Flood Risk Assessment in Bath

Bath is one of the most flood-exposed historic cities in England. The River Avon flows straight through its centre, the city sits on the valley floor where the river meets steep limestone hillsides, and much of the centre — Bath Quays, the Recreation Ground, Green Park, Riverside and the Lower Bristol Road corridor — lies within the highest-probability river flood zone. If you are developing, buying, insuring or refinancing here, a flood risk assessment in Bath is the report that turns that broad mapped risk into a clear, site-specific answer the Environment Agency, the council and a lender will accept.

We prepare flood risk assessments in Bath for planning, for property purchase and mortgage, for insurance and for BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS). 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. Our consultants know Bath, the River Avon and Bath & North East Somerset planning policy well, and reply to every quote request within 60 minutes.

The River Avon runs through the heart of Bath, and the 1960 flood that pushed a record flow through the city is the reason the modern flood defences and the radial gate at Pulteney Weir exist at all — protection that reduces the risk but never removes it.

Flood risk assessment in Bath at a glance

A flood risk assessment in Bath establishes how flooding from every source could affect a site over its lifetime and proves the development can be made safe without increasing risk elsewhere. The key facts for the city:

• Dominant source is the River Avon. The Bristol Avon flows through central Bath, and the valley floor through the centre lies largely in Flood Zones 2 and 3 on the Environment Agency Flood Map for Planning.
• Surface water adds a second layer. Steep limestone valley sides shed runoff quickly onto the flat valley floor, so pluvial (surface water) flooding affects streets well away from the river.
• The defences are real but partial. The Bath Flood Defence Scheme of the 1960s–70s and the newer Bath Quays Waterside scheme reduce risk — they do not remove residual risk, which an assessment must still address.
• Bath & North East Somerset Council is your Lead Local Flood Authority. It is also the planning authority, and applies Core Strategy Policy CP5 and Placemaking Plan Policy SU1 to flood risk and drainage.
• World Heritage constraints bite. Bath is a UNESCO World Heritage Site, so raising floor levels or adding visible flood resilience has to be reconciled with strict design and conservation control.

Need a fast, fixed-fee answer for a specific site? You can start a quote or call +44 (0) 1293 214444 — one of our experienced flood risk consultants will get back to you within 60 minutes.

Check flood risk anywhere in Bath

Bath and North East Somerset is outlined in coral on the map below. Enter any postcode to zoom in and see the Environment Agency’s modelled flood risk for that location — rivers and sea, surface water and reservoirs, flood zones for planning, and climate-change projections to 2125 — with live flood warnings. It is a free screening tool to orient you before a site-specific assessment, not a substitute for one. For current river conditions you can also use our Live River Levels Map, and to check whether the ground is likely to suit a soakaway, our Geology & Ground Conditions checker.

Flood risk in Bath: the River Avon and its valley

Flooding in Bath is driven first by the River Avon, then by surface water running off the surrounding hills, with groundwater and sewer surcharge as secondary sources. The Bristol Avon enters the city from the south-east, is held up at Pulteney Weir in the centre, and leaves to the west towards Bristol. Because the city was built on the narrow valley floor, the floodplain and the most valuable development land are the same ground — which is why so many Bath sites need careful flood risk work.

The Avon gathers several tributaries just upstream of and within the Bath area, and their combined catchments shape how fast the river rises. The Midford Brook — formed where the Cam Brook and Wellow Brook meet at Midford — drains a catchment of around 147 square kilometres that is largely impermeable Lias, so rainfall runs off quickly rather than soaking away. The Kennet & Avon Canal also threads through the city, adding a man-made water body whose own residual risk has to be considered near it.

National screening tools are the right place to start but the wrong place to finish: as we explain in our guide to how accurate flood maps are, a city like Bath has tight local variations in ground level, defences and flow paths that strategic mapping cannot capture. Groundwater in particular sits on no national flood map and has to be assessed directly, which is why a dedicated groundwater flood risk assessment matters on the lower valley floor.

A history of flooding in Bath

Bath has flooded repeatedly through its recorded history, and the dated events explain why the modern defences were built. The flood of 1882 was for decades treated as the worst on record, with a peak flow estimated at around 367 cubic metres per second. The defining modern event came in December 1960, when the Avon peaked at an estimated 424 cubic metres per second — beyond the city’s gauging capacity at the time — and caused damage put at around £1.4 million in 1960 prices. Further serious flooding in 1968 was the last occasion the Avon was, in the words of local flood historians, “allowed to get seriously out of control” before the scheme took effect.

• 1882. Long regarded as Bath’s worst flood on record, with a peak flow of roughly 367 cubic metres per second.
• December 1960. A record peak of about 424 cubic metres per second and around £1.4 million of damage — the direct catalyst for the Bath Flood Defence Scheme.
• 1968. The West Country floods hit the Avon again; the last major uncontrolled flood through the city before the new works were completed.
• Since the 1970s. Serious river flooding has been far less frequent, thanks to sustained investment in defences and channel maintenance — but lower-level flood warnings on the Avon riverside continue today.

This record still matters today. Under national planning policy a flood risk assessment must demonstrate a site is safe for its whole lifetime, usually 100 years for housing, and how high the Avon has reached in the past is part of the evidence that informs finished floor levels and mitigation.

Bath’s flood defences and recent schemes

Bath is defended, but defended is not the same as safe, and every flood risk assessment in Bath has to work out what risk remains. The Bath Flood Defence Scheme, built between the early 1960s and the mid-1970s at a cost of around £3 million, dredged and widened the river, raised and sheet-piled the banks, replaced the Old Bridge with Churchill Bridge in 1964, and rebuilt Pulteney Weir with the radial sluice gate that opened in 1972 to pass flood flows while holding the famous upstream water level.

More recently, Bath & North East Somerset Council and the Environment Agency delivered the Bath Quays Waterside scheme, a roughly £5 million project of new and raised defences between Churchill Bridge and Midland Bridge that reduces flood risk to the Lower Bristol Road and around 60 to 100 properties while unlocking the Bath City Riverside regeneration. Separately, Wessex Water installed a 125,000-litre underground storm tank at Lambridge to ease pressure on the sewer network in the east of the city.

Because the Environment Agency’s flood maps show risk as if the defences were not there, defended Bath sites stay inside the flood zones — and an assessment has to test what happens if a defence is overtopped or breached.

That remaining exposure is what we call residual flood risk, and on defended Bath sites it is often where a planning application is won or lost. Where the mapping is too coarse to settle it, site-specific flood modelling defines the levels, depths and velocities the assessment relies on.

Planning and drainage policy for development in Bath

For development in Bath your Lead Local Flood Authority and your planning authority are the same body: Bath & North East Somerset Council. It reviews flood risk against national policy — the National Planning Policy Framework and its Planning Practice Guidance — and against its own Local Plan, while the Environment Agency advises on the River Avon as a main river. Since the September 2025 PPG update, the sequential, risk-based approach applies to all sources of flooding, so even a site that screens as Flood Zone 1 can attract surface-water scrutiny here.

• Lead Local Flood Authority. Bath & North East Somerset Council leads on surface water, groundwater and ordinary watercourses — see our explainer on what a Lead Local Flood Authority does.
• Local Plan Policy CP5. The Core Strategy requires a sequential approach to flood risk and the use of sustainable drainage to control runoff and avoid increasing risk elsewhere.
• Placemaking Plan Policy SU1. Requires planning applications to be accompanied by a SuDS proof of concept, with drainage built on sustainable principles that do not increase flood risk.
• Strategic Flood Risk Assessment. The council’s Level 1 SFRA is the strategic evidence base you should check before fixing a layout.
• World Heritage Site. Bath’s UNESCO status means flood mitigation has to be reconciled with conservation and design control — raised levels and resilience need a careful, defensible approach.

The specifics matter, so it is worth reading the council’s own flood risk guidance for planning and development and its Level 1 Strategic Flood Risk Assessment early. We map every report directly to these tests, as set out in our NPPF flood risk guidance.

Common development and FRA needs in Bath

The kind of flood risk assessment a Bath site needs follows the kind of development. Because the city’s growth land sits on the Avon floodplain and on steep valley sides, the same few patterns recur, each with its own flood and drainage implications.

• City-centre regeneration on the floodplain. Schemes around Bath Quays, Riverside and the enterprise area sit in Flood Zone 2 or 3, so they turn on finished floor levels, safe access and egress, and often compensatory flood storage and a sequential or exception test.
• Hillside infill and conversions. Plots below Lansdown, Bathwick and Combe Down rarely flood from the river but generate and receive surface water runoff, so the drainage strategy carries the assessment.
• Heritage conversions and change of use. Reusing Bath’s historic building stock means reconciling resilience and raised levels with World Heritage and listed-building constraints.
• Basements and lower-ground floors. Common in Bath’s Georgian terraces, these raise specific surface-water, groundwater and safe-exit questions that an assessment must resolve.
• Householder extensions. Smaller works may rely on Environment Agency standing advice, but anything near the Avon or in a surface-water area usually still needs a proper look — see whether you can do your own FRA.

How Unda helps with flood risk assessment in Bath

Unda know Bath and the River Avon, and we work to the people who judge your scheme: Bath & North East Somerset Council, the Environment Agency and national policy. We assess every source of flooding, read the data for your specific site, model flood levels where the maps fall short, and design proportionate mitigation in a report planners and the Environment Agency accept. A Senior Flood Risk Consultant signs off every report, and we stay involved past submission to answer objections. We have completed more than 5,000 flood risk assessments since 2014 and are rated 5.0 on Google.

Whether you need a planning flood risk assessment, a flood risk survey for a property purchase, or a full drainage strategy, you can speak to one of our experienced flood risk consultants today. Learn more about Unda and our flood risk consultants.

Flood risk assessments for every situation in Bath

People need a flood risk assessment or drainage strategy in Bath for many reasons. We prepare each of the following, scoped to your site and the question you need answered.

• Flood risk assessment for planning. The site-specific report that supports a planning application in Flood Zones 2 and 3, on larger Flood Zone 1 sites, or wherever surface-water risk is flagged — FRA for planning.
• Flood risk survey for property purchase. An independent, property-specific survey for buyers, lenders and conveyancers when a search flags risk — homebuyer flood risk survey.
• Flood risk assessment for insurance. Property-level evidence where premiums climb, cover is restricted, or risk needs clarifying after an event — FRA for insurance.
• Flood risk assessment for BREEAM. Structured around BREEAM Pol 03 to secure flood and surface-water credits from the outset — BREEAM FRA.
• Sequential and exception tests. The locational justification a Bath site in a higher-risk zone often needs — sequential and exception tests.
• Surface-water drainage strategy and SuDS. The drainage report that answers Policy SU1 and the four pillars of SuDS — drainage strategy and SuDS design.
• Discharge of drainage conditions and preliminary design. From an early preliminary drainage design to the detailed scheme that discharges a drainage condition.
• Groundwater assessment and flood modelling. Where the lower valley’s geology or a watercourse demands it, a focused groundwater assessment or 1D/2D flood modelling within the FRA.

Designing the drainage yourself? Our free drainage calculators and BRE 365 infiltration rate calculator give a defensible first pass, and our note on when infiltration testing is required explains the evidence the council expects. Bath sits within the wider Somerset region we cover.

Local flood risk management and emergency contacts in Bath

Several bodies share responsibility for flood risk in Bath. Knowing who deals with what saves time, whether you are reporting a flood, planning a development or preparing for severe weather.

The council’s Local Flood Risk Management Strategy sets out how local flood risk is managed across the district, and you can sign up for Environment Agency flood warnings through Floodline. For a development decision, none of these replace a site-specific assessment.

Flood risk assessment in Bath: frequently asked questions