Extreme flood risk: New report outlines potentially disastrous scenario for Ho Chi Minh City

Extreme flood risk: New report outlines potentially disastrous scenario for Ho Chi Minh City

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Ho Chi Minh City faces devastating floods over the coming decades. (Photo: AFP/Kao Nguyen)

BANGKOK: The risk of extreme future flooding events in major Vietnamese metropolis Ho Chi Minh City could increase by up to 10 times by 2050, resulting in immense economic and infrastructural damage, according to a new study by an international consulting firm.

Without a concentrated effort to mitigate the worsening impacts of sea-level rise brought about by climate change and to improve urban planning, the city faces billions of dollars of damage on an annual basis, with freak events potentially devastating vast urban areas.

The report by McKinsey Global Institute provides a snapshot of flooding in the fast-expanding city by analysing hydrological simulations, land use maps, infrastructure databases and damage curves. The future, without action, will become increasingly difficult to manage, it concludes.

As time passes and Ho Chi Minh City grows at a rapid pace, the impacts will increase exponentially. A flood with the same probability as today in 30 years’ time will cause triple the amount of infrastructure damage and 20 times the knock-on effects.

Ho Chi Minh inundation flood graphic
A visualisation of depths and extents of 100-year flood in 180cm sea-level rise scenario in Ho Chi Minh City. (Graphic: McKinsey Global Institute)

Major projects currently underway, including the underground metro system, as well as new power plants, wastewater processing plants, data centres and a new airport, would be valuable assets highly exposed to future risk. 

With electricity demands to triple from 2015 to 2030, a surge in development means new infrastructure will face a more tenuous lifespan. 

If climate change was not mitigated and sea level rises hit 180cm by the end of the century - as forecast under a worst-case scenario - a once in a century flood would inundate two-thirds of the entire city.

In this extreme scenario, the city centre would become an island. Major power stations, ports and half of all roads would be damaged. 

Also, the metro would likely be shut down with 60 per cent of the station’s inaccessible and real estate damage could top US$18 billion. Water supplies and electricity could be cut off, with the city effectively shut down for a month or more.

READ: The fight to save Bangkok from sinking into watery depths

While Ho Chi Minh City’s prospects seem very bleak with such forecasts, the study's chief researcher told CNA that the intention is not to paint an alarming picture.

“The goal of this research is not to be alarmist, but rather give stakeholders a way to understand physical risk and its socioeconomic impacts and identify a set of actions to manage the risk,” said Mekala Krishnan a senior fellow at McKinsey Global Institute.

“Ho Chi Minh City is still relatively early in its infrastructure journey and has many options at its disposal to continue its impressive growth trajectory, while reducing climate impacts,” she added.

Vietnam flood
Flooding is a common feature of Vietnam's monsoon season. (Photo: AFP/Anthony Wallace)

FLOODING "MOSTLY A MAN-MADE PROBLEM" IN THE CITY

Ho Chi Minh City has an intrinsic relationship with water. Access to rivers, canals and the sea helped transform a strategically located village into the economic powerhouse of one of the world’s fastest growing economies. 

Flooding, storm surges and monsoon rains are common features on the city’s calendar and for generations, its population has learnt to live with the disruptions that come with these events. More than 40 per cent of the city is less than one metre above sea level.

But the original ingenuity of planning around nature has succumbed to expansive development. Domestic migration to urban areas has soared and lower-income populations have been pushed to areas with higher flood risk. 

“As the city expanded, we started to fill up floodplains for human settlement and disrupted natural drainage systems, then the flood came. Until now, flooding is mostly a man-made problem in the city,” said Dzung Do Nguyen, the founder and group managing director of urban planning consultancy firm, enCity.

Ho Chi Minh statue
A statue of Ho Chi Minh in the centre of Vietnam's economic powerhouse. (Photo: AFP/Christophe Archambault)

“The constant level of development is quickly taking over any remaining drainable land and covering it with concrete. It is relentless,” said Melissa Merryweather, the director of Green Consult-Asia, a Vietnam-based consulting service focused on the green building market.

“A lack of future vision means that flooding gets out of control, and then the sewers are expanded as a response. At the same time, there has been a gradual erosion of green areas in the city and no new green areas have been introduced in decades.”

Climate change will make the city’s existing problems worse. Local rainfall is forecast to become more intense as regional sea levels rise. McKinsey’s researchers say they have been conservative with their estimates of increasing precipitation and how common extreme rain events might be in the coming decades.

Vietnam has been slow to adapt to climate change. Its economy is highly reliant on fossil fuels and coal production is set to increase over the next decade. 

Its Paris Agreement target is an unconditional 8 per cent reduction of greenhouse emissions on business as usual levels by 2030 - a pledge considered critically insufficient by Climate Action Tracker, an independent consortium that tracks government action on climate.

HCMC canal
Low-income earners are pushed to the riskier fringes of the city. (Photo: AFP/Kao Nguyen)

“Estimates on climate change’s impact are based on one unlikely scenario: we do nothing. So they are helpful for the government to decide how much they should invest into solutions,” said Dzung, the urban planning consultant.

“We need to be aware that unlike other natural disasters, climate change is a long process - long enough to allow government, society and the environment adapt to its conditions. Policy change in Vietnam is usually not explicit but implicit and subtle.”

READ: Why Manila is at risk of becoming an underwater city

The city has already made investments in its flood defence system, including pledging to spend US$4.4 billion to further bolster its protections over the next five years. 

But the report stresses this will likely be insufficient, noting that Singapore’s estimated budget for sea level rise sits at US$72 billion, while Jakarta’s major coastal defence plan will cost approximately US$40 billion.

Dzung says solutions proposed to protect the city from the sea, such as river dykes, may only shift flooding problems elsewhere and affect stormwater discharge. “We need to create more water bodies within urban areas and avoid building in low and swampy land,” he said.

Ho Chi Minh City aerial
Worst case scenario flooding would result in major inundation of the city and its important infrastructure. (Photo: AFP/Kao Nguyen)

Merryweather of Green Consult-Asia believes that instead of waiting for grand solutions from the government, small improvements can come from the private sector. But there are obstacles, she says. 

“There is very little information available publicly so that the private sector can take action. We know that micro-improvements on land owned by developers would make a significant difference,” she said.

“At this time, it is only possible for the government to plan and combat potential flooding since there is little hope of the private sector adding to resilience capacity.”

HCMC skyline
Ho Chi Minh City is a fast developing metropolis with huge new infrastructure needs. (Photo: AFP/Hoang Dinh Nam)

MANGROVES TO THE RESCUE?

The study agrees that revising real estate codes would help. But greater benefits are likely from restoring nature itself, particularly the extensive mangrove system close to Ho Chi Minh City. 

Mangroves currently offer significant protection from more extreme events, reducing the height of storm surge by 20 per cent or more for every 100 metres of forest, the report outlines, noting that the city has made substantial achievements in replanting over the past three decades.

And while climate impacts are coming fast, there is still time. Less than half of the infrastructure needed by 2050 exists today, giving planners opportunities to forge solutions.

“Adaptation is in our blood. It is a strong character of the Vietnamese,” Dzung said. “So I believe we will be able to navigate through this climate change, but I am still unsure how we will do that.” 

Source: CNA/jb(aw)

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