Methodology · Coastal Risk Atlas
How the flood extent is mapped
The Atlas shows which 1 km grid cells flood under three sea-level-rise scenarios: +1 m, +2 m and +3 m. In each scenario a cell is either flooded or not flooded.
grid cell
elevation limit
Spatial framework
The Atlas uses a standardised grid of 1 km × 1 km cells — fine enough to show local detail, coarse enough to compare across the region. Analysis is limited to land below the 30 m elevation contour, the zone most likely to flood.
Flood-extent scenarios
Each cell carries one flag per scenario: 1 where the model floods the cell at that rise, 0 where it stays dry. The map draws the flag of the scenario you choose. It does not combine the scenarios or score them.
- +1 m
- Cells the model floods when the sea rises by 1 m.
- +2 m
- Cells the model floods when the sea rises by 2 m.
- +3 m
- Cells the model floods when the sea rises by 3 m.
Scenario values and method are under review by the Centre for Coastal Management. A vulnerability component is planned once socioeconomic data is available.
Technical implementation
The three scenario layers were modelled in ArcGIS Pro, loaded into the ROC database and are served by the ROC Datahub API. Click any grid cell to see whether the chosen scenario floods it.
Model validation
Model outputs were checked against observed coastal impacts — floods, shoreline retreat and community displacement. Where ground-truth data exist, such as the Lower Volta feasibility study, the flooded zones match places that have suffered significant coastal flooding.