River Dart Flooding & Flood Risk

The River Dart is a Dartmoor river, and that shapes almost everything about how it floods. It gathers rain off some of the highest, wettest ground in southern England, funnels it down through steep wooded valleys, and delivers it to the low-lying towns strung along its course in a matter of hours. From Buckfastleigh and Staverton to the tidal quays of Totnes and the estuary at Dartmouth, the communities beside the Dart face flooding from two directions at once: the river charging down off the moor, and the tide pushing up from the sea. Unda prepares flood risk assessments, drainage strategies and related reports for sites across the Dart catchment and its floodplain. To talk a site through, call 01293 214444 or email enquiries@unda.co.uk.

On 27 December 1979 the River Dart reached 4.41 metres at the Austins Bridge gauge near Buckfastleigh, still its highest level in a record that runs back to 1958, and the growing risk of fluvial and tidal flooding at Totnes has since justified a £3.8 million defence scheme protecting more than 400 homes and businesses.

• A flashy moorland river. The Dart drains around 475 square kilometres of Dartmoor and south Devon, and steep, wet, fast-shedding upland means it rises quickly and peaks hard after heavy rain.
• Fluvial above Totnes, tidal below it. The river is fresh and fast down to Totnes Weir, then becomes a tidal ria all the way to Dartmouth, so the towns face river flooding, tidal flooding, or both together.
• A designated Main River. The Environment Agency regulates the Dart, so the 8 metre byelaw margin and Flood Risk Activity Permits apply to work near it.
• Real development pressure. From Buckfastleigh and Totnes to Dartmouth and Kingswear, sites in and near the floodplain almost always need a flood risk assessment for planning.

Check flood risk along the River Dart

The map below draws the River Dart in coral, with the Environment Agency’s live river gauge at Austins Bridge positioned on it — click the pin 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.

Why does the River Dart flood?

The River Dart floods because of where it starts. Its two headwaters, the East Dart and the West Dart, rise on the high northern plateau of Dartmoor (the East Dart near Cranmere Pool at around 510 metres, the West Dart below Lower White Tor at around 450 metres) and meet at Dartmeet, 210 metres up, before the combined river drops away to the sea over roughly 75 kilometres. That is a steep, short journey off high moorland, and the ground it drains is the problem: thin peaty soils over granite, already wet for much of the year, that shed rain almost as fast as it lands. Dartmoor is one of the wettest places in the south of England, and when a wet Atlantic system parks over the moor, the runoff has nowhere to soak away.

The result is a classic flashy river. Water reaches the channel quickly, so the Dart can go from placid to raging in a few hours, and the whitewater kayakers who prize the upper reaches from Dartmeet down to Buckfastleigh are reading the same rapid rises that put the towns downstream at risk. The single long-term gauge on the main river, at Austins Bridge near Buckfastleigh, has been recording since 1958 and drains a catchment of about 247 square kilometres at that point; its average flow is a modest 11 cubic metres per second, but its record stands at 4.41 metres, set in the December 1979 flood. Tributaries such as the Webburn, the Mardle and Dean Burn add their own quick responses lower down, concentrating yet more runoff into the valley through Buckfastleigh. It is the behaviour behind the annual flood probabilities a planning assessment has to work with.

• High, wet headwaters. The East and West Dart rise above 450 metres on Dartmoor and join at Dartmeet, giving the river a steep drop and a fast response to rain.
• Ground that sheds rain. Thin soils over granite, often already saturated, produce rapid runoff rather than soaking rainfall away.
• One long gauged record. The Environment Agency has gauged the Dart at Austins Bridge, Buckfastleigh, since 1958, the longest flow record in the catchment, with a peak of 4.41 metres in December 1979.
• Tributaries pile in. The Webburn, Mardle and Dean Burn feed the river through the Buckfastleigh reach, adding their own flashy peaks to the main flow.

Where the river meets the tide: Totnes and the estuary

Totnes is where the River Dart changes character. At the seventeenth-century weir just above the town, rebuilt in the 1960s, the fresh, fast-flowing river meets the tide, and from there down to the sea it is a drowned valley, a ria, deep and tidal with no bridges below the town. That transition is exactly why flood risk at Totnes is harder to manage than anywhere else on the river. The Environment Agency describes the risk to the town as both fluvial and tidal, and the two can arrive together: a big flow coming off the moor meeting a high spring tide backing up the estuary, each stopping the other from draining away. You can watch the tide on the Environment Agency’s Tidal River Dart at Totnes warning area.

Below Totnes the tide governs everything. The estuary winds past Stoke Gabriel, Dittisham, Tuckenhay and Bow before opening out at Dartmouth and Kingswear, and the low-lying quays, creekside lanes and waterfront properties along it flood when high tides, low pressure and onshore weather combine. That is the same tidal mechanism that puts Bayards Cove and the Dartmouth waterfront under water in the worst surges. For a site anywhere below the weir, tidal levels and their allowance for sea level rise matter far more than the river flow does, which is why a coastal or estuary site is often assessed through a flood consequence assessment rather than a purely fluvial one.

A history of flooding on the River Dart

The Dart has a long history of flooding its valley towns, and the modern record is anchored by the December 1979 event, when the river hit 4.41 metres at Austins Bridge, the highest level ever gauged there. Totnes has come close to serious flooding on a number of occasions since, which is what prompted the Environment Agency to act on its scheme to reduce flood risk in Totnes. A flood defence scheme was first built in 1980, but improved hydrology, taking account of climate and land use change, showed the town still carried significant risk, in places only a 10 percent chance of flooding in any given year.

In 2017 South Hams District Council granted permission for a new £3.8 million scheme, completed in 2018, to reduce the risk to more than 400 homes and businesses. It raised the older linear defences at Broadmarsh, built new flood walls through the historic town centre (including a raised riverside wall in glass at the Bistro), replaced the failing quay wall at Steamer Quay with sheet piling, and created seven hectares of restored wetland at Queensmarsh with the Dartington Estate to hold water back. The winters since have kept the pressure on: the run of Atlantic storms through late 2025 and into 2026 dropped as much as 88 millimetres of rain on Dartmoor in a single event, sending the moorland rivers of south Devon to some of their highest levels on record. These are the events a flood risk assessment for a site near the Dart has to plan around, and they are why residual flood risk behind a defence still has to be assessed.

Which areas does the River Dart put at risk?

Flooding on the Dart is concentrated on the valley floor and the estuary edge, and the Environment Agency runs a formal warning service the length of the river. A catchment-wide flood alert area, the “River Dart area”, covers the whole system from the moor to the sea, taking in Totnes, Ashburton, Buckfastleigh, Dartmouth and Torbay. Inside it, more precise flood warning areas cover the reaches where the Agency can warn individual properties, running from Dartmeet down to Buckfastleigh, from Buckfastleigh to Totnes including Staverton, the tidal river at Totnes itself, and the low-lying areas of the Dart estuary below the town. 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 county is covered on our Devon flood risk page, with nearby coastal towns on our Dawlish, Paignton and Exeter pages.

Is the River Dart a Main River, and what that means for your site

Yes. The River Dart is a designated Main River along its length, which matters a good deal if you are developing near it. Main River status means the Environment Agency, rather than the local council, is the regulator for the channel and its immediate margins. Works within 8 metres of the top of the bank generally need a Flood Risk Activity Permit from the Environment Agency before they start, sought alongside planning permission rather than instead of it, and a site in the river’s floodplain will normally need a flood risk assessment to support its application. The many smaller streams and ditches feeding the Dart are a mix of main river and ordinary watercourses, the latter regulated by Devon County Council as Lead Local Flood Authority and by the riparian owners whose land they cross. On the upper reaches the Dartmoor National Park Authority is the planning authority, while South Hams and Teignbridge cover the towns downstream, so getting the right classification and the right authority clear at the outset saves time later. Work in or near an ordinary watercourse can also need ordinary watercourse consent.

• The 8 metre byelaw margin. Building, excavation or structures near the Dart usually require a Flood Risk Activity Permit, sought alongside 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.
• Tidal or fluvial, know which. Above Totnes Weir the risk is river flow; below it, tidal levels and sea level rise dominate. The right allowances depend on which you are in.
• Know your authority. Environment Agency for the main river, Devon County Council for ordinary watercourses and surface water, with Dartmoor National Park, South Hams or Teignbridge deciding the planning application.

What flood risk on the River Dart means for a nearby development

If your site sits near the Dart, the flood risk work follows from where it is on the river. Above Totnes the question is how high the river gets in a flood, allowing for climate change, and how to raise floor levels and manage access so the development stays safe without pushing flood risk onto neighbours. Below the weir the question shifts to tidal levels and the generous sea level rise allowances that now apply over a development’s lifetime. Either way, a site in Flood Zone 2 or 3 needs a site-specific flood risk assessment for planning, and where the national mapping is too coarse, which is common right beside a Main River like the Dart, hydraulic flood modelling can pin down accurate levels and extents. Sites that fall in the higher-risk zones may also need a sequential test to justify their location, may have to provide compensatory flood storage, and must show their surface water drainage will not make matters worse on ground that already sheds water fast. If you are not sure whether your site needs one at all, our guide on when you need a flood risk assessment is a good place to start.

Flood risk and drainage services for sites near the River Dart

A development near the River Dart 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 there at all, and where the surface water goes. Unda prepares each of them for sites across the Dart 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 manage runoff on steep, fast-shedding ground and meet the discharge limits set by the Lead Local Flood Authority. 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 is in play.

Where national mapping is not enough, 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. For sites below Totnes we build the tidal and sea level rise allowances into a flood consequence assessment, and everything we do is framed by the NPPF and its planning practice guidance. Report types stay distinct: modelling and groundwater work sit within a flood risk assessment, while the sequential test and the drainage strategy are separate documents in their own right. If budget is your first question, see our guide on how much a flood risk assessment costs.

Managing flood risk on the River Dart: policy and contacts

Several bodies share responsibility for flood risk on the Dart, and it is worth knowing who does what. The river sits within the South West River Basin District. The Environment Agency regulates the Main River, publishes the flood map for planning and issues the flood warnings; Devon County Council is the Lead Local Flood Authority for surface water, groundwater and ordinary watercourses; and Dartmoor National Park, South Hams District Council and Teignbridge District Council are the planning authorities along the river, each with its own strategic flood risk assessment. The £3.8 million Totnes scheme shows what that partnership looks like on the ground.

• Live river levels. Check the Dart’s gauge on the National River Flow Archive and the Environment Agency service, or use our own live river levels map.
• Screen a location. Try our free flood risk map and, for drainage design, the drainage calculators, the BRE 365 infiltration calculator and the ground conditions checker.
• Flood warnings. Sign up for Environment Agency flood warnings and call Floodline on 0345 988 1188.
• 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 Dart

Unda understand how a Dartmoor river like the Dart behaves in flood, and what the planning system and the Environment Agency expect from the reports that follow. We know how fast this river responds to rain off the moor, where the fluvial risk gives way to the tide at Totnes, and how the estuary reaches below the weir behave on a high spring tide. We prepare assessments and drainage strategies for developers, planning consultants, architects, agents and homeowners with sites the length of the valley, from Buckfastleigh to Dartmouth. Buyers and owners can also read our guide to checking flood risk before buying a property, and on why a flood map is only a starting point.

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

River Dart flood risk: your questions answered