An international team of engineers from California and Melbourne are investigating methods for optimizing urban rainfall management by emulating the behaviour of water in natural ecosystems, and have found that Australia is a leader in this field.

The team of engineering experts from the three University of California campuses (UCI, UCLA and UC San Diego), Orange County Public Works, consulting firm Michael Baker and the University of Melbourne have collaborated on a new review paper that examines how low-impact development technologies (LIDs) can improve the management of urban stormwater runoff.

The authors of the paper, which was recently published in the American Chemical Society journal Environmental Science & Technology, point to the urgent need for improvements to urban stormwater management in places such as California and Australia, where climate change is expected to create the twin problems of increasingly frequent droughts and heavy storms.

Enhanced management of urban precipitation is also needed to help deal with the problem of pollutants entering the environment via stormwater runoff.

“The massive volumes of pollutants associated with stormwater runoff are a deadly one-two punch for streams and lead to a condition known as ‘urban stream syndrome,’” said Asal Askarizadeh, lead author and UCI graduate student in civil and environmental engineering.

The solution to these dilemmas could lie in LID technologies that mimic the natural landscape’s handling of heavy precipitation levels prior to the creation of the built environment.

Stormwater management methods categorised as LIDs include green roofs that are capable of both absorbing then evapotranspiring rainfall and the installation of permeable pavements on the urban landscape for enhanced channelling of precipitation.

They also include more familiar and commonplace measures such as rainwater tanks and recycling of water in the bathroom or laundry.

According to Askarizadeh, LIDs could solve the dilemma of both water scarcity and pollution of the natural ecosystem by harvesting and recycling stormwater runoff to the greatest extent possible while also allowing some precipitation to enter the environment for the maintenance of ground water and other natural water formations.

The new paper argues for the creation of a diffuse network of LID infrastructure comprised of green roofs and rainwater tanks in order optimize the efficient channelling and recycling of heavy precipitation.

“In order to protect receiving waters and streams, we need to capture the runoff as close to where it’s generated – for example, your home- as possible,” said Brett Sanders, report co-author and professor and chair of the Department of Civil & Environmental Engineering at UCI.

The paper also examines how to best dispose of stormwater once it’s captured, based on climate conditions and the pre-existing natural environment.

“Our work provides a blueprint for estimating how much of the captured water should be infiltrated into the ground and how much should be harvested for any purpose that keeps it out of the stream, such as for nonpotable purposes in the home,” said Megan Rippy, a UCI postdoctoral researcher in civil and environmental engineering.

“The ratio of those two volumes depends on local climate and what the landscape looked like in pre-industrial times.”

The researchers note that Australia, and Melbourne in particular, is already taking the lead in effective handling of stormwater runoff, given the challenging climate conditions that the country already faces.

“[Australians] have had a positive experience implementing LID technologies to manage scarce water resources, and in doing so, they’ve provided a good example of how universities can work with governments and private-sector entities to come up with solutions for water challenges,” said Stanley Grant, professor of civil and environmental engineering at UCI and senior author of the paper.

“The best part is that after emerging from one of the longest droughts in Australia’s history, Melbourne has been voted year after year as the most liveable city in the world. We could definitely use some of their magic.”