Have you ever thought stormwater management is just too complex? We are managing proposed developments to peak flows, imposed detention requirements, sometimes effective imperviousness and then water quality requirements. On top of this, we are asked to match the peak flow in the 1.5 year ARI (VIC) or something even more complicated as in NSW. And now let's throw in BASIX and other related planning requirements.
This is excellent for keeping our industry and consultants busy, but is it all necesssary?
Perhaps there is a simpler and more holistic way that can manage all facets related to stormwater for new developments.
What if requirements can be simplified and lead to better outcomes?
What if there was a single simple stormwater condition that addressed both peak flow and water quality targets, protects our urban waterways, eased complex planning restrictions, encouraged further industry innovation, could be readily applied throughout Australia at very little cost, can reverse the clock on flooding and waterway degradation and could be expressed as one number?
This would simply be amazing - what is it? Your Stormwater Footprint!
Curious?
Our current practices are not really coping with development pressures with flooding levels seemingly always increasing and degradation of our waterways. Climate change is certainly magnifying issues. We do need another way of looking at stormwater management and this could potentially be it.
Try it on, discuss it with your colleagues and let us know. Not only can we better manage flooding and stormwater quality but we can effectively protect our waterways from stormwater volumes, reduce potable water demand, decrease urban heat islands, decrease leaks to sewer and improve public amenity.
How does this work?
The shift in thinking is to adopt a volume metric to stormwater runoff. Your Stormwater Footprint is the runoff volume post development divided by the pre-development runoff volume. A Stormwater Footprint of 1 means that the post development runoff matches the pre-development. A Stormwater Footprint greater than 1 allows more runoff post development which is the current practice that would be appropriate where a regional stormwater scheme is downstream of the site. A Stormwater Footprint less than 1 will start to wind back the clock on flooding (similar to UPRCMT) and stream degradation.
There is no defined way of achieving the specified Stormwater Footprint – get creative. Treatments like smart rainwater tanks would have a significant impact on Your Stormwater Footprint. Infiltration would assist as well. The larger the proportion of the site that is proposed as impervious surfaces the more difficult it is to achieve that required Stormwater Footprint. This places a natural restriction on imperviousness of the site but also invites innovation.