Why can not Sydney cope when it rains?

"And the process of understanding flood risk is well managed," said Dr. Johnson. "The problem occurs when you are using already limited systems."

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A flood similar to Wednesday morning – a 100-year rainfall concentration, based on historical volumes – is still likely to create localized floods.

The drains are clogged with leaves and debris. Water volumes temporarily exceed the capacity of local outlets to cope.

But that does not mean that measures can not be taken to reduce the serious, and sometimes fatal, effects of bad weather on society.

"We expect more events to happen in Sydney," said Beck Dawson, who works with several boards as part of her role as "Head of Resilience" in Sydney, a position funded by the Rockefeller Center.

For Ms. Dawson, to deal with weather conditions made more extreme by climate change, it is essential to incorporate mitigation measures into the new infrastructure. For example, in case of heavy rain, it means trying to disperse the water rather than concentrating it.

"Do we want the city to act like a funnel or a sieve?" Said Ms. Dawson.

A city serves as a funnel for concrete and hard surfaces, concentrating water in places that it quickly submerses.

On the other hand, governments, councils and planners can create sieve effects by offering many opportunities for water to flow and escape. Well designed gardens can do the trick.

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"It's a winning solution for all: you get more greenery in your city, you get less runoff and you also get better runoff, because plants can remove some of the nutrients in the water," said Dr. Johnson said.

However, more rain gardens would necessarily have affected the impact of Wednesday's rain, during which 73 millimeters of rain fell between 6 am and 7 am on Observatory Hill. It's a 100-year event, when most drainage systems are built for events every 10 years.

Also with regard to the city's transport infrastructure, in which separate railway lines were sometimes closed and in which many roads were obstructed or narrowed, the experts urged governments to integrate longer term management.

Geoffrey Clifton, a transportation lecturer at the University of Sydney Business School, blamed the transportation system's "general lack of resilience" on major weather events, in part because of construction decisions made 150 years ago. infrastructure.

Much of the city's railroad, such as the Western Railway Line, was built in the 19th century and was not designed to cope with heavy rains on Wednesday, he said. declared.

"Better maintenance can help, but many infrastructures will have to be rebuilt to cope," he said.

Dr. Clifton also explained that the city's transportation infrastructure was virtually stuck, that a large part of the railroad was above ground, making it more vulnerable than in Europe and Asia, where lines in the big cities were often underground.

Michelle Zeibots, director of the Transportation Research Center at Sydney University of Technology, said the city's ability to cope with the weather has been reduced because of its heavy reliance on the Harbor Bridge. Bridge, become a strangulation. "When you arrive in a city the size of ours, you have to make public transport much more diverse," said Dr. Zeibots.

And then there are the predictable problems. For example, almost every time there is a local flood, Lewisham station in west central Sydney becomes inaccessible. And still it happened Wednesday.

A spokesman for Transport for NSW said that corrective maintenance work had been completed at the Lewisham station, including the installation of an inversion valve to mitigate floods.

The incident at the station Wednesday morning was caused by a nearby power outage that disrupted a pumping system for about 50 minutes and hampered efforts to reduce flooding.

"The Sydney trains have taken a number of steps to mitigate the risk of flooding our network," he said. "We continue to consider other mitigation measures at places such as the Marrickville station that are prone to flooding."

Dawson said much work has been done to prevent the flood from becoming more severe.

"This event has been predicted. Many organizations have put in place weather protection programs to actively clean the streets to remove debris. They can not enter the pipes and block the streets, "Dawson said.

"No one will have noticed it, but it's a bit of boring preparation work that means a lot of disasters did not happen today."