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.
- 30 to 1
- 41 to 1
- 1 to 2
- 2 to 2
- 2 to 3
- 23 to 3
Bands
| Bucket | Value |
|---|---|
| 0 to 1 | 3 figures |
| 1 to 1 | 4 figures |
| 1 to 2 | 0 figures |
| 2 to 2 | 0 figures |
| 2 to 3 | 0 figures |
| 3 to 3 | 2 figures |
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 |
|---|---|---|---|
| ruledesign-flood-river | 1% | 1 to 1% | 1 |
| ruledesign-flood-tidal | 0.5% | 0.5 to 0.5% | 1 |
| ruledesign-flood-surface-water | 1% | 1 to 1% | 1 |
| ruleflood-zone-1 | 0.1% | 0.1 to 0.1% | 1 |
| ruleflood-zone-2 | 1% | 1 to 1% | 1 |
| ruleflood-zone-3a | 1% | 1 to 1% | 1 |
| ruleflood-zone-3b | 3.3% | 3.3 to 3.3% | 1 |
| ruleminor-extension | 3.3% | 3.3 to 3.3% | 1 |
| ruleaccess-and-escape | 0.1% | 0.1 to 0.1% | 1 |
Every figure, with its source
One row per published figure: the figure as the source's own page publishes it, the page, and the day it was read. A figure that is not on a page we read is not on this one.
| Source | Figure | Breakdown | Read |
|---|---|---|---|
| Planning Practice Guidance - flood risk and coastal change | 3.3% | flood-zone-3b | 2026-10-27 |
| Flood risk assessments: applying for planning permission | 3.3% | minor-extension | 2026-10-27 |
| Planning Practice Guidance - flood risk and coastal change | 1% | design-flood-river | 2026-10-27 |
| Planning Practice Guidance - flood risk and coastal change | 1% | design-flood-surface-water | 2026-10-27 |
| Planning Practice Guidance - flood risk and coastal change | 1% | flood-zone-2 | 2026-10-27 |
| Planning Practice Guidance - flood risk and coastal change | 1% | flood-zone-3a | 2026-10-27 |
| Planning Practice Guidance - flood risk and coastal change | 0.5% | design-flood-tidal | 2026-10-27 |
| Planning Practice Guidance - flood risk and coastal change | 0.1% | flood-zone-1 | 2026-10-27 |
| Preparing a 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, 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, 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, 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, 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, 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, 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, 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, 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, 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
6 named sources were read in full on the dates shown and print no usable figure. They are counted, never filled in.
- Flood risk assessments: 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, read 2026-10-27: read in full and no accepted figure on the page
- Check the long term flood risk for an area, read 2026-10-27: read in full and no accepted figure on the page
- NPPF chapter 14 - 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, read 2026-10-27: read in full and no accepted figure on the page
- SEPA - 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
10 candidate sentences on these pages were refused by a reviewer; each refusal and its reason is recorded in the review ledger.
Sources (12)
- Planning Practice Guidance - flood risk and coastal change(the publisher's own terms; quoted for reporting and comment)
- Flood risk assessments: applying for planning permission(the publisher's own terms; quoted for reporting and comment)
- Preparing a flood risk assessment: standing advice(the publisher's own terms; quoted for reporting and comment)
- Flood risk assessments: the sequential test for applicants(the publisher's own terms; quoted for reporting and comment)
- National flood risk standing advice for local planning authorities(the publisher's own terms; quoted for reporting and comment)
- Flood map for planning(the publisher's own terms; quoted for reporting and comment)
- Check the long term flood risk for an area(the publisher's own terms; quoted for reporting and comment)
- National Planning Policy Framework(the publisher's own terms; quoted for reporting and comment)
- NPPF chapter 14 - flooding and coastal change(the publisher's own terms; quoted for reporting and comment)
- Flood and Water Management Act 2010(the publisher's own terms; quoted for reporting and comment)
- Welsh Government - TAN 15 development, flooding and coastal erosion(the publisher's own terms; quoted for reporting and comment)
- SEPA - planning guidance and advice notes(the publisher's own terms; quoted for reporting and comment)
Cite or embed this figure
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/.
Download the CSV (9 rows, computed 2026-10-28)