What’s Nairobi’s drainage got to do with health?

The rains have been pounding the city relentlessly in the last few weeks. Good things have happened, clouds of dust have disappeared and the city lawns are all green and beautiful. But other untoward things have also happened; the already chaotic city life has worsened with flooding and traffic snarls. And the risk of disease has increased.

Why the increased risk of disease when it rains? Simple stuff, a sustained heavy downpour quickly saturates the ground and runs off paved streets. Urban health problems increase if excess water has nowhere to go. Such excess water may feed into and overflow sewer systems, or find its way into domestic water supplies. Drainage channels come in handy, but do they actually exist in Nairobi? City drainage systems are designed to drain excess rain and ground water from paved streets, parking lots, sidewalks and roofs. Street gutters should carry the untreated water into reservoirs, dry holding wells or straight into canals and rivers. Alternatively, combined sewer systems can drain both sanitary sewage and excess surface water, albeit at the risk of overflowing sewer lines.

Looking around Nairobi currently, you are bound to encounter lots of standing water. Standing water is a breeding ground for mosquitoes and other waterborne disease vectors, all waiting for an opportunity to inflict disease into Nairobians. Diarrhoea and vomiting diseases, especially in children, tend to increase if domestic water supplies get contaminated. This may be caused by overflowing and blocked sewer lines, with disease causing micro-organisms finding their way through bathing, domestic washing, food preparation or simply drinking infested water. The dirty urban surface water contains many pollutants that include gasoline waste, motor oil, heavy metals and, pesticides and fertilizers from garden lawns. All these can cause disease if they get into contact with humans one way or the other.

There is also the physical risk of drowning in flooded neighbourhoods. Poorly constructed houses in the paths of fast flowing waters have been known to collapse, leaving the occupants either homeless or at worst dead.

Nairobi has to do better before we all get swallowed by raging heavy rains. Our existing drainage systems must be continuously maintained if they are to serve their intended purpose. Nairobians must take responsibility too, there is too much plastic waste dumped into drain inlets by the city residents. This must stop. NEMA must do its work too by regulating storm waste management through residential, commercial and road building codes that cater for better drainage. Nairobi city may wish to invest in sustainable modern drainage systems that separate undesired run-off from the water, so called oil-grit separators (OGS), as attempts are made to improve the city’s drainage system. It may seem far-fetched, but the better the city’s drainage systems, the better the health for Nairobians.