Flood Risk Assessment in Selsey

A flood risk assessment in Selsey starts with the sea, which surrounds the town on three sides. Selsey stands at the tip of the Manhood Peninsula in Chichester district, West Sussex, behind sea walls built in the 1950s, and our check of the Environment Agency's Flood Map for Planning puts about 38% of its built-up area in Flood Zone 3. Our consultants prepare flood risk assessments in Selsey for seafront and harbour-side planning applications, house purchases, mortgages and insurance, and the sequential tests, exception tests and surface water drainage strategies that go with them. Reports for sites in Selsey come from Unda Consulting Limited, a CIWEM Business Partner.

Here, Selsey means the town's built-up area as the Office for National Statistics maps it: the High Street and the town centre, Selsey Bill at the southern point, East Beach on the eastern shore and the homes and holiday parks behind West Sands on the western side. All of it is in the PO20 postcode district, in sectors PO20 0 and PO20 9. Church Norton, the hamlet by the mouth of Pagham Harbour, lies just beyond the outline but shares the town's flood warning area. Medmerry and Bracklesham are to the north-west.

Until 2013 the shingle bank west of Selsey gave roughly a 1-in-1-year standard of protection; the Medmerry embankments that replaced it protect 348 properties and the town's only road to 1 in 100.

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

Selsey Bill, the 1950s sea wall and four kilometres of seafront

Most of the Selsey seafront is held by hard defences. Sea walls from the 1950s, timber groynes and a shingle beach topped up every year protect the town from the tide and from erosion. Before the walls went up, Selsey had one of the fastest-eroding coastlines in England, according to Coastal Partners, the shared coastal team that manages the frontage for Chichester District Council.

• A replacement in design. Coastal Partners says the walls are nearing the end of their serviceable life. An Environment Agency grant of £2.9 million is paying for an options appraisal and outline design across 4 km of seafront, the Selsey Coastal Scheme, and drop-in events at Selsey Town Hall on 15 to 17 October 2026 showed the leading options.
• Repairs in the meantime. Refurbishment of a deteriorating stretch of the West Beach sea wall was due to start at the end of August 2026, and the yearly shingle recharge began on 2 February, according to Coastal Partners' scheme updates. In June 2026 the council extended its beach management plan to March 2029, subject to Environment Agency funding.
• Hold the line, without a guarantee. The Pagham to East Head Coastal Defence Strategy holds the line at Selsey. Two shoreline plans meet at the Bill: the Beachy Head to Selsey Bill shoreline management plan holds the point itself, with managed realignment towards Pagham Harbour, and the North Solent plan takes over to the west from Selsey West Beach (2023 Level 1 SFRA). Chichester's Local Plan adds that even a hold-the-line frontage has no guarantee of future funding.
• Flood Zone 3 regardless. The planning map ignores the walls, so land behind them stays Flood Zone 3. An assessment answers the residual flood risk of the walls being overtopped by waves or breached in a storm, and where the Environment Agency's Arun to East Head tidal model sets the zones, it expects both the defended and the undefended results to be used.

Our GIS check of the Flood Map for Planning, run in October 2026, shows the risk following the lie of the land. The low ground behind West Sands on the western side and the shore from the Bill round to East Beach are Flood Zone 3; the High Street and the town centre sit on higher ground in Flood Zone 1. About 38% of the built-up area is in Flood Zone 3 and a further 5% in Flood Zone 2. Our guide to sea defences explains what walls, groynes and shingle recharge each do.

Check a postcode from West Sands to East Beach

The map outlines Selsey's built-up area in coral. Enter a postcode to see the planning flood zone, the risk from the sea and from surface water, and any warning in force; our flood risk map does the same for the rest of England. Both describe the area around a postcode rather than one building, so neither stands in for a site-specific assessment.

Medmerry: the coast west of Selsey moved inland

West of the town, the Environment Agency gave up the old shingle bank and built a new line of defence further back. The Medmerry managed realignment, between Selsey and Bracklesham, began in September 2011 and was marked complete on 4 November 2013. The figures below are from the Institution of Civil Engineers' case study of the scheme.

• The old bank. A 3 km shingle bank, reshaped by bulldozer every winter at up to £300,000 a year, gave roughly a 1-in-1-year standard. It breached regularly, most recently in 2008, when the damage passed £5 million.
• The new line. Seven kilometres of new floodbank reach almost 2 km inland behind a 110 m gap cut in the shingle. The £28 million scheme created 183 ha of intertidal habitat, now the RSPB's Medmerry reserve.
• What it protects. 348 properties, a sewage works, caravan parks and the main road into Selsey, to a 1-in-100-year standard.
• A protected site in planning. Chichester's Local Plan treats the Medmerry Compensatory Habitat as equivalent to an internationally designated site, so policy NE13 asks schemes near it to show no harm to its integrity and no coastal squeeze.
• The test behind it. A 1-in-100 standard lowers the odds of flooding, and in April 2024 a surge of about that size overtopped the defences at Medmerry West Beach. The assessment still has to show that a building stays safe if the embankment is overtopped or fails, with sea level rise added over its lifetime.

The shoreline plan's policy for this stretch, Selsey West Beach to Bracklesham, was managed realignment to 2025 and hold the line on the new embankments from then to 2105 (North Solent SMP policy unit 5A01).

Storms, surges and breaches on the Selsey shore

Selsey was cut off at high tide until 1809, when the causeway that now carries the B2145 was finished, according to the University of Sussex's CoastView history of Selsey Bill. The floods recorded since have almost all come from the sea.

1. 1950s. Sea walls and groynes went up after severe storm damage early in the decade, and they still form most of the town's defence against the sea.
2. January 1998. A tornado damaged about a quarter of the town's properties on 7 January. About a week later, storms broke through the sea defences and flooded the caravan park and some properties at East Beach.
3. January 1999. Storms breached the defences again over a weekend, and the Environment Agency brought in about 10,000 tonnes of shingle from Shoreham Harbour to repair them.
4. 2005. Coastal defences west of Selsey were overtopped, the event the county's Manhood Peninsula surface water management plan records for the town's coast.
5. 10 March 2008. A storm surge flooded at least 37 separate areas around the Solent, and a breached shingle barrier at Selsey accounted for up to 90% of the flooded land (Wadey, Nicholls and Haigh, 2013).
6. 10 to 12 June 2012. Rain of 114 mm in 24 hours at the Bognor Regis gauge affected 110 properties across the Manhood Peninsula; the flat coastal plain was tide-locked twice a day, so the rifes could not discharge (county report on the June 2012 floods).
7. 8 to 9 April 2024. In Storm Kathleen the tide and surge overtopped the Environment Agency's defences at Medmerry West Beach. Water crossed the nature reserve and flooded about 233 of the 268 chalets at Medmerry Cove Seaside Park, east of Bracklesham; the Medmerry tide gauge peaked at 3.26 m AOD, and the county's Section 19 report put the event at roughly 1 in 100. No Selsey property was recorded as flooded.
8. 2021 to 2026. Chichester District Council reported in June 2026 that the frontages it manages, which do not include the Environment Agency's Medmerry scheme, had seen no tidal flooding since 2021.
9. February 2026. After rainfall the county council described as reaching highs of 190% above average, Highleigh Road and Keynor Lane in Sidlesham, north of the town, were closed when a neighbouring rife overflowed (West Sussex County Council).

Readings from the Medmerry gauge appear with other river and sea gauges on our live river levels map. Most flooding on this coast comes from waves overtopping the defences when high winds, offshore storms, high tides and swell arrive together, according to Coastal Partners' Selsey questions and answers; it rates a breach of the sea wall as very low risk while the beach is managed.

Rain, rifes and groundwater behind the sea wall

Away from the shore, the problem is water with nowhere to go. The Manhood Peninsula is low, flat and drained by ditches and rifes; high tides can lock the outfalls shut, and saturated ground has filled septic tanks and overloaded sewers, according to Chichester's 2023 Level 1 SFRA. The county's surface water plan for the peninsula ranks Selsey among its seven high-priority locations.

Policy NE15 sets the drainage rule that follows from this: because groundwater is high and the land is low, a development and its SuDS must not worsen the drainage or flood risk of neighbouring land or buildings, and open SuDS that support wildlife are encouraged. Soakaways need testing against the winter water table, and our guide to groundwater in planning applications sets out what to submit. National standards under NPPF policy F8 apply too; our note on the 2025 SuDS standards sets them out.

What Chichester's Local Plan asks of a flood risk assessment in Selsey

Chichester District Council decides planning applications in Selsey under the Chichester Local Plan 2021 to 2039, adopted on 19 August 2025, and West Sussex County Council advises on surface water as Lead Local Flood Authority. Four of the plan's policies shape the assessment, read with the Selsey Neighbourhood Plan and chapter 18 of the NPPF.

The plan names Selsey as a settlement hub but makes no strategic housing allocations on the Manhood Peninsula, and it proposes no coastal change management areas, relying on the 25 m buffer instead. So the schemes that come forward in Selsey tend to be windfall plots, replacement houses, extensions and changes on the holiday parks. The council's 2023 Strategic Flood Risk Assessment includes a method for running the sequential test against its mapping.

Nationally, chapter 18 of the August 2026 NPPF sets out when an assessment is needed (policy F4), the sequential and exception tests (F5 and F6) and the national standards for sustainable drainage (F8); our summary of the 2026 NPPF changes covers the detail. Floor levels in Selsey are worked in metres above Ordnance Datum, explained in our note on AOD and floor levels, with the Environment Agency's climate change allowances for sea level rise.

When a flood risk assessment in Selsey is needed, scheme by scheme

Whether a Selsey scheme needs an assessment depends on its flood zone, its size and what it is for. The table covers the schemes that come up most often in the town; the postcode map above gives the flood zone, and the same tests apply to a site anywhere in the parish.

Getting out during a flood is the other question that comes up on Selsey sites. The B2145 is the only road in and out of Selsey, and Medmerry was built partly to protect it. Where a site's own route out could flood, our article on dry island sites explains how an assessment deals with safe access and egress.

Reports we prepare for East Beach, the High Street and the holiday parks

People commission flood work in Selsey to build, buy, insure or run a business on a defended coast. Each report below answers a different question, and several often go in together with one application.

• Applications to Chichester District Council. New homes, replacement dwellings and changes of use in Flood Zone 2 or 3 need a flood risk assessment for planning that answers policy NE16, including its floor-level rule.
• The sea, the rain and the ground together. A flood risk assessment for a Selsey site weighs overtopping and a breach of the sea wall against surface water and a high water table, then sets floor levels and a safe way out.
• Before exchange at East Beach or behind West Sands. Lenders and buyers ask about the warning area and the flood zone, and a flood risk survey for property purchase answers them for the one building being bought.
• New homes in Flood Zone 3. Chichester starts the sequential and exception test from the method published with its 2023 SFRA, which sets out how the search for lower-risk sites is run.
• Flat ground and outfalls that lock shut at high tide. A drainage strategy for Selsey has to show where water goes when the ground is already wet and the ditches cannot discharge.
• Major schemes and any site that needs an assessment. Policy NE16 asks for SuDS on both, and a surface water drainage strategy shows that runoff will not rise and, under NE15, that neighbouring land will not get wetter.
• After permission. An application for the discharge of drainage conditions gives the council the calculations and details its pre-commencement conditions on a Selsey consent asked for.
• Residual risk behind the sea wall. NE16 requires a site-specific flood warning and evacuation plan wherever residual risk remains, and the seafront from West Street round to East Beach Road sits in the Selsey East Beach warning area.
• Cover priced on the postcode. With about two-fifths of the town in Flood Zone 3 and a flooding record at East Beach, a flood risk assessment for insurance sets out the risk to the house itself.
• Buying a holiday park or commercial land. The caravan parks on the western side of town are in Flood Zone 3 and rely on the Medmerry embankments, and flood risk due diligence puts that in front of a buyer or lender before the deal.
• Keeping a seasonal business running. Storms flooded a Selsey caravan park in January 1998 and Storm Kathleen flooded 233 chalets at Medmerry Cove in April 2024; a business continuity flood risk assessment plans the warning triggers, the response and the recovery for an operator.
• A high water table across the peninsula. Chichester's Local Plan names high groundwater on the Manhood Peninsula, and a groundwater flood risk assessment tests what that means for foundations, soakaways and any space below ground.
• Commercial and employment schemes. The neighbourhood plan allocates an employment site, and the Park Farm scheme permitted alongside it includes a supermarket, a hotel and a clinic; a BREEAM flood risk assessment covers the Pol 03 credits for buildings of that kind.

Sea wall, warnings and drains: who handles flooding in Selsey

Responsibility in Selsey is split by source. The district council, working through Coastal Partners, looks after the sea defences on its frontages; the county council handles surface water and ordinary watercourses; the Environment Agency covers the sea and issues the warnings. The table lists who to contact.

Warnings for the town come in two areas. The Selsey East Beach warning area covers coastal parts of Selsey Bill, including West Street, Clayton Road, Warner Road, Marine Gardens, Kingsway, East Beach Road, East Beach and Church Norton; the Medmerry warning area includes the West Sands caravan park. Anyone can sign up for flood warnings by phone, text or email, and the government's long-term flood risk service gives the long-term picture for an address.

Questions asked about Selsey sites, from the seafront to the High Street

Unda Consulting Limited prepares flood risk assessments, sequential and exception tests and drainage strategies for homes, holiday parks, businesses and development land across Selsey. Neighbouring pages cover Chichester, Pagham and West Sussex as a whole, and our areas index lists the rest. To discuss a Selsey site, call 01293 214444 or email enquiries@unda.co.uk.