Flood Risk in Wales: Why 1 in 7 Properties Are Already at Risk

Flood risk is the most immediate physical climate risk facing Welsh communities, and it is already here rather than approaching.

The 60-word answer

Natural Resources Wales estimates around 275,000 properties in Wales, roughly one in seven, are at risk of flooding, after removing properties counted under more than one source. Risk is assessed separately for rivers, the sea, and surface water and small watercourses. Under central climate assumptions and assuming no defences, risk in every category rises substantially by 2120.

What the evidence says

• Reported: approximately 275,000 properties at risk, about one in seven, on NRW’s de-duplicated figure.
• Projected: under NRW’s central climate assumptions and assuming no defences, properties at risk by 2120 reach roughly 130,969 from rivers, 131,501 from the sea and 192,753 from surface water and small watercourses, against 106,477, 91,707 and 144,252 respectively in 2025.
• Methodological: those three categories overlap. A property can appear in more than one. They must never be summed.

What the numbers actually mean

“At risk” means a property falls within an area with a modelled likelihood of flooding, not that it floods regularly or that it will flood. The 2120 figures are a scenario: they assume central climate projections and that defences are not maintained or improved. They measure exposure if nothing is done, which is what makes them useful for planning, and why quoting them as a forecast would be wrong.

What it does not mean

It does not mean 275,000 Welsh homes will flood. It does not mean the three categories combine to over 450,000 properties in 2120, that arithmetic is invalid because of overlap. And surface water risk, the largest single category, is not primarily about rivers bursting: it is about rainfall exceeding drainage capacity, often far from any watercourse.

Why this matters in Wales

Welsh settlement patterns concentrate people in valley floors and along the coast, which is where river and tidal risk coincide. Surface water risk is dispersed across urban areas and is growing with more intense rainfall and the continued sealing of permeable surfaces. Insurance availability, planning decisions and business continuity all follow from these maps.

What can be done

• Check the actual risk for a property or site against NRW’s published flood risk maps rather than assuming.
• Treat surface water seriously, sustainable drainage, permeable surfacing and roof runoff management are within the control of most site operators.
• Write adaptation into continuity planning, not just mitigation into net zero planning. They are different disciplines and organisations routinely do only the second.
• Natural flood management upstream, leaky dams, restored peat, woodland in the right places, reduces peak flows, though it complements rather than replaces engineered defences.

Sources and methodology

• Flood risk information and Flood Risk Assessment Wales, Natural Resources Wales.

All property counts are NRW’s. The de-duplicated headline (275,000) and the per-source counts come from different tables and are not interchangeable.

Last reviewed: 31 August 2026.

Context: Climate change in Wales. Related: water deficits by 2050. Organisations can publish a climate pledge.