Storm Claudia: Impact on Monmouth – Summary of Monmouthshire County Council's Flood Investigation

Storm Claudia caused severe flooding in Monmouth in November 2025, when exceptionally heavy rainfall overwhelmed the River Monnow and existing flood defences. The event resulted in widespread damage to homes, businesses and infrastructure, prompting Monmouthshire County Council (MCC) to undertake a formal flood investigation under Section 19 of the Flood and Water Management Act 2010.

The key finding emerging from the investigation is that the volume of water passing through the Monnow catchment exceeded the capacity of the existing flood protection system. The incident has prompted a wider review of flood risk management, emergency response and future flood prevention measures.

Storm Claudia brought exceptionally heavy rainfall to south-east Wales on 14 November 2025.

The main impacts included:

• Extreme rainfall: Approximately 120mm of rain was recorded in the Monnow catchment over a period of around 28 hours.

• Record river levels: The River Monnow reached levels exceeding those recorded during Storm Dennis in 2020 and Storm Bert in 2024.

• Flood defences overwhelmed: Water overtopped existing flood defences, inundating parts of Monmouth town centre.

• Major incident declared: Emergency services and public authorities coordinated rescues, evacuations and recovery operations.

• Widespread property damage: Homes and businesses were flooded, with significant disruption to residents and local trade.

Natural Resources Wales subsequently reported that river levels reached approximately 18 times their normal level.

Areas affected

The flooding was not confined to Monmouth town centre. The wider River Monnow catchment experienced significant impacts.

Approximately 250 residential and business properties were flooded across Monmouthshire during the event, making it one of the most severe and widespread flooding incidents in the county's recent history.

What is Monmouthshire County Council's Section 19 report?

Under Section 19 of the Flood and Water Management Act 2010, a lead local flood authority must investigate flooding where it considers the incident to have had significant consequences.

MCC confirmed that it would prepare a formal investigation covering the River Monnow catchment because the flooding exceeded the threshold of 20 affected properties.

The investigation is intended to establish:

1. Which organisations had relevant flood risk management responsibilities.

2. Whether those organisations exercised their functions appropriately during the event.

3. What actions were undertaken in response to the flooding.

4. What improvements may be required to reduce future flood risk.

5. What lessons can be learned from the emergency response and subsequent recovery.

The investigation covers Monmouth, Forge Road, Rockfield and Skenfrith rather than treating each location as a separate incident.

What do the findings tell us about the flood defences?

Natural Resources Wales (NRW), which is responsible for maintaining certain flood defences, has published information about the performance of its assets during Storm Claudia.

Its assessment identified that:

• The flood defences in Monmouth were overwhelmed because the volume of water exceeded their designed level of protection.

• The defences were subsequently assessed as being fit to perform in future storms, apart from some minor surface damage.

• Minor damage was identified on the Forge Road embankment and an embankment on the Scud Brook.

• Repairs were undertaken to the Town Ditch outfall at Over Monnow.

These findings distinguish between the physical condition of the flood defences and their ability to protect the town during an exceptionally severe flood. The fact that the defences remained structurally serviceable does not mean that they prevented flooding during Storm Claudia.

What improvements are being considered?

MCC has acknowledged the need to review flood protection measures and work with Welsh Government, NRW and other organisations to develop improved protection.

The emerging approach includes several strands.

Natural flood management: The Resilient Rivers Monnow project aims to improve water storage in soils, slow runoff and reduce peak flows through catchment-scale land management. The project involves working with upstream landowners and the Wye and Usk Foundation.

Flood defence improvements: Reviewing existing defences and identifying opportunities to improve protection in locations vulnerable to overtopping.

Drainage and infrastructure maintenance: Reviewing drainage assets, watercourses, highway drainage and other local issues to identify problems before future periods of heavy rainfall.

Emergency response and communication: Reviewing lessons from the incident, including flood warnings, emergency coordination, evacuation arrangements and communication with affected communities.

Financial and community recovery: The council's recovery response included financial assistance for affected households and businesses, alongside support from Monmouth Town Council and voluntary organisations. The Monmouth Mayor's Flood Recovery Fund raised £201,023.88, with two phases of payments completed between November 2025 and March 2026. MCC also announced plans for council tax relief, business rates relief and grants to help those affected by the flooding.

Overall conclusion

Storm Claudia demonstrated the vulnerability of Monmouth to extreme rainfall events, even where established flood defences are in place.

The event exposed the limitations of relying solely on engineered flood protection when rainfall and river flows exceed the design capacity of existing infrastructure.

The Section 19 investigation is therefore important not only for establishing what happened in November 2025, but also for informing a longer-term strategy that combines improved flood defences, natural flood management, drainage maintenance and more effective emergency preparedness.

The critical outstanding question is how the findings of the final Section 19 report will translate into funded, practical measures that reduce the risk of another major flood in Monmouth.