Flood Risk Assessment in Devon

Unda prepares clear, robust flood risk assessments and surface‑water drainage strategies for residential and commercial sites right across Devon. A flood risk assessment in Devon shows your planning authority that a development will stay safe from flooding for its whole lifetime and will not push flood risk onto anyone else.

Devon is a county of steep catchments and a long, exposed coast, so flood risk here rarely comes from one direction. We assess every source that matters on a Devon site — the rivers that drain Dartmoor and Exmoor, the surface water that overwhelms drains in the towns, the groundwater that rises through valley gravels, and the tides and waves along the south and north coasts — then deal directly with the Environment Agency and the relevant Lead Local Flood Authority on your behalf. We work for architects, planning consultants, developers, landowners, home buyers and businesses, whether the report is needed for planning, a property purchase, a mortgage or insurance, BREEAM, or a drainage strategy.

If you need a quote or want to talk a Devon site through, contact one of our experienced flood risk consultants on 01293 214444.

Flood risk assessment in Devon at a glance

• Steep catchments, fast rivers. The Exe, Otter, Culm, Clyst, Taw, Torridge, Dart and Teign drain high ground quickly, so heavy rain becomes a river flood peak in the valleys below within hours.
• Three Lead Local Flood Authorities. Devon County Council covers most of the county, while Plymouth and Torbay are unitary authorities and run their own flood teams. We work with all three, and with the Dartmoor and Exmoor National Park authorities.
• A record set in 2026. During Storm Chandra in January 2026 the River Otter at Fenny Bridges reached 2.83m, its highest ever recorded level, beating the December 2000 record of 2.81m.
• Flood Zone 1 is not a free pass. Since the 2025 Planning Practice Guidance update, surface‑water risk on the Flood Map for Planning can trigger an assessment even on a Flood Zone 1 site.

Check flood risk anywhere in Devon

Devon is outlined below. Screen any postcode in the county against Environment Agency data for rivers and sea, surface water and the planning flood zones, with a climate outlook to 2125. It is an indicative first pass, not a substitute for a site‑specific assessment.

Flood risk across Devon: rivers, the coast and surface water

River flooding leads in Devon, but it is rarely the only issue on a site. Water runs fast off Dartmoor, Exmoor and the Blackdown Hills into rivers such as the Exe, Otter, Taw and Dart; surface water overwhelms drains in Exeter, Tiverton and the coastal towns; groundwater rises through valley gravels; and the south and north coasts add tidal and wave risk. Most Devon sites face more than one source at once.

The county splits roughly into three river systems. The Exe and its tributaries the Culm, Creedy and Clyst gather in the east and run through Exeter to the sea at Exmouth, with the Otter, Sid and Axe draining the East Devon coast alongside them. The Taw and Torridge drain the north through Barnstaple and Bideford. The Dart, Teign, Avon, Erme and Yealm drain the south through the South Hams. Knowing which watercourse drives the risk on a given site, and how it behaves in a storm, is the heart of a credible flood risk assessment.

• Rivers (fluvial). The Exe, Otter, Culm, Clyst, Taw, Torridge, Dart and Teign flood their valley floors. Land in Flood Zones 2 and 3 along these corridors almost always needs a flood risk assessment for planning.
• Surface water (pluvial). Now the most widespread flood risk in England. Intense rain runs off steep ground and overwhelms drains in Exeter, Tiverton, Cullompton and the coastal towns. Surface water can trigger an assessment even where the river map shows Flood Zone 1 — see critical drainage areas.
• Coastal and tidal. The south coast around Exmouth, Dawlish and the Exe estuary, and the north coast around Barnstaple and the Taw–Torridge estuary, are exposed to tidal flooding and wave action, made worse by sea‑level rise.
• Groundwater. Permeable valley gravels and the chalk and greensand of East Devon can raise water tables that flood low ground and basements without ever showing on a river map — critical for any soakaway or below‑ground level. See groundwater flooding.
• Sewers and ordinary watercourses. Smaller streams and the surface‑water sewer network back up in heavy rain. These sit with the Lead Local Flood Authority and South West Water rather than the Environment Agency.

Exeter is the textbook case for why a single map is never enough: the Exe and Creedy floodplains run against the western and northern edges of the city while low‑lying neighbourhoods flood from surface water that cannot drain by gravity. A scheme there has to reconcile both, which is exactly why the £32 million Exeter Flood Defence Scheme was built to better protect more than 3,000 homes and businesses.

A history of flooding in Devon

These dated events are why authorities in Devon scrutinise development so closely, and why a flood risk assessment in Devon has to be evidence‑led rather than generic. Each one reshaped local policy and the flood defences a developer now has to design around.

• 1607 — the Bristol Channel flood. A huge tidal surge (now thought to have been a storm tide, possibly with a tsunami component) drove seawater far inland along the North Devon coast and the Taw–Torridge estuary, one of the earliest well‑documented flood disasters in the South West.
• 1952 — the Lynmouth disaster. After around nine inches of rain fell on already saturated Exmoor in a single day, the East and West Lyn rivers tore through Lynmouth on the night of 15–16 August. Thirty‑four people died, dozens of buildings were destroyed and hundreds were made homeless — still one of the worst river floods in English history.
• 1960 — Exeter’s “Black Friday.” The River Exe overflowed and split the city in two, with around a thousand properties flooded, followed by a second major flood that December. The events led directly to Exeter’s post‑war flood defences.
• Autumn 2000. The wettest autumn in over two centuries flooded thousands of properties across Devon and the wider South West and prompted a step change in how local flood risk was managed.
• October 2023 — Storm Babet. Persistent, widespread rain flooded properties across Devon; at Cockwood on the Exe estuary the historic Ship Inn partially collapsed after the deluge.
• January 2026 — Storm Chandra. The River Otter at Fenny Bridges reached a record 2.83m, a severe flood warning was issued at Ottery St Mary, and more than 80 properties flooded across over 30 locations in Devon, with Dartmoor recording up to 88mm of rain. See our coverage of Storm Chandra.

A 2022 analysis placed Devon among the English counties with the highest proportion of properties at risk of flooding, which is why developers, buyers and insurers here so often need site‑specific evidence rather than a broad map. Devon County Council publishes its own flood investigation reports after significant events, and these are a useful starting point for understanding how a particular area has behaved.

Planning and drainage policy for development in Devon

Development in Devon is judged against national policy — the NPPF and its Planning Practice Guidance — read alongside local strategy and drainage standards. The wrinkle in Devon is that responsibility is split between three flood authorities and two National Park authorities, so the body you have to satisfy depends on exactly where the site sits.

The Lead Local Flood Authority is the statutory consultee for surface water and drainage on major development, and the Environment Agency advises on river and coastal flood risk. Getting the drainage right early, to the local standard, is usually what keeps a Devon application moving — an unresolved drainage objection can hold up a decision for months. Our notes on NPPF flood risk guidance and the Environment Agency’s planning role set out how the pieces fit together.

• Three Lead Local Flood Authorities. Devon County Council is the LLFA for most of the county; Plymouth City Council and Torbay Council are unitary authorities that act as their own LLFAs. Each maintains its own flood team and local guidance.
• Two National Park authorities. Dartmoor and Exmoor National Park authorities are the planning authorities within their boundaries, so a site on the moor is determined by the park authority, working alongside the relevant LLFA and the Environment Agency.
• Devon’s local strategy and SFRAs. The Devon Local Flood Risk Management Strategy 2021–2027 sets the direction, and each district holds a Strategic Flood Risk Assessment that maps local risk and the policies you must satisfy.
• The Devon SuDS standard. The county’s Sustainable Drainage System Guidance for Devon (2023) expects surface‑water runoff to be restricted to greenfield rates — generally no more than 2 litres per second per hectare, or QBAR — with brownfield schemes required to demonstrate betterment as close to greenfield as feasible.
• Climate change over the lifetime. Devon expects up‑to‑date peak‑rainfall and river‑flow allowances to be applied so a scheme is shown safe across its full design life, taken as 100 years for housing.

When you need a flood risk assessment in Devon

As a rule, you need a flood risk assessment in Devon when your site sits in Flood Zone 2 or 3, when it is one hectare or larger even in Flood Zone 1, or when it is shown at risk of surface water flooding on the Flood Map for Planning. A drainage strategy is usually needed once a scheme reaches ten or more dwellings, a hectare in area, or 1,000m² of floor space.

The table below is a quick guide to the report a typical Devon site needs. It is a starting point, not a substitute for advice — a clean, site‑specific assessment can sometimes show a site is safe and remove a requirement, and a constrained coastal or valley‑floor site can need more than the table suggests.

How Unda helps with flood risk in Devon

We are experts on Devon’s flood risk and planning landscape, not a local branch — and that is the point. We act as the accurate translation layer between your scheme and the Environment Agency, the relevant Lead Local Flood Authority and national policy, so your application lands right first time. Our consultants know how Devon’s rivers, coast and drainage standards behave, and we stay involved past the report to answer any objection.

Unda has prepared more than 5,000 flood risk assessments since 2014 and is a CIWEM Business Partner, with a Senior Flood Risk Consultant signing off every report. From the Exe valley to the South Hams and the north coast, we have assessed sites across the county and dealt with each of Devon’s flood authorities. You can read more about Unda and our work in the media.

Flood risk assessments for every situation in Devon

People come to us for a flood risk assessment in Devon for many reasons — securing planning permission, buying a home, satisfying a mortgage lender or insurer, achieving a BREEAM rating, or designing the drainage for a new scheme. We prepare the right report for each.

It helps to keep three things separate. 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 answer different questions: is the site safe, should the development be here, and where does the surface water go. Groundwater and flood modelling are not separate reports — groundwater is a source every assessment considers, and modelling is a technique that feeds one.

• Flood risk assessment for planning. The site‑specific report that satisfies the NPPF and shows your Devon development is safe for its lifetime without increasing risk elsewhere.
• Flood risk survey for property purchase. An independent, property‑specific survey for buyers and their advisers, going beyond the conveyancing search to assess the actual building.
• Flood risk assessment for insurance. Property‑level evidence for brokers and underwriters where cover has been restricted, declined or priced on flood risk.
• Flood risk assessment for BREEAM. Structured around BREEAM Pol 03 so a scheme keeps its flood and surface‑water credits.
• Sequential and exception tests. The locational justification that a higher‑risk Devon site is the most appropriate available, prepared alongside the assessment.
• Groundwater flood risk. A defensible design groundwater level for sites on Devon’s gravels, chalk and greensand, tested against floor levels, basements and drainage.
• Flood modelling. 1D and 2D hydraulic modelling where national mapping does not reflect a Devon site by a river, estuary or floodplain.
• Surface‑water drainage strategy (SuDS). A scheme that manages runoff to the Devon SuDS standard following the four pillars of SuDS and the drainage hierarchy.
• Discharge of drainage conditions. The detailed design that discharges a pre‑commencement or pre‑occupation drainage condition on a Devon permission.
• Preliminary drainage design. The early, outline read that flags infiltration issues before they affect layout and land value.

Buying or selling rather than building? Flood risk can affect value, insurability and mortgageability — see how flood risk affects house prices. And if you are weighing up a minor scheme yourself, our note on whether you can do your own flood risk assessment is a good place to start.

Flood risk management and emergency contacts in Devon

Responsibility for flooding in Devon is split by source: the Environment Agency leads on main rivers and the sea, the Lead Local Flood Authority on surface water, groundwater and ordinary watercourses, and South West Water on the public sewers. The contacts below cover reporting and emergencies; in any risk to life, call 999.

To check a Devon location yourself before commissioning a report, our free tools use the same open data the regulators rely on:

• Flood Risk Map. Screen any Devon postcode for rivers and sea, surface water, reservoirs and flood zones, with a climate outlook to 2125.
• Live River Levels Map. See whether rivers such as the Exe, Otter or Taw near you are low, normal, high or near record, from the live Environment Agency feed.
• Geology and ground conditions. An indicative read of the geology beneath a Devon site to gauge whether a soakaway is likely to work.
• Drainage calculators and the BRE 365 infiltration calculator. A fast first pass at sizing and checking a Devon drainage scheme; see also when infiltration testing is required.
• GOV.UK “Check for flooding” in Devon. The Environment Agency’s live flood warnings and five‑day forecast for the county.

Flood risk assessment in Devon: your questions answered