#watersensitiveurbandesign

19 February 2020

I get the taste of dust in my mouth every time I think of the word gully. Rain is more memory than experience for many parts of Australia, but even scaling the dustiest of gullies reminds you that it plays a powerful role in shaping both the land and our sense of who we are.

Canberra is a pretty dry place. Its blue skies prevent the winter blues, except, that is, if you are a farmer trying to make a living. But occasionally the rain belts down in a reminder than Sydney is not too far up the road. And when it does rain, water slides off the hard surfaces of an increasingly urban environment, and carries nutrients in to the local streams and our crafted lake. The result is algal bloom and anoxia—water with depleted oxygen—which spells bad news for organisms up and down the food chain.

The creek that runs through our campus is part of this story, but you have to work hard to remember that. Most of the time it’s a desolatory dribble, punctuated by the occasional shopping trolley and a once in a year flood that has me reminding students not to raft on it. It’s a gullied memory of a meaningful place for Indigenous peoples over tens of thousands of years. When someone told me that it hosts a platypus, I was incredulous. I pictured a six-eyed creature in the style of Matt Groenig. Yet it does—a normal one, I hear—and much more besides. Last week a member of the team spotted a ballet of swans.

Large-scale construction projects such as the one in the centre of our campus provides the opportunity to reset the flow and management of water in ways that will benefit the trees, the creek and the lake under the global framework of what is called water sensitive urban design (WSUD), or the related ideas of low impact development in the US (LiD) or a sustainable drainage system in the UK (SDS).

At one level, urban water management is pretty simple. The goal is to filter and to regulate the amount of water runoff, and to reduce reliance on drinking water for uses such as irrigation. How you do that comes down to the species of plants you choose, and methods of stormwater detention, filtering and use.

Take a footpath. Great for walking or wheeling down, obviously, but it’s also an efficient conveyor of stormwater, particularly on a slope. Slope that path from its centre—ever so gently—and you can usher water into accompanying rain gardens.

Plant those rain gardens out with water-tolerant plants and support them with pebbles and free-draining soil mix and water capture outlets and you have the basics for slowing the movement of water down, of filtering out nutrients, and of capturing that water to top up a creek or to retain for irrigation.

Add a weir to raise the level of that creek, and plant out its banks with species including rushes, and you have a much better environment for plants, animals, and humans alike.

Multiple elements are needed to maximise management of water and environmental improvement and maintenance. Not all of them are effective from a standing start, so WSUD also involves ramp-up phrases. You won’t have any water captured after installing rain water capture, and plant species may not be established enough to survive without some irrigation. We acknowledge that we’ll need drinking and irrigation water for some elements at the beginning.

But we’ll get there. That just leaves the rafting and the shopping trolleys to worry about. The former will be managed by the use of a weir that will raise and stabilise the creek water level, and the instillation of a ceremonial fire pit that reminds us all that this is a special place for Indigenous peoples, and to be respected.

The local government has a trolley containment framework—all trolleys require coin deposit, for example—but the related example of oBike dumping suggests that use of GPS data and use ‘good user’ credits is probably also needed to ensure that the only thing that lands up in creeks, gullies and lakes is nutrient-low water. That will make a water-sustained environment more than just a dust-filled memory.