Flood Risk Assessment in Wraysbury

A flood risk assessment in Wraysbury starts from January 2024, when the Thames, and then the groundwater beneath the village, flooded more properties here than in any other parish of the Royal Borough of Windsor and Maidenhead. Wraysbury lies on the Berkshire bank of the river between Old Windsor and Staines, with the Colne Brook running down its eastern side to Hythe End. Our consultants prepare flood risk assessments in Wraysbury for planning applications, house purchases, mortgages and insurance, together with sequential and exception tests and surface water drainage strategies.

On this page Wraysbury means the civil parish, 6.7 km² of land between the Thames and the lakes. It takes in the old village around The Green and the High Street, and Sunnymeads to the north along Welley Road and The Avenue. Hythe End lies in the south-east beside the Colne Brook, and the riverside runs from Friary Island down to Magna Carta Island and the Ankerwycke estate. Addresses carry a Staines postal town and the TW19 postcode district, yet Spelthorne Borough Council does not decide applications here. The parish moved from Buckinghamshire to Berkshire in 1974, and the Royal Borough is both its planning authority and its Lead Local Flood Authority.

After Storm Henk in January 2024 the Royal Borough recorded 46 properties flooded inside and 116 flooded outside in Wraysbury parish, and some gardens were still under water four months later.

To talk through a plot in Wraysbury, Sunnymeads or Hythe End, call our flood risk consultants on 01293 214444 or email enquiries@unda.co.uk.

What the Storm Henk investigation found in Wraysbury

The Royal Borough's Section 19 report on the January 2024 Thames flooding, published in January 2025, is the fullest account so far of how the parish floods. External flooding was reported from 1 January, the first water inside a home on 7 January, and the Thames peaked at Wraysbury on 8 January. Of the 271 properties reported affected across the borough, 162 were in Wraysbury. The council expects the true figure to be higher, because some owners do not report flooding for fear of what it does to their insurance or mortgage.

• Where nothing holds the river. The Thames came out of bank at several points, mostly where there is no defence of any kind, and ran south across the parish to rejoin the main channel around Hythe End, along what the report takes to be old routes of the river.
• A gap at The Avenue. An informal earth bank runs behind many homes in the north of the village. One section had been levelled when a property was redeveloped, and floodwater came through the gap and under the new building's flood void, closing Welley Road and reaching neighbouring homes.
• Lakes that rose and stayed up. That water carried on east into the large lake north of the village, which residents say rose by about six feet. With no outflow, it took around four months to fall back.
• Groundwater in the gardens. Water rose through the gravels into gardens on Ouseley Road, Wharf Road and Garson Lane and onto the village green. On Hythe End Road some homes were reached by groundwater flowing from the fields to the north before the river arrived from the south.
• A drain that could not clear it. The Wraysbury Drain normally takes water from the green to the Thames at Hythe End, but it was obstructed downstream at Hythe End and on the Ankerwycke land, so standing water lingered for months.
• Raised homes, blocked channels. Houses on Friary Island and Wharf Road built up since 2014 fared better, though a side channel on Friary Island, partly blocked by driveways, may have pushed water towards neighbours.
• Cut off by road. Welley Road was closed, Hythe End Road, The Island, Friary Island, King John's Close and Feathers Lane were cut off, and with Horton Road and Datchet Road shut to the north, traffic had to go round by the M25 or through Surrey. Sunnymeads station closed.

Two of the report's eight Wraysbury recommendations bear on planning. The Environment Agency is to consider reinstating the bank at The Avenue, and the Royal Borough and the Agency are to make sure applications pick up informal defences, so that new building does not remove them. A flood risk assessment for a Wraysbury plot should therefore record any bank, wall or raised edge on or beside the site and show how the scheme keeps it working. Our guide to Section 19 flood investigations explains how councils decide which floods to investigate.

Screening a Wraysbury, Sunnymeads or Hythe End postcode

Type a postcode into the map below to screen it against Environment Agency data for rivers and the sea, surface water and reservoirs, or open our full flood risk map for anywhere in England. The coral line follows the Wraysbury parish boundary. Old Windsor lies across the Thames to the west, with Runnymede facing Magna Carta Island; Horton and the Queen Mother Reservoir lie to the north and Datchet beyond them; Staines and Egham are downstream past Hythe End. The planning flood zones ignore defences, and along most of Wraysbury's riverside there are none to ignore.

River, brook, gravel and drain: where Wraysbury's water comes from

River flooding comes first in Wraysbury, but 2024 showed it seldom arrives alone. The parish sits on Thames gravels and is ringed by flooded gravel pits. The Royal Borough's 2017 Level 1 SFRA warns that high river levels lift the groundwater in those gravels, so land well back from the bank can flood from below.

The Royal Borough's drainage guidance states that, as Lead Local Flood Authority, it is not a statutory consultee on groundwater, so the groundwater case in a Wraysbury application has to stand on its own evidence. The 2024 report notes that the groundwater monitoring station at Windsor Road in the village had recorded nothing since September 2023. Our article on groundwater evidence for planning applications sets out what is usually submitted. The catchments themselves are covered on our pages for the River Thames and the River Colne; despite its name, the Wraysbury River runs east of the reservoirs through Staines Moor, outside the parish.

Wraysbury flooding from 1947 to 2024

Floods in the parish come from long, slow Thames events measured in days and weeks, not hours. The dates below come from the Royal Borough's own flood history, its 2024 investigation and the Environment Agency's papers on the reach.

1. 1947. The most notable of the reach's floods, in the Environment Agency's words. The Royal Borough's history lists extensive flooding from the Thames in Wraysbury, Datchet and Old Windsor, among other places.
2. January 2003. River and groundwater flooding in Wraysbury. About 128 houses were affected across the borough, many of them in Wraysbury and on Ham Island in Old Windsor.
3. Winter 2013 to 2014. Prolonged Thames flooding across the borough, from Hurley down to Wraysbury. On 13 February 2014 the government reported around 100 soldiers of the 1st Battalion, Royal Regiment of Fusiliers still at work in Wraysbury, filling sandbags and helping residents. The Colne Brook gauge at Hythe End had reached its highest recorded level two days earlier.
4. July 2020. The River Thames Scheme's sponsors decided to go ahead without Channel 1, the relief channel planned from Datchet to Hythe End past Wraysbury.
5. January 2024. Storm Henk, when Wraysbury saw the widest flooding in the borough, as set out above. Groundwater kept the village green out of use until the summer.
6. July 2026. The Royal Borough's Flood Liaison Group heard that the Environment Agency's option assessment for the Datchet to Hythe End measures was complete and funding was being sought, and that reinstatement works on the Wraysbury Drain were on hold.

Thames and Colne Brook levels can be followed as they change on our live river levels map. The Environment Agency's Colne Brook gauge at Hythe End sits inside the parish and shows where the brook stands against its normal range.

Channel 1 and the defences Wraysbury does not have

Wraysbury has no formal flood defence along its stretch of the Thames. The Environment Agency describes the river from Datchet to Teddington as one of the largest areas of undefended, developed floodplain in England, and the channel meant to change that for Wraysbury has not been built.

The River Thames Scheme once included Channel 1, a flood relief channel from Datchet to Hythe End. In July 2020 the scheme's sponsorship group decided to go ahead without it, because it could not be paid for without more funding or more flexibility over council tax, and the Royal Borough's original £10 million commitment remains available for other flood works (Environment Agency). Borough Local Plan policy NR1 still safeguards land for the flood relief channel from Datchet to Wraysbury, although the plan's supporting text records that Channel 1 is not proceeding at present.

Its replacement, the Datchet to Hythe End flood improvement measures, covers about 2,500 properties. Two options are shortlisted, flood walls and embankments or a relief channel, with property-level measures considered alongside, and none is yet funded. Meanwhile the 2017 SFRA lists a temporary defence deployment plan for Wraysbury, intended to protect against a 1 in 30 year flood. A temporary barrier does not change a site's flood zone.

The River Thames Scheme now in design covers the Runnymede and Spelthorne reaches downstream, and as our article on why the River Thames Scheme is delayed explains, it had no development consent order or construction date in September 2026. Until a scheme for Wraysbury is funded and built, an assessment here works from the undefended position, and the residual risk from any local bank or raised ground is assessed as an addition to it, not a substitute.

Zone 3b, policy NR1 and the Horton and Wraysbury Neighbourhood Plan

Three layers of policy apply to a site in the parish: chapter 18 of the NPPF, the Royal Borough's Borough Local Plan 2013 to 2033, adopted on 8 February 2022, and the Horton and Wraysbury Neighbourhood Plan, made on 23 June 2020 after an 83% vote in favour at referendum. Underneath all three sits the SFRA, which places a large proportion of its Wraysbury and Horton character area in Zone 3b, the functional floodplain.

• Zone 3b from the 1 in 20 outline. The SFRA draws the functional floodplain from land flooded in the 5% annual chance event and treats the footprints of existing buildings within it as Zone 3b Developed. Where no 5% outline has been modelled, it treats the whole 1% outline as functional floodplain until a site assessment shows otherwise; our explainer on Flood Zone 3b covers the national definition.
• NR1 in the functional floodplain. Policy NR1 supports only water-compatible uses and essential infrastructure there. Elsewhere it requires the sequential test for all development at risk except on allocated sites, and asks schemes to add floodplain storage where they can, use SuDS, build in resilience and provide safe access, egress and evacuation plans.
• An 8 m strip by the water. NR1 also keeps an undeveloped 8 m buffer from the top of the bank on both sides of a main river, which here means the Thames and the Colne Brook, and on ordinary watercourses such as the Wraysbury Drain where practicable.
• Neighbourhood Plan policy NP/SUSTDEV 02. New homes and other new development in Flood Zones 2 and 3 are not supported, apart from the one-for-one replacement of houses and extensions up to the size that permitted development rights allow.
• Dry islands and a way out. The plan's supporting text accepts new homes on land above the 1 in 1,000 year flood level only where residents have a safe route to land outside the flood. It names Staines Road as the evacuation route that worked in recent floods, and warns that water can stand for weeks.
• Building back smaller and higher. The SFRA expects redevelopment in the floodplain to cut the built footprint by at least 5%, to replace any lost flood storage level for level with at least 5% extra, and to set floor levels at least 300 mm above the 1% plus climate change flood level.

The SFRA's April 2018 Level 2 report shows how those rules meet real land in the parish. It found a candidate housing site at Tithe Farm, Tithe Lane, mostly in Flood Zone 2, with no apparent safe access or egress, and the World of Water site on Wraysbury Road with nearly 75% of its area in the functional floodplain. For both it said an evacuation or emergency plan would have to be agreed with the Royal Borough and the Environment Agency. Our article on dry island sites explains why isolation alone can stop an application, and the NPPF's approach to the sequential test decides whether a lower-risk site has to be preferred.

On drainage, the Royal Borough's SuDS guidance for major schemes follows the 2025 National Standards, which policy F8 of the NPPF expects all development to meet. Because the borough is a water-stressed area, it always expects rainwater to be collected for reuse, and it lets long-term storage drain at no more than 2 l/s/ha. On the gravels, infiltration has to be tested against a water table that can sit close to the surface in winter; our geology and ground conditions map gives a first indication before any trial pit.

Replacement houses, extensions and dry islands: when a flood risk assessment in Wraysbury is needed

Most building in the parish is the rebuilding and extending of existing homes, as the Neighbourhood Plan itself records, and in Flood Zones 2 and 3 that work needs a flood risk assessment. The table gives the usual position for each kind of proposal; the plot's zone on the Flood Map for Planning, and the SFRA's Zone 3b mapping, settle it.

Whatever is proposed, the floor and the ground beneath it matter as much as the zone. The 2024 report notes that new building in Wraysbury's Flood Zone 3 is expected to stand over voids that let floodwater pass, and our explainer on floodable voids covers how they are specified. The Avenue showed what else is needed: a void works only inside a layout that leaves the neighbouring banks in place. Rebuilding is covered in more depth in our guide to replacing a house in a flood zone, and extensions in building an extension in a flood zone.

Reports our consultants prepare for Wraysbury, Sunnymeads and Hythe End

We prepare reports in Wraysbury for applicants, home buyers, owners and insurers. Each one below answers a different question, and on a riverside plot several often go in together.

• Rebuilds and extensions. Most applications in the parish need a flood risk assessment for planning that answers policy NR1, the Neighbourhood Plan and the SFRA's Zone 3b mapping.
• Every source on one plot. A flood risk assessment weighs the Thames and the Colne Brook against groundwater in the gravels, the Wraysbury Drain and the vacuum sewers.
• Before buying in Wraysbury. Home buyers on the riverside or near the lakes can commission a flood risk survey for property purchase that looks at the house itself, its floor levels and how its street fared in 2014 and 2024.
• Homes in Zone 2 or 3. A replacement house counts as a new dwelling, so the sequential and exception test goes in with the assessment.
• Water-stressed and on gravel. Any drainage strategy here has to show rainwater reuse and infiltration tested against a high water table.
• Major schemes. A surface water drainage strategy meets the Royal Borough's SuDS guidance and the 2025 National Standards, including the 2 l/s/ha limit on long-term storage.
• After permission. Discharge of drainage conditions supplies the drainage detail and maintenance plan that a Wraysbury condition asks for.
• Proving the 1 in 20 outline. Where the SFRA has no 5% outline for a plot, flood modelling can show whether it truly lies in the functional floodplain.
• No dry way out. Sites like the two the Level 2 SFRA tested without safe access need a flood warning and evacuation plan agreed with the Royal Borough and the Environment Agency.
• Gardens wet for months. Where groundwater lingered in 2024, a groundwater flood risk assessment sets a design water level for floors, voids and soakaways.
• Cover after Storm Henk. Where an insurer has loaded a premium since 2024, a flood risk assessment for insurance sets out the house's own floor levels and flood history for the underwriter.
• Vacuum sewers. On a network the Neighbourhood Plan calls vulnerable to flooding, a foul drainage strategy shows how a scheme's wastewater will be handled.
• Businesses on the floodplain. Five commercial premises in Wraysbury flooded inside in 2024, and a business continuity flood risk assessment helps an occupier plan for the next event.

Flood wardens, warnings and the Royal Borough: contacts for Wraysbury

If a flood threatens life, call 999, and for a power cut during flooding, call 105. Beyond that, each of the bodies below handles a different part of flood risk in the parish.

Sign up for free flood warnings for the Wraysbury areas, including the separate warning for properties closest to the river from Old Windsor Weir to Magna Carta Island and the Colne Brook warning that names Horton and Wraysbury. The Royal Borough's Flood Liaison Group brings the parish councils together with the Environment Agency and Thames Water, and its July 2026 minutes record that reinstatement works on the Wraysbury Drain are on hold while a camera survey of Feathers Lane goes ahead.

Wraysbury sites and flooding: questions buyers and applicants ask

Our flood risk consultants are chartered, Unda Consulting Limited is a CIWEM Business Partner, and a senior consultant signs off every report. For a site anywhere in the parish, call 01293 214444 or email enquiries@unda.co.uk. For the rest of the county, see our page on flood risk in Berkshire, or browse all the areas we cover.