Flood Risk Assessment in Wigan

A flood risk assessment in Wigan, Greater Manchester, starts with the River Douglas, which runs through the town in a walled, largely artificial channel between an Environment Agency dam on its upstream side and the low ground at Poolstock and Robin Park downstream. Three culverted brooks join it from the estates: Barley Brook from Whitley and Gidlow, Smithy Brook from Pemberton and Worsley Mesnes, and Hawkley Brook from Hawkley Hall. For sites across the town we write flood risk assessments in Wigan to go with a planning application, to inform a purchase or to answer a lender or insurer, and we prepare sequential and exception tests and surface water drainage strategies for the same sites.

On this page Wigan means the town's built-up area as the Office for National Statistics draws it: the town centre, Wallgate, Newtown and Wigan Pier; Scholes, Whelley, Swinley, Gidlow, Beech Hill, Springfield and Whitley to the north and east; Pemberton, Lamberhead Green, Marsh Green and Standish Lower Ground to the west; and Poolstock, Worsley Mesnes, Goose Green, Hawkley, Highfield and Winstanley to the south, across the WN1, WN3, WN5 and WN6 postcode districts. Wigan Council is both the planning authority and the lead local flood authority.

Before the Douglas scheme, around 610 homes and 170 other properties in Wigan were at risk in a 1 in 100 year river flood, behind old walls an inspection had found in poor or very poor condition. The dam and new walls are designed to hold back that flood, but the town's mapped flood zones still ignore them.

To talk through an address in Wigan, call 01293 214444 or email enquiries@unda.co.uk. We check the site against the Douglas warning areas, the council's flood investigation reports and the Greater Manchester flood studies before we quote.

Is Wigan in a flood zone? The Douglas from Scholes to Robin Park

The river corridor is. Flood Zone 3 follows the Douglas through the town, and the Greater Manchester Level 1 SFRA (2019) lists Wallgate and Newtown as an area of considerable river flood risk, mostly commercial premises and open land, with historic flood outlines in both. Away from the river most of the town is in Flood Zone 1, though Hawkley is on the SFRA's list of existing housing areas in Flood Zone 3, from the culverted Hawkley Brook. Two Environment Agency warning areas and one alert area cover the Douglas here:

The Douglas rises fast. On Boxing Day 2015 the Wigan gauge climbed 1.4 m in the two and a quarter hours before its 14:15 peak and finished a metre above anything in its 38 years of records, according to the Greater Manchester flood investigation. The Environment Agency issues the Wigan warnings from its Cumbria and Lancashire office, because the Douglas drains west to the Ribble estuary. Our live river levels map shows the Wigan and Red Rock readings as they report.

Look up a WN1, WN3, WN5 or WN6 postcode

Type a postcode into the map to see the planning flood zones, surface water extents and any warning in force, or open our flood risk map for anywhere in England. The coral outline is the Wigan built-up area from the Office for National Statistics; Ince, Hindley, Standish and Orrell sit outside it.

The dam above Coppull Lane and the walls through the town centre

Wigan's river defences came in two phases under the Environment Agency's Douglas strategy. The first replaced the old privately built walls, some of which had leaked into Eleanor Street in August 2004; the second built a flood detention reservoir in the valley above the town, which the council's flood strategy records as operational from 2011.

• Phase one, south of the centre. About 1,000 m of new and raised walls and 300 m of embankment, up to 1.8 m high in places, with the riverside path raised so walkers can still see the water. On their own they gave roughly a 1 in 20 year standard (British Dams Society paper, 2010).
• Phase two, the dam. An 8 m dam upstream of Coppull Lane with two Hydro-Brake flow controls that hold back about 370,000 cubic metres of floodwater in the Douglas valley and let no more through the town than the channel can carry. Wigan Council puts the £12 million scheme's combined standard at 1 in 100 years.
• Inside the reservoir basin. The stored water backs up towards Haigh Hall bridge and Leyland Mill, and the design allows the crest to be raised later for climate change.
• Safeguarded in the new plan. Draft Policy EN11 in the Publication Local Plan protects the Wigan Flood Alleviation Scheme from development that would reduce its storage.

Two consequences follow for a site. The flood zones used for the sequential test are drawn without the defences, so land at Poolstock or Robin Park stays in Flood Zone 3 however well the dam performs. And the dam is itself a reservoir: the 2019 SFRA notes that Wigan town centre could be badly flooded if an upstream dam failed, so a flood risk assessment here reads the reservoir flood map as well as the river map.

Barley Brook, Smithy Brook and Hawkley Brook: Wigan's buried tributaries

Wigan's worst recent flooding has come from brooks the town has built over. All three below are main rivers, so the Environment Agency rather than the council regulates works on them, but much of their length runs in culverts, siphons and pipes owned by railway, canal and private landowners. The 2019 SFRA notes that Wigan Council listed its top 20 culverts in critical condition.

• Barley Brook, Whitley to Pagefield. Runs in a long Network Rail culvert to Spencer Road, then under the Pagefield estate and through a siphon beneath the Leeds and Liverpool Canal. A tree trunk jammed the timber siphon in 2008, and debris in the culverts flooded Beresford Street in 2012 and Havenwood Road in 2023.
• Smithy Brook, Pemberton and Worsley Mesnes. A main river tributary that the SFRA names among Wigan's watercourses not yet modelled for climate change. On Boxing Day 2015 high water in the brook stopped drains emptying, and eight properties at Worsley Mesnes flooded from surface water, all of them in Flood Zone 1.
• Hawkley Brook, Hawkley Hall. Culverted for much of its length. On 14 June 2016 it rose high enough to stop the surface water sewer discharging, and water came back up through manholes into Colby Road and Fulbeck Avenue.

A flood zone map says little about this kind of flooding, so an assessment near one of these brooks finds where the culvert runs, who owns it, whether a screen guards the inlet and what happens on the site if it blocks. Our explainer on culverts and who maintains them covers the ownership side.

Floods recorded in Wigan from 2000 to 2023

Wigan Council investigates any flood that reaches five homes or two businesses, and its reports, with the Environment Agency's, give a street-level record for the town:

1. 29 October 2000. The Douglas overtopped its channel and flooded the Kwik Fit garage, the old bus depot and two houses on Eleanor Street (Wigan Local Flood Risk Management Strategy, 2014).
2. 2008. The trunk lodged in the Barley Brook siphon under the canal flooded properties on Beresford Street, and the combined sewer surcharged into Gorman Street, mixing sewage with the floodwater.
3. 22 June 2012. Fourteen homes on Beresford Street and Gorman Street flooded internally from the blocked Barley Brook culvert, with 300 mm of water in the Miry Lane industrial estate turning circle (Wigan Council flood investigation).
4. 24 September 2012. Eight homes and a business at Eleanor Street, the Saddle junction and Wallgate flooded to depths of 300 mm to 750 mm when the combined sewer and highway drains backed up against a swollen Douglas.
5. 26 December 2015. Storm Eva put 66 mm of rain on the Worthington gauge in a day. Nine properties flooded at Worsley Mesnes, with smaller clusters in Whelley, Beech Hill and Scholes, and lengths of the Douglas retaining walls were damaged (Greater Manchester Section 19 report).
6. 14 June 2016. A short, intense storm flooded 20 properties, 16 of them around Hawkley Hall and four on Cavendish Drive in Winstanley.
7. 6 November 2023. Fly-tipped tyres and branches blocked the Barley Brook culvert under Spencer Road behind a broken debris screen. Havenwood Road and May Tree Drive flooded from late afternoon until 3am, and sewage backed up from the overloaded foul pumping station.

The council's flood investigation reports are public, and they are among the first documents we read for a Wigan address.

Policy CP16, draft Policy EN10 and what a flood risk assessment in Wigan must show

Three layers of policy apply. National policy in chapter 18 of the NPPF decides when an assessment is needed and how the sequential and exception tests work; Places for Everyone sets runoff rules across nine Greater Manchester boroughs; and Wigan's own Core Strategy, now being replaced, adds local discharge targets.

The evidence assessment gives a town centre example. Land next to the Premier Inn on Harrogate Street was screened in the Level 2 SFRA, which judged it unlikely to pass the exception test because of residual and long-term risk from the Douglas. The council has since cut the developable area back to the frontage in Flood Zone 1, and asks for any assessment there to carry a drainage strategy and an emergency plan with safe access and exit routes. Our guide to the National Standards for sustainable drainage explains the drainage side of EN10.

Combined sewers, the canal and rain that cannot drain

In the older terraces around the town centre, surface water and foul sewage share United Utilities' combined sewers. The September 2012 flood at Eleanor Street happened without the sewer overflowing: it was full enough that the road gullies could not empty into it, and under Wallgate bridge one gully sits 540 mm below the soffit of Adam Bridge, so a high Douglas probably drove water back up the highway drain. Wigan Council later fitted attenuation tanks during the Saddle junction works. The same pattern of an outfall drowned by the receiving watercourse turns up at Worsley Mesnes in 2015, Hawkley Hall in 2016 and Havenwood Road in 2023.

For a new scheme that makes the outfall level as important as the discharge rate. A surface water strategy in Wigan checks the level of the brook or river when the storm arrives as well as how much water leaves the site, and where infiltration is possible the soakaway and ground conditions checker is a sensible first look before testing. The Leeds and Liverpool Canal, which crosses Barley Brook by siphon and runs past Wigan Pier, is assessed for overtopping and breach wherever a site sits below its banks. Our note on sewer flooding explains who answers for which pipe.

Reports for Wigan sites, from Pemberton terraces to Robin Park

Every report starts from the same Wigan questions: which side of the Douglas walls the site sits, what brook or culvert lies upstream, where its water can go and what the council, a lender or an insurer has asked to see.

• Applying to Wigan Council. A scheme in Flood Zone 2 or 3 beside the Douglas, on a hectare or more, or over one of the culverted brooks needs a flood risk assessment for planning that answers CP16, the emerging EN10 and the Greater Manchester SFRA.
• River, brook, sewer and reservoir. A flood risk assessment for a Wigan address looks at the walled Douglas, the culverts upstream of the site, the combined sewers, the canal and the reservoir map together.
• Buying in Scholes, Poolstock or Hawkley Hall. Before exchange on a house in a Douglas warning area or near a recorded flood street, a flood risk survey for property purchase sets out what has happened there and what the defences do and do not cover.
• Homes in Flood Zone 3. New dwellings at Wallgate, Newtown or Poolstock stay in Flood Zone 3 despite the dam, so the council expects a sequential and exception test report alongside the assessment.
• Foul and surface water together. Where the only outlet is a combined sewer, a drainage strategy sets out both flows and the connection United Utilities will accept.
• CP16 runoff targets. A brownfield site must cut runoff by at least 30%, or 50% in a critical drainage area, and a surface water drainage strategy shows how, with the outfall level checked against the receiving brook.
• After the permission. Wigan permissions often carry pre-commencement drainage conditions, and the discharge of drainage conditions means sending the council the calculations, plans and maintenance arrangements it asked for.
• Brooks without climate change data. Smithy Brook and Ince Brook have no modelled climate change extents in the SFRA, and flood modelling can fill that gap for a site beside them or below a culvert that could block.
• Inside the Poolstock and Scholes warnings. Flats, care homes and workplaces in the two Douglas warning areas often need a flood warning and evacuation plan tied to the Wigan gauge.
• Commercial land by the river. Buyers and lenders on the retail and industrial land at Robin Park, Miry Lane and Wallgate, which the SFRA places in the Douglas floodplain, use a due diligence flood risk assessment before they commit.

Ince, Hindley, Standish and the rest of the borough

Wigan Council plans for a borough of separate towns, and the outline on this page stops at Wigan itself. Ince-in-Makerfield and Hindley to the east, Standish and Haigh to the north, Orrell and Billinge to the west, and Ashton-in-Makerfield and Leigh to the south are mapped as places of their own, several of them in the Glaze Brook or Sankey Brook catchments with different warning areas and a different Environment Agency office. Westwood Park, a proposed housing allocation in the new plan with Flood Zone 2 land around Westwood Flash, lies just beyond the outline between Poolstock and Ince. We still prepare assessments across all of them.

For the wider region, see our pages for Manchester, Salford on the Irwell and Warrington on the Mersey. The Douglas itself ends in the Ribble estuary below Preston. Every town and county we cover is listed on our areas page.

Wigan Council, United Utilities or the Environment Agency: who handles which flood

In Wigan the body you call depends on whether the water came from the Douglas, a brook, a sewer or the road:

Culverting, diverting or building beside an ordinary watercourse in Wigan needs the council's land drainage consent. On the Douglas or any of the main river brooks the Environment Agency's permission applies instead.

Wigan flood questions from buyers and applicants

Whether it is a house on Eleanor Street, a yard at Robin Park or a plot off Spencer Road, call 01293 214444 or email enquiries@unda.co.uk. Every report our chartered consultants prepare is signed off by a senior consultant, and Unda Consulting Limited is a CIWEM Business Partner.