GIS Specialist Mohamed Mohamud Omar has warned that Nairobi’s persistent flooding is largely the result of poor urban planning and weak implementation of expert advice.
In a Radio Generation interview on Monday, he said increasing rainfall intensity combined with outdated drainage infrastructure and development on wetlands, has left the city vulnerable urging authorities to prioritise disaster preparedness. and data-driven urban planning.
He said Kenya has sufficient technical expertise to manage urban development but the main challenge lies in implementing recommendations provided by experts.
“We have amazing engineers, urban planners and GIS analysts,” Omar said. “In terms of capacity, we are very okay, but the problem is on the implementation side.”
According to him, many studies conducted by urban planners and environmental experts are often meant to guide decisions at the leadership level but are sometimes not acted upon.
The comments come after heavy rainfall triggered flooding in several areas of Nairobi, including sections around Chiromo, where roads were submerged, disrupting traffic and damaging property.
Omar said the intensity of rainfall recorded during the storm was significantly higher than in previous years.
“In some places rainfall reached about 120 millimetres,” he said. “When you have that level of rainfall, it exposes the structural deficit that the city has.”
He explained that while rainfall may trigger flooding, the scale of damage is often worsened by outdated drainage systems and rapid urban expansion.
Many of Nairobi’s drainage systems were originally designed decades ago when buildings were much smaller and population density was lower.
“Some of the drainage systems were built for four or five-storey buildings, not the kind of high-rise developments we have today,” Omar said.
As new developments continue to expand across the city, runoff water from buildings and paved surfaces moves faster into drainage systems, overwhelming existing infrastructure.
Urban growth has also increased the amount of impervious surfaces such as asphalt, concrete and paving blocks that prevent rainwater from soaking into the ground.
“When rain falls on these surfaces it has nowhere to go,” Omar said. “It flows quickly into the drainage system and eventually causes flooding.”
The GIS expert also highlighted the impact of uncontrolled land use and construction in environmentally sensitive areas such as wetlands and riparian zones.
Wetlands naturally absorb excess water and act as flood buffers, but many have been converted into residential or commercial developments.
“These wetlands are natural flood barriers,” Omar explained. “When we build on them we remove the natural systems that absorb water.”
He pointed to international examples where cities have adopted nature-based solutions to reduce flood risks.
In some Chinese cities, urban planners have introduced the concept of “sponge cities”, where parks, artificial wetlands and green spaces are integrated into urban design to absorb rainfall and reduce flooding.
“These areas act like a sponge,” he said. “They allow water to seep into the ground instead of overwhelming drainage systems.”
He also emphasised the importance of early warning systems and disaster preparedness.
Many cities around the world install sensors in upstream river catchments to monitor water levels and provide advance warnings when floods are likely.
When water levels exceed a certain threshold, authorities can alert residents downstream through mobile phone messages or emergency alerts.
“With these systems you can warn people hours before the flooding reaches them,” he said.
He added that Kenya currently focuses more on disaster response and recovery rather than prevention and preparedness.
“In many cases the government becomes active after the disaster happens,” he said. “But what other cities do is invest heavily in prevention, mitigation and preparedness.”
Omar said Kenya could significantly reduce flood risks by upgrading storm water drainage systems, enforcing zoning laws and reclaiming encroached riparian land.
He also urged property buyers and developers to conduct proper due diligence before investing in land, including consulting environmental experts to assess flood risks.
“Land is a major investment,” he said. “You have to understand the topography and environmental risks before building.”
Without stronger planning and enforcement, he warned, flooding could become more frequent as rainfall intensity continues to rise due to climate change.
