Flood Risk Assessment in Maidstone

A flood risk assessment in Maidstone nearly always starts with the River Medway, which runs north through the town centre, past Lockmeadow, to Allington Lock, where the non-tidal river meets the tide. The Len and the Loose Stream join it inside the town. Our consultants prepare flood risk assessments in the town for planning applications, house and land purchases and insurance, together with sequential and exception tests and surface water drainage strategies.

The page takes in the town as the ONS built-up area draws it: the town centre with Fant and Tovil, Barming Heath and East Barming to the west, Allington, Ringlestone and Sandling to the north, Penenden Heath, Grove Green and Vinters Park to the east, and Shepway and Park Wood to the south, across the ME14, ME15 and ME16 postcode districts. Bearsted on the Len and Loose on its stream lie just outside the outline but inside Maidstone borough; Aylesford, downstream, is in Tonbridge and Malling.

On 26 December 2013 the Environment Agency gauge on the Medway at Maidstone reached 3.58 m, its highest level on record. The agency says property flooding becomes possible once the river passes 2.60 m there.

To go through a site in the town with one of our flood risk consultants, call 01293 214444 or email enquiries@unda.co.uk.

Is Maidstone prone to flooding?

Yes. The river that runs through Maidstone is the Medway, and Kent County Council's flood profile of the town records the centre flooding from it in November 1960, 1963, September 1968, October 2000 and over Christmas 2013. The same profile notes that the town's steep, heavily built-up streets shed rainwater fast, so surface water and overloaded drains are a second problem well away from the river.

The Medway between East Farleigh and Allington Lock

Through the town the Medway is a managed, non-tidal navigation. Allington Lock, at the northern edge of the built-up area, marks the border between the tidal and non-tidal river, so sites upstream of it face river flooding and sites below it feel the tide as well. Kent County Council records no formal flood defences in central Maidstone, and the sluice at Allington serves navigation and bank retention rather than flood defence.

The Environment Agency's River Medway at Maidstone gauge gives a working scale for the town centre:

1. 0.23 m to 0.75 m. The normal range for the river at the station.
2. Above 0.75 m. Low-lying land can flood and flood alerts may be issued.
3. Above 2.60 m. Property flooding is possible.
4. 3.58 m on 26 December 2013. The highest level the station has recorded. A day earlier the Allington Lock gauge set its own record of 4.27 m.

The town falls in three Environment Agency warning areas: the River Medway at Maidstone, which takes in Tovil, Allington and Allington Marina; the river between Yalding and Maidstone; and the tidal Medway from Allington to Cuxton. Our live river levels map shows these gauges beside every other one in the catchment, and the river as a whole is covered on our River Medway page. An assessment for a town-centre site reads those thresholds alongside the modelled flood levels, and our guide to assessing river flooding explains how the two fit together.

Floods the town remembers

• November 1960, 1963 and September 1968. Kent County Council lists all three among the river floods that reached Maidstone town centre.
• October 2000. Prolonged autumn rain filled the Medway catchment, though the county council says the effect on the town itself was limited compared with 2013.
• Christmas 2013. Maidstone market, in the Lockmeadow complex on Barker Road, was completely flooded on Christmas Day, the Lockmeadow and Fremlin Walk car parks went under, and at the worst point around 15 town-centre stores, bars and restaurants had to shut, Kent Online reported on 7 January 2014.
• Winter 2013/14 in numbers. Kent County Council's final report on the storms counted 262 flooded properties in the Maidstone council area, 207 homes and 55 businesses, out of 929 across Kent.
• Winter 2019/20. The borough's 2020 Strategic Flood Risk Assessment records significant flooding in the borough again that winter.

In December 2025 Maidstone Borough Council put the number of properties at risk of flooding in Maidstone at 5,370 and said only 1,406 of them had signed up for flood alerts. A planning officer will expect an assessment to use a dated record like this, set against every source of flood risk and not the river alone.

Screen a site in Tovil, Allington or the town centre

Enter a postcode below for a first look at the Environment Agency's flood data for a Maidstone site, or open our full flood risk map for anywhere in England. The coral line is the ONS built-up area, so Allington, Sandling and Park Wood are inside it while Bearsted, Loose and Boxley fall outside.

Why the upstream schemes stop short of the town

Most flood investment on the Medway has gone upstream, and none of the schemes names Maidstone town among the places it protects. That matters for a riverside application, because the planning flood zones leave defences out and the borough's Strategic Flood Risk Assessment finds no formal defences anywhere in the Local Plan area.

• Leigh flood storage area. The expanded storage area above Tonbridge opened in 2026; the Environment Agency says it now holds about 7.4 million cubic metres, roughly 23% more than before, protecting 1,870 homes and 575 businesses in Tonbridge and Hildenborough.
• Medway Flood Partnership. Set up in January 2017 with Maidstone Borough Council among its members, it published the Medway Flood Action Plan that December for the non-tidal Medway, Beult, Teise and Eden.
• Middle Medway flood resilience scheme. Completed in November 2020, the scheme fitted flood doors, gates and air brick covers to homes in eight parishes from Yalding to Wateringbury, none of them in the town.
• Fairmeadow. The 2020 SFRA lists defences near Fairmeadow as a possible future scheme, with no design or funding attached.

A town-centre site is therefore assessed as it stands, including the residual flood risk from a flood bigger than the upstream storage can hold. Where a scheme takes up floodplain, the volume lost has to be replaced level for level elsewhere on the site.

Ragstone, clay and the Mote Park dam

The ground under Maidstone changes from one district to the next. British Geological Survey mapping puts Weald Clay mudstone beneath the town centre and the riverside, Atherfield Clay at Tovil and along the Len by Mote Park, and the Hythe Formation, Kent's ragstone with its sandy hassock, across Allington, Barming Heath, Shepway, Park Wood, Grove Green and Vinters Park. Folkestone sandstone comes to the surface at Penenden Heath and Gault mudstone at Sandling.

That mix decides how a site drains. A soakaway that works on ragstone at Barming Heath may fail on clay in the town centre, so a soakaway has to be proved by infiltration testing on the site, not assumed from the map. The ground conditions and soakaway checker reads the mapped geology under a postcode, and the BRE 365 infiltration rate calculator turns trial-pit results into an infiltration rate.

• Groundwater. Kent County Council does not regard the area as especially prone to groundwater flooding, but it records a few incidents around Loose, where the ground is Lower Greensand, an aquifer. A site on that ground may need the groundwater evidence a planning application calls for.
• The Mote Park dam. The Len was dammed in about the 1830s to form the lake, and in 2020 Maidstone Borough Council said a failure could spread water across about 40 acres, flooding Turkey Mill and parts of the park to an estimated 12 feet. The council repaired the dam, spillway and sluices that year after the ten-yearly safety inspection. Breach mapping for a reservoir is not always released, and our article on dam breach data explains what a site below one can obtain.
• Surface water. Kent's 2012 surface water management plan for Maidstone and Malling picked out Turkey Mill as a hotspot, and the Local Plan Review asks new development to have regard to that plan. How planning weighs this source is set out in our guide to surface water flooding and planning.

Which sites need a flood risk assessment in Maidstone?

Policy LPRSP14(C) of the Local Plan Review makes a flood risk assessment in Maidstone a requirement on any site in Flood Zone 2 or 3 or over one hectare, and national policy in chapter 18 of the NPPF adds sites at risk from other sources. The table shows how that plays out across the town, using the three flood zones on the Environment Agency's map.

New homes and other more vulnerable uses in Flood Zones 2 and 3 also face the sequential test, which asks whether reasonably available land at lower risk exists before the site's own evidence is weighed.

Local Plan Review policies and Kent's drainage rules

Maidstone Borough Council adopted the Local Plan Review 2021 to 2038 on 20 March 2024, with a housing requirement of 1,157 homes a year. Its climate change policy, LPRSP14(C), asks major development to build in SuDS and blue-green infrastructure, requires flood risk assessments on the sites set out above and expects development to have regard to surface water management plans. Policy LPRSP1 asks town-centre sites beside the Len and the Medway to respond to the rivers' setting.

The evidence behind the plan is the council's Level 1 SFRA update and Level 2 SFRA, prepared by JBA Consulting in August 2020. A Strategic Flood Risk Assessment maps risk across a whole authority so that sites can be compared. For river flood risk the Maidstone SFRA asks for ground floors at least 300 mm, and sleeping accommodation at least 600 mm, above the 1% annual chance flood level with a 35% climate change allowance, subject to further tests in the SFRA that include a 70% allowance.

Kent County Council, as Lead Local Flood Authority, is consulted on the surface water drainage of every major application in the county. It reviews drainage strategies against its Drainage and Planning Policy statement, whose latest version it supplies on request through suds@kent.gov.uk, and its Local Flood Risk Management Strategy 2024 to 2034 estimates that more than 20,000 properties in Kent are at risk from surface water runoff. Where a site drains to a watercourse in the Upper Medway Internal Drainage Board's district, the board's byelaws apply as well.

Nationally, the NPPF's flood chapter (chapter 18, policies F1 to F9) sets the tests, and the August 2026 changes tied the sequential test's area of search to the development's catchment.

Matching the report to a Maidstone site

A riverside block, a hillside plot on the ragstone and a house purchase in Tovil each call for something different. Our consultants prepare each of the reports below for Maidstone sites. A flood risk assessment, a sequential test and a drainage strategy answer different questions: whether the site is safe, whether it should be there, and where the water goes. Unda is a CIWEM Business Partner, and a senior flood risk consultant signs off every report.

• Riverside and larger sites. Land in the floodplain of the Medway, the Len or the Loose, or any site over a hectare, needs a flood risk assessment for planning under policy LPRSP14(C).
• Several sources on one plot. A site in Tovil or the town centre can face the river, surface water, the sewers and the Mote Park reservoir together, and a flood risk assessment weighs them side by side.
• Buying near the Medway. A riverside home in Tovil, Allington or the centre sits below a gauge that set its record in 2013, and a flood risk survey for property purchase tells a buyer what that means for the building before exchange.
• New homes in the flood zones. Housing on Maidstone West or Maidstone Riverside meets the sequential and exception test before anyone looks at floor levels.
• Drainage for planning. Kent County Council reviews the surface water proposals on every major application, and our drainage strategy work is prepared to meet that review.
• Clay or ragstone underfoot. Whether a plot sits on Weald Clay or the Hythe Formation decides how a surface water drainage strategy disposes of runoff.
• Conditions after consent. Where the council attaches a drainage condition, we prepare the evidence for the discharge of drainage conditions.
• Levels the national maps cannot give. For a riverside scheme where national mapping is too coarse, flood modelling derives Medway levels, depths and hazards for the site itself.
• Getting people out safely. Maidstone West is nearly a third Flood Zone 3 and lies in the River Medway at Maidstone warning area, so homes there need a flood warning and evacuation plan.
• Insurance after 2013. With 262 properties flooded across the borough that winter, a flood risk assessment for insurance gives an underwriter evidence about the building itself.
• Keeping a business trading. Around 15 town-centre businesses shut during the Christmas 2013 flood, and a business continuity flood assessment helps an occupier plan for the next high river.
• Buying riverside land. Maidstone Riverside is more than half Flood Zone 2, so flood risk due diligence belongs before any land deal along the river.
• Water in the sands. The Lower Greensand, which takes in the Hythe and Folkestone beds, is an aquifer and Kent County Council records groundwater incidents near Loose; where basements or soakaways are planned, a groundwater flood risk assessment tests the risk.
• Sewer capacity. Policy LPRSP5(B) makes the 1,300 homes at Invicta Park Barracks show sewerage capacity, and a foul drainage strategy puts that question to Southern Water early on any large scheme.
• Before committing to a site. On land the size of Invicta Park Barracks, or a riverside plot near the town centre, a flood risk feasibility study shows what the flood constraints allow before money changes hands.

Who to call when the Medway or the drains overflow

If anyone's life is at risk, call 999. For a power cut, call 105. Responsibility for everything else is shared between these bodies:

The Environment Agency's Check for flooding page for Maidstone shows current warnings and the five-day flood forecast, and its Flood Map for Planning gives the official zone for a site. The split of duties between these bodies is laid out in our overview of who manages flood risk in England.

Upstream, Yalding is where the Beult and the River Teise meet the Medway; downstream, the tidal river carries on through Rochester and past Gillingham. For the wider county, see flood risk assessment in Kent and the index of areas we cover.

Questions from Maidstone buyers, builders and planners

Our consultants work on sites throughout Maidstone borough and across Kent, whatever the reason a report is needed. Call 01293 214444 or email enquiries@unda.co.uk to discuss one.