Damara WA Pty Ltd

Innaloo, Australia

Damara WA Pty Ltd

Innaloo, Australia
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Eliot I.,Damara WA Pty Ltd | Gozzard B.,Geological Survey of Western Australia | Nutt C.,Department of Environment and Conservation Perth
20th Australasian Coastal and Ocean Engineering Conference 2011 and the 13th Australasian Port and Harbour Conference 2011, COASTS and PORTS 2011 | Year: 2011

Coastal compartments are features primarily related to the regional geologic framework and which exert structural control on the plan form of the coastline. In contrast to compartments, sediment cells commonly are smaller three-dimensional units. They are functionally defined by the movement of unconsolidated sediments between source areas and sinks within compartmental boundaries. Together, the compartments and cells provide a hierarchy of natural management units applicable to development of plans for sustainable use of natural marine resources, conservation of essential life habitats and sedimentary processes, vulnerability assessment and mitigation of environmental risks. Mapping of coastal landforms has been coupled with identification of physical compartments and sediment cells around the Western Australian coast to provide a land system hierarchy for marine and coastal planning and management. Limiting scales at each level in the hierarchy are linked to the detail of information required for the type of planning to be undertaken. At each scale key landforms are associated with metocean processes at a similar scale and linked to the major environmental risks for the compartment. In effect the hierarchy ranges from broad policy setting based on the structure and condition of the prevailing landforms to preparation of more detailed local plans associated with sites set on different landform components of coastal sediment cells within compartments.

Gallop S.L.,University of Western Australia | Bosserelle C.,University of Western Australia | Pattiaratchi C.B.,University of Western Australia | Eliot I.,Damara WA Pty Ltd.
Journal of Coastal Research | Year: 2011

Beaches associated with geological or engineered structures, recognised as perched beaches, are commonplace on many coastlines around the world and especially so in South West Western Australia (SWWA). Although it is accepted that hard coastal structures will affect beach behaviour, little is known about the mechanisms through which this occurs. The microtidal Perth coast in SWWA is influenced by one of the strongest and most persistent sea breeze cycles in the world. This, together with offshore limestone reefs attenuating swell means that locally generated sea breeze waves and currents dominate the hydrodynamics for half of the year. Field measurements were made of wave, current and beach morphology changes due to strong sea breeze forcing at the perched Yanchep Beach and Lagoon on the Perth Metropolitan coast. Spatial and temporal variation of waves and currents at the beach and in the lagoon were monitored throughout several sea breeze cycles and changes in beachface morphology surveyed at two beach profiles. A 50% reduction in sea breeze wind speed was found to weaken the lagoonal currents by 50% due to less wave overtopping of the limestone reef. Results show the influence of the limestone formations on waves and currents which affects the beachface response to sea breeze. Both beach profiles showed a clear cycle of erosion and accretion to sea breeze, with differences between the profiles even though they were spaced just 120 m apart. These results provide insights into the role of geological formations on the behaviour of a perched beach.

Gallop S.L.,University of Southampton | Gallop S.L.,University of Western Australia | Bosserelle C.,University of Western Australia | Eliot I.,Damara WA Pty Ltd | Pattiaratchi C.B.,University of Western Australia
Marine Geology | Year: 2013

The effect of coastal reefs on seasonal erosion and accretion was investigated on 2. km of sandy coast. The focus was on how reef topography drives alongshore variation in the mode and magnitude of seasonal beach erosion and accretion; and the effect of intra- and inter-annual variability in metocean conditions on seasonal sediment fluxes. This involved using monthly and 6-monthly surveys of the beach and coastal zone, and comparison with a range of metocean conditions including mean sea level, storm surges, wind, and wave power. Alongshore 'zones' were revealed with alternating modes of sediment transport in spring and summer compared to autumn and winter. Zone boundaries were determined by rock headlands and reefs interrupting littoral drift; the seasonal build up of sand over the reef in the south zone; and current jets generated by wave set-up over reefs. In spring and summer, constant sand resuspension and northerly littoral drift due to sea breezes allowed a sand ramp to form in the South Zone so that sand overtopped the reef to infill the lagoon. This blocked the main pathway for sand supply to downdrift zones which subsequently eroded. In autumn and winter, with the dominance of northwesterly storms and reversal in the direction of littoral drift, the South Zone eroded and sand travelled through the lagoon in the current jet to nourish the northern beaches. Inter-annual and seasonal variation in sea level, storm frequency and intensity, together with pulsational effects of local sand fluxes at Yanchep due to inter-seasonal switching in the direction of littoral drift determined marked differences in the volumes of seasonal sand transport. These seasonal 'sediment zones' highlighted interesting and unexplored parallels between coasts fronted seaward by coral reefs and rock formations. © 2013 Elsevier B.V.

Gallop S.L.,University of Western Australia | Bosserelle C.,University of Western Australia | Pattiaratchi C.,University of Western Australia | Eliot I.,Damara WA Pty Ltd
Marine Geology | Year: 2011

We hypothesized that beach profiles that are perched on natural rock structures would be better protected from waves and currents than profiles that are not fronted by rock. In southwest Western Australia many beaches, such as at Yanchep, are perched on Quaternary limestone. Yanchep Lagoon is fronted by a low-crested limestone reef that partially encloses a coastal lagoon. The spatial variation of waves and currents around the rock structures were quantified during the sea breeze cycle at locations: (1) offshore; (2) 20 m seaward of the reef; (3) inside the lagoon; and (4) in the surf zone. The spatial variation in the beach profile response was measured at two beach profiles: (1) the Exposed Profile that was not fronted directly seaward by outcropping limestone; and (2) the Sheltered Profile which was fronted seaward by submerged limestone at 2. m water depth and that was near the lagoon exit at the end of the limestone reef. The Sheltered Profile had greater volume changes during the cycle of the sea breeze whilst the Exposed Profile recovered more by overnight accretion when wind decreased. The lagoonal current drove the strong response of the Sheltered Profile and may have contributed to the lack of overnight recovery of the beach together with the seaward rock formation impeding onshore sediment transport. The different direction and speed responses of bottom-currents in the surf zone fronting the two profiles reflected the local variation in geology, the influence of the jet exiting the lagoon, and wave refraction around the reef that was measured with GPS drifters and wave-ray tracing using XBeach. Major spatial variation in waves, currents and beachface behavior at this perched beach shows the importance of the local geological setting. © 2011 Elsevier B.V.

Gallop S.L.,University of Western Australia | Bosserelle C.,University of Western Australia | Eliot I.,Damara WA Pty Ltd | Pattiaratchi C.B.,University of Western Australia
Continental Shelf Research | Year: 2012

Mechanisms through which naturally-occurring hard landforms, such as rock and coral reefs, influence coastal sediment transport are still poorly understood. Therefore, field investigations were undertaken during storm conditions on the sandy beaches of Yanchep Lagoon in southwestern Australia, which are perched on Quaternary limestone reefs. During two consecutive winter storms, the response of three subaerial beach profiles were quantified at: (a) an Exposed Profile which was fronted to seaward by a predominantly sandy substrate; (b) a Reef Profile that was fronted directly seaward by limestone outcrops submerged below mean sea level; and (c) a Bluff Profile where the dry beach was perched on a limestone bluff that reached above mean sea level and that contained a shallow coastal lagoon. The subaerial beach response to the storms had considerable spatial variation alongshore and was strongly dependent on the local rock topography. The Exposed Profile eroded most with a 2. m-high scarp cut into the dune while the dunes at the Reef and Bluff Profiles were stable. The Bluff Profile also eroded considerably and the coastal lagoon widened and deepened. The Reef Profile was the most stable overall because erosion was balanced by short periods of accretion during the storm period which was partly due to sediment supplied by longshore transport through the coastal lagoon from the Bluff Profile. During the month after the storms wave energy was relatively low and the beach at the Exposed Profile accreted almost to the pre-storm volume, although the scarp in the dune was still present. The Reef Profile accreted most in the month after the storms while recovery at the Bluff Profile was low. It appeared that the bluff inhibited onshore sediment transport during and after the storms and in addition, strong currents in the lagoon transported sediment alongshore to supply the other beach profiles. These observations indicated that rock topography, especially elevation relative to sea level determined if beach erosion was reduced during storms and whether accretion was dampened in the post-storm recovery phase. © 2012 Elsevier Ltd.

Eliot M.,Damara WA Pty Ltd. | Travers A.,Coastal Zone Management Pty Ltd.
20th Australasian Coastal and Ocean Engineering Conference 2011 and the 13th Australasian Port and Harbour Conference 2011, COASTS and PORTS 2011 | Year: 2011

Investigation of historic beach and dune field evolution was undertaken, to develop a probabilistic model of future shoreline change, to be used for coastal vulnerability assessment of foreshore infrastructure at Scarborough Beach. The analysis compared long-term records with previous studies of beach width, to describe relationships with key climate variables. A major finding of the investigations was the significant role of annual alongshore wind anomalies in beach growth or recession.

Eliot M.,Damara WA Pty Ltd | Stul T.,Damara WA Pty Ltd | Eliot I.,Damara WA Pty Ltd
Coasts and Ports 2013 | Year: 2013

Landform analysis provides an opportunity to more effectively use the broad array of available coastal modelling techniques. In the absence of dedicated monitoring programs, limited validation commonly leads to adoption of generic modelling systems and a 'one-size-fits-all' approach. The implication of a one-size-fitsall approach to coastal process assessment is strongly challenged in areas of complex geomorphology, or in locations with discrete changes, such as a headland controlled coast. The effect is to develop a systematic dislocation between model representation and reality, according to how well the model captures processes. In the absence of more detailed information, landform analysis may provide a proxy indication of active coastal processes. Consideration of landform scales is intrinsic to this approach, enabling evaluation of landform relationships and potentially clearer focus on processes otherwise obscured due to observational scale. In particular, landform analysis indicates longer-term coastal response to changes in climate, including sea level fluctuations. It also may be used to assist coastal management by providing a simple indication of where coastal land may be unstable and what coastal sensitivities may need to be considered. This paper revisits the importance and use of landforms within coastal engineering in the context of increased use of numerical models. The concepts are supported by examples for sections of the Western Australian coast from Geographe Bay to Port Hedland in the Pilbara, encapsulating a range of morphologies. It is argued that use of landforms to guide the use of numerical models will improve model performance.

Stul T.,Damara WA Pty Ltd. | Eliot M.,Damara WA Pty Ltd. | Bailey J.,BMT JFA Consultants Pty Ltd. | Marshman S.,BMT Oceanica Pty Ltd. | Hill A.,Range to Reef Environmental
Australian Coasts and Ports 2015 Conference | Year: 2015

This study presents a method for assessing the feasibility of using dredged or hauled sand as a renourishment source for estuarine beaches. Three protocols improve the ease of decision-making when considering renourishment, dredging viability and cost-comparison of dredging against hauled sand. The protocols determine: (1) if renourishment is required at a target site; (2) potential sources of renourishment material and their constraints; and (3) life-cycle costs, allowing comparison with alternate management options. Components of each of these protocols were condensed into a field sheet to facilitate an initial 'Go- No Go' assessment. This produces one of four outcomes: do not renourish; consider hauled sand; consider land-based excavation; or consider floating dredge. Short-listed options may then be subject to a cost comparison over the life-cycle based on cost estimates for all project stages.

French J.,University College London | Payo A.,University of Oxford | Murray B.,Duke University | Orford J.,Queen's University of Belfast | And 2 more authors.
Geomorphology | Year: 2016

Coastal and estuarine landforms provide a physical template that not only accommodates diverse ecosystem functions and human activities, but also mediates flood and erosion risks that are expected to increase with climate change. In this paper, we explore some of the issues associated with the conceptualisation and modelling of coastal morphological change at time and space scales relevant to managers and policy makers. Firstly, we revisit the question of how to define the most appropriate scales at which to seek quantitative predictions of landform change within an age defined by human interference with natural sediment systems and by the prospect of significant changes in climate and ocean forcing. Secondly, we consider the theoretical bases and conceptual frameworks for determining which processes are most important at a given scale of interest and the related problem of how to translate this understanding into models that are computationally feasible, retain a sound physical basis and demonstrate useful predictive skill. In particular, we explore the limitations of a primary scale approach and the extent to which these can be resolved with reference to the concept of the coastal tract and application of systems theory. Thirdly, we consider the importance of different styles of landform change and the need to resolve not only incremental evolution of morphology but also changes in the qualitative dynamics of a system and/or its gross morphological configuration. The extreme complexity and spatially distributed nature of landform systems means that quantitative prediction of future changes must necessarily be approached through mechanistic modelling of some form or another. Geomorphology has increasingly embraced so-called 'reduced complexity' models as a means of moving from an essentially reductionist focus on the mechanics of sediment transport towards a more synthesist view of landform evolution. However, there is little consensus on exactly what constitutes a reduced complexity model and the term itself is both misleading and, arguably, unhelpful. Accordingly, we synthesise a set of requirements for what might be termed 'appropriate complexity modelling' of quantitative coastal morphological change at scales commensurate with contemporary management and policy-making requirements: 1) The system being studied must be bounded with reference to the time and space scales at which behaviours of interest emerge and/or scientific or management problems arise; 2) model complexity and comprehensiveness must be appropriate to the problem at hand; 3) modellers should seek a priori insights into what kind of behaviours are likely to be evident at the scale of interest and the extent to which the behavioural validity of a model may be constrained by its underlying assumptions and its comprehensiveness; 4) informed by qualitative insights into likely dynamic behaviour, models should then be formulated with a view to resolving critical state changes; and 5) meso-scale modelling of coastal morphological change should reflect critically on the role of modelling and its relation to the observable world. © 2015 Published by Elsevier B.V.

Eliot M.,Damara WA Pty Ltd | Eliot M.,University of Western Australia | Eliot I.,University of Western Australia
Hydrobiologia | Year: 2013

Geomorphic research across the semi-arid and wet-dry tropics of northern Australia has highlighted the role of the regions' estuaries as a "canary in the coalmine" for climate variations, with dramatic structural shifts over the Holocene. This behaviour highlights the region's potential sensitivity to climate change and suggests the need for careful identification and interpretation of dynamics in the tropical and subtropical regions. However, analysis of change in these regions requires care, as a number of the basic tools applied to interpreting estuarine change in temperate regions are obscured, invalid or simply unavailable when applied in lower latitudes. This study provides a synthesis from a range of investigations across northern Australia and identifies characteristics to be considered when interpreting or predicting submillennial estuarine change in these regions. © Springer Science+Business Media B.V. 2012.

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