Reservoir Flood Extents for Dry and Wet Day Scenarios

Separate packages for each large raised reservoir show predicted flood extents for two credible worst-case scenarios: a 'dry-day' and a 'wet-day' release. The data, produced by the Environment Agency, models flood extents from reservoir failure under different local river conditions. It excludes smaller reservoirs and those commissioned after the modeling program began in October 2016.

Use Cases

• Model downstream flood risk by comparing 'dry-day' and 'wet-day' scenario extents for specific reservoirs.
• Assess infrastructure vulnerability by overlaying predicted flood extents from the 'wet-day' scenario onto maps.
• Support land-use planning by analyzing the spatial extent of potential flooding from reservoir failure.

Strengths

• Models two distinct and credible worst-case scenarios ('dry-day' and 'wet-day') for each reservoir.
• Focuses on large raised reservoirs, a critical infrastructure subset for flood risk assessment.
• Data is maintained and updated by the authoritative Environment Agency, with a last update in March 2026.

Limitations

• Flood extents are not provided for smaller reservoirs, limiting comprehensive regional analysis.
• Does not include reservoirs commissioned after October 2016, creating a temporal coverage gap.
• The data provides no probability or likelihood estimates for the modeled flood events.

Provenance

Source

Environment Agency

Collection Method

Reservoir modeling program for flood extent prediction.

Time Range

Modeling program began October 2016; data current as of 2026.

Freshness

Last updated March 2026.

Geography

United Kingdom (focus on large raised reservoirs).