River Tone Flooding & Flood Risk

The River Tone is really two rivers in one. Its upper catchment gathers fast off the steep, wet flanks of Exmoor and the Brendon, Quantock and Blackdown Hills, so the river rises quickly after rain; but below Taunton it slows to a crawl across the flat peat moors of the Somerset Levels, where the channel is embanked, the land lies at or below sea level, and the river can only empty into the tidal River Parrett at low water. That combination, a flashy upland catchment feeding a tide-locked lowland reach, is why the Tone has been at the centre of some of the worst flooding England has seen this century. Unda prepares flood risk assessments, drainage strategies and related reports for sites the length of the Tone’s floodplain. To talk a site through, call 01293 214444 or email enquiries@unda.co.uk.

In the winter of 2013–14, water backing up behind the tidal Parrett left around 600 homes and 17,000 acres of the Somerset Levels — including Curry Moor and Hay Moor on the lower Tone — under water for weeks, and it took 65 pumps moving 65 million cubic metres of floodwater to clear it.

• A river of two halves. Quick-responding upland tributaries off Exmoor and the Brendon, Quantock and Blackdown Hills funnel into a flat, embanked lower reach across the Levels that drains only slowly to the sea.
• A designated Main River. The Environment Agency regulates the Tone, so the 8 metre byelaw margin and Flood Risk Activity Permits apply to work near it.
• Live Environment Agency gauges. Taunton Market, Bishops Hull and Currymoor all appear on the map below, with their latest levels updating in real time.
• Real development pressure around Taunton. A strategic scheme is being built to cut flood risk to more than 1,000 properties in the town — and sites in and near the floodplain almost always need a flood risk assessment for planning.

Check flood risk along the River Tone

The map below draws the River Tone in coral, from its headwaters in the Brendon Hills to the point where it meets the River Parrett at Burrowbridge, with the Environment Agency’s live river gauges positioned along it — click a gauge to see its latest level, its typical range and its record peak. Enter a postcode near the river to zoom in and screen that location against the Environment Agency’s flood data for rivers and sea, surface water, reservoirs and the flood zones used for planning. It is an indicative screening tool, not a flood risk assessment.

Which areas does the River Tone put at risk?

Flooding from the River Tone reaches furthest on the flat ground below Taunton, and the Environment Agency runs a formal warning service for the communities along it. A catchment-wide flood alert area, the “River Tone catchment”, runs from Clatworthy Reservoir down to Currymoor and takes in the Hillfarrance Brook, the Halsewater Stream and the river’s other tributaries. Within it, tighter flood warning areas cover Taunton itself and the moors downstream, where the Environment Agency can warn individual properties. The table below sets out the main settlements at risk, from source to mouth.

If your site sits within one of these areas, the Environment Agency’s flood map for planning is likely to place it in Flood Zone 2 or 3, which triggers the need for a site-specific flood risk assessment. You can screen any address against the live Environment Agency data using the map above, and the wider picture across the county is covered on our local pages for Somerset and Bridgwater, the tidal Parrett town the Tone ultimately drains towards.

Why does the River Tone flood?

The River Tone floods because its geography stacks the odds against it. It rises at Beverton Pond in the Brendon Hills and runs about 33 kilometres, roughly 21 miles, to join the River Parrett at Burrowbridge, draining a catchment of around 414 square kilometres off Exmoor and the Brendon, Quantock and Blackdown Hills. Those uplands are steep and wet, so rain reaches the channel quickly and the river rises fast. Then everything changes below Taunton: the gradient all but disappears, the river is carried between raised banks across peat moors that lie at or below the level of the sea, and its only outlet is the tidal Parrett, which itself can only discharge to the Bristol Channel at low water. When a high tide meets a river already full, the water has nowhere to go but out across the moors.

• A steep, wet, fast-responding catchment. The Tone and its tributaries drain some of the wettest high ground in the South West, so the upper river peaks sharply after prolonged or intense rain.
• Many tributaries, concentrated into one channel. Halse Water, the Hillfarrance Brook, Broughton Brook, Haywards Water, the Sherford Stream and others all feed the Tone, gathering runoff from across the catchment into a single lowland channel.
• Reservoirs at the top, tide-lock at the bottom. Clatworthy and Luxhay Reservoirs regulate the headwaters, but the lower Tone is embanked across the Levels and can only drain to the Parrett at low tide — the defining constraint on how fast floodwater clears.
• Gauged along its length. The Environment Agency records levels at Bishops Hull and Taunton Market in and above the town, and at Currymoor out on the Levels — the reaches where flooding bites hardest.

A history of flooding on the River Tone

Taunton’s worst flood in living memory came in the 1960s, when more than 360 homes, shops and business premises were flooded in the town. Since then the defences built in response have held through several close calls: the river ran dangerously high in October 2000, when the Bishops Hull gauge reached 2.59 metres on 30 October and water came close to spilling into streets near French Weir, and again in 2007, 2009 and 2012. At Taunton Market, the highest level on record is 1.84 metres, set on 21 November 2012, against a normal range of roughly 0.82 to 1.77 metres.

The events that made national news, though, happened downstream. In the winter of 2013–14 a relentless run of storms filled the Levels faster than the tide-locked Tone and Parrett could drain them, and around 600 homes and 17,000 acres of farmland, taking in Curry Moor, Hay Moor and Northmoor, went under, with the villages of Muchelney and Thorney cut off for weeks. The response ran to 65 pumps shifting 65 million cubic metres of water, and in the aftermath an eight-kilometre stretch of the Tone and Parrett around Burrowbridge was dredged to speed the drainage. More recently, Storm Chandra in January 2026, during Somerset’s second-wettest January since records began in 1871, pushed 1.2 million cubic metres of water an hour down the Tone and Parrett catchments; around 30 square miles of low-lying land flooded and roughly 100 properties were affected, though defences and pumps kept a further 2,860 dry. These are the events an assessment for a site near the river has to reckon with.

Is the River Tone a Main River — and what that means for your site

Along most of its length, and certainly through Taunton and across the Levels, the River Tone is a designated Main River, which means the Environment Agency, rather than the local council, regulates the channel and its immediate margins. That distinction matters if you are developing nearby. Works within 8 metres of the top of the bank generally need a Flood Risk Activity Permit from the Environment Agency before they start, and a site in the river’s floodplain will normally need a flood risk assessment to support a planning application. The many smaller brooks and field ditches that feed the Tone are ordinary watercourses instead, regulated by Somerset Council as Lead Local Flood Authority and, out on the moors, by the internal drainage boards — and by the riparian owners whose land they cross. Getting that classification right at the outset saves time later.

• The 8 metre byelaw margin. Building, excavation or structures near the Tone usually require a Flood Risk Activity Permit, sought alongside — not instead of — planning permission.
• Flood zones drive the assessment. A site in Flood Zone 2 or 3, or a larger site in Flood Zone 1, needs a flood risk assessment for planning.
• Know which watercourse you are on. The Tone is Environment Agency territory; each tributary and moor rhyne is an ordinary watercourse under the Lead Local Flood Authority and the internal drainage boards. We confirm this for every site.

Flood risk and drainage services for sites near the River Tone

A development near the River Tone can call for several different reports, and it helps to be clear that they answer different questions. A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports. They often travel together in a planning submission, but they address separate things: whether the site is safe from flooding, whether the development should be located here, and where the surface water goes. Unda prepares each of them for sites across the Tone catchment.

• Flood risk assessments for planning. Site-specific assessments dealing directly with the Environment Agency’s requirements for development in the river’s flood zones. See our flood risk assessment for planning service.
• Assessments for property purchase and insurance. Independent reports for buyers, owners and lenders through our flood risk survey for property purchase and flood risk assessment for insurance.
• Drainage strategies and SuDS. Surface-water designs that meet the discharge limits set by the Lead Local Flood Authority and the drainage boards — see our sustainable drainage strategy service.
• Sequential and exception tests. Locational justification where policy requires it, through our sequential and exception test reports.
• BREEAM and groundwater. A BREEAM flood risk assessment for the Pol 03 credit, and a groundwater flood risk assessment where a high water table in the peat is in play.

Where national mapping is not enough, as it often is for sites right beside a Main River on the Levels, we can bring in hydraulic flood modelling to derive accurate flood levels and extents, and prepare the detailed scheme needed to discharge a drainage condition. Everything we do is framed by the NPPF and its planning practice guidance. The Somerset Levels are a case study in why all of this matters, set out in our article on why the Somerset Levels flood and how fluvial river flooding works.

Managing flood risk on the River Tone: policy and contacts

Several bodies share responsibility for flood risk on the River Tone, and it is worth knowing who does what. The river sits within the Parrett catchment, part of the South West River Basin District. The Environment Agency regulates the Main River, publishes the flood map for planning and issues flood warnings; Somerset Council is the Lead Local Flood Authority for surface water, groundwater and ordinary watercourses; the internal drainage boards manage the network of moor rhynes and pumping stations; and the Somerset Rivers Authority coordinates the extra work that followed the 2013–14 floods. In Taunton, the Environment Agency and the council are delivering a strategic flood alleviation scheme, including new flood-storage embankments at Longrun Meadow, designed to cut flood risk to more than 1,000 properties.

• Live river levels. Check the Tone’s gauges on the Environment Agency service — River Tone at Taunton Market — or use our own live river levels map.
• Flood warnings. Track the River Tone catchment flood alert area and the Curry Moor and Hay Moor flood warning area, sign up for Environment Agency warnings, and call Floodline on 0345 988 1188.
• Screen a location. Try our free flood risk map and, for drainage design, the drainage calculators and BRE 365 infiltration calculator. Wider catchment data sits with the Environment Agency’s Tone operational catchment record.
• In a flood emergency. Call 999 if life is in danger, and 105 for power cuts.

How Unda helps with flood risk on the River Tone

Unda understand how a river like the Tone behaves in flood — how fast the upland catchment responds to rain, why the tide-locked lower reaches across the Levels drain so slowly, and what the planning system and the Environment Agency expect from the reports that follow. We know where the floodplain bites hardest along the Taunton and Levels reaches, and what a robust, compliance-led flood risk assessment has to demonstrate to carry a development through planning. We prepare assessments and drainage strategies for developers, planning consultants, architects, agents and homeowners with sites the length of the river.

Every assessment rests on the same evidence the regulators use: the Environment Agency’s flood mapping, the river’s gauged levels and modelled flows, and the local planning policy that applies to the site. If you are working on a site near the River Tone, talk to one of our experienced flood risk consultants about what your application will need, or read more about our flood risk consultancy.

River Tone flood risk: your questions answered