Written by Lucy Kago
Location: South C, Nairobi, Kenya
Project: Nairobi Drainage Map and Clean
Tools: KoboCollect · ChatMap
Organizations: UN Mappers Kenya · Young Lawyers Voice on Climate Change Foundation (YLVOCCF)
Background
Nairobi has long struggled with flooding linked to blocked and poorly maintained drainage infrastructure , a problem that hits informal and peri-urban neighbourhoods hardest every rainy season. In April 2026, UN Mappers Kenya partnered with the the Young Lawyers Voice on Climate Change Foundation (YLVOCCF) to turn that problem into a mapping opportunity: collect structured, geolocated drainage data on the ground in South C, one of the areas most regularly affected by flooding.
The initiative ran over two days , a training day on 17 April and a full field deployment on 18 April.
Day 1 — Training (17 April)
The weekend started indoors. Sixteen participants gathered for a hands-on session running from 2:00 pm to 4:00 pm, led by Lucy Kago, UN Mappers Ambassador for Kenya.
The session covered the two primary data collection tools for the project: ChatMap and KoboToolbox/KoboCollect.
The group was a mix, 12 geospatial science students and 4 lawyers from the Young Lawyers Voice on Climate Change Foundation — which made for an interesting dynamic. Legal and technical minds working through the same workflows, asking different but equally sharp questions. What stood out was how quickly everyone got comfortable with the tools and, more importantly, understood why the data fields mattered — what "drainage condition" or "flood risk observation" would actually mean for someone using that data later to make decisions.
The training was facilitated by the Geospatial Sciences Students Association, with thanks to Patron Pamela Ochungo, PhD, MISK for supporting the session and ensuring everything was in place.
By the end of Friday, the team was ready. All participants received certifications recognizing their training in field data collection for urban drainage mapping.
Day 2 — Field Mapping (18 April, 2026)
18 April was the real test. Sixteen mappers fanned out across South C with a clear brief: locate, assess, and document drainage features — culverts, open channels, road-side drains — and record their condition, blockage causes, and associated flood risk.
The team split into two groups of eight:
- 8 mappers working with ChatMap
- 8 mappers working with KoboCollect
Both tools fed data into the same survey form, covering six key variables per drainage point: feature type, physical condition, flood risk level, primary blockage cause, nearby land use, and GPS-tagged photos and video.
The areas covered included Popo Road, 5 Star Road, Red Cross Road, and surrounding streets and culverts — hotspots for drainage failure during heavy rains.
What the data shows
By day's end, the team had submitted 110 geolocated drainage records, captured by 12 enumerators across four field teams. A quick read of the data:
- Drainage condition: 72 of 110 features (~65%) were recorded in poor condition; 27 moderate; only 11 in good condition.
- Flood risk: 69 points rated high flood risk; 38 medium; 3 low.
- Main blockage cause: Solid waste was the dominant cause (55 entries), followed by sediment buildup (42), with structural issues accounting for the remaining 13.
Feature types recorded: Open channels were the most common (47), followed by covered drains (32), culverts (25), and inlets/outlets (5+).
These numbers tell a familiar story for Nairobi — drainage infrastructure is largely present but overwhelmingly blocked, mostly by waste, and the flood risk is high across the board. That's exactly the kind of structured, location-specific evidence that's hard to argue with in urban planning conversations.
All data points are available for visualisation on uMap: https://umap.hotosm.org/en/map/south-c-nairobi-drainage_2616
Collaboration
This wasn't a solo effort. Merging the UN Mappers drainage mapping initiative with the Young Lawyers Voice on Climate Change Foundation's concurrent drainage clean-up campaign on the same day, in the same area, meant the data collection happened alongside active community intervention — mappers were recording and doing the clean-up in real time. That kind of alignment between documentation and action doesn't happen often, and it made the day more grounded.
Reflections
South C is not the last area that needs this kind of attention. Across Nairobi, drainage data is patchy, outdated, or simply missing. What this weekend showed is that with a bit of coordination, the right tools, and people who are genuinely invested — students, lawyers, community members — it's possible to generate meaningful, usable data fast.
The mappers who showed up on 18 April , rain risk and all ,did real work. The data is on the map. The next step is making sure it reaches the people who can act on it.
Team: Felix Kipleting · Joseph Mjumbi · Collins Omwando · Michael Kioko · Wandera Joseph · Brandon Mwangi · Lucy Kago · Alister Mutugi · Eric Mutunga · and the full 16-person South C field team.