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.
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. |
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.
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.
Naylor T.,CSIRO |
Moglia M.,CSIRO |
Grant A.L.,BMT WBM Pty. Ltd. |
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.