An England flood-zone map and an environmental permit answer different questions. The Environment Agency’s flood-risk activity rules depend on the work and its distance from a main river, flood defence, culvert, or sea defence. Foundations, service trenches, grading, drainage, retaining structures, or access work may need a separate check even when planning permission is also being considered.
Identify the watercourse and the actual work
Use the Environment Agency’s current main-river map, then describe the work and its location to the Agency before relying on a map measurement. Its guidance lists activities that may need permission, including putting a structure in, over, or under a main river; changing structures that affect flow or drainage; and excavation or other activity within specified distances.
| Example in the Environment Agency guidance | Distance that may trigger a check |
|---|---|
| Quarrying or excavation near a main river, flood defence (including a remote defence), or culvert | Within 16 metres |
| Activity near the bank of a main river, or near a flood defence or culvert on a main river | Within 8 metres; 16 metres for a tidal main river |
| Activity near a sea defence | Within 16 metres |
Other activities on a floodplain may also be regulated, and exemptions or exclusions have their own conditions. These distances are prompts to check the current rules, not a guarantee that work outside them is unrestricted or that every activity inside them requires the same permit.
Confirm the right consent route
If the work is regulated, the Environment Agency describes three routes: a registered exemption, a standard-rules permit, or a bespoke permit. Which route fits depends on the exact activity and its conditions. Check the current GOV.UK guidance and ask the Agency if the activity or distance is uncertain. The page was updated on 9 October 2026, including information about getting advice before applying, so recheck it before design or submission.
Work on an ordinary watercourse usually does not use the Environment Agency’s main-river flood-risk permit route. Contact the local council or internal drainage board to ask whether land-drainage consent is needed. Wales, Scotland, and Northern Ireland have separate rules and authorities.
Keep the checks separate
An environmental permit does not replace planning permission, building approval, a flood-risk assessment, or any site-specific engineering work. A flood map does not by itself determine whether a proposed excavation or structure is a regulated activity. Give the authority the parcel, the proposed footprint, the work method, and measured distances, and keep its written response with the project records.
See the broader flood and hazard screening guide for map and assessment checks. This page does not determine whether a particular ADU needs a permit or will be approved.