Hi all, the Open Mapping Hub West and Northern Africa (part of Humanitarian OpenStreetMap Team (HOT) is responding to the flooding that occurred on 28 May in Mokwa, Nigeria. Officials have said that the floods killed more than 200 people and confirmed that 1,000 were missing. At least 121 others were injured, and the flooding destroyed 2,000 homes.
On June 3, 2025 the Western and Northern Africa Hub conducted a size-up (OSM needs assessment) of the disaster focusing in on a GDACS polygon. This found that Mokwa town was already very well mapped on OSM due to a successful Tasking Manager project 9417 from Médecins Sans Frontières (MSF) that completely intersects Mokwa Town. The project had used Maxar imagery captured in November 2020 - which was the latest available open imagery for improving OSM in that region at the time (via Bing/Esri). Thus, no immediate needs to improve OSM base map data in response to the disaster were identified.
On June 4, HOT created a custom Humanitarian Data Exchange (HDX) export to allow data users to easily download OSM data clipped to Mokwa Town. This will be available from HDX for at least six months.
On June 5, Maxar released a post-flood scene captured on 2 June under a Creative Commons Attribution Non Commercial 4.0 International following a request from HOT the day before. This scene was then added to OpenAerialMap.
On June 9, the Western and Northern Africa Hub spoke to a representative of Geohazards Risk Mapping Initiative who shared that for their longer term flood recovery efforts it would be valuable for damage tags to be added to building footprints using the post-flood Maxar imagery.
After consulting local organizations and locally based individuals a Tasking Manager project restricted to manually selected very experienced mappers has now been launched to coordinate this damage mapping. Please find the dedicated Wiki page for this response for more info and additional links: https://wiki.openstreetmap.org/wiki/Organised_Editing/Activities/Nigeria_Mokwa_Flood_Recovery_2025
Of key importance, the damage mapping approach will be as follows:
The boundary of this project is focused on UNOSATs flood extent data , derived from the post-flood Maxar scene, ensuring that mapping efforts are targeted to areas affected by the disaster.
The area has been well mapped already on OSM, so the goal here is to add relevant tags to existing OSM building footprints based on the latest damage.
On comparing the custom (post flood) imagery with mapped footprints and Esri World Imagery, if you spot damage or destruction please tag the relevant building footprint with:
*building=yes**damage=minimal*OR*damage=significant*OR*damage=complete*(based on * the * *BAR methodology*source:damage:date=2025-05**source:damage=Maxar Imagery*
Please pay special attention to any buildings that existed in OpenStreetMap (OSM) prior to the flood but that are no longer visible in the Maxar Imagery provided, they have a high likelihood of being destroyed or heavily damaged (i.e. damage=complete).
Do not delete any building footprints, even if they seem completely destroyed , the resulting data will be used for recovery and it is important to know what existed before the flood event (baseline data).
Please let us know if you have comments or questions about this mapping activity.
