Flood Risk Assessment in Exeter

A flood risk assessment in Exeter starts with the River Exe. It gathers rain from Exmoor, picks up the Culm and the Creedy just above the city, runs past the city's western and southern districts, and meets the tide below Trews Weir. Exeter Quay, St Thomas, Exwick and Marsh Barton sit low beside it. We prepare these assessments for planning applications, house purchases, mortgages and insurance, together with sequential and exception tests and surface water drainage strategies, for sites from Cowley Bridge and St Davids to Countess Wear, Heavitree and Pinhoe.

On this page Exeter means the city as the Office for National Statistics maps its built-up area, trimmed to the city council's boundary: the centre, St Davids, St Thomas, Exwick, Alphington, Marsh Barton, Heavitree, Wonford, Whipton, Pinhoe, Countess Wear and Newcourt, across the EX1, EX2 and EX4 postcode districts. Topsham, at the head of the estuary, is part of the city but has its own built-up area, so it sits outside the outline on the map; it is covered here all the same. Exeter City Council decides planning applications and Devon County Council is the lead local flood authority. The rest of the county is on our Devon page, and other places are listed among the areas we cover.

Exeter's rebuilt river defences protect more than 3,000 homes and businesses, yet the land behind them is still mapped as Flood Zone 3. The council's own flood study found the Exe could stay above its banks for more than a day, with water reaching riverside sites less than two hours after it overtops.

Call 01293 214444 or email enquiries@unda.co.uk with an Exeter address and one of our flood risk consultants will tell you which reports the site is likely to need.

Where does flood water reach in Exeter?

Exeter sits at the tidal limit of a river that drains about 1,500 square kilometres. The Exe's natural floodplain spreads south-west into lower Exwick, St Thomas and Marsh Barton, and the quay and the bottom of St Davids are low as well. Below Trews Weir the tide takes over, and the hills on either side shed rain fast onto clay that does not soak much of it up.

The flood zones on the Environment Agency's map treat the defences as if they were not there, so a defended street in St Thomas is still shown as Flood Zone 3; our guide to flood zones in England explains what each zone means for an application. The Exe is a main river through the city, so the Environment Agency, not the council, answers for it; the river as a whole, from Exmoor to Exmouth, is covered on our River Exe page. The smaller brooks are managed differently, and our note on main rivers and ordinary watercourses sets out why that matters from the first consultation.

Look up an EX1, EX2 or EX4 postcode

Enter an Exeter postcode below to see the Environment Agency's river and sea, surface water and reservoir layers for that spot; our flood risk map runs the same check anywhere in England. The coral line is the ONS built-up area named Exeter, clipped to the city boundary: it runs from Duryard and Stoke Hill in the north to Marsh Barton and Countess Wear in the south, and east to Pinhoe and Newcourt. Topsham, and the edges of Alphington, Ide and Sowton that lie in neighbouring districts, fall outside it.

Fourteen gates and a lowered channel: how the Exe is held back

Exeter's defences come in two generations. The first followed the floods of October and December 1960 and was built between 1965 and 1977. The second, a joint project of the Environment Agency, the city council and the county council, rebuilt them from 2014 and was finished in 2022.

• The relief channels of 1965 to 1977. After the 1960 floods, relief channels were cut beside the river at Exwick, running past St Davids station, to carry flood flows past the city.
• Phase 1 at Trews Weir, 2014 to 2016. The Trews relief channel and the side spill weir at its head were lowered, which lets the channel carry more water and takes pressure off the quay at high flows. The channel was reshaped with a stream running through it.
• Phase 2, Cowley Bridge to Countess Wear. New embankments, walls, flood gates, control structures and demountable barriers at the Quay ran the length of the city to Bridge Road. Later works covered the Cowley Bridge outfall, Station Road, Hayes Barton Court, the Countess Wear mill leat, the Northbrook and Waring Bowen Court.
• What is in place now. The scheme protects more than 3,000 homes and businesses. It relies on 14 operational flood gates, demountable and temporary barriers and pumps, along with Network Rail's defences at Cowley Bridge and four gates south of St Davids station, according to the Environment Agency.
• Sharper warnings since 2025. In August 2025 the agency switched on a new forecasting model for the Exe, with a separate forecast below Trews Weir for river and tide together, and went from two targeted warning areas to four.

None of this takes a site out of the flood zone, and the gates only help if they are shut in time. The council's December 2024 Level 2 flood study found the Exe could stay above bank and defence levels for more than 24 hours, and that water would reach riverside sites less than two hours after it went over. An assessment has to show what happens if a gate is left open or a wall is overtopped; our guide to residual flood risk covers the method, and why a site stays in a flood zone after new defences explains the mapping.

Warning areas and gauges on the Exe through the city

Four Environment Agency warning areas cover Exeter and Topsham, each defined by the streets it protects, with an alert area for the river above the city. The gauges behind them show how close the river has come to its records. The figures below are from the agency's flood-monitoring service, read on 26 October 2026.

You can follow the Trews Weir and Topsham gauges on our live river levels map, and anyone in the warning areas can sign up for flood warnings. On an application, a building in one of these areas needs a plan built around the warning: who receives it, how long the occupants have, and where they go when the river is over the defences.

Exeter flooding on record, from 1960 to Longbrook Street

The river floods that shaped the city are old. Since 2008 Devon County Council has recorded property flooding in Exeter every few years, the latest from a storm that overwhelmed the drains. The dates below come from the Environment Agency, the gauges and Devon County Council's flood investigations.

1. October and December 1960. Two floods weeks apart put St Thomas and Exwick under water, in places close to 2 m deep in Exwick, with Cowick Street, Okehampton Street, Exe Island and the Quay among the streets hit. The Environment Agency says the original defences were built after flooding affected more than 1,000 properties.
2. 30 October 2000. The Exe at Trews Weir reached 4.611 m, still the gauge's highest reading, and the Creedy at Cowley Bridge set its own record that December.
3. 29 April 2008. Four properties flooded around Old Tiverton Road.
4. 22 December 2012. Nine properties flooded at Countess Wear.
5. 4 February 2014. The Topsham gauge recorded its highest tide, 3.32 m, during the winter storms of 2013 to 2014.
6. 16 October 2014. Twelve properties flooded in the St James area, the subject of a county flood investigation.
7. 17 August 2020. Six properties flooded in central Exeter.
8. 4 October 2021. A storm dropped 7.3 mm in a quarter of an hour on the Met Office gauge in the city. Longbrook Street flooded to knee height and nine properties flooded inside, more than anywhere else in Devon that night, the county's investigation report records.
9. 12 to 14 January 2023. The Exe at Pynes, just above the city, reached its highest level since the gauge opened. The Culm and the Creedy stayed lower, and the county found that the lower Exe escaped serious flooding.

The 2021 storm is the one to plan for on most hillside sites: a short downpour that beats the drains on a steep street, whatever the river is doing. An assessment in Exeter deals with that as well as the Exe, even where the flood map shows only one of them.

CP12 now, CC8 next: the policies a flood risk assessment in Exeter answers to

Exeter is between two local plans. Applications are still decided against the 2012 Core Strategy and the saved policies of the 2005 Local Plan First Review, but the new Exeter Plan is at examination, and the further it gets the more weight its policies carry.

The inspectors held hearings between March and May 2026 and sent their post-hearings letter on 15 September 2026; the council is preparing main modifications, and its timetable aims for adoption in March 2027. Until then CC8 sits alongside CP12 rather than replacing it. For the strategic study itself, our explainer on strategic flood risk assessments covers how planners use them, and our note on climate change allowances explains which figure applies to which building.

Drainage in a city with no critical drainage area

Exeter has no critical drainage area, according to the city council's flood page (updated 23 September 2026) and its 2024 study, though the Environment Agency is reviewing that. Devon County Council, the lead local flood authority, has been a statutory consultee on every major application since April 2015 and applies its 2023 SuDS guidance to schemes in the city.

• Into the ground first. Infiltration has to be ruled out with evidence before anything else is considered. Exeter's ground is largely clay, so soakaways often struggle, but the county expects BRE 365 tests at the depth and location of each soakaway, not an assumption.
• Groundwater monitoring. Where a soakaway does work, Devon wants the winter peak recorded, ideally over a year and at least from November to May, with 1 m of unsaturated ground under the base. Our note on when infiltration testing is needed covers the timing.
• Greenfield rates, brownfield included. Runoff should not exceed greenfield rates for the same storm. On a cleared Marsh Barton yard the county still starts from greenfield and accepts the closest betterment the site can show.
• Long-term storage. Where water cannot go into the ground, the extra volume from new roofs and paving is held back and let out at no more than 2 litres a second per hectare, or Qbar.
• Rainfall allowance. Devon asks for the upper-end 2080s rainfall allowance, 45% or 50% depending on location, and accepts no flooding on site in the 1 in 100 year storm with that added.
• Tidal outfalls. A pipe discharging to the tidal Exe needs no attenuation, but the network has to work when the tide locks the outfall, tested against the 1 in 200 year tide with climate change.
• Householders too. The city council expects an extension or a new drive to use water butts, rain gardens, permeable paving or a soakaway before any connection to a sewer.

Our guide to LLFA objections goes through the usual causes, and surface water flooding and planning explains how the surface water maps feed into an application.

Water Lane, Marsh Barton and the riverside allocations

Exeter's largest planned sites are brownfield land close to the Exe, so the river shapes how they can be built. The December 2024 Level 2 study, prepared for the Exeter Plan, looked at five sites in detail and found four of them mostly in Flood Zone 3a.

• Water Lane (SBA1). About 1,861 homes on 36.2 hectares between the canal and the river, guided by the Liveable Water Lane supplementary planning document of July 2024 and served by the new Marsh Barton station. It floods in the design river event, and the study's escape route, to be built above the design flood level, runs east over the Trews Weir suspension bridge to Bell Isle Drive.
• Exe Bridges Retail Park (SBA4). Also at risk in the design event; the escape route runs north over Exe Bridge to New Bridge Street.
• Red Cow (SBA3). At risk from the Exe and from the Taddiforde Brook, which floods the site significantly in the 1 in 1,000 year event and in the 1 in 100 year event with climate change; the route out climbs St David's Hill.
• East Gate (SBA2). The one site where surface water, not the river, is the main source; the route runs south along Western Way.
• Marsh Barton. Identified as having potential for regeneration rather than allocated, and any scheme there needs its access worked out in its own assessment.
• Topsham (TI1). Policy TI1 ties four allocations on the edge of Topsham to a larger East Devon site north of the town through a shared infrastructure framework. The old town's low land beside the Exe and the Clyst faces tidal flooding and wave overtopping, the city's 2024 study notes.

The study's advice for all of them is similar: put the most vulnerable uses on the highest ground, set habitable floors above the design flood with a margin, give residents a refuge above the 1 in 1,000 year level with climate change, and only raise land where modelling shows it does not push water elsewhere. That often means shops, offices or other less vulnerable uses on the ground floor, which changes how a street looks; our note on floodable voids and undercrofts covers that approach.

Extension, flats or a Marsh Barton unit: what each Exeter scheme needs

The flood zone and the size of the scheme decide most cases, and in Exeter the defences rarely change the answer. The table gives the usual position.

If a scheme falls between two rows, send us the address and we will tell you where it sits. Our guide on when an FRA is needed sets out the national triggers in full, and the sequential and exception tests explains how the two tests run.

Reports for Exeter's riverside streets, hillsides and allocations

A buyer in St Thomas, a business owner at Marsh Barton and a developer at Water Lane each need a different report. Chartered consultants write each one, and a senior consultant checks and signs it before it goes out.

• Every source, one site. A flood risk assessment for an Exeter site weighs the Exe and the defences, the tide below Trews Weir, the brooks, the drains on the hillsides and the sewers.
• Applications near the river. Exeter City Council expects a flood risk assessment for planning with any scheme in Flood Zone 2 or 3, which takes in much of St Thomas, Exwick and Marsh Barton, and on sites of 1 ha or more anywhere.
• Buying in St Thomas or Topsham. When a search flags a house in a warning area, a flood risk survey for property purchase compares its floor and threshold levels with the river and tidal flood levels.
• Homes in Flood Zone 3. New housing on the riverside has to pass the sequential and exception test, and under draft Policy CC8 it must also reduce flood risk overall.
• Major schemes read by the county. Devon County Council reads the drainage strategy on every major Exeter application, checking infiltration evidence, greenfield rates and storage.
• Clay, slopes and tide-locked outfalls. A surface water drainage strategy for an Exeter site sizes storage to Devon's 45% or 50% rainfall allowance and checks outfalls to the tidal river.
• Conditions on the allocations. Permissions at Water Lane and the other riverside sites carry drainage conditions, and discharge of drainage conditions supplies the details the county asks for.
• Breach and overtopping. Behind the Exe walls at St Thomas, Exwick or the Quay the flood map shows the undefended case, so flood modelling tests a breach or overtopping there and sets floor levels from it.
• Less than two hours' notice. With water reaching Water Lane, Red Cow or Exe Bridges within two hours of overtopping, a flood warning and evacuation plan sets out who acts on a warning and which way people leave.
• Streets that have flooded. Owners in Countess Wear, St James or the centre, where properties flooded in 2012, 2014 and 2021, can use a flood risk assessment for insurance to show insurers the real position.
• Marsh Barton transactions. Before buying or lending on an industrial unit or yard in the valley floor, flood risk due diligence puts the river and surface water risk in front of the deal.
• Trading behind the gates. Businesses on the Quay and at Marsh Barton can plan for closures and recovery with a business continuity flood risk assessment.
• Commercial space at East Gate and Exe Bridges. Non-residential buildings in the allocations seeking BREEAM credits need a BREEAM flood risk assessment for the Pol 03 issue.
• Water in the valley gravels. The Level 2 study found varying groundwater emergence risk on the riverside sites, and a groundwater flood risk assessment covers it where a scheme has basements or relies on infiltration.
• Combined sewers in the old city. Where older streets still drain to combined sewers with limited capacity, a foul drainage strategy shows South West Water how new flows can be taken.
• Before buying riverside land. For land near Water Lane or Marsh Barton, a flood risk feasibility study tests the flood and drainage limits before an offer is made.

River, drains, sewers or tide: who answers for each in Exeter

Responsibility in Exeter is split by where the water comes from, and an application may hear from more than one body. In an emergency, ring 999 first.

For planning, Devon's SuDS guidance for Devon sets the drainage standards, and its flood reports page holds the Exeter surface water management plans and the Section 19 investigations. Our page on the lead local flood authority explains the county's part. Further up the river, Tiverton has its own page, and across the estuary so does Dawlish.

Exeter flood risk questions from buyers, builders and planners

Send us the address of a terrace in St Thomas or a plot at Water Lane, and our consultants at Unda Consulting Limited will tell you which reports it needs. Call 01293 214444 or email enquiries@unda.co.uk.