Search

The three-dimensional variability of the subaerial beach is examined for Stanwell Park Beach, New South Wales (NSW), Australia. This embayed environment has previously been studied over long time scales (decades), but not over shorter time scales (days, weeks). Embayed beaches experience rotation events during which opposite accretion and erosion patterns are observed at the extremities of the beach. To analyse this phenomenon, the beach is mapped with 10 Real-Time Kinematic Global Positioning System (RTK-GPS) surveys collected from 10th February 2016 to 14th May 2016. This study aims to examine short-term changes (days, weeks) to the morphology of the subaerial beach of Stanwell Park Beach and any factors that may influence its behaviours. We show that a short-time beach rotation event occurs over one month, caused by a large eastern swell. However, swell with a southern direction generates rip current channels on the subaerial beach face. During this particular event, the amount of sediment transported is lower than during beach rotation events. Furthermore, Stanwell Park Beach has two lagoons that can open to discharge water accumulated in these lagoons. We show that during heavy rainfall, the lagoons open, transporting sediment in surf zone and thus causing erosion. This study provides a clear demonstration of the sensitivity of embayed beaches to short-term variability in wave climate. [ABSTRACT FROM AUTHOR]

Soil erosion rates after wildfire are strongly controlled by intrinsic properties such as topography, weather, climate, soil, and vegetation. These landscape and hydroclimatic properties are important in determining post-fire erosion rates; however, their influence on post-fire erosion and their interaction with the intensity of a wildfire remains uncertain. A key limitation in resolving this uncertainty is the lack of conceptual models and frameworks for organising data related to the geomorphic sensitivity of landscapes to wildfire. Our aim is to develop a framework for consolidating understanding of post-fire erosion in the context of hydroclimatic conditions which contribute to system states, for example soil and vegetation properties, and wildfire regime. The framework is developed around a simple conceptual model where the change in erosion due to wildfire is a product of change in runoff generation and sediment supply, which is strongly related to landscape net primary productivity (NPP). We hypothesised that geomorphic sensitivity to wildfire should vary as a unimodal humped relationship across a gradient of NPP, peaking at an intermediate level. To develop this framework and to test the hypothesis, we first review intrinsic soil and vegetation properties related to the supply and transport of sediment from burned and unburned hillslopes. Net primary productivity is systematically related to these intrinsic properties because it integrates many processes involved in soil and vegetation development. Empirical data indicate a trend in the change in surface runoff generation with NPP after wildfire, peaking at an NPP of approximately 15 Mg C ha−1 y−1. A simple model of fuel availability and soil heating are correlated with a similar "humped" trend in sediment supply. These results are consistent with our conceptual model, which indicates that sediment supply and runoff contribute towards a distinct peak in wildfire effects on erosion at an intermediate level of NPP. We propose that landscapes of intermediate NPP typically have the highest quantity of fuel available to burn, which cause large changes to the soil surface properties. Landscapes at intermediate NPP also tend to produce intrinsic soil and vegetation properties that promote erosion after wildfire. The interplay between these short and long-term landscape characteristics is strongest at intermediate levels of NPP. Our proposed biogeographic model of geomorphic sensitivity to wildfire was supported by erosion data from burned hillslope and zero-order catchments studies from a range fire-prone landscapes in Australia and North America. Our proposed conceptual model will help identify areas most vulnerable to post-fire erosion changes. [ABSTRACT FROM AUTHOR]

The vulnerability of coastal wetlands to future sea-level rise (SLR) has been extensively studied in recent years, and models of coastal wetland evolution have been developed to assess and quantify the expected impacts. Coastal wetlands respond to SLR by vertical accretion and landward migration. Wetlands accrete due to their capacity to trap sediments and to incorporate dead leaves, branches, stems and roots into the soil, and they migrate driven by the preferred inundation conditions in terms of salinity and oxygen availability. Accretion and migration strongly interact, and they both depend on water flow and sediment distribution within the wetland, so wetlands under the same external flow and sediment forcing but with different configurations will respond differently to SLR. Analyses of wetland response to SLR that do not incorporate realistic consideration of flow and sediment distribution, like the bathtub approach, are likely to result in poor estimates of wetland resilience. Here, we investigate how accretion and migration processes affect wetland response to SLR using a computational framework that includes all relevant hydrodynamic and sediment transport mechanisms that affect vegetation and landscape dynamics, and it is efficient enough computationally to allow the simulation of long time periods. Our framework incorporates two vegetation species, mangrove and saltmarsh, and accounts for the effects of natural and manmade features like inner channels, embankments and flow constrictions due to culverts. We apply our model to simplified domains that represent four different settings found in coastal wetlands, including a case of a tidal flat free from obstructions or drainage features and three other cases incorporating an inner channel, an embankment with a culvert, and a combination of inner channel, embankment and culvert. We use conditions typical of south-eastern Australia in terms of vegetation, tidal range and sediment load, but we also analyse situations with 3 times the sediment load to assess the potential of biophysical feedbacks to produce increased accretion rates. We find that all wetland settings are unable to cope with SLR and disappear by the end of the century, even for the case of increased sediment load. Wetlands with good drainage that improves tidal flushing are more resilient than wetlands with obstacles that result in tidal attenuation and can delay wetland submergence by 20 years. Results from a bathtub model reveal systematic overprediction of wetland resilience to SLR: by the end of the century, half of the wetland survives with a typical sediment load, while the entire wetland survives with increased sediment load. [ABSTRACT FROM AUTHOR]

Parnell, K.E. and Smithers, S.G., 2020. Regional and local variability in coastal processes in Torres Strait, Australia, and its importance for climate change planning. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 616–620. Coconut Creek (Florida), ISSN 0749-0208. In small island states or regions, climate change planning is frequently undertaken at a country or regional level, and it is assumed that problems are common and that remedial actions can be widely applied. Community members observe treatments such as seawalls elsewhere and demand similar interventions even though they may be inappropriate. Torres Strait lies between mainland Australia and Papua New Guinea and has communities on a diverse range of islands including low muddy, coral cay, volcanic and continental island types. Approaches to solving problems caused by changing coastal processes on these varied shorelines are discussed at scales from regional to specific sites. Torres Strait has two distinct wind seasons which influence wave-driven processes and lead to seasonally reversing alongshore sediment transport, with shoreline dynamics also controlled by coastal orientation and the beach / reef flat interactions. The low muddy islands have limited management options, requiring shore protection and elevation. Shorelines on coral cay islands and the volcanic and continental islands change shape seasonally. In these settings, planning must allow for the seasonal shoreline adjustments, with structural treatments to manage longer-term shoreline trends used only to protect high-value assets and important cultural sites where alternative management responses are not possible. [ABSTRACT FROM AUTHOR]

Background and Aims Coastal protection from erosion and flooding is a significant ecosystem service provided by vegetated marine systems. Kelp beds are a dominant habitat-forming species on temperate reefs worldwide. While they are valued as hotspots of biodiversity, there is a paucity of information that supports their use in nature-based coastal defence. This includes the effectiveness of kelp beds in attenuating waves approaching the shore and how this influences sediment transport. Methods Wave loggers were deployed at paired kelp bed and control (urchin barren) treatments at four sites in Port Phillip Bay, Australia. The significant wave height offshore (exposed side) to onshore (sheltered side) of the treatment were compared to determine wave attenuation. Key Results At three sites, the wave attenuation of kelp beds was significantly less than that of the control. This result was consistent across the environmental conditions recorded in this study. At the fourth site, on average there was no significant difference in wave transmission between kelp and control. However, wave attenuation at kelp beds was 10 % greater than the control during periods of northerly winds. We highlight the importance of disentangling the effects of the reef substratum and kelp when evaluating the efficacy of kelp at providing coastal protection. Conclusions We have highlighted a significant gap in the research on ecosystem services provided by kelp beds. A greater understanding is needed on which kelp species are able to provide coastal protection, and under what conditions. Such future research is essential for providing managers and policy makers with actionable information on sustainable and cost-effective solutions for coastal defence when faced with a changing climate. [ABSTRACT FROM AUTHOR]

Shoreline variability at embayed beaches can be characterized into modes where either longshore or cross-shore sediment transport processes dominate the overall shoreline response, or there is a mixed combination of the two. To-date it has been assumed that the relative dominance of these differing modes of longshore and/or cross-shore shoreline behaviour is stationary in time. This concept is tested using a unique 43-year dataset of shoreline positions at Narrabeen-Collaroy beach (southeast Australia) and a rolling five-year window Empirical Orthogonal Function analysis, revealing the new observation of a distinct interannual variability in the dominant cross-shore and longshore modes of shoreline behaviour at this site. The dominant mode of shoreline behaviour was found to range from time periods when the cross-shore mode (referred to as the cross-shore coherent mode) comprised as much as 74 % of the overall shoreline variability, contrasting to other time periods when the alongshore mode of shoreline behaviour (longshore coherent mode) was more dominant, accounting for up to 62 % of the observed shoreline variability. Wave forcing correlation analysis suggests that these modes are controlled by varying influences of wave intensity and wave direction at interannual time scales. Consistent with previous research at this same embayment, the cross-shore coherent mode of shoreline variability appears to be controlled primarily by wave height/intensity, with stronger controls (i.e., higher correlation) when this cross-shore mode was overwhelmingly dominant. In contrast, the contribution of the longshore coherent mode appears to be controlled primarily by wave direction, but also at certain unique times in the time series by wave intensity. Analysis using available topographic and bathymetric data suggests that the observed switch in longshore versus cross-shore dominance may be triggered by extreme storm events, which cause significant and near 'instantaneous' redistribution of sediment across the entire shoreface and beach face. These results highlight the importance of considering a non-stationary shoreline behaviour at embayed beaches and the association of differing modes of dominant shoreline behaviour with interannual wave climate variability. Given observed interannual variability in deep water wave climates more broadly, it is likely that the dominant modes of shoreline variability may also occur at other embayed beaches and should be considered for numerical modelling (and prediction) of future shoreline behaviour. • A 43-year dataset of shoreline position at a wave-dominated embayment is analysed • A rolling five-year window EOF analysis reveals interannual variability in shoreline behaviour • Dominant cross-shore and longshore modes of shoreline behaviour alternate in time at interannual time scales • Modes of shoreline behaviour are controlled by different influences of wave intensity and direction parameters • Implications for adopting a non-stationary approach to coastal shoreline change numerical modelling and future predictions [ABSTRACT FROM AUTHOR]

The transfer of sediments through the landscape (sediment connectivity) depends on hydrological conditions. This study aimed at assessing changes in sediment sources engendered under extreme drought. A sediment budget model that considered hillslope sediment connectivity was applied to the Latrobe River catchment (South-east Australia) in a relatively normal period (1990–1996) followed by part of the ‘Millennium Drought’ (1997–2005). Bayesian inference was applied to optimize monthly streamflow and calibrate sediment parameters against mean annual specific sediment yields at ten monitoring stations. In 1990–1996, assessed sediment yield at the outlet was 68 kt/y; 60% of sediments originated from net hillslope erosion and 40% from streambank erosion. In 1997–2005, sediment yield decreased to 13 kt/y, 27% from net hillslope erosion against 65% from streambank erosion. During the drought, both hillslope gross erosion and hillslope sediment connectivity decreased dramatically. Streambank protection is of the utmost importance under all hydrologic conditions and especially during drought periods. [ABSTRACT FROM AUTHOR]

Al-Nasrawi, A.K.M.; Jones, B.G., and Hamylton, S. M., 2016. GIS-based modelling of vulnerability of coastal wetland ecosystems to environmental changes: Comerong Island, southeastern Australia. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 33-37. Coconut Creek (Florida), ISSN 0749-0208. Sustainable management of coastal zones has become a complicated issue. The majority of the human population lives along the coast, where their activities, together with a range of environmental changes, have altered the natural ecosystem processes and caused changes in coastal wetlands. To ensure sustainable use of coastal resources, a comprehensive set of modelling tools can help managers to make decisions. This study uses Comerong Island (southeastern NSW, Australia) as a case study to demonstrate the importance of modelling modifications to environmental change. Several data-based modelling approaches are employed to explore how human activities have altered this estuarine island setting over the last sixty years (1949 - 2014). Multi-temporal changes in land cover, shorelines and sediment delivery are estimated from remote sensing data, GIS analysis, and laboratory tests on water and sediment samples (grain size, X-ray diffraction and loss on ignition and water analysis). Results show there are significant changes to the areal extents and elevation of mangroves, saltmarshes and shorelines in the wetlands on Comerong Island over the time period of analysis, including northern accretion (0.4 km2), eastern, middle and southern erosion (0.7 km2) of the island. The implementation of modelling using GIS tools, water and sediment samples to monitor ecosystem processes, such as sediment transport and erosion/deposition, will allow resource managers to make more informed decisions by evaluating the potential consequences of the existing situation. [ABSTRACT FROM AUTHOR]

The extent to which Aboriginal Australians used fire to modify their environment has been debated for decades and is generally based on charcoal and pollen records rather than landscape responses to land-use change. Here we investigate the sensitivity of in-situ-produced 10Be, an isotope commonly used in geomorphological contexts, to anthropogenic perturbations in the southeastern Australian Tablelands. Comparing 10Be-derived erosion rates from fluvial sediment (8.7 ± 0.9 mm k.y.-1; 1 standard error, SE; n = 11) and rock outcrops (5.3 ± 1.4 mm k.y.-1; 1 SE; n = 6) confirms that landscape lowering rates integrating over 104-105 yr are consistent with rates previously derived from studies integrating over 104 to >107 yr. We then model an expected 10Be inventory in fluvial sediment if background erosion rates were perturbed by a low-intensity, high-frequency Aboriginal burning regime. When we run the model using the average erosion rate derived from 10Be in fluvial sediment (8.7 mm k.y.-1), measured and modeled 10Be concentrations overlap between ca. 3 ka and 1 ka. Our modeling is consistent with intensified Aboriginal use of fire in the late Holocene, a time when Aboriginal population growth is widely recognized. [ABSTRACT FROM AUTHOR]

Darwin Harbour, Northern Territory, Australia, is a semi diurnal macro-tidal embayment that is situated in a cyclone prone area. The tidal variations range up to 8 m with a mean tidal range of 3.7 m. The coastal area consists of mangrove fringes, sandy beaches, tidal flats, rocky shore platforms and coastal cliffs. The main morphological changes are movement of the sandbars and erosion of beaches and coastal cliffs. Sea level rise due to climate change and more intense cyclones and storm surges may exacerbate these processes with detrimental impacts on the coast and the adjacent city, particularly when occurring at high tide. To assist with coastal erosion management, a greater understanding of morphological changes is required. A two-dimensional depth averaged finite-element hydrodynamic model (RMA-2), coupled with a sediment transport model (RMA-11) from Resource Modelling Associates, have been used to deduce the sources and spatial patterns of sand erosion and deposition in the harbour. Geochemical analysis is also used to characterize the sand source(s). This paper presents hydrodynamic simulations focusing on culturally and recreationally significant beaches in Fannie Bay. Simulations indicate that the Cullen Bay sandbar is an indirect sand source replenishing Fannie Bay beaches. Respective geochemical results also show similar Rare Earth Element contents of the sand in the area. Considering the fast pace of development in and around Darwin Harbour, this study is essential in providing a fundamental understanding of coastal processes and to assist coastal and shoreline management in a tropical estuary. [ABSTRACT FROM AUTHOR]

Short, A.D., Bracs, M.A., Turner, I.L., 2014, Beach oscillation and rotation: local and regional response on three beaches in southeast Australia. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue 70, pp. 712-717, ISSN 0749-0208. Six years of monthly subaerial surveys across three embayed beaches in southeast Australia located 270 km apart are utilized to compare the response of the beaches at the local and regional scale. The three beaches (Narrabeen, Moruya and Pedro) are exposed to a similar deep water wave climate (Hs ~1.5 m, T~10 s), identical tides (spring range 1.6 m) and have similar lengths (~3 km), easterly orientation and medium to fine sand. Over the six years all three beaches had synchronous oscillation and rotation, though at different magnitudes. The lower energy Moruya beach undergoes greater beach oscillation (up to 100 m) and rotation than the higher energy Narrabeen and Pedro. The results highlight the regional scale of synchronous beach response, as well as have implication for our understanding of sediment transport and shoreline stability in relation to beach state, with the lower energy beach having a more dynamic shoreline. Furthermore the six years of data is insufficient to detect longer term trends observed at Narrabeen since 1976. [ABSTRACT FROM AUTHOR]

Multi-purpose Artificial Reefs (MPARs) are structures that may provide aesthetically acceptable coastal protection and improve recreational outcomes. Twenty years after construction of the first MPAR, Narrowneck Reef on the Gold Coast of Australia, most of the available literature is still focused on the planning, design and construction of such structures and peer-reviewed publications on their post-construction monitoring, interaction with sediment transport and impacts on coastal morphology are lacking. The aim of this paper is to evaluate how does Narrowneck Reef influence the sediment transport, and morphological changes around the anthropogenic structure, two decades after construction. To do so, a combination of ten high spatial resolution topo-bathymetric surveys from the top of the dune to the 10 m depth captured over 21 months and a series of 60 simulations using a calibrated numerical model were used. Our results demonstrate that: although not expected during design or reported in similar structures, sand can bypass the MPAR around its offshore end; under oblique waves, the longshore currents are deflected as they pass the reef, resulting in a shadow zone on the downdrift side where sand deposits; the bar crest tends to be higher on the reef's updrift side compared to downdrift, indicating that the MPAR can act as a store for sediments, as initially designed. Furthermore, the MPAR can act to stabilise the bar as it moves onshore with a downdrift offset of the inner bar as a result of low oblique wave incidence. The results presented here demonstrate that the short-term response to the MPAR twenty years after construction is more closely related to the updrift build up of sand and the deflection of longshore currents as they encounter the reef than to the dissipation of wave energy. This is because MPARs are designed to dissipate just enough wave energy so that they can achieve their recreational goal (surfing). • Beach morphodynamic state and tide level influence sediment transport pathways. • Sand bypassing occurs mainly inshore of the structure. • Under large oblique waves, sand bypass can occur offshore of the structure. • Deflection of longshore currents influence morphological response to the reef. • Bar crest is usually higher on the reef's updrift side compared to downdrift. [ABSTRACT FROM AUTHOR]

An understanding of suspended particulate matter (SPM) dynamics is of great importance to design awareness and management strategies of estuaries. Using a Laser In Situ Scattering and Transmissiometry (LISST) instrument, variations in suspended particle size volumetric concentrations (VC) and particle size distributions (PSD) were measured at six sites within Port Curtis estuary (Australia). The port is a macrotidal estuary with significant economic and environmental importance. Observed VC and SPM sizes demonstrated spatial and temporal trends strongly controlled by the variable energy conditions operating on the neap and spring cycle timescale, with a clear trend towards increasing concentrations and decreasing SPM sizes with increasing tidal ranges. Mid-estuary sites were characterized by the greatest depth-averaged VC under transitional and spring conditions. Estuary-wide mean spring tide total water profile concentrations revealed a near 300% increase in comparison to neap tide condition concentrations. In the upper-estuary sites the mean contribution of the combined 2.5–35 µm size classes to the total profile PSDs was greatest during all tidal conditions, whilst within the lower-estuary site the combined 35–130 µm size classes were greatest. Mean contributions of the largest size class (300–500 µm) dominated surface-waters throughout the estuary during the neap tide period, which when compared with the transitional and spring tide conditions, demonstrated changes of −82% to −48% and −82% to −40%, respectively. Overall, the results from this case study provides further evidence of the important influence of neap and spring tidal regimes on SPM dynamics within estuarine settings and the need to observe parameter dynamics on such timescales. [ABSTRACT FROM AUTHOR]

Abstract: The tropics of northern Australia have received relatively little attention with regard to the impact of soil erosion on the many large river systems that are an important part of Australia''s water resource, especially given the high potential for erosion when long dry seasons are followed by intense wet season rain. Here we use 137Cs concentrations to determine the erosion processes supplying sediment to two major northern Australian Rivers; the Daly River (Northern Territory), and the Mitchell River (Queensland). We also present data from five sediment samples collected from a 100km reach of the Cloncurry River, a major tributary of the Flinders River (Queensland). Concentrations of 137Cs in the surface soil and subsurface (channel banks and gully) samples were used to derive ‘best fit’ probability density functions describing their distributions. These modelled distributions are then used to estimate the relative contribution of these two components to the river sediments. Our results are consistent with channel and gully erosion being the dominant source of sediment, with more than 90% of sediment transported along the main stem of these rivers originating from subsoil. We summarize the findings of similar studies on tropical Australian rivers and conclude that the primary source of sediment delivered to these systems is gully and channel bank erosion. Previously, as a result of catchment scale modelling, sheet-wash and rill erosion was considered to be the major sediment source in these rivers. Identifying the relative importance of sediment sources, as shown in this paper, will provide valuable information for land management planning in the region. This study also reinforces the importance of testing model predictions before they are used to target investment in remedial action. [Copyright &y& Elsevier]

The Australian coast can be subdivided into three broad sedimentary provinces occupying the east, south, west, and northwest coasts. The 11,978-km long eastern province extends from the western Gulf of Carpentaria along the entire east coast to eastern Tasmania. It is characterized by tropical to temperate humid climates, quartz sediments, and overall northerly sediment transport, with significant onshore transport where shoreline orientation and wave and wind energy combine to produce massive coastal dune systems, including the world's largest sand islands. The 9587- km long south and west coast province has an arid to semiarid climate with little terrigenous sediment. Much of the coast faces into the prevailing southerly winds and the high year-round Southern Ocean swell, resulting in massive transfer of shelf and nearshore carbonate-rich sediments to the shore and into extensive coastal barrier-dunes systems, the largest dunes extending 110 km inland. The 9106-km long northwest province has a tropical arid to monsoonal climate with coral reefs fringing parts of the coast and has predominately offshore winds. While several large rivers deliver substantial terrigenous sediment to the coast, little is deposited above sea level. [ABSTRACT FROM AUTHOR]

Collocated sun photometer and nephelometer measurements at Tinga Tingana in the Australian Outback over the decade 1997-2007 show a significant increase in aerosol loading following the onset of severe drought conditions in 2002. This increase is confined to the season of dust activity, particularly September to March. In contrast, background aerosol levels during May, June and July remained stable. The enhanced aerosol loadings during the latter 5 years of the study period can be understood as a combination of dune destabilisation through loss of ephemeral vegetation and surface crust, and the changing supply of fluvial sediments to ephemeral lakes and floodplains within the Lake Eyre Basin. Major dust outbreaks are generally highly localised, although significant dust activity was observed at Tinga Tingana on 50% of days when a major event occurred elsewhere in the Lake Eyre Basin, suggesting frequent basinwide dust mobilisation. Combined analysis of aerosol optical depth and scattering coefficient shows weak correlation between the surface and column aerosol (R2 = 0.24). The aerosol scale height is broadly distributed with a mode typically between 2-3 km, with clearly defined seasonal variation. Climatological analysis reveals bimodal structure in the annual cycle of aerosol optical depth, with a summer peak related to maximal dust activity, and a spring peak related to lofted fine-mode aerosol. There is evidence for an increase in near-surface aerosol during the period 2003-2007 relative to 1997-2002, consistent with an increase in dust activity. This accords with an independent finding of increasing aerosol loading over the Australian region as a whole, suggesting that rising dust activity over the Lake Eyre Basin may be a significant contributor to changes in the aerosol budget of the continent. [ABSTRACT FROM AUTHOR]

Abstract: Analysis of the changes in rates of catchment sediment storage can provide material evidence of the impact of landscape disturbance on catchment sediment flux. A number of studies have suggested increased sediment yields from the rivers draining to the Great Barrier Reef since European settlement in the mid-nineteenth century. Many of these predictions, which indicate increases between four to ten times the pre-disturbance estimates, are based on large-scale catchment modelling that make some critical assumptions about pre-disturbance erosion rates and/or sediment delivery ratios. In addition, the majority have not been validated by empirical data. This study uses single-grain OSL dating and 137Cs depth profiles to determine pre- and post-floodplain accretion rates in Theresa Creek, a subcatchment of the dry-tropical Fitzroy River basin. We demonstrate that floodplain accretion rates have increased by three to four times since European settlement (ca. A.D. 1850). Decreased rates of floodplain accretion since the mid-twentieth century at sites contributed to by gullied terrain suggest a decrease in the supply of sediment derived from gully networks. In contrast, floodplain accretion rates from areas dominated by cultivation remain high. Widespread in-channel benches deposited since European settlement are stable and appear to be important stores of large volumes of sediment. Low magnitude increases in post-disturbance floodplain sedimentation rates (3 to 4 times), in comparison to those reported from mainly temperate climates (10 to 100 times), are attributed to the naturally high sediment loads typical of dry-tropical catchments. Consequently, previous predictions of large post-disturbance increases in sediment yields from large dry-tropical catchments draining to the Great Barrier Reef are likely to be overestimates. [Copyright &y& Elsevier]

Abstract: Fire can alter sediment sources and transport rates in river basins, changing landforms and aquatic habitats and degrading downstream water quality. Variability in the response between environments, between fires, and with time since fire makes predicting the catchment-scale effect of individual fires difficult. This study applies the fallout radionuclides 137Cs and 210Pbxs to trace the sources and transport of fine sediment through a river network following a wildfire of moderate to extreme severity in the 629-km2 eucalypt-forested Nattai River water-supply catchment near Sydney, Australia. The tracer analysis showed that post-fire erosion caused a switch in fine (<10 µm) sediment sources from 80% subsoil derived from gully and river bank erosion to 86% topsoil derived from hillslope surface erosion. The fine sediment phosphorus content increased 4–10 fold over pre-fire levels. Annual post-fire sediment yields estimated from suspended solids rating curves were 109–250 times higher than they would have been without fire. A large additional amount of sediment remained stored within the river network for at least four years, particularly in lower-gradient reaches. Analysis of a sediment core showed that surface erosion following a previous fire had supplied at least 29% of total catchment sediment yield over the past 36 years. It is concluded that wildfire can alter catchment sediment budgets in two ways. Firstly, a spatially-diffuse pulse of elevated erosion is associated with moderate or intense rainfall events in post-fire years. Secondly, pulses of elevated catchment sediment yield are driven by the timing and river sediment transport capacity of runoff events. Severe post-fire erosion and high interannual hydrologic variability can result in large sediment stores persisting within the river network for many years. Fallout radionuclide tracers are shown to be useful in quantifying fine sediment sources and transport dynamics following wildfire, and the contribution of wildfire to catchment sediment yield. [Copyright &y& Elsevier]

Abstract: This paper describes the “miniphone,” an instrument to measure aeolian saltation. This instrument is a modified electret microphone that detects the impacts of individual grains. The unidirectional miniphone is inexpensive (approximately US$10), small, and poses minimal disruption to the wind field. It can be sampled at rates up to 44,100 Hz using commonly available sound card technology or it can be interfaced with a data acquisition system. Data from deployments on beaches on Marco Island, FL, USA and near Shoalhaven Heads, NSW, Australia using sample rates of 44,100 Hz and 6000 Hz, are presented. An algorithm for identifying discrete impacts of grains is described. The number of saltation impacts was not reduced when sub-sampling a record from 44,100 Hz to 6000 Hz. The most immediate use for the miniphone is for short-term deployments to detect unsteadiness in the saltation field. [Copyright &y& Elsevier]

Identifying the erosion processes contributing to increased basin fine sediment yield is important for reducing downstream impacts on aquatic ecosystems. However, erosion rates are spatially variable, and much eroded sediment is stored within river basins and not delivered downstream. A spatially distributed sediment budget model is described that assesses the primary sources (hillslope soil erosion, gully and riverbank erosion) and sinks (floodplain and reservoir deposition) of fine sediment for each link in a river network. The model performance is evaluated in a 17,000-km2 basin in south-east Australia using measured suspended sediment yields from eight catchments within the basin, each 100–700km2 in area. Spatial variations within the basin in yield and area-specific yield were reliably predicted. Observed yields and area-specific yields varied by 17-fold and 15-fold respectively between the catchments, while predictions were generally within a factor of 2 of observations. Model efficiency at predicting variations in area-specific yield was good outside forested areas (0.58), and performance was weakly sensitive to parameter values. Yields from forested areas were under-predicted, and reducing the predicted influence of riparian vegetation on bank erosion improved model performance in those areas. The model provided more accurate and higher resolution predictions than catchment area interpolation of measured yields from neighbouring river basins. The model is suitable for guiding the targeting of remediation measures within river basins to reduce downstream sediment yields. [Copyright &y& Elsevier]

Abstract: Rivers draining to the Great Barrier Reef are receiving increased attention with the realisation that European land use changes over the last ∼150 years may have increased river sediment yields, and that these may have adversely affected the reef environment. Mitigation of the effects associated with such changes is only possible if information on the spatial provenance and dominant types of erosion is known. To date, very few field-based studies have attempted to provide this information. This study uses fallout radionuclide (137Cs and 210Pbex) and geochemical tracing of river bed and floodplain sediments to examine sources over the last ∼250 years for Theresa Creek, a subcatchment of the Fitzroy River basin, central Queensland, Australia. A Monte Carlo style mixing model is used to predict the relative contribution of both the spatial (geological) sources and erosion types. The results indicate that sheetwash and rill erosion from cultivated basaltic land and channel erosion from non-basaltic parts of the catchment are currently contributing most sediment to the river system. Evidence indicates that the dominant form of channel erosion is gully headcut and sidewall erosion. Sheetwash and rill erosion from uncultivated land (i.e., grazed pasture/woodland) is a comparatively minor contributor of sediment to the river network. Analysis of the spatial provenance of floodplain core sediments, in conjunction with optical dating and 137Cs depth profile data, suggests that a phase of channel erosion was initiated in the late nineteenth century. With the development of land underlain by basalt in the mid-twentieth century the dominant source of erosion shifted to cultivated land, although improvements in land management practices have probably resulted in a decrease in sediment yield from cultivated areas in the later half of the twentieth century. On a basin-wide scale, because of the limited spatial extent of cultivation, channel sources are likely to be the largest contributor of sediment to the Fitzroy River. Accordingly, catchment management measures focused on reducing sediment delivery to the Great Barrier Reef should focus primarily on decreasing erosion from channel sources. [Copyright &y& Elsevier]

Abstract: This paper identifies a fluvial landform, the flow chute, from Fowlers Creek, an ephemeral stream in western New South Wales, Australia. On this stream there are contrasting configurations of channel-margin and channel-bed vegetation (channel-associated vegetation). In the most common type of channel reach, large Eucalyptus camaldulensis trees grow on the bed and banks, and contribute to high channel roughness. In some reaches of about 0.5 km length, however, no trees grow below mid-bank height. The bed remains completely unvegetated, and the channel narrows to one third or less of the width of adjoining reaches immediately upstream and downstream. The coarse end of the bedload grain size population is not represented in these narrow reaches, indicating that the coarsest grains are efficiently moved through them, overpassing finer sediments. These reaches evidently experience higher flow speeds than the remainder of the channel, are here termed flow chutes. The bed material within them is often moved as dunes that remain upon flood recession. Each flow chute ends with a reverse bed slope and just downstream of the terminus the channel widens, resulting in the deposition of coarse bed load in the form of gravel and cobble bars. The reverse bed slope detains water in the flow chutes, which remain as major pools or waterholes for months following flood events. The large and apparently old trees lining the flow chutes imply that these channel features are stable over periods of 102–103 years, in contrast with the behaviour of reaches with vegetated beds, where bank erosion and local lateral channel migration and/or widening are active. Flow chutes thus appear to be stable, equilibrium fluvial landforms. [Copyright &y& Elsevier]

The influence of the El Niño-Southern Oscillation (ENSO) on NSW coastal storm severity was investigated by comparing the yearly mean Southern Oscillation Index, SOI, with the yearly averaged storm severity Ω measured at the NSW coast. It was found that Ω correlates well with SOI, i.e., Ω generally increases with SOI. The probability distributions of storm peak wave height and yearly mean SOI were also studied and were found to follow a Gumbel distribution. A simple linear relationship between extreme wave height and yearly mean SOI was then derived. At the NSW coast or at other coasts with similar wave climates, coastal recession and increased coastal damage may be expected in La Niña years, while beach recovery and reduced coastal threat may be expected in El Niño years. [ABSTRACT FROM AUTHOR]

Abstract: This study evaluates an experiment in river rehabilitation which uses large wood to stimulate and emulate natural system processes in an effort to reverse channel degradation, excess sediment transport and habitat simplification that has resulted from two centuries of human induced disturbances, particularly desnagging. The experiment involved the reintroduction of 436 logs (350 t) within 20 engineered log jams (ELJs) over an 1100 m reach. Commencing in 1999, the experiment was set up as a standard BACI design, with a control reach 3 km upstream. In the 5 years since implementing the rehabilitation strategy, the study reach has experienced five floods greater than the mean annual, and a further five events capable of mobilising the gravel bed. Five surveys of channel terrain have been completed since treatment implementation, and the changes to net sediment storage and morphologic diversity assessed in comparison to the control reach. Seven surveys of the fish population in the reach have also been undertaken during the project to measure the ecological response to the introduced wood. The experiment has demonstrated the effectiveness of ELJ technology in achieving engineering and geomorphic goals. To date, the treatment has halted further degradation of the river and increased sediment storage, with the test reach now storing, on average, 40 m3/1000 m2 more sediment than in the control. These values, it would appear, represent a new reach-scale dynamic equilibrium storage level over decadal timescales. Additional sediment storage amounts to 3.5 m3/m3 of wood added. At the reach scale this additional storage represents a reduction of just 2% or less of the post-European expansion in channel capacity, suggesting far greater efforts are required than those employed here to reverse the cumulative effects of 180 years of channel erosion and simplification. Pool and bar area in the test reach increased by around 5% and 3.5%, respectively, while the corresponding values in the control were around 1.5% and 1%, respectively. Two indices of morphologic diversity were measured for each bed survey: the standard deviation of 3D residuals of change compared with the baseline survey (SDiΔ3D); and the standard deviation of thalweg residuals from the line of best fit (SDiTR). The SDiΔ3D index shows both reaches increased in complexity through the study with the treatment increasing more than the control (0.37 and 0.29, respectively). The SDiTR index does not detect clear changes because of the low signal to noise ratio, however, it does suggest the test reach was more complex than the control at the outset. The observed increase in fish abundance after the first 12 months of monitoring, reported previously, is now far less distinct 4 years on — a pattern seemingly reflecting the relatively minor increases in critical pool habitat and habitat diversity over the same period. Although no significant differences were detectable in fish species richness or total abundance from the reach aggregate data after 4 years, analysis of individual structures show them to be high quality habitat for native fish compared to the rest of the reach and the upstream control. These results highlight the challenges river managers face in achieving measurable improvements in the health of aquatic ecosystems in highly altered rivers. Managers must confront hysteresis in a biophysical and institutional sense when attempting to reverse the degradation of rivers. The scale of treatment implemented in this experiment was at the upper end of the spectrum of rehabilitation efforts currently being undertaken in Australia, suggesting that far greater resources and longer timescales are required to achieve the levels of improvement in the diversity of stream habitat expected by the community. The study also highlights problems with the strategy of attempting to meet multiple objectives within a reach scale rehabilitation project. While this treatment successfully met some geomorphic study objectives, maximising the benefits for fish habitat would require a strategy focused primarily on the creation of complex woody habitat within deeper pools, particularly pools immediately below riffles. [Copyright &y& Elsevier]

Banks Strait, Tasmania, Australia, has been identified as a potential site for the deployment of tidal turbines. In this study, the characterization of sediment transport and large sand waves for this site is performed. Observations of bed level change collected from surveys in 2018 showed a migration of large sand waves over a period of nine months. Migration rates in an excess of one hundred meters for nine months were found, which are large compared to the rate reported at other coastal sites, by several meters per year. A validated hydrodynamic model is coupled with a morphodynamic model to perform sensitivity tests and identify what parameters influence migration to better understand sediment dynamic in the Banks Strait. Numerical analysis showed a constant shift of the sand waves profile in an eastward direction, consistent with the observations. This migration was strongly linked with tidal asymmetry, with a residual current flowing towards the east. The principal parameters driving the migration of sand waves in the Banks Strait were found to be sediment sorting, bed friction and residual current. This study gives new insights for the seabed of Banks Strait and provides an assessment of the natural variability of sediment for futures tidal farms deployments. [ABSTRACT FROM AUTHOR]

The development of tidal energy in Australia is still a challenge with few studies performed on the characterisation of the resource, due to the difficulty to acquire data and uncertainties about the influence of this anthropogenic activity on the marine environment. Changes in flow could lead to alterations in sediment transport and have further influence on the marine habitat. A case study in a promising area, Banks Strait (Australia), was created using high resolution 2D and 3D models validated against in situ data to investigate changes to hydrodynamic conditions with two scenarios of tidal farms (100 and 300 turbines). Comparison between 2D and 3D is performed to find the best compromise between model accuracy and computational time for preliminary assessment. Changes to current speed and bed shear stress over a 35 day period were found to be localised around the tidal farms and did not extent more than 7 km from the farm (300 turbines) for both 2D and 3D. The results showed that for near field and far field, 2D models are sufficient to give a first approximation of the hydrodynamic influence of tidal farm deployment on its environment. [ABSTRACT FROM AUTHOR]

Human activities are known to impact the physical template of river channels. These impacts can result from deliberate, direct modifications as well as via indirect processes linked to broadscale landscape change. This study examined changes in the physical template of the Barwon-Darling River, a dryland river in southeastern Australia. Historical longitudinal profiles from the late 1800s were compared with contemporary profiles derived from high-definition, side scanning sonar. Comparisons focused on characterising waterhole features as they are a critical biophysical component of dryland rivers. The use of historical data presented several challenges related to small sample size and suspected sampling bias in the historical survey. However, this study demonstrates that these issues are not insurmountable providing the limitations and uncertainties with the data are acknowledged and data analyses are limited to parameters that can distinguish genuine landscape change. The findings revealed a dramatic change in the physical template of the Barwon-Darling River over a 120-yr period. Waterhole depths and distances between waterholes have been altered significantly. The magnitude and trajectory of change was found to be scale-dependent, with the greatest observable change aligned with the presence or absence of low-level weirs. Waterholes influenced by low-level weirs have increased in depth because of localised impoundment, whilst the distance between deep waterholes (>4 m in depth) has declined substantially. In contrast, the maximum depths of waterholes located outside the influence of weir pools has declined by 1.6 m and the distance between deep waterholes has more than doubled in several reaches. These declines are likely to be caused by sediment accumulation in waterholes associated with anthropogenic increases in sediment flux and a decline in the river's capacity to entrain and transport sediment throughout the system. • Waterhole depths and distances between waterholes have been altered over 120 years. • The trajectory and rate of change is aligned with low level-weir occurrence. • Maximum waterhole depths declined substantially in non-weir pool locations. • Distances between deep waterholes have doubled in several non-weir pool locations. • Historical data can be valuable if data limitations are acknowledged. [ABSTRACT FROM AUTHOR]

Numerical coastal erosion models are used by engineers to predict the magnitude of storm erosion at the coastline. In particular, the 'dry' region of the beach, extending landwards from the waterline to include the beach face, berm and dunes, is a particular focus of interest to managers, planners and other coastal practitioners. However, the choice of the most appropriate numerical model to predict subaerial beach erosion requires careful consideration of the strengths and limitations of each model, and the quality and quantity of field data available for both model calibration and prediction. While no model can perfectly replicate observed upper beach erosion, this study specifically assesses the quantity of field calibration data required to achieve optimum model performance for coastal storm erosion modelling applications. Two of the most commonly used, but differently formulated, coastal erosion profile models are compared: the process-based and more complex model XBeach, and the semi-empirical and significantly simpler model SBEACH. A rigorous calibration technique (the Generalised Likelihood Uncertainty Estimation) is applied to both models, using a comprehensive dataset of pre- and post-storm topographic measurements collected over four differing storm events at Narrabeen-Collaroy Beach in southeast Australia, as well as at two adjacent embayed beaches. When applying the two numerical models using their default parameters (i.e., with no model calibration), SBEACH was found to be the more skilful model and XBeach default parameters were found to have no predictive skill along this stretch of coastline. Once calibrated with detailed field observations obtained before and after a single storm event, XBeach validation skill rose considerably and provided predictions of subaerial beach profile change with greater skill (87% better Brier Skill Score on average for the same calibration data) than SBEACH. Overall XBeach model performance was found to marginally improve when field observations obtained from additional storm events were included in the calibration process, whereas SBEACH showed negligible improvement. A comparison was made of the options available for transferring previously-calibrated parameters to adjacent locations, finding spatial proximity to be the most sensitive indicator of model performance for a transferred parameter set. Due to the alongshore variability in pre-storm topography as well as wave exposure at the sites tested, the spatial coverage of data was more important for the calibration process than the magnitude of the individual storm(s) used for a specific calibration. The results of this study underscore the need for careful consideration of the available calibration field data when choosing and optimising coastal erosion models. • Default XBeach parameters were found to be non-skilful at coastal sites in southeast Australia. • The XBeach model outperformed the SBEACH model when one or more calibration storm event field datasets were available. • Collection of calibration pre- and post-storm field data at specific locations of interest was important. • Spatial proximity was found to be a good performance indicator of calibrated parameter values transferred to new locations. [ABSTRACT FROM AUTHOR]

Modelling investigations into the local changes in the shoreline resulting from enhanced atmospheric greenhouse gas concentrations and global climate change are important for supporting the planning of coastal mitigation measures. Analysis of Global Climate Model (GCM) and Regional Climate Model (RCM) simulations has shown that Lakes Entrance, a township located at the northern end of Ninety Mile Beach in south-eastern Australia, is situated in a region that may experience noticeable future changes in longshore winds, waves and coastal currents, which could alter the supply of sediments to the shoreline. This paper will demonstrate a downscaling procedure for using the data from GCM and RCM simulations to force a local climate model (LCM) at the beach scale to simulate additional nearshore wind-wave, hydrodynamic and sediment transport processes to estimate future changes. Two types of sediment transport models were used in this study, the simple empirical coastline-type model (CERC equation), and a detailed numerical coastal area-type model (TELEMAC). The two models resolved transport in very different ways, but nevertheless came to similar conclusions on the annual net longshore sediment transport rate. The TELEMAC model, with the Soulsby-Van Rijn formulation, showed the importance of the contribution of storm events to transport. The CERC equation estimates more transport during the period between storms than TELEMAC. The TELEMAC modelled waves, hydrodynamics and bed-evolutions are shown to agree well with the available observations. A new method is introduced to downscale GCM longshore sediment transport projections using wave-transport-directional change parameter to modify directional wave spectra. We developed a semi-empirical equation (NMB-LM) to extrapolate the ~3.7-year TELEMAC, storm dominated transport estimates, to the longer ~30-year hindcast climate. It shows that the shorter TELEMAC modelled period had twice as large annual net longshore sediment transport of the ~30 year hindcast. The CERC equation does not pick up this difference for the two climate periods. Modelled changes to the wave transport are shown to be an order of magnitude larger than changes from storm-tide current and mean sea level changes (0.1 to 0.2 m). Discussion is provided on the limitations of the models and how the projected changes could indicate sediment transport changes in the nearshore zone, which could impact the coastline position. [ABSTRACT FROM AUTHOR]

Sedimentary provenance studies can provide a finely-tuned record of sediment sourcing and tectonism where vertical provenance changes generally reflect either basin-forming tectonic processes or far-field orogeneses generating sediment that overwhelms local sediment supply. Basin-fill histories receiving extrabasinal sedimentation can provide valuable links between basins and tectonic processes operating in different parts of a continent. This study focuses on an example of a continental basin that was influenced by a far-field tectonic event causing a major provenance change. The mid-Mississippian Drummond Basin (Queensland, Australia), preserves a thick (>5 km), large-volume (~235,000 km3) succession of predominantly fluviatile, coarse-grained, cratonic-derived sandstones and conglomerates that define an abrupt, basin-wide provenance change supplanting initial rift-related intrabasinal volcanism and related sedimentation. Shifts in sandstone compositions are extreme, switching from Q28F19L53 to Q80F8L12 and where quartz changes from volcanic to plutonic varieties. Paleocurrent data, in combination with petrographic and facies analyses, indicate sediment supply from beyond the S/S-W basin margin, and require the transport of high loads of coarse-grained material to be maintained over an unusually long distance: ~470 km along the basin axis, in addition to an unknown distance from the extrabasinal sources. To understand the causes of the profound provenance change recorded in the basin, and to constrain the source terrain(s), a comprehensive detrital multi-dating study was undertaken. While many sedimentary provenance studies have been reliant on U-Pb detrital zircon dating, it has been increasingly recognised that this method alone cannot provide clarity on the source region of sedimentary rocks, as it only truly identifies the ultimate igneous source terrain, rather than immediate sedimentary or metamorphic sources. Here, utilising multiple techniques provides broad coverage of the closure temperature spectrum, from high-closure-temperature U-Pb zircon (~900-1000oC), through moderate-temperature U-Pb rutile (~500-600oC), to low-temperature 40Ar/39Ar systems in muscovite (300-400oC) and biotite (~280-350oC). Twenty-nine samples were collected from different stratigraphic formations and multiple basin locations, allowing 4-D insights into the propagation of detrital mineral age signals across the basin. LA-ICP-MS U-Pb zircon dating was performed on 27 samples (2,544 analyses in total) and revealed a complex age pattern dominated by <440 Ma ages, as well as several older populations, notably of Pacific-Gondwanan and Grenvillean ages. To investigate potential metamorphic sources, 18 detrital rutile samples were analysed for a total of 1,431 analyses. Both concordant and discordant rutile data are dominated by Pacific-Gondwanan ages, with a minor ~1547 Ma detrital population appearing mid-succession. 40Ar/39Ar detrital muscovite (2 samples) and biotite (1 sample) dating was undertaken and yielded 422-439 Ma ages which are interpreted to record the timing of the source terrain cooling/exhumation. The multi-dating results reveal a broad, mixed source region, including a significant syn-depositional volcanic contribution (<360 Ma zircon population), igneous basement rocks to the S and W of the basin (older zircon populations; micas), recycled sedimentary rocks (Pacific-Gondwanan and Grenvillean zircons), and high-grade metapelitic rocks (rutile). The timing and nature of the provenance change recorded in the Drummond Basin are consistent with it being driven by the contemporaneous but far-field intraplate Alice Springs Orogeny of central Australia. [ABSTRACT FROM AUTHOR]

Sennes, G., Castelle, B., Bertin, X., Mirfenderesk, H. and Tomlinson, R.B., 2007. Modelling of the Gold Coast Seaway tidal inlet, Australia. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 1086 – 1091. Gold Coast, Australia, ISSN 0749.0208 The Seaway entrance is a tidal inlet located on the Gold Coast (Queensland, Australia). Before the 80s, the entrance was highly variable in terms of inlet location and sand bar characteristics. The Seaway stabilisation with two training walls combined with an artificial sand bypassing system were completed in 1986 with the aims of fixing the entrance, maintaining a safe navigable channel, preventing shoreline erosion to the north and a buildup of sand to the south. Despite these training works, the dynamics of the Seaway is still poorly understood: channel infilling problems and navigation issues remain. For these reasons, the present study aims to develop a comprehensive model of the entrance to be used for further dredging and training work issues. The present investigation is carried out in two stages. The first stage is based on historic aerial photograph analysis of the Seaway before training works. It shows that the mouth was periodically driven northward by the longshore drift, with an average cycle time of 10 years. The second stage is based on numerical modelling after training works. Refined Delft3D modelling is undertaken with a 2DH approach on the Seaway area, taking into account the training walls and the sand bypassing system. This local model is coupled with MIKE21 implemented on a regional scale to provide accurate tide and flow forcing at the boundaries. After calibration, the analysis of flow patterns shows that the Gold Coast Seaway is ebb-dominated and that the more intense flow velocities are observed in the northern channel. Morphological evolution of the inlet is also investigated with a qualitative approach. Results indicate the pathways and rate of the sand movement within the tidal inlet in its current configuration and provide information about a planned 400 m extension of the southern training wall. A significant calibration work, involving sediment transport and bathymetry measurement, is required for the model to be used as a comprehensive tool for further dredging and dumping strategies within the entrance. [ABSTRACT FROM AUTHOR]

Kim, I.H and Lee, J.L., 2007. Changes in the sediment transport pattern after breakwater extension at Anmok Port, Korea. Journal of Coastal Research, SI 50, 1046 – 1050. Gold Coast, Australia, ISSN 0749.0208 The breakwater extension at Anmok Port has resulted in erosional stresses along the shoreline immediately south of the port. In this study, the downdrift affects caused by the breakwater extension are investigated through both analytical and numerical model approaches. The analytical approach is accomplished through littoral drift vectors which are estimated in this study from measured volumetric changes by using an inverse matrix. The model has five components including a parabolic equation for wave transformation from the deep ocean to the coastal region, depth-integrated shallow water equations for calculating coastal current, diffusion-advection equations for sediment transport and a mass conservation equation of bottom-layered sediments for predicting depth changes. Analyses of sand transport processes in the vicinity of Anmok Port resulted in the conclusion that a heavy eddy generated in a sheltered zone is the predominant erosion mechanics at the site and therefore, the bypassing system is considered as a necessary device in order to basically solve the concurrent problem such as heavy accumulation of sediments in a port entrance and the closure of a stream mouth in the east coast as well as the eroding problem. [ABSTRACT FROM AUTHOR]

Dias, J.M., Abrantes, I. and Rocha, F., 2007. Suspended Particulate Matter Sources and Residence Time in a Mesotidal Lagoon. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 1034 – 1039. Gold Coast, Australia, ISSN 0749.0208 In the frame of this work the suspended particulate matter (SPM) concentration was measured in February 2002 in seven sites of Ria de Aveiro (located in its four main channels) during one tidal cycle of a neap tide event (at approximately 2-hour intervals, including high tide and low tide measurements) and its mineralogical composition was identified. The purposes of this work are to identify the main sources of sediments for these locations (ocean or rivers), as well as to determine the sediments residence time for this locations and their paths along the channels. The methodology adopted consisted in applying a lagrangian model coupled to a previously calibrated hydrodynamic model of Ria de Aveiro to study the dispersion and mixing processes of passive particles during the sampling period. Considering the sediments represented as passive particles, lagrangian models allow the simulation of sediments transport paths and the computation of residence times. Several simulations were performed in order to simulate the surveys conditions and understand the dynamics and origin of measured SPM. The model results are supported by textural, mineralogical and concentrations field data, revealing that it may constitute an important tool to study the lagoon sediments dynamics and origin. [ABSTRACT FROM AUTHOR]

Plecha, S., Sancho, F., Silva, P. and Dias, J.M., 2007. Representative waves for morphological simulations. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 995 – 999. Gold Coast, Australia, ISSN 0749.0208 In the present study, a set of representative waves is derived for the coast adjacent to the Ria de Aveiro, such that it is morphologically equivalent to the complete wave regime. Different schematising methodologies are presented, based on the principles of conservation of wave energy and equivalent longshore sediment transport capacity over the beach profile. Firstly, the sediment transport capacities due to the whole set of waves is computed and then various sets of representative waves are proposed based on the principles above. The most suitable set is selected by taking into account the dominant sediment transport processes at the selected site. The representative waves can be used to significantly reduce computational time in morphological models, by reducing the number of different sea states that characterise the annual wave climate. This simplified nearshore wave regime shall provide the wave effects into the sediment transport formulae and the hydrodynamical model. [ABSTRACT FROM AUTHOR]

Jabbari, E. and Saeedpanah, I., 2007 Simulation of sediment transport in coastal areas with Meshless Local Petrov-Galerkin scheme. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 943 – 948. Gold Coast, Australia, ISSN 0749.0208 The phenomenon of sediment transport plays an important role in the design of coastal structures. Lack of enough attention to the sediment transport process at coastal areas would cause considerable problems distribution such as filling the ports basins by sediment in a short time. In this paper, the truly Meshless Local Petrov-Galerkin (MLPG) scheme is extended for computation of concentration distribution of suspended sediment in depth and at different distances from a coast line, governed by the time-averaged advection-diffusion equation. The present method is a truly meshless method based only on a number of randomly located nodes. The meshless method is based on a local weighted residual method with the Heaviside step function and quartic spline as the test functions respectively over a local subdomain. Moving Least Square approximation (MLS) is employed in shape function construction for approximation of a gauss point. Due to dissatisfaction of kronecker delta property in MLS approximation, the penalty method is employed to enforce the essential boundary conditions. The results of the simulations were compared with the results of the simulations done by van Rijn. The comparison of computational results shows that the developed method is capable of accurate resolution of concentration distribution of suspended sediment at depth and in different distances from the coast line. [ABSTRACT FROM AUTHOR]

Guard, P., Teakle, I., Nielsen, P. and Baldock, T.E., 2007. Modelling Sheet Flow Sediment Transport Using Convolution Integrals. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 937 – 942. Gold Coast, Australia, ISSN 0749.0208 A new method for the prediction of instantaneous sediment transport rates is presented based on the use of convolution integrals. The convolution integral technique allows solution of the governing differential equations in the time domain while accurately representing important unsteady flow effects. This technique overcomes many of the limitations of simple quasi-steady sediment transport models and does not require the computational effort of more detailed process-based models. The present model has been parameterised using results from a more detailed process-based two-phase model. Preliminary results indicate that the technique is successful in predicting net transport rates in oscillatory flow tunnel experiments in the sheet flow regime. Extension of the model to other sediment transport regimes and incorporation of real-wave effects such as boundary layer streaming is possible. [ABSTRACT FROM AUTHOR]

Coughlan, C., Vincent, C.E., Dolphin, T.J. and Rees, J.M., 2007. Effects of tidal stage on the wave climate inshore of a sandbank. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 751 – 756. Gold Coast, Australia, ISSN 0749.0208 Modelling of the processes that link the movements of offshore sandbanks to erosion and accretion of neighbouring beaches was undertaken to improve understanding of the links between sandbanks and beaches in order to inform coastal management. The effect of varying tidal stage on the wave climate inshore of a sandbank was examined using the TELEMAC suite of numerical models. Longshore sediment transport was calculated using the CERC formula to investigate changes to the magnitude and pattern of coastal erosion/accretion according to tidal stage using waves from two of the most frequent directions. Tidal stage has a significant impact on the inshore wave climate, varying wave heights by up to 0.5 m and increasing tenfold the magnitude of the longshore sediment transport. Tidal elevation appears to play a more important role than the tidal currents, with wave heights and longshore sediment transport maximum at high water. The pattern of alongshore erosion and accretion varies more strongly with wave direction than tidal stage. [ABSTRACT FROM AUTHOR]

Vila-Concejo, A., Short, A.D., Hughes, M.G. and Ranasinghe, R., 2007. Flood-tide Delta Morphodynamics and Management Implications, Port Stephens, Australia. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 705 – 709. Gold Coast, Australia, ISSN 0749.0208 Port Stephens is a drowned river valley estuary located in SE Australia. Its flood-tide delta is part of the morphological transition between the wave-dominated open coast and the tide-dominated estuarine environment. The sand surface of the flood-tide delta is subject to episodic disturbance by large ocean waves that penetrate into Port Stephens. Moreover, the flood-tide delta is a dynamic feature that responds to variations in the forcing mechanisms. Shoal Bay, Nelson Bay and Jimmy's Beach located on both sides of the entrance have experienced severe erosion for the last 40 years, resulting in expensive shoreline management controls. The evolution of these beaches has been linked to the flood-tide delta morphodynamics. Most of the morphologic features in outer Port Stephens have undergone erosion processes during at least the last 40 years. Yacaaba Head seems to be the only morphologic unit that has undergone sedimentary accretion. Results from numerical models obtained by other authors found eastward directed sediment transport occurring on the eroding beaches. Field measurements and observations show westward sediment transport. Further studies to identify the sediment exchange mechanisms and controls are needed to clarify the morphodynamics of the outer part of Port Stephens. [ABSTRACT FROM AUTHOR]

Barnes, M.P. and Baldock, T.E., 2007. Direct Bed Shear Stress Measurements in Laboratory Swash. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 641 – 645. Gold Coast, Australia, ISSN 0749.0208 Knowledge of the boundary shear stress in the swash zone is essential for the accurate prediction of sediment transport rates and beach morphology. The variation of bed shear stress over the swash cycle has been investigated directly using a novel shear plate instrument. Laboratory measurements of bed shear stress, flow depth, and fluid velocity were obtained for dam break waves and bore generated swash. For dam break and swash uprush, a large positive (landward) spike in bed shear stress has been measured at the fluid tip followed by a rapid decay throughout the flow interior. The maximum measured negative (seaward) bed shear stress occurring in the swash backwash flow interior is several times smaller than the measured peak uprush bed shear stress. Surface elevation measurements indicate a virtually zero gradient at the uprush tip, a predominately adverse gradient throughout the decelerating uprush interior, and a weakening favourable gradient throughout the entire accelerating backwash. Measured pressure gradients indicate negative (seaward) total acceleration for the majority of the swash cycle. Considering that fluid velocity and total acceleration favours seaward sediment transport for a single swash event, the positive peak in bed shear stress at the uprush tip may in fact be a significant contributor towards the observed uprush sediment transport efficiency. [ABSTRACT FROM AUTHOR]

Butt, T., Russell, P., Miles, J. and Turner, I., 2007. Sediment Transport Processes in the Swash Zone of Sandy Beaches. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 636 – 640. Gold Coast, Australia, ISSN 0749.0208 In recent years, there has been a general resurgence of interest in the swash zone. However, it still remains one of the least well understood parts of the coastal zone. The sediment transport and resulting morphological changes in the swash zone are notoriously difficult to predict. Energetics-type formulations are less useful for predicting sediment transport in the swash zone than further seaward, particularly as conditions become more reflective. One reason for this is the existence of processes in the swash zone such as bore turbulence, inexfiltration and sediment advection. This paper presents an overview of the findings from a recent 3-year UK swash-zone field study with particular focus on these processes and the way their influence varies according to the prevalent hydrodynamic and morphological conditions. There is now evidence that (a) the influence of bore turbulence decreases with increasing dissipativeness, (b) in-exfiltration biases the transport onshore or offshore above and below a particular grain size respectively and (c) sediment advection may bias the transport onshore in reflective conditions and offshore in high-energy dissipative conditions. [ABSTRACT FROM AUTHOR]

Baldock, T. E., Manoonvoravong, P. and Pham K. S.., 2007. Beach face morphology and surf beat sediment transport. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 631 – 635. Gold Coast, Australia, ISSN 0749.0208 Predicting the evolution of the beachface is important in terms of coastal protection, recreation and environmental sustainability. Swash zone sediment transport plays a major role in this morphological response. However, despite recent advances in swash zone modelling and data collection, specific details are lacking, notably the cross-shore variation in net transport rates, the influence of surf beat and wave groups on swash sediment transport and the effects of the feedback between the surf and swash zones. This paper provides novel data from carefully controlled small-scale laboratory experiments investigating surf beat sediment transport. The data include very detailed observations of the cross-shore distribution of net sediment transport in the surf and swash zones for both eroding and accreting beaches. Further, these distributions are contrasted for monochromatic waves, monochromatic waves with surf beat and bichromatic wave groups with surf beat. In this case, free surf beat is shown to reduce nearshore wave heights and reduce short wave velocity amplitudes. Free surf beat is found to promote onshore sediment transport under accretionary conditions and reduce offshore transport under erosive conditions. Hence, the free surf beat tends to transform the beach toward a reflective state and possibly protects the beach. However, a bichromatic wave group shows the opposite effect. Additional data show the influence of the beach face evolution on the onshore migration of longshore bars, illustrating coupling between swash and surf zone morphology. [ABSTRACT FROM AUTHOR]

Figueiredp S. A., Cowell P. and Short A. D., 2007. Intermittent backbeach discharge to the surfzone: modes and geomorphologic implications. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 610 – 614. Gold Coast, Australia, ISSN 0749.0208 The exchange of sediment between dune-beach and surfzone is influenced by the elevation of the water table relative to the surface. Locations where the discharge of water from the backbeach to the surf zone is established, in the form of seepage, washouts and lagoons openings are associated with seaward transport of sediment. The generation and maintenance of washouts at the beach are mainly related to water table levels, sediment characteristics and frequency of precipitation. Their source area is chiefly the water table and swamp areas behind foredunes; in contrast, the pocket lagoons openings and intermittently open lagoon (ICOLL) breaching are due to high beach water tables and lagoons level immediately landward of the berm. The locations of surface discharge points may be preferential places for the establishment of subsequent coastal processes, as a consequence of a lower beach and dune line. This may influence the longer term-large scale coastal evolution of the dune, back beach and sediment budget. [ABSTRACT FROM AUTHOR]

Kim, Chang S. and Lim, H. S., 2007. Safety criteria on water depth, offshore distance and dredging volume in marine sand mining operation in Kyunggi Bay, Korea. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 507 – 510. Gold Coast, Australia, ISSN 0749.0208 A model study to investigate the sediment transport and cross-shore sediment flux near the shoreline is conducted for a marine sand mining operation in Kyunggi Bay, Korea. A modelling effort using a 3-dimensional model, a wave model and a wave-current sediment flux model has been applied to the study area. The ROMS (Regional Ocean Modelling System), SWAN and the HARRIS and WIBERG (2001) model represent the basic modules of the 3-dimensional hydrodynamics, wave transformation in shallow water and sediment transport respectively. The goal of the current study is to estimate the cross-shore sediment flux to quantify the erosion vulnerability of the shoreline by imposing various dredging intensity as in real situation. Being the wave and current interaction considered, the sediment transport model adopts the outputs of ROMS and SWAN for any designated time and space in the computation field. The realistic hydrodynamic conditions and wave field obtained from 20-year wave statistics enhance the prediction of the erosion process according to the water depth, offshore distance from the shoreline and dredging intensity (volume and frequency etc). [ABSTRACT FROM AUTHOR]

Alsina, J.M., Sánchez-Arcilla, A., Gironella, X. and Baldock, T.E., 2007. Design of scaled movable bed experiments using numerical models. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 379 – 383. Gold Coast, Australia, ISSN 0749.0208 Scaling designs for mobile bed short wave experiments have been analysed using a suite of numerical models to test different sediment scaling configurations. The numerical simulations have revealed that geometrical sediment scaling gives similarity in the boundary layer flow but the sediment transport mode switches from bed-load in the prototype to suspended-load in the model. This is due to the high relation of prototype to model sediment sizes. However, scaling to maintain the relative fall speed allows smaller sediment size relations and closer similarity in the dominant transport processes. A set of corrections have been proposed to minimise the scaling effects in sediment transport rates and bottom evolution. [ABSTRACT FROM AUTHOR]

Tsujimoto, G., Kakinoki, T., Hamaura Y., Shigematsu T. and Uno K., 2007. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 206 – 210. Gold Coast, Australia, ISSN 0749.0208 Sediment transport inside and outside a permeable submerged breakwater was examined in a laboratory experiment and a numerical calculation. The Macroscopic turbulence model, which has been applied for the thermal conduction in porous media, was used for the theoretical approach. A two- equation model for inside regions and 0- equation model was used for the outside region. Suspended sediment could be transported toward the onshore side due to two effects; vortex over sand ripples and the slope of a permeable breakwater. The amount of sediment deposited in the breakwater decreased gradually from the offshore to the onshore side during the experiment, while on the other hand decreasing rapidly in the numerical calculation. The surface profile over the submerged breakwaters could be reproduced excellently. [ABSTRACT FROM AUTHOR]