# Accra Flood Susceptibility Mapping
Accra has been dealing with flooding for decades. Every rainy season,
the same low-lying neighbourhoods go under — Korle Lagoon, the Odaw
corridor, Accra New Town — and the same question gets asked: which parts
of the city are actually at risk, and why?
This project builds a supervised machine learning model that predicts
flood susceptibility across the Greater Accra Metropolitan Area using
satellite data extracted from Google Earth Engine. Flood labels were
derived from Sentinel-1 SAR imagery captured during the June 2020 floods,
and the model was trained on terrain, rainfall, vegetation, and land cover
features at 30m resolution.
---
## Study Area
Greater Accra Metropolitan Area (GAMA), Ghana
Bounding box: 5.35°N – 5.85°N, 0.55°W – 0.05°W
Reference flood event: June 2020
---
## Data Sources
| Dataset | Source | Use |
|---|---|---|
| Sentinel-1 SAR (GRD) | Copernicus / GEE | Flood label generation |
| SRTM DEM 30m | USGS / GEE | Elevation, slope, aspect, TWI |
| HydroSHEDS Flow Accumulation | WWF / GEE | Topographic Wetness Index |
| JRC Global Surface Water | EC JRC / GEE | Distance to river |
| CHIRPS Daily Rainfall | UCSB / GEE | Mean annual rainfall |
| ESA WorldCover 2020 | ESA / GEE | Land use / land cover |
| Sentinel-2 SR | Copernicus / GEE | NDVI |
---
## Features
| Feature | Description |
|---|---|
| Elevation | Height above sea level (SRTM) |
| Slope | Terrain steepness |
| Aspect | Slope orientation |
| TWI | Topographic Wetness Index |
| Distance to river | Proximity to nearest water body (JRC GSW) |
| Mean annual rainfall | 10-year average from CHIRPS (2010–2020) |
| Land cover | ESA WorldCover 2020 class |
| NDVI | Vegetation index from Sentinel-2 |
---
## Model
Algorithm: Random Forest Classifier
Training samples: 2,000 (1,000 flooded, 1,000 non-flooded)
Validation: 80/20 train-test split + 5-fold stratified cross-validation
| Metric | Result |
|---|---|
| AUC-ROC | 0.982 |
| F1 Score | 0.927 |
| A …