A comprehensive risk assessment supported by Sydney's metropolitan councils has found economic, technological and social changes mean the city's five million residents face increasingly complex threats over the next 30 years.

Growing integration with the world economy has made the city more susceptible to global financial shocks. The rapid proliferation of digital technologies has introduced an array of potential disruptions. Meanwhile, the effects of climate change will make extreme weather including heatwaves and storms more frequent and intense.

The city-wide risk assessment, which was backed by the Rockefeller Foundation's 100 Resilient Cities Initiative and local councils, identified the eight potential shocks that would paralyse the city and cause widespread economic and social disruption.

"Building resilience starts by identifying our most important problems first and figuring out the best ways to tackle them together," said Beck Dawson, the report author and chief resilience officer with Sydney's 100 Resilient Cities Initiative.

Similar risk assessments have been carried out for 100 cities across the world with the aim of making them more resilient.

The eight biggest shocks threatening Sydney are:

1. Extreme weather

Collaroy's beach front houses were among those hardest hit by this year's big storm. Photo: AAP

Sydney's climate is changing and the city is likely to encounter more heatwaves, intense storms and bushfires. The risk assessment showed more people in Sydney are directly affected by heat stress than any other natural hazard.

"In January 2013 we had our hottest day, 46 degrees, and 350 people were hospitalised that day, many of them were unconscious, due to heat related illness," Ms Dawson said. Heatwaves also put key services including, health services, transport and electricity networks under stress.

Sydney is also vulnerable to flooding due to extensive urban development in the flood plains of the Hawkesbury, Georges and Cooks rivers. Storms, flooding and hail regularly cause major disruption to urban transport networks at considerable cost the economy.

2. Failures of large financial institutions

Sydney's economy is exposed to global changes. Photo: Peter Braig

Sydney is heavily dependent on the financial and insurance services industry. It commands a 16.2 per cent share of the city's economy the consultancy SGS Economics and Planning estimates, which is far more than any other industry sector. That means Sydney's economy is exposed to major fluctuations in global financial markets.

"When there is major blip in the global economy it is particularly felt here," said Dawson. "The global financial crisis of 2008 was a good example.

The city's economy, especially employment, would be badly affected if one of Australia's major financial institutions – such as a major bank or an insurance company – were to fail.

3. Infrastructure failures, especially power outages

Commuters were plunged into chaos, and darkness, at Sydenham station. Photo: Wolter Peeters

The way Adelaide was plunged into darkness after a storm damaged power infrastructure last month underscored how dependent modern cities are on electricity.

"Once you have a power outage you loose a lot of basic services including transport, water and lot of other things," said Dawson. "Most of the big infrastructure failures we have seen are linked to power outages."

The failure of important infrastructure such as power, road or rail can cause huge disruption across large parts of the city at significant cost to the economy.

The risk assessment singled out health infrastructure, airports and the rail network as the city's three most vulnerable infrastructure assets.

4. Disease pandemics

Babies in Brazil have been born with Zika-linked microcephaly. Photo: Getty Images

International bird flu, swine flu and the zika virus outbreaks over the past decade have drawn attention to the economic and social disruption caused by disease pandemics. Sydney is vulnerable to international pandemics because of its growing integration with the global economy and a significant tourism industry.

"Pandemics can have a direct impact on everyday businesses because they stop people moving around and meeting with each other," Dawson said. "When people cease connecting with each other business activity slows."

The risk assessment said chronic illness and lifestyle diseases such as obesity and diabetes are on the rise in Sydney, increasing pressure on our health system.

5. Water crisis – too much or too little

Stormwater causes localised flooding at Cronulla. Photo: John Veage

The risk assessment ranked Sydney's wastewater and stormwater system as the city's fourth most vulnerable infrastructure asset because of its age and capacity constraints.

As the city gets more high rainfall events there is an "increasing level of urban flooding," says Dawson. The failure of stormwater networks poses a pollution risk Sydney's many waterways.

The risk assessment also found Sydney's supply of drinking water could come under pressure due to lower average rainfall, higher temperatures and a growing population. The city's water supply network was ranked among the city's eight most vulnerable infrastructure assets because of "limited diversity and availability during droughts". The assessment called for "innovation" in Sydney's water management.

6. Digital network failures

Increased reliance on digital solutions means increased risk if networks go down. Photo: Supplied

Many of Sydney's critical services, including the payments system, depend on continuous data supply in order to function. Sydney also has a growing digital industry. That means any network interruptions can have knock-on effects across the whole economy.

"Even a disruption to one supplier of broadband or mobile technology, such as Telstra, affects millions of people and businesses," said Dawson.

The risk assessment said an "increased reliance on digital solutions" was one of the key trends that would influence the city over the next 30 years. Finding ways to mitigate the impact of digital network failures will be crucial.

7. Cyber attacks

Cyber attacks pose a major threat to Sydney. Photo: Erin Jonasson

Recent cyber attacks on the national census and the Bureau of Meteorology have grabbed headlines but the risk assessment found they also pose major threat to Sydney because services and commerce have become so dependent on information technology. It said a growing number of businesses and government agencies in NSW are coming under cyber attack.

"This is a global trend but Australia seems to be particularly vulnerable because we haven't done a huge amount of work on it, our businesses in particular, compared to some other countries," Dawson said.

8. Terror attacks

Thousands of floral tributes left in Martin Place following the Lindt cafe siege in 2014. Photo: Cole Bennetts

While Sydney's critical infrastructure is less vulnerable to terror attack than many parts of the world, the Lindt Café siege at Martin Place in December 2014 showed the city is not immune. In addition to the tragic loss of life, that emergency stunned the city and shut down its commercial hub.

"Terror came out very strongly in the public's perception of risk," said Dawson.

"There's a real sensitivity too it."

Research for the risk assessment found nurturing social cohesion will be an important challenge for Sydney in coming decades.

Sydney's eight chronic stresses

Diminishing social cohesion, high housing costs and growing inequality are among eight chronic stresses tearing at Sydney's social fabric, the city-wide risk assessment has found.

These nagging pressure points will have a major bearing on the quality of life enjoyed by Sydneysiders over the next 30 years.

The chronic stresses are:

1. Increasing demand on health services

2. Diminishing social cohesion

3. Loss of housing affordability

4. Increasing chronic illnesses

5. Lack of transport diversity

6. Insufficient employment diversity

7. Increasing geographic inequity

8. Rise in drug and alcohol abuse

Some of these long-term stresses overlap. About half of the city's adults are overweight or obese, contributing to an increase in chronic "lifestyle illnesses" such as diabetes and heart disease. This stress, along with the rise in drug and alcohol abuse, both exacerbate the first problem listed – increasing demand on health services. The risk assessment said catering for the health care needs across the Sydney entire urban sprawl was a key challenge.

Beck Dawson, the report's author, said social and economic inequality was an "underlying theme" in the chronic stresses affecting Sydney.

Rising housing costs, a lack of employment in western Sydney and limited transport options in some suburbs have all contributed to "increasing spatial inequality" across metropolitan area.

"Because of patterns of settlement and because of our geography we are quite a polarised city," Ms Dawson said.

Many cities across the world which have conducted a similar risk assessment have identified inequality as a challenge.

Sydney's risk assessment also drew attention to growing distrust between communities and described declining social cohesion was one of the city's "disruptive issues".

Ms Dawson said Sydney is relatively well resourced to deal with future stresses and shocks but a high level of collaboration between metropolitan councils, the state government, businesses, academics and the community was needed to make the city more resilient.

"This is all about understanding our city so that we can make the very best of the resources we have available," she said.