The elegant buildings of Gatumba, a town on the outskirts of the capital Bujumbura, are a reminder of its recent prosperity.

But all too often, residents must pitch tents on their roofs, while children float between houses on rafts made of plastic bottles.

"We've been underwater for years," said Asha, 32.

The level of Lake Tanganyika rises cyclically but has been exacerbated by global warming, said Bernard Sindayihebura, an urban planning and environment specialist at the University of Burundi.

Surface temperatures on Africa's second-largest lake have been rising steadily, causing more rain and pushing the lake above its historical average since 2018, he said.

The high water level means the Ruzizi River cannot flow into the lake, flooding the surrounding area year after year, including Gatumba on its northern shore.

Asha fled with her family during a particularly severe flood in 2023 -- which reached up to her waist -- seeking refuge in temporary shelters nearby.

They were flooded again a year later and again this year, with the waters swallowing up many neighbourhoods.

The area once thrived thanks to its fertile land and trade across the nearby Congolese border.

But the floods destroyed farmland and schools, said Asha, who previously lived off her crops.

Now, her family often goes hungry, she said, and her children are stuck at home.

"It's not that we don't want to move. We can't afford it because of the lack of jobs," said Asha, who only gave her first name for security reasons.

- 'Lost everything' -

Burundi is one of the poorest countries in the world, ranked 187th out of 193 by the UN on its Human Development Index.

It is also one of the 20 countries most vulnerable to climate change, the UN says.

In 2024, torrential rains, exacerbated by the El Nino climate phenomenon, displaced nearly 100,000 people and claimed many lives, although no official toll has been given.

Ariella, a mother of seven now living in the Gateri camp in the north of the country, said she "lost everything" to a flood in Gatumba in 2020.

Her house collapsed and one of her babies was almost swept away by the floodwaters. She moved her family to two different camps -- only to be hit by flooding again.

The camp at Gateri is on high ground and further from the Ruzizi River, so she feels safer. But the land is poor and money scarce.

"We often wonder what our future will look like," she told AFP.

She refuses to return to Gatumba since the flooding has brought hippopotamuses and crocodiles to the streets.

- Cholera -

"Anarchic" construction since the colonial era has added to the problem, environment specialist Sindayihebura said, including in the capital where several roads and buildings are frequently submerged.

Sindayihebura said that a dyke could save Gatumba but it would take at least 10 years for the waters in the lake to recede enough to build it.

Locals tried to build one themselves last year, but it made little difference.

Save the Children, an international NGO, is appealing for funds to help those affected.

But the timing is bad: the administration of US President Donald Trump has suspended 83 percent of US humanitarian projects, with climate-related programmes among those most likely to be cut.

The United States accounted for 40 percent of global aid and no country has stepped in to fill the void.

In Gatumba, neighbourhood leader Jean-Marie Niyonkuru, 42, said locals were finding ways to survive, but it was tough.

"Children suffer from diarrhoea because the water has mixed with toilet water, flooding the streets," he said. "There is a lot of cholera."

jcp/jf/er/kjm

INDEX CORP.