45 Shand Road, Reservoir

Insight:

This infill development uses rainwater harvesting and raingardens to meet council flood mitigation requirements, rather than dedicated on-site ‘grey infrastructure’ like concrete pits, tanks and pipes. The project also involved a new method of assessing flood water mitigation that proves these water sensitive solutions are a viable alternative to conventional infrastructure.

The drivers

The developer, Ys Housing, is a not-for-profit organisation that aims to deliver 1,000 new, affordable homes over 10 years to combat inequality and shape a fairer, more vibrant city.

For Shand, Ys Housing set out to make sustainability more accessible and affordable. In particular, Ys Housing aimed to:

demonstrate net-zero, water sensitive, affordable housing that is repeatable at a suburban scale
reduce cost by replacing conventional underground concrete stormwater detention systems, with water sensitive alternatives
meet stormwater flow volume reductions to protect waterways, as set out in EPA Victoria’s Urban Stormwater Guidance and to comply with the obligations of the General Environmental Duty in the Environment Protection Act 2017
meet the Australian Rainfall and Runoff 2019 guideline (AR&R) for the design and modelling of flood mitigation responses
collaborate with the City of Darebin on WSUD innovation.

The innovations

This case study uses WSUD to meet council flood mitigation requirements, rather than dedicated on-site ‘grey infrastructure’ like concrete pits, tanks and pipes.

In particular, the WSUD scheme at Shand introduced the following features:

Household collection and reuse of rainwater – Each townhouse will be equipped with a 3000 L rainwater tank that has 2000 L for reuse and approximately 1000 L for stormwater detention. Harvested rainwater will be connected for flushing and external taps for gardens.
Integrated swale and raingarden – The site will include a vegetated swale running the length of the driveway and a ~8 m² raingarden that runs along the front boundary, designed to support tree growth in the front set back.
High surface permeability – The development will have ~200 m² (30%) of pervious surfaces made up of gardens, permeable paving and decking.
Plant selection – The gardens will use native species that are local to the Victorian volcanic plains. The use of bird-attracting trees, wildflowers and scented shrubs will provide shade and encourage biodiversity, while also requiring little active irrigation because they are well adapted to the Victorian climate.

As well as using WSUD in this way, this case study also relied on a new method of assessing the flood mitigation of WSUD assets. This is a fundamental shift from the existing STORM design method. To achieve this, a new method was developed to assess on-site detention outcomes for WSUD assets that complies with AR&R.

The lessons

Engage the council early. Council is on board with the approach, but needs advice on how to quantify the detention and retention volume contribution of raingardens, and clarity on the margin-of-safety factors to account for deterioration of the vegetated systems over time.
Allow for additional coordination among the consulting team. The project required strong collaboration and coordination between landscape design and drainage engineering for the overall design to be successful.
Allow for extra time, because the project is not business as usual. Novel design approaches need extra consideration and time. Often there is insufficient consulting budget in projects to allow for this extra time, especially on small projects. It can be tempting to revert back to more standard ‘grey infrastructure’ solutions to keep the project on time and on budget.