BMT WBM Pty. Ltd.

Melbourne, Australia

BMT WBM Pty. Ltd.

Melbourne, Australia
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Scott A.,National Marine Science Center | Scott A.,Southern Cross University of Australia | Malcolm H.A.,Solitary Islands Marine Park | Damiano C.,National Marine Science Center | And 2 more authors.
Marine and Freshwater Research | Year: 2011

Understanding the population dynamics of host sea anemones and their symbiotic anemonefish is important given that pressures such as aquarium collecting and bleaching events are adversely impacting their abundance in some IndoPacific locations. We examined long-term trends in anemone and anemonefish abundance at four sites within a 'no-take' zone at North Solitary Island, Australia, by comparing data from 2008 to surveys done in 1994 and 1995. Species richness was stable, comprising two anemones, Entacmaea quadricolor and Heteractis crispa, and three anemonefishes, Amphiprion akindynos, A. latezonatus, and A. melanopus. In 2008, densities of the most abundant species, E. quadricolor and A. akindynos, were substantially higher than previously recorded, with increases of up to 532% and 133%, respectively. There was a strong relationship between A. akindynos densities and anemone cover, whereas A. latezonatus had higher densities in deeper waters. Densities of this species remained similar over time, although there was a decline at one site. Heteractis crispa and A. melanopus were found in comparatively low numbers. Potential reasons for the overall increase in abundance include: protection from severe swell events, the lack of major bleaching events, the ability of E. quadricolor to reproduce rapidly by asexual reproduction, and the increasing duration of marine park protection. © CSIRO 2011.

Teakle I.,BMT WBM Pty Ltd | Andrews M.,BMT WBM Pty Ltd
Coasts and Ports 2013 | Year: 2013

In 2005 a shoaling indicator tool was developed by BMT WBM to assist the Department of Transport and Main Roads (TMR) in the management of periodic shoaling events in the entrance channel of Mooloolah River. The indicator was developed as a simple tool to alert TMR to the potential for a shoaling event and hence provide critical lead time for hydrographic surveys and dredge plant mobilisation to better manage the shoaling event. The tool utilises a detailed understanding of the sediment transport processes and the output of two directional wave buoy's (located offshore of Mooloolaba and near Moreton Island) to predict the onset and cessation of shoaling events. This paper describes the development of the indicator and presents its operational performance in the last 8 years. Overall the indicator has proven to be a valuable tool in the management of Mooloolaba Harbour entrance.

Sharma A.K.,CSIRO | Tjandraatmadja G.,CSIRO | Grant A.L.,BMT WBM Pty. Ltd. | Grant T.,RMIT University | Pamminger F.,Yarra Valley Water
Water Science and Technology | Year: 2010

The provision of water and wastewater services to peri-urban areas faces very different challenges to providing services to cities. Sustainable solutions for such areas are increasingly being sought, in order to solve the environmental and health risks posed by failing septic systems. These solutions should have the capability to reduce potable water demand, provide fit for purpose reuse options, and minimise impacts on the local and global environment. A methodology for the selection of sustainable sewerage servicing systems and technologies is presented in this paper. This paper describes the outcomes of applying this methodology to a case study in rural community near Melbourne, Australia, and describes the economic and environmental implications of various sewerage servicing options. Applying this methodology has found that it is possible to deliver environmental improvements at a lower community cost, by choosing servicing configurations not historically used by urban water utilities. The selected solution is currently being implemented, with the aim being to generate further transferable learnings for the water industry. © IWA Publishing 2010.

Lowry M.B.,Port Stephens Fisheries Institute | Glasby T.M.,Port Stephens Fisheries Institute | Boys C.A.,Port Stephens Fisheries Institute | Folpp H.,Indigenous | And 2 more authors.
Fisheries Management and Ecology | Year: 2014

Understanding succession of fish communities associated with artificial structures is required to assess the potential of these initiatives as part of fisheries enhancement strategies and determine possible impacts on the broader ecological community. Artificial reef systems constructed in three south-eastern Australian estuaries were monitored over a four-year period. Recruitment of fish to the artificial reefs was rapid, with significantly greater species richness observed on artificial reefs than on natural habitats for the majority of locations and times. The rate of community change varied between estuaries and appeared to be related to the quality and amount of existing habitat and the distance of the artificial reef from sources of recruitment. General patterns were also identified among estuaries driven by strong recruitment, followed by a rapid reduction in several mobile schooling species. By contrast, there was early and sustained recruitment of a variety of sparid species, which are of importance to recreational and commercial fisheries. © 2013 John Wiley & Sons Ltd.

Bruce L.C.,University of Western Australia | Cook P.L.M.,Monash University | Teakle I.,BMT WBM Pty Ltd | Hipsey M.R.,University of Western Australia
Hydrology and Earth System Sciences | Year: 2014

Oxygen depletion in coastal and estuarine waters has been increasing rapidly around the globe over the past several decades, leading to decline in water quality and ecological health. In this study we apply a numerical model to understand how salt wedge dynamics, changes in river flow and temperature together control oxygen depletion in a micro-tidal riverine estuary, the Yarra River estuary, Australia. Coupled physical-biogeochemical models have been previously applied to study how hydrodynamics impact upon seasonal hypoxia; however, their application to relatively shallow, narrow riverine estuaries with highly transient patterns of river inputs and sporadic periods of oxygen depletion has remained challenging, largely due to difficulty in accurately simulating salt wedge dynamics in morphologically complex areas. In this study we overcome this issue through application of a flexible mesh 3-D hydrodynamic-biogeochemical model in order to predict the extent of salt wedge intrusion and consequent patterns of oxygen depletion. The extent of the salt wedge responded quickly to the sporadic riverine flows, with the strength of stratification and vertical density gradients heavily influenced by morphological features corresponding to shallow points in regions of tight curvature ("horseshoe" bends). The spatiotemporal patterns of stratification led to the emergence of two "hot spots" of anoxia, the first downstream of a shallow region of tight curvature and the second downstream of a sill. Whilst these areas corresponded to regions of intense stratification, it was found that antecedent conditions related to the placement of the salt wedge played a major role in the recovery of anoxic regions following episodic high flow events. Furthermore, whilst a threshold salt wedge intrusion was a requirement for oxygen depletion, analysis of the results allowed us to quantify the effect of temperature in determining the overall severity and extent of hypoxia and anoxia. Climate warming scenarios highlighted that oxygen depletion is likely to be exacerbated through changes in flow regimes and warming temperatures; however, the increasing risk of hypoxia and anoxia can be mitigated through management of minimum flow allocations and targeted reductions in organic matter loading. A simple statistical model (R2 > 0.65) is suggested to relate riverine flow and temperature to the extent of estuary-wide anoxia. © 2014 Author(s).

Huxley C.,BMT WBM Pty Ltd | Beaman F.,Arup
ISHS 2014 - Hydraulic Structures and Society - Engineering Challenges and Extremes: Proceedings of the 5th IAHR International Symposium on Hydraulic Structures | Year: 2014

The Clarence River catchment, on the far north coast of New South Wales (NSW), is one of the largest catchments on the east coast of Australia, with an area of approximately 20,000km2. The lower Clarence River floodplain spans 500km2, within which lie the towns of Grafton and Maclean. These towns are home to over 20,000 residents collectively and serve as a rural centre for the surrounding agricultural lands. Both Grafton and Maclean are protected by levee systems which have been developed over time as a response to previous floods in the region. Roads and Maritime Services (RMS) is currently investigating options for an additional crossing of the Clarence River at Grafton to address short-term and long-term transport needs. All upgrade options for an additional crossing of the Clarence River will increase flood levels. RMS intends to maintain the current level of immunity and mitigate any adverse impact from piers and structures within the Clarence River by raising current levees. This paper draws upon and consolidates some of the findings from the options analysis to investigate considerations associated with spanning a 600m section of the Clarence River, mitigation of flood impacts, and modifications proposed to the existing levee systems.

Seelam J.K.,University of Queensland | Seelam J.K.,CSIR - Central Electrochemical Research Institute | Guard P.A.,BMT WBM Pty Ltd. | Baldock T.E.,University of Queensland
Coastal Engineering | Year: 2011

Direct measurements of bed shear stresses (using a shear cell apparatus) generated by non-breaking solitary waves are presented. The measurements were carried out over a smooth bed in laminar and transitional flow regimes (~104

Haines P.,BMT WBM Pty Ltd
Ecological Engineering | Year: 2013

Wetland restoration is becoming more common across the globe, encouraged by an increasing number of success stories, and facilitated by emerging environmental conservation and offset legislation. However, much care is still required as the 'art and science' of wetland restoration is considered to be rudimentary compared to the complexity of natural wetland environments (Zedler, 2001). Gaining a sound appreciation of wetland hydrology is fundamental to predicting future ecological function in response to wetland restoration projects (Callaway, 2001). In this regard, hydrodynamic numerical models can be used to predict hydrological behaviour and wetland inundation extents, providing that the models are an adequate representation of the real-world environment.Wetland restoration commenced at Hexham Swamp, Australia, in 2008. For the past 40 years this former estuarine wetland has been degraded by hydrological modifications resulting from the operation of one-way floodgates at its downstream end. The restoration project involves progressively opening the floodgates and allowing saline tidal waters to re-inundate the wetland flats, which have become dominated by a vast monoculture of Phragmites australis. A TUFLOW hydrodynamic model of Hexham Swamp was developed to identify areas within the wetland likely to be influenced by opening the floodgates. The model's predictive capacity was improved during the course of the project by the collection of high resolution ground elevation data and advancements in the numerical representation of the floodgates structure. Calibration of the numerical model was undertaken progressively as the restoration project advanced. One of the most critical parameters for matching observed data was the definition of the top-of-bank elevations along the wetland creekbanks. These elevations define the level at which water starts to overtop the banks and inundate the lower-lying wetland flats.The development of a predictive numerical model of Hexham Swamp wetland has been limited by the availability of accurate topographic data given the dense vegetation covering the majority of the model domain. This has necessitated a pragmatic and incremental approach to wetland restoration in order to manage risk and uncertainty. It is envisaged that topographic data collection will become easier over the next decade or so as the vegetation slowly transitions from its existing tall freshwater reeds to lower profile saltmarsh communities and open water ponds. © 2013 Elsevier B.V.

Naylor T.,CSIRO | Moglia M.,CSIRO | Grant A.L.,BMT WBM Pty Ltd | Sharma A.K.,CSIRO
Journal of Cleaner Production | Year: 2012

Empirical evidence on how to best operate and maintain greywater and stormwater systems is needed. Therefore, a survey was developed to explore operational and maintenance requirements of these systems. This paper reports on quantitative and qualitative methods used to determine attributes of "effective" greywater and stormwater systems in Australia, according to the management issue criteria used in the framework. Managers of stormwater and greywater systems were asked their opinion on the technical reliability, financial success, reduction in freshwater consumption and satisfaction of the end-user of the system. The data has then been analysed to determine which managing agency and predominant employee type manage to contribute significantly towards enhanced system performance according the prescribed criteria, while also accounting for the relative technical complexity of each system. © 2012 Elsevier Ltd. All rights reserved.

Andrews M.J.,BMT WBM Pty Ltd
Coasts and Ports 2013 | Year: 2013

The City of Darwin is responsible for managing coastal areas which include stable beaches, eroding soft cliff shorelines and shorelines behind mangrove forests. The core objective of this study was to develop a management plan which assessed the processes causing erosion, established an infrastructure risk priority ranking and then develop coastal engineering based recommendations for actions to prevent or minimise any erosion risk. The understanding of the interaction of the shoreline (geology, geomorphology) and oceanographic components (waves, tides) at the shoreline was the fundamental basis of understanding drivers and resistance to shoreline recession with each shoreline type resisting coastal stresses through different mechanisms. These mechanisms implied their relative susceptibility to future conditions, including severe storm events and/or projected sea level rise and therefore informed the assessment of mitigation options. A prioritised and costed list of erosion risk and mitigation actions was provided to Council for consideration.

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