Climate change is intensifying rainfall in Southern Africa, where rapid urbanisation and poor drainage made recent flooding in Botswana and South Africa deadly, a group of scientists said, while a separate study showed some of the continent’s biggest cities are being squeezed by wet and dry extremes.

Last month, southern Botswana and eastern South Africa suffered five consecutive days of heavy rainfall which caused severe flooding across the region, killing at least 31 people, including six children, and displacing about 5,000 others.

Such episodes are becoming more frequent in a warming world, found scientists working with the World Weather Attribution (WWA) group, based in Botswana, South Africa, the UK, Denmark, the US and elsewhere.

Alongside heavier precipitation, a key driver of disasters in cities is inadequate infrastructure, they said. For instance, in Botswana’s capital Gaborone, drainage systems have not kept pace with its growing population density and fast-expanding construction, making low-lying areas particularly susceptible to severe flooding.

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With today’s global warming of 1.3C, a warmer atmosphere is holding more moisture and leading to more extreme downpours, said Ben Clarke, one of the WWA research authors. “To limit the damage, we need to cut fossil fuel emissions and adapt to a warmer climate,” he added.

Piet Kenabatho, a professor of environmental science at the University of Botswana, said investment in better storm water management systems “is more than urgent if Botswana is to cope with the effects of climate change”.

While the researchers could not quantify the precise contribution of climate change to February’s flooding, they said historical weather observations show an increasing trend in five-day rainfall over the last few decades. Based on the data, they estimated that similar rainfall events are about 60% more intense today than in pre-industrial times, before humans started burning fossil fuels.

Clarke warned that climate models show the situation will become even more dangerous in the future.

To understand the broader implications for Botswana and its development, Tiro Nkemelang, of the Botswana Institute for Technology Research, called for more investment to study local weather and climate.

Water woes worsen

At the same time, in East Africa, more severe droughts are giving way to heavier floods, a back-to-back pattern that is becoming more pronounced, with three capital cities – Nairobi in Kenya, Addis Ababa in Ethiopia and Kampala in Uganda – experiencing this so-called “climate whiplash”, according to research issued this week by international charity WaterAid.

The phenomenon, also affecting Cape Town, sees prolonged droughts that can cause water shortages, food insecurity and electricity disruptions interspersed with intense rainfall, overwhelming urban drainage and resulting in flash floods that displace communities, damage roads and spread waterborne diseases.

“The rapid shift between these extremes makes it difficult for people to prepare and recover, damaging economies and endangering lives,” the report said.

Sudan’s capital Khartoum and Cameroon’s capital Yaoundé, meanwhile, are experiencing a flip in their prevailing climate trends from wet to dry extremes, with the opposite happening in the Nigerian city of Kano, the study found.

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The research comes at a pivotal time, when a sweep of global aid cuts “could leave basic human rights hanging in the balance”, warned Tim Wainwright, WaterAid UK’s Chief Executive. He said the devastating impacts of the shifts in extreme climate patterns across all continents are being most keenly felt in low-income countries, where the lack of water is not just a challenge, but a matter of life and death.

The research – which looked at the world’s 100 most populated cities – revealed that cities in Southern Asia are becoming overwhelmingly flood-prone and European cities are exhibiting significant drying trends, all of which can impact people’s clean water access and water security.

“Floods and droughts are stripping away people’s foundation of survival – water,” said Wainwright. “But with a reliable supply of clean water, communities can recover from disasters, stay healthy and be ready for whatever the future holds.”

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Age of “climate whiplash” puts residents of Africa’s fast-growing cities in danger