On a rainy evening in March last year, Nairobi's South B estate turned into a lake. Residents waded through waist-high water, struggling to salvage what they could as vehicles floated like abandoned boats.
The culprit? A section of the Ngong River that had been blocked by newly constructed buildings, preventing its natural flow. What should have been a manageable downpour turned into a full-scale disaster, displacing families and destroying businesses overnight.