Flood Risk Assessment in Arundel

Arundel sits on a bend of the River Arun where the tide decides as much about flood risk as the weather does. The Arun stays tidal for around 40km inland of the town, so a flood risk assessment in Arundel has to weigh a rising spring tide and storm surge pushing up from the coast alongside river flow off the Weald and the South Downs. Low-lying land either side of the river, through the town centre and along River Road, sits within Flood Zones 2 and 3, while the historic core around Arundel Castle sits higher and drier.

We prepare flood risk assessments in Arundel for planning, property purchase, mortgage and insurance, and BREEAM, alongside sequential and exception tests and surface-water drainage strategies (SuDS). A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct reports, answering three different questions: is the site safe, should the development be here, and where does the surface water go once it's built.

Call 01293 214444 or email enquiries@unda.co.uk to talk to one of our experienced flood risk consultants about a site in Arundel.

In November 2023, Storm Ciarán pushed the River Arun to what local reporting described as its highest level in Arundel in living memory, proof that this stretch of river can flood on a strong tide and storm surge alone, without a drop of local rain falling.

• Dominant flood risk: tidal and fluvial flooding from the River Arun, plus surface water and chalk groundwater around the South Downs.
• Lead Local Flood Authority: West Sussex County Council, responsible for surface water, groundwater and ordinary watercourses.
• Local planning authority: Arun District Council, whose Strategic Flood Risk Assessment and Local Plan set the local policy tests.
• Flood zones: low ground beside the river, including River Road and the water meadows, sits within Flood Zones 2 and 3.
• Active flood scheme: the Environment Agency's Arundel Tidal Defence Scheme has strengthened defences on both riverbanks, aiming to protect up to 130 properties.

Flood risk assessment in Arundel: check your site

Use the tool below to check the modelled flood risk for any postcode in and around Arundel. The Arun district, Arundel's local planning authority area, is outlined in coral; search a postcode to see Environment Agency data on rivers and the sea, surface water, reservoirs and climate-change projections to 2125, plus live flood warnings for the area.

Local flood risk and hydrology in Arundel

Arundel's flood risk comes from more sources than most inland towns face: the tidal and fluvial River Arun, surface water gathering on low-lying land, and groundwater rising through the chalk of the South Downs. The wider Arun and Western Streams Catchment Flood Management Plan covers the river's catchment, and the Flood Map for Planning shows Flood Zones 2 and 3 concentrated along the river through the town and the water meadows.

The Environment Agency's Arundel Tidal Defence Scheme has strengthened flood defences on both banks of the river at River Road, Tarrant Wharf and Fitzalan Road, and the Agency forecasts river levels up to three days ahead because sea level, not rainfall, is normally the dominant factor at Arundel. The wider Lower Tidal Arun Flood Risk Management Scheme covers further work along the estuary downstream towards Littlehampton, an area we also cover in our flood risk assessment in Littlehampton.

Historical flooding in Arundel

Arundel's location on a tidally dominated river means flooding here is a recurring, well-documented risk rather than a rare event.

• December 2013: the River Arun at Queen Street Bridge reached one of its highest recorded levels, 3.65 metres, as a tidal surge combined with high river flows.
• January 2014: the Arun burst its banks and flooded properties on River Road; the Environment Agency issued over 100 flood warnings and 200 flood alerts across the South East that week.
• 2019–2020: the Environment Agency's Arundel Tidal Defence Scheme (Phase 1) strengthened defences at River Road, Tarrant Wharf and Fitzalan Road, at an estimated cost of £6.7 million, protecting up to 130 properties from flooding and a further 30 from erosion.
• November 2023: Storm Ciarán pushed the river to what local reporting described as its highest level in the town in living memory.

Planning and drainage policy for a flood risk assessment in Arundel

West Sussex County Council is the Lead Local Flood Authority for Arundel, responsible for surface water, groundwater and ordinary watercourse flood risk. Arun District Council is the local planning authority; its Strategic Flood Risk Assessment (the SFRA 2026 Level 1 Assessment, published March 2026) considers fluvial, tidal, estuarial, groundwater and surface-water sources across the district and feeds policy in the emerging Arun Local Plan 2023–2041. Because surface water flooding affects a large proportion of the district, Arun DC has also published a set of SuDS design checklists (October 2025), aligned with the CIRIA SuDS Manual and the National Standards for SuDS, which require groundwater monitoring and BRE 365 infiltration testing to support any infiltration-based drainage design.

• Lead Local Flood Authority: West Sussex County Council — surface water, groundwater and ordinary watercourses.
• Local planning authority: Arun District Council — Strategic Flood Risk Assessment (SFRA 2026) and the emerging Local Plan 2023–2041.
• SuDS design checklists: Arun DC's October 2025 checklists set out ground investigation, design, maintenance and verification requirements for surface-water drainage, referencing our own note on Arun's new drainage checklists.
• Main river authority: the Environment Agency manages the River Arun Internal Drainage District pending a stakeholder-agreed long-term arrangement.

Development in Arundel: what triggers a flood risk assessment

Development around Arundel is shaped as much by heritage as by hydrology. Much of the historic town centre beneath Arundel Castle is a conservation area, which restricts the scale and form of new building, so schemes here tend to be small, sensitive infill rather than large-scale redevelopment. Around the town's edges, low-density residential schemes, conversions of rural and agricultural buildings, and tourism and visitor-related development make up much of the remaining pipeline, reflecting Arundel's position as a major heritage destination. Any site close to the River Arun, the water meadows or the Arundel Wetland Centre sits within or close to Flood Zone 2 or 3, so heritage constraints and flood-zone constraints often apply to the same site at once, and a flood risk assessment for planning in Arundel has to work alongside conservation-area and listed-building requirements, not around them.

How Unda helps with a flood risk assessment in Arundel

We have prepared flood risk assessments and drainage strategies across West Sussex and the wider Arun valley, working through the district's chalk hydrogeology, tidal river dynamics and conservation-area planning constraints. Our flood risk consultants know how to read a site against the Arun's tidal reach, the Arun and Western Streams Catchment Flood Management Plan and Arun District Council's Strategic Flood Risk Assessment, and how to evidence a scheme against the council's SuDS design checklists.

That single line from Arun District Council's own planning policy is why a site-specific assessment matters here: national flood maps rarely tell the whole story on a chalk-and-river landscape like the Arun valley, and a proper flood risk assessment or drainage strategy has to close that gap for each site individually. Before commissioning a full report, it's worth checking a site against Unda's free Flood Risk Map, Live River Levels Map and Geology & Ground Conditions checker. They're useful first steps for any site near the Arun.

Flood risk assessments for every situation in Arundel

A flood risk assessment, a sequential or exception test and a drainage strategy are three distinct 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. We prepare all three for sites in Arundel and across the Arun valley.

• Flood risk assessment for planning: satisfies the NPPF and Arun District Council's validation requirements for sites in Flood Zone 2 or 3, 1ha+ in Flood Zone 1, or flagged for surface water risk.
• Flood risk assessment for property purchase: for buyers, lenders or conveyancers who need to understand the real flood risk to a specific building in Arundel, not just the national dataset.
• Flood risk assessment for insurance: for brokers and underwriters where premiums have risen or cover has been restricted on a property near the Arun.
• Flood risk assessment for BREEAM: structured around BREEAM's Pol 03 credit, assessing pre-development flood risk classification rather than planning safety.
• Sequential and exception tests: locational justification for sites in Flood Zone 2 or 3 where lower-risk alternatives must be considered.
• Surface-water drainage strategies (SuDS): calculating existing and proposed runoff and designing sustainable drainage to meet Arun District Council's checklists and the wider SuDS hierarchy, including discharge of drainage conditions and preliminary drainage design.

Groundwater is assessed as part of every flood risk assessment we prepare, not as a separate report. That matters in a chalk landscape like the Arun valley, where risk does not show on national flood maps (see our notes on what groundwater flooding is and how to check a groundwater flood risk map). Where a site sits close to the river or floodplain, we can also bring in flood modelling to establish accurate levels, extents and velocities, guided by the NPPF and case law such as the Yatton judgment on the exception test.

Local flood risk management and emergency contacts in Arundel

If flooding is happening now and lives or property are at immediate risk, call 999. For power cuts caused by flooding, call 105. Otherwise, the bodies below are Arundel's main points of contact for flood risk management, warnings and reporting.

• Sign up for flood warnings: free warnings for the Arundel flood warning area are available via Floodline (0345 988 1188) or the Environment Agency's check for flooding service.
• Ongoing scheme updates: Arundel Town Council and the Environment Agency publish updates on the Arundel Tidal Defence Scheme, which protects properties on both banks of the river.
• Wider West Sussex context: see our flood risk assessment in West Sussex and flood risk assessment in Sussex pages, or our coverage of neighbouring Chichester and Worthing.

Flood risk assessment in Arundel: frequently asked questions

Whether you need a flood risk assessment for a planning application near the River Arun, a drainage strategy to satisfy Arun District Council's SuDS checklists, or a report for a property purchase or insurance renewal, contact one of our experienced flood risk consultants today.