Nairobi maps 246 flood hotspots as El Nino rains threaten 100, 000 residents

Expansion of Nairobi drainage on September 2, 2026. Sixteen high-risk flood zones have been identified across Nairobi requiring drainage clearance ahead of the El Nino rains. [Edward Kiplimo, Standard]

Nairobi County has identified 246 flood hotspots across the city as El Nino rains approach, with up to 100, 000 people at risk of being severely affected by flooding.

The hotspots, mapped and geocoded are concentrated in several parts of the city, with Roysambu, Ruaraka and Embakasi South recording the highest number of mapped locations.

Out of the 246 hotspots, 39 were mapped in Roysambu, 33 hotspots in Ruaraka while Embakasi was found to have at least 20 floods points.

Other areas with relatively high mapped points are Embakasi North (18), Dagoretti South (15), Starehe (14) and Makadara (12).

Other hotspots were mapped in Wetlands (10), Kibra (9), Embakasi East (8), Embakasi Central (7), Lang’ata (6), Kamukunji (5) and Dagoretti North (5).

Although the city’s Southern corridors have fewer hosts, the inter-agency team overseeing El Niño preparedness in Nairobi City County anticipate that the rea could have higher displacement potential, hence ranked high-priority.

In a joint response plan, the interagency team is preparing for the possibility of widespread displacement, flash floods and riverine flooding, infrastructure collapse, disruption of transport and road access, disease outbreaks, household displacement and damage to schools and health facilities and the simultaneous activation of multiple evacuation centres.

“The northern belt- Roysambu, Ruaraka, Kasarani, Embakasi North, carries the largest number of mapped points. The southern corridors carry fewer points but have higher displacement potential,” reads the report.

Nairobi’s exposure to flooding is heightened by rapid and largely unplanned urbanisation, inadequate storm-water drainage and the encroachment of settlements and developments onto waterways and riparian reserves.

The city’s drainage systems are frequently overwhelmed or blocked, leaving many areas vulnerable when heavy rains fall.

The risk is particularly high in densely populated informal settlements, with much of the exposure concentrated along the Nairobi, Ngong and Mathare rivers and their tributaries.

Although 246 locations have been mapped, the number of points in a particular sub-county should not automatically be interpreted as the level of risk.

“The mapping records the location of hotspots, rather than their severity, frequency or the number of people who could be affected.”

To further narrow down the risks, The Standard established that the inter-agency team ranked 16 priority risk areas based on exposure, probability of displacements and the severity of compounding hazards such as drainage failure, structural collapse, contamination and dam overflow so as to help the response teams know the kit and tactic each cluster needs.

The Mukuru and industrial corridor ranks highest, covering Mukuru Kwa Njenga, Mukuru Kwa Reuben, Viwandani, Kware, Pipeline and Imara Daima. The corridor has an estimated exposure of more than 40,000 residents with river flooding, drainage blockage and settlement congestion listed as top priority risks.

The Dagoretti-Kawangware corridor follows, with Gatina, Kawangware and Waruku facing risks associated with river overflow, drainage failure and road inaccessibility. Gatina is among the county’s most exposed corridors.

Residents living in Nairobi Dam Catchment, Laini Saba, Makina, Sarang’ombe, Mugumoini areas under the Nairobi Dam catchment and Kibra cluster are likely to be affected by Nairobi Dam overflow and poor drainage conditions.

These areas downstream and surrounding the dam could face severe safety, health, and structural risks if the water levels rise dangerously high and threaten to overflow or break the dam.

The city’s Northern and Eastern river corridor where Mathare and Dandora are clustered, the top priority risks are river overflow, floodwater contamination with the team foreseeing possibilities of structural collapses.

These areas are also expected to have the highest risk of secondary health emergencies such as waterborne and vector-borne diseases outbreaks.

The response team is paying particular attention to the Nairobi, Ngong and Mathare rivers and their tributaries since because communities and infrastructure along these corridors can be severely affected when water levels rise.

The stakes are high because Nairobi is Kenya’s administrative, economic, industrial, transport and diplomatic centre, with the country’s largest concentration of critical infrastructure.

Heavy October-November-December (OND) rains could therefore have far-reaching consequences, including flash and riverine floods, damage to infrastructure, disruption of road access, disease outbreaks and displacement of households. Schools and health facilities could also be affected.

Nairobi has 17 sub-counties and had more than 4.4 million residents in the 2019 census, a population that is now estimated to have surpassed five million.

In anticipation of the rains, an inter-agency committee has developed three scenarios to guide preparedness.

The best-case scenario envisages about 5,000 people, or 1,000 households, being affected. Under the moderate scenario, the number rises to 25,000 people, or 5,000 households.

The worst-case scenario puts the number at 100,000 people, equivalent to about 20,000 households.

However, the team indicates that the 100,000 figure is a planning assumption rather than a prediction of what will happen.

Authorities are using the worst-case scenario as the basis for determining how much emergency capacity is needed, including the pre-positioning of supplies, deployment of personnel and planning for evacuations.

 Shelter capacity is also being planned around the possibility of up to 20,000 households being displaced, alongside widespread transport disruption, disease outbreaks and the need for multiple evacuation centres.

As part of the preparedness measures, authorities have mapped and geocoded 246 flood hotspots out of approximately 260 locations identified across the county.

The hotspot map will be used to guide early-warning messages, determine where rescue teams and equipment should be deployed, identify potential evacuation and shelter sites, and inform daily situation reports from the Emergency Operations Centre.

The mapping is intended to give emergency responders a clearer picture of where flooding is most likely to cause harm, allowing them to position resources before heavy rains turn into a crisis.

A multi-agency team established specifically to coordinate Nairobi’s preparedness, separate from the national multi-agency team, has also identified 172 holding and evacuation sites across the county including churches, social halls, schools, mosques, community centres, stadia and open grounds.

Among the areas identified as holding and evacuation sites, there are 15 strategic evacuation centers identified from the larger pool.

“These are mapped locations, not yet a fully confirmed shelter network. The sites still need physical verification to establish whether they are accessible, secure and capable of accommodating displaced residents.”

They include Gatina Primary School, Gatina Social Hall, Kawangware Primary School, Mukuru Community Centre, Mukuru Promotion Centre, Kayole South Secondary School, Dandora Stadium, Olympic Primary School, Joseph Kangethe Primary School, Kariobangi North Primary School, Kwa Njenga Primary School, PCEA Kahawa West, Kamulu Grounds, Maji Mazuri Grounds and the East African School of Aviation.

“The first five are the corridors carrying the highest displacement potential but the capacity has to be verified in sequence,” reads the report.

The selection was based on factors including elevation, road accessibility, water availability, latrine capacity, security, space per person and disability access.

Some parts of the city have a relatively high concentration of mapped holding sites, while others have thinner coverage.

For instance, Lang’ata, Embakasi East, Ruaraka, Roysambu and Dagoretti North have comparatively fewer mapped sites.

“Mukuru, Kibra, Mathare and Dandora need verified sites within walking distance, with a named manager and an agreed access route. Where hotspot density is high and mapped sites are few, pre-agree alternative premises and county transport before the rains begin,” reads the report.

“Stocks should sit inside the high-risk sub-counties before onset, not in a central store,” reads the plan.

However, the preparedness plan indicates that mapping of flood hotspot or identifying evacuation centres does not necessarily mean that the location is ready for an emergency.

The 172 sites are only potential holding sites whose capacity, physical condition and suitability have yet to be fully verified.

With only weeks remaining before the expected onset, authorities are expected to swift into action and move people, equipment and supplies quickly before floods strike.

The response plan brings together the county’s emergency services and the Kenya Red Cross under a common command structure.

Nairobi County has listed fire engines, rescue trucks, ambulances, administrative vehicles, water bowsers, front-end loaders, excavators, lighting towers, mobile generators, portable pumps and rescue ropes among the equipment available for emergencies.

The Kenya Red Cross has inflatable rescue boats and rafts, life jackets, tarpaulins, family tents, 3,000 shelter kits, blankets, water purification units, radio communication systems, emergency medical kits, megaphones and camp-management kits.

The plan also provides for a surge capacity of 200 trained volunteers who can be deployed during major flood emergencies.

The plan identifies Mukuru, Kibra, Mathare, Dandora and Ruai as priority deployment areas for search and rescue.

County fire and rescue teams would provide fire engines, rescue trucks, pumps, lighting towers and heavy equipment, while Kenya Red Cross rescue teams would provide boats, rafts, life jackets and emergency medical support.

The National Police Service would assist with access control, crowd management, security and evacuation routes, while the Kenya Defence Forces could be deployed upon request for large-scale or technically demanding operations.

The county’s preparedness plan proposes a five-level activation system, beginning with routine monitoring and escalating through enhanced preparedness, partial activation, full activation and major emergency activation through a single Emergency Operations Centre message.

At full operation, the EOC is expected to run around the clock through three eight-hour shifts from 6am to 2pm, 2pm to 10pm and 10pm to 6am to ensure that emergency coordination does not stop when the working day ends.

The EOC will handle operational command, forecasting, mapping, logistics, public information and situation reporting, while the City Hall Crisis Management Centre will provide strategic leadership and executive decision-making.

The proposed system would also require situation reports to reach the City Hall Crisis Centre every six hours.

Although the planning window is October to December, the county’s briefing says preparedness should effectively extend into January. That has implications for staffing, emergency stocks, shelter arrangements and volunteer deployment.

Between September and the onset in the first weeks of October, the joint team will be carrying out validation and prepositioning activities and conducting joint simulations to test effectiveness of the plan.