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 | NASA GPM IMERG Final Run | 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 is powered by NASA GPM IMERG Final Run — actual satellite-observed monthly precipitation bias-corrected against ground gauges — replacing the climatological averages used in earlier versions. This makes risk scores responsive to real rainfall conditions rather than historical means.
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.