Sefton Flood Risk Areas from 1 in 30 Year Hydraulic Model

200,000 homes in the North West are estimated to be at flood risk. This dataset contains flood outlines for Sefton, UK, generated by a 5m cell resolution hydraulic model simulating a storm event with a 3.3% annual probability. The model was developed by Sefton Council, the Environment Agency, Capita Symonds, and United Utilities, updated in 2013, and considers a 30% increase in rainfall intensity for climate change.

Use Cases

• Assess property-level flood damage potential based on modeled flood depths exceeding 0.08m internally.
• Identify urban areas at high risk from surface water flooding using the strategic risk assessment methodology.
• Model flood hazard and velocity for a 1 in 30 year storm event to inform infrastructure planning.
• Analyze the impact of climate change on flood risk by applying a 30% rainfall intensity factor.

Strengths

• Model outputs are based on flood velocity, depth, and hazard, incorporating a debris factor based on DEFRA guidance.
• The GIS data has been checked for geographic errors and is described as accurate.
• Modeling uses a 5m cell resolution and was conducted with industry-standard ESTRY-TUFLOW software.

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 13:32:24.339327; freshness should be verified.

Provenance

Source

Sefton Metropolitan Borough Council, Environment Agency, Capita Symonds, United Utilities

Collection Method

Hydraulic modeling using ESTRY-TUFLOW software, part of a Surface Water Management Plan.

Time Range

Model updated in 2013, based on events since 1990.

Freshness

Last updated 2026-07-08 13:32:24.339327

Geography

Sefton, North West England, UK