Heavy rain causes flooding in the south-western county of Somerset
In early May 2023, more than two weeks’ worth of rain fell in a few hours and turned roads to rivers in the south-western English county of Somerset (BBC, 2023). Disruption also affected travel networks and brought damage to homes and businesses in other parts of the country, including Devon, Essex and Northamptonshire, but the worst effects of flash flooding were experienced in rural Somerset (Guardian, 2023).
Event overview
Heavy rain began on Tuesday 9 May 2023, leading to localised surface water flooding which blocked roads and bridges and affected properties. The town of Yeovilton in Somerset recorded 35.8mm of rain in a single day, over half the average monthly amount for May of 62.5mm (BBC, 2023).
Figure 1: Satellite-observed rainfall animation showing 24-hour rainfall accumulations between 7 May 2023 and 11 May 2023. Rainfall data source: NASA GPM, 2023. Animation produced by JBA Risk Management, 2023.
River levels rose rapidly, with the River Cam reaching 2.85 metres close to the village of North Cadbury, one of the worst affected areas; the Environment Agency state that property flooding is possible at that location at 0.6 metres and above. A similar story in Newton Poppleford saw flood levels of 1.4 metres exceeded on 9 May with the River Otter reaching 1.55 metres (Floodlist, 2023).
Somerset Council declared a major incident on the Tuesday evening, although this had been stood down by 2am on Wednesday morning. The council reported that over 40 homes and 18 businesses in North Cadbury, Queen Camel and Milverton had been affected, but these numbers were expected to rise as more reports come in (Somerset.gov.uk, 2023).
Mudslides were also reported, blocking roads and leading to the village of Queen Camel becoming cut off for several hours. Homes were evacuated in North Cadbury, with floodwaters reaching an estimated 1.2 metres in the village (Telegraph, 2023).
As the rain swept north and east across the country through Tuesday evening, flash flooding caused blocked roads and delays for drivers and rail passengers in areas of Hertfordshire, Northamptonshire and Essex (Guardian, 2023).
Active flood warnings were still in place on the River Cam, River Brue and Glastonbury Millstream on Wednesday 10 May although no further heavy rain was forecast for affected areas (ITV, 2023).
After the major incident was stood down, Somerset Council pledged to work with communities across the county to improve flood resilience, but warned that extraordinary weather events such as this would continue to threaten to cause serious damage in the area (BBC, 2023).
Figure 2: JBA’s 5m-resolution river flood hazard maps for a return period of 20 years at (a) North Cadbury and (b) Queen Camel in Somerset, UK. The green circles depict locations known to have flooded during the May 2023 floods.
Somerset: an area of concern
Flooding is a major threat to people and property in Somerset, with high annual rainfall and low-lying land causing problems for local communities and farmers. Much of the county is below sea level, which makes it an area of concern for policy makers (Sky, 2023).
In the winter of 2013/14 much of the Somerset Levels spent months underwater, with villages cut off, power cuts and agriculture coming to a standstill. It was estimated at the time that farmland might take up to two years to ‘dry out’ and become usable again (BBC, 2014).
The towns of Chard and Ilminster were flooded in 2021, when drainage systems were overcome by heavy rain in June and October. This is of particular concern as new housing is often being built in areas at risk to flood (BBC, 2021).
Flooding returned to the Somerset Levels in January 2023, with farmers concerned at how fast the waters had risen – up to flood level in six days compared to the month it had taken water to flood the same fields in 2014 (BBC, 2023b). Heavy rain had caused the overflowing of spillways, forcing excess water onto moorland and agricultural land (Floodlist, 2023b). The Environment Agency responded with “enhanced pumping” in affected areas, but the fact that a major incident was declared in the county twice in five months means that the council are having to look at taking more action to deal with future flooding (BBC, 2023a).
Last year a tidal barrier was approved to be built at Bridgewater, in the north of the county. This will be one of the England’s biggest flood defence schemes, protecting residents and businesses from coastal flooding – another big threat to the region – but the barrier may not be operational until 2027 (BBC, 2022).
To understand both current and future flood risk, it's important that businesses act now. Alongside cutting-edge climate change data, JBA offers probabilistic modelling and high-resolution hazard maps for all major flood types in the UK. For more details, get in touch with the team at JBA.
References
BBC, 2014. Somerset floods crisis: How the story unfolded. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-somerset-26157538 [Accessed 12 May 2023]
BBC, 2021. Somerset flood prevention should be high priority. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-somerset-59986914 [Accessed 12 May 2023]
BBC, 2022. Bridgewater tidal barrier: One of England’s biggest flood defences approved. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-somerset-60124245 [Accessed 12 May 2023]
BBC, 2023a. Somerset flash flooding: Investigation after heavy rain hits county. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-somerset-65547308 [Accessed 12 May 2023]
BBC, 2023b. Major incident declared due to Somerset flood risk. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-somerset-64315643 [Accessed 12 May 2023]
Floodlist, 2023a. UK - Evacuations After Flooding in Devon and Somerset. [Online]. Available at: https://floodlist.com/europe/united-kingdom/floods-devon-somerset-may-2023 [Accessed 12 May 2023]
Floodlist, 2023b. UK - Government Declares Major Incident Over Flood Risk in Somerset. [Online]. Available at: https://floodlist.com/europe/united-kingdom/flood-risk-somerset-levels-january-2023 [Accessed 12 May 2023]
Guardian, 2023. Somerset: major incident declared after flash flooding. [Online]. Available at: https://www.theguardian.com/environment/2023/may/10/somerset-major-incident-declared-after-flash-flooding [Accessed 12 May 2023]
ITV, 2023. Latest on today’s flooding in Somerset and Devon as major incident declared. [Online]. Available at: https://www.itv.com/news/westcountry/2023-05-10/major-incident-declared-flash-flooding-hits-parts-of-somerset [Accessed 12 May 2023]
NASA Global Precipitation Measurement (GPM), 2023. Precipitation Data Directory. [online] Available at: https://gpm.nasa.gov/data/directory [Accessed 15 May March 2023]
Sky, 2023. UK weather: Somerset flood risk ‘concern’ triggers Environment Agency major incident. [Online]. Available at: https://news.sky.com/story/uk-weather-somerset-flood-risk-concern-triggers-environment-agency-major-incident-12789388 [Accessed 12 May 2023]
Somerset.gov.uk, 2023. Flooding update - 10 May. [Online]. Available at: https://www.somerset.gov.uk/flooding-update-10-may-2023/ [Accessed 12 May 2023]
Telegraph, 2023. More storms predicted after South West hit by flash floods and mudslides. [Online]. Available at: https://www.telegraph.co.uk/news/2023/05/10/somerset-flash-floods-mudslides-major-incident-uk-weather/ [Accessed 12 May 2023]
