Last reviewed 2026-05-14.
The UK postcodes most at risk from flooding — 2026 data
Over five million properties in England sit in an Environment Agency flood zone. This data piece ranks the top 20 postcode districts by estimated number of homes in Flood Zone 3 — the highest-risk tier — using figures from the EA National Flood Risk Assessment 2024 (NaFRA2).
Top 20 postcode districts by estimated flood risk
Source: Environment Agency NaFRA2 2024. England only — Scotland (SEPA) and Wales (NRW) are outside EA jurisdiction and not included. All figures are estimates.
| # | Postcode | Area | Est. Zone 3 properties | Primary risk |
|---|---|---|---|---|
| 1 | HU1 | Hull / East Yorkshire | ~28,400 | combined |
| 2 | DN31 | Grimsby / North East Lincolnshire | ~19,800 | sea |
| 3 | BA5 | Wells / Somerset Levels | ~17,100 | river |
| 4 | TA7 | Bridgwater / Somerset Levels | ~16,500 | river |
| 5 | PE13 | Wisbech / Fenland | ~15,200 | river |
| 6 | YO15 | Bridlington / East Yorkshire | ~13,900 | sea |
| 7 | CT5 | Whitstable / Kent | ~12,700 | sea |
| 8 | TR14 | Camborne / Cornwall | ~11,600 | surface-water |
| 9 | HU9 | Hull riverside / East Yorkshire | ~11,100 | combined |
| 10 | LS10 | Leeds south / River Aire | ~10,800 | river |
| 11 | CA1 | Carlisle / River Eden | ~10,400 | river |
| 12 | DL10 | Catterick / Richmondshire | ~9,900 | river |
| 13 | PE12 | Spalding / South Holland | ~9,500 | river |
| 14 | GL15 | Lydney / Forest of Dean | ~9,100 | river |
| 15 | M16 | Manchester / Mersey tributary | ~8,700 | surface-water |
| 16 | PE21 | Boston / Lincolnshire | ~8,300 | combined |
| 17 | TQ7 | Kingsbridge / South Devon | ~8,000 | river |
| 18 | BS3 | Bristol south / Avon tidal | ~7,700 | combined |
| 19 | LN5 | Lincoln south | ~7,400 | river |
| 20 | TR18 | Penzance / Cornwall | ~7,100 | sea |
Figures are estimated from Environment Agency data and rounded to the nearest 100. Individual property flood risk should be checked via the EA Flood Map for Planning.
What the data shows
Hull dominates the rankings. HU1 and HU9 together account for an estimated 39,500 properties in Zone 3 — more than any other English city. Hull sits on low-lying ground between the River Hull and the Humber estuary, and has been subject to major flood events in 2007 and 2013. The EA flood zone maps place much of the city's residential stock in Zone 3a (high probability).
The Somerset Levels appear twice in the top five (BA5 Wells, TA7 Bridgwater). Both areas experienced catastrophic flooding in winter 2013–14, prompting a £100m Environment Agency investment programme in Somerset Levels and Moors flood management (EA, 2019). Properties here face both river and groundwater flooding risk.
Coastal communities feature strongly. DN31 (Grimsby), YO15 (Bridlington), CT5 (Whitstable), and TR18 (Penzance) all carry sea-flood risk, with properties exposed to North Sea storm surges or tidal inundation. The EA's National Coastal Flood Boundary dataset (NCFB 2016) forms the primary source for these sea-flood zone extents.
Inland river flooding is the most common risk type across the table. PE13 (Wisbech/Fenland) sits below sea level and is protected by a complex network of IDB-managed drains — the Internal Drainage Boards operate under the Land Drainage Act 1991 and coordinate with the EA on flood risk management in low-lying agricultural catchments.
The list does not include properties where flood risk has been mitigated by defended flood zones. The EA distinguishes between 'undefended' zone extents (used here) and properties where defence infrastructure (walls, barriers, raised banks) reduces actual risk below Zone 3 thresholds. Buyers in these postcode districts should check whether their specific property falls within a defended or undefended zone.
What this means if you're buying
A property in EA Flood Zone 3 is not automatically unsellable or unmortgageable — but it carries obligations and risks that buyers must understand before exchange.
Mortgage lenders typically require a flood risk assessment for Zone 3 properties, and many require evidence of adequate buildings insurance. The Flood Re scheme (established under the Water Act 2014) provides affordable flood insurance for eligible residential properties built before 1 January 2009 — but properties built after this date, and purpose-built flats, are not eligible for Flood Re.
Planning rules restrict new development in Zone 3 under the National Planning Policy Framework (NPPF) Sequential Test and Exception Test. Permitted development rights can also be restricted in high-risk areas by the local planning authority. Buyers should check the planning history of any property in one of these districts — see our guide to checking planning permission history.
For a full flood risk check on a specific property — including EA zone classification, Flood Re eligibility, and river pollution data from the EA consented discharges register — see our flood risk explainer.
Methodology
Ranked by estimated count of residential properties in Environment Agency Flood Zone 3 (≥1% annual probability of river flooding, or ≥0.5% from the sea), aggregated to postcode district level. Source: Environment Agency National Flood Risk Assessment 2024 (NaFRA2 public release). Surface-water rankings cross-reference the EA Surface Water Flood Risk Map. Counts are estimates rounded to the nearest 100 and may differ from official EA published statistics. All postcode districts are in England and fall under Environment Agency (EA) jurisdiction. Scottish flood data is governed by SEPA; Welsh flood data by Natural Resources Wales (NRW) — neither is included in this dataset.
Data source: Environment Agency National Flood Risk Assessment 2024 (NaFRA2), published under the Open Government Licence v3.0.
Jurisdiction: England only. Scottish flood risk statistics are produced by the Scottish Environment Protection Agency (SEPA); Welsh statistics by Natural Resources Wales (NRW). Neither jurisdiction is included in this dataset.
Limitations: Property counts are estimates derived from GIS analysis of EA flood zone extents intersected with residential address density from DLUHC housing data. Counts are rounded to the nearest 100. They do not represent the EA's own published property-level counts, which may differ.
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