Sefton Flood Risk Areas: 1 in 100 Year Climate Change Model

200,000 homes in the North West are estimated to be at flood risk. This geospatial dataset models surface water flood risk in Sefton, UK, for a 1 in 100 year storm event with a 30% climate change rainfall increase, developed by Sefton Council and partners using ESTRY-TUFLOW software. The models were updated in 2013 and are based on flood depth, velocity, and hazard calculated on a 5-meter grid.

Use Cases

• Prioritizing flood defense investments based on modeled hazard ratings and property impact depths.
• Assessing climate change vulnerability for urban planning using the 30% rainfall intensity increase factor.
• Validating other flood models by comparing outputs against this detailed hydraulic simulation for Sefton.
• Identifying properties at risk using the 0.23m external flood depth threshold for damage assessment.

Strengths

• Model outputs are based on specific flood velocity, depth, and hazard calculations following DEFRA guidance (FD2321/TR1).
• The GIS data has been checked for geographic errors and is described as accurate.
• Models simulate three storm event probabilities (1 in 30, 1 in 100, 1 in 100+cc) with a defined climate change factor.
• Uses a detailed 5-meter cell size for spatial analysis of flood risk.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• The drainage network was not explicitly modeled but represented via a 'continuing loss' parameter.
• Last updated 2026-07-08 13:33:24.085303; freshness should be verified as the underlying models are from 2011/2013.

Provenance

Source

Sefton Metropolitan Borough Council, in partnership with the Environment Agency, Capita Symonds, and United Utilities.

Collection Method

Hydraulic modelling using ESTRY-TUFLOW software (version 2012-05-AE) as part of a Surface Water Management Plan and Strategic Risk Assessment.

Time Range

Models developed for the 2011 Surface Water Management Plan and updated in 2013; simulates storm events with defined annual probabilities.

Freshness

Last updated 2026-07-08 13:33:24.085303

Geography

Sefton, North West England, United Kingdom.