Flood Risk Assessment in Leamington Spa

A flood risk assessment in Leamington Spa starts with the River Leam, which crosses the town from Newbold Comyn in the east past Jephson Gardens, the Royal Pump Rooms and Mill Gardens. The second question is surface water, which collects in Lillington, Milverton and the Old Town when a storm overwhelms the drains. Our consultants prepare flood risk assessments in Leamington Spa for planning, for buyers and their mortgage lenders and for insurers, together with sequential and exception tests and surface water drainage strategies. Reports for sites in Leamington Spa come from Unda Consulting Limited, a CIWEM Business Partner.

Royal Leamington Spa, to give the town its full name, is taken here as the ONS built-up area of that name. It runs from the Regency centre around the Parade and Clarendon Square to the Old Town south of the river, with the station and the Grand Union Canal, and takes in Milverton to the west, Lillington to the north and Brunswick and Sydenham to the south, all in the CV31 and CV32 postcode districts. Whitnash, which runs into Leamington along its southern edge, is a separate built-up area with its own town council, but it shares the planning authority, the flood authority and the sewerage company, so this page covers it too. Warwick District Council decides planning applications and Warwickshire County Council is the lead local flood authority. Warwick has a page of its own, and Kenilworth and the rest of the county are on our Warwickshire page.

On 10 April 1998 the Leam broke its banks at about 5.30 in the morning, and by 7 o'clock most of Leamington's town centre was under water. The county council later put the flow at a 0.67% annual chance, roughly one year in 150.

Call 01293 214444 or email enquiries@unda.co.uk if you have a site in Leamington or Whitnash you would like a consultant to look at.

The four warning areas along the Leam through Leamington

Before it reaches the town the Leam drains farmland to the east around Long Itchington and Eathorpe, picking up the River Itchen on the way, and it joins the Warwickshire Avon on Leamington's western edge, towards Warwick. The Environment Agency divides the town's river frontage into four flood warning areas, each naming the streets it covers. River Leam at Leamington A is the first:

• Warning area A. Mill Gardens, the Royal Pump Rooms, Pump Room Gardens and parts of Dormer Place, Riverside and Adelaide Road.
• Warning area B. Parts of Leam Terrace, Willes Road, Mill Road, the Parade and Dormer Place.
• Warning area C. Gullimans Way, Priory Terrace, Victoria Terrace, Bath Street, High Street, Euston Place, Riverside and Princes Drive, among others.
• Warning area D. The widest of the four, adding Radford Road, Willes Terrace, Beaconsfield Street, Leam Street, New Street, George Street, Church Street, Augusta Place, Portland Place and Archery Road.
• Upstream alert. A flood alert for the Leam and the Itchen covers low-lying land and roads between Grandborough and Leamington, including Long Itchington.

There is no public river gauge inside the town. The nearest are on the Leam upstream at Eathorpe, where property flooding is possible above 2.30 m and the highest reading is 3.25 m, and downstream on the Avon at Warwick, whose record of 3.95 m was set on the same day, 10 April 1998. Our live river levels map shows both readings against their normal range. The Avon itself passes the southern edge of Coventry before the Leam joins it, and takes the combined flow on to Stratford-upon-Avon. The council's Level 1 Strategic Flood Risk Assessment of October 2022 found much of the town centre at risk from the Leam, and identified the south bank as the part of Leamington most sensitive to climate change.

Look up an address between Lillington and Sydenham

The map below checks any Leamington or Whitnash postcode against the Environment Agency's river, surface water and reservoir datasets; for an address elsewhere in England, use our main flood risk map. The coral line follows the town as ONS draws its built-up area, taking in the centre, the Old Town, Milverton, Lillington, Brunswick and Sydenham. Whitnash, Cubbington, Old Milverton and Warwick all fall outside it, as does the open parkland of Newbold Comyn, though the same councils and the same river evidence apply there.

Leamington's floods on record, from Easter 1998 to Storm Henk

The Leam caused the worst flood on record in Leamington, in 1998. The floods investigated since, in 2005, 2023 and 2024, came from rain the drains could not take. Warwick District's Local Plan names 1998, 2007 and 2012 as the district-wide floods of recent decades, and the county council's records give the Leamington detail:

1. 10 April 1998. After 74 mm of rain over Warwickshire, the Leam came over its banks at about 5.30 am and most of the centre was flooded by 7 am; 20,000 sandbags were found and delivered overnight, according to the Leamington Courier's timeline. The records set that day at the Eathorpe and Warwick gauges still stand.
2. June 2005. Thunderstorms at the end of a heatwave brought more than 100 calls from flooded householders to Warwickshire Fire and Rescue on 24 June, with Warwick and Leamington the worst hit, according to the county's flood history. In Lillington, five homes on Loxley Way and Gresham Avenue reported flooding that month.
3. Summer 2007. Some 2,000 properties flooded across Warwickshire; the county counts six of them in Leamington. Our guide to the Pitt Review and the 2007 floods covers what changed nationally afterwards.
4. 11 June 2023. A storm over the town sent runoff down Pound Lane in Lillington and into twelve homes on Shuckburgh Grove, the event described in the next section.
5. 2 and 3 January 2024. Storm Henk arrived after three months of well above average rain had saturated the county. The Environment Agency sent 27 flood warnings to the county's flood team over 1 and 2 January, and 106 properties flooded internally across Warwickshire. The county's Section 19 report on Storm Henk records one Leamington home, at Lansdowne Circus, where about 1 cm of water got in; the resident put it down to waterlogged ground and the lack of a damp-proof course.

What the Shuckburgh Grove flood showed about Leamington's drains

On the evening of 11 June 2023, 29 mm of rain fell on the Leamington catchment, peaking at 9.7 mm an hour, a storm of between a 5-year and a 10-year return period. The county council's investigation found that water ran down Pound Lane, pooled at the Loxley Way junction and crossed a grass verge into the backs of homes on Shuckburgh Grove, which sit lower than the road and have almost no step at the door. Twelve homes flooded internally, which was enough to trigger a formal investigation under the county's thresholds; our guide to Section 19 flood investigations explains how those work.

The drainage itself was working. Highway gullies feed a Severn Trent surface water sewer, which runs into a culverted watercourse under the Pound Lane Training Centre and a holding pond beyond it, and CCTV surveys found no blockage or collapse that would explain the flooding. The report concludes that the homes would still have flooded given how hard the rain fell on the wider catchment. A site that sits below a road, or at the foot of a slope in Lillington, needs its flow routes traced whatever the flood zone map shows, as our guide to surface water flooding and planning sets out.

The pattern points north of the river. Milverton and Lillington account for most of the town's sewer flooding incidents on Severn Trent's register, while the county's records for Lillington are almost all drainage failures rather than river or overland flooding. The SFRA also notes a major Severn Trent scheme to renew the strategic sewerage system in the town centre. On previously developed land, Policy RLS1 of the Royal Leamington Spa Neighbourhood Plan asks for an assessment of the surface water outfall so that new buildings stop sending rainwater into the combined sewers where another route exists.

Will a soakaway work on Leamington's clays and river gravels?

Under the centre of Leamington and Warwick the SFRA maps siltstone, mudstone and sandstone of the Tarporley Siltstone, Helsby Sandstone and Ashow formations, with river terrace sands and gravels and alluvium along the Leam and the Avon. Clay can lie close to the surface even near the centre: the Lansdowne Circus home that flooded in Storm Henk sits on clay subsoil, and its owner traced the water to saturated topsoil draining sideways into the walls. Warwickshire County Council's Flood Risk Guidance for Development, updated to version 6 in October 2026, says of the county as a whole that it is "underlain predominantly by clayey, impermeable soils and geology and as such, infiltration is rarely capable of providing the final runoff destination".

That does not rule infiltration out on the gravels by the rivers, but it has to be proved. The county expects infiltration tests and, where water will go into the ground, at least six months of groundwater monitoring over the winter, ideally twelve. Our guide to when infiltration testing is required explains the test, the BRE 365 infiltration rate calculator works through the results, and our ground conditions and soakaway checker gives a first read of the geology under an address.

For existing homes, a soakaway serving one property belongs to its owner. Soakaways were left out when private sewers and lateral drains passed to the water companies in 2011, so Severn Trent will not clear one. A blocked or silted soakaway is a common reason for water standing in a garden or against a wall after heavy rain, and our guide to where surface water drains go and who owns them covers how to find out what a house drains to.

Basements, the canal and the defended edges: sites that need a closer look

Some Leamington sites face a risk that a flood zone map does not show on its own:

• Basements and lower ground floors. National policy classes basement dwellings as highly vulnerable, so turning the basement of a Regency house into a flat puts the most sensitive use in the lowest part of the building; national policy does not support it in Flood Zone 3, and in Flood Zone 2 or on a surface water route it needs its own evidence. The planning rules for that change are in our guide to basement and cellar conversions in a flood zone. The draft South Warwickshire Local Plan also warns against retrofitted flood measures that stop traditional walls drying out.
• The Grand Union Canal. The canal runs through the Old Town south of the Leam. The SFRA found no recorded breach or overtopping in the district but asks for any flood risk assessment next to a canal to consider a breach, and the draft plan points to the recent failures on the Bridgewater and Llangollen canals. Our article on why breach data is hard to obtain explains what that involves.
• Behind an embankment. The SFRA lists embankments at Midland Oak Park in Leamington and Saltisford Common in Warwick as the district's main flood defences, built to a 1-in-100-year standard. Land behind them still has residual flood risk if a bank is overtopped or breached.
• Beside the Leam and its brooks. Policy FW1 keeps an 8 m buffer from the top of the bank of every watercourse and does not allow open watercourses to be culverted; our guide to main rivers and ordinary watercourses explains who regulates which channel.

Which policies does a flood risk assessment in Leamington Spa have to answer?

Warwick District Council decides applications against the Warwick District Local Plan 2011 to 2029, adopted in September 2017, and the Royal Leamington Spa Neighbourhood Plan, made in May 2021 after 88.3% voted for it. Warwickshire County Council comments on surface water for major schemes, and the Environment Agency on development by the Leam.

The two councils published the South Warwickshire Local Plan for its final consultation between 21 July and 8 September 2026 and aim to submit it for examination by the end of the year, so its draft policies sit alongside the adopted plan for now. Plans to replace the district and county councils with unitary authorities were paused for a government review in September 2026, and both remain the authorities that decide. For new homes in Flood Zone 2 or 3 the first question is whether a lower-risk site is reasonably available, which is what the sequential test examines.

Riverside House, Court Street, Chandos Street and the land towards the Tach Brook

Inside the town the Local Plan allocates a handful of brownfield sites. Its larger allocations lie on the southern edge between Whitnash, Sydenham and Warwick, where the Tach Brook flows towards the Avon:

• Riverside House (H14). The council's offices on Milverton Hill, allocated for about 100 homes once its present users have moved to new premises.
• Court Street (H16). About 75 homes in the Old Town near the canal, which the council is bringing forward itself.
• Chandos Street (TC4). The car park allocated for a major retail-led town-centre scheme that may include offices, leisure and homes.
• The southern edge. Land west of Europa Way (about 1,210 homes), south of Harbury Lane (about 1,605) and east of Whitnash and south of Sydenham (about 500). The draft South Warwickshire Local Plan lists re-naturalising the Tach Brook among its green and blue infrastructure aims.

Any of the greenfield sites of a hectare or more needs a flood risk assessment even in Flood Zone 1, and each is a major application on which the county council comments on drainage. On the brownfield sites the questions are usually surface water routes, the combined sewers and, at Court Street, the canal.

From a Parade shop to a Lillington extension: when is an assessment needed?

National policy and the Local Plan decide when a report is needed. The table covers the cases we see most often in the town:

For an extension, our guide to building a house extension in a flood zone sets out what a proportionate report covers.

Reports for Leamington's riverside streets, Regency terraces and new estates

The reports below answer the questions Leamington sites raise, whether it is a terrace on Leam Terrace changing hands, a kitchen extension in Lillington or a field south of Sydenham coming forward for homes. Our chartered consultants write them and a senior consultant checks and signs each one.

• Homes and conversions in the Leam corridor. New flats on Bath Street, a change of use on Leam Terrace or a house on Princes Drive each need a flood risk assessment for planning that answers Policy FW1, including its 600 mm floor-level rule.
• The river, the streets and the sewers in one report. A flood risk assessment for a Leamington site weighs the Leam, the runoff routes through Lillington and Milverton, the combined sewers in the centre and the ground beneath it together.
• Before exchange in the Old Town. Where a search flags a terrace by Pump Room Gardens or a flat off Clemens Street, a flood risk survey for property purchase looks at the building itself, its floor levels and its flood history.
• Building homes beside the Leam. Housing proposed in the Leam warning areas has to pass the sequential and exception test before Warwick District Council can grant permission.
• Evidence for the county council. Warwickshire County Council comments on surface water for major schemes, so applications from Riverside House to the edge of Sydenham need drainage strategy work that meets Policy FW2.
• QBAR on clay ground. A surface water drainage strategy tests whether infiltration is possible and, where the clays rule it out, sizes storage so the site drains at the greenfield rate set by FW2.
• Clearing the condition. When a Leamington permission comes with a drainage condition, discharge of drainage conditions supplies the calculations, details and maintenance plan the council needs before building starts.
• Levels where there is no town gauge. With the nearest public gauges at Eathorpe and Warwick, flood modelling can set the design flood level for a riverside site where the national mapping is too coarse.
• Four warning areas, one way out. For a scheme inside one of the four Leamington warning areas, a flood warning and evacuation plan links occupants to the warnings and sets out a dry route to higher ground.
• Homes with a flood history. After the twelve homes flooded in Shuckburgh Grove in 2023, a flood risk assessment for insurance gives an insurer evidence about one address rather than a postcode.
• Gravels by the rivers. The council's SFRA finds groundwater susceptibility higher along the Leam and the Avon, so a groundwater flood risk assessment checks basements, deep foundations and soakaways on the terrace gravels.
• Combined sewers in the old streets. Severn Trent's register holds 64 sewer flooding incidents in the CV32 7 sector alone, and a foul drainage strategy shows how new flats will connect without adding to it.
• Shops in warning area D. Bath Street, High Street and parts of the Parade sit inside a Leam warning area, and a business continuity flood risk assessment plans how a business keeps trading through the next flood.
• Larger commercial buildings. Policy CC3 asks non-residential schemes over 1,000 m2 to reach BREEAM Very Good, so a BREEAM flood risk assessment covers the Pol 03 credits for offices and shops such as those planned for Chandos Street.
• Land on the southern edge. Before an offer on land south of Sydenham or Harbury Lane, a flood risk feasibility study shows early how much of it can be built on and drained.
• The national tests behind FW1. Our NPPF flood risk guidance explains how chapter 18 of the NPPF and its policies on the sequential and exception tests apply to a Leamington scheme.

Who to contact about flooding in Leamington, from Floodline to the canal

In a flood, several bodies share the work in Leamington, and the right one depends on where the water is coming from:

Warwickshire County Council publishes its Local Flood Risk Management Strategy and Surface Water Management Plan, which set out how it ranks flooding locations for investment.

Leamington questions: soakaways, Storm Henk and the sequential test

To talk about a house on Leam Terrace, a basement in the Regency centre or land south of Whitnash, call 01293 214444 or email enquiries@unda.co.uk. Unda Consulting Limited will check the address against the Leam, the warning areas and the local policies and set out the reports the site calls for.