Intense rainfall during Kenya’s long‑rains season often triggers flash floods, with Nairobi regularly among the hardest‑hit areas.

Rapid surface runoff overwhelms the city’s undersized drainage, causing the Nairobi and Ngong rivers to breach their banks and flood homes and infrastructure.

Nairobi sits on a floodplain crossed by several rivers and streams, a geography that makes it naturally prone to flooding, especially when high‑intensity storms hit impermeable surfaces.

The city’s vulnerability has risen as its population grew from about 100,000 a century ago to over 4.5 million today, outpacing upgrades to drainage, sewage and waste‑management systems.

Recent floods this year affected neighbourhoods such as Parklands and the Central Business District, with the Nairobi River bursting its banks and displacing residents.

Assessments linked the severity of those floods to poor drainage and blocked waterways, especially where unregulated development has encroached on riverbanks and wetlands.

Conversely, low‑lying areas equipped with proper flood‑prevention infrastructure avoided inundation, highlighting the importance of targeted engineering measures.

Governor Johnson Sakaja has urged residents to join neighbourhood clean‑up drives as the county steps up preparations for the expected El Niño rains.

About 4,500 Green Army volunteers have been deployed across Nairobi’s 17 sub‑counties to clear waste, maintain drainage channels and improve public spaces as part of a broader road‑and‑drainage programme.

The Kenya Defence Forces are also bolstering emergency medical capacity to support national response efforts should local health services become strained.

The Kenya Meteorological Department forecasts El Niño conditions and above‑average rainfall nationwide, while a national assessment rates overall flood preparedness at 54 percent and identifies 18 counties and 5,660 health facilities as at‑risk.