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Hospitalisations increase and asphalt hits 60 degrees without Darwin heat mitigation strategy

By Jesse Thompson, Wednesday September 19, 2018 - 10:22 EST
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Some surfaces in Darwin city heat up to more than 60 degrees according to this heat map. - ABC

Unmitigated heat during hot Darwin days is driving up energy consumption and threatening lives, according to research by the University of New South Wales.

Long-term hospitalisation data examined by UNSW showed a correlation between admissions and days when temperatures of more than 32 degrees coupled with humidity above 80 per cent.

These conditions aren't uncommon during the sweaty build-up months.

"Unfortunately this is what's happening once temperature is very high, or quite high, and humidity is high as well — the hospital admissions are increasing by 200 to 250 per cent," Professor Mat Santamouris said.

The study, handed up to the NT Government, showed heat mitigation techniques could reduce the city's ambient temperature by up to 2.5 degrees and energy consumption by 10 per cent.

Professor Santamouris believed this could save about 10 lives per 100,000 residents per year.

What's causing the heat?

Already hotter than Cairns, Singapore and Denpasar, Darwin's inner-city is filled with asphalt and concrete rather than greenery.

Heat map vision shows car parks and asphalt approaching 60 degrees on hot days, in turn raising temperatures in surrounding areas by up to three degrees.

The high density of buildings, anthropogenic heat and consumption of energy to cool buildings also contribute to urban overheating.

"Never in my life have I seen such a high energy consumption for cooling," Professor Santamouris, who has worked extensively overseas, said.

"All these drivers increase temperature up to two, three, sometimes four degrees.

"This has a very high impact on the energy consumption, peak electricity demand, mortality, morbidity and also the economy of the city."

The heat-mapping study was intended to show the extent of the problem and which areas were most in need.

The solutions — shading hot surfaces with greenery, increasing the flow of evaporated water, coating hot surfaces with light, reflective materials — are in most instances simple, cost-effective and can be done in the short-term, the professor said.

"Even if the cost is quite high, which is not the case, we have to do it, otherwise temperatures will be very high.

"The cost of additional health services will be tremendous."

Urban design plan needed

Strategies to mitigate the heat are already underway.

In Cavenagh Street, the installation of a shade structure is expected to increase comfort with a canopy of vines and misting.

"But we have a long way to go because unless we have a city-wide cooling scheme, we're only going to get small amounts of cool in small places rather than the whole of city centre," architect Lawrence Nield, who commissioned the study, told 's Conor Byrne.

The recently departed government architect warned that in the absence of a coordinated urban design plan, few gains could be made.

Walkability through the city would increase commerce under such a plan, he said. At the moment, people prefer to drive short distances between sweaty city streets.

"We don't have a plan that tells us how much we should have canopies that don't trap the hot air and are actually cool; it doesn't tell us how much greener we should have the city; it doesn't tell us that every car park should have shading over the top of the cars.

"There is not a plan that begins to address, over the whole of the city centre, the questions of heat mitigation."

Professor Santamouris said the city had reached this point because of decades of development without policies that prioritised heat mitigation.

He described Professor Nield's departure as "a concern", but said early talks with the government were encouraging.

Reflecting on his tenure as the government architect, Professor Nield said he achieved about 30 per cent of what he thought he could have achieved.

"I'm not sure whether that's the politicians or the bureaucrats," he said.

While you're here… are you feeling curious?


© ABC 2018

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