River Wye Flooding & Flood Risk

River Wye flooding is a flood that travels. Rain on Plynlimon in mid-Wales takes more than a day to work down through Hay-on-Wye, Hereford and Ross-on-Wye, and in February 2020 it set new records at every Environment Agency gauge on the river in England. This is the Wye of Wales and Herefordshire, which joins the Severn below Chepstow. A site on its English bank and a site on its Welsh bank answer to different regulators and different flood rules, and our consultants work on both.

At 09:30 on 17 February 2020 the Wye stood at 6.111 m on the Old Wye Bridge gauge in Hereford, its highest level there in at least two hundred years, and the peak was still building towards Ross-on-Wye and Lydbrook.

For a site anywhere between Rhayader and Chepstow, call 01293 214444 or email enquiries@unda.co.uk.

• Which Wye this is. The Afon Gwy, which rises on Plynlimon and runs about 250 km through Powys and Herefordshire to the Severn Estuary. Not the Wye that flows through Buxton and Bakewell in Derbyshire, and not the small Wye under High Wycombe in Buckinghamshire.
• A border river at both ends. It starts in Wales, crosses into England below Hay-on-Wye, and for its last 26 km, from Redbrook to Chepstow, the river itself is the boundary between the two countries.
• Tidal below Bigsweir. The tide reaches about 24 km up from the Severn, past Tintern and Brockweir, so the lowest reach floods from the estuary as well as from the hills.
• Main River throughout. The Environment Agency regulates the English reaches and Natural Resources Wales the Welsh ones.

How a Wye flood moves downstream: the February 2020 peaks

A Wye flood arrives in Herefordshire hours after the rain has stopped, and it reaches each town in turn. In February 2020 the peak passed Bredwardine on the evening of 16 February, Hereford the next morning, Ross-on-Wye that night and Lydbrook in the early hours of 18 February, about 30 hours from first gauge to last. The coral line on the map below follows the Wye from its source to the Severn, and the pins are the Agency's live gauges; our live river levels map shows them beside gauges on other rivers. A postcode check screens a location against the national flood data, as the flood risk map does.

Every one of the Agency's English gauges on the main river logged its highest reading in that single flood. The table lists them from upstream to downstream, with the hour each peak passed.

Gauges on the Welsh reaches are run by Natural Resources Wales and do not appear on the map: the Wye at Hay-on-Wye and the Wye at Monmouth both publish live readings. Further down, the National River Flow Archive measured 925.8 cubic metres per second at Redbrook at 08:45 on 18 February 2020, the largest flow on its record.

Why does the River Wye flood?

The Wye floods because its head waters take in a huge amount of rain on thin soils over hard rock, then pour it into a valley that gets wider, gentler and more built-up downstream. Cefn Brwyn, high on Plynlimon, averages 2,457 mm of rain a year, and only about a third of the river's flow there comes from groundwater; the rest runs straight off the hillside.

Rainfall is the 1961 to 1990 average the archive publishes for each catchment. The Erwood peak of December 1960 is the highest flow gauged anywhere on the river, though it depends on a rating extended well beyond measured flows. The pattern in the table is the Wye's flood behaviour in miniature: a flashy upland stream that turns, below Builth Wells, into a large, slower river carrying the runoff from more than 4,000 square kilometres.

• Tributaries that add a peak of their own. The Elan joins near Rhayader, the Ithon above Builth Wells, the Irfon at Builth, the Llynfi at Glasbury, the Lugg at Mordiford just below Hereford, and the Monnow at Monmouth. Where the Lugg comes in, Hampton Bishop sits behind banks on both rivers.
• Regulated, but only at the top. The Elan Valley reservoirs above Rhayader store water for Birmingham, and the archive notes reservoir regulation and abstraction in the Redbrook record. They sit in the headwaters, so the big tributaries below them, the Ithon, Irfon, Lugg and Monnow, reach the Wye uncontrolled.
• Little town, much farmland. Built-up land covers only about 2% of the catchment above Redbrook, on the archive's land-cover figures. The Wye floods because of the rain and the ground, not because of paved surfaces.
• Held back by the tide. Below Bigsweir, a high tide in the Severn Estuary can hold back a flood coming down the valley, so levels at Brockweir and Chepstow depend on the timing of both. Our note on tidal flooding explains how that combination is assessed, and the River Severn page covers the estuary the Wye flows into.

Our guide to fluvial flooding covers the general mechanism; on the Wye, the length of the journey and the timing of the tributaries are what decide how high a flood gets at any one place.

When has the River Wye flooded?

Most of the Wye's largest floods have come in winter, when long spells of rain land on ground that is already wet, though the two headwater gauges set their records in August storms in 1957 and 1973. Storms Ciara and Dennis in February 2020 broke the level records in England; Storm Claudia in November 2025 flooded Monmouth, mostly from the Monnow, in what the county council's leader called unprecedented flooding.

1. December 1960. The largest flow ever gauged on the river, 1,228.8 m³/s at Erwood in Powys on 2 December, with high water at Belmont two days later (National River Flow Archive).
2. February 2014. The Old Wye Bridge gauge reached 4.94 m on 10 February, the highest reading there in the years before 2020, and every English gauge peaked within two days of it.
3. February 2020. Ciara on 9 February and Dennis a week later fell on a saturated catchment. Hereford's peak was reported at the time as the highest there in at least two hundred years (Yahoo News UK, 19 February 2020). The Agency counted 166 properties flooded in the city, while its defences kept water out of 201 more; at Hampton Bishop the Lugg overtopped its bank at a record level and 48 properties flooded (Environment Agency, Hereford; Environment Agency, Hampton Bishop). Herefordshire Council investigated the flooding under Section 19; our explainer on Section 19 reports says what those investigations cover.
4. January 2021 and February 2022. Storm Christoph sent 609 m³/s past Belmont on 21 January 2021 and Storm Franklin 573 m³/s on 21 February 2022, the second and fourth highest flows there on record (National River Flow Archive).
5. November 2025. Storm Claudia broke over Monmouthshire on 14 and 15 November. A major incident was declared in Monmouth at 1.30am on the 15th and Natural Resources Wales issued four severe flood warnings, one of them for the defended areas on the Wye and the Monnow (Shropshire Star / PA). The council's later investigation found the Monnow at or near record levels, with 233 homes and 109 commercial premises flooded internally (Nation.Cymru).

Those dates matter for a site because the Agency's flood mapping and a council's strategic flood risk assessment are checked against them. A scheme on land that went under in 2020 or 2025 will be asked how it would have fared.

Where does the River Wye flood? Towns and villages from Rhayader to Chepstow

Hereford and Monmouth carry the largest exposure, but flooding from the Wye reaches every town on its banks. Warnings on the English reaches come from the Environment Agency, inside its River Wye in Herefordshire alert area; Natural Resources Wales covers the Welsh reaches through its River Wye in Powys and Rivers Wye and Monnow in Monmouthshire alert areas.

On the English side the Agency runs eleven flood warning areas along the Wye, one of them for the Yazor and Widemarsh Brooks in Hereford, under three alert areas. More on the counties the river crosses is on our Herefordshire and Gloucestershire pages. Inside a warning area, a site is very likely to sit in a higher flood zone, which our guide to flood zones 1, 2 and 3 explains, and the meadows that take the overflow are part of the protection, as our note on why floodplains matter sets out.

English bank or Welsh bank: what the River Wye means for a site

The rules for a site near the Wye depend on which country it is in, not on where the water came from. On the English bank, in Herefordshire and the Forest of Dean, the Environment Agency advises the council and national policy on flood risk sits in chapter 18 of the NPPF; on the Welsh bank, in Powys and Monmouthshire, Natural Resources Wales advises and TAN15 applies.

• Main River on both sides. The Wye's own channel is a Main River for its whole length; the brooks, dingles and ditches feeding it are ordinary watercourses, overseen by the lead local flood authority and looked after by their riparian owners.
• Permits near the bank. Building, digging or storing material within 8 metres of the Wye, or 16 metres on the tidal reach below Bigsweir, may need a flood risk activity permit from the Environment Agency in England or from Natural Resources Wales, as set out in the government's permit guidance.
• England: a flood risk assessment. A site in Flood Zone 2 or 3, or a large site in Zone 1, needs a site-specific assessment under the NPPF and its planning practice guidance, with the sequential test where a new home or business is proposed in a flood zone.
• Wales: a flood consequence assessment. The current TAN15 came into force on 31 March 2025, and Natural Resources Wales' Flood Map for Planning is the map that counts; our pages on the 2025 TAN15, Welsh flood zones and the role of Natural Resources Wales explain the differences.
• Climate change on both banks. Either report has to show the development stays safe for its lifetime under the published climate change allowances, which increase the peak river flow the assessment has to plan for.
• Four councils as lead local flood authorities. Powys, Herefordshire, Gloucestershire and Monmouthshire each handle surface water and ordinary watercourses on their stretch, and each sets its own drainage expectations, summarised in our note on what planning authorities ask for.

Phosphate as well as flood water in the Wye catchment

A planning application in the Wye catchment can face a second water question alongside flooding. The River Wye and part of the Lugg are a Special Area of Conservation, and in May 2023 Natural England downgraded the Wye's condition to unfavourable and declining, with phosphate pollution the main cause (Natural England).

Schemes that add overnight accommodation in the affected catchments have to show nutrient neutrality before the council can complete its habitats assessment. That shapes the drainage: the surface water and foul water arrangements for a Wye site are judged on what they carry to the river as well as on how fast.

Flood and drainage reports for land beside the Wye

Sites on the Wye's floodplain, and on higher ground that drains to it, need different reports for different questions. A flood risk assessment asks whether a site is safe from the river and every other source; a sequential test asks whether the development belongs on that site at all; a drainage strategy asks where the rain falling on the finished site goes, and at what rate.

• Sites in the Wye's flood zones. A flood risk assessment that starts from the nearest gauge record, the Agency's modelled outlines and the defences in front of the site.
• Applications on the English bank. A flood risk assessment for planning for Herefordshire Council or the Forest of Dean, covering floor levels, safe access in a flood like 2020 and any effect on neighbours.
• Applications in Powys and Monmouthshire. A flood consequence assessment prepared to TAN15 for sites at Builth Wells, Hay-on-Wye, Monmouth or Chepstow.
• Buying near the river. A flood risk survey for property purchase for a house or business premises in a town the Wye has flooded, before exchange.
• New homes in a Herefordshire flood zone. A sequential and exception test report showing why no lower-risk site is reasonably available.
• Drainage evidence for a planning application. A drainage strategy that sets out how the site deals with rainfall and, in this catchment, with phosphate.
• Runoff from new roofs and roads. A surface water drainage strategy holding discharge to the rate the lead local flood authority will accept.
• Conditions attached to a consent. The information needed for the discharge of drainage conditions set by the council.
• Levels where the national mapping falls short. Flood modelling of the Wye or a tributary where the site sits behind a bank, at a confluence or on the tidal reach.
• Homes the river has already reached. A flood risk assessment for insurance for owners in Hereford, Hampton Bishop, Ross-on-Wye or Monmouth, where water has already been inside homes.
• Premises that must keep running. A business continuity flood risk assessment for shops and firms like the 109 Monmouth premises flooded inside in November 2025.
• Commercial land on the floodplain. A BREEAM flood risk assessment for buildings at Rotherwas or elsewhere on Hereford's low ground, scored against the Pol 03 credit.
• Ground that holds water. A groundwater flood risk assessment for sites on the shallow river gravels under Hereford's Edgar Street area.
• Getting people out in time. A flood warning and evacuation plan for a site in one of the Wye's warning areas, built around the hours of notice a travelling flood gives.

Assessments for sites on either bank come from Unda Consulting Limited, a CIWEM Business Partner, and our consultants are chartered. Where a site needs a soakaway, the ground conditions and soakaway map and our drainage calculators give a first look at whether infiltration is likely to work.

Plans, defences and who to contact about Wye flooding

Flood risk on the Wye is managed jointly across the border. The Severn river basin district flood risk management plan for 2021 to 2027 is published by the Environment Agency together with Natural Resources Wales, and covers the Wye along with the Severn.

• Defences in Hereford. A riverside flood wall protects parts of the city; it was damaged in the 2019 and 2020 floods and repaired at a cost of £450,000. Beyond the wall, Bishops Meadow and the other riverside fields are left to flood, and they hold water that would otherwise go downstream.
• Defences at Hampton Bishop. Earth banks along the Wye and the Lugg protect about 150 homes and businesses; the Lugg bank was overtopped in 2020 and repaired for £90,000.
• Regional committee. The English Severn and Wye Regional Flood and Coastal Committee approves flood schemes on the English side.
• Warnings. Sign up for Environment Agency flood warnings for an English address or Natural Resources Wales warnings for a Welsh one; Floodline on 0345 988 1188 covers both.
• Councils. Powys County Council, Herefordshire Council, Gloucestershire County Council and Monmouthshire County Council take reports of flooding from surface water and ordinary watercourses on their stretch; Herefordshire supports community flood groups and trained volunteers who close minor roads in a flood.
• Emergency planning. The Dyfed-Powys, West Mercia, Gloucestershire and Gwent Local Resilience Forums plan the emergency response along the river, from the Welsh hills to the estuary.
• Sewers and emergencies. Dŵr Cymru Welsh Water runs the public sewers across most of the catchment. In an emergency, call 999 if life is at risk, and 105 for a power cut.

River Wye flooding: questions people ask

Whether the site is in Powys, Herefordshire, the Forest of Dean or Monmouthshire, call 01293 214444 or email enquiries@unda.co.uk, and our consultants will tell you which report the council, a lender or an insurer is likely to want. The rivers we cover are listed river by river.