Flood Risk Assessment in Arundel

A flood risk assessment in Arundel usually starts at the river walls. The tidal River Arun runs along the east side of the town, and the homes and shops on River Road, Tarrant Wharf and Fitzalan Road sit behind walls the Environment Agency rebuilt in two phases between 2019 and 2024. We prepare flood risk assessments in Arundel for planning applications, house purchases, mortgages and insurance, together with sequential and exception tests and surface water drainage strategies.

On this page Arundel is the town as the Office for National Statistics draws its built-up area: the castle and the cathedral on the hill, the High Street, Maltravers Street and Tarrant Street, the riverside along River Road down to Queen Street bridge, Fitzalan Road on the far bank, and Torton Hill and Ford Road to the south-west. It falls in the BN18 postcode district. Warningcamp and Burpham, upriver on the east bank, lie outside the outline but share the town's flood warning area.

Arun's 2026 flood study warns that several walls along the river through Arundel give some protection without being recognised flood defences, and are unlikely to be maintained, so an assessment for a site near one has to consider a local breach.

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

Arun District or the National Park: who decides a planning application in Arundel?

Two planning authorities share Arundel, and the line between them is drawn tightly round the town. Arun District Council decides applications on the town streets: the High Street, Maltravers Street, Tarrant Street, Queen Street, River Road, Fitzalan Road, Ford Road and Torton Hill. The castle, the cathedral, Mill Road and Arundel Park lie inside the South Downs National Park, where the National Park Authority decides. Arun's Local Plan says as much: Arundel stays within Arun's planning area, but Arundel Park and much of the Town Council's area fall within the park.

Check which side of the line a site falls on before anything else. The two authorities want much the same evidence, but a report has to cite the policies and the flood study of the one deciding the application. West Sussex County Council is the Lead Local Flood Authority on both sides, and the Environment Agency is responsible for the river. Both plans are being replaced. The National Park's new Local Plan, with policies SDW2 and SDW3, had its final consultation from 12 May to 23 June 2026 (proposed submission plan), and Arun's update is further behind (its 2025 to 2028 timetable puts the final consultation in 2027), so applications are judged against the adopted policies in the table. Our guide to Arun District Council's flood and drainage requirements covers the district rules in more depth.

Arundel's river walls: the 2016 collapse, the rebuild and who maintains them now

Arundel's riverside is held by walls rather than wide embankments, and for years some were in poor repair. In the early hours of Friday 8 January 2016 a privately owned stretch of flood wall on River Road collapsed. Arun District Council's statement records that the Environment Agency set up a temporary barrier and pumps to protect homes through the next high spring tide, and that utilities to three properties were cut off. The collapse set off the Arundel Tidal Walls Scheme.

1. March 2014. The Environment Agency approves the Lower Tidal River Arun Strategy, covering the valley from Pallingham Weir to Littlehampton and Ford for the next 100 years.
2. January 2016. The River Road wall falls. A week later Arun District Council, the Agency, the county council, Angmering Park Estates and residents agree a recovery plan.
3. November 2019. Phase 1 begins: new defences at River Road and Tarrant Wharf and a strengthened wall along Fitzalan Road, estimated at £6.7 million, to better protect up to 130 properties from flooding and 30 more from erosion.
4. August 2020. Phase 1 is complete.
5. July to November 2023. Phase 2 starts on 31 July. Contractors drive 18-metre steel piles into the riverbed for a 93-metre sheet pile wall protecting 176 homes on River Road, Tarrant Wharf and nearby streets. The old masonry wall at Tarrant Wharf partly gives way during piling on 27 October; piling ends on 25 November.
6. November 2024. With the capping beams and finishing work done, the site compound is cleared. The Agency's final newsletter says the scheme meets the Lower Tidal River Arun Strategy and that there is no strategic need for further Environment Agency flood defence works in Arundel.

The same newsletter says future works and maintenance of the river walls in the town fall to the riparian owners. That is a practical question for anyone buying or building by the river: who owns the wall in front of the site, what state it is in, and what follows if nobody repairs it. Our article on riparian ownership explains those duties, and our note on residual flood risk sets out how an assessment treats a site that is defended but not risk-free. The March 2026 SFRA leaves the undesignated walls out of its flood mapping, so the mapped extents are not understated, and expects a site-specific assessment close to them to test the depths and velocities a breach could bring.

Check a postcode between the castle and Ford Road

Type an Arundel postcode below to screen it against Environment Agency data for rivers and the sea, surface water and reservoirs, or use our flood risk map for anywhere in England and Wales. The coral line is Arundel's 2022 built-up area, not the whole of Arun district. A screening is only a first look: it cannot show a floor level, the condition of a private wall or the depth to groundwater.

Is Arundel in a flood zone? Five sources in one small town

Parts of it are. The 2026 SFRA finds the Flood Zones around Arundel mainly on the east bank of the Arun, and the surface water extents mostly on the west bank and in the town centre. The town on the hill is largely clear of the river zones, but surface water reaches much of the town centre that the river does not. Flood Zones take no account of defences, so a riverside home behind the new walls is still in Flood Zone 3 for planning purposes.

Groundwater often decides whether a drainage scheme works here, because Arun expects infiltration to be tested before any other way of discharging surface water; our guide to groundwater evidence in planning applications covers what to submit. The reservoir flooding article explains the dry-day and wet-day scenarios. For the river from the Weald to the sea, see our River Arun page.

Floods recorded in Arundel since 1810

Arundel has a long flood record. The Chronology of British Hydrological Events, quoted in the 2026 SFRA, notes the levels inundated “particularly at Arundel” after heavy rain in the autumn of 1841, and snowmelt flooding in February 1847. The modern record is shorter and better measured.

• 1810 to 1927. Events recorded in November 1810, December 1839, autumn and winter 1841, February 1847, 1865, 12 November 1913 (river and surface water) and March 1927.
• 1993 to 1994. Arun District Council records flooding at the wildfowl reserve in Arundel.
• 6 December 2013. The River Arun at Arundel gauge reaches 3.65 m, still its highest reading. Low-lying land can flood once the river passes 3.30 m, and property flooding is possible above 3.75 m.
• Winter 2013 to 2014. Environment Agency recorded flood outlines show the Arun valley flooding from December 2013 to February 2014, with a further outline on 5 March 2014 covering the valley and Arundel.
• January 2016. The River Road wall collapse described above.
• November 2023. Through Storm Ciarán and the high tides of 1 and 2 November, scheme staff stood by on River Road with pumps ready. The Agency reported no flooding in that period.

Arundel lies in the Environment Agency's Arundel on the River Arun flood warning area, which also takes in Warningcamp and Burpham. The Arundel gauge, Houghton Bridge upstream and Littlehampton downstream can all be followed on our live river levels map.

Policies W DM2 and SD49: what an Arundel application has to show

On the Arun side, policy W DM2 allows development in an area at risk only when all six of its criteria are met, and W DM3 sets the drainage standard. Inside the National Park, SD49 and SD50 do the same job more briefly. A report written to one authority's policies will not satisfy the other's by chance.

• W DM2, Arun. The sequential test met; a site-specific assessment showing the scheme safe, including access and egress, without raising risk elsewhere; wider sustainability benefits; adaptation and mitigation; flood warning and evacuation plans; and drainage that allows for exceedance. Proposals must also take account of the Lower Tidal River Arun Strategy.
• W DM3, Arun. SuDS on every scheme, source control even on minor sites, up to six months of winter groundwater monitoring, winter infiltration testing to BRE 365, no flooding in a 1 in 30 year storm, and no flooding of homes, the highway or the foul sewer in a 1 in 100 year storm plus 30% for climate change.
• SD49, National Park. Development steered away from flood risk and towards Flood Zone 1, the sequential and exception tests where relevant, no increase in risk elsewhere, and river defences left intact. Mitigation needs a maintenance schedule, a named body responsible and funding in perpetuity.
• SD50, National Park. No net increase in surface water runoff, allowing for climate change; SuDS on major schemes unless shown to be inappropriate, priority for them elsewhere where the LLFA asks; and arrangements for their whole-life care.
• Arundel Neighbourhood Plan. Policy 12 supports new flood defences and safeguards the land the Environment Agency needs to deliver the Lower Tidal River Arun Strategy.

Arun's drainage engineers add five checklists published in October 2025, for outline and full applications, ground investigations, maintenance and verification; our article on Arun's SuDS checklists works through each. The council's position on surface water also keeps SuDS features out of Flood Zones 2 and 3 unless the whole site lies in them, with limited exceptions. Where a scheme depends on infiltration, our soakaway geology checker and BRE 365 infiltration rate calculator give an early indication before the winter tests.

National policy sits in chapter 18 of the NPPF: policy F4 sets when an assessment is needed, F5 and F6 cover the sequential and exception tests, and F8 expects all development to follow the 2025 National Standards for sustainable drainage.

Which schemes need a flood risk assessment in Arundel?

You need one for any site in Flood Zone 2 or 3, for sites of a hectare or more, and for smaller sites another source puts at risk, which takes in a large share of Arundel. The Neighbourhood Plan sites show the pattern: each came with a flood requirement written into its policy.

Splitting a house into flats or adding a dwelling changes how vulnerable the use is, which is often what brings the requirement in; see converting a house into flats and extensions in a flood zone. The allocations come from the Arundel Neighbourhood Plan review.

Reports we prepare for Arundel's riverside, town centre and park edge

A flat on River Road, a brownfield site off Fitzalan Road and a building inside the National Park each raise their own questions, so each report is shaped to its site. Unda is a CIWEM Business Partner, our consultants are chartered, and no report goes out until a senior consultant has signed it off.

• Planning applications on either side of the boundary. Arun and the National Park each expect a flood risk assessment for planning that answers their own policy, W DM2 or SD49.
• Rivers, rain, chalk and a lake. A flood risk assessment for an Arundel site sets the tidal Arun and the walls beside surface water, groundwater, sewers and Swanbourne Lake.
• Buying near the river. Before exchange, a flood risk survey for property purchase looks at one building on River Road or Tarrant Wharf, its floor level and the wall in front of it.
• Homes on the riverside and the east bank. New housing there needs the sequential and exception test; the Fitzalan Road allocation passed both.
• Drainage evidence at application. A drainage strategy sets out how foul and surface water will leave the site, to Arun's W DM3 or the park's SD50.
• Runoff on chalk. A surface water drainage strategy has to show whether infiltration works, which on Arun's side means winter groundwater monitoring and winter BRE 365 tests.
• Conditions on an Arundel permission. Where the decision notice holds back the drainage details, discharge of drainage conditions puts the evidence Arun's full checklist asks for before the council.
• Levels behind the walls. Where national mapping cannot show what a breach of an undesignated wall in Arundel would do to a riverside site, flood modelling provides the depths and velocities.
• Warning and a way out. W DM2 asks for flood warning and evacuation plans in areas at risk; a flood warning and evacuation plan links a riverside site to the Arundel warning area and a dry route out.
• Insurance on River Road and Tarrant Wharf. Where cover on an Arundel riverside home is loaded or refused, a flood risk assessment for insurance gives the insurer evidence for that building, including the rebuilt walls.
• Groundwater near the river. Where the water table sits close to the surface in parts of Arundel, a groundwater flood risk assessment looks at cellars, foundations and soakaways.
• Sewer capacity. The Neighbourhood Plan ties occupation of the Fitzalan Road and Causeway sites to new sewerage infrastructure, and a foul drainage strategy shows where and when a scheme can connect.
• Buying land by the river. Before acquiring brownfield land on Arundel's east bank, due diligence sets out the flood constraints and how they may limit what can be built.

Reporting flooding and getting warnings in Arundel: the bodies involved

If lives are at risk, call 999. If flooding has cut the power, call 105. For everything else, these are the bodies that cover Arundel.

For the county picture see flood risk assessment in West Sussex. Downriver, the estuary has its own page, flood risk assessment in Littlehampton, and along the coast there are pages for Worthing and Chichester. Every place we cover is in our index of areas.

Questions about flood risk in Arundel

Unda Consulting Limited prepares flood risk assessments, sequential and exception tests and drainage strategies for homes, businesses and land across Arundel, from River Road and Tarrant Street to Torton Hill and the park edge. To discuss a site, call 01293 214444 or email enquiries@unda.co.uk.