Is 'dry development' possible in Australia's West?

When working in low-lying areas, development projects are often plagued by ‘water problems’—rising groundwater, complex engineering, the huge expense of fill.

It’s a problem that we’ve been facing for a long time here in Western Australia (WA), and an issue I’ve spent a lot of time considering as part of my PhD.

This week, I’ll be sharing insights from my thesis research at the Institute of Public Works Engineering Australasia (IPWEA) state conference, talking about how shallow water table issues are being addressed overseas, and locally here in WA.

While some view urbanisation in low-slung areas of Western Australia as involving a fundamental choice between ‘wet feet’ (dealing with soggy ground and periodic flooding when the water table rises post-development) or absorbing the huge cost of building sites up with extra fill, I believe there are options to minimise both these negatives.

Shallow groundwater is not a unique development problem

Through my research, I’ve compared how many cities are addressing the challenges of shallow groundwater. There are a variety of engineering solutions—or combinations of solutions—in play.

The Netherlands is a classic example with two-thirds of the entire nation sitting below sea-level. In Amsterdam, an intricate set of engineering interventions—dikes, ditches, pumping and fill—keep homes and businesses from being inundated. In other cities, the control measures include a combination of swales, canals, stormwater retention ponds, along with imported fill to elevate building and infrastructure sites.

From looking at different international case study examples, it’s clear that no solution is 100% foolproof, and that engineering interventions must be location-specific. What works in Holland is not necessarily a workable or viable solution for WA.

What’s important to note is that there is more than one way to think about groundwater problems, and the ways we might solve them through engineering.

Drainage water capture in Perth estate development

Excess meets scarcity in suburban Perth

In addition to the huge cost of fill, here on the Swan Coastal Plain we do face another water issue. In local areas we experience problematic shallow groundwater across the wetter seasons, while groundwater reserves are dwindling. So much so that developers in some areas are scrambling to find the water they need to irrigate public spaces.

In 2017-18, the Integrated Water Supply Scheme which supplies Perth, the Goldfields Region and parts of the South West sourced 40 per cent of its water from groundwater aquifers. In some areas, however, developers are prevented from sinking bores for things like the irrigation of parks, as groundwater is simply too scarce a resource.

On the flip side, as the water table is already shallow and new construction only serves to raise it further, it’s estimated that developers are spending up to 40 percent of their construction budgets on raising sites with imported fill.

Not only does this make housing more expensive and construction a longer, more complicated process, but the mining and transport of fill comes with its own set of environmental issues.

A two birds approach yielding benefits on the Swan Coastal Plain

As part of my thesis research, I have been investigating an approach that addresses scarcity and excess issues in tandem.

Rather than raising sites up to increase the barrier between the water table, homes and infrastructure, implementing other engineering options while at the same time capturing and harvesting excess drainage can minimise fill requirements (and costs) significantly while opening up a new possibility...The opportunity for communities to retain and reuse this excess to augment local water supply at the precinct scale, and improve groundwater quality while doing it.

Perth suburban development featuring groundwater solutions that reduce the need for fill while facilitating drainage harvesting

Pursuing true sustainability

I’m a big believer in the need to pursue sustainability in all its forms—environmental, economic and social. When a solution only focuses on one of these facets, we run the risk of creating new issues to replace the old ones.

A large portion of my PhD research has centred on solving an economic issue facing developers—the huge requirement and significant costs associated with importing fill to address the shallow groundwater conditions typical to Perth and surrounding regions.

What makes me passionate about my work, and sharing it with people, is the evidence it provides. Not just in the form of measurements and modelling that can drive better outcomes for specific people and projects around my home city, but for a broader sustainable design idea...That using engineering and science to address economic problems doesn’t have to come at the cost of environment or people. It can, and should, generate benefits for all three.

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