Research and analysis

Groundwater situation: Sussex, 18 December 2024

Updated 20 December 2024

Applies to England

Current situation

Above average rainfall has been recorded in Sussex this autumn. The end of September 2024 was particularly wet, when more than twice the average rainfall was measured. December has been a little drier than normal, so far.

Groundwater levels in Sussex are roughly average for the time of year. In some locations, groundwater is a little higher than average for the time of year. However, no groundwater flood impacts are thought to be currently occurring.

Graph showing changes in groundwater levels in Compton Borehole in West Sussex from October 2022 to December 2024. The graph shows that groundwater levels are currently about average.

Graph showing changes in groundwater levels in Ladies Mile Borehole near Brighton from October 2022 to December 2024. The graph shows that groundwater levels are currently about average.

Weather forecast

Rainfall is forecast Wednesday evening 18 December 2024. Followed by showers in the five days that follow.

Long term weather forecasting is extremely difficult. There remains uncertainty and predictions might change, but currently, unsettled conditions could continue through the end of December and into January, although the south of the UK possibly could experience less rain than the north.

Forecast risk of flooding

We predict that groundwater will rise in all boreholes across Sussex, but not far, and not enough to generate immediate groundwater flood impacts. However, if unsettled weather and periods of rain occurs into and through January, then minor groundwater flood impacts could be possible around mid January 2025. With impacts including small amounts of water in fields, on roads, and in a small number of basements. Potentially in groundwater communities in Sussex; Lavant Valley, Ems Valley, Patcham, Lewes, and Newhaven.

It is very difficult to accurately predict the weather weeks or months ahead. The exact groundwater response will depend on the amount, intensity and distribution of any rainfall that occurs. If we experience persistent or large volumes of rainfall over the festive period, then groundwater flood impacts could occur sooner.

Next update

We will update this groundwater situation document by 17 January 2025, or sooner if the risk of groundwater flooding significantly increases. When in force, groundwater Flood Alerts are updated with information more frequently.

What we are doing

We continue to monitor groundwater levels and their response to rainfall.

Throughout autumn and winter, we will update this groundwater situation and our groundwater Briefing Notes.

We will issue and update flood alerts when there is risk of flooding affecting property.

We liaise with the local authority and other responding partners to ensure they are aware of the situation.

Our operational staff will remove blockages from main rivers, to ensure they flow freely.

Actions and advice

Think and prepare now for what you’ll do if flooding occurs where you live, don’t wait until flooding happens.

Call Floodline on 0345 988 118 or visit check for flooding to find out if you can register to receive free flood alerts for flooding from groundwater.

Look for data in your area:

• groundwater data
• river, sea, groundwater and rainfall levels

There is practical advice on what to do before, during and after groundwater flooding, and further guidance about groundwater flooding, how it might affect you and what to do.

Prepare a personal flood plan or community flood plan to help you and your community decide what practical actions to take before and during a flood, which will help reduce the damage flooding could cause.

Check pumps and any other flood protection equipment you have. Ensure valuables are moved from basements and other low parts of properties.

Where safe to do so, communities may wish to check and ensure there are no blockages in local watercourses and ditches.

Further information

You can view:

• daily groundwater levels compared to average and maximum, with indicative impact thresholds
• sub daily groundwater levels on Gaugemap
• the latest flood alert information
• water situation reports

More detailed groundwater briefing notes are emailed as part of the flood alert service. See contacts section below to register your email address.

Contacts

For more information on the flood alert service and to find out what messages you are registered to receive, call Floodline on 0345 988 118.

Alternatively, you can contact the following for additional information:

• Environment Agency Customers and Engagement: ssdenquiries@environment-agency.gov.uk
• Environment Agency Incident Reporting Hotline: 0800 807060
• Environment Agency National Customer Contact Centre: 03708 506 506