Stormwater Victoria 2019 State Conference
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
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.