Flood Risk Assessment in Sheerness

A flood risk assessment in Sheerness starts with the sea. The town sits on the north-west tip of the Isle of Sheppey, where the Medway meets the Thames Estuary, and nearly nine-tenths of its built-up area lies in Flood Zone 3 behind walls, embankments and flood gates. Our consultants prepare flood risk assessments for planning applications, house purchases and insurers in the town, as well as sequential and exception tests and surface water drainage strategies. Reports for sites in Sheerness come from Unda Consulting Limited, a CIWEM Business Partner.

By Sheerness, Kent, we mean the town as the Office for National Statistics draws its built-up area: Blue Town with the former Royal Dockyard and the Port of Sheerness, which many still call Sheerness Docks; Mile Town around the High Street and Sheerness-on-Sea station; Marine Town along the seafront; and West Minster to the south. All of it falls in the ME12 postcode district. Halfway, Minster, Queenborough and Rushenden lie outside the outline and are covered on our page for the Isle of Sheppey. The Swale is the tidal channel that separates the island from the Kent mainland, and it meets the Medway beside Queenborough, a few kilometres south of the town.

If the defences between Sheerness, Minster and Rushenden were not maintained, the Environment Agency's appraisal puts 6,226 homes and 944 commercial properties inside the area a 1-in-200 tide would flood today.

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

Does Sheerness flood, and where does the water come from?

It has, and it could again. Before the present defences were finished in 1983 the town flooded on the tide, most notably in 1953 and 1978. A planning application now has to show what would happen if the sea wall were overtopped or breached, and where rain falling on clay ground and into combined sewers would go.

Flood Zone 3 is drawn as if the defences were not there, which is how a house that has never flooded ends up inside it. Our explainer on why a property stays in a flood zone after defences are built sets out what the defended picture changes, and what it leaves alone. For the way tides and surges behave, see our guide to tidal flooding and planning.

The sea wall, the port and the plan to raise them

Sheerness is benefit area 11 in the Environment Agency's Medway Estuary and Swale Flood and Coastal Risk Management Strategy, which Defra approved in 2019. The agency's BA11 consultation document describes walls and embankments with sheet-piled sections around the port, a lowest standard of protection of 5% a year (about 1 in 20) and an average remaining life of 20 years. Policy for the town frontage is to hold the line in every period up to 2118.

Those totals cover the whole unit, which runs past the town to Minster and round to Rushenden, so they count Halfway, Minster, Queenborough and Rushenden as well as Sheerness. The strategy's 10-year programme lists a Sheerness and Queenborough scheme among its first projects. On the beach, shingle was recycled from Garrison Point and from east of Neptune Jetty during the winter of 2017 to 2018, the first phase of works meant to improve protection for around 5,500 homes.

Kent County Council's 2017 profile of flood risk in Swale describes the defences as a shingle beach held by timber groynes, a rock revetment and a sea wall, built to a 1-in-200-year standard, and records that they kept the December 2013 surge out of the town. The gap between that figure and the strategy's 1-in-20 low point is the reason an assessment behind the wall turns on residual risk from overtopping or a breach, not on the flood zone alone.

The Thames Estuary 2100 Plan draws its seaward edge between Shoeburyness and Sheerness, yet none of its 23 policy units is in Swale; on the Kent shore they stop at the Isle of Grain. So the TE2100 policies that shape riverside sites upstream do not govern this town, and the Thames Barrier upstream in London plays no part in its defence. For a site here, the defence evidence comes from the Medway Estuary and Swale strategy instead.

The national tide gauge at Sheerness

The Environment Agency's sea level gauge at Sheerness is one of the 43 gauges in the UK National Tide Gauge Network, with records held from 1952 and an unbroken run since 1980. The National Tidal and Sea Level Facility notes that it is used in protecting London from tidal surges. Its highest recorded level is 4.10 m. Our live river levels map shows it beside the other gauges around the estuary.

Check a postcode in Blue Town, Mile Town or Marine Town

Type a Sheerness postcode into the tool below for an indicative screening, or open our full flood risk map for anywhere else in England. The coral line is the ONS built-up area: it takes in the port, Blue Town, Mile Town, Marine Town and West Minster, and stops short of Halfway, Minster, Queenborough and Barton's Point Coastal Park.

Surges that reached the town: 1953, 1978 and after

The record that matters for planning here is tidal. Rainfall floods are more frequent across Swale, but the two surges below reached into the town itself, and the works that followed shape what a new building has to prove.

1. 31 January to 1 February 1953. The North Sea surge overtopped the defences at Sheerness and flooded the Royal Naval dockyard and the town centre. Swale's SFRA records extensive flooding in the town that night, and our account of the 1953 North Sea flood covers the wider disaster.
2. 11 to 12 January 1978. A second surge caused serious disruption in Sheerness, and flooding and snow cut the Isle of Sheppey off from the mainland. In Kent it was put at roughly a 1-in-20-year event.
3. 1983. The present defences were completed. Kent County Council's profile dates the town's tidal floods, 1953 and 1978, to before this.
4. December 2013. The upgraded defences held through the surge that flooded properties along Faversham Creek.
5. Winter 2017 to 2018. Shingle was recycled along the beach between Garrison Point and Sheerness Sailing Club near Barton's Point.

Rain on London Clay: surface water and sewers

Sheerness is built on London Clay, which Kent County Council notes can leave ground waterlogged and surface water standing after heavy or prolonged rain. Swale's July 2026 SFRA maps large areas of surface water risk across the town, mostly following roads such as New Road, Brielle Way and St George's Avenue, with ponding around The Fleet and on low ground towards the coast in the north-west.

High tides make it harder. The SFRA warns that tide locking stops surface water leaving gravity outfalls along the defended coastal plain, and Swale's surface water management plan finds that the low-lying land of the island limits drainage. The public sewers are mostly combined, so in a heavy storm rainwater and foul flows compete for the same pipes.

Kent County Council's Drainage and Planning Policy, adopted in November 2019 and due to be replaced, sets these rules for new development:

• Greenfield land. Peak runoff held to the greenfield rate for every storm from 1 in 1 year to 1 in 100 years.
• Previously developed land. Runoff as close to greenfield as practicable and never above the existing rate, with a 50% reduction expected unless it is shown to be impracticable.
• On-site performance. No flooding anywhere on the site up to a 1-in-30-year storm, and none inside buildings up to 1 in 100 years plus climate change.
• Storage. Attenuation must half-empty within 24 hours so that the next storm has room.

Clay drains slowly, so most schemes here depend on storage and a controlled outfall. Our ground conditions and soakaway checker and BRE 365 infiltration rate calculator give a quick first read before any trial pit, and our drainage calculators help with early sizing.

What Swale's plans ask of a flood risk assessment in Sheerness

Swale Borough Council decides applications against its adopted Local Plan, Bearing Fruits 2031, adopted on 26 July 2017, and national policy, now chapter 18 of the August 2026 NPPF. Its policy DM 21 asks for a site-specific flood risk assessment to the Environment Agency's satisfaction, SuDS where possible, drainage strategies for major schemes to the satisfaction of Kent County Council, and a flood warning and emergency plan in areas at risk of flooding.

A replacement plan for 2027 to 2042 is well advanced. Its Regulation 19 Publication Draft was consulted on from 10 August to 21 September 2026 and goes next to submission, with an examination expected in 2027. These are the policies a Sheerness scheme will meet:

For the sequential test, Swale's July 2026 advice note lets an application in the town search only the built-up area of Sheerness, Queenborough and Rushenden taken together, rather than the whole borough; the note adds that the Environment Agency's strategy holds the line around these settlements. If the red line runs outside the built-up area, the search reverts to the whole of Swale. That makes testing alternative sites a far smaller job than a borough-wide search would be.

The council's Level 1 SFRA (version 5, July 2026) sets floor levels at least 600 mm above whichever is higher of the average ground level, the adjacent road and the estimated flood level, reduced to 300 mm only where that level is known with confidence. It rules out habitable basements in Flood Zone 3 and keeps a 16 m strip clear from tidal main rivers, measured from the landward toe of any defence. Our summary of what the August 2026 NPPF changed covers the national side.

Matching the report to a Sheerness site

Which report a site needs comes down to the proposal and to who will read the result: the council, a lender, an insurer or a buyer. Our consultants prepare each of these for sites across the town:

• New homes and conversions. Nearly anything in Flood Zone 3 here, from a flat conversion in Mile Town to the West Minster allocations, needs a flood risk assessment for planning.
• Tide, rain and sewers together. A flood risk assessment in the town has to weigh overtopping, a breach, ponding on the clay and surcharged sewers on the same plot.
• Buying a house. Terraces in Marine Town and Blue Town can carry a tidal flag in the searches, which a flood risk survey for property purchase checks against the actual house before exchange.
• Testing the location. New homes in Flood Zone 3 face the sequential and exception test, searched across the Sheerness, Queenborough and Rushenden built-up area.
• Runoff from new building. Kent County Council expects a 50% cut in runoff from previously developed land, and our drainage strategy work shows how a site achieves it.
• Water on clay. Where the ground will not take water and outfalls lock at high tide, a surface water drainage strategy finds the storage and a controlled route out.
• After consent. Where Swale grants permission subject to a drainage condition, we prepare the evidence for the discharge of drainage conditions.
• Evacuation and refuge. The town sits in warning area 064FWC1Sheerness, and policies DM 21 and C8 ask for a flood warning and evacuation plan in flood risk areas.
• Insurance cover. After the floods of 1953 and 1978, and with 87% of the town in Flood Zone 3, a flood risk assessment for insurance gives an underwriter evidence about the building itself.
• Land deals near the port. The Environment Agency lists historic landfills at Lappel Bank, Sheerness Canal and Westminster Works behind the frontage, so flood risk due diligence belongs before a purchase.
• Keeping a business running. The port and New Road Industrial Estate are named among the assets behind the BA11 defences, and a business continuity flood assessment helps occupiers plan for a surge.
• Breach and overtopping. The SFRA treats wave overtopping as a main flood mechanism along the Sheerness seafront and the rest of this coast, and our flood modelling produces depths and hazards on a site if the wall fails or is overtopped.
• Sewer capacity. With 25 sewer flooding incidents logged in ME12 2 since 2015, a foul drainage strategy should confirm Southern Water's capacity early.
• Port and employment schemes. The adopted plan treats the Port of Sheerness as a regeneration area and strategic employment site, where a BREEAM flood risk assessment supports the Pol 03 credit.
• Before buying land. For sites like the Brielle Way and New Road allocations, a feasibility study tests what the flood constraints leave for layout and numbers.
• Which Framework applies. Swale's draft policies were written against the December 2024 Framework, and our NPPF guidance explains what the August 2026 version changes for a Sheerness scheme.

Warnings, emergencies and the bodies involved

In a flood that puts life at risk, call 999, and for a power cut call 105. Beyond that, emergency preparedness and flood management in the town are shared between these bodies:

A second Environment Agency area, the Isle of Sheppey and coast from Kemsley to Seasalter flood alert area, gives earlier notice when the tide is expected to run high. Kent County Council's flood risk profile for Swale describes the 1983 defences and the London Clay beneath the town.

Across the estuary, Southend-on-Sea and Canvey Island face the same North Sea surges inside the TE2100 area, while Gillingham sits up the tidal Medway. Our River Medway and River Thames pages cover the two estuaries that meet off Garrison Point, and the Kent county page and our list of areas take in the rest of the county.

Questions about building and buying in Sheerness

Unda Consulting Limited works on sites throughout Swale, from the Sheerness seafront to the creeks of the mainland. For a site in Blue Town, Mile Town or Marine Town, call 01293 214444 or email enquiries@unda.co.uk.