Tuesday, March 05, 2013

Urban Stormwater Management – Smarter Solutions and Better Stormwater Use

While almost no urban sewerage system in Australia is designed to also handle stormwater, as is the case in some older cities, particularly in the USA, the management of stormwater productively is quite a challenge.  With our increasingly hard surfaced cities, the stormwater system has grown, usually channelling away water that previously would have often dissipated within the landscape where it was generated, often even into the ground, or at least nearby.
While there are places around Australia where the stormwater is planned to move and actually recharge local aquifers, with Mawson Lakes near Adelaide a good example, as is some stormwater even around Palmerston, recharging the aquifer under the city in the wet season.  Normally, most stormwater runs off, and is lost to local use.

With about 80% of contaminants on hard surfaces, being moved with the first flush of rain [even more in the tropics with the first break storms of the wet season], colleting that and filtering through land and used by plants is a major and distinct improvement to the quality of stormwater discharged into nearby rivers, creeks and ultimately the harbours and oceans.  Most of the pollutants are remediated by soil borne organisms.
But driving that change is difficult as engineering has dominated how urban stormwater has been managed and the usual method has been pipe, or surface hard channel it, away.

More localities are reconsidering this however, through design modification to use plant based drains and detention areas before excess water flows elsewhere.  Volumes handled by expensive engineered solutions are often decreased as is cost, and water is used productively near where it is produced.
Better design can actually increase volumes handled by bioengineering approaches, so often even reducing overall costs.  This type of approach may even be retro fitted at modest cost or with little disruption to existing facilities.

It is more difficult in monsoonal areas with major differences in urban water between the wet and dry seasons, but it is possible to modify designs to at least allow a reduction in irrigation in the early and late wet seasons by better using locally generated surface waters locally with better design of roads and local parklands.
Some projects have been finished in Sydney as well as overseas. There are some smart designs on the web site of www.atlantiscorp.com.au  used in Sydney, an Australian company in this design space.  See more here -  http://www.atlantiscorp.com.au/solutions/civil-engineering/road-solution-drainage .

More are being planned, with some further details here –

And then there are green roofs, aimed at collecting and using water that falls on buildings and preventing much of that getting to street level – it helps cool buildings too, reducing heat load on concrete roofs.  More of these options are developing.

We just do not do enough of these more appropriate solutions here in the NT. 

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