Flood Risk Assessment in Melksham

A flood risk assessment in Melksham, Wiltshire, has three rivers to deal with inside the town itself. The Bristol Avon flows past the town centre under the Town Bridge, and two smaller main rivers run through the town to join it: Clackers Brook from Melksham Forest and Lowbourne in the east, and South Brook from Shaw in the north-west. People applying for planning permission, buying a home, arranging a mortgage or renewing insurance ask our consultants for flood risk assessments in Melksham, and for sequential and exception tests and surface water drainage strategies.

Here, Melksham means the built-up town that the Office for National Statistics maps. That takes in the centre and Market Place, Lowbourne, Melksham Forest, the Queensway estates, Scotland Road, the Northbrook and Southbrook streets and the newer housing off Snowberry Lane, all in the SN12 postcode district. Bowerhill and Berryfield to the south, and Beanacre, Shaw and Whitley to the north, belong to Melksham Without, the parish that wraps round the town on three sides. Wiltshire Council decides planning applications in both and is the lead local flood authority.

On Monday 25 November 2024, in Storm Bert, the Avon came out of its banks and flooded homes and businesses on Bath Road, Avonside and Broughton Road, the most serious flooding the town had seen since July 1968.

Ring 01293 214444 or email enquiries@unda.co.uk with the Melksham address. Before quoting, we look at where it sits against the town's flood warning area, the two brook corridors and the council's 2025 site studies.

Is Melksham in a flood zone? The Avon, Clackers Brook and South Brook

Parts of it are. Flood Zones 2 and 3 follow the Avon through the middle and reach up both brooks into the streets either side. Unda's own overlay of the Environment Agency's Flood Map for Planning on the ONS outline puts about an eighth of the built-up town in Flood Zone 2 or 3, and about 4% in Flood Zone 3.

One Environment Agency warning area, Bristol Avon (mid) at Melksham, covers all three rivers, and a second covers the Avon upstream from Chippenham through Reybridge and Lacock. Each brook has its own gauge. Clackers Brook at Melksham normally sits below 0.60 m and reached its highest recorded level, 1.47 m, on 23 September 2024. South Brook at Shaw peaked at 1.71 m on 12 January 2023 against a normal top of 0.80 m. Both feed our live river levels map.

Melksham on the flood map, street by street

Enter a Melksham postcode to see the planning flood zones, the surface water extents and any warning in force at that address, or open our flood risk map to look further afield. The coral line follows the ONS built-up area, so Bowerhill, Berryfield and some of the open land beside the Avon fall outside it.

Wiltshire Council's countywide Level 1 strategic flood risk assessment, prepared by JBA Consulting in November 2024, lists Melksham among the urban centres most exposed to river flooding, alongside Bradford on Avon, Malmesbury and Salisbury. Its online data explorer shows groundwater emergence, sewer incidents and recorded floods for any site in the town.

Storm Bert and the floods before it: Melksham's record since 1925

The Environment Agency has mapped floods in Melksham for a century, and nearly all of them came from a river that could not hold the water: the Avon on its own, or the Avon with Clackers Brook or South Brook backing up behind it.

1. January 1925. The Avon spread across a large part of what is now the town, and South Brook flooded at Shaw in the same month.
2. May 1932. Clackers Brook and the Avon overtopped together, leaving the largest outline the Agency has drawn inside today's built-up area.
3. December 1960 and July 1968. Two more Avon floods. In 1968 the town was cut off, and army lorries carried children across the river to Lowbourne; Broughton Road and its junction with Lowbourne were among the worst hit, according to the town's historical association.
4. December 1979 and March 1982. The Avon flooded from Challymead Bridge downstream, and in 1982 the Agency recorded the river overtopping defences in Melksham.
5. 1992 to 2014. Further Avon floods in December 1992, January 1999, February 2009 and April 2012; a flood on the stream the Agency calls Forest Brook in November 2012; and the winter of 2013 to 2014, which the neighbourhood plan says hit parts of the area hard.
6. January 2023 and September 2024. Each brook set a new record at its gauge: South Brook at Shaw on 12 January 2023 and Clackers Brook on 23 September 2024.
7. 25 November 2024, Storm Bert. After prolonged heavy rain the Avon broke its banks. Water covered Bath Road until police shut it, and Bradford Road and New Broughton Road closed. A family on Broughton Road had two feet of water indoors by 11am, and homes and businesses at Avonside and the former Avon factory site flooded, as Melksham News reported.

Wiltshire Council's leader later said Chippenham and Melksham had seen their worst flooding since the 1960s. Seven months on, two of the flooded businesses, Sanmax and Melksham Cycle Centre, had only just reopened after taking in about two and a half feet of water, the paper found. No published investigation counts the Melksham properties that flooded, so a riverside site is judged on its levels, the warning area and the recorded outlines.

South Brook and Clackers Brook: the quick-rising streams

• A priority catchment. The Joint Melksham Neighbourhood Plan 2 records that the Environment Agency and Wiltshire Council both treat the South Brook catchment as a priority flood risk area for surface water, and the Bristol Avon Rivers Trust has been carrying out natural flood management there.
• Runoff from north of Whitley. The plan describes many small drainage streams from north of Whitley running into the First Lane area, which adds to the risk in the north-west of the parish.
• Flashy by nature. Shaw and Whitley's community emergency group warns that any hardening of surfaces upstream shows quickly at the gauge by Shaw school and raises the risk downstream. The plan therefore asks drainage strategies to cope with the 1 in 100 year storm plus climate change.
• Clackers Brook at Lowbourne. Parts of Lowbourne flood from the brook, and the plan expects any scheme for older residents on the former library site to show how they would get out safely when it does.
• Volunteers on watch. The plan names one local response: recruiting and training residents as flood wardens who monitor the brooks and act as soon as water rises.

Our guides to natural flood management schemes and surface water flooding and planning explain how upstream works and on-site storage are weighed in a planning decision.

What a flood risk assessment in Melksham must satisfy under Core Policy 67 and the 2025 neighbourhood plan

Melksham applications are decided under the Wiltshire Core Strategy, the Joint Melksham Neighbourhood Plan 2 and the council's drainage standards, as well as national policy. Voters in Melksham and Melksham Without backed the neighbourhood plan by 1,903 votes to 239 on 31 July 2025, and it has been part of the development plan since August that year.

The draft Wiltshire Local Plan to 2038 was withdrawn in May 2026, and a new plan is not due for adoption until 2029. The council's Level 2 strategic flood risk assessment of February 2025, written for the withdrawn plan, still gives the most detailed published view of two Melksham sites. It recommends floor levels 600 mm above the 1% annual probability flood plus climate change. Our explainers on the 2025 National Standards for SuDS and lead local flood authority objections cover what the drainage officers will look for.

Cooper Tires, Lowbourne and the land east of the town

The sites in the neighbourhood plan and the council's 2025 study split between brownfield land near the river and greenfield land at the edge of the town, and each raises different flood questions.

• The former Cooper Tires factory. The neighbourhood plan found flood zones 2 and 3 and contamination leave only about a quarter of the site readily available for homes. It allocates about 100 dwellings on the Flood Zone 1 land up to 2038 and expects regeneration to run on beyond that.
• The former library, Lowbourne House. A town-centre site the council owns, allocated for extra care apartments, where the access route has to work when the brook is in flood.
• Land east of Melksham. The Level 2 study found surface water flow paths crossing this draft site, possible access problems from flooded roads around it, recorded flood outlines inside it and a high cumulative impact rating for most of it.
• Land off Bath Road. The same study rated the whole site high for cumulative impact, noted recorded sewer flooding in its postcode area and pointed to the old canal along its eastern edge.
• Snarlton Farm. Wiltshire Council's strategic planning committee refused up to 300 homes here on 5 August 2025, a day after the neighbourhood plan was made, finding that the homes did not outweigh the scheme's conflict with it.

Reports for Melksham sites, from Lowbourne to the riverside

Each report is scoped to the address and to whoever has asked for it: how close the site is to the Avon or a brook, which of the plan's policies apply, where the water can drain, and what a lender, an insurer or the council needs to see.

• Applications to Wiltshire Council. New homes or commercial space in Flood Zone 2 or 3 beside the Avon, Clackers Brook or South Brook, or any site of a hectare or more, needs a flood risk assessment for planning that answers Core Policy 67 and the neighbourhood plan's Policy 3.
• Three rivers in one small town. The town's recorded floods have come from the Avon and from each of its brooks, so a flood risk assessment here weighs all three alongside surface water and the sewers.
• Buying on a street the warning names. A house on Broughton Road, Lowbourne or Southbrook Road lies inside the Environment Agency's Melksham warning area, and a flood risk survey for property purchase looks at its floor level, air bricks and history before contracts are exchanged.
• Riverside windfall sites. Infill or a change of use on land in Flood Zone 2 or 3 near the Town Bridge, which the neighbourhood plan does not allocate, has to show through the sequential and exception test that no lower-risk site in the area would serve.
• A cut in runoff, not a match. Wiltshire's June 2024 betterment rules ask brownfield sites in the town centre for at least a 30% reduction in discharge where greenfield rates cannot be reached, which a drainage strategy has to evidence.
• Slowing the flashy South Brook. North-west of the centre, a surface water drainage strategy has to hold storm runoff to the 1 in 100 year event plus climate change, because any hardening of the catchment shows up quickly at the Shaw gauge.
• After the decision notice. Schemes approved under the neighbourhood plan's site policies usually carry drainage conditions, cleared through the discharge of drainage conditions with the calculations, exceedance routes and maintenance plan the officers ask for.
• Where two rivers meet. Clackers Brook and South Brook both run through the town to the Avon, and a high river can hold back the water in either, so some sites need flood modelling to set floor levels the national maps cannot.
• Getting out of Lowbourne. The neighbourhood plan asks for an emergency access strategy for older residents at the former library site, and a flood warning and evacuation plan ties a building to the Agency's Melksham warnings.
• Renewing cover after 2024. Households on Broughton Road and Avonside whose homes took in water during Storm Bert can give an underwriter an insurance flood risk assessment for the individual property.
• Bath Road trade. Two businesses flooded in Storm Bert took about seven months to reopen, and a business continuity flood risk assessment helps an occupier plan stock, power and access for the next flood.
• Brownfield land by the river. Flood zones and contamination limit the housing land on the former Cooper Tires factory to about a quarter of the site, so buyers and lenders looking at it, or at neighbouring yards, commission flood risk due diligence before they commit.

Bowerhill, Berryfield and the villages of Melksham Without

Bowerhill and Berryfield are mapped by the ONS as separate built-up areas, and the neighbourhood plan allocates land south of Western Way at Bowerhill. Shaw and Whitley sit in the South Brook catchment, Beanacre lies near the Avon upstream, and Semington Brook runs to the south, where its gauge recorded 3.30 m on 28 December 1979. The same council policies apply in each, and our Wiltshire page covers the rest of the county.

Upstream the Avon passes through Chippenham on its way to Melksham, and downstream it reaches Bath after Bradford on Avon. Warminster, on the chalk to the south, faces a different mix of river and groundwater. Our areas page lists every other town and county page.

River, brook, drain or sewer: who to call about flooding in Melksham

Who deals with a flood in Melksham turns on its source. The Environment Agency answers for the Avon and both brooks, Wiltshire Council for roads, surface water and ordinary watercourses, and Wessex Water for the public sewers. Anyone in danger from floodwater should call 999 first.

Questions to settle before a flood risk assessment in Melksham

For a terrace in Lowbourne, a plot off Snowberry Lane or a unit beside the river, call 01293 214444 or email enquiries@unda.co.uk. Unda Consulting Limited is a CIWEM Business Partner, our consultants are chartered, and a senior consultant checks and signs off every report before it is submitted to Wiltshire Council.