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

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Wigan Metropolitan Borough CouncilCivic Buildings (4) New Market StreetWiganLancashireWN1 1RPOur ref:01/IS1-L01Your ref:SO/2006/000257/SF-Date: 11 November 2010FAO: Damian GarnerDear DamianDRAFT STRATEGIC FLOOD RISK ASSESSMENTThe Environment Agency has reviewed the draft strategic flood risk assessment andwould like to make the following comments.1) Level 2 ReportDevelopment behind DefencesParagraph 3.65 of the PPS25 Practice Guide advises the following when consideringdefences within a level 2 SFRA: The SFRA should contain an appraisal of current condition of flood defenceinfrastructure and of likely future flood management policy with regards to itsmaintenance and upgrade. The SFRA should contain an appraisal of the probability and consequences ofovertopping or failure of flood risk management infrastructure, including andappropriate allowance for climate change.Although the Level 2 report lists defences within the borough of Wigan, there appears tobe no appraisal of defence condition or likely future management. In addition it is notclear as to whether breach analysis of the defences for strategic development isrequired / has been undertaken. This information will inform both the sequential andexception tests as required by PPS25.We would welcome further discussion on this issue as the Council will need to besatisfied that strategic planning decisions are being informed on a sound basis.Environment AgencyAppleton House, 430 Birchwood Boulevard, Birchwood, Warrington, Cheshire, WA3 7WD.Customer services line: 08708 506 506Email: enquiries@environment-agency.gov.ukwww.environment-agency.gov.ukCont/d..
Flood Hazard MappingThe Level 2 report (Page 16) makes reference to flood hazard being presented on thefollowing scale:1) No Hazard2) Very Low Hazard3) Danger for Some4) Danger for Most5) Danger for AllHowever both flood hazard maps present the keys as the following:1) Area of Low Hazard2) Area of Some Hazard3) Area of High Hazard4) Area of Highest HazardWe would recommend that the key on the hazard maps is amended to reflect thehazard rating as outlined within the Level 2 report. This would avoid any confusion forreaders of the document.Section 8: Summary of RiskWe would refer to the following paragraph in this section:“..to identify whether there is a need for strategic flood risk mitigation measures orwhether it is possible for new development to be permitted and provisions to be madeon a piecemeal basis ( it should be noted that this is not the preferred approach toPPS25 )”We would expect the SFRA to be carried out in accordance with PPS25 to ensure it isa sound piece of evidence to support the Council’s Local Development Framework.Further clarification on this is required.Flood Risk GuidanceThe Sequential test table provides data on the extent of each flood risk zone for siteshighlighted for development within Wigan. Also the supporting SFRA maps provide thebaseline data for the Council to apply the Sequential and Exception test (i.e. HazardMaps, Depth Mapping, Canal Hazard Zones etc).In addition to this, it would be useful for the Level 2 SFRA to provide descriptive textwithin the Level 2 report which brings this information together within a ‘flood risksummary’. This would be particularly important for strategic sites and locations withinthe Council’s Local Development Framework. This approach is supported by paragraph3.65 of the practice guide.Design Standards for the River Douglas ABDThe current NFCDD indicates that the design standards used to create the ABD fromthe River Douglas are incorrect and have recently (July/August 2010) been updated.We would recommend that this is verified again and I would advise you to contactGareth Hamlett (Assett Systems) on 01772 714105 to discuss in further detail.Cont/d.. 2
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Wigan Borough Hybrid SFRAVolume I:
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JBA OfficeJBA ConsultingSouth BarnB
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AcknowledgmentsJBA would like to ac
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Understanding flood risk from a pla
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8.3 Planning considerations........
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AbbreviationsABDAreas Benefiting fr
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The key objectives of a SFRA are to
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2 Flooding from RiversA detailed as
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1. Astely Brook2. Bedford Brook3. W
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Unique ID Watercourse Description L
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2.7 Understanding flood risk from a
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For example, flooding may affect ke
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3 Flooding from CanalsThe SFRA has
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3.2.2 Canal breach methodologyCanal
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4 Flooding from ReservoirsFollowing
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direction in Future Water3, Making
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oundaries. Nine key CDAs have been
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CDA Sites Site TypeLark Hill, Astle
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particular hotspots where surface w
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important role to play in reducing
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In the reverse situation, where flo
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8 Summary of riskA summary of flood
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Having followed this procedure it i
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9 Outline Mitigation OptionsChapter
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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
Page 83 and 84: E . SUDs SuitabilityNew SiteReferen
Page 85 and 86: New SiteReferenceWig 354Site Addres
Page 87 and 88: New SiteReferenceWig 855Wig 857Wig
Page 91 and 92: New SiteReferenceWig 716Wig 706BSit
Page 97 and 98: Site Reference Site Location Soil T
Page 99 and 100: F . Flood Zone 3 Proposed Developme
Page 101: G . Environment Agency comments on
Page 105 and 106: Planning LiaisonEnvironment Agency
Page 107 and 108: Guide makes further summation diffi
Page 109 and 110: Wigan Metropolitan Borough CouncilC
Page 111 and 112: of the extent of any works required
Page 113 and 114: Planning & Transport StrategyWigan
Page 115 and 116: Again, avoiding generalities, we ha
Page 117 and 118: EA comment:Guidance on the preparat
Page 119 and 120: Please give me a call to discuss wh
Page 121 and 122: RECORD OF MEETINGStatus:JBA Project
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Level 2 Strategic Flood Risk Assessment (.pdf ... - Wigan Council

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