Flood Risk Assessment in Chester, Cheshire

A flood risk assessment in Chester, Cheshire, has to start with the tidal River Dee and the earth banks and walls that keep it off the low ground west of the city walls. Sealand Road, the Roodee and parts of Lache and Saltney are land the river would reach if a bank were overtopped or breached, and the drains that serve them empty into a river the tide can hold up. In Chester we prepare flood risk assessments for planning, for house buyers, for mortgage lenders and for insurance, as well as sequential and exception tests and surface water drainage strategies, for sites on both sides of the river.

By Chester we mean the city as the Office for National Statistics maps its built-up area: the centre and the Groves, Blacon and Upton to the north-west and north, Newton and Hoole to the north-east, Boughton and Great Boughton to the east, and Handbridge, Westminster Park and Lache south of the river, across the CH1 to CH4 postcode districts. The same outline runs over Boundary Lane into Saltney, which is in Flintshire and so in Wales. Christleton, Vicars Cross and Mickle Trafford sit just outside it, under the same council. Cheshire West and Chester Council decides applications on the English side and is the lead local flood authority there; the rest of the county is on our Cheshire page.

Five Environment Agency flood warning areas cover Chester: two for land behind the Northern and Hawarden Embankments, two along the river at the Roodee and the Groves, and one where Highfield Drain meets Finchett's Gutter at Abbot's Mead.

To talk through a Chester site, call 01293 214444 or email enquiries@unda.co.uk and one of our flood risk consultants will look at the address with you.

Which parts of Chester sit behind the Dee embankments?

Most of the defended land lies west and south-west of the city walls, either side of the tidal river. The council's 2026 Strategic Flood Risk Assessment lists the racecourse and the Sealand Road and Greyhound retail park areas among the main parts of the borough where defences reduce the risk. The Environment Agency's warning areas show street by street what sits behind them:

The planning flood zones are drawn as if those banks were not there, so a plot on Sealand Road can sit in Flood Zone 3 behind a bank built to keep the river out. The SFRA records 50 defence assets in and around the city, mostly embankments and walls, 31 of them the Environment Agency's, and where a design standard is recorded it is most often 1 in 100. Our guides to residual flood risk and to why land stays in a flood zone after defences are built explain what an assessment then has to show. When a tidal warning is in force, our live river levels map shows the gauges on Finchett's Gutter and along the Dee.

Screening a CH1, CH2, CH3 or CH4 address

Type a Chester postcode into the map to see the Environment Agency's planning flood zones, surface water and reservoir extents and any live warnings, or open our flood risk map to look up an address anywhere in England. The coral line follows the ONS built-up area, Saltney included. A screen cannot read a bank's crest level or a culvert's capacity, and in Chester those usually decide the answer.

Finchett's Gutter, the Sealand Basin and the drains the tide holds back

After the Dee itself, the 2026 SFRA names Finchett's Gutter as the main source of flood risk in Chester's growth areas. It runs south from the farmland north of the city, past Blacon, and turns west into the Dee, where the council's investigators found its levels can be raised by the tide. Several smaller brooks and drains feed it or run alongside:

• Finchett's Gutter. Shown as a main river on the Environment Agency's main river map. Its gauge at Knolls Bridge normally reads between 5.25 m and 6.93 m and reached 8.15 m on 21 January 2021, the highest on record there (Environment Agency). A second gauge sits at Countess Way, Abbot's Mead.
• Sealand Basin. An Environment Agency flood storage area west of the city centre, with part of the Backford Brook floodplain also used for storage (SFRA Appendix C).
• Two flood storage reservoirs. The SFRA lists Finchett's Gutter and Knoll's Bridge, both owned by the Environment Agency, among the high-risk reservoirs whose failure could affect the borough, so a reservoir flood extent can reach a site well away from any river.
• Highfield Drain. An ordinary watercourse from the fields around the A540 that enters a 900 mm culvert north of Browning Close and passes under the Shropshire Union Canal and Parkgate Road into Finchett's Gutter.
• Bache Brook, Backford Brook and Balderton Brook. Bache Brook is modelled by the Environment Agency together with Finchett's Gutter. Backford Brook has flooded on the northern outskirts and Balderton Brook on the southern, where land either side of it south of Saltney is functional floodplain or Flood Zone 3.

The council's Blacon investigation describes Finchett's Gutter as an ordinary watercourse, but the Environment Agency's own map shows it as main river, and that decides who consents to works on or beside it. Our note on main rivers and ordinary watercourses sets out the difference, and how reservoir flooding is mapped covers the storage reservoirs.

January 2021 and October 2023 in Blacon, Upton and the city

Chester's most recent floods came from drains and culverts rather than from the Dee overtopping its banks. Cheshire West and Chester Council investigated each one under Section 19 of the Flood and Water Management Act:

1. 2012. Several homes in the north of Blacon flooded inside; the council's later report calls the area regularly flooded. Gardens on Upton Park were flooded from the parkland behind them the same year.
2. 20 to 21 January 2021, Storm Christoph. The trash screen at the head of the Highfield Drain culvert blocked. Water ran through gardens into Browning Close and Chaucer Close, then down Parkgate Road to Abbots Mead, where traffic pushed bow waves into houses and about 1 m of water stood inside some of them. 27 properties flooded, 20 homes and 7 businesses, and 15 were evacuated (Blacon report).
3. The same storm in Upton. Water from Queen Elizabeth II Park reached the rear of houses on Upton Park, flooding cellars and one home, in an estate with no main river nearby (Upton Park report).
4. October 2023, Storm Babet. The council's 16 Section 19 reports name Chester, Lower Kinnerton and Blacon as the hotspots of internal flooding, with a surcharging sewer in Chester and road flooding in Lache and Vicars Cross (SFRA 2026).

After 2021 the Environment Agency added the Abbot's Mead warning area, and the council began lowering kerbs so water leaving Parkgate Road can find its way back into Finchett's Gutter. Our explainer on Section 19 flood investigations covers when a council has to carry one out.

Sewers on the Welsh Water network

Chester's public sewers belong to Dŵr Cymru Welsh Water. United Utilities, which runs the sewers across most of Cheshire, does not serve the city. Welsh Water gave the council 490 records of sewer flooding across its network in the borough between 2001 and mid 2024, and the SFRA says they are mainly clustered around Chester. Of the incidents recorded from 2015 to 2024, 17 were inside buildings and 65 outside, with Chester, Saltney, Christleton and Huntington among the places with most records.

Where the network already floods, Welsh Water may limit what a new connection can add, and an outfall to Finchett's Gutter or the Dee may be shut by the tide at the moment the rain is heaviest. A drainage scheme in Chester therefore needs to show where water is stored while the outfall is locked. How a water company's records feed into a planning decision is covered in our note on sewer flooding and planning.

Which local and national policies apply to a flood risk assessment in Chester?

On the English side, applications are judged against the Cheshire West and Chester Local Plan Part One (adopted January 2015) and Part Two (July 2019), with the council's March 2026 SFRA as the evidence behind them. National policy sits in chapter 18 of the NPPF.

The council is preparing a new Local Plan, and its issues and options paper suggests merging ENV 1 and DM 40 to DM 43 into one policy and keeping the Finchett's Gutter flood storage area free of building, so the numbers above may change before adoption, timetabled for December 2028. The council is consulted as lead local flood authority on surface water for major schemes and publishes a SuDS submission checklist. A site assessment starts from the SFRA's mapping and then tests it at plot scale, as our explainer on strategic flood risk assessments describes.

Wrexham Road, the Business Quarter and Sealand Road: where Chester is growing

Chester's planned growth splits between greenfield land on the southern edge, brownfield sites around the station and centre, and employment land on the tidal flats to the west. Each raises a different flood question:

Further sites at Dale Barracks on Liverpool Road, north of the Countess of Chester Hospital at Upton and off Melverly Drive appear in the SFRA's list of land that could be safeguarded for flood storage, which may affect how they are promoted. For new homes in Flood Zone 2 or 3, Cheshire West and Chester applies the sequential test across the whole borough.

Saltney and Boundary Lane: when Welsh policy applies

About a fifteenth of the built-up area on our map, mostly Saltney, lies west of Boundary Lane in Flintshire. The planning rules change at the lane. A planning application there goes to Flintshire County Council and is read against Welsh policy, so where a report is needed it is a Flood Consequence Assessment, not an English flood risk assessment:

• TAN 15. The current Technical Advice Note 15 took effect on 31 March 2025 and works from Natural Resources Wales's Flood Map for Planning.
• When an assessment is needed. Welsh Government guidance asks for one with applications in Zones 2 and 3, in TAN 15 Defended Zones and in the surface water and small watercourse zones.
• Local plan. The Flintshire Local Development Plan 2015 to 2030, adopted on 24 January 2023, deals with flooding in policy EN14 Flood Risk.
• Breach depths. Flintshire's 2018 Strategic Flood Consequence Assessment modelled a breach of the Dee defences at Mold Junction Drain, with water up to about 0.7 m deep on land just south of it in a 1 in 200 year event (SFCA).
• Drainage. Since 7 January 2019 Welsh developments of more than one house, or 100 m2 or more of construction, need sustainable drainage approved by the council as SuDS Approving Body before work starts.

For a Saltney site we prepare the assessment Welsh policy asks for in place of an English one; our guide to the Welsh flood zones explains the map it is read against.

Reports for Chester sites, from the Groves to Sealand Road

Every report below is scoped to the address, the bank or drain nearest to it, the sewer record and which side of Boundary Lane it falls:

• Applications to Cheshire West and Chester. A scheme on the English side in Flood Zone 2 or 3, from Sealand Road to the Groves, needs a flood risk assessment for planning that answers DM 40 and the 2026 SFRA.
• Every source together. One flood risk assessment weighs the tidal Dee, Finchett's Gutter, surface water, the Welsh Water sewers and the two flood storage reservoirs for a single site.
• Homes in a warning area. Before exchange on a house in the Groves, Lache or Abbots Mead, a flood risk survey for property purchase looks at the building's floor levels and the flood record for its street.
• Searching the whole borough. For new homes behind the banks, a sequential and exception test report shows whether a safer site is reasonably available anywhere in Cheshire West and Chester.
• Sewers that already flood. With 490 Welsh Water sewer flooding records clustered on the city, a drainage strategy shows where foul and surface water will go.
• Outfalls the tide can lock. A surface water drainage strategy meets DM 41's runoff limits and stores water on site while Finchett's Gutter or the Dee is too high to take it.
• After permission. We prepare the evidence for the discharge of drainage conditions that Cheshire West and Chester attaches to Chester consents.
• Depths if a bank fails. Where national mapping stops short, flood modelling built on the Environment Agency's models of the Lower Dee and Finchett's Gutter gives breach and overtopping depths for one plot.
• When the tide warning comes. For flats or a care home inside the Northern or Hawarden Embankment warning areas, a flood warning and evacuation plan sets the trigger, the route out and who acts.
• Units on the tidal flats. Sealand Industrial Estate and Chester West Employment Park sit inside the Northern Embankment warning area, and a business continuity flood risk assessment plans how a unit keeps trading through a warning or a breach.
• Homes that flooded in 2021. For houses in Blacon or on Parkgate Road, a flood risk assessment for insurance gives an underwriter evidence about the one address.
• Plots west of Boundary Lane. In Saltney a site is in Wales, so Flintshire asks for a Flood Consequence Assessment rather than an English report.
• The Welsh rules. Our TAN 15 guidance explains the zones, the Defended Zones and the tolerable depths a Saltney scheme is tested against.

Who deals with flooding in Chester, on both sides of the border

Call 999 if flood water puts anyone in danger, and 105 if it cuts the power. Otherwise, which body to contact depends on the source of the water and on whether the address is in England or Wales:

The Cheshire councils' flood partnership posts advice and recovery information on The Flood Hub. Elsewhere in the county, our Northwich page covers the Weaver and the Dane and our Warrington page the Mersey estuary, and Liverpool, at the far end of the Wirral, has its own page. The Dee from Bala to the estuary has a page of its own, and every other place we cover is in our list of areas.

Chester sites: questions owners and applicants ask

For a house in Hoole, a unit on Sealand Road or land in Saltney, call 01293 214444 or email enquiries@unda.co.uk. Our chartered consultants at Unda Consulting Limited, a CIWEM Business Partner, will say which reports the site needs, and a senior consultant signs off every report.