Global South metropolises 10 times more likely to be affected by flooding than rich cities: study

China’s coastal cities face the greatest risk from flooding over the next three decades, along with key Asian municipalities Mumbai, Dhaka, Bangkok and Quezon City.

Zhejiang, China
The town of Jiaxing in Zhejiang, China. Image: Song SongrooveCC BY-SA 3.0, via Wikimedia Commons

City dwellers in developing countries are 10 times more likely to suffer damage to their homes and livelihoods from riverine and coastal flooding than residents in wealthy cities, based on the findings of a new study that seeks to quantify the impacts of climate change.

Among cities in the Global South, those in South and Southeast Asia will suffer the most, according to a report by C40 Cities, a network of megacities committed to addressing climate change. 

The Global South refers to regions in Asia, Africa and Latin America which are mostly low-income or politically marginalised.

“Flooding is a complex threat that cities are navigating. Cities will have to protect their critical infrastructure from the damage stormwater flooding can wreak,” said the report titled Water Safe Cities

Chinese metropolises are expected to suffer the most from flooding in the developing world by 2050. The rivers of coastal cities Zhenjiang and Fuzhou are projected to be inundated by up to 800,000 cubic metres for every square kilometer (m3/km2), equivalent to about 320 Olympic size swimming pools. 

Densely-populated Guangzhou and Shenzhen are projected to flood by up to 330,000 m3/km2, if nations fail to rein in the climate crisis.

The rivers of Mumbai, India’s commercial capital, will overflow by about 330,000 m3/km2, made worse by coastal flooding from rising sea levels and storm surges. Flooding already costs Mumbai US$65 per person every year. But under a business-as-usual scenario, this will rise to US$249 per capita per year by 2050. Dhaka, Bangladesh’s capital city, is estimated to see the largest spike in flood cost among Global South countries, from US$52 today to US$607 over the next three decades. 

Riverine flooding in Vietnam’s Ho Chi Minh city is expected to have about the same impact as on Mumbai, but flood damage will cost seven times more by the first half of the century than the current toll of US$65 per citizen. 

Bangkok, Jakarta, Kuala Lumpur, and Quezon City in the Philippines are each anticipated to witness flood volumes of 50,000 m3/km2, but it will be Thailand’s most populous city that will take the biggest hit in flood destruction expenses, with a 400 per cent increase by 2050. 

Outside of Asia, Salvador in Brazil, known for its ports and beaches, will flood up to 330,000 m3/km2, while Ghana’s coastal area of Accra may sink under 50,000 m3/km2 of water. 

This is in contrast to the flood damage predicted for cities in richer continents. Only New Orleans, Houston, and Portland in the United States, and Oslo, Norway face flooding peril. 

Cities around the world will experience combined flood volumes of 10.5 million m3 annually, exposing 7.4 million people to inundation risk, the report added. 

The annual cost of urban flood damage will treble to US$64 billion each year, resulting in a US$136 billion fall in global gross domestic product.  

Some cities are tackling the flooding threat by implementing river catchment management programmes. Oslo has developed a river basin plan, for instance, while Singapore has naturalised the previously concrete-walled Kallang river, which runs through the city’s central Bishan Mio Park, preventing the frequent flooding that nearby roads were prone to.

Climate migration: key factor to coastal flooding

Asian cities are home to the most flood-prone people, and the region’s population is set to increase rapidly by 2050, largely due to climate migration, said the research. 

“Migrants inside cities, often face greater vulnerability, as they trade one set of risks for another when they leave their homes, then settle into vulnerable housing in informal settlements made of fragile materials, often in high-hazard-risk areas,” read the report. 

Elsewhere in the Global South, 50,000 people moved from the Nigerian countryside to Lagos in 2018 due to climate change – the largest such movement of people in Africa. This climate migration had a major impact on the city’s economy, infrastructure and services.

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