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A guide named “Future” walks visitors through Nairobi’s Mukuru informal settlement. The journey takes them downhill from paved streets into villages marooned in foul water. While the flooding is often blamed on the river, researchers found that the drainage system is the primary failure point causing the crisis.

The Rubble Barrier

Mukuru kwa Reuben is a valley, as the name implies. Centuries ago, the land belonged to a settler named Reuben. After his departure in the 1970s, the land was subdivided to accommodate waves of people fleeing regional wars and moving from the countryside to the city.

By the early 2000s, zinc roofs covered the upper slopes, and people began building on the swampy soils by the riverside. Mud and mosquitoes were the main inconvenience at first, but as siltation from farms and construction sites upstream raised the river, it started spilling over during heavy rains.

“A lot of people have washed away over the years, I cannot count them,” says Francis Mukiri Muthoni, known as “Future”. In 2024, the government responded to criticism about wet-season drownings by demolishing tens of thousands of homes and creating a 30-meter buffer zone along the riverbanks. This has undoubtedly saved lives, but it has not solved the flooding problem.

The root cause lies in how residents and builders have tried to control the water. From around 2003, community leaders invited builders to dump rubble along the riverbank. They created a vast berm to prevent runoff from reaching the river directly. Now, when it rains, the water cannot flow away and instead builds up in low-lying villages.

The runoff picks up human waste as it goes, displacing sewage from hundreds of pit toilets. It is a complicated mess that has turned daily life into a series of battles with filth. “The industrial area above Mukuru makes it worse—the drains there are all clogged,” Muthoni explains.

The physical toll is visible. Susan Kambura, who has been flooded out countless times, has a routine she follows religiously. “First you sweep out faeces, then you wait for the water to subside, and then you come with soap and water,” she says.

John Mangi, wearing a Superman cap, describes the sudden nature of the danger. “Sometimes the floods ambush us at night,” he says. He once had to abandon his house by kicking out his own roof to escape rising waters.

A Measure of Trauma

Mental health professionals are increasingly concerned about the living conditions. Between 2021 and 2022, researchers with the African Population and Health Research Centre collected samples from water, soil, and food. They found traces of the DNA of cholera-causing bacteria in 97% of surface water samples and 77% of floodwater samples.

In 2025, the APHRC conducted surveys with more than 500 flood-exposed residents. Preliminary findings suggest that 44% showed signs of PTSD, such as nightmares and irritability. The stress level jumped to 51% for those who experienced five or more floods.

To understand the specific impact of this drainage, the team compared Mukuru with Manyatta, an informal settlement in Kisumu that floods far less often. Manyatta residents had a 30% rate of PTSD, compared to 44% in Mukuru. While the difference is significant, the numbers are still high.

The economic reality of the settlement ensures that these risks are internalized rather than mitigated. Rental prices in Mukuru often drop significantly when floods occur, sometimes slashing costs in half, which incentivizes landlords to keep tenants in hazardous areas. To rent a safer home in a higher district would cost five or six times more. This financial trap forces families to remain in morasses where they cannot afford to leave, effectively pricing them out of safety while the mental strain of constant displacement erodes their well-being.