Flood Risk Assessment in Woking

A flood risk assessment in Woking is mostly about two small watercourses and a canal rather than a big river. The Hoe Stream runs through Mayford, Westfield and Kingfield to the Wey at Old Woking, the Rive Ditch drains Horsell Common through Maybury, and the Basingstoke Canal crosses the middle of the town. Our consultants prepare flood risk assessments for planning, house purchases, mortgages and insurance, along with sequential and exception tests and surface water drainage strategies, for sites anywhere in the town.

On this page Woking means the built-up area mapped by the Office for National Statistics, in the GU21 and GU22 postcode districts: the town centre, Horsell, Goldsworth Park, St John's and Knaphill to the west, Maybury and Mount Hermon to the east, and Hook Heath, Kingfield, Westfield, Mayford and Old Woking to the south. Byfleet, West Byfleet, Sheerwater, Pyrford and Brookwood belong to the same borough but are mapped as separate places, and Send, across the Wey, is in Guildford borough.

On 11 May 2016 a storm stalled over Maybury, dropped about 32 mm of rain in two hours, and 45 properties flooded internally when the Rive Ditch and the sewers feeding it overflowed.

To talk through a Woking site, ring 01293 214444 or write to enquiries@unda.co.uk with the address and the plans, and a consultant will say which reports it needs.

Is Woking in a flood zone? Two streams, the Wey and a canal

Woking sits largely outside the river flood zones. Our own overlay of the Environment Agency's flood map for planning on the town's outline puts about 7% of it in Flood Zones 2 and 3, and about 2.4% in Flood Zone 3, almost all of it along the Hoe Stream between Mayford and Old Woking and on the Wey meadows east of Old Woking. The north of the town, from Horsell to Maybury, has very little river flood zone, but it is where the surface water and sewer records cluster. The Agency's warning and alert areas for the town are these:

Two gauges matter here. The Hoe Stream gauge at Woking South, in Mayford, normally reads 0.30 m to 1.50 m; low land can flood above that and property above 2.22 m, the level it reached on 14 August 2006, its highest. On the Wey at Old Woking the normal range is 1.00 m to 3.20 m, property can flood above 3.66 m, and the record is 3.94 m, set on 24 December 2013. Both readings update on our live river levels map.

Check a GU21 or GU22 address on the map

Type a Woking postcode below to see the river and surface water flood extents around it, or use our full flood risk map further afield. The coral line follows the town as the Office for National Statistics draws it, which leaves Byfleet, West Byfleet, Sheerwater and Pyrford outside. The map does not show the canal's breach risk or the places where sewers have flooded, which in Woking often decide a site.

The Hoe Stream from Mayford to Old Woking, and the 2012 defences

The Hoe Stream rises at Tickners Bridge near Normandy and drains about 85 square kilometres before it meets the Wey at Newark Lock. Its lower reach runs through the south of Woking, and the borough's Strategic Flood Risk Assessment of November 2015, prepared by Capita, calls that part of the catchment heavily urbanised. The stream flooded Old Woking, Kingfield and Mayford in December 2000 and set its gauge record in August 2006. A flood alleviation scheme followed, led by Woking Borough Council with the Environment Agency as its flood defence partner.

• What was built. Earth embankments, some clay-lined, with concrete and sheet-pile walls along about 2 km of the stream, from north Mayford to just below Elm Bridge, plus two new ponds, a re-routed channel at Elm Bridge and non-return valves.
• What it changed. The SFRA estimates almost 200 homes were taken out of the floodplain, and the Environment Agency counts more than 80 properties protected. The scheme was completed in 2012.
• How it was tested. A 2014 model of the Hoe Stream measured the scheme's benefit, mapping the 1 in 20, 1 in 100 and 1 in 1,000 year floods with and without the defences, and its undefended outlines went into the Environment Agency's flood map.
• What is left. The SFRA describes most of the very high risk land along the stream as parkland, but it flags the A247 crossing, where property and roads can still flood, and gardens on the south side of White Rose Lane.

Behind the walls, a flood risk assessment on the Hoe Stream works out what happens if a flood bigger than the defences were built for overtops them, using today's climate change allowances, and how people would get out.

Maybury's flash floods: the Rive Ditch in 2016

The Rive Ditch shows how quickly the north of the town can flood. It rises on Horsell Common as an ordinary watercourse, goes into a culvert near Monument Way West, runs as a Thames Water surface water sewer in a 750 mm pipe, and only opens up again, as main river, north of Woodlands Avenue east of Sheerwater. From there it passes under the Basingstoke Canal and the Wey Navigation. Surrey County Council's Section 19 report on the May 2016 flood sets out what happened when that system filled:

1. July 2007. Walton Terrace, Princess Road and Boundary Road in Maybury flooded from surface water, and a blocked grille where the ditch passes under the canal flooded the land beside it.
2. 11 May 2016, 11.00 to 13.30. A storm stalled over Woking. Radar put 31.7 mm on Maybury between 11.00 and 13.00, about two thirds of a normal May's rain at Wisley.
3. Early afternoon. The ditch reached capacity, sewers and gullies surcharged, and water ran overland into low streets. Forty-five properties flooded inside across Maybury and West Byfleet, three schools closed, and the council handed out 1,500 sandbags.
4. 16 September 2016. A night storm flooded the same streets again: seven properties inside, around Walton Terrace and in West Byfleet.

No flood alert went out in May 2016, because the Wey gauges did not respond to so short a storm and the ditch had no warning service of its own; the Environment Agency now runs a warning for the Rive Ditch at Woodham and New Haw. Our article on Section 19 flood investigations explains what these reports are and how planners use them.

Where the Wey reaches Old Woking

The Wey forms the town's south-eastern edge, and its floodplain widens to about 2 km at the Hoe Stream confluence. The SFRA notes that on its lower reach the river runs over London Clay, so it responds quickly to heavy rain. Floods are recorded around Old Woking and Westfield in September 1968, and over Christmas and New Year 2013 to 2014 the Wey overtopped into Old Woking High Street together with surface water. Its course, gauges and wider history are covered on our River Wey page; for a site here, the questions are the Old Woking flood levels and whether the access road stays dry.

Surface water, sewers and a high water table near the canal

Away from the two streams, the SFRA's evidence points to heavy rain, overloaded sewers and, in a few places, shallow groundwater. Woking has no designated critical drainage areas, so these records are the main guide to where a site in Flood Zone 1 still needs a closer look.

The canal follows the contours, and in places its water is retained by banks built from its own spoil. The SFRA records that it burst its banks in two places in September 1968, outside the borough, an event that led to the canal's restoration; the canal authority reports very few or no incidents in the last 20 years. The risk is residual, and the SFRA asks the council to weigh canal breach when it chooses development sites, so an assessment for land below the bank should deal with it; our piece on canal failures and planning explains why. Our article on sewer flooding covers the Thames Water side.

Policy CS9: when a flood risk assessment in Woking is needed

Woking Borough Council decides applications under its Core Strategy, adopted on 25 October 2012 and reviewed in 2018 and on 12 October 2023, with the Development Management Policies of October 2016 and the Site Allocations plan of October 2021. Two parts of its flood policy, CS9 Flooding and water management, shape most Woking applications: it treats Flood Zone 2 as a last resort, and it asks for an assessment for development within or next to areas at risk of surface water flooding, in Flood Zone 1 as much as anywhere.

Above the local plan sits chapter 18 of the NPPF: policy F4 on when an assessment is needed, F5 and F6 on the sequential and exception tests, and F8 on the 2025 National Standards for sustainable drainage. Our Flood Zone 3b explainer covers what the functional floodplain rules out, and our Surrey page puts Woking alongside the other ten boroughs.

Surrey County Council's drainage rules for Woking sites

Surrey County Council, the lead local flood authority, is a statutory consultee on surface water for major schemes, and its SuDS planning advice has applied the June 2025 national standards to every new consultation since 6 October 2025. For smaller schemes it gives a response only where the site lies in the 1% surface water extent or next to a watercourse.

• Rainwater first. Surrey is classed as water stressed, so the county expects roof water to be collected for reuse on every scheme, with a lower outfall as well.
• The 1 in 2 year rate. Most sites that add runoff volume are held to the 1 in 2 year discharge rate, and a brownfield allowance is accepted only in exceptional cases.
• Soakaways with a margin. Infiltration needs BRE 365 test results with the application and a metre of unsaturated ground above the seasonal high water table, a hard test on the Old Woking gravels, where the SFRA finds the borough's highest groundwater susceptibility.
• Nothing onto the road. No new private surface water may drain to the highway or into highway drains, and designs allow 10% for urban creep.

Where a scheme would discharge to the Rive Ditch or the Hoe Stream, the county also wants proof that the watercourse downstream can take the flow. Our article on the 2025 national standards for sustainable drainage sets out the standards the county now tests against, and the lead local flood authority explainer covers its role.

A new Local Plan and a new council from 2027

Woking's next plan will run from 2027 to 2044. Work formally began on 25 September 2026, the council's published timetable puts a consultation on its content from 6 January to 19 February 2027, a draft plan in early 2028 and adoption in April 2029, and until then CS9 and the 2015 SFRA remain the tests. From 1 April 2027 the new West Surrey Council takes over from Woking Borough Council and Surrey County Council in the borough, as the planning authority and the lead local flood authority. Our article on local government reorganisation covers what that means for applications in progress.

From a Horsell loft to a Mayford infill: the reports a Woking site needs

The flood zone, the surface water record and the size of the scheme decide most of it. These are typical Woking proposals; we confirm the set for the real address before quoting.

Reports we write for Woking addresses

Each of these starts from the Woking evidence above, not from the flood zone alone:

• The whole picture. A flood risk assessment for a Woking address weighs the Hoe Stream, the Rive Ditch, the Wey, the canal, the sewers and the water table together.
• With the application. Woking Borough Council expects a flood risk assessment for planning that answers CS9, including its surface water trigger in Flood Zone 1.
• Before buying. A flood risk survey for property purchase looks at the house itself, which matters most in the defended streets by the Hoe Stream and in Maybury.
• Is there a safer site? Because CS9 accepts Flood Zone 2 only where nothing lower is available, the sequential and exception test is usually the first report on Hoe Stream and Wey land.
• Where the rain goes. Our drainage strategy work for Woking begins with the county's rainwater reuse rule and the 1 in 2 year rate.
• Holding back runoff. A surface water drainage strategy shows storage, reuse and any soakaway against the Surrey tests, and the capacity of the ditch or sewer it drains to.
• Once permission is granted. The discharge of drainage conditions assembles the test results, calculations and maintenance plan the county's standard condition lists.
• Levels where the maps stop. The Hoe Stream model dates from 2014 and the Rive Ditch was still being studied after the 2016 floods, so flood modelling can set current design levels for a site beside either.
• Warnings with a plan. In the Hoe Stream, defended-area and Old Woking warning areas, a flood warning and evacuation plan ties a building to the warning and a dry route out.
• Gravels and the canal. On the Old Woking and Westfield gravels and the canal-side patches the SFRA flags, a groundwater flood risk assessment sets the level that basements and soakaways must clear.
• After a flood. For a Maybury home flooded twice in 2016, an insurance flood risk assessment gives the insurer evidence on the building rather than the postcode.

Who to call about the Hoe Stream, the Rive Ditch and the sewers

If floodwater puts anyone at risk, ring 999; for a power cut, 105. Otherwise, in Woking the right body depends on where the water comes from:

Who looks after which watercourse is explained in our guide to main rivers and ordinary watercourses. Close by, see our pages for Guildford up the Wey, Weybridge, which also covers the river at Byfleet, Addlestone to the north and Staines on the Thames, or the full list of areas we cover.

Questions from Woking owners and applicants

Whether it is a house by the Hoe Stream in Mayford, flats near the canal or a purchase in Maybury, call 01293 214444 or email enquiries@unda.co.uk. The chartered consultants at Unda Consulting Limited will tell you what the site needs, and a senior consultant reviews and signs off every report before it is issued.