New Flood Maps for Planning: What Developers, Planners and Architects Need to Know

The Flood Map for Planning has just got fluvial flooding. On 28 May 2026, the Environment Agency added new surface water climate change extents and banded depth information to the service. For architects, planners and developers working on sites across England, this changes how surface water flood risk should be assessed and used in flood risk assessments for planning applications.

What Has Changed on the Flood Map for Planning?

Four datasets are now live on the Flood Map for Planning (FMfP) service and the Defra Data Services Platform (DSP):

• Surface Water Spatial Planning Extents – Present Day
• Surface Water Spatial Planning Extents – Climate Change
• Surface Water Spatial Planning Depths – Present Day
• Surface Water Spatial Planning Depths – Climate Change

The present day extents were already available. What is new is the climate change extents and most significantly banded depth information for both scenarios.

Depths are split into seven bands: under 150mm, 150–300mm, 300–600mm, 600–900mm, 900–1,200mm, 1,200–2,300mm, and over 2,300mm. This gives design teams real, usable information about flood severity — not just where water goes, but how deep it gets.

The datasets cover three annual exceedance probability (AEP) scenarios: 0.1% (1 in 1,000), 1% (1 in 100), and 3.3% (1 in 30). These are the standard return periods used across flood risk assessments and sequential testing in England.

Why the Previous Approach Was Not Fit for Purpose

Before this update, professionals were directed to use surface water data from the Check Your Long Term Flood Risk (CYLTFR) service when the FMfP lacked sufficient information. That approach had clear weaknesses.

CYLTFR uses a central (50th percentile) climate change scenario for the 2050s epoch (2040–2060). Most planning applications require the upper end (95th percentile) for the 2070s epoch (2061–2125), as set out in the Environment Agency's flood risk assessment climate change allowances. The CYLTFR scenario is simply not precautionary enough for most development types.

The depth information on CYLTFR was also inadequate. It did not provide the design flood depth data needed for planning — making it unsuitable for informing SuDS design or detailed flood risk assessments.

How the New Datasets Are Produced

The datasets are built by combining nationally produced flood model outputs with locally produced detailed models from Lead Local Flood Authorities (LLFAs). The approach prioritises the best available information at any given location — local detailed models take precedence where they exist.

One important technical detail: flooding shallower than 75mm is removed from the outputs. Surface water modelling typically shows very shallow water across most of a catchment during a rainfall event. Below 75mm, flooding is generally unlikely to prevent access or cause property flooding. Filtering it out keeps the data focused on meaningful risk levels.

The climate change scenarios are based on UK Climate Projections (UKCP18) from the Met Office, using Representative Concentration Pathway (RCP) 8.5. The upper end (95th percentile) for the 2070s epoch has been selected — a long-term horizon appropriate for planning and development decisions that will shape places for decades.

What Planners and Developers Should Do Right Now

The advice from the Environment Agency is clear: start using the new datasets straight away. Here is what that means practically.

Update your GIS tools. Add the new surface water datasets to the tools your team uses for development planning. Data feeds from the DSP are recommended — they keep your layers current automatically without manual updates.

Remove the CYLTFR surface water layers from your planning workflows. Two specific layers should no longer be used for development planning:

• Risk of flooding from surface water – present day extents and depths
• Risk of flooding from surface water – climate change extents and depths

Review live applications. Sites that previously fell outside any surface water flood risk area may now sit within one. Where that happens, a flood risk assessment or sequential test may be triggered. Existing flood risk assessments, sequential tests, or SuDS strategies may need to be updated to reflect the new data.

What These Datasets Can and Cannot Tell You

The new datasets are a significant improvement but they have defined limits that every user needs to understand.

They show flood risk to areas of land, not to individual properties. Property-level flood risk depends on factors — ground levels, construction type, thresholds, internal layouts — that cannot be captured in a spatial dataset. A site falling within a flood risk extent does not automatically mean every building on it will flood.

The datasets cover surface water flooding only. River flooding, tidal and coastal flooding, groundwater flooding, and infrastructure failure — blocked drains, surcharging sewers, overloaded storm drains — are not represented. A complete flood risk picture for any site requires assessment across all relevant sources.

How to Access the Data

The datasets are available through two routes.

The Flood Map for Planning digital service on GOV.UK presents the data as a layered interactive map. It can be accessed using a postcode, place name, or coordinates — no account required. It sits alongside Flood Zone data, flood defences, and water storage areas in a single view.

The Defra Data Services Platform (DSP) provides the datasets in GIS-compatible formats for professional use, including ESRI layer files with recommended symbology. Data feeds are available for live integration into GIS workflows.

How Urban Water Can Help

Surface water flood risk is now front and centre in the planning process. Getting the assessment right at the start of a project saves time, cost, and redesign later.

Urban Water works with architects, planners and developers to interpret flood risk data in the context of specific sites and proposals. From initial site appraisals using the new FMfP datasets, through to site-specific flood risk assessments, sequential and exception testing, SuDS strategies, and strategic flood risk assessments — our team brings technical depth and planning experience together.

If you have a live application affected by the new datasets, or a new site you want assessed against the updated surface water information, get in touch with the Urban Water team.