# Do i need a flood risk assessment: Flood Risk Planning Rules

> The Flood Risk Planning Rules carries 9 published figures read from 3 sources' own pages, from 0.10 to 3.30 percent, read 27 October 2026.

Flood risk assessment cost · https://floodriskassessmentcost.co.uk/datasets/flood-risk-planning-rules/ · computed 2026-10-28

**Range of the published figures:** 0.1 to 3.3 % (range 0.1 to 3.3 %; 9 published figures; 3 of 9 sources read publish one).

3 of the 9 named sources read in full publish a figure; 6 publish none, read 27 October 2026.

## By rule

| Breakdown | Median | Range | Sources |
|---|---|---|---|
| rule design-flood-river | 1 % | 1 to 1 % | 1 |
| rule design-flood-tidal | 0.5 % | 0.5 to 0.5 % | 1 |
| rule design-flood-surface-water | 1 % | 1 to 1 % | 1 |
| rule flood-zone-1 | 0.1 % | 0.1 to 0.1 % | 1 |
| rule flood-zone-2 | 1 % | 1 to 1 % | 1 |
| rule flood-zone-3a | 1 % | 1 to 1 % | 1 |
| rule flood-zone-3b | 3.3 % | 3.3 to 3.3 % | 1 |
| rule minor-extension | 3.3 % | 3.3 to 3.3 % | 1 |
| rule access-and-escape | 0.1 % | 0.1 to 0.1 % | 1 |

## Every figure, with its source

One row per source: the figure the source's own page publishes, the page, and the day it was read.

| Source | Figure | Breakdown | Read |
|---|---|---|---|
| [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) | 3.3 % | flood-zone-3b | 2026-10-27 |
| [Flood risk assessments: applying for planning permission](https://www.gov.uk/guidance/flood-risk-assessment-for-planning-applications) | 3.3 % | minor-extension | 2026-10-27 |
| [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) | 1 % | design-flood-river | 2026-10-27 |
| [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) | 1 % | design-flood-surface-water | 2026-10-27 |
| [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) | 1 % | flood-zone-2 | 2026-10-27 |
| [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) | 1 % | flood-zone-3a | 2026-10-27 |
| [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) | 0.5 % | design-flood-tidal | 2026-10-27 |
| [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) | 0.1 % | flood-zone-1 | 2026-10-27 |
| [Preparing a flood risk assessment: standing advice](https://www.gov.uk/guidance/flood-risk-assessment-standing-advice) | 0.1 % | access-and-escape | 2026-10-27 |

## The sentence each figure was read from (9)

- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change), read 2026-10-27: "• land having a 3.3% or greater annual probability of flooding, with any existing flood risk management infrastructure operating effectively; or"
- [Flood risk assessments: applying for planning permission](https://www.gov.uk/guidance/flood-risk-assessment-for-planning-applications), read 2026-10-27: "present day 3.3% annual probability extent of river and sea flooding with defences"
- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change), read 2026-10-27: "river flooding likely to occur with a 1% annual probability (a 1 in 100 chance each year); or"
- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change), read 2026-10-27: "surface water flooding likely to occur with a 1% annual probability (a 1 in 100 chance each year),"
- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change), read 2026-10-27: "Zone 2 Medium Probability Land having between a 1% and 0.1% annual probability of river flooding; or land having between a 0.5% and 0.1% annual probability of sea flooding."
- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change), read 2026-10-27: "Zone 3a High Probability Land having a 1% or greater annual probability of river flooding; or Land having a 0.5% or greater annual probability of sea."
- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change), read 2026-10-27: "tidal flooding with a 0.5% annual probability (1 in 200 chance each year); or"
- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change), read 2026-10-27: "Zone 1 Low Probability Land having a less than 0.1% annual probability of river or sea flooding."
- [Preparing a flood risk assessment: standing advice](https://www.gov.uk/guidance/flood-risk-assessment-standing-advice), read 2026-10-27: "how the development could be evacuated before an extreme flood – this is an event with a 0.1% annual probability of flooding plus an allowance for climate change"

## Read in full, publishes no figure

- [Flood risk assessments: the sequential test for applicants](https://www.gov.uk/guidance/flood-risk-assessment-the-sequential-test-for-applicants), read 2026-10-27: every candidate on the page was refused
- [National flood risk standing advice for local planning authorities](https://www.gov.uk/guidance/flood-risk-assessment-local-planning-authorities), read 2026-10-27: read in full and no accepted figure on the page
- [Check the long term flood risk for an area](https://www.gov.uk/check-long-term-flood-risk), read 2026-10-27: read in full and no accepted figure on the page
- [NPPF chapter 14 - flooding and coastal change](https://www.gov.uk/guidance/national-planning-policy-framework/14-meeting-the-challenge-of-climate-change-flooding-and-coastal-change), read 2026-10-27: read in full and no accepted figure on the page
- [Welsh Government - TAN 15 development, flooding and coastal erosion](https://www.gov.wales/technical-advice-note-tan-15-development-flooding-and-coastal-erosion), read 2026-10-27: read in full and no accepted figure on the page
- [SEPA - planning guidance and advice notes](https://www.sepa.org.uk/environment/land/planning/guidance-and-advice-notes/), read 2026-10-27: read in full and no accepted figure on the page

## Methodology

Every row is a verbatim sentence read from the named source's own page through our fetch service on the date shown, hash-pinned to the stored read (the sha of the page's visible text; the raw page is mirrored to R2). 3 of the 9 named sources that could be read published a usable figure; 6 published none and are recorded as not published, never filled in; 3 could not be read (blocked, dead or unreachable) and count nowhere. The headline figures (median, minimum, maximum, quartiles) are over ONE figure per source for each breakdown it prices, in % (a source's median where its page yielded several accepted sentences for one breakdown), so a page that gives figures for several breakdowns gives one for each and N counts 9 figures, never sentences; 10 candidate sentence(s) were refused by a reviewer with the reason recorded. The fuller derivation this dataset is chartered to grow into (not yet what the figures above are; they are each source's own published figure as read): one row per rule: the trigger (flood zone, site area, development vulnerability, critical drainage area), the test it requires and the authority that applies it, per nation

## Sources

- [Planning Practice Guidance - flood risk and coastal change](https://www.gov.uk/guidance/flood-risk-and-coastal-change) (the publisher's own terms; quoted for reporting and comment)
- [Flood risk assessments: applying for planning permission](https://www.gov.uk/guidance/flood-risk-assessment-for-planning-applications) (the publisher's own terms; quoted for reporting and comment)
- [Preparing a flood risk assessment: standing advice](https://www.gov.uk/guidance/flood-risk-assessment-standing-advice) (the publisher's own terms; quoted for reporting and comment)
- [Flood risk assessments: the sequential test for applicants](https://www.gov.uk/guidance/flood-risk-assessment-the-sequential-test-for-applicants) (the publisher's own terms; quoted for reporting and comment)
- [National flood risk standing advice for local planning authorities](https://www.gov.uk/guidance/flood-risk-assessment-local-planning-authorities) (the publisher's own terms; quoted for reporting and comment)
- [Flood map for planning](https://flood-map-for-planning.service.gov.uk/) (the publisher's own terms; quoted for reporting and comment)
- [Check the long term flood risk for an area](https://www.gov.uk/check-long-term-flood-risk) (the publisher's own terms; quoted for reporting and comment)
- [National Planning Policy Framework](https://www.gov.uk/government/publications/national-planning-policy-framework--2) (the publisher's own terms; quoted for reporting and comment)
- [NPPF chapter 14 - flooding and coastal change](https://www.gov.uk/guidance/national-planning-policy-framework/14-meeting-the-challenge-of-climate-change-flooding-and-coastal-change) (the publisher's own terms; quoted for reporting and comment)
- [Flood and Water Management Act 2010](https://www.legislation.gov.uk/ukpga/2010/29/contents) (the publisher's own terms; quoted for reporting and comment)
- [Welsh Government - TAN 15 development, flooding and coastal erosion](https://www.gov.wales/technical-advice-note-tan-15-development-flooding-and-coastal-erosion) (the publisher's own terms; quoted for reporting and comment)
- [SEPA - planning guidance and advice notes](https://www.sepa.org.uk/environment/land/planning/guidance-and-advice-notes/) (the publisher's own terms; quoted for reporting and comment)

## Cite or embed

- The Flood Risk Planning Rules carries 9 published figures read from 3 sources' own pages, from 0.10 to 3.30 percent, read 27 October 2026.
- 3 of the 9 named sources read in full publish a figure; 6 publish none, read 27 October 2026.
- Flood Risk Planning Rules, rule design-flood-river: median 1 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule design-flood-tidal: median 0.50 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule design-flood-surface-water: median 1 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule flood-zone-1: median 0.10 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule flood-zone-2: median 1 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule flood-zone-3a: median 1 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule flood-zone-3b: median 3.30 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule minor-extension: median 3.30 percent across 1 source, read 27 October 2026.
- Flood Risk Planning Rules, rule access-and-escape: median 0.10 percent across 1 source, read 27 October 2026.

Cite as: "floodriskassessmentcost.co.uk Flood Risk Planning Rules", updated 2026-10-28, https://floodriskassessmentcost.co.uk/datasets/flood-risk-planning-rules/.

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