River for Liveability – Promote, Protect and Preserve

Our waterways are under increasing pressure from climate change, pollution, recreational use, water abstraction and flow constraints, such as damming and channelisation. This years Stormwater Victoria 2019 State Conference is focusing on “River for Liveability – Promote, Protect and Preserve.

Celine Marchenay and Sarah Hollis will be presenting three projects at the conference that the Water Technology team and our clients have been working on.

Development of a city-wide Drainage Model to assess System Performance

Celine Marchenay, Warwick Bishop, Nigel Pugh (Melbourne Water)

Melbourne Water is currently developing system performance assessment tools for their water, sewer and drainage networks, to enable the completion of a system-wide assessment of performance and assist integrated water planning. With the existence of InfoWorks models for both the potable and sewer networks built and regularly calibrated over the last decade, Melbourne Water is aiming to fill in the gaps by developing a one-dimension (1D) drainage network model in InfoWorks ICM of the Melbourne metropolitan area and urban growth.

This project is the first step to building a living drainage network model to be updated, calibrated over time and used to assess the performance of the system under current and future scenarios. The first lot of priority catchments modelled and preliminarily assessed over a range of scenarios include the Patterson River, Elster Creek, Mordialloc Creek, Kananook Creek and the Mornington Peninsula. The 1D drainage model comprises all the Melbourne Water underground drainage infrastructure, some of the Council drainage trunk mains, open drains, natural waterways and retarding basins within the catchment extent. It was run for the 5-year ARI design events using the Australian Rainfall and Runoff 1987 including spatial variability in order to identify the deficiencies in the network which is supposed to be design for and carry the 5-year ARI design storm. The model was verified against the Melbourne Water 5-year ARI design flow values available from previous flood studies throughout the catchment. The existing conditions system performance was then assessed and presented in the form of thematic maps of pipe surcharges and maximum flow against pipe full capacity based on the Manning’s equation. The existing conditions system performance assessment revealed specific hotspots where the drainage network is surcharged, causing or not overland flooding (extent not assessed in this study) under the 5-year ARI. The 1D drainage model was assessed over a range of future scenarios including climate change and increase in population in line with the Victoria in Future 6 million (2031), 7 million (2041), 8 million (2051) and 10 million (2061) predictions to assess the needs for future infrastructure upgrade.

Monash National Employment and Innovation Cluster: IWM Precinct Scale Strategy

Sarah Hollis

The Monash National Employment Innovation Cluster (NEIC) is located 20km south east of Melbourne’s CBD and currently supports 85,000 jobs and generates $9.4 billion annually for the Victorian economy with the largest concentration of employment outside of the CBD. With the number of employees set to double over the next 35 years, a significant investment in infrastructure is required to support business development and ensure the precinct is an attractive place to work. As part of this investment, South East Water with support from Water Technology took the lead to identify precinct scale Integrated Water Management (IWM) strategies through engagement of key stakeholders including Yarra Valley Water, Melbourne Water, City of Monash, City of Kingston, City of Greater Dandenong, Monash University and the Victoria Planning Authority.

The engagement series included one-on-one stakeholder meetings, followed by workshops that were targeted at identifying:

• The current state and future pressures of the Monash NEIC;
• The progress towards a shared vision for the NEIC and identify institutional arrangements and barriers to achieving it; and
• Potential IWM projects and the prioritisation of these projects.

Within the workshop series, the overall stakeholder objectives were identified including Liveability, Landscape Health, Waterway Health, Flood Resilience and Diversification of Water Sources with Liveability proving to be the primary focus for all stakeholders. Through an appreciation of the Monash NEIC objectives, several opportunities were identified, primarily the reimaging of Mile Creek.

Mile Creek is currently an inaccessible, concrete-lined drain with poor aesthetic and environmental amenity. Three high-level conceptual designs were proposed with the preliminary performance of proposed scenarios assessed across a range of measures relative to each of the stakeholder defined objectives through the application of innovative tools developed by the CRC for Water Sensitive Cities. The reimagining of Mile Creek has the potential to not just provide significant positive impacts in terms of the identified Monash NEIC objectives but to also be transformative for the NEIC; it’s residents, employees and key stakeholders.

Banyule Swamp, my neighbour, will you give me a glass of water?

Cintia Dotto, Bertrand Salmi, Sarah Hollis, Sarah Gaskill (Melbourne Water), Sian Gleeson (Banyule City Council), Robert Powell (Banyule City Council)

The Banyule Billabong has been identified as one of the priority billabongs within the Yarra catchment currently suffering the impacts from flow regulation, urbanisation, and a changing climate. Previous studies concluded that the frequency and duration of inundation is insufficient to protect the billabong ecological health, prompting Melbourne Water and Banyule City Council to conduct a successful watering trial in 2016 with help from Victorian Environmental Water Holder. Water was pumped from the Yarra River into the billabong to protect its marsh and meadow zones.

Council and Melbourne Water are now looking to develop a long-term solution. Previous studies identified that excess water from Banyule Swamp -located north of the billabong -may be re-directed towards Banyule Billabong, to allow more frequent inundations of the billabong. The main concerns around this option are centred around the timing of the water delivery, potential impact on Banyule Swamp and quality of the water, which may be high in nutrients.

This study aims to understand possible interaction between existing water regime, water quality and vegetation in the Banyule Swamp to develop a long-term solution to both improve the ecological health of the Banyule Billabong and encourage wader habitat in Banyule Swamp, as Lathams Snipe visits the site. A monitoring program was thus initiated to gain an understanding of the water quality and level fluctuations in Banyule Swamp. Preliminary catchment analysis identified the main sources of water to the Swamp and bathymetric characteristics of the Swamp.

The results suggest that levels may fluctuate significantly during a prolonged drought period. This will need to be considered when considering Banyule Swamp as a potential source of water for Banyule Billabong. Hydraulic modelling was undertaken to identify key overland flow paths and estimate the trigger points above which Banyule Swamp received overland flows from adjacent creeks. This ultimately informed:

• the water balance analysis
• validated against data from the monitoring program
• used to understand the hydrological regime of Banyule Swamp and its suitability as a back-up source for Banyule Billabong.

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Floodplain Management Australia National Conference 2019

14-17th May 2019

The Annual Floodplain Management Australia Conference provides a great opportunity for practitioners and researchers to get together, learn from each other, share there experiences and understanding in an effort to “Make Australia Flood Safe”.

Many people around the world are working tirelessly to improve flood management and emergency response practices.  This FMA conference support this valuable ideal.

At Water Technology, we believe it is essential that flood management practices and decision-making continues to improve and that information needed for emergency response is available when it is needed. At this conference we will be supporting this knowledge sharing ideal with a workshop and two presentations.

• Our experienced floodplain management team will be presenting a workshop on “Modelling for Non-Modellers” with Danny Rose (FMA Technical Director and Manager Roads and Stormwater at Tweed Shire Council) prior to the conference.
• Lachlan Inglis will present “When Perception and Evidence-Based Practice Collide – Floodplain Management in the Aftermath of the 2016 Floods at St Marys, Tasmania”
• Ben Hughes is presenting “Communicating Planning Scheme Amendments in Victoria”

WORKSHOP: Modelling for Non-Modellers

Presenters: Steve Clark, Ben Hughes, Danny Rose (FMA and Tweed Shire Council) and Lachlan Inglis

Providing the basics necessary to understand the often complex world of flood modelling in order to better understand flood studies and reports, better manage consultants and prepare briefs, and understand the various technologies available. This workshop will focus on better understanding the “client side” of flood modelling, such as the activities of Council and Agency staff.

PRESENTATION:  When Perception and Evidence-Based Practice Collide – Floodplain Management in the Aftermath of the 2016 Floods at St Marys, Tasmania

Authors:Lachlan Inglis and Ben Tate

PRESENTATION: Communicating Planning Scheme Amendments in Victoria.

Authors: Ben Hughes, Ben Tate, Paul Fennell (Wimmera CMA) and Jack Brook (City of Ballarat)

Water Technology has completed dozens of flood mapping projects across Victoria. These studies initially determine flood risk, then attempt to reduce future flood risk by recommending changes to Council planning schemes to introduce or change overlays which control development. Generally, the planning scheme amendment is completed by a Council sometime after the flood mapping is complete, too often these amendments do not happen in a timely fashion or not at all. One of the primary reasons for this is the expected community opposition to Council attempting to regulate what individuals can and can’t do on their properties. It seems regardless of the population or level of change, community members will object, making the process unattractive to planners and Councillors. The additional complexity of communicating the changes in flood levels due to the new ARR2016 this process becomes more daunting and creates confusion with the public.

This paper focuses on Water Technology’s experience transferring flood intelligence data into planning scheme overlays and communicating how and why they were developed. It draws from numerous projects which through successes and failures, we have learnt what community consultation methods work in which circumstances and how the community perceive the consequences of the ARR2016 updates. We have represented Councils in a range of public forums including Planning Panel Hearings, Council Meetings, public meetings and one on one landholder discussions. The practical lessons learnt throughout this process allows for an ongoing improvement to how we as an industry communicate flood risk in a way which allows genuine understanding, less objections and a smoother planning process.

If you’d like to know more, get in touch with the presenters – call 03 8526 0800.

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In 2000, the Wodonga City Council and the North East Catchment Management Authority (CMA) jointly developed the Wodonga Waterway Action Plan (Thompson Berrill Landscape Design). This Plan is now out of date with many of its objectives met and new issues arising from a change in social, environmental and economic factors occurring across the project area in recent years.

One of the key pressures across the Wodonga City Council is the urban growth. The Wodonga Growth Strategy (Mesh Planning, 2016) states that the City has a current population of 39,644 and with consideration of the designated growth areas has a capacity to support an ultimate population of 100,000 people. To accommodate the growth, urban development has occurred and will continue to occur across the regional City into the future. Past urbanisation practices have contributed to several pressures and changes to the waterways across the Wodonga region.

There are many community groups across Wodonga City Council that are actively contributing to the management of the waterways in Wodonga.  The Wodonga Urban Landcare Network (WULN), a volunteer-based organisation, supports and facilities linkages between these community groups. As such WULN were tasked with the development of a new Wodonga Regional Water Action Plan with support from Wodonga City Council and North East CMA.

The Wodonga RWAP focuses on eight key waterways across the City of Wodonga. Each of the waterways have a unique range of values and threats.

Waterway Action Plan

What is a “Waterway Action Plan”?

The new Wodonga Regional Waterway Action Plan is aimed at developing sustainable rehabilitation and management strategies for the waterways across the region and is to account for the community and waterway values, aspirations and priorities as they relate to the waterways of Wodonga. Importantly, the implementation of the Regional Waterway Action Plan is to be managed by the Wodonga Urban Landcare Network and their sixteen community groups.

Traditionally, waterway action plans focus on one waterway system and are managed and implemented by a Catchment Management Authority. The Wodonga Regional Waterway Action Plan focuses on eight waterways and is to be managed and implemented by community groups. This provides a unique project management structure and target audience for a waterway action plan.

Development of the Regional Waterway Action Plan

Wodonga Urban Landcare Network (WULN) was tasked with leading the development of Wodonga RWAP. WULN is managed by a committee of volunteers from local community organisations. WULN have sixteen-member groups, largely consisting of Landcare and ‘Friends Of’ groups. A part time Facilitator is funded by the Victorian Government to provide support and co-ordinate training and other opportunities for the member groups. An additional part time co-ordinator was also funded to assist with the facilitation of the development of the Wodonga RWAP.

The Wodonga RWAP was developed in conjunction with North East CMA and Wodonga City Council. It is envisaged that North East CMA and Wodonga City Council will partner with WULN to deliver and fund projects developed from the RWAP. The input of the partner organisations for the project was managed through the establishment of a Project Control Group (PCG). The primary roles of the Project Control Group were to:

• Guide the preparation of the Regional Waterway Action Plan development.
• Disseminate information to their relevant stakeholder group/agency.

Since it is expected that the community will lead the implementation of the RWAP, it is critical to consult the community and broader partner agencies throughout the development of the RWAP. A Project Reference Group (PRG) was established to consult with key individuals and organisations that were deemed to have an interest in what is being proposed in the Wodonga RWAP by the Wodonga Urban Landcare Network. The PRG consisted of members from Landcare groups and ‘Friends Of’ Groups, individual landholders and land managers, property developers, DELWP and CFA. Through consultation with the PRG, it was highlighted that this plan was to be implemented by community members that have little to no experience with waterway management and are not professional waterway managers.

Since the RWAP is to be largely implemented by WULN and the community, the plan had to provide sufficient detail for the community members to co-ordinate and lead waterway rehabilitation works. Many community members are unfamiliar with the relevant partner organisations and the approval processes. As such, the plan needed to clearly define the roles and responsibilities of the relevant partner organisations and provide details of the approvals and permits required to undertake works on a waterway and on Crownland. The Plan also provides the community with standard works arrangements to assist them with applying for the required approvals and permits.

To develop the RWAP it was critical to gain an appreciation of the condition of the waterways within the project extent. It was not possible to assess all eight waterways in detail within the project scope. As such, site assessments were undertaken at targeted sites. The determination of field assessment locations was informed through:

• Review of background information including the Wodonga Regional Waterway Action Plan Community Consultation Findings Report. This report provided a summary of a comprehensive community consultation process that was undertaken as a preceding piece of work.
• Input from both the Project Control Group and Project Reference Group.
• Consultation with the broader community through the Wodonga Urban Landcare Network.

Through this process, a list of sites that were prioritised for assessment was compiled. Notably a large portion of the prioritised sites were concentrated in the urban section of the project area. This is primarily due to greater community interest in the urban areas where the waterways are easily accessed by the community and where the waterways are valued for their aesthetic and recreational attractions.

Additional localities were inspected across the project area to gain a broader understanding of the waterway/catchment condition. These sites were limited to where there was public access and visibility of the waterway network. This limited the additional site assessments largely to road crossing and parklands. Again, the majority of the sites were located in the urban areas.

The Wodonga RWAP has been prepared to empower the community to identify and implement individual waterway rehabilitation projects. This was done to so that the plan’s life wasn’t limited by a list of specific projects and to help build the communities involvement and ownership of projects. This has been achieved by providing a range of recommended projects and higher level, long term strategies. The recommended projects and strategies focus on work that Landcare groups and ‘Friends of’ groups can undertake, such as weed management, fencing and revegetation. However, it is acknowledged that some projects, such as large scale weed management or construction of grade control structures will require assistance from partner organisations that have the required expertise and experience.

To ensure the community led projects target the cause of an issue, rather than a symptom, it was essential to educate the community about the relevant catchment processes and influences. An example of the educational value of the RWAP is that there was a perception that stands of Phragmites were causing flooding and sedimentation in some of the urban reaches. In some locations the ‘Friends of’ groups would slash the Phragmites in an attempt to manage them. Through the development of the RWAP, the community were educated about the importance of Phragmites in waterways and that Phragmites are often incorrectly accused of causing flooding and sedimentation. However, it is more likely that flooding is exacerbated by downstream hydraulic controls such as bridges or culverts.  Likewise, bed and bank erosion in the upper and mid reaches is contributing to an oversupply of sediment into the lower urban reaches. It is the oversupply of sediment that is leading to the sedimentation rather than the presence of Phragmites. Phragmites will subsequently establish in the areas where deposition is occurring and hence they get blamed for the sedimentation.

By educating the community on catchment processes and influences, it allows the community to identify that they should be managing the cause of the issues rather than the symptom. In this example it is better to manage the sediment inputs in the upper and mid reaches to reduce the on-going sedimentation of the lower catchments, and that managing the Phragmites will likely be detrimental to the overall goal of improving the health of the waterways.

Opportunities and Limitations of a Community Implemented Waterway Action Plan

It is expected that WULN will lead the implementation of the plan with assistance from the partner organisations. Having a community group lead the implementation of the Plan can present great opportunities for the community and waterway health, but also present some challenges and limitations.  Some of the opportunities and limitations of the community led Waterway Action Plan are:

• Having a community group lead the implementation of the Plan will encourages community involvement and ownership of individual projects and the waterways on a whole. This will likely have great outcomes for waterway health and can also build a sense of community, purpose and self-worth for the individuals that are involved.
• Having the community lead waterway management projects will provide skill development and educational opportunities at various levels. The community will learn about waterway management and relationships between land management and waterway health. The volunteers leading the projects will develop project and people management, organisation and negotiation skills. There will also be significant opportunities to get local school, TAFE and university groups involved.
• WULN are a volunteer, non-for-profit organisation with limited funding. It could be considered unreasonable to hold WULN to account for overseeing the implementation of the Plan as it will rely on the good will of the WULN volunteers to continually seek funding and negotiate with Council and the CMA to undertake works. Should a few motivated community leaders cease to drive the implementation of the Plan, the implementation of the Plan may fail.
• The different partner organisations, including the individual Landcare and ‘Friends of’ groups and the general community, have a differing set of management priorities. Improving Wodonga’s waterways is a high priority for WULN and is a primary focus for many of the member groups. However, Wodonga Council and North East CMA have a broader list of responsibilities. It may be difficult for WULN to get Council and North East CMA to commit to specific projects considering these broader priorities.

The development of the Wodonga Regional Waterway Action Plan was a unique project. The development and implementation of the plan is to be led by a volunteer-based community group. The RWAP also covers eight key waterways. This meant that the plan had to be aimed at the general community rather than waterway management professionals. Therefore, the RWAP must arm the community with more than a list of recommended actions and strategies. The RWAP had to provide the community with an understanding of the how the catchment works in order for them to identify and prioritise suitable projects.  The WRAP also had to provide the community with details of partner organization they should be working with and the approval and permitting system they need to work through prior to starting a project. The management and implementation of a Waterway Action Plan led by a community group can present community building and educational opportunities but may lead to some challenges with the long term implementation of the plan.

To discuss this project, please contact Tom Atkin on 03 5721 2650.

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Water Sensitive Cities Conference: Valuing a water sensitive city – Economics Session

4th Water Sensitive Cities Conference 2019

Authors:

Craig Flavel (Water Technology), Andrew Telfer (Water Technology), Alison Charles (Water Technology), Michael Di Matteo (Water Technology), Sam Phillips (SA Dept for Environment and Water), Andy Chambers (Seed Consulting), Michele Akeroyd (Inside Infrastructure), Kanchana Karunaratna (Marsden Jacobs).

Presentation Summary:

Adelaide’s use of groundwater, treated effluent and treated stormwater from schemes using managed aquifer recharge (MAR) not only provides water at a price that stimulates the economy but also provides benefits such as increased water resilience and reduced coastal pollution.

By providing evidence of the true value of alternative water, this work can be used by a broad stakeholder group to inform business cases for the integration of alternative water schemes and encourage the use of alternative water resources to build sustainable cities and thriving communities.

Case Study:

Adelaide is the capital city of the driest state in the driest inhabited continent on Earth. The estimated market value of potable and alternative water on licence in the state of South Australia is over $2.8 billion. Alternative water in the study (Figure 1) now provides approximately 40% of Adelaide’s reticulated water use (Figure 2). Use of groundwater, treated effluent and treated stormwater from schemes using managed aquifer recharge (MAR) not only provides water at a price that stimulates the economy but also provides benefits such as increased water resilience and reduced coastal pollution. Due to variability in the value placed on these benefits by market stakeholders (Table 1), MAR is complex and strongly influenced by market externalities. These market stakeholders are diverse, including primary producers, sporting clubs, residents and councils. The regulation of the market is accordingly diverse; directly involving nine state government departments.

Within this context, the Adelaide and Mount Lofty Ranges NRM Board commissioned a study that derived estimates of the supply, demand, usage and quality of alternative water. The study methodology leveraged previous work, studying the land use in three zones in the study area and consulting with a wide range of stakeholders. Complex challenges of valuing water, water quality variability and a lack of monitoring data were addressed during the study by the project team. The project team mapped urban open spaces near alternative water pipelines, gathered operational data and identified trends and alternative water opportunities.

In the study area, alternative water usage was ~60,000 ML/a with 7% comprising MAR. Stormwater MAR supply was driven by a combination of market drivers and grant funding. The variable timing and distribution of grant funding can create uncertainty in the alternative water market. The impact of the different drivers of supply is evident in the pricing disparity between treated effluent and stormwater MAR. Excess demand for all alternative water was ~38,000 ML/a and excess supply (without upgrades) was ~54,000 ML/a. Peak demand did not coincide with peak supply, however, additional storage using MAR could reduce the excess supply.

Groundwater and treated effluent supply 93% of alternative water usage in the study area. Both of these sources are cheaper than stormwater MAR but for different reasons. Groundwater prices are driven by market forces under Water Allocation Plans. Treated effluent prices are subsidised by sewerage charges and driven by environmental protection legislation. Critical to integration of the market is coordination of diverse stakeholders. A coordinating body could set a framework that considers the true value of using alternative water, in addition to opportunities such as blending of water sources, decentralising MAR wells, water trading and expansion of treated effluent supply schemes to maximise the effectiveness of alternative water usage.

Increasing demand in future will likely be from conversion of perennial horticulture to high value seasonal horticulture, accessing excess demand from primary production outside the study area and meeting residential demand. Identifying these sectors is important as it drives where future investment may be cost effective.

By constructing 58 MAR schemes and 1,050 km of alternative water pipework for MAR and treated effluent in the study area, the region has demonstrated capacity to create and meet demand using alternative water. By providing evidence on the true value of alternative water, this work can be used by a broad stakeholder group to inform business cases for the integration of alternative water schemes and encourage use of alternative water resources.

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The causes of coastal erosion and options for managing eroding beaches.

At the upcoming Coastal Councils Conference, Coastal Challenges – Smarter Solutions, Dr Andrew McCowan will be presenting a discussion on coastal erosion, the causes and impacts, and coastal erosion management options.

Author:

Dr Andrew McCowan

Abstract:

With increasing population and more hot weather our beaches are increasingly in demand. In contrast to this, many of our beaches are actively eroding and require on-going maintenance. This presentation will discuss the main processes affecting our beaches: wind, waves, tides, currents and storms, and will explore some of the main causes of erosion. These causes will include: the effects of natural seasonal and inter-annual fluctuations, the effects of coastal structures and the effects of changes in coastal processes in adjacent beaches. They will also include the effects of Climate Change and Sea Level Rise and the impact that these will have in the future.

The presentation will then review the options available for managing eroding beaches. This will include both “soft” and “hard” management options. In this context, soft management options include non-structural measures such as dune management and beach nourishment, while hard management option include engineered solutions such as seawalls, groynes, artificial reefs and offshore breakwaters. These will be illustrated by examples where different management options have been used.

To discuss coastal erosion and the management options available, please contact Andrew or our Coasts and Environment team on 03 8526 0800.

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The Annual Coastal Councils Conference theme for 2019 is Coastal Challenges – Smarter Solutions.

Authors:

Astrid Stuer, Joanna Garcia-Webb and Elise Lawry

Abstract:

Australians place a high value on the coastline, which is used extensively for recreational and commercial purposes. Processes affecting the coastal zone are multiple and complex. The potential impacts of climate change will place increased pressure on the coastal zone and threaten public infrastructure and assets, private property, foreshore reserves and natural ecosystems.

Coastal adaptation planning is recognised as best practice to prepare for areas at risk of being affected by coastal hazards. Having a coastal foreshore reserve is considered the best practise in preparation for climate change as this allows for coastal processes to occur naturally without impacting on life and assets. However, most inhabited coastal areas are not protected by a natural buffer such as a reserve and coastal vulnerability assessments are recommended in order to prepare for climate change impacts on assets. Following this, a risk mitigation approach to planning identifies the hazards located within the council area, and prioritises adaptive measures.

This paper presents a review of the approaches to assessing coastal hazard vulnerability, risk identification and adaptive planning across Australia: in Western Australia, the process is Coastal Hazard Risk Management and Adaptation Planning (CHRMAP); Queensland applies the Coastal Hazard Adaptation Strategy (CHAS); South Australia follows the Climate Adaptation Planning Guidelines; Victoria the Victorian Coastal Hazards Guide provides the framework for coastal risk assessments, and in New South Wales it is the Coastal Management Plan. All of these are aimed to prepare coastal communities for climate change. During development of the plans, stakeholder communication with local communities is of utmost importance.

While all state programs are developed for a similar purpose, to plan and prepare for climate change through local government implementation, they also all have their differences which can lead to challenges. In some states, guidelines are not precise enough which results in varying methodologies applied over different councils. In these instances it would be more efficient to prepare stricter guidelines to enable uniform assessment across the whole state. At other times, gap analysis included in the very early phases of the program are not detailed enough, or gaps cannot realistically be filled in the available time, which results in difficulties and increased uncertainties in predicted hazards. In all states, funding of the mitigation strategies is a hot topic.

This paper explores the advantages and disadvantages of the different programs and what we can learn from each.

If you can’t make the conference and would like to know more about this presentation or climate change adaptation strategies, please contact Astrid on 07 3105 1460.

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Dude, Where’s My Yard? – A Forensic Assessment of Flood Model Results

Being able to undertake a detailed analysis of flood model results is an arrow in the quiver of every talented floodplain engineer. But how do you begin to analyse model results when you already know the answer? Following the 2011 flood event west of Brisbane, a series of waterway crossings were upgraded within the moderately large local catchment of an unnamed creek. In 2013, a rural property in close proximity to these upgraded crossings was devastated by flooding associated with ex-Tropical Cyclone Oswald. Although no significant property damage was incurred, a large portion of viable agricultural land was eroded. Given the close proximity of the property to the crossings, the landowner alleged that these works were responsible for a change in flood behaviour and, subsequently, resulted or at least contributed the erosion of a significant volume of land.

Prior to the 2011 flood event, the unnamed creek was traversed in numerous locations by small causeways. Although suitable in low flow conditions, these causeways proved problematic following minor and severe flood events with significant damage to several causeways occurring as a result of the 2011 flood event. Widespread improvement and modification of these structures was undertaken with a standard box culvert arrangement adopted at three crossings in the immediate vicinity of the property.

What does a ‘flood model’ have to do with it?

This paper provides insight into the forensic analyses undertaken within this specific reach of the unnamed creek. Of particular interest was the impact blockage of culverts had on flow behaviour and how altered flow paths resulted in a fundamental shift in flood behaviour during the 2013 flood event. Given that numerous iterations reflecting blockage did not readily result in a fundamental change in water level, an assessment of change in velocity and bed shear stress was undertaken. The findings of this assessment indicated that not only did blockage of the culverts result in a redirection of flows but the change in bed shear stress and velocity contributed to significant channel avulsion adjacent to the property and the damaged agricultural land.

Andrew Thompson will be presenting this paper on Thursday 7th March at IPWEA SWQ Branch Conference.

If you would like to know more about this presentation, please call Andrew on 07  3105 1460.

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An innovative risk-based approach for identifying potential water quality issues.

By T McAlister, M Stephens, D Middleton, M Bartkow, A Watkinson and J Lampard.

This stormwater harvesting paper was first published in the Australian Water Association Water e-Journal Vol 3 No 4 2018 and is now available online to download.

a key learning of those involved in this project is that a collaborative and consultative process between the project proponent and the ultimate authority responsible for potable water safety is essential if a scheme such as that proposed at Aura is to succeed.

Introduction

Stockland is one of Australia’s largest urban development companies, with a lengthy track record of delivering leading edge urban projects. Stockland is currently undertaking the Aura development on Queensland’s Sunshine Coast, a 50,000-person, 2200 ha master-planned community, which commenced construction early in 2015 and will be developed over the next 20 to 30 years.

A stormwater harvesting scheme is being investigated as a potential sustainability and water management component of Aura (McAlister et al 2017 and Figure 1). This scheme could potentially realise 2 GL/year of urban stormwater being harvested and used to augment the nearby Ewen Maddock Dam, owned and operated by Seqwater.

This paper describes an innovative and transparent risk-based approach that was developed to identify potential ecological and public health water quality issues associated with the scheme. The approach described was implemented for the first time in South East Queensland. The paper also presents previous and ongoing technical investigations conducted to inform the process, preliminary findings and lessons learnt.

Case study summary

The water quality characteristics of stormwater vary across urban catchments (Sidhu et al. 2012, Page et al. 2013, Reeve et al. 2015, Gernjak et al. 2017). The range and load of pollutants within stormwater from a specific catchment affect its suitability for use augmenting a drinking water supply source. Establishing the physico-chemical, chemical and microbial quality of stormwater is a critical step in determining the treatment and removal processes required to meet human and ecosystem health guidelines relevant to the drinking water supply source.

This study developed a clear and transparent framework to assess the entire suite of pollutants that may be present in stormwater for further consideration and evaluation. The framework uses a prioritisation and selection approach that gave consideration to land use, stormwater treatment, dilution and assimilation, and water treatment issues. Key actions associated with the case study were to apply the framework at Aura to guide ongoing risk assessments associated with the potential stormwater harvesting scheme.

Read the full paper in the AWA Water Source

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HydroNET and Deltares have signed an agreement to launch the WaterCONNECT initiative to provide an integrated, online solution to help improve water management decision-making.

Read the press release here.
Visit the WaterCONNECT website.

Delft-FEWS is an open platform that efficiently handles large amounts of big datasets and performs massive computations, while HydroNET applies data-mining algorithms and analytics to these datasets to create new information and knowledge. Water professionals and stakeholders can then use the easily accessible Delft-FEWS HydroNET Water Control Room to visualise online personalised dashboards and reports and make well-informed, accountable decisions.

Combination of HydroNET and Delft-FEWS

By connecting international knowledge and software to local data and information WaterCONNECT works with clients and local parties to co-create solutions to water problems. The well-established Delft-FEWS and HydroNET platforms form the backbone of these solutions. Delft-FEWS is an open platform that efficiently handles large amounts of big datasets and performs massive computations, while HydroNET applies data-mining algorithms and analytics to these datasets to create new information and knowledge. Water professionals and stakeholders can then use the easily accessible Delft-FEWS HydroNET Water Control Room to visualise online personalised dashboards and reports and make well-informed, accountable decisions.

Water Technology is the agent for HydroNET in Australia, contact Brian Jackson for more information on +61 3 8526 0800.

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The River Basin Management Society is holding its biannual Australian Stream Management Conference in Hobart on the 12-15th August 2018. This is a great opportunity for researchers, policy makers, consultants and practitioners to get together and share their experiences and investigations in the management of stream ecosystems and their catchments.

This is an important conference that Water Technology is proud to support. Water Technology staff from across Australia will be presenting:

• Hope for the best, plan for the worst: Managing sediment input in the upper catchment whilst preparing for avulsion at the mouth – Dr Michael Cheetham
• Development of the stream rehabilitation guidelines for Queensland – Luke McPhail
• Groundwater the known unknown in floodplain management – Andrew Telfer
• Werribee River Ecohydraulics – Parvin Zavarei
• When Perception and Evidence Based Practice Collide – Floodplain and Waterway Management in the aftermath of the 2016 Floods at St Marys, Tasmania – Julian Skipworth
• From planting willows to pulling them out: The past, present and future of riparian management in Victoria – Jo Slijkerman
• Wodonga regional waterway action plan: a community led waterway action plan – Tom Atkin

Abstracts for the Australian Stream Management Conference presentations are below.

Download the conference program here.

Australian Stream Management Conference Abstracts

Hope for the best, plan for the worst: Managing sediment input in the upper catchment whilst preparing for avulsion at the mouth

Michael Cheetham and Julian Martin

The George River in north east Tasmania runs from west of Pyengana to St Helens, where it flows out onto a large delta within Georges Bay. Previous research shows the delta, on which the township of St Helens it built, is Holocene in age. The George River and the Golden Fleece Rivulet to the south have both contributed to delta progradation during the Holocene and the George River has occupied several courses on the delta over that time. Currently, the George River occupies a course at the northern boundary of the delta; however, increased sediment accumulation in this section of the channel is causing rapid infill and avulsion to a new course on the floodplain is becoming imminent.

Sitting in a granitic catchment the George River is naturally subject to high sediment loads. However, historic hydraulic mining and land clearing have increased sediment loads substantially. The George River consists of alternating floodplain and gorge sections. As such, eroded sediment is forced rapidly through gorge sections and stored temporarily in the valley expansions, either as splays on the floodplain or sand slugs in the channel. Increased bank erosion due to a lack of vegetation or willow outflanking is leading to a substantially increased rate of sediment moving to the mouth, instead of being stored in these sections. Combined with substantial willow infestations in the lower reaches the river mouth is soon set to fill completely.

Management options to reduce sediment load include weed management, riparian revegetation and stock exclusion. However, the channel is very close to the threshold required for avulsion and the scale of bank stabilisation and revegetation required is vast. Whereas, managing sediment in the upper catchment is strongly recommended, preparing for avulsion at the mouth is essential to ensure a stable new course for the George River.

Development of the stream rehabilitation guidelines for Queensland

Luke McPhail, Michael Cheetham, Andrew Markham (Hydrobiology), Julian Martin, Andrew Brooks (Griffith University), Geoff Vietz (Streamology) Ben Pearson (Hydrobiology), Jim Tait (econcern) and Tim Pietsch (Griffith University)

The Queensland Department of Natural Resources, Mines and Energy is undertaking the production of the streambank, in-channel (instream) and riparian rehabilitation guidelines for Queensland (the Guidelines). The Guidelines, to be delivered in mid-2018, will provide users with a framework to understand the latest best practice rehabilitation principles; to evaluate intervention or monitoring approaches; and guide users to the appropriate sources of information to assess rehabilitation options based on their location within Queensland. The principles of streambank, riparian and in-channel rehabilitation and restoration, including stream classification, restoration objectives, management techniques, best management practice and demonstrable outcomes, and operational case studies are the foundation of the Guidelines. Regionally appropriate rehabilitation approaches will be identified to inform improved management practices relevant to the local context.

An extensive engagement program with a broad stakeholder group is key to the ultimate successful adoption of the guidelines. More specifically, a detailed engagement program with Natural Resource Management organisations, River Improvement Trusts and local government across Queensland is integral to this project. Stakeholder collaboration and consultation is to be used to evaluate and incorporate the hands-on practical knowledge, proven techniques, local context and experience that natural resource managers across Queensland can provide.

Groundwater the known unknown in floodplain management

Andrew Telfer, Alison Charles and Whendee Young (Department of Environment Water and Natural Resources (SA))

The Lower Murray Floodplain is generally a saline environment, both the groundwater and the unsaturated zone.  While native vegetation species are highly salt-tolerant, it is essential that sufficient, appropriate salinity, soil moisture is available to sustain growth and life cycle processes. Low salinity groundwater lenses (LSLs) provide an important source of water and support the ecological function of floodplains in an otherwise dry and saline environment. We advocate that the role of groundwater in sustaining floodplain vegetation needs to be more routinely considered in floodplain management.

In recent years, the behaviour of LSLs has become increasingly important in the management of Salt Interception Schemes (SISs).  It is important to understand the relationship between pumping volumes and lens development, as this will determine how quickly salt inflow returns to the River and influence floodplain vegetation condition. In addition, the SARFIIP program is developing floodplain infrastructure that will address the continuing decline in ecosystem health and deliver improved ecological outcomes for floodplains along the Lower River Murray.  Active management of groundwater to enhance ecological condition and manage risks associated with surface water inundation is an integral part of the program design.

The close relationship between groundwater and vegetation condition needs to be understood to make best use of environmental water.   There has been considerable investment in improving vegetation along the River Murray floodplain, and groundwater management may provide one of the most cost-effective interventions, especially where there is existing infrastructure. The learnings from the River Murray are likely to be applicable to other floodplains.

Werribee River Ecohydraulics

Parvin Zavarei

Agriculture is the dominant land use in the Werribee River catchment. Flow regime of the river has been dramatically altered to provide water for drinking and irrigation in this area, resulting in a significant depletion of flows in the lower reaches of the river in recent years. As a result of depleted flows and high levels of nutrients, this area is affected by large-scale accumulation of floating weeds and blue-green algal blooms.

Due to high nutrient levels, it is unrealistic to reduce weeds and algal blooms through water quality management. Therefore, the best approach is to prevent their build up by supplying a large enough flow. This study assessed the performance of a set of environmental flow releases as the mitigation measure for this ongoing issue.

A 3D hydrodynamic (HD) and advection-dispersion (AD) model of the lower Werribee river, was developed using MIKE by DHI 3D FM model. Hydraulic control points along the river were identified during a field survey. A series of ADCP velocity profiles were collected across the river by Water Technology during 2 environmental flow release events. Modelled velocities were successfully calibrated and verified against the velocity measurements. The AD model assessed the performance of the flow release for residence time improvement and the prevention of accumulation of blue-green algae blooms.

It was concluded that lower environmental flow releases in the range of 6 to 80 ML/d are not sufficient to achieve satisfactory flushing of the lower Werribee River.  An environmental flow of 100-200 ML/d performed best to mitigate algal bloom accumulation.

When Perception and Evidence Based Practice Collide – Floodplain and Waterway Management in the aftermath of the 2016 Floods at St Marys, Tasmania

Julian Skipworth

St Marys is a small town near the east coast of Tasmania which experienced three significant flood events in 2016. The largest event occurred in January 2016 and resulted in extensive damage including above floor flooding to numerous dwellings. The event has been estimated to be larger than a 0.5% AEP (1 in 200 year ARI) event and also resulted in significant changes to the waterway through the township.

The St Marys Flood Risk Management Study was commissioned six months ago by Break O’Day Council and has since been completed by Water Technology in partnership with Council, the community of St Marys and a number of other key stakeholders. The study commenced in late September 2017 against a backdrop of strong public perception around the cause of flooding at St Marys and how it should be managed. Through extensive consultation, engagement and education the community and study team have come to better understand why the town floods, and the sort of flood risk management options that could be implemented which won’t adversely impact the town’s greatest natural asset – the St Marys Rivulet.

The study has almost concluded and has been a great success with a number of actions identified to improve flood risk that have the strong support of the community. While improving waterway management was not an objective of the study the community has also come to better understand riverine processes in the rivulet and as a community have committed to working together to maintain and improve the ongoing health of the waterway.

From planting willows to pulling them out: The past, present and future of riparian management in Victoria

Peter Vollebergh (Department of Environment, Land, Water and Planning (VIC)), Jo Slijkerman

Riparian management in Victoria before the 1990s largely meant planting willows. Since then, particularly after the formation of catchment management authorities (CMAs) in 1997, the emphasis has been on using revegetation, weed management, fencing and off-stream stock watering to maintain or improve the condition of riparian areas. The program has resulted in several waterways being more than 80% fenced and protected.

Strong policy and funding have underpinned the Victorian Riparian Management Program. The Victorian Waterway Management Strategy (2013) and its predecessors provided policy and strategic direction for how riparian management was implemented – from the general framework such as how nine CMAs deliver the program by working with landholders in voluntary partnerships, to resolving operational issues and obstacles to the implementation of on-ground riparian work. Examples of the latter include the development of controlled grazing guidelines, information about fire on riparian land, and policy changes that make it easier for farmers who fence to get access to stock water. Improvements to the licensing of Victoria’s Crown water frontages have also been a key component of the program.

A dedicated plan – the Regional Riparian Action Plan – was released in 2015. It is a high priority for state government with over $40 million allocated to its implementation for five years. It outlines policies and actions for the future of riparian management in Victoria.

Although undertaken in Victoria, the lessons learnt from riparian management in the state are transferrable and far reaching, well-beyond jurisdictional boundaries.

Wodonga regional waterway action plan: a community led waterway action plan

Tom Atkin, Julian Martin, James Kaye

In 2000, the City of Wodonga and the North East CMA jointly developed the Wodonga Waterway Action Plan. The original plan is now out of date with many of its objectives met and new issues arising from a change in social, environmental and economic factors in recent years.

The Wodonga Urban Landcare Network (WULN) were tasked with the development of a new Wodonga Regional Water Action Plan with support of the City of Wodonga and North East CMA. The project area encompasses all the waterways across the City of Wodonga. Each of these waterways have a unique range of values including ecological values, passive recreation uses and aesthetic values and threats including urban encroachment, stock grazing, historic mining, channel instabilities and weed dominance.

The new Regional Waterway Action Plan aimed to develop sustainable restoration and management strategies for the waterways across the project region, accounting for the community and waterway values, aspirations and priorities as they relate to the waterways of Wodonga. Importantly, the implementation of the Regional Waterway Action Plan shall be managed by the Wodonga Urban Landcare Network who work with 14 different community groups, including regional Landcare groups, school groups, TAFE, Universities, Wodonga City Council, the North East CMA, individual landholders and other land managers.

This paper discusses the approach and key lessons learnt from the development of a community led strategic waterway action plan.

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