Methodology · Sea Rise Insight
How inundation is mapped
Sea Rise Insight compares projected water levels with a 30 m elevation model to show which parts of the West African coast, from Senegal to Nigeria, a rising sea would flood.
scenarios
elevation data resolution
Under review: the Centre for Coastal Management is checking the scenario values and the method behind this layer, so some of this page may change.
Data
The main dataset is the 30-meter resolution Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM), downloaded via Google Earth Engine. It was preprocessed in ArcGIS Pro V3.5 to correct voids, fill sinks and remove anomalies in flat terrain.
Only terrain below 3 metres elevation was analysed.
The result is a grid layer with one field for each sea-level rise scenario, modelled in ArcGIS Pro, loaded into the ROC database and served by the ROC Datahub API.
The map supports layer toggling, scenario switching, zoom and pan, and pop-up information windows.
Scenarios
Sea-level rise was simulated with a modified bathtub method: the projected increments come from global climate projections, including the IPCC Sixth Assessment Report (AR6). Each field in the layer holds one scenario.
- SLR_1m
- +1.0 m
- SLR_2m
- +2.0 m
- SLR_3m
- +3.0 m
How a cell is classed
Inundation was mapped by subtracting the DEM from each water surface: where the water level exceeds the ground, the cell is marked as potentially inundated. A cell is then classed by the first scenario that floods it.
Only hydrologically connected zones, those continuously linked to the ocean or tidal systems, are counted as inundated. This was checked with the Region Group function in ArcGIS Pro.
Limitations
Low-lying depressions larger than one acre that are not connected to the ocean were kept but symbolized separately, to avoid overestimating risk. Inundation depths were also mapped for each scenario, and a land-water mask limits the visual output to terrestrial areas.
A bathtub model ignores waves, storm surge, tides and coastal defences, so it shows exposure to sea-level rise rather than a forecast of flooding.
Source
The layer was produced by the Centre for Coastal Management, University of Cape Coast, the contact for questions about it. A formal citation will be added once it is confirmed.