Flood Risk Assessment in Tewkesbury

Our team at Unda use years of experience to prepare comprehensive flood risk assessments and drainage strategies for commercial and residential sites across Tewkesbury. Few towns in England flood as visibly or as often, so a flood risk assessment in Tewkesbury has to do more than tick a box — it has to show your local planning authority and the Environment Agency that a development will stay safe for its whole lifetime without pushing flood risk onto neighbours downstream.

Tewkesbury sits at the confluence of the River Severn and the River Avon, the meeting point that makes the town the focal point for flooding across much of north Gloucestershire. We assess every source that matters here — the two big rivers, the tributaries that back up behind them (the Carrant Brook, the Swilgate, the Tirle Brook and the Mill Avon), the surface water that overwhelms drains in heavy rain, and the groundwater that rises through the valley gravels — then deal directly with the Environment Agency and Gloucestershire County Council as Lead Local Flood Authority on your behalf. We guide architects, planning consultants, developers, landowners, home buyers and businesses through to a decision, whether the report is needed for planning, a property purchase, mortgage or insurance, BREEAM, or a surface-water drainage strategy.

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

Flood risk assessment in Tewkesbury at a glance

• Two major rivers meet in the town. The Severn and the Avon converge at Tewkesbury, so heavy rain anywhere in either catchment becomes a flood peak here — and when both rivers are high at once, the water has nowhere to go.
• Over 1,800 homes and 300 businesses flooded in July 2007, the defining event that left Tewkesbury Abbey surrounded by water, cut the town off by road, and knocked out the Mythe water treatment works — an event that helped trigger the national Pitt Review.
• Gloucestershire County Council is the Lead Local Flood Authority. It leads on surface water, groundwater and ordinary watercourses; the Environment Agency leads on the Severn and the Avon. We work with both.
• Flood Zone 1 is not a free pass. Since the 2025 Planning Practice Guidance update, surface water risk can trigger an assessment even on a Flood Zone 1 site in Tewkesbury.

Check flood risk anywhere in Tewkesbury

Tewkesbury Borough is outlined below. Screen any postcode in the area 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 — useful for an early read on a site — not a substitute for a site-specific assessment. For current conditions you can also use our live river levels map and our free flood risk map.

Why Tewkesbury floods: the Severn, the Avon and their tributaries

Tewkesbury floods because of where it sits. The River Severn — the longest river in Britain — and the Warwickshire Avon meet at the town, and a third channel, the Mill Avon, runs through it. When prolonged rain falls across the huge catchments upstream, both rivers rise together and the floodplain on which much of the town and the Severn Ham meadow sit fills up. River flooding dominates here, but it rarely arrives alone: surface water and the smaller watercourses make the picture worse.

The smaller watercourses are central to local flood risk. The Carrant Brook, the Swilgate and the Tirle Brook drain the land around the town and discharge towards the Severn and Avon. When the main rivers are high they cannot get away, so they back up and spill — which is why neighbourhoods such as Newtown are exposed to the Swilgate and the Tirle Brook as much as to the Severn itself. The Environment Agency is investigating slowing the flow of the Carrant Brook, Tirle Brook and Swilgate upstream of Tewkesbury to reduce this risk. Understanding which watercourse drives the risk on a given site is the heart of a credible fluvial flood risk assessment.

A history of flooding in Tewkesbury

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

• July 2007 — the defining flood. After the wettest summer on record, two months’ rain fell in 14 hours on 20 July. Over 1,800 homes and 300 businesses were flooded across the borough, water reached more than two metres in places, the town was cut off by road, and flood water entered Tewkesbury Abbey for the first time in around 247 years. The Mythe water treatment works was inundated, cutting mains water to roughly 150,000 people for up to 17 days; 48,000 homes lost power. It remains the benchmark event and helped drive the national Pitt Review into England’s flood response.
• 2000 — the Severn floods. The autumn 2000 floods across the Severn valley were a warning of what was to come, and are still used as a reference event for the catchment. We covered their legacy in 25 years on from the 2000 Severn floods.
• November 2012 — renewed flooding. Heavy autumn rainfall flooded properties and closed roads in and around Tewkesbury again, a reminder that 2007 was not a one-off.
• February 2020 — Storm Dennis and Storm Ciara. The wettest February on record left soils saturated; the Severn and Avon rose sharply and flooded low-lying parts of the town and surrounding villages.
• January 2024 — Storm Henk. Flood water from the Severn and Avon again surrounded the town. The River Severn at the Mythe Bridge gauge peaked at about 4.78 m, well above its 4.2 m trigger level; the Severn Ham, riverside roads including the A38, and Willows Caravan Park were flooded, with the rescue charity SARA assisting residents.

Flood water entered Tewkesbury Abbey in 2007 for the first time in roughly two and a half centuries — a single fact that captures why a generic, desk-based report will not satisfy planners in this town.

Which parts of Tewkesbury are most at risk of flooding?

Flood risk is not spread evenly across the town. The wide Flood Zone 3 of the Severn and Avon wraps around Tewkesbury, and several neighbourhoods sit low against the rivers or their tributaries. The areas below face the highest profile risk, but surface water can flood streets well outside the mapped river floodplain — which is why a site-specific assessment matters even where the national map looks reassuring.

• The historic town centre. Mill Street, Quay Street and the streets around the Abbey and the Mill Avon sit close to the water and flooded badly in 2007.
• Newtown. Exposed to the Swilgate and the Tirle Brook as well as the Severn, and one of the worst-affected areas in 2007.
• Priors Park. Low-lying residential area on the south side of the town, close to the Severn floodplain.
• Wheatpieces and Walton Cardiff. Newer development on the south-east edge where surface water and the Tirle Brook are the main constraints.
• Northway and Ashchurch. Drained by the Carrant Brook, which backs up against the Severn during a flood.
• The Severn Ham and the Mythe. The Ham is a natural floodplain meadow that floods most winters; the Mythe, to the north-west, carries the bridge, the river gauge and the water treatment works.

Planning policy and your Lead Local Flood Authority in Tewkesbury

Two kinds of authority set the rules. The Environment Agency leads on the River Severn, the River Avon and the Mill Avon as main rivers. A Lead Local Flood Authority (LLFA) leads on surface water, groundwater and ordinary watercourses such as the Swilgate and Tirle Brook — and in Tewkesbury that is Gloucestershire County Council. A development here deals with both, alongside Tewkesbury Borough Council as the local planning authority.

Gloucestershire County Council sets out its approach in its Local Flood Risk Management Strategy and, with the district councils, commissioned the Strategic Flood Risk Assessment that underpins local planning. The county was a national pilot for Surface Water Management Plans, with an early plan centred on the Tewkesbury, Cheltenham and Gloucester corridor. The adopted Gloucester, Cheltenham and Tewkesbury Joint Core Strategy and the Tewkesbury Borough Plan steer development towards lower-risk land and require flood risk and drainage to be addressed early. The Lower Severn Internal Drainage Board also has an interest in low-lying land near the rivers.

What your flood risk assessment in Tewkesbury must show

Your assessment and any drainage strategy must satisfy national policy — the NPPF and its Planning Practice Guidance — and the local framework. It needs to identify every source of flooding affecting the site, classify the flood zone correctly, apply the right vulnerability classification, set safe finished floor levels and access and egress, and show the development does not increase risk elsewhere. Where a higher-risk site is involved, the Sequential and Exception Tests apply. On drainage, the 2025 national SuDS standards and the four pillars of SuDS shape what the LLFA will accept, and runoff is normally held to greenfield rates with a climate change allowance.

Development and flood risk assessment in Tewkesbury

Tewkesbury is under real pressure for new homes and employment land, and the kind of site you bring forward shapes the assessment you need. The right scope from the start is the difference between a clean approval and a flood or drainage objection that holds an application up for months.

• Town-centre and brownfield regeneration. Redevelopment close to the Severn, Avon and Mill Avon almost always sits in Flood Zone 2 or 3 and turns on finished floor levels, safe access and compensatory flood storage.
• Edge-of-town growth. Larger allocations around Ashchurch, Northway and Walton Cardiff hinge on the Carrant Brook and Tirle Brook, surface water and a robust drainage strategy.
• The A38 / M5 corridor. Commercial and logistics schemes near Junction 9 need both flood risk and drainage addressed, often with preliminary drainage design at the outline stage.
• Rural and riverside sites. Conversions and small schemes near the rivers or an ordinary watercourse turn on riparian responsibilities and, where works affect a watercourse, ordinary watercourse consent.

Because the Environment Agency’s Flood Map for Planning is drawn as if defences are not there, a site protected by the post-2007 works can still fall in Flood Zone 3. Planning policy requires the residual risk — what remains if a defence is overtopped or fails — to be assessed over the development’s lifetime, including climate change.

Climate change is not optional here. A Tewkesbury assessment must apply the Environment Agency’s allowances for higher river flows and rainfall over the development’s lifetime — generally 100 years for housing — which sets floor levels, freeboard and how much attenuation a drainage scheme needs.

How Unda helps with flood risk assessment in Tewkesbury

We act as the accurate translation layer between your scheme and the requirements set by the Environment Agency, Gloucestershire County Council as LLFA and national planning policy. We are experts on Tewkesbury’s flooding, not a generic report mill, and we know how the Severn, the Avon and the tributaries behave when they all rise together.

A flood risk assessment in Tewkesbury from Unda assesses every credible source — the Severn and Avon, the Mill Avon, the Carrant Brook, Swilgate and Tirle Brook, surface water, groundwater and sewers — compares modelled flood levels against your proposed floor levels, sets safe access and egress, and recommends mitigation the regulators will accept. Where national mapping is not enough on a riverside site, we bring in detailed flood modelling. We are a CIWEM Business Partner with chartered members, and a senior consultant signs off every report. Where the council needs it, a surface-water drainage strategy sits alongside the assessment as a separate report so the two cases stay consistent and an objection has nowhere to land. You can reach our flood risk consultants for an early view on any site.

Flood risk assessments and related reports for every situation in Tewkesbury

People need a flood risk assessment or a drainage strategy in Tewkesbury for many reasons. 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. We prepare all of them.

• Flood risk assessment for planning. The site-specific report prepared to satisfy the NPPF, the Environment Agency and Tewkesbury Borough Council. Groundwater and, where needed, flood modelling are assessed within it rather than as separate reports.
• Flood risk survey for property purchase. An independent, property-specific survey for home buyers and their advisers when a search or conveyancing report flags risk — common in a town with Tewkesbury’s history.
• Flood risk assessment for insurance. Property-level evidence where premiums rise, cover is restricted, or a buyer needs clarity. See also our guides to flood risk and mortgage lending and whether flood risk affects house prices.
• Flood risk assessment for BREEAM. Structured around BREEAM Pol 03 so a scheme earns its flood and surface-water credits from the outset.
• Sequential and Exception Tests. The locational case that steers development to lower-risk land — frequently needed given the extent of Flood Zone 3 around Tewkesbury.
• Drainage strategy and SuDS design. How surface water is managed to meet policy, with discharge of drainage conditions at the detailed stage.
• Groundwater flood risk. Where the valley gravels raise a credible groundwater flooding issue or a scheme relies on infiltration.

Free tools can help you screen a site before you commission anything: our geology and ground conditions checker gives an early read on whether a soakaway is likely to work, the BRE 365 infiltration rate calculator turns trial-pit results into a design rate, and our drainage calculators size the main SuDS elements. Across all of it, our flood risk assessment service ties the reporting together.

Tewkesbury flood resources and emergency contacts

The most reliable Tewkesbury flood information comes from the lead authorities. For an immediate threat to life during a flood, always call 999; for a power cut during flooding, call 105.

• Check for flooding in Tewkesbury. Environment Agency live warnings, river levels and maps at check-for-flooding.service.gov.uk; sign up for flood warnings or call Floodline on 0345 988 1188.
• River Severn at Mythe Bridge gauge. The key level to watch for the town, available on the Environment Agency river levels service.
• Tewkesbury Borough Council. Flood advice, sandbags and the flood warden scheme at tewkesbury.gov.uk.
• Gloucestershire County Council (LLFA). Developer guidance, the SFRA and flood risk management at gloucestershire.gov.uk.
• Gloucestershire Prepared. The county’s Local Resilience Forum, with live road closures and emergency advice at glosprepared.co.uk.

Flood risk assessment in Tewkesbury: frequently asked questions