Storm Isha brings 90mph winds and heavy rain to Wales

Storm Isha brought winds as strong as 90mph and very wet weather to Wales on 21 and 22 January 2024, according to Natural Resources Wales (NRW), which issued 6 Flood Warnings and 36 Flood Alerts at the peak of the storm¹. Roads were flooded in North Wales, along with much disruption caused by the strong winds¹.

The high ground of North Wales received 50mm of rainfall widely and in places over 100mm¹. NRW reports that the flood risk posed by Storm Isha was diminished because it arrived after a fortnight of cold and dry weather¹. The figures are given in NRW's flood risk management annual report for 2023 to 2024, which covers the financial year from April 2023 to March 2024¹.

The storm sat within a wetter than usual year. NRW records 12 named storms in the period from April 2023 to March 2024, against none in 2022/23, and says more flood alerts were issued during 2023/24 than in any of the previous three years¹. The period from October 2023 to March 2024 was the second wettest winter ever in the UK, according to the Met Office¹. NRW also cites Met Office analysis that there was 20% more rainfall, and that rainfall was 15% more intense, due to climate change¹.

For comparison with other storms in the same year, NRW reports that Storm Henk on 2 January 2024 led to a total of 30 Flood Warnings and 40 Flood Alerts across Wales, and that Storm Babet, from 18 to 21 October 2023, triggered 46 flood warnings of varying levels in a 48-hour period and led to the flooding of approximately 160 properties in Conwy, Denbighshire, Flintshire, Wrexham and Powys¹. During Storm Ciaran, NRW says the advice it gave led to the safe and successful evacuation of over 900 people as flood waters inundated the Kiln Park Holiday site in the Tenby area¹.

Why it matters for households

NRW estimates that 272,817 properties in Wales are at risk of flooding, approximately 1 in 7 properties, and gives the undefended sum of properties at risk as 340,046 as of April 2024¹. Its network of flood defences benefits 102,000 properties across Wales, and NRW says these defences did their job in helping to reduce the risk for thousands of people during the storms of 2023/24¹.

The report sets out how warnings reach households in Wales. NRW monitors and responds to floods 24 hours a day, 365 days a year, tracking forecasts, issuing warnings, posting information on its website and supporting other incident responder organisations¹. Flood Warnings and Alerts for Wales are issued by NRW, and the site's guides explain the difference between Flood Alerts, Flood Warnings and Severe Flood Warnings and how Natural Resources Wales warnings and risk maps for Wales work. NRW also reports improvements to its flood forecasting service and hydrometric network, and says its new and updated Flood Warning Service will enter operation in the summer¹.

What happens next

NRW says it made significant progress on the development of its new and updated Flood Warning Service, which will enter operation in the summer¹. It published its updated Flood Risk Management Plan in November 2023, setting out its priorities for managing flood risk for the next six years¹. In January 2024 it published a report on the level of investment required in flood defences to manage Wales' future flood risk from rivers and the sea¹. NRW also reports the completion of a flood alleviation scheme in Ammanford, Carmarthenshire, that protects 223 properties, and that a further 824 properties directly benefited from capital maintenance work¹. The report states that a further phase of work "will begin during May 2024"¹.