Flood Risk In Northern Ireland: How DfI Rivers Maps Flooding

Northern Ireland does not use Flood Zones or flood risk bands. It has its own maps, its own probability levels, its own planning policy and a single phone number for reporting flooding. This page explains how DfI Rivers classifies flood risk, who does what, how to check an address, and what flood risk means for planning and insurance in Northern Ireland.

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How Is Flood Risk Classified In Northern Ireland?

Flood risk in Northern Ireland is classified by annual exceedance probability, the chance a flood of a given size is exceeded in any one year, at three levels: high, medium and low. DfI Rivers sets different thresholds for rivers, the sea and surface water.

The probability levels on Flood Maps NI are shown below.

Each level means that chance or greater. Flood Maps NI also has a historical layer showing areas known to have flooded, drawn from records DfI Rivers made at the time of past floods. For detailed river and coastal maps, DfI Rivers states that "The mapping produced takes into account flood defences."

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Who Is Responsible For Flood Risk In Northern Ireland?

In Northern Ireland, the Department for Infrastructure, through DfI Rivers, manages flooding from rivers and the sea and publishes the flood maps. DfI is also the lead body for flood risk management planning, working with Northern Ireland Water and local councils.

DfI's FAQ states that "The Department for Infrastructure is the competent authority for implementing the Floods Directive Regulations in Northern Ireland in partnership with a number of other statutory bodies, including Northern Ireland Water and local councils." Responsibility in practice is split as below.

Flooding on roads, from burst water mains or from blocked drains is reported on one number, 0300 2000 100, which is available 24 hours a day, seven days a week. NI Direct explains that staff will know which agency needs to respond. In an emergency, call 999.

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How Do You Check Flood Risk In Northern Ireland?

The flood risk of an address in Northern Ireland is shown on Flood Maps NI, which DfI Rivers describes as an interactive map-viewer that enables users to access the latest flood hazard information available from government.

The checker on this site covers Northern Ireland too, but by a different route, and the difference matters. DfI's maps are not published under an open licence, so our figures are not taken from them — they come from a European river flood model sampled at about 90 metres. Three consequences follow, and each is stated on every Northern Ireland result: the figures are modelled, not DfI's official mapping; they are undefended, because the model does not account for flood defences, so a defended place can read as more exposed than DfI's map shows; and they cover rivers only, because no open coastal, surface water or groundwater source exists for Northern Ireland. For a property-level answer, Flood Maps NI remains the reference.

The official sources are:

1. Flood Maps NI — present and climate change flood extents for rivers and the sea, surface water extents, and the historical flood layer.
2. DfI Rivers water level network — levels for rivers, sea and loughs at approximately 130 locations.
3. Severe weather warnings — NI Direct points residents to the Met Office for weather warnings; no separate DfI flood warning sign-up is listed.

Two limits matter when reading the maps. Broad-scale strategic models, used where no detailed map exists, are not considered to be sufficiently accurate to determine the flood risk to a particular property or specific point location. And the maps do not identify flooding caused by blockages to culvert inlet grilles, deficiencies or system failures in local sewer systems or from small watercourses with catchments less than 3km².

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How Does Northern Ireland's System Compare With The Rest Of The UK?

Northern Ireland and Scotland both set high probability at 10% a year, well above the 3.3% used in England and Wales. Northern Ireland's planning policy is built on defined flood plains rather than zones or bands.

The four systems are compared below.

The Northern Irish planning flood plain uses the same thresholds as England's Flood Zone 3 for rivers (1%) and the sea (0.5%), so it is the closest equivalent. It is not identical: English zones ignore defences, and the Northern Irish policy has its own exceptions. Each system is explained on flood risk in England, flood risk in Wales and flood risk in Scotland.

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Which Areas Of Northern Ireland Have The Highest Flood Risk?

The areas of Northern Ireland with the greatest assessed flood risk are its Areas of Potential Significant Flood Risk. The Northern Ireland Flood Risk Assessment 2018 identified 12 areas as APSFR and 9 areas have been determined as TAPSFR, with transitional areas carried over from the 2011 assessment.

Together the 21 areas are Antrim, Ballymena, Banbridge, Bangor, Belfast, Carrickfergus, Coleraine, Downpatrick, Dundonald, Glengormley and Mallusk, Larne, Londonderry, Lurgan, Newcastle, Newry, Newtownabbey, Newtownards, Omagh, Portadown and Craigavon, Strabane and Warrenpoint.

1. Enniskillen flood risk High 21.8% of homes at Medium or High no separate surface water figure
2. Omagh Town flood risk High 18.1% of homes at Medium or High no separate surface water figure
3. Strabane flood risk High 15.8% of homes at Medium or High no separate surface water figure
4. Newry flood risk High 12.6% of homes at Medium or High no separate surface water figure
5. Antrim flood risk High 12.2% of homes at Medium or High no separate surface water figure
6. Banbridge flood risk High 9.7% of homes at Medium or High no separate surface water figure
7. Randalstown flood risk High 9.5% of homes at Medium or High no separate surface water figure
8. Belfast City flood risk Medium 6.6% of homes at Medium or High no separate surface water figure
9. Coleraine flood risk Medium 6.3% of homes at Medium or High no separate surface water figure
10. Portrush flood risk Medium 6.3% of homes at Medium or High no separate surface water figure
11. Lisburn City flood risk Medium 6.3% of homes at Medium or High no separate surface water figure
12. Craigavon Urban Area Including Aghacommon flood risk Medium 5.8% of homes at Medium or High no separate surface water figure
13. Ballymena flood risk Medium 5.1% of homes at Medium or High no separate surface water figure
14. Holywood flood risk Very low 4.3% of homes at Medium or High no separate surface water figure
15. Warrenpoint / Burren flood risk Very low 2.9% of homes at Medium or High no separate surface water figure

Counties in Northern Ireland

1. flood risk in Cambridgeshire 5 districts ranked · 6% of homes at Medium or High
2. flood risk in Derbyshire 8 districts ranked · 1.1% of homes at Medium or High
3. flood risk in Devon 8 districts ranked · 3.8% of homes at Medium or High
4. flood risk in East Sussex 5 districts ranked · 1.8% of homes at Medium or High
5. flood risk in Essex 12 districts ranked · 1.1% of homes at Medium or High
6. flood risk in Gloucestershire 6 districts ranked · 2.3% of homes at Medium or High
7. flood risk in Hampshire 11 districts ranked · 1.2% of homes at Medium or High
8. flood risk in Hertfordshire 10 districts ranked · 0.9% of homes at Medium or High
9. flood risk in Kent 12 districts ranked · 2.2% of homes at Medium or High
10. flood risk in Lancashire 12 districts ranked · 2.5% of homes at Medium or High

DfI notes that locations not designated APSFR may still be at risk of flooding. It also states that In Northern Ireland there are far fewer properties located within the flood plain, compared with the rest of the UK.

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What Does Flood Risk Mean For Planning In Northern Ireland?

In Northern Ireland, flood risk in planning is governed by the Revised Planning Policy Statement 15 'Planning and Flood Risk', September 2014. Its first policy, FLD 1, states that development will not be permitted within the 1 in 100 year river flood plain or the 1 in 200 year coastal flood plain unless the applicant can show that the proposal is an exception.

The policy's main tests are:

1. FLD 1 — flood plains. Development inside the 1% river or 0.5% coastal flood plain is refused unless it qualifies as an exception.
2. FLD 2 — flood defence and drainage infrastructure. The planning authority will not permit development that would impede the operational effectiveness of flood defence and drainage infrastructure or hinder access to enable their maintenance.
3. Flood risk and drainage assessments. After consultation, a developer may be asked for a Flood Risk Assessment or a Drainage Assessment.

Flood Maps NI is used by councils in planning, alongside historical evidence and site-specific flood risk assessments where required.

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What Does Flood Risk Mean For Insurance In Northern Ireland?

Flood cover in Northern Ireland is sold as part of home insurance in the same way as elsewhere in the UK, and Flood Re covers Northern Ireland for eligible homes built before 1 January 2009. DfI states that "The decision to offer flood insurance rests with individual insurance companies."

Insurers can use DfI's data directly: "Flood Maps (NI) may be licensed by insurers for commercial purposes." Flood Re's premium table for Northern Ireland uses numbered bands 1 to 8 rather than the lettered bands used in Great Britain. Specialist providers are listed in the BIBA and ABI Flood Insurance Directory, on 0370 950 1790. How premiums and refused cover work is explained in flood insurance, and the scheme's rules in Flood Re.

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Sources (Verified 16 Sep 2026)