Section E
Lagos floods because we build where water used to go
What estate developers can do before the first block goes up, from levels to culverts to the forgotten outfall.
By Folake Adewunmi, water lead · Yaba, Lagos
Start with levels
Many estates are laid out on paper without a levels survey. Water then decides where the low point is, usually someone’s living room.
Size for the storm, not the average
Lagos regularly sees more than 100 mm of rain in a day. Drains sized for a typical shower overflow in the first July storm.
The outfall is the whole game
A beautiful drain that empties into a blocked channel does nothing. We trace every drain to where the water finally goes.
Leave room for water
Retention ponds, permeable paving and green verges hold water back and cost less than bigger pipes.
Maintain it
Most estate floods we investigate start with a blocked drain. A cleaning plan before the rains is the cheapest flood defence there is.
