments are primarily sourced from calcifying communities colonizing the outer periphery of the reef platform and that sediment grain size can be reliably linked to wave energy by virtue of a linear model.