FloodWatch Ghana is an open source flood risk intelligence system for Greater Accra. In its v0.1 "raw" state, it provides a high-resolution, static baseline of structural flood vulnerability. This methodology is optimized for long-term urban planning, infrastructure assessment, and city-wide resilience strategy.
The score reflects chronic structural vulnerability - areas that are low-lying, poorly drained, and near water bodies. This static baseline acts as a foundation for long-term planning, identifying where the city's infrastructure is most at risk regardless of individual weather events.
| Data layer | Source | Weight |
|---|---|---|
| Elevation (DEM) | NASA SRTM | 30% |
| Precipitation | CHIRPS v2.0 Monthly Climatology | 25% |
| Terrain slope | Derived from SRTM | 20% |
| Land cover | ESA WorldCover 2021 | 15% |
| Water proximity | OpenStreetMap | 10% |
FloodWatch v0.1 was validated against the May 18, 2025 Greater Accra flood event (132mm rainfall, 4 deaths, 3,000+ displaced). Quantitative results across all 29 districts:
Rainfall uses CHIRPS v2.0 monthly climatology — a smooth spatial surface representing chronic rainfall patterns across the region. This is the correct input for a structural vulnerability model. NASA GPM IMERG (actual observed data) is reserved for the v1.1 dynamic event layer where single-event rainfall belongs.
As a static structural model, it identifies chronic vulnerability — areas that are low-lying, poorly drained, and exposed. Event-specific flash flood dynamics (drainage overload, extreme single-day rainfall) are planned for v1.1 as a dynamic risk layer.
Click any district to see detailed risk statistics. Use the layer controls (top left) to toggle layers and adjust opacity. The map updates monthly as new rainfall data becomes available.
FloodWatch Ghana is an open source initiative by GeoBuilders Africa, founded by Rachel Atia, a Geospatial Data Engineer based in Accra, Ghana.