UK Surface Water Flood Hazard Ratings and Likelihood

Risk of Flooding from Surface Water maps assess flood hazard based on depth and speed, with likelihood expressed in three annual probability bands: High (≥3.3%), Medium (1-3.3%), and Low (0.1-1%). Produced by the UK Environment Agency using national and local flood authority modelling, the dataset was last updated in April 2026.

Use Cases

• Classify land parcels into High, Medium, or Low annual flood likelihood bands for risk zoning.
• Model flood hazard severity using combined depth and speed ratings (0, 0.25, 0.5, 0.75, 1.25, 2).
• Identify areas with 'Very Low' risk (below 0.1% annual chance) outside mapped extents for baseline comparisons.
• Integrate probabilistic flood hazard layers with property data to estimate asset vulnerability.

Strengths

• Provides six distinct flood hazard rating thresholds (0 to 2) for granular analysis.
• Defines three explicit annual probability likelihood bands with clear numerical thresholds (e.g., 1 in 30 year chance).

Limitations

• Data format is PDF, limiting direct computational analysis and integration with GIS or ML workflows.
• Probabilistic nature shows overall risk, not specific event scenarios, limiting use for single-event forecasting.

Provenance

Source

Environment Agency (UK)

Collection Method

National scale modelling enhanced with compatible local modelling from Lead Local Flood Authorities.

Time Range

null

Freshness

Updated April 2026.

Geography

United Kingdom