UK suffers widespread damage caused by Storm Henk
The beginning of the new year saw Storm Henk cause severe disruption across southern Britain. The eighth storm of the UK winter season, Henk brought severe weather to southern and central parts of England and Wales (Met Office, 2024). Intense winds and heavy rain led to toppled trees and flooding, blocking roads, bridges and rail lines as thousands of households suffered power cuts (Guardian, 2024a). Two people are known to have died due to adverse weather conditions. More than 500 flood warnings were issued in various parts of England and Wales (Guardian, 2024b). Major rivers including the Severn, Avon, Thames and Trent flooded with the Environment Agency reporting 2,200 properties damaged (EA, 2024) causing an estimated £150 million insured losses, according to PwC (Reuters, 2024).
Meteorological overview
The Met Office named an area of low pressure crossing southern UK as Storm Henk on 2 January 2024. It brought strong wind gusts of up to 80 mph to south-west England and Wales. The area of low pressure moved northeastwards by the evening of 2 January 2024 bringing gusts of up to 70 mph to southern England and the Midlands.
Storm Henk followed a period of sustained wet weather over the course of winter 2023. The most recent prior storm, Storm Gerrit, which lasted from 27-28 December, brought 30-50mm of rainfall to much of northern England, Wales, Scotland and Northern Ireland (MetOffice, 2023) meaning that soils were already saturated ahead of Storm Henk (NASA, 2024b). In the first four days of 2024, Storm Henk brought an additional 30-50mm of rainfall to these already saturated soils, with 50mm reported widely across areas of Wales and parts of southern England (Met Office, 2024).
Figure 1 highlights rainfall accumulation over the first seven days of 2024. As shown, most of the extreme accumulation is concentrated along the coastal areas of England and Wales. The Midlands, as well as areas of Wiltshire and Gloucestershire, received high rainfall accumulation over the seven-day period. The River Trent catchment area, that runs through Birmingham, Leicestershire and Nottinghamshire, received particularly extreme accumulations, and this is reflected in the high impact flooding seen in these areas.
Figure 1: (Left) 7-day accumulated rainfall totals from 1 to 7 January 2024. Rainfall data source: NASA GPM, 2024. (Right) Satellite-observed rainfall animation showing Storm Henk’s coverage between 01 and 06 January 2024. Rainfall data source: NASA GPM 3-hour rainfall accumulation (2024a). Animation produced by JBA Risk Management (2024).
River flow return period analysis
JBA conducted Extreme Value Analysis on historic streamflow data to estimate the return period of Storm Henk. The exceedance probability of streamflow on the River Trent at North Muskham was calculated using daily mean watercourse discharge data from the National River Flow Archive (NRFA, 2024). The 56-year time series was fitted with a generalised Pareto distribution to produce an exceedance probability curve (Figure 2). The curve is shown by the solid orange line and the dashed lines represent the 95th percentiles. A streamflow of 742 cubic meters per second on 5 January corresponds to a return period of 15 years. The River Leam, at Princes Drive Weir, Leamington Spa, Warwickshire experienced a streamflow of 71 cubic meters per second on 3 January 2024, corresponding to a return period of 25 years.
Figure 2: Return period estimate for river flows on the River Trent on 5 January 2024 and River Leam 3 January 2024.
Impacts
Despite the wet antecedent conditions, high rainfall and record, or close to record levels, across the rivers Trent, Thames, Severn and Avon, property impacts were limited. The Environment Agency reported that 102,000 properties were protected from flooding in England with over 12 kilometres of temporary and semi-permanent defences installed to protect communities (EA, 2024). NRW reported that 73,000 properties were protected in Wales during Storm Gerrit and Henk (NRW, 2024). Still, many areas are not protected, either because investment in flood defences is not seen as being cost effective or because they act as a flood storage area limiting impacts elsewhere.
Across Nottinghamshire, Colwick, Mansfield Woodhouse, Worksop, Sawley, Newark on Trent and Wilford saw widespread flooding with many roads and commercial properties flooded. More than 300 homes and businesses were flooded around Leicester, Leicestershire and Rutland as a result of rivers and canals bursting their banks (Leicestershire County Council, 2024). Along the rivers Avon, Severn and Thames, wide areas of floodplain were inundated, with isolated homes and those immediately adjacent to watercourses flooded together with numerous sports and recreational facilities. Thousands of acres of crops were submerged due to the storm. Affected farmers urged the government to bolster flood defences in rural regions (BBC, 2024) while others called for a compensation scheme reflecting their role as flood storage.
Elsewhere heavy rainfall did cause widespread surface water flooding. In Lincolnshire, a typical month’s worth of rain fell in three days, causing hundreds of properties to be flooded, mainly between Bourne and Sleaford. Cranwell saw 44.8mm of rain whilst Holbeach and Hull East Park witnessed 38.44mm and 36.2mm respectively (BBC, 2024d). On 4 January heavy rainfall caused widespread surface water flooding in Oxfordshire, with properties impacted in Abingdon, Steventon and Botley. In Wiltshire, Marlborough sustained the brunt of the damage, resulting in urgent action from the town council (Gazette and Herald, 2024). Over 500 people were hit by power cuts across the county (Wiltshire Times, 2024).
Winter 2023-2024 UK storm season
In the United Kingdom, a storm receives a name when it poses the risk of causing disturbance or harm due to powerful winds, substantial rainfall, or snowfall, prompting amber or red weather warnings to be issued. UK storms bring heavy rainfall that can lead to flooding. The UK is renowned for its stormy weather, and the jet stream plays a crucial role. This high-altitude band of strong winds, located around 8-11 km above the Earth's surface and blowing from west to east, guides weather systems, including storms, across the Atlantic to reach the UK (NCAS, 2024). The position of the jet stream can be influenced by numerous factors, however the El Niño event in the tropical Pacific is likely affecting the east Atlantic storm season. El Niño’s influence typically causes a stormy autumn and early winter but come late winter, the weather is usually calmer and colder (Harvey, 2024).
Since the initiation of the current naming scheme in 2015, the UK typically experiences up to nine named storms each winter. As of January 2024, there have already been eight named storms, marking the highest count within this timeframe.
Table 1: Storms that have affected the UK during the 2023/2024 winter storm season.
JBA flood hazard maps
JBA offers national 5m resolution river, surface water and coastal storm surge flood hazard maps for the UK. We have developed a flood event footprint for Storm Henk based on our hazard maps. Figure 3 shows that JBA’s storm river and surface water flood event footprints capture areas known to have flooded as a direct result of the Storm Henk.
Figure 3: Detailed view of Loughborough and Oxford, UK, from JBA’s 5m Storm Henk Flood Event Footprint. Base map: © Mapbox © OpenStreetMap Improve this map.
JBA’s flood footprint for Storm Henk details extents and depths of the flooding in areas affected. Download it via our Client Portal or request a copy by emailing eventresponse@jbarisk.com.
References
BBC, 2024a. Storm Henk-hit farmers call for stronger river defences. [Online]. Available at: https://www.bbc.co.uk/news/science-environment-67877086 [Accessed 11 January 2024]
BBC, 2024b. Widespread disruption as Storm Henk hits Northamptonshire. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-northamptonshire-67864452 [Accessed 11 January 2024]
BBC, 2024c. Storm Henk: Warning of more West Midlands flooding after heavy rain. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-hereford-worcester-67861072 [Accessed 11 January 2024]
BBC, 2024d. Properties in Lincolnshire flooded after Storm Henk sweeps county. [Online]. Available at: https://www.bbc.co.uk/news/uk-england-lincolnshire-67861999 [Accessed 11 January 2024]
EA, 2024. More than 102,000 properties protected during Storm Henk and recent flooding. [Online]. Available at: https://www.gov.uk/government/news/january-flooding-in-england [Accessed 16 January 2024]
Floodlist, 2024. UK – Evacuations and Rescues After Storm Henk Leaves Widespread Flooding. [Online]. Available at: https://floodlist.com/europe/united-kingdom/storm-henk-floods-january-2024 [Accessed 11 January 2024]
Gazette and Herald, 2024. Storm Henk: Marlborough flooding update on recovery effort. [Online]. Available at: https://www.gazetteandherald.co.uk/news/24032159.storm-henk-marlborough-flooding-update-recovery-effort/ [Accessed 11 January 2024]
Guardian, 2024a. Storm Henk hits Britain, blocking roads, bridges and rail lines in south. [Online]. Available at: https://www.theguardian.com/uk-news/2024/jan/02/met-office-uk-weather-warning-storm-henk-britain [Accessed 11 January 2024]
Guardian, 2024b. Storm Henk leaves flooded homes and roads across England. [Online]. Available at: https://www.theguardian.com/uk-news/2024/jan/04/uk-weather-woman-dies-car-hits-fallen-tree-storm-henk [Accessed 11 January 2024]
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Harvey, B. (2024) Why was autumn 2023 so stormy in the UK? [Online]. Available at: https://ncas.ac.uk/uks-2023-24-storm-season-what-causes-storms-and-are-they-getting-worse/ [Accessed 16 January 2024]
Leicestershire County Council, 2024. Leaders call on Government to release funding to help residents. [Online]. Available at: Leaders call on Government to release funding to help residents | Leicestershire County Council [Accessed 16 January 2024]
Leicester Mercury, 2024. Downpours and flooding as Storm Henk wreaks havoc on Leicestershire. [Online]. Available at: https://www.leicestermercury.co.uk/news/local-news/leicestershire-weather-live-updates-county-9008523 [Accessed 11 January 2024]
Met Office, 2023. Storm Gerrit, 27 to 28 December 2023. [Online]. Available at: https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2023/2023_12_storm_gerrit.pdf [Accessed 16 January 2024]
Met Office, 2024. Storm Henk, 2 January 2024. [Online]. Available at: https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2024/2024_01_storm_henk_v1.pdf [Accessed 11 January 2024]
Metro, 2024. Couple beat Storm Henk after being flooded 11 times by building 7ft wall around house. [Online]. Available at: https://metro.co.uk/2024/01/06/couples-house-stays-dry-flooding-building-7ft-wall-20074055/ [Accessed 11 January 2024]
MSN, 2024. Flood warning around Northampton holiday park finally removed after more than a week. [Online]. Available at: https://www.msn.com/en-gb/news/uknews/flood-warning-around-northampton-holiday-park-finally-removed-after-more-than-a-week/ar-AA1mGfvz [Accessed 11 January 2024]
NASA Global Precipitation Measurement (GPM), 2024a. Precipitation Data Directory. [Online]. Available at: https://gpm.nasa.gov/data/directory [Accessed 11 January 2024]
NASA, 2024b. Flooding Along the River Trent. [Online]. Available at: https://earthobservatory.nasa.gov/images/152295/flooding-along-the-river-trent [Accessed 16 January 2024]
National River Flow Archive (NRFA), 2024. Gauged Daily Flow data. [Online]. Available at: https://nrfa.ceh.ac.uk/ [Accessed 16 January 2024]
NCAS, 2024. UK’s 2023-24 storm season: What causes storms and are they getting worse? [Online]. Available at: https://ncas.ac.uk/uks-2023-24-storm-season-what-causes-storms-and-are-they-getting-worse/ [Accessed 16 January 2024]
Nottingham Post, 2024. Storm Henk: Nottinghamshire flooding as homes ‘uninhabitable’ and several roads closed. [Online]. Available at: https://www.nottinghampost.com/news/local-news/storm-henk-live-nottinghamshire-weather-9010001 [Accessed 11 January 2024]
NRW, 2024. Written Statement: Flood impacts from Storm Gerrit and Storm Henk. [Online]. Available at: https://www.gov.wales/written-statement-flood-impacts-storm-gerrit-and-storm-henk
Reuters, 2024. Storm Henk causes around 150 mln pounds in UK insured losses. [Online] Available at: https://www.reuters.com/world/uk/storm-henk-causes-around-150-mln-pounds-uk-insured-losses-pwc-2024-01-10/ [Accessed 11 January 2024]
Wiltshire Times, 2024. Storm Henk: Wiltshire power cuts affecting hundreds of homes. [Online]. Available at: Storm Henk: Wiltshire power cuts affecting hundreds of homes | Wiltshire Times [Accessed 16 January 2024]
