Methodology · Coastal Risk Atlas
How coastal risk is determined
Following the IPCC risk framework, the Atlas treats coastal risk as the interaction of three components: hazard, exposure and vulnerability. Each is scored on a 1 km grid below the 30 m elevation contour.
grid cell
elevation limit
Spatial framework
The Atlas uses a standardised grid of 1 km × 1 km cells — fine enough to show local risk, coarse enough to compare across the region. Analysis is limited to land below the 30 m elevation contour, the zone most exposed to flooding and erosion.
Data sources
Each component of risk draws on open geospatial datasets, processed to a common resolution and projection.
Hazard
Taken from two ROC tools: Sea Rise Insight, which simulates inundation under projected sea-level rise, and EroTrack, which tracks shoreline change and erosion along the West African coast.
Exposure
The people and ecosystems inside hazard-prone areas: gridded population density from WorldPop, and land cover — including mangroves and wetlands — from ESA WorldCover.
Vulnerability
Socioeconomic indicators such as income, education and housing quality, plus dependence on fisheries and access to early warning, disaster response and health services.
Risk score
Every indicator is normalised to a 0–1 range. Weighted indicators are combined into a hazard, an exposure and a vulnerability index for each cell, and those three give the composite score.
- Coastal risk score
- R = H × (E + V) / 2
- H · Hazard index
- Sea-level rise inundation, shoreline erosion
- E · Exposure index
- Population density, land cover, critical ecosystems
- V · Vulnerability index
- Income, education, housing, fisheries dependence, services
- Scale
- 0.00 – 1.00 · low / medium / high
Technical implementation
The hazard, exposure, vulnerability and composite layers are published from ArcGIS Pro as feature services, each on its own API endpoint, and drawn in the ROC website with Esri Leaflet. Users can switch between layers and click any grid cell to see its contributing indicators.
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 high-risk zones match places that have suffered significant coastal hazards.