Flood Risk Assessment in Esher

A flood risk assessment in Esher deals with a town divided by height. Most of it stands on a sandy ridge 35 to 50 metres above sea level, while the River Mole runs along its western edge behind the banks of the Lower Mole Flood Alleviation Scheme and the River Rythe runs down its eastern side past Claygate. We prepare flood risk assessments in Esher for planning applications to Elmbridge, for buyers and lenders and for insurers, together with sequential and exception tests and surface water drainage strategies, all drawn from the same local evidence.

Here, Esher means the built-up area mapped by the Office for National Statistics: the town centre and Esher Place, the Claremont Park estates, most of West End, Lower Green around the station, and the Esher end of Weston Green, all within the KT10 postcode district. Claygate, across the Rythe, has no page of its own and is covered here as well. Elmbridge Borough Council decides planning applications, Surrey County Council is the Lead Local Flood Authority, and the county-wide picture is on our page for flood risk assessment in Surrey.

Four fifths of Elmbridge's Esher settlement area lies in Flood Zone 1, yet the Mole gauge at Esher logged the biggest flow in its record on 23 and 24 December 2013, and the fields beside the river west of West End are functional floodplain.

For a first view on a particular KT10 address, ring 01293 214444 or email enquiries@unda.co.uk and one of our consultants will look at it.

Where the flood risk sits in Esher: the Mole, the Rythe and the ridge between

Elmbridge's Level 1 Strategic Flood Risk Assessment, prepared by AECOM and updated in June 2024, draws an Esher settlement area of 9.3 km² that runs south over Esher Common and Claremont, so it is larger than our map. Of that area, 80% is in Flood Zone 1, 13% in Zone 2, 2% in Zone 3 and 5% in Zone 3b. The town centre sits high; the risk gathers at the edges, where the ground drops west to the Mole floodplain at 10 to 15 metres above sea level.

Esher railway bridge is where the Environment Agency's Middle Mole and Lower Mole studies meet. Above it the river is the Middle Mole, draining about 270 km² back past Dorking and Leatherhead; below it is the Lower Mole, an 11 km² reach that was rebuilt as a flood channel and meets the Thames opposite Hampton Court. A plot by the river in West End can therefore need levels from the Middle Mole model while Lower Green, a short walk away, sits beside the defended reach. Our River Mole page follows the whole river, and the Hogsmill River page covers the river that the ditches in Claygate's north-east corner eventually drain to.

Checking a KT10 address on the map

Type a postcode into the map below to see the Environment Agency's river, surface water and reservoir data for it, or use our full flood risk map for any address in England. In coral, the map traces the ONS built-up area of Esher. It stops at the edge of Esher Common in the south and takes in Lower Green and the station in the north, so Claygate and most of the Mole floodplain lie just outside it.

Behind the Lower Mole banks: why a defended site in Esher still needs assessing

After the September 1968 flood the river below Esher was rebuilt. The SFRA says the Lower Mole Flood Alleviation Scheme was built between 1977 and 1991, and the Environment Agency describes a scheme about 7.5 km long, from the Hersham and West End area to the Thames. Its earth embankments and concrete walls begin at West End in Esher. Since the scheme was finished in 1991, the SFRA records no flood on the Lower Mole or the River Ember that has left the channel.

• Zone 3 on the map, defended on the ground. The Flood Map for Planning shows a reduction in river flood risk thanks to the defences in parts of Esher and Hersham, but flood zones are drawn as if the defences were absent, so land behind them stays in Zone 3.
• A standard, not a promise. The SFRA puts the scheme's standard of protection above the 1 in 100 year flood. An assessment still has to show what happens if a bigger flood, a breach or a structure failure lets water through.
• Run hard in 2013/14. The Agency operated the scheme on 24 and 25 December 2013 and through January and February 2014. The high flows eroded its banks, which the Agency has since repaired.
• A scheme at the end of its design life. The Agency consulted on refurbishing it from 15 August to 6 November 2024, with options from minimum repairs to rock ramps in place of sluice gates, and aimed to choose an option in spring 2025. Every option has to keep a 1 in 100 year standard with climate change over a 100-year appraisal period.

So for a site in Lower Green, or by the river at West End, a flood risk assessment in Esher sets out two pictures: the defended case, where the banks hold, and the undefended case on which the flood zone rests. Our article on why a site can still be in a flood zone after defences are built explains that gap, and our guide to residual flood risk covers how the risk left over is dealt with. The Agency's 2024 consultation sets out each option in full.

When did Esher last flood? From 1968 to the record flow of December 2013

Esher's flood history is mostly the Mole's. The dates below come from Elmbridge's SFRA, Surrey County Council's Section 19 report on the winter of 2013/14, published on 28 October 2015, the Environment Agency, and getSURREY's account of 1968.

1. March 1947. Heavy rain on the snow of a bitter winter: the first of the severe Mole floods the SFRA lists.
2. 14 and 15 September 1968. Torrential rain on soil already soaked by the wettest September on record sent the Mole and the Ember into Esher. The SFRA calls it the worst flood ever recorded in the area and puts it at about a 1 in 200 year event here. Esher's urban district council later concluded that 8,000 of the 20,000 buildings in its district had been flooded, and Army amphibious vehicles joined the relief effort.
3. 1977 to 1991. The Lower Mole scheme is built, with its banks and walls running from West End in Esher to the Thames.
4. December 1994. An overnight deluge produces the second-largest flow then recorded at the Esher gauging station.
5. Autumn 2000. The Mole at Esher reaches 115 m³/s, its highest flow since 1968, and large areas of rural land in Elmbridge flood.
6. 23 and 24 December 2013. The Mole peaks at 148 m³/s at Esher, the largest flow in the gauge's 16-year record. Surrey's report put that flow at about 1 in 150 years and the flood overall at about 1 in 50 years at Esher; no property in the Esher and East Molesey sub-area was reported flooded from the Mole that December.
7. January and February 2014. Agency flood ambassadors and data recorders are in Esher for the January event, and Surrey closes Woodstock Lane South, which the report lists under Esher.

The Agency's page for the River Mole level at Esher still gives 24 December 2013 as the highest level recorded there, and our live river levels map shows the same gauge alongside the rest of Surrey's rivers.

Claygate and the River Rythe

Claygate, across the Rythe from Esher, is a separate settlement area in the SFRA: 4.7 km², of which 96% is Flood Zone 1. Its river risk is confined to a strip of Green Belt along the western edge near Milbourne Lodge school and the low ground of the Rythe, where the 1 in 30 year outline reaches the built-up part of Station Road. The Rythe rises in Prince's Coverts near Oxshott, and Barwell Court Lake to the east appears in the Agency's reservoir mapping; if it released its water, the flood would follow the Rythe's floodplain through Claygate.

Surface water makes up the rest of Claygate's record. Surrey lists Woodstock Lane as a wetspot where works have been carried out and are waiting for a heavy storm to prove them, and its 2015 report judged the 2013/14 flooding on Woodstock Road more likely to be road drainage or surface water than river water. For a plot close to the Rythe, the SFRA asks applicants to obtain the Agency's latest model results, because the published flood zones are not fine enough to set floor levels. Esher has no designated rest centre of its own; in a flood the council would look to the Claygate Centre on Elm Road or the centre in Hersham.

Policy CS26 and Elmbridge's householder guide: the rules for a flood risk assessment in Esher

Planning applications in Esher are still decided against Elmbridge's Core Strategy of July 2011. The Local Plan 2037 was withdrawn on 26 February 2025, and although the council has started work on a new Local Plan, nothing in it carries weight yet. Elmbridge becomes part of East Surrey Council on 1 April 2027, when the new council takes over planning and the Lead Local Flood Authority role; our article on local government reorganisation explains what changes for applicants.

Elmbridge's householder guide sets six steps. For an extension in Zone 2, or on a plot with medium or high surface water risk, it asks for the flood sources including climate change, the effect of the extension on floodwater, mitigation, floor levels no lower than the existing house, a personal flood plan with a map of the escape route, and SuDS for the extra runoff. It says the Environment Agency's standing advice table is not detailed enough for the borough, and that a thin assessment may be refused with no chance to add information once the application is being decided.

Drainage is easier on the ridge than by the river. The SFRA finds the northern and western parts of the Esher area very constrained for infiltration, sees room for bespoke infiltration in the east, and expects the rest to suit soakaways well; Surrey wants test results with the application. Our ground conditions and soakaway map gives a first read on the geology under a plot, and our article on whether you need infiltration testing explains when the county will ask for it.

Extensions, rebuilds and basements: what needs a flood risk assessment in Esher?

Most Esher applications are extensions, replacement houses and conversions on large residential plots, with fewer schemes in the High Street and on the Green Belt edges. The plot's flood zone and its surface water mapping decide the detail, and the table gives the usual starting point.

At Sandown Park, flooding was argued at a public inquiry without deciding the outcome. The Jockey Club's plan for up to 318 homes and a 150-bedroom hotel at Sandown Park drew residents' concerns about flooding at Lower Green Road, where part of one site was crossed by a watercourse and lay in Zone 2. The inspector accepted that a drainage condition could manage the risk, yet the Secretary of State dismissed the appeal on 12 May 2021 on other grounds, among them Green Belt policy.

Works in or next to the Rythe's side ditches need Surrey's ordinary watercourse consent as well as planning permission. For houses, our guides to extending a house in a flood zone and rebuilding a house in a flood zone set out what each route involves.

Reports we prepare for sites from West End to Weston Green

Our Esher clients are homeowners extending or rebuilding, buyers and their lenders, developers and landlords. Each report below answers its own question, and an application near the Mole may need several of them.

• One plot, every source. A flood risk assessment in Esher deals with the Mole, the Rythe, surface water, groundwater, sewers and the reservoir extent together.
• Applications to Elmbridge. A flood risk assessment for planning is written to Policy CS26, the householder guide and the SFRA's Esher profile.
• Before exchange. Lower Green and West End sit beside the defended Mole, so a flood risk survey for property purchase tells a buyer what the banks cover and what they leave.
• Rebuilding on a large plot. A replacement house in Zone 2 or 3 counts as a new home, which brings a sequential and exception test report into the application.
• Rainwater first. Surrey always expects rainwater to be collected and reused, and the north and west of Esher are poor ground for soakaways, so a drainage strategy starts from both facts.
• Holding runoff back. A surface water drainage strategy shows discharge kept to Surrey's 1 in 2 year rate, and to greenfield rates in Zones 2 and 3.
• After permission. Where Elmbridge attaches pre-commencement drainage conditions, our discharge of drainage conditions service prepares what is needed to clear them.
• Defended and undefended levels. Where the national maps cannot show what happens behind the Lower Mole banks or beside the Rythe, flood modelling sets the design level for the plot.
• Three warning areas. Owners covered by the Mole warning areas for Esher and for Cobham and South Hersham, or by the Rythe warning area, can set out their response in a flood warning and evacuation plan.
• Below ground. Around Lower Green in the north of Esher and along the West End fringe, the SFRA finds groundwater potential at and below the surface, which a groundwater flood risk assessment tests before a basement is planned.
• Cover beside the river. For houses in Lower Green and West End behind the scheme's banks, a flood risk assessment for insurance sets out the defended risk at that address.

Reporting flooding in Esher and Claygate

Ring 999 if floodwater puts anyone in danger, and 105 for a power cut. After that, who to call depends on where the water came from.

Downstream, our pages on Molesey, Thames Ditton and Walton-on-Thames cover the Lower Mole, the mouth of the Rythe and the Thames. Upstream, Cobham and Oxshott cover the Middle Mole and the head of the Rythe, and our list of areas we cover shows the rest.

Esher flood questions from owners, buyers and applicants

Each Esher report is signed off by a senior consultant before it is issued. Our flood risk consultants hold chartered status, and the firm, Unda Consulting Limited, is a CIWEM Business Partner. Call 01293 214444 or email enquiries@unda.co.uk with the address.