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

More documents

Recommendations

Info

3.2.3 Flooding from the Leeds Liverpool canal through WiganCanal flooding is an unlikely occurrence and so should be considered to be a residual risk.The locations where canal breach is considered most likely are summarised below:The River Douglas may overtop into the canal during a severe flood event in Wiganwhere the Leeds Liverpool canal crosses the river. However, the aqueduct in thislocation is raised by approximately 6-7 metres above the river level, suggesting therisk of this is low.Risk of blockage of the inlets of the twin siphons that pipe the River Douglas underthe Leeds Liverpool Canal. It should be noted that access to view the upstream faceof the siphons was restricted (no access onto third party land). These siphons havetrash screens on the inlets.The risk of breach of canal embankments causing significant flooding to people orproperty within the area appears low. The most likely flooding risk along the LeedsLiverpool Canal appear to be overtopping of the Leigh branch of the canal into thelow lying areas south of Poolstock. The greatest flood risk appears to be a reoccurrence or similar of the April 2009 eventwhere the opening of sluice gates by third parties caused downstream flooding in thePoolstock Lane area. This scenario could potentially happen at any lock gatesthroughout Wigan.3.2.4 Data availability3.2.4.1 A series of overtopping and breach appraisal have been undertaken at selected locationsalong the canal system in Wigan. This mapping has been provided to the Council in digitalformat. Due to the potentially numerous locations for failure scenarios, the canal mapping isconsidered indicative only and will need to be reviewed and updated as part of any detailedsite specific FRA. The location of breach scenarios were based on the location of elevatedcanal systems and vulnerable infrastructure. The actual risk of failure, at any location, hasnot be assessed in this SFRA2009s0578 Final SFRA with Environment Agency Comments - L2 Ver5 Wigan.doc 21
4 Flooding from ReservoirsFollowing the recommendations of the Pitt Review, DEFRA and the Environment Agencyhave prepared inundation maps (at various levels of detail) of all reservoirs falling within theremit of the Reservoirs Act 1975. These inundation maps show the effects of a dam breachon the downstream area.By December 2010 the Environment Agency website plans to offer a facility to allowmembers of the public to identify whether or not a property is downstream of a reservoir andmay be subject to flooding.This chapter summarises the location of key reservoirs within the Wigan area.4.1 Reservoir locationsThis SFRA was not able to obtain a copy of the Environment Agency Reservoir Register,which identifies those reservoirs under the Reservoirs Act due to “implications for nationalsecurity”.However, discussions with Wigan Council and a review of OS mapping shows there anumber of large reservoirs within or upstream of the borough. Table 4-1 identifies the mainreservoirs and urban areas at risk immediately downstream of them.Explicit consideration of reservoir overtopping and breach should be considered in detailedsite based FRAs where the reservoir is within or in close proximity to the proposeddevelopment. Prior to undertaking an FRA, the Environment Agency should be consulted toconfirm the site specific requirements.Table 4-1: Key ReservoirsReservoir Name Local Authority Downstream AreaAdlington Wigan Council Chorley Road Standish, ThornHill, Marylebone, central Wigan,ScholesArley Wigan Council Chorley Road Standish, ThornHill, Marylebone, centralWigan, ScholesWorthington Wigan Council Chorley road Standish, ThornHill, Marylebone, centralWigan, ScholesWrightington New Pond West Lancashire Appley Bridge, ShevingtonVale, Holland Lees (included asa potential risk to Wigan area)Atherton Lake FSR Wigan Council LeighRivington Lower Chorley / Bolton Adlington (included as apotential risk to Wigan area)2009s0578 Final SFRA with Environment Agency Comments - L2 Ver5 Wigan.doc 22
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: 3.2.2 Canal breach methodologyCanal
Page 31 and 32: direction in Future Water3, Making
Page 33 and 34: oundaries. Nine key CDAs have been
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 79 and 80:
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 89 and 90:
Page 91 and 92:
New SiteReferenceWig 716Wig 706BSit
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Site Reference Site Location Soil T
Page 99 and 100:
F . Flood Zone 3 Proposed Developme
Page 101 and 102:
G . Environment Agency comments on
Page 103 and 104:
Flood Hazard MappingThe Level 2 rep
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
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?