The Derwent Estuary – what do the people of Hobart really think of it?

Ursula Taylor1

1Manager, Partnerships & Governance, Derwent Estuary Program

Abstract

The Derwent Estuary flows through the heart of Hobart where 40% of Tasmania’s population resides. It has a reputation for two extremes: natural beauty and pollution. There is a great deal of scientific information about the Derwent because of high heavy metal levels due to past industrial practices, however, as the clean-up is well underway and continues, how does the community view and interact with the Derwent? Do they care? If not, why not? And for our organisation, have they heard of the Derwent Estuary Program and the messages we promote around beach water quality, seafood safety and walking track access? In comparing results from community surveys of Hobart residents in 2007 and 2013, changes in the community’s value of the Derwent were observed. There is greater use and enjoyment of the estuary as well as differences in concerns for its wellbeing. This repeated evaluation informs the communications of the Derwent Estuary Program – messages as well as communication avenues. Our aim is to increase awareness of the benefits of environmental management for the estuary, as well as for the people who live by it or visit it.

Biography

Ursula Taylor is a long-standing member of the Derwent Estuary Program and has been a coordinator, communicator and manager with the Program. She loves the Derwent estuary in Hobart and the people she works with to improve its health and keenly communicates the science and management of the estuary to the community, who use it for swimming, walking, boating and fishing.

Calculating sediment contributions from highly modified catchments to a tidal inlet – Broadwater, Gold Coast, Australia

Ms Jemma Purandare1, Dr Nick Cartwright2, Professor Rodger  Tomlinson1, Dr Mark Gibbs3

1Griffith Centre For Coastal Management, Griffith University, Southport, Australia, 2School of Engineering, Griffith University, Southport, Australia, 3Institute for Future Environments, Queensland University of Technology, Brisbane, Australia

Abstract

The Broadwater is a semi-enclosed tidal inlet located on the northern Gold Coast, Queensland, Australia. The Broadwater is connected to the Coral Sea by the Gold Coast Seaway – a constructed entrance originally the mouth of the Nerang River, and is fed by the Nerang, Coomera, Pimpama, and Albert-Logan River catchments. These catchments are highly modified with extensive urbanisation and constructed canal estates in the lower reaches of the Nerang and Coomera Rivers, water control from weirs and dams, including the Hinze Dam in the upper Nerang River catchment, agriculture, including grazing and cane farming, and dense urbanisation of the lower catchment around Southport and Labrador. The Broadwater itself is a highly modified coastal environment, with the fixing of the Nerang River entrance, construction of the Gold Coast Seaway and sand bypass system on the Southport Spit, and continuous dredging of navigational channels, all contributing to significant hydrological and sediment transport dynamics over the past 40 years. The urbanisation and intense modification of the catchments and surrounding coastal environment have impacted sediment dynamics, and while the Broadwater, particularly the Gold Coast Seaway and nearshore coastal environments, have been relatively extensively studied, analysis of literature indicates that the sediment dynamics and contribution from catchments is relatively poorly understood.

This paper details an investigation into the sediment contribution of the catchments to the Broadwater, with the aim of providing a quantitative assessment and analysis of catchment sediment dynamics. The paper provides a summary of the literature reviewed in determining the gap in knowledge, methodologies employed for gathering data and conducting analysis, summary of the data collected and quantitative statistical analysis and associated results, and a discussion and conclusions relating to the findings.

Biography

Jemma is a Coastal Scientist with more than 13 years’ experience in coastal and estuarine geomorphology, sedimentology, and restoration. She is currently halfway through her PhD research investigating the changes to sediment transport dynamics in a highly modified tidal inlet that is subject to a sand bypass pumping system. Jemma also works with Gold Coast City Council as the lead scientist on multiple estuarine monitoring projects, and is also the Queensland State Chair of the Australian Coastal Society.

Complexities of opening and closing the Gellibrand River estuary for water quality management

Ms Amanda Shipp1

1Alluvium, Cremorne, Australia

Abstract

Over 80% of Victoria’s estuaries periodically close to the sea. Closures are a natural process, however extensive flooding can occur when an estuary mouth is closed, impacting on public and private assets and productive use of the floodplain. As a result, estuaries are sometimes artificially opened with earth moving equipment. This process can lead to low dissolved oxygen conditions in the water column and fish deaths.

The Gellibrand River estuary has a complex history of management regarding the open / closed state of the estuary mouth. Periods of low dissolved oxygen (DO) concentrations historically occur during prolonged periods of estuary closure to the ocean, however also occur with artificial estuary opening. We completed an investigation using a data-driven approach to understand the factors influencing water quality conditions both in a closed estuary and immediately after artificial openings.

The investigation produced a framework to assess the likely impact on dissolved oxygen from keeping the estuary closed, vs the impact from artificially opening. Guidance on when to open was developed, which including limiting water extractions during key times . The project included a live trial of using the framework to inform management actions.  This approach could also be applied to other intermittently closed estuaries (ICE) to overcome artificial estuary opening and water quality management issues.

Biography

Amanda is an environmental engineer at Alluvium. Amanda specalises in fluvial and estuary processes and water resource investigations, and developing conceptual and technical solutions to complex problems.

Murder mysteries, life saving and the black ooze of the Merricks Creek estuary

Mr Ross  Hardie1

1Alluvium, Cremorne, Australia

Abstract

The Merricks Creek estuary was subject to a period of unpleasant hydrogen sulfide (rotten egg gas) odour, fish kills and decreasing aquatic recreation opportunities.  This study was undertaken to identify the processes that led to these issues, sorting through the history of the estuary and the diversity of opinions presented by an active and engaged community.

Through a series of investigations, including a review of an unsolved murder mystery, the hydrogen sulphide was found to be associated with the decomposition of organic matter in the presence of sea water, in a low oxygen environment, creating a black ooze. The dominant source of the organic matter, feeding the odour production, was identified to be sea grass brought into the estuary through tidal action.   However, the reason behind the sea grass accumulation in the estuary was more complex. The investigations revealed the Merricks Creek estuary to be on the margin of two estuary types i.e. wave dominated estuary and tide dominated estuary. Recent (2011/12) construction of a rock revetment wall to protect adjoining properties from estuary scour was identified to have shifted the estuary from a wave dominated estuary, to a tide dominated estuary, and as a consequence reduced the natural closure events at the estuary mouth, increasing the sea grass input to, and loading in, the estuary.

The paper explores these issues and the difficult decisions required to address the management of the Merricks Creek estuary.

Biography

Ross is a founding director of Alluvium and responsible for the assessment, design and review of waterway management programs and estuaries projects throughout Australia and South East Asia. Ross specialises in working with clients and stakeholders to develop agreed objectives, and understanding of the processes that impact on these objectives and the development of programs to achieve agreed water and waterway management outcomes.

Nuisance Inundation at Selected South East Australian Estuary Sites

Mr Dave Hanslow1

1Nsw Office Of Environment And Heritage, Dangar, Australia

Abstract

Global sea levels are rising and likely to have an increasing impact on coastal communities over the coming decades and centuries. NSW communities are known to be highly vulnerable to sea level rise with exposure greatest in low lying areas adjacent to estuaries. Increasing extent and frequency of inundation is likely to be one the more obvious impacts of sea level rise.

The potential impact of sea level rise on coastal infrastructure and communities is known to be partially dependent on the magnitude of current tide range and sea level extremes. The smaller the tide range and magnitude of extremes the greater the potential impact of sea level rise. In several places internationally, the impacts of sea level rise are already evident through increasing frequency of inundation of low-lying areas -so called ‘nuisance inundation’ or ‘sunny day flooding’.

In this study we examine the occurrence of tidal inundation at selected estuary sites in NSW. We combine observations of local inundation, high resolution digital elevation data with local tide gage data to identify thresholds for nuisance inundation at selected estuary sites. These thresholds are linked with the inundation of streets and foot paths. We explore changes in the frequency of inundation to date and examine the likely implications of relatively modest amounts of sea level rise on the frequency of inundation.

Biography

Dave is the senior team leader for the coastal and marine science team at the NSW office of Environment and Heritage

Working together to build an integrated forecasting system for the Patawalonga Lake

Mr Daniel Rodger1, Mr Lachlan  Attard1, Mr Craig Reardon2, Mr  Alex Cornish3

1Jeremy Benn Pacific, Spring Hill , Australia, 2Department of Environment, Water and Natural Resources , Adelaide, Australia, 3Bureau of Meteorology , Adelaide, Australia

Abstract

Australia is renowned for its coastal lifestyle – which is a source of both reputation and risk for communities living in low-lying areas.  The management of storm tides, coastal and fluvial flooding is an important element to these areas, particularly around coastal lakes.  The development of comprehensive forecasting systems offer an important non-structural mitigation approach to increase resilience in these areas.  Delivered through a multi-agency approach, they provide earlier warning of extreme events, allowing preventative actions, greater preparedness to emergency services, and faster recovery for communities.

The Patawalonga Lake, located south of Adelaide, is managed by the Department of Environment, Water and Natural Resources (DEWNR).  The lake has multiple uses, and during extreme weather it plays an important role in flood mitigation.  By manually opening the lake and altering its water level in the days before heavy rainfall and tides, it can be used as additional storage for flooding.  However, decisions need to be made in the days leading up to an event to offer the greatest benefits to residents.

A coastal and river forecasting system has been developed to support the lake operations, linking DEWNR operations to Bureau of Meteorology (BoM) forecasts.  It accounts for both coastal and fluvial processes, the upcoming astronomical tide, storm surge, rainfall, soil infiltration, runoff/routing to the lower system, and the complex hydraulic operations between the various outlets.  Each component has been linked within the Delft-FEWS forecasting ‘shell’ and a user-friendly website, and linked to BoM weather and tide predictions.

Biography

Dan is a Director at JBP for Coastal, Marine and Flood Risk Management, and a chartered civil and marine engineer.

Dan’s focus is the integration of innovation and technology within extreme weather management. He has lead the development of over 10 integrated coastal and flood forecasting systems, in Australia, Scotland, England and Wales.  In 2014 he developed the largest coastal comprehensive forecasting system in the UK, developed for the Moray Firth, and covering 400km of coastline, three councils, and 42 different communities.

Cleaning up an old port – what does success look like?

Mr Peter Pfennig1

1Environment Protection Authority SA, Adelaide, Australia

Abstract

After over a century of neglect and uninformed development and management the Port River near South Australia’s capital city Adelaide was looking very much the worst for wear. The river was characterised by an almost constant algal bloom with regular dinoflagellate population explosions causing ‘Red Tides’.  Stable rafts of sea lettuce (Ulva lactuca) were a regular feature of the nearby Barker Inlet and Adelaide’s coastal waters during spring. In the 1990s things began to change with discharges being either severely curtailed or removed and a continuing move to better stormwater management.  A Water Quality Improvement Plan was developed by 2008 with support from the Australian Government to set targets and guide efforts.

A Dolphin Sanctuary was established and more recently there has been a move away from heavy industry in the inner Port to commercial and residential development.

Things have changed in the Port River over the last 20 years, but how is it faring now, and what does the community think about their river?

Information about the current environmental status of the Port River will be presented and questions posed – when have we done enough? What will this look like? how will we use our Port river?

Biography

Peter Pfennig is a Principal Environment Protection Officer for the Environment Protection Authority of South Australia. Previous work includes the project management of Stage 2 of the Adelaide Coastal Waters Study and the development of the Port Waterways water quality improvement plan. Peter currently leads a team who develop water quality and other environmental management strategies in South Australia The team has a strong focus on engagement across the community. The team’s recent work includes water quality improvement plans for the Adelaide coast and the Mount Lofty Ranges watershed.

Exploring different approaches to estuary management in Australia and New Zealand

Ms Jaclyne Scally1

1RM Consulting Group, Torquay, Australia, 2Great Ocean Road Coast Committee, Torquay, Australia

Abstract

Estuaries around the world have long been places of strong social and economic interest. The flat, alluvial soils and ease of access has seen the establishment of agriculture, horticulture and industry on estuarine floodplains. The availability of resources, including fish, water and building materials such as sand and gravel has supported the development of settlements at estuaries; and historically they have been favoured sites for ports and protected harbours.

Over time, the use and development of estuarine environments has resulted in highly modified landscapes. Vegetation clearing, the introduction of weeds and pest animals, soil disturbance, the application of nutrients and changes in hydrology have directly altered the natural functioning of estuaries.

Estuary managers today are faced with a significant challenge to minimise further impact and restore and protect the ecological functioning of estuaries. This is no easy task given the highly dynamic nature of estuaries, the legacy of past actions, the looming threat of climate change, the large areas of privately owned land surrounding estuaries and the competing social, economic and environmental values.

Across Australia and New Zealand there are examples of NRM agencies working with industry and private landholders to enhance and conserve estuarine environments through a range of mechanisms. This presentation reports the main findings of a study tour undertaken during 2017-18 that explored estuary management approaches at catchments along the Great Barrier Reef, NSW and New Zealand.

Biography

Jaclyne is a Consultant with RMCG, based on Victoria’s surf coast. Her work has involved environment and sustainability planning for local government, estuary management planning, NRM program evaluations and community and stakeholder engagement. In 2017, Jaclyne received a Victorian Government grant to undertake a study tour looking at different approaches to estuary management, that seek to address the conflict between private landholders and the environment. This study tour forms the basis of her presentation.

Jaclyne is a board member of the Great Ocean Road Coast Committee and an active member of her local Coastcare group. In her spare time she can be found swimming, surfing or walking by the water.

About the Association

The Australian Coastal Society (ACS) was initiated at the Coast to Coast Conference in Tasmania in 2004. The idea was floated as a means for those interested in coastal matters to communicate between conferences and where possible take resolutions of the conference to appropriate levels of government.

The idea was discussed further at the Coast to Coast Conference in Melbourne in 2006 and it was agreed that Bruce Thom develop a constitution of a company limited by guarantee that would operate on a national basis.

This plan was accomplished and in 2008 at the Coast to Coast Conference in Darwin the constitution was ratified and an Executive appointed. The company received charitable status in 2011.

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