Remnants of Hurricane Lee cause flooding in South and Mid Wales

The remnants of Hurricane Lee, which had already caused impacts in Bermuda, the United States and Canada, brought high winds and bands of heavy rain that caused flooding of roads and disruption in Swansea, Carmarthenshire and Powys on 20 September 2023, according to Natural Resources Wales¹. At Clydach in the Tawe valley, the river Clydach peaked at 4.16m and led to flooding of the Mond Valley Golf club and the Vardre RFC pitches and buildings¹.

The report records the event as an unnamed storm in its summary of notable flooding during the financial year from April 2023 to March 2024¹. It gives no figure for the number of properties affected in September 2023, and no estimate of damage has been reported¹.

The same annual report sets the event in a wetter year. It states that for the period from April 2023 to March 2024 there were 12 named storms, and that more flood alerts were issued during 2023/24 than in any of the previous three years¹. It also cites Met Office analysis that there was 20% more rainfall, and that rainfall was 15% more intense, due to climate change, and that the period October 2023 to March 2024 was the second wettest winter ever in the UK¹.

Later storms in the same year brought wider flooding. 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 Powys, with a severe flood warning issued for Llandrinio, Powys¹. During Storm Henk on 2 January 2024, Natural Resources Wales issued a total of 30 Flood Warnings and 40 Flood Alerts across Wales¹.

Why it matters for households

Natural Resources Wales estimates that 272,817 properties in Wales are at risk of flooding, approximately 1 in 7 properties, and that as of April 2024 the undefended sum of properties at risk is 340,046¹. The agency describes its network of flood defences as benefiting 102,000 properties across Wales, and says that during the winter storms the defences prevented flooding in many areas¹. Households in the areas named in the September 2023 event, Swansea, Carmarthenshire and Powys, can check current river and surface water risk through the Wales: Natural Resources Wales Warnings and Risk Maps page, and the differences between river, sea, surface water and groundwater flooding are set out in Types of Flooding: River, Sea, Surface Water and Groundwater. The three levels of message used by the agency are explained in Flood Alerts, Flood Warnings and Severe Flood Warnings, and practical preparation is covered in Flooding: A Household Guide.

What happens next

The annual report records that Natural Resources Wales made significant progress on the development of a new and updated Flood Warning Service, which it says will enter operation in the summer, and that work on replacing its Flood Warning System and Telemetry system continued¹. It published its updated Flood Risk Management Plan in November 2023, setting out priorities for the next six years, and in January 2024 published a report on the level of investment required in flood defences to manage Wales' future flood risk from rivers and the sea¹. The report also records the completion of a flood alleviation scheme in Ammanford, Carmarthenshire, that protects 223 properties¹.