Flood Risk Assessment in Worthing

Unda prepares clear, technically robust flood risk assessments and drainage strategies for residential and commercial sites across Worthing. A flood risk assessment in Worthing shows the local planning authority, and the Environment Agency where it is involved, that a development will stay safe from flooding for its whole lifetime and will not push flood risk onto anyone else. We know how a town built on a flat, tide-locked coastal plain behaves in heavy rain, and how Worthing Borough Council and West Sussex County Council expect that risk to be evidenced.

Worthing sits between the English Channel and the chalk of the South Downs, and its flooding reflects that setting. The seafront is defended but exposed to tidal and wave overtopping risk; the built-up coastal plain behind it drains slowly to the sea through the Teville Stream and a network of culverts that lock against the tide twice a day; and groundwater rises through the chalk on the northern edge of the town. We assess every source that matters on a given site, then deal directly with the Environment Agency and West Sussex County Council as Lead Local Flood Authority on your behalf. We prepare flood risk assessments in Worthing for planning, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS) — guiding developers, planning consultants, architects, landowners, home buyers and businesses through to a decision.

A flood risk assessment, a sequential or exception test and a drainage strategy are three different reports. They often travel together in a planning submission, but they answer different questions: is the site safe, should the development be here, and where does the surface water go. If you need a quote or want to talk a site through, contact one of our experienced flood risk consultants on 01293 214444.

Surface water is the defining flood risk in Worthing: the coastal plain is flat, drains to the sea by gravity and locks against the tide twice a day, so sustained rain has nowhere to go and finds the lowest ground — which is why a site can sit in Flood Zone 1 and still need a careful assessment.

Flood risk assessment in Worthing at a glance

• Surface water is the main risk. The Environment Agency identifies Worthing as one of England's surface-water Flood Risk Areas, and the Adur & Worthing strategic evidence puts the order of 10,400 properties at risk of surface-water flooding in an extreme rainfall event.
• A tide-locked coastal plain. The drainage network behind the seafront outfalls to the sea and is generally flat and locked against the tide twice a day, so any sustained rainfall ponds at the lowest point.
• A defended, exposed coast. Worthing sits behind sea defences, with tidal and wave-overtopping risk along the seafront that a low-lying frontage scheme has to address.
• Chalk groundwater on the doorstep. The South Downs chalk aquifer rises behind the town and can flood low ground and basements without ever showing on a river map.
• Flood Zone 1 is not a free pass. Since the 2025 Planning Practice Guidance update, mapped surface water or groundwater risk can trigger an assessment and a sequential test even on a Flood Zone 1 site.

Check the flood risk anywhere in Worthing

Worthing is outlined in coral below. Screen any postcode in the borough against Environment Agency data for rivers and sea, surface water, reservoirs and the planning flood zones, with a climate outlook to 2125. It is an indicative first pass and a useful starting point — not a substitute for a site-specific flood risk assessment.

Flood risk in Worthing: surface water, the coast and chalk groundwater

No single map describes flood risk in Worthing. The dominant source is surface water, because the coastal plain is flat, drains to the sea by gravity and locks against the tide twice a day. Tidal and wave overtopping threaten the defended seafront, and chalk groundwater rises on the northern edge of the town. A credible flood risk assessment in Worthing identifies which of these actually drives the risk on your site, because the mitigation for each is different.

Worthing has very little open river. Its main watercourse is the Teville Stream, an ordinary watercourse largely culverted through the centre of town near the railway and the Teville Gate site, which drains the low ground towards the sea. With the outfalls tide-locked, the practical risk is surface water ponding where the land is lowest — a pattern that has nothing to do with a named river. On the seafront, the defences hold back a normal tide but a low-lying frontage still has to address tidal and wave-overtopping risk and sea-level rise over the development's lifetime. Inland, the chalk of the South Downs produces groundwater flooding that can defeat soakaway drainage and flood basements without showing on any river map.

• Surface water dominates. Worthing is one of the Environment Agency's identified surface-water Flood Risk Areas, and surface water is now the most widespread source of flood risk in England.
• The tide does half the work. Because the network discharges to the sea and locks twice a day, drainage design has to cope with periods when nothing can leave the site by gravity.
• Flood Zone 1 still carries risk. Flood zones map only rivers and the sea, so a Worthing site can sit in Flood Zone 1 and still face real surface-water or groundwater risk — see critical drainage areas.
• Climate change widens the map. The May 2026 Flood Map for Planning update added surface-water climate-change extents that pull some previously unflagged sites into a mapped risk area.

A history of flooding in Worthing

Dated events are the clearest test of whether risk has really been understood on a site. Worthing's flood record is a surface-water record: intense rain on a flat, tide-locked plain, overwhelming the drainage network rather than any single river. These are the events the Environment Agency and West Sussex County Council have in mind when they read a new application here.

• June 2012 — the defining event. On 10–12 June 2012 a storm of around a 1-in-200-year severity hit the coast between Worthing and the Hampshire border. The drainage network was overwhelmed, Worthing Hospital flooded and seafront basement flats further west went under, in an event that drew national attention.
• The policy response. The 2012 floods prompted West Sussex County Council to produce its first Local Flood Risk Management Strategy, and surface water has been the county's stated priority ever since.
• December 2019 — a wet winter. Almost 50mm of rain fell in 36 hours at the Clapham gauge near Worthing during the 2019/20 storms, with repeated flooding across the area that winter.
• 2007 — the wider Sussex picture. Torrential summer rain across Sussex in 2007, with around 48mm in a very short period in places, is part of the same surface-water story that drives scrutiny of drainage here today.

The pattern is consistent: in Worthing it is rain, not a river, that floods homes — and ground that ponded once tends to pond again. A robust assessment treats that recorded history as evidence, not background.

Planning and drainage policy in Worthing

Two authorities set the rules. West Sussex County Council is the Lead Local Flood Authority for surface water, groundwater and ordinary watercourses, and the statutory consultee on drainage for major development. Planning decisions are made by Worthing Borough Council, part of Adur & Worthing Councils, against the adopted Worthing Local Plan — with the South Downs National Park Authority determining any site within the park.

West Sussex County Council reviews surface water drainage on major applications across the borough, and an unresolved drainage objection can hold up a decision for months. Its Local Flood Risk Management Strategy takes a catchment-based, source-to-sea approach and identifies the county's priority surface-water areas, while the Adur & Worthing Strategic Flood Risk Assessment is the local evidence base a reviewer reaches for first — including for surface-water and groundwater risk on Flood Zone 1 sites.

Your assessment and drainage strategy must satisfy national policy — the NPPF and its Planning Practice Guidance — and the local framework: the West Sussex Local Flood Risk Management Strategy, the Worthing Local Plan 2023 and the Adur & Worthing Strategic Flood Risk Assessment. Where a higher-risk site is involved, the sequential and exception tests apply. On drainage, infiltration is often defeated by the clay and high water tables of the coastal plain, so infiltration testing and, frequently, a tanked or restricted-discharge design are expected — the same higher bar neighbouring authorities such as Arun have already set in their checklists.

Why sites in Worthing need a flood risk assessment

Development in Worthing tends to fall into a few recognisable patterns, and each raises its own flood risk and drainage questions. Knowing which one applies to your site is the quickest route to a proportionate assessment and a smooth application.

• Town-centre brownfield regeneration. Sites such as the Teville Gate regeneration and the wider town centre sit on low, tide-locked ground near the Teville Stream, where surface-water drainage and exceedance routing shape the scheme.
• Seafront and coastal infill. Constrained plots along the frontage often screen as Flood Zone 1 for rivers yet carry tidal, wave-overtopping or safe-access constraints that a sequential and exception test has to address.
• Prior-approval conversions. Changing offices or commercial buildings to homes raises the vulnerability of the use, so even a low-lying Flood Zone 1 building can need raised floor levels and a safe escape route to be approved.
• Downs-fringe and groundwater sites. On the northern edge of the town the binding constraint is often a winter chalk groundwater level that defeats infiltration drainage — which is why groundwater monitoring has to be planned early.
• Property purchase and insurance. A surface-water flag on a Worthing address can affect a sale, a mortgage and house prices, and a conveyancing search is not the same as a site-specific assessment.

Climate change is not optional here. An assessment in Worthing applies the Environment Agency's allowances for heavier rainfall and sea-level rise over the development's lifetime — generally 100 years for housing — which sets floor levels, freeboard and how much attenuation a drainage scheme needs.

How Unda helps with flood risk in Worthing

Unda are experts on Worthing flooding and planning, not a local presence to drop in — we are the accurate translation layer between your scheme and the West Sussex County Council, Environment Agency and NPPF requirements it has to satisfy. A Senior Flood Risk Consultant oversees and signs off every report, and we stay involved past the report to answer consultee objections and keep the application moving.

A flood risk assessment in Worthing from Unda assesses every credible source — surface water on the tide-locked plain, tidal and wave overtopping on the frontage, chalk groundwater on the northern edge, the Teville Stream and the sewer network — compares modelled flood levels against your proposed floor levels, sets safe access and egress, and recommends mitigation the regulators will accept. Where the council needs it, a surface-water drainage strategy sits alongside the assessment as a separate report so the two cases stay consistent and an objection has nowhere to land.

We have resolved similar constraints on the coastal plain — from surface-water-affected residential infill to a property purchase where careful interpretation of surface-water mapping let the buyer secure insurance on normal terms. Worthing is a town in West Sussex, and our consultants know the county's flooding and planning well.

Flood risk assessments for every situation in Worthing

Whatever the reason you need flood risk or drainage advice in Worthing, Unda covers it. A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports that answer different questions, and we will tell you honestly which ones your situation calls for.

Flood risk assessments

• Flood risk assessment for planning. The core report for a planning application, demonstrating a site is safe for its lifetime and does not increase risk elsewhere. Groundwater is assessed within it as a source, and flood modelling is brought in where mapping is not enough.
• Flood risk survey for property purchase. A property-specific survey for buyers and their advisers when a conveyancing search flags surface-water or coastal risk.
• Flood risk assessment for insurance. Property-level evidence for brokers and underwriters where cover or premiums are in question.
• Flood risk assessment for BREEAM. An assessment structured around BREEAM Pol 03 for project teams pursuing certification.
• Groundwater flood risk. A defensible winter design water table for chalk-fringe sites and basements — assessed as a source within the assessment, or as a standalone hydrogeological assessment on complex sites.

Sequential and exception tests

The sequential and exception tests are a separate, locational report about whether a development should be in a higher-risk location at all. The sequential test defines an area of search, identifies reasonably available lower-risk sites and justifies the proposed site; the exception test is the second gate where development still needs to proceed.

Drainage strategy and SuDS

• Sustainable drainage strategy (SuDS). Surface-water engineering — calculates existing versus proposed runoff and proposes SuDS to hold discharge within the limits West Sussex County Council expects on a tide-locked site.
• Preliminary drainage design. The early, outline read that flags infiltration issues before they affect layout and land value.
• Discharge of drainage conditions. The detailed stage to discharge a pre-commencement or pre-occupation drainage condition.

You can get an early read on a site for free using Unda's Flood Risk Map, the Live River Levels Map for the nearest gauges, the geology and ground conditions checker, the BRE 365 infiltration rate calculator and the drainage calculators — then talk to our flood risk consultants when you need a report.

Flood risk management and emergency contacts in Worthing

If you need to report flooding, prepare for it, or understand who is responsible for what in Worthing, these are the bodies that matter. In a flood that threatens life, always call 999; for a power cut during flooding, call 105.

• Check for flooding in Worthing. Environment Agency live warnings, river and sea levels at check-for-flooding.service.gov.uk; sign up for flood warnings or call Floodline on 0345 988 1188.
• West Sussex County Council (LLFA). Report surface water, groundwater and ordinary watercourse flooding, and read the developer drainage guidance, via the West Sussex flood risk management pages.
• Adur & Worthing Councils. Local flood preparation, riparian responsibilities and coastal protection at adur-worthing.gov.uk.
• Live levels nearby. See whether the nearest gauges are running high right now on our live river levels map.

For flooding from blocked or burst sewers, contact Southern Water. For broader context, our notes on the Environment Agency's planning role and on residual flood risk behind a defended coast are a good starting point.

Flood risk assessment in Worthing: common questions