Archaeology of Australia’s coastline: The role of geomorphology in the visibility and preservation of archaeological deposits on sandy shores, with a Gippsland case study

Abstract In Australia as elsewhere in the world, coastal archaeological sites are increasingly threatened by rising seas and changing storm patterns, along with encroaching human activities. Understanding the geomorphological context is key to understanding the positioning of archaeological deposits in or on coastal landforms, their vulnerability to erosion and their resilience and capacity for longer-term management and preservation. Here we review the dynamics of beach-barrier systems to contextualise the potential of archaeological deposits to survive erosional processes, especially those associated with current and anticipated impacts of climate change. In doing so, we outline a practical logic for zoning coastal landforms and processes by their proclivity to either erode or preserve archaeological deposits, to assist in the planning of management agendas. It is the sediment budgets and how they change in relation to variation in sea level that fundamentally determine the potential preservation of archaeological deposits in coastal beach-barrier environments. We advocate close transdisciplinary collaboration between archaeology, geomorphology and site managers (i.e. Traditional Owners and land-and-sea management agencies) to better understand the wider landscape dynamics of coastal archaeological sites and landscapes.


Introduction
Across the world the coast is a critical zone of human habitation.Coastlines are dynamic interfaces between the land and the sea, where terrestrial processes interact with marine energy to create a wide range of landforms and ecosystems from estuaries to dunes and rocky cliffs (Davidson-Arnott 2010; Woodroffe 2003).For its inhabitants, this merging of terrestrial and seascapes is a space that brings a biologically diverse range of abundant resources, habitats, ecotones, and vistas within reach.Some have argued these merged land-and-seascapes make for enhanced demographic possibilities (e.g.Binford 2001;Codding and Jones 2013;Rick et al. 2020;Testart 1982;Thompson and Worth 2011).In Australia, today more than 85% of the current population lives within 50 km of the coast (Australian Bureau of Statistics 2020).The dense network of archaeological sites that ring the mainland, coupled with the high population densities estimated from ethnohistoric records (e.g.Williams et al. 2018), suggest that the current coast has supported some of Australia's densest human populations for hundreds or thousands of generations (e.g.O'Connor et al. 2017).Despite the thousands of sites listed in community, State and Territory registers, the physical traces of that lengthy history mark the ground with rich but currently largely undocumented cultural deposits (e.g.Rowland et al. 2014:38; see review in Cane 1997).Vertically, layer upon buried layer of archaeological sites are preserved in coastal beach-dunes, ridge plains and estuaries (e.g.Rowland et al. 2021).These exposed and buried landscapes are the ancestral presences of living Aboriginal and Torres Strait Islander communities; they are the 'history books' written on the Australian coastline.These sites are, however, under significant threat due to encroaching development and tourism, and by climate-change induced rising seas and changing storm patterns (e.g.Erlandson 2012;Rowland and Ulm 2012).
For GunaiKurnai Country in eastern Victoria (see below), by 2030, under the United Nations Intergovernmental Panel for Climate Change (IPCC)'s best-case scenario, 445 of the 547 (81%) known Aboriginal archaeological sites in Talli Kar Tor (meaning 'little flood', the GunaiKurnai name for the Gippsland Lakes coastal precinct) will be either destroyed or severely damaged by sea level rise, storm surges, and vegetation denudation (Birkett-Rees et al. 2023).The vulnerability of the coastal archaeological record in this region is further compounded by increasing human activity and infrastructure development.This means the Gippsland coast is likely to see further and possibly accelerated erosion of the region's coast and, by association, the permanent loss of First Nations' cultural (hi)story places.
In this context of cumulative and accelerating impacts on ancestral places, the GunaiKurnai Land and Waters Aboriginal Corporation (GKLaWAC), representing the Aboriginal Traditional Owners of much of Gippsland's coast (eastern Victoria), has initiated long-term scientific research of the coast across the length of Katungal (GunaiKurnai sea Country), with the management of sites and landscapes through the Katungal Indigenous Protected Area Sea Country Project.Underlying these concerns is an awareness that the 'archaeological' sites are inter-connected in multiple ways, so that their care requires a 'landscape' approach, as articulated in GKLaWAC's Whole-of-Country Plan.The Plan is based on nine fundamental Principles: 1. We have cultural obligations.It is our inherent responsibility to look after Countryto heal the damage of the past and protect it for future generations.2. Everything is connected.All of our Country is linked.There is no separation between our landscapes, waterways, coasts and oceans, and natural and cultural resources.All are linked and bound to our people, law and custom.This paper has grown from community-requested and community-led research that aims 'to understand what natural and cultural heritage exists out on Country', and to determine its management.It examines how an understanding of coastal geomorphology can help reveal archaeological site patterning and inform survey methodologies and site and landscape management.Our aim is to outline a practical logic by which to plan site surveys around the proclivity of different kinds of coastal landforms and processes to either erode or preserve archaeological deposits.But this simple distinction between erosional and preservational landforms is underlain by a more complex set of coastal processes that also need to be understood for the methodology to work.Guiding it all is the idea that the ability to understand and manage individual sites, and sets of sites, requires a consideration of their landforms in their broader and dynamic land-and-seascape context.As the elemental forces driving coastal landforms are global in nature, the principle developed here, focussed on Katungal (GunaiKurnai sea Country), is nationally and internationally applicable for sandy beach and dune systems similar to those found on Katungal.

Coastal geomorphology
The temporal co-evolution of landforms and human habitation raises the question of how geomorphology has influenced what people did where, and by association the nature of the archaeological record, and how it can be used to predict the future resilience of surface and buried cultural heritage along the coast, such as shell middens, stone artefact scatters and ancestral burials.A key to understanding the positioning of archaeological deposits in or on coastal landforms, their vulnerability to erosion and their resilience and capacity for longer-term preservation, lies in understanding their geomorphological contexts.In this paper, we review the dynamics of the coastal landforms of beach-barrier systems to contextualise geomorphic change in deposits that contain archaeological materials.We focus on the Talli Kar Tor/Gippsland Lakes region in Katungal, where the research is ongoing.While the archaeology has often supplied the 'dots on maps' and the stories that the individual sites and their distributions can reveal, it is the geomorphology that has shed most light on the deposits that contain the sites, and on the changing configuration of the land-and-seascape.
Along the coast, the development of geomorphic landforms (e.g.dunes, estuaries and coastal barriers) and the dynamics of their ecosystems are framed by environmental 'boundary conditions' (e.g.hydrodynamics, sediment supply, sea level change).In geomorphology, 'boundary conditions' are those landscape processes that occur outside the direct influence of the landform scale which is being investigated.They can include the regional wind and wave patterns, sediment supply from rivers, or even older landscapes that were active during different climatic periods.Anthropogenic forces can also be significant boundary conditions (e.g.Braje and Lauer 2020;Gibbard et al. 2022), which has significant influence on other elements of coastal systems, such as vegetation cover and associated aeolian sediment mobility (Gao et al. 2020;Jackson et al. 2019).
Here we differentiate between anthropogenic features and processes and anthropic ones: an 'anthropogenic' feature is one directly created by people, such as a stone tool.An 'anthropic' feature is something whose form or history was indirectly caused or influenced by human activities, despite not being directly created by people.For instance, wind-blown erosion of the sand creating a blowout in a dune might be considered 'natural' but may in fact have been initiated and thus in part created by people's behaviour, such as by the removal of nearby vegetation.In this paper, however, we mainly focus on environmental processes such as sea level rise, storm surges, wind and wave action, particularly the large-scale impacts of changing climate.This is perhaps best observed in the transition from glacial to interglacial periods, when sea levels rose at average rates of up to 15 mm/year in eastern Australia (Lewis et al. 2013;Thom and Roy 1985), with step-rises in excess of 45 mm/year over decades recorded for the Caribbean as a result of icesheet collapse (Harrison et al. 2019).
Landforms are created at nested (multiple articulating) scales (French and Burningham 2009;Kennedy et al. 2017).That is, processes that take place at very short, instantaneous timescales (e.g.individual waves breaking, single gusts of wind) drive sediment transport (Wright and Thom 1977), and averaged over centuries to millennia may lead to the creation of landforms.The longer-term trajectory of landform evolution in turn affects its resilience to shorter timescale environmental disturbances.For example, a landform that has a high sediment supply will be able to recover more quickly from an erosive event than one which has a net sediment deficit (i.e.where sediment supply is hindered or absent; see below for examples of sediment supply conditions) (Houser et al. 2015).On tectonically stable continental margins, such as in Australia, this scale-dependence means that extant coastal landforms have an evolutionary history that spans much or all of the Holocene, with many beach-barriers having boundary conditions related to deposition during the Last Interglacial (80,000-125,000 years ago) -e.g.eastern Victoria (Oliver et al. 2018), Bass Strait (Goodwin et al. 2023), South Australia (Belperio et al. 1995) and New South Wales (Thom et al. 1981) -or Penultimate Interglacial and older (>220,000 years ago), such as the Coorong Plain of southeastern South Australia and southwestern Victoria (Murray-Wallace et al. 2001) and probably Gippsland (Bird 1961;Jenkin 1968).
Human habitation of the Australian continent as documented by archaeology dates to around 65,000 years ago (e.g.Clarkson et al. 2017).During this period, the Australian climate has undergone radical shifts between cold glacials and the current warm interglacial of the Holocene.Sea level has risen by up to 130 m since the termination of the last glacial maximum at around 20,000 years ago, exposing a wide continental shelf that connected New Guinea and Tasmania to the Australian mainland through fluctuating land bridges (Murray-Wallace and Woodroffe 2014).The geomorphic responses to these eustatic (sea level) oscillations are significant (see below), and result from changes in sediment supply related to the rising and falling of the sea (Murray-Wallace and Woodroffe 2014).

Coastal barrier responses to sea levels
Coastal barriers are landforms found at the coast that are composed of sediments that are transported to the coast via fluvial processes, or created in situ by carbonate organisms within marine environments, and subsequently reworked back onto the coast by waves and tides and transported and stored onshore via aeolian processes to form coastal dunes.The typical landforms or landform elements that comprise a coastal barrier system are nearshore bars, beach face, berms, and foredunes and, where the shoreface is prograding, relic dunes which make up the barrier complex.They are characteristic of depositional environments along wave-dominated shores (Davis and Fitzgerald 2004;Davis and Hayes 1984;Woodroffe 2003).Coastal barriers include beaches and their associated landforms, spits and islands, for example, and can extend for many thousands of kilometres along the shore (e.g. the barrier islands of the eastern USA (Otvos and Carter 2008)) and create coastal plains tens of kilometres wide, such as at Moruya or in the Port Stephens-Myall Lakes region (Figure 1).In this paper we are mainly concerned with beachbarriers.A beach-barrier is often a large-scale (up to 1,000s of kilometres long) geomorphic unit that, while dynamic on a decadal scale, can commonly develop over many hundreds to thousands of years.As a result, the active surface of the beach-barrier extends from the seaward limit of sediment mobilisation by waves ('closure depth'), to the inland extent of aeolian or wave-tidal sediment transport (Otvos 1981(Otvos , 2012;;Roy et al. 1994).Beach-barriers can also exist as palaeo-landforms, either submerged beneath the current sea level or located inland from the current coastline.In Australia, the 90-Mile Beach-Talli Kar Tor/Gippsland Lakes system represents one of the nation's most extensive, dynamic, and geomorphically complex beach-barrier systems, being 150 km long, 30 km wide and enclosing the 354 km 2 of Talli Kar Tor/Gippsland Lakes (Bird 1961;Kennedy et al. 2020;  Oliver et al. 2018).The scale and variety of beach-barrier environments, proximity and diversity of marine and terrestrial habitats, makes them highly amenable to human settlement and therefore to the presence of often numerous or dense archaeological records.
As beach-barriers form over long timescales, they can be considered time-averaged depositional sequences with morphologies determined by the boundary conditions of sediment supply, sea level and storminess (Otvos 2012).Three broad types of beach-barriers are recognised: (1) prograding (also called 'regressive'); (2) stationary; and (3) transgressive (also called 'receding') (Roy et al. 1994) (Figures 1 and 2; Appendix 1).The landforms are generally classified on the basis of how the waterline at mean sea level behaves at a centennial scale.Where the shoreline moves seaward (i.e. the beach-barrier is building more land), it is classed as prograding.This occurs when the coast has a positive sediment budget.The shoreline can also move seaward when sea level is falling.This typically occurs when water is moved from the ocean to ice sheets during cold climatic phases, most notable during Ice Ages but may also take place in less pronounced ways during periods of lesser cooling.Such beach-barriers are also termed 'regressive', as they are associated with sea level regression.
Transgressive beach-barriers do the opposite; that is, the shoreline moves in a landward direction (Figure 2).This occurs when sea level is rising and progressively floods the coast as climate warms.The beach and dune sequences roll-over in a landward direction through processes of wave overwash (Kraft et al. 1987) (Figure 2).Effectively, under these circumstances, the landforms backstep (an intermittent process with gaps in deposition) or roll-over (continual movement) up the continental shelf as water depths increase.Beach-barriers can also move Figure 2. Schematic models of beach-barrier behaviour through time during (A) rising, and (B) stable sea levels under different time periods (t 0 , t 1 , t 2 ).(A) during a period of rising sea level, a beach-barrier moves landward as a transgressive system, as sand is reworked landward by wave overwash.(B) during a period of stable sea level where there is a high amount of sediment, the beach-barrier builds seaward (prograding), but as sediment supply wanes it can build vertically (stationary), or when in deficit the beach retreats (receding).MSL ¼ mean sea level (inspired by Roy et al. 1994).
landward during a period of stable (also called 'stillstand') sea level, which occurs when the supply of sediment to the landform decreases.In such instances, the landforms move landward to create a new profile in balance with the prevailing energy conditions.The classic evidence in the field of such behaviour is the exposure of older low-energy back-barrier sediments such as peat swamps on the beach-face, as previously overlying sediments are redeposited elsewhere by wave and/or wind (Figure 3).Understanding these conditions can be critical to assessing the potential antiquity of archaeological deposits during surveys or when planning excavations.
Onshore and offshore sediment movement during transgression is controlled by the slope of the continental shelf, especially in areas with low terrestrial sediment supply.Where the slope of the continental shelf is <1 � , a rising sea level causes the net direction of sediment movement to be landward.When the slope angle is steeper (>5 � ), sediment flux is offshore into deepwater.As a result, beach-barrier sequences on today's coasts are generally only found in areas with gently sloping continental shelves (Roy et al. 1994).This means that areas of shallow shelf slope contain more drowned barriers, and therefore have more sandy areas for people to exploit and inhabit.
In areas with moderately steeply sloping continental shelves (3-5 � ), the remnants of drowned beach-barriers may occur offshore, that is, seaward of the present-day coast, such as on the northern Gippsland Shelf in Victoria (Brooke et al. 2017) and Myall Lakes-Port Stephens in NSW (Thom et al. 1981(Thom et al. , 1992)).These drowned beach-barriers are often a source of sediment for landward transgressive sequences during periods of rising seas, and have been shown to be important conduits of sediment along the coast at Glacial-Interglacial timescales measured in the hundreds of thousands of years.An example is the Myall Lakes-Port Stephens region (Thom et al. 1981(Thom et al. , 1992)).Such drowned beach-barriers, preserved at depth below modern sea level, represent past shorelines from lower sea levels during periods of colder climate.
Under stable (stillstand) sea level conditions, sediment accumulation allows a beach-barrier to move seaward (Figure 1).On the Australian coast this was common during the Early to Mid-Holocene when the newly flooded continental shelf could supply sediment to the shoreline.This resulted in high rates of progradation of the coastal plains such as in the Moruya region of southern NSW between c. 7,000 and 4,000 cal BP, a process that slowed or ceased after c. 4,000 cal BP (Oliver et al. 2020) (Figure 1A); or the southern limit of 90-Mile Beach at McLoughlins Beach in Gippsland, which prograded over 1 km in 500 years from around 2,500 cal BP (Figure 4A).In some instances, progradation occurred relatively steadily throughout the Holocene (e.g.Callala Beach, southern NSW (Oliver and Woodroffe 2016)).Where additional sediments could be supplied to the coast, such as those that were washed down by river flows and floods, rates of coastal progradation increased in the Late Holocene, such as in the Shoalhaven region of NSW (Carvalho et al. 2019).As sediment supply wanes, or is not high enough in the first instance, a stationary beach-barrier can develop.These landforms are often dominated by vertical accretion and have complex internal structures as cycles of erosion and deposition occur at approximately the same location through time.Paradise Beach in Gippsland, Victoria is considered stationary (Thom 1984) (Figure 4B), as is Merimbula, NSW (Thom et al. 1978) (Figure 1B).At these locations, sediment supply is enough to create a subaerial (formed above the water line) beach once a rising sea level stabilised, but it is not high enough to allow for its seaward progradation.In areas where the sediment supply is low, the beachdune profile moves inland and the beach-barrier transgresses in the same way that it behaves during periods of sea level rise.
Outcrops of former back-barrier swamps on the open ocean beach-face are the most common evidence of a transgressive beach-barrier, such as found at Dee Why in Sydney (Thom 1984;Thom et al. 1969), Bulli in the Illawarra, NSW (Jones et al. 1979) and McGauran-Seaspray Beach in Gippsland (Figure 3, 4C).Transgressive beach-barriers can also occur in areas of higher sediment supply when the net direction of sediment movement is inland, rather than being deposited on the beach (Psuty 1988).This most often occurs in higher marine energy locations where extensive transgressive dunes occur behind the beach, such as in Discovery Bay, Victoria (Gao et al. 2022) (Figure 1C).
The behaviour of a beach-barrier both during sea level rise and subsequent stabilisation provides an important context for assessing the preservation potential of the archaeological record.As sea level has moved vertically by over 130 m during the past c.25,000 years, the shoreline has moved laterally by over 100 km in places such as Gippsland.This means that the archaeological evidence of settlement (e.g.middens, stone artefact scatters and burials) will be a function of where landforms can form and whether they can survive being drowned by sea level rise.

Preservation potential of the archaeology within surficial beach-barrier sediments
As coastal archaeology is created at or very near the land surface, knowledge of the geomorphology of its landscape is fundamental for understanding site preservation.The surface morphology of a modern beach-barrier is a direct function of the sediment budget of that particular section of the coast (Psuty 1988) (Figure 5).A positive sediment budget describes areas where sand accumulates, while a negative sediment budget generally indicates areas of erosion.
Two distinct sediment systems occur on a beachbarrier: (1) beach, and (2) dune.Wave and tidal processes determine sediment transport to and from the beach as well as along the shoreline (longshore), while aeolian (wind) processes move sand into dunes.The impact of each process is not confined entirely to each landform: waves can erode dunes and wind moves sand on the beach, but, as a whole, beach and dune landforms can be considered to be wave-and wind-dominated respectively (Davis and Fitzgerald 2004;Woodroffe 2003).Beaches will not build above the upper limit of waves, so where the sediment supply is greater than the amount eroded, the beach progrades seaward.Once a beach is wide enough such that its surface is able to dry between tidal cycles, wind is then able to transport sand inland and create dunes.A positive dune sediment budget leads to an increase in the size of the dune field, either vertically or through landward migration (Psuty 1988) (Figure 5).The preservation potential of the associated archaeology can then be related to the sediment budget (Figure 5).Where the budget is positive, the potential for site preservation is highest, as the area of land expands and the continued deposition of sand will protect sites through either direct burial, or by moving the shoreline seaward as the coast progrades and thereby reduces the ability of waves to impact a particular location.
The beach surface and dune geomorphology are directly related to the coastal sediment budget, and therefore the preservation of archaeological deposits in coastal landforms will also be linked to the sediment budget.This point is key to designing geomorphologically informed archaeological surveys and management plans that aim to: interpret past environmental processes accurately; infer future changes; McLoughlins Beach, the beach-barrier system was prograding during a 500-year period between 2,500 and 2,000 cal BP.This has resulted in the creation of sub-parallel dunes and troughs, here visible in the linear undulations under the vegetation (photo) and in the LiDAR image.(B) The beach-barrier at Golden Beach is stationary, having remained approximately in the same position for around 6,000 years.This has resulted in a higher sequence of dunes and more complex internal age structure.(C) The beach-barrier south of Seaspray is transgressive.Only a small foredune occurs, which is at most decades in age, and the coast is dominated by overwash deposits (oblique aerial images courtesy of Neville Rosengren).
and preserve cultural heritage sites and landscapes.In a simple model, it can be assumed that preservation will be highest where the sediment budget is positive, that is, where sediment deposition is occurring.The classic landform sequences that are formed in this situation are beach and foredune ridges (Figure 4A), the former being solely a beach deposit while the latter has a cap of aeolian sand.As it takes longer for a dune to form than a beach ridge (i.e. a ridge of wave-deposited sediment such as a berm), due to the time required to transport sand landward from the beach and form a dune, lines of beach ridges commonly occur in areas of faster rates of progradation (seaward movement of the land) than allow for the formation of foredune ridge plains.Such landscapes are characterised by a series of linear beach ridges aligned parallel to each other.
In areas where there is sediment deficit, sand is transported out of the system.On a beach, sand can be lost offshore/alongshore or landward into the dunes.In these circumstances, the shoreline retreats landward.Dune systems may also lose sand into the marine zone caused by coastal retreat, but they can also lose sand landward as wind blows material away from the coast.The geomorphic imprint of this reworking on a beach includes erosion scarps or washover deposits (Figure 6E,F), while for dunes wind-swept depressions and blowouts are found (Figure 6B,C).This reworking will disturb in situ archaeological remains, but not necessarily destroy them entirely as material may be reworked and redeposited elsewhere as deflated, lag (allochthonous) deposits.
Three geographical preservation zones can be inferred from these observations of coastal geomorphology.These zones can be mapped for their landforms, biogeography and extant geomorphological processes, and for the archaeological materials and sites they contain.This zonation may usefully be considered to determine what actions are required and at what stage they occur in the management of coastal cultural heritage sites and landscapes.

Zone 1: High preservation
The greatest degree of preservation occurs where the sediment supply to both the dune and beach components of the beach-barrier is high (Figures 5 and 7).The height of the foredune ridges in this setting is often inversely related to the rate of shoreline progradation.That is, slow seaward migration of the land has more time to transfer sediment from the beach into the dunes, and this therefore leads to the formation of higher foredunes (Hesp 1988(Hesp , 2002)).Therefore, fluctuations in depth-age curves of (archaeological) deposits can, at least in part, signal the changing distance between a ridge (e.g. a dune) and the low-tide mark over time-scales measured in years, decades and centuries.Any archaeological remains that are deposited in these areas of progradation are therefore not threatened by shoreline retreat or overwash, and will be able to be preserved through time.Where significant aeolian deposition can occur, there will also be enhanced preservation through burial.

Zone 2: Medium preservation
In areas where the coast is prograding quickly, there may not be enough time for dunes to form, or they may be small in height.The determinant is the amount of sediment available to the system.Sand dunes require the release of sediment to facilitate formation.In such situations, a series of beach ridges often develop, which are essentially waveformed features without the aeolian cap.The potential for preservation in such areas is not as high as before, as the protection that burial by aeolian deposition provides does not occur.Furthermore, as beach-ridge features (berms) are formed by waves, there is a higher potential for reworking of archaeological deposits as sites are under the influence of wave swash during their accumulation.These environments can also be less conducive for human settlement, as they do not have the shelter and the freshwater resources associated with dunes.These types of landforms are more common in areas of high coarse-sediment supply, such as along the South Island of New Zealand (Soons et al. 1997).
For beach-barriers where the beach is starting to erode and the shoreline moves inland (negative beach sediment budget) but the dunes are still accumulating sand, the potential for preservation of the archaeology is reduced.This reduction occurs through loss of land area as the coast retreats.In such settings, dunes can still accrete material as sediment is transferred inland, often through blowouts (Figure 8A,B), but the entire beach-barrier itself will be retreating as the shoreline transgresses inland.In the short term, this can temporarily increase the preservation of the archaeology immediately behind the coast as older surfaces are buried.This process is well observed along 90-Mile Beach, where recent ground-penetrating radar (GPR) and hand-auger surveys have indicated the presence of a widespread buried soil profile running along much of the current foredune.This soil profile is buried under several metres of aeolian sand dated to have been deposited within the past 150 years (Kennedy et al. 2020) (Figure 8C,D).The soil profile is exposed in blowouts in the foredune, where shell middens are now being eroded.These middens were preserved for over a century by rapid sand accumulation on the upper parts of dunes that formed on top of them, but are now being destroyed as sand moves further inland.For such beach-barrier settings preservation is initially high, but, over longer timescales, archaeological deposits are progressively lost through erosion.

Zone 3: Low preservation
In this zone, both the beach and the dune systems have negative sediment budgets.That is, sediment is being permanently lost (eroded away) through time.The surfaces of the landforms consist of actively transgressive sand sheets which continually rework material and transport it inland (Hesp 2013).For the beach, sand is either lost into these dunes or transported offshore by wind and/or wave action.The net effect is a surface environment that is continually being reworked (Hesp 2013(Hesp , 2000)).Reworking can cause a range of smaller, interlinked landforms to form.Blowouts in the foredune form when bare sand is exposed to wind, hollowing out delimited but growing areas as the wind is concentrated through their bowl-trough shapes (Hesp 2002;Nguyen et al. 2021) (Figures 6B and  8A,B).The troughs elongate downwind and, where there is enough sediment available, the front of the blowout moves inland, leading to the formation of parabolic dunes (Figure 6C).The dunes will often deflate to the elevation of the water-table, below which the wet sediments are unable to be transported by wind.Dunes that contained shells in their higher levels will often feature shell lag deposits on the exposed surfaces of the blowouts (potentially as palimpsests of material from different chronological contexts).This shell lag aids to protect the underlying sand from soil erosion (Figure 9).Such highly active systems often provide a variety of unique ecological niches with rich biomes, as well as access to groundwater that people can use.The potential for in situ archaeological The sediment budget of the beach and dune determines the landform types that will form.Where material accumulates on the beach (positive budget), the coast progrades (i.e. the beach widens seaward).Where beach sediments are eroding away (negative budget), the beach narrows.Dune growth can occur on both retreating (inlandmoving) and prograding (seaward-moving) coasts, and the foredune is most well-developed when the dune is accreting sediment (positive budget) and the beach is moving slightly more sand inland than it receives.(B) A conceptual model of the preservation potential of archaeological sites based on the coastal sediment budget.Preservation is highest when dunes are building (accreting upwards), and lowest when the coast is quickly receding (moving landward) such as during a sea level transgression.
materials to be preserved is low due to the constant reworking of sediments and high landscape mobility.In addition, the shorelines associated with such dune systems are also often transgressive, and therefore the landward migration of the high-water line would also rework any archaeological material into the littoral zone as the coast erodes away.

Human cultural factors
It is important to recognise that the creation of archaeological sites, while strongly affected by geomorphology, is not solely a product of the environment.People create and curate landscapes and utilise their environments for a variety of purposes, meaning that the absence of archaeological evidence does not necessarily indicate that people were absent, nor that an area was not culturally important.Instead, this could imply that people were not there for long enough to leave a permanent presence or were there in low numbers, or that the types of engagement did not involve the deposition of large amounts of cultural materials -the relationship between mobility levels, group size, the kinds of activities being undertaken and the material culture used and deposited (the 'artefacts' of archaeological sites) is complex.This is encapsulated, for example, in the idea of locations being used only temporarily or for very short periods, such as for seasonal or opportune (e.g.whale stranding) harvest, with materials being taken elsewhere for consumption or processing (e.g.Bird et al. 2002;McNiven 2000; Buried soil profiles that are now being re-exposed by dune blowouts.Luminescence dating and ground penetrating radar surveys (E) show that the burial has occurred over the past 150 years.In some cases (C), formerly buried middens are now being exposed and eroded (photos by David Kennedy).Meehan 1982).Absence of archaeological materials can also be a result of cultural preferences and protocols, whereby certain areas may be preferred or even reserved for specific activities as part of cultural practice (including avoidance as an active choice, and not to be confused with 'abandonment') (e.g.Barberena et al. 2017;David and Wilson 1999;Veth 2003).There may also be situations where archaeological sites become divorced from their original landscape context (e.g. through progradation), thereby altering the way that people view and interpret them as a part of a particular landscape.In such cases, individual sites or groups of sites may be preserved (e.g.shell mounds) while the landforms around them shift, such as embayments turning to wetlands and saltflats, so that the meanings attributed to the sites occur as part of altered cultural landscapes (Hiscock and Faulkner 2006;Meehan 1982:166-168;Stevenson et al. 2015).People give meaning to places, and their cultural preferences may influence the ways that people choose to use the landscape, such that a cultural sense of place produces the archaeological record before taphonomic or geomorphological processes become involved in its preservation, exposure, burial or reworking.Understanding archaeological sites and landscapes as cultural creations, as well as engaging with the environmental conditions and processes active in a landscape, gives researchers, managers and others the best opportunity to locate archaeological materials, interpret the roles of people in shaping the landscape (e.g.anthropic influences), and recognise the likely future conditions of these landscapes.

Conclusions
How can this geomorphological knowledge assist archaeological research and the management of artefacts, cultural sites and landscapes?The first key aspect to recognise is that landscapes are never static features, especially in high-energy environments such as the coast.They are constantly adjusting, albeit at rates that are highly variable, especially under changing climatic conditions.This dynamism is active today, and it was active when people inhabited coastal formations in past.It is therefore essential to recognise that the landscape-resource relationships observed today differed through time in the past (keeping in mind also that occupation and engagement of places was not just about resources).The (changing) patterns of occupation and their relationships to changing landform dynamics over time, and the fluctuating potential for archaeological sites to be preserved in such dynamic landscapes, are especially salient for Australia where human habitation has occurred over very long periods of time in which sea levels have vertically varied by some 130 m.
Second, understanding sediment dynamics provides a context by which to understand potential locations of past habitation.Areas where sediment is actively accumulating will lead to the archaeological record being preserved at depth through burial, but as the landscape grows under these accumulation conditions, activity can be dispersed over a wider spatial area.The geomorphic characteristics of each landform type thus provide mechanisms for exploring the archaeology.Beach-barriers dominated by overwash will be unlikely to preserve in situ remains, as observed during tropical cyclone events in North Queensland (Bird 1992) and Exmouth Gulf (Przywolnik 2002) for example, while those that are stationary will have a concentrated history of settlement preserved in the same area.The landforms themselves also provide different ecological niches as sources of food and water, raw materials, shelter and as access routes to connect with other areas and people.Complex systems with blowouts, deflation basins, lakes, high foredunes and the like would provide more varied and resource-rich environments for people than one composed simply of overwash sand sheets, but they may not be ideal as longer-distance travel routes.The kinds of archaeology one will find in different landforms cannot, therefore, be assumed but remain to be determined, as is the wont of archaeology.The variable chronostratigraphic integrity and potential of each landform needs to be assessed, and geomorphology has a key role to play in this because archaeological sites lie on or in landforms, each with its own dynamics, as argued in this paper.
The ever-moving nature of the landscape allows for more in-depth interpretation of the archaeology.Reworking of material is a very natural phenomenon, and recognition of this taphonomy is essential for reliably using the archaeology to tell (hi)stories about people and places in the past.Midden sites are an excellent example.Where they are made up of multiple events, they will often represent timeaveraged indicators of human occupation at a site.The exception are single-event sites, and multi-event sites with rapid sediment accumulation so that each event is separated by an intervening sediment horizon devoid of archaeological materials.The shells themselves are transported to a location by people, and are therefore allochthonous in nature having come from elsewhere, but the site provides an excellent timestamp of when that particular point of the landscape was exposed at the surface.This is especially the case for molluscs which would be consumed very soon after collection, so their time of death is well-constrained.Reworking of a midden site will destroy this site-specific timestamp, but the shells themselves remain as indicators of human presence in the landscape.While they may be reworked, often concentrated in lag deposits in dune blowouts, their presence still provides datable ages for when this part of the landscape was used in this way.
A major conclusion of this work is the need for close transdisciplinary collaboration between archaeology and geomorphology.Each landscape is unique -it operates in tandem with the local environment -the morphology of an individual dune can be understood by interactions between various boundary conditions, but the specifics of each archaeological site and its positioning requires detailed understanding of the local cultural setting.For too long the disciplines have largely operated independently or adjacently, despite some major close transdisciplinary collaborations over the past 50 years or more (e.g.Hughes and Lampert 1977;Robins et al. 2015;Sullivan et al. 2011) and the acknowledgement of the importance of geoarchaeology (Holdaway andFanning 2010, 2014).Archaeology is well aware of the greater spatial expanses that need to be understood, and yet research often remains very sitespecific; the individual sites are usually the focus of detailed investigation, in the process often missing the wider landscape dynamics.Geomorphology, on the other hand, has generally avoided archaeology, with it being viewed as contamination of the 'natural' processes (this is akin to the notion of the 'cultural filter' in Peacock et al. 2012).The planet is rich in peopled landforms and dynamics; not seeing the forest (landscape) for the trees (sites) leaves one and the other lacking.
two anonymous referees and the editors for useful comments.

Figure 1 .
Figure 1.The principal types of beach-barriers found on the present coast in Australia.Top-left: Regressive beach-barrier that progrades seaward, as observed at Moruya, NSW.Top-right: Stationary beach-barrier, as found at Merimbula, NSW.Bottomleft: Transgressive beach-barrier where sediment flow is inland, such as at Discovery Bay in Victoria (aerial image sourced from GoogleEarth).

Figure 3 .
Figure 3. Fine peaty muds developed in a former back-barrier lagoon, now exposed on the open-ocean beach-face at McGauran Beach, Katungal (photo courtesy of Neville Rosengren).

Figure 4 .
Figure 4. Examples of different beach-barrier types along the Talli Kar tor/Gippsland Lakes region in Katungal, with aerial photography and LiDAR images.(A) AtMcLoughlins Beach, the beach-barrier system was prograding during a 500-year period between 2,500 and 2,000 cal BP.This has resulted in the creation of sub-parallel dunes and troughs, here visible in the linear undulations under the vegetation (photo) and in the LiDAR image.(B) The beach-barrier at Golden Beach is stationary, having remained approximately in the same position for around 6,000 years.This has resulted in a higher sequence of dunes and more complex internal age structure.(C) The beach-barrier south of Seaspray is transgressive.Only a small foredune occurs, which is at most decades in age, and the coast is dominated by overwash deposits (oblique aerial images courtesy of Neville Rosengren).

Figure 5 .
Figure 5.A conceptual model for the preservation potential of the archaeology within coastal beach-barrier systems.The landforms in beach-barriers are a function of the dual sediment budgets of the beach and dune environments.Foredunes will reach their maximum size when the beach is transporting sediment inland but the coast itself is not receding (after Psuty and Silveira 2010).

Figure 6 .
Figure 6.Examples of classic surface landform features found on beach-barriers.(A) A large, narrow, single foredune near Seaspray, eastern Victoria.(B) Blowouts and troughs eroded into the foredune on Otago Peninsula, New Zealand.(C) Parabolic dunes extending inland from a foredune with extensive blowouts at Foxton, New Zealand.(D) The prograded foredune ridge system at McLoughlins Beach, eastern Victoria.The complete cover of vegetation masks the ridge morphology.(E) The landward edge of an overwash sequence, at the location of a former foredune after a category 5 hurricane along the Yucatan, Mexico.(F) The landward edge of the same overwash sand sheet (E) at the Yucatan, Mexico (photos by David Kennedy).

Figure 7 .
Figure 7. (A)The sediment budget of the beach and dune determines the landform types that will form.Where material accumulates on the beach (positive budget), the coast progrades (i.e. the beach widens seaward).Where beach sediments are eroding away (negative budget), the beach narrows.Dune growth can occur on both retreating (inlandmoving) and prograding (seaward-moving) coasts, and the foredune is most well-developed when the dune is accreting sediment (positive budget) and the beach is moving slightly more sand inland than it receives.(B) A conceptual model of the preservation potential of archaeological sites based on the coastal sediment budget.Preservation is highest when dunes are building (accreting upwards), and lowest when the coast is quickly receding (moving landward) such as during a sea level transgression.

Figure 8 .
Figure 8. Blowouts in the Gippsland region, Victoria.(A) Dune blowouts at Squeaky Beach, Wilsons Promontory, showing the incremental movement of sand from the foredune inland.(B) Vegetated saucer-shaped blowout at Reeves Beach (90-Mile Beach).The blowout has been stabilised by tea-tree over the past 100 years.People are standing in the Centre bowl.(C,D)Buried soil profiles that are now being re-exposed by dune blowouts.Luminescence dating and ground penetrating radar surveys (E) show that the burial has occurred over the past 150 years.In some cases (C), formerly buried middens are now being exposed and eroded (photos byDavid Kennedy).

Figure 9 .
Figure 9. Development of a blowout in a dune system(after Carter 1988).(A) An area of exposed sand is initially eroded and down-wears, with wind subsequently being concentrated in this area, leading to a positive-feedback and the blowout expanding.Sand is mobilised and transported downwind, causing the blowout to expand.Shells and associated midden deposits within the dunes are reworked and eventually form a lag deposit, after which aeolian transport ceases.(B) Small blowout and (C) large lag of mollusc shells, both in the Foxton dunes of the Manawatu region, southwest of the North Island, New Zealand (photos byDavid Kennedy).

have the right to be on our Country.
Our approach to managing Country is to balance resource use with conservation -they are all part of the same.
4. Don't wait until it has gone.When you lose a site, it's gone forever.We need to act now to prevent any further loss of environmental or cultural values.5. Look at what was there before.When we are healing and restoring degraded landscapes, we should try to put back the plants and animals that used to be there.6. Sustainable use.