Global Annual Population Exposure to Flood Risk

An estimate of the annual physical exposure of populations to flooding, modeled for a global assessment. The dataset combines hydrological modeling, observed flood data from 1999 to 2007, and a 2010 population grid to calculate the expected average annual population exposed. It was designed by UNEP/GRID-Europe for the Global Assessment Report on Risk Reduction (GAR).

Use Cases

• Modeling expected average annual population exposed to floods using the combined hydrological and population grid.
• Assessing regional flood frequency by integrating the UNEP/GRID-Europe PREVIEW flood dataset's frequency data.
• Validating flood risk models with observed flood event data from the Dartmouth Flood Observatory (1999-2007).
• Analyzing population vulnerability in areas where flood frequency information was unavailable, defaulted to a 50-year return period.

Strengths

• Integrates multiple authoritative global data sources: HydroSHEDS, Dartmouth Flood Observatory, UNEP/GRID-Europe PREVIEW, and LandScan population data.
• Provides a modeled global coverage estimate for flood exposure.
• Uses observed flood events from a 9-year period (1999-2007) for calibration.

Limitations

• Population exposure is based on a single reference year (2010), which may not reflect current demographics.
• Flood frequency data has gaps, with a default 50-year return period assumption applied in unknown areas.
• The core observed flood data is over 15 years old, potentially missing recent climate and land-use change impacts.

Provenance

Source

UNEP/GRID-Europe, with support from USGS EROS Data Center and Dartmouth Flood Observatory.

Collection Method

GIS modeling combining statistical peak-flow estimation, hydrological modeling (HydroSHEDS, Manning equation), observed flood records, and a global population grid.

Time Range

Model reference year is 2007 for exposure; uses observed floods from 1999-2007 and 2010 population data.

Geography

Global