Level 2 Strategic Flood Risk Assessment (.pdf ... - Wigan Council

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The Town and Country Planning Order 2006 7 defines Critical Drainage Areas as “an areawithin Flood Zone 1 which has critical drainage problems and which has been notified…[to]…the local planning authority by the Environment Agency.” However, the EnvironmentAgency Standing Advice 8 also recognises the part that SFRAs play in identifying areas withdrainage problems and in doing so highlighting areas that need a FRA to consider drainage indetail.Certain locations are particularly sensitive to an increase in the rate of surface water runoffand/or volume from new development. There are generally known local flooding problemsassociated with these areas. These areas have been defined as CDAs in the SFRA.Specific drainage requirements are required in these areas to help reduce local flood risk.These are areas with complex surface water flooding problems that would benefit from aSurface Water Management Plan and subsequent drainage strategy.The SFRA has developed Critical Drainage Areas where:1. There is a high risk of localised flooding from ordinary watercourses, includingculverts surcharging and overland surface water flows, including the potential forflooding from the sewer network due to failure/ blockage or exceedance events whenthe storm return period is greater than the sewer was designed for.2. Where there are areas of significant redevelopment planned that could have asignificant impact on surface water runoff to local watercourses and the sewernetwork.Screening for Critical Drainage Areas (CDAs) within the borough was undertaken using datafrom the following sources:Wigan local authority incident recordsWigan Fire and Rescue MapsThe national Areas Susceptible to Surface Water Flooding mapAn assessment of properties at risk based on the ASSWF mapFEH CatchmentsUnited Utilities Drainage Area CatchmentsHistorical records from Environment Agency and United UtilitiesThe historical flood records from United Utilities, the Environment Agency and Wigan councilwere analysed to help identify any CDAs throughout the borough. It was assumed that wherea historical record exceeded an eight metre distance from a watercourse (D009_005), theevent was presumed to be from surface water runoff or by exceeding sewer capacities. Amap of these locations can be found in Appendix C.United Utilities provided historical flooding records for this SFRA. Details of the sewernetwork were not made available for use in this assessment. The sewer network can have asignificant impact on the location of surface water and sewer flooding for more frequentevents. It can also affect the distribution of water throughout urban catchments during floodevents, passing excess flows from the combined network into watercourses throughcombined sewer overflows. It was agreed that without the detailed UU data, naturalcatchments would be combined with UU Drainage Areas (showing where sewer systems areinterconnected across the boundaries of natural catchments) to define CDA boundaries.Using available data, screening was undertaken to identify Critical Drainage Areas. TheCDAs for Wigan have been typically identified by a significant density of high vulnerabilityASTSWF data, historical flooding records and United Utilities defined drainage area7 HMSO (2006) The Town and Country Planning (General Development Procedure) (Amendment) (No. 2) (England)Order 20068 Environment Agency. Flood Risk Standing Advice for England - PPS25 National Version 2.0. Can be accessedonline at http://www.environment-agency.gov.uk/research/planning/82584.aspx2009s0578 Final SFRA with Environment Agency Comments - L2 Ver5 Wigan.doc 25
oundaries. Nine key CDAs have been identified and prioritised on this basis. These arelisted in Table 5-1 below and included in map number 2009s0578 - D007-001.Table 5-1: Critical Drainage Areas & Associated Development SitesCDA Sites Site Type1 Landgate Candidate KeyStrategic SiteStubshaw CrossSouth Lancashire Industrial EstateLand r/o 42 Booths Brow Road, AshtonLow Bank Garage, Low Bank RoadSite of Britannia Inn, 361 Wigan Road, Ashton-In-Makerfield, WiganAshton Reservoirs, Druid St/Mill St, AshtonLiverpool Road, AshtonOff Lincoln Drive, AshtonSite of Cranberry Hotel and 641-643 Wigan RoadAshton FC Ground off Golborne Road, AshtonAdjacent to 233 Wigan Road, Ashton-In-Makerfield, WiganCorner of Princess Road/York Road, AshtonMillingford Grove, AshtonRockleigh Hotel, 50 Bolton RoadOpen land north east of 612 Bolton Road, Ashton-In-MakerfieldCandidate KeyStrategic SiteELASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAA2 Part of Newton Road PEA, Lowton SHLAALowton Junior and Infant SchoolGolborne High SchoolLowton High SchoolThe Bungalow and Scrap Yard, Pocket Nook Lane, LowtonOpen land north of 248 Slag Lane, LowtonLand to northwest of Lowton Civic Hall, Hesketh Meadow Lane,LowtonSpruce Close, LowtonPocket Nook, LowtonRothwells Farm, GolborneStirrups Farm, GolborneSHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAASHLAA3 Stone Cross Park ELAJ & E W Shimmin Transport, Ashton RoadGolborne High SchoolSHLAASHLAA2009s0578 Final SFRA with Environment Agency Comments - L2 Ver5 Wigan.doc 26
Page 1 and 2: Wigan Borough Hybrid SFRAVolume I:
Page 3 and 4: JBA OfficeJBA ConsultingSouth BarnB
Page 5 and 6: AcknowledgmentsJBA would like to ac
Page 7 and 8: Understanding flood risk from a pla
Page 9 and 10: 8.3 Planning considerations........
Page 11 and 12: AbbreviationsABDAreas Benefiting fr
Page 13 and 14: The key objectives of a SFRA are to
Page 15 and 16: 2 Flooding from RiversA detailed as
Page 17 and 18: 1. Astely Brook2. Bedford Brook3. W
Page 19 and 20: Unique ID Watercourse Description L
Page 21 and 22: 2.7 Understanding flood risk from a
Page 23 and 24: For example, flooding may affect ke
Page 25 and 26: 3 Flooding from CanalsThe SFRA has
Page 27 and 28: 3.2.2 Canal breach methodologyCanal
Page 29 and 30: 4 Flooding from ReservoirsFollowing
Page 31: direction in Future Water3, Making
Page 35 and 36: CDA Sites Site TypeLark Hill, Astle
Page 37 and 38: particular hotspots where surface w
Page 39 and 40: important role to play in reducing
Page 41 and 42: In the reverse situation, where flo
Page 43 and 44: 8 Summary of riskA summary of flood
Page 45 and 46: Having followed this procedure it i
Page 47 and 48: 9 Outline Mitigation OptionsChapter
Page 49 and 50: Water-resistant materials for floor
Page 51 and 52: JBA Consulting - Engineers Scientis
Page 53 and 54: JBA Consulting - Engineers Scientis
Page 55 and 56: Table B-1: Flood Risk Balance Sheet
Page 57 and 58: Map Name Map Reference Map Title De
Page 81 and 82: D . Wigan Council - Data RegisterXX
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E . SUDs SuitabilityNew SiteReferen
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New SiteReferenceWig 354Site Addres
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New SiteReferenceWig 855Wig 857Wig
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New SiteReferenceWig 716Wig 706BSit
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Site Reference Site Location Soil T
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F . Flood Zone 3 Proposed Developme
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G . Environment Agency comments on
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Flood Hazard MappingThe Level 2 rep
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Planning LiaisonEnvironment Agency
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Guide makes further summation diffi
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Wigan Metropolitan Borough CouncilC
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of the extent of any works required
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Planning & Transport StrategyWigan
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Again, avoiding generalities, we ha
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EA comment:Guidance on the preparat
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Please give me a call to discuss wh
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RECORD OF MEETINGStatus:JBA Project
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Level 2 Strategic Flood Risk Assessment (.pdf ... - Wigan Council

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