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The White Hat Guide to Water Sensitive Urban Design (WSUD) in Australia

What is WSUD? With water restrictions in most Australian cities we have become more aware of managing our water. We plant drought resistant plants, let our lawns go yellow in the dry season and collect and reuse water where we can. If we were starting from scratch on our property, neighbourhood or precinct what would we do differently about managing water?

I suppose the main principles of WSUD (Water Sensitive Urban Design) boil down to:

Collect your fair share of the water falling on or passing through your property. Use it wisely. Pass on the rest in good condition.

In the next few newsletters we will look at several aspects of WSUD but let’s start with perhaps the least discussed area – pass on the surplus water in good condition.

In the 50s and 60s dealing with water runoff in cities was pretty straightforward. Most of the city and inner suburban area was paved so rainfall drained off to the gutters as did the water collected from the roofs. The middle suburbs were less paved but still the runoff from the roofs, roads and driveways was directed into the gutters. From the gutters, the water was directed into underground stormwater drains which in turn made their way to the nearest natural waterway – be it a creek, river, bay, harbour or the sea. Nothing wrong with that. That is where the water would have ended up before the city was developed.

Well, as it turned out, there were a few problems. For a start the water was now being fed into the waterways in larger quantities. Before settlement much of it would have laid in swamps and soggy ground before gradually making its way into the waterways but now with all those paved and covered areas it was all arriving at once. This meant the downstream areas had to be upgraded to handle the increased flows. Creeks are messy, untidy things anyway which don’t flow in a logical direction. Replace them with a wide concrete channel. A good example is the Moonee Ponds Creek in Melbourne which runs next to the Tullamarine Freeway. That can handle a much bigger flow than the original creek and after the flows from a heavy downpour have subsided you can send a truck up the side of the channel to pick up any debris which has been washed down. Much better than the messy old creek with its snags and smelly reed beds.

Then there was the problem of the water that was entering the system. In the past it had filtered its way through the swampland and reedbeds but now the dog droppings and chemicals from the roof paint and all manner of other things were being efficiently funnelled into the creek system which in turn had no snags and vegetation systems to ‘polish’ out the harmful chemicals, remove excess nutrients or slowly dilute the e-coli levels. The water had been quickly and efficiently removed from the roads and properties in the city and was now ‘someone else’s problem’.

Planners were doing the best they could with the knowledge they had at the time and many post-war families owe a debt of gratitude to the people who helped keep their fledgling properties drained and flood-free. However our understanding has moved on since that time.

Most of our major cities have recognised that the state of the water entering our waterways needs close attention and there are some important projects in Sydney, Melbourne and other cities. They have recognised that not only do the lands next to the waterways have to act responsibly about the water they release, but often they have to try to fix the problems with the runoff delivered further ‘inland’. Sydney is well underway with creating a ‘green necklace’ of harbourside parks which do their best to ‘massage’ the water released into the harbour. Melbourne’s greyfield site of Docklands has had a WSUD policy in place since the commencement of its redevelopment.

Some of the things you might expect to see in such precincts are:

• Soaks – slightly sunken areas where surface water is allowed to slowly sink into the ground
• Swales – slightly sunken areas where reedbeds and other vegetation capture the chemicals and nutrients from the runoff
• Water features – that help aerate the water and humidify the local atmosphere

The whole area of WSUD is obviously large and complex and very important in the area of city design so more in our next newsletter. In particular we will return to some of the things we can do at a local property level to pass on water in the most responsible manner.

Royal Society of Victoria - free lecture Professor Iven Mareels (Dean School of Engineering, University of Melbourne) speaks on “Managing Water: A System Engineering Point of View” 7pm, 14th June 2012 The Royal Society of Victoria, 9 Victoria Street, Melbourne - Free and open to the public