Check Flood Risk by Postcode: An England Planning Guide

The August 2026 NPPF, Annex F, distinguishes river/sea probability zones from other flood evidence. Zone 1 has less than 0.1% annual river/sea probability; Zone 2 sits between that level and the higher Zone 3a thresholds. Zone 3b is functional floodplain, normally including land with at least 3.3% annual probability with effective infrastructure, or land designed to flood. It is not simply land that floods every year.

The standard zone layer does not include defence benefits or climate change. The planning map also provides other datasets, including current/future surface-water information. Read each layer’s definition. Zone 3b is not separately distinguished from 3a on the national zone map; use the local assessment and resolve site-specific uncertainty.

The Environment Agency applicant guidance, updated 28 May 2026, includes development in Zones 2 or 3, Zone 1 sites of at least one hectare, and additional triggers involving future flood zones, surface water, critical drainage and other identified risk. Being below one hectare in Zone 1 is therefore not automatic clearance.

Scope the assessment with the appropriate adviser and authority. Straightforward low-risk proposals may be capable of a proportionate assessment by the applicant; it is inaccurate to say every case legally needs a “licensed flood consultant”. A substantive risk or uncertain access route warrants appropriate specialist input.

The sequential test addresses the location of development relative to flood risk. The exception test applies in specified circumstances depending on vulnerability, flood zone and the applicable exceptions. It is incorrect to say that Zone 2 normally avoids the sequential test or that the exception test applies only in Zone 3a.

Use current NPPF policies F5–F7 and Annex F, together with the authority’s interpretation for the proposal. Some older guidance retains superseded paragraph numbers. Confirm the current policy text and scope rather than copying a historical cross-reference into an application.

Save the map extract with its date, layer names and site boundary. Add the proposed use and vulnerability, levels information, access/escape route, drainage concept and development lifetime. Identify model limitations and climate allowances.

Read the local strategic flood risk assessment guidance alongside the actual authority document. Check recorded events, groundwater or sewer issues and the relevant drainage authority where needed. A national map is a starting point; missing local information remains an open question.

The Atlasly flood checker can help start the enquiry where information is available. Read the returned source and coverage limits, then verify material findings against the current official map. An address match or successful result does not certify the whole site, its access or a proposed use as safe.

Write the conclusion as an evidence statement: “The reviewed layer shows no mapped river/sea risk at this location; surface water, future risk and access still need review.” Avoid turning “no result returned” into “no flood risk”.