Kenya: When Sewage Floods Your Home, It Floods Your Mind Too

In some of Kenya's informal settlements, the floods that wreck homes several times a year aren't always about raging rivers and violent storms. It's also about drains that don't work. Sean Christie travelled to find out what a lifetime of sewage through the front door does to the mind — and why the same pattern is playing out in places like Cape Town and Beira.

Your guide through Nairobi's informal settlement of Mukuru is a man everyone calls 'Future'. He walks you downhill, from paved streets and working toilets into villages where the stench of sewage overpowers the boiling tilapia and houses sit marooned in foul water.

Years ago Kenyan authorities bulldozed tens of thousands of riverside homes and cleared a buffer to stop drownings. But the further you go, you realise the river was only part of the problem. After the community invited builders to dump their rubble along the bank to create a barrier, water and sewage became trapped, flowing into the homes below and pooling in communities.

Researchers recently came to Mukuru to study river flooding and how it affected the mental health of those who lived there. "Instead they have made a study of our drainage," says Future. When they went looking for a settlement that didn't flood, to compare against, they couldn't find one.

Sean Christie travelled to find out what a lifetime of sewage through the front door does to the mind — and why the same pattern is playing out in places like Cape Town and Beira.

If you visit Mukuru kwa Reuben (Mukuru for short) on the southern edge of Nairobi, the guide you want is Francis Mukiri Muthoni, aka "Future", a man dedicated to realising a better future for his community, as he is quick to claim.

We meet at the assistant chief's office in the upper part of Mukuru, known pithily as the "highlands". Although devolution in 2013 transferred power and authority from the central government to 47 newly created county governments, informal settlements like Mukuru remain under the authority of a central government appointed chief and assistant chief, who rely on "elders" like Muthoni to carry information to and from "villages" within the settlement.

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"There has been some progress [in recent years]," says Muthoni, navigating down a street paved for the first time during COVID-19 lockdowns. The street was widened, too, and drainage channels were dug in. Today, some of the houses incorporate built toilets, connected to a so-called "simplified sewer system", comprising pipes that are bendy enough to go around corners in Mukuru's jumbled mass of housing.

As we head downhill, however, it becomes clear that some change isn't nearly enough for most.

Here in the "lowlands", in villages like Mombasa (because low-lying), the stench of sewage overpowers even the smell of boiling tilapia, known as ngege . The road — this one unpaved — is criss-crossed with rivulets of human waste, and towards the bottom of the road the houses have become enisled by foul water, accessible only on makeshift walkways of rocks and pallet wood.

How do you say cesspool in Kiswahili?

Bad drainage: A short history

Muthoni explains that the word "Mukuru" means valley, and is derived from the name of the birthplace of all Agikuyu people — Mukurwe wa Nyagathanga — a glade of fig trees where Gikuyu, the mythological patriarch, is supposed to have met his bride Mumbi.

The utopian shine had all but gone off Mukuru kwa Reuben by the time Muthoni's family arrived in the early 1990s, although he remembers one could still catch fish in the Ngong River at the bottom of the hill. The sloping land, which had been the property of a settler named "Reuben", was progressively sub-divided after his departure in the 1970s, to accommodate waves of people moving from the countryside to the city, as well as refugees fleeing regional wars.

By the early 2000s zinc roofs were interleaved like fish scales over the upper slopes, leading people to erect houses on the swampy soils by the riverside. For a time, their main inconvenience was mud and mosquitoes, but as siltation from farms and building sites upstream raised the river, it started spilling whenever it rained heavily in the distant Ngong Hills.

"A lot of people have washed away over the years, I cannot count them," says Muthoni.

From the lowest point of Mukuru the road rises slightly, and deposits us on the riverbank, which is clear of all structures in a band as wide as a double-lane highway. Children run amok, goats graze on refuse, but there are no houses.

Muthoni explains that in 2024, in response to building criticism over the number of wet-season drownings, Kenya's government demolished tens of thousands of homes and created a 30-metre buffer zone along the Nairobi, Ngong and Mathare Rivers.

The initiative has undoubtedly saved lives but it has done nothing to prevent flooding, and little to ameliorate suffering, and that's because the people of Mukuru, in seeking to control nature, have created a problem bigger even than the river.

From around 2003, community leaders invited builders to dump their rubble along the riverbank, creating a vast berm. When it rains, the berm prevents runoff from reaching the river, causing water to build up in low-lying villages.

"The industrial area above Mukuru makes it worse — the drains there are all clogged," Muthoni explains, adding that the runoff picks up human waste as it goes, displacing sewage from hundreds of pit toilets and septic tanks.

Everyone we speak to down here has a story.

Susan Kambura, after being flooded out of her home countless times, has a drill:

"First you sweep out faeces, then you wait for the water to subside, and then you come with soap and water," she says.

"Sometimes the floods ambush us at night," says John Mangi, in a Superman cap and a sleeveless jersey. He once had to leave his house by kicking out his own roof.

A few years back the Red Cross established an advance storm warning system in Mukuru, using SMS to alert community members of coming rains, but Mangi says not everyone has a phone, and even if they do, few are willing to abandon their homes and their possessions.

Faith Atieno, with the broad smile, lost everything in the big floods of 2024 .

"The worst was personal documents — having to apply for new ones," she says.

All have moved more than once, but not out of harm's way — they simply cannot afford to get to higher ground.

Teresia Wambui explains how the danger and unpleasantness of life in the flood-prone areas have been priced into the rental market.

"I pay 2 000 [shillings] (about R250) to live here. When it floods, the landlord drops the price to 1 000 (R125). To rent in a safer area, with my large family, I would pay 5 or 6 000 (between about R630 and R750). So we remain," she says.

Living in a morass comes with the usual physical consequences, chief among them an increased risk of waterborne diarrhoeal diseases like cholera and bloody diarrhoea (dysentery).

"It is impossible to keep the children out of the ponds. They are often sick," Atieno says.

Between 2021 and 2022 , researchers collected water, food, soil and other samples from places Mukuru children and adults come into contact with. In it, they found traces of the DNA (the genetic material found inside all living cells) of the bacteria that can cause cholera in 97% of surface water samples and 77% of floodwater samples. The DNA was everywhere in the water, but nothing grew in the lab — a sign the bacteria may be lying dormant, in a form that can still wake up and infect people.

It is the psychological impacts that come through most strongly in conversation with residents, however.

Mangi quietly admits he has felt like giving up at times, while Kambura describes a local atmosphere of fear and panic whenever heavy storm clouds appear, leading people to "rush about, raising beds on bricks and hanging our belongings high".

The link between poor mental health, sh*tty drainage

Studies conducted elsewhere , including in Africa , have linked floods to increased depression, anxiety and post-traumatic stress disorder, or PTSD, (long-lasting mental distress after trauma) but very little has been conducted in Kenya.

In 2025, seeking to address this gap, the African Population and Health Research Centre (APHRC) talked to more than 500 "flood-exposed" Mukuru residents. Preliminary findings suggest that 44% showed signs of PTSD, such as nightmares, hypervigilance and outbursts of anger and irritability, with the percentage rising to 51% among those who had experienced five or more floods. The number of people who showed signs of depression was quite high, too, at 24%.

Muthoni believes there are many contributors to trauma in Mukuru, from high levels of sexual and gender-based violence to deadly fires, but he is convinced that Mukuru's particular hydrological dynamics — the way that toxic runoff serially inundates low-lying villages — is the biggest contributor.

"They [APHRC] came to make a study of river flooding, and instead they have made a study of our drainage!" says Muthoni.

It is a joke, but the idea that the APHRC's study results could be a proxy for the psychological toll of poor drainage is compelling. While several studies have shown that flooding can harm people's mental health, Bhekisisa found almost no research looking specifically at the psychological toll of living with chronically poor drainage.

In 2026, blocked drains caused the informal settlement of Dunoon in Cape Town to flood several times, and the same thing happened in parts of Khayelitsha, Philippi and Masiphumelele. Beira in Mozambique is known for being vulnerable to cyclones, but it is the annual flooding of city streets due to poor drainage that is most oppressive, requiring residents to build their homes differently, with most doorways raised a metre above the ground. Kenya arguably has the worst of it, with an estimated 60% of the population living in informal settlements or slums , most of which suffer from poor to non-existent drainage.

When I put this to APHRC research officer Henry Owoko, he nods vigorously.

"Pick any urban informal settlement in Nairobi — Viwandani, Dandora, Kibera, Soweto-Kayole — and you will find there is usually an industrial area nearby, which has a clogged drainage system, and the land slopes down to either the Nairobi River or one of its tributaries, and all through you find people struggling with flooding, either as a result of the river breaking its banks, or poor drainage, or both," Owoko explains.

To strengthen the inference that flooding is a cause of poor mental health in Mukuru, the APHRC team planned to talk with the same number of people in a community that is not exposed to flooding, but has similar income and living conditions.

The research forms part of a four-country study in South Africa, Kenya, Burkina Faso and Mozambique that looks at the mental health impact of increased flooding caused by climate change.

"That's when we realised how common the experience of flooding in informal settlements is," Owoko says.

"We visited Mombasa on the coast but found most people there have experienced flooding, too, much of it the result of collapsed drainage systems, with extreme heat as a confounding factor. We then went to Kisumu, and what did we find? Floods!"

The team eventually settled on Manyatta, an informal settlement in Kisumu set some distance back from rivers on sandy, quick-draining soils. Five hundred residents submitted to the same survey conducted in Mukuru, and the results were interesting.

The number of people showing signs of moderate mental health problems such as trauma, depression and anxiety was lower than Mukuru, with 30% of people showing signs of PTSD in Manyatta compared to 44% in Mukuru, and 19% being symptomatic of depression compared to Mukuru's 26%, suggesting Mukuru's floods added measurable levels of extra stress and trauma to people's lives.

Still, even the rate of PTSD and depression in Manyatta, the control site, remains incredibly high.

When those rates are compared with the levels of depression and PTSD in some conflict-exposed regions, as estimated in a 2020 analysis of 25 studies conducted in sub-Saharan Africa, Manyatta's PTSD levels are on par with conflict-ridden places and Mukuru's 15 percentage points higher.

On a trip to Kisumu, which hugs the shoreline of Lake Victoria, I took a short walk around Manyatta with APHRC researcher Tedy Ouma, and it quickly became apparent that here, too, poor drainage is a major quality of life issue, one that may account for its high rates of psychological suffering.

"People here might not experience natural floods, but water is still a major problem," says Ouma, leading past a large pile of refuse on the side of the street in a part of Manyatta called Lower Gonda.

A woman nearby tut-tuts and says the county occasionally takes waste away, if it is dropped here, but most people chuck their rubbish in the stormwater drains on the side of the street.

"Diapers are a major problem. When it rains they block the drains, and the water spills into our houses," she says.

We find Judith Otieno in Lower Flamingo, sluicing water into a drain that has become overgrown with weeds ("the drains receive a lot of human fertiliser," Ouma jokes). She says two structures on her property have been undermined by flash floods, but she is too poor to leave. The biggest problem, she explains, is the multi-storey buildings that are springing up everywhere. In the absence of sewer lines the buildings, known as gorofas , are simply plumbed into pits, which are deliberately opened when it rains so that the sewage can flow downhill. Livestock owners in Manyatta do a similar thing.

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"When it rains, they come to their sheds with spades," Otieno says.

New drains are being constructed along our route, in an area called Kosawo.

"Are you alright?" Ouma asks one of the workers.

"No, I'm all left," comes the response. Kisumu is the heartland of the Luo people, one of the largest ethnic groups in Kenya, and Luos, Ouma explains, love a joke.

New drains will help but a nearby motorbike taxi rider, after a shouted greeting of " Ber! ", explains that property owners with drain frontage charge their neighbours for the maintenance of their section of the drain, knowing that if it blocks, all the properties around the blockage will flood.

"Sometimes they block the drain on purpose," he says.

A man reaches into the drain with a rod, at the end of which a halved section of PVC piping has been horizontally attached. It is exactly the width of a small plastic bottle, and when he lifts his rod there is an empty bottle attached. He adds it to a sack of bottles, which he will later sell at two shillings (about 25c) a piece to a woman living in a so-called kona mbaya (bad corner) near Bypass Highway. She will scrub the bottles and sell them on to shopkeepers for use, for five shillings (about 65c).

In a community like Manyatta, where residents face so many hardships, there is surely a risk of overstating poor drainage and sanitation as factors in people's poor mental health. And yet, when I meet James Bosse, a psychologist working for the Kisumu county government who also volunteers for local disaster response structures, he immediately insists that the impact of water on people's lives should not be minimised.

"In the dry season it is mainly women who come in, depressed and anxious because they are having to walk 20 minutes each way to fetch water, and maybe the quality of that water is questionable anyway because our boreholes haven't been sealed against contamination, and they get home and a child knocks it over, and they must go back. In the rainy season it is the men, because they are the ones repairing the houses that are damaged by flooding," says Bosse, recalling how, on his way back home recently, he looked across at a familiar house and was surprised to see inside.

"The wall had collapsed. Everybody inside was standing on top of tables and chairs, and you could clearly see the clogged waterway that had caused the flood that had undermined their wall."

Bosse called the Red Cross, and stayed on to do some psychological first aid with the family.

"I knew if I did not, I would soon see them in my rooms, complaining of depression," he says, "complaining of anxiety every time it rains."

This story is part of a series of articles about the impact of climate change on mental health. Read the first , second , third , fourth , fifth and sixth . Also view our Health Beat TV programme on the mental health impact of floods in KwaZulu-Natal. Bhekisisa is a collaborator on a Wellcome Trust-funded project, which the Africa Health Research Institute at the University of KwaZulu-Natal is leading. Bhekisisa, however, operates editorially independent of the project.