Strategic Flood Risk Assessment - South Worcestershire ...

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Figure 8-1: Rationale for flood resilient and/or resistant design strategies 2AvoidanceResistance/Resilience**Design waterdepth*Design waterdepth up to 0.3mDesign waterdepth from 0.3mto 0.6mDesign waterdepth above0.6mApproachRemove building/ developmentfrom flood hazardAttempt to keepwater out ‘WaterExclusionStrategy’Attempt to keepwater out, in fullor in part,depending onstructuralassessment. Ifstructuralconcerns existfollow approachto the right***Allow waterthrough propertyto avoid risk ofstructuraldamage.Attempt to keepwater out for lowdepths offlooding ‘WaterEntryStrategy’***MitigationmeasuresLand raising,landscaping,raisedthresholdsMaterials andconstructionswith lowpermeabilityNotes:* Design water depth should be based on assessment of allflood types that can impact on the building** Resistance/resilience measures can be used in conjunctionwith Avoidance measures to minimise overall flood risk*** In all cases the ‘water exclusion strategy’ can be followedfor flood water depths up to 0.3mMaterials withlowpermeability toat least 0.3mFlood resilientmaterials anddesignsAccess to allspaces topermit dryingand cleaningSource: PPS25Practice Guide p118Materials withlowpermeabilityup to 0.3mAccept waterpassagethroughbuilding athigher waterdepthsDesign todrain wateraway afterfloodingAccess to allspaces topermit dryingand cleaning8.6 Sustainable Urban Drainage SystemsSustainable Urban Drainage Systems (SUDS) are management practices which enable surfacewater to be drained in a way which mimics, as closely as possible, the run-off prior to sitedevelopment. The choice of flow management facilities within a single site is heavily influencedby constraints including (but not limited to):TopographyGeology (soil permeability)Available areaFormer site useProposed site useGroundwater conditionsFuture adoption and maintenance possibilities2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 174
The design, construction and ongoing maintenance regime of such a scheme must be carefullydefined, and a clear and comprehensive understanding of the existing catchment hydrologicalprocesses and existing drainage arrangements is essential.For infiltration SUDS techniques it is imperative that the water table is low enough and a sitespecificinfiltration test is undertaken. Where sites lie within or close to groundwater protectionzones or aquifers further restrictions may be applicable, and guidance should be sought from theEnvironment Agency.There are many different SUDS techniques which can be implemented. The suitability of thetechniques will be dictated in part by the development proposal and site conditions. Advice onbest practice is available from the Environment Agency and the Construction Industry Researchand Information Association (CIRIA).SUDS TechniqueTable 8-1: Example SUDS TechniquesFloodReductionWater QualityTreatment &EnhancementLandscapeand WildlifeBenefitLiving roofs Basins and pondsConstructed wetlandsBalancing pondsDetention basinsRetention pondsFilter strips and swales Infiltration devicesSoakawaysInfiltration trenches and basinsPermeable surfaces and filterdrainsGravelled areasSolid paving blocksPorous pavementsTanked systemsOver-sized pipes/tanksStorm cellsThe inclusion of SUDS within developments should be seen as an opportunity to enhanceecological and amenity value, incorporating above ground facilities into the developmentlandscape strategy. SUDS must be considered at the outset, during preparation of the initial siteconceptual layout to ensure that enough land is given to design spaces that will be an asset tothe development rather than an after-thought. The future adoption and maintenance of SUDS,particularly those including swales, basins, ponds or reed beds, should be closely aligned withplans for the management of green infrastructure. The emerging Worcestershire GreenInfrastructure Strategy is being developed by the Worcestershire Green InfrastructurePartnership, which includes the South Worcestershire authorities.Under the Flood and Water Management Act, the SUDS Approval Body will be responsible forapproving, adopting and maintaining drainage plans and SUDS schemes that meet the NationalStandards for sustainable drainage.All new developments will require planning approval from both the SAB and the local planningauthority. The Environment Agency will be a statutory consultee when delivering SUDS for anyproposed discharge of surface water into a watercourse.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 175
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2012s5947 South WorcestershireStrat
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ContractThis Level 2 Strategic Floo
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Executive SummaryThis report is an
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Table 7-16: SWDP8/1 (Broomhall Comm
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NRDOrdinary WatercourseOS NGRPFRAPi
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identify the level of detail requir
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1.4 Approach1.4.1 General Assessmen
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1.5.3 Severn Trent WaterSevern Tren
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2 The Planning Framework and Flood
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Additionally Provision 110 of the A
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Risk ManagementAuthority (RMA)Distr
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3 Understanding Flood Risk in South
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earth embankment, flood wall and fl
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4 How Flood Risk is Assessed4.1 Def
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Zone 1Zone 2Zone 3aZone 3bTable 4-1
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etween the proposed level of commit
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5 Mapping and risk based approach5.
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The ability to manage flood risk fo
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Stage 3 - Applying the Sequential T
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6 Overview of future developmentThe
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A proposed 340 dwelling have been a
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Figure 6-5: Proposed Pershore Alloc
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6.3 Windfall sitesWindfall is unall
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7 Summary assessment of SWDP develo
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SUDS TypeSource ControlsTable 7-2:
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7.4 Summary tables and mapsTable 7-
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SUDS and the development site:SUDS
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Sources of Flood Risk:Primary flood
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Table 7-5: LP1 (Ivy Lane)OS NGR: SP
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Table 7-7: 2012SC (Stonebridge Cros
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emergence. Further assessment of gr
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Table 7-10: SWDP6/NEWJ (Land North
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Estimated Attenuation Storage Volum
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Table 7-12: SWDP6/6 (Old Northwick
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Soil TypeGreenfield Runoff Rate (l/
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Sources of Flood Risk:Surface water
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Table 7-14: SWDP6/21 (Former Hallow
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SUDS and the development siteSUDS T
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Table 7-16: SWDP8/1 (Broomhall Comm
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Surface water presents a risk to th
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Table 7-17: SWDP8/2 (Temple Laugher
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A44 Bromyard road, the A4440 Grove
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Table 7-18: SWDP8/3 (Land to the re
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impermeable surfaces may result in
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Table 7-19: SWDP9/2 (Land east of S
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impermeable surfaces may result in
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Table 7-20: SWDP9/3 (Boxing Club)OS
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Estimated Attenuation Storage Volum
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Table 7-22: SWDP9/7 (Canal Basin Pr
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Soil TypeGreenfield Runoff Rate (l/
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Sources of Flood Risk:The main sour
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Table 7-24: SWDP13/4 (Former playin
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Surface Water Drainage:As an indica
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Table 7-25: SWDP13/5 (Former Recrea
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Surface Water Drainage:As an indica
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Table 7-26: SWDP13/9 (Land off Mayf
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Page 134 and 135: Sources of Flood Risk:Primary flood
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Page 140 and 141: Table 7-29: SWDP18/6 Land rear of t
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Page 150 and 151: Table 7-32: SWDP23/26 (Land between
Page 154 and 155: Sources of Flood Risk:The main sour
Page 156 and 157: Table 7-34: SWDP24/8 (Site behind H
Page 158 and 159: SUDS and the development site:SUDS
Page 162 and 163: Table 7-36: SWDP24/11 (Site behind
Page 164 and 165: overtopping of an unnamed tributary
Page 166 and 167: Table 7-37: SWDP24/13 (Land east of
Page 172 and 173: Table 7-39: SWDP25/9 (Land at Park
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Page 176 and 177: Table 7-40: SWDP/VPx (Vale Park ext
Page 178 and 179: Surface Water Drainage:As an indica
Page 180 and 181: 8 FRA requirements for developers8.
Page 184 and 185: Local planning bodies should:Promot
Page 186 and 187: Temporary BarriersTemporary barrier
Page 188 and 189: flood risk. Development locations s
Page 190 and 191: 9 Recommended policy for management
Page 192 and 193: 10 Outcomes10.1 Summary of work und
Page 194 and 195: Appendices2012s5947 S Worcestershir
Page 196 and 197: AFlood Zone mapping2012s5947 S Worc
Page 198 and 199: BClimate change mapping2012s5947 S
Page 200 and 201: CHazard mapping2012s5947 S Worceste
Page 202 and 203: DSurface water flood risk mapping20
Page 204 and 205: D.2 200 years2012s5947 S Worcesters
Page 206 and 207: EFloodplain policy mapping2012s5947
Page 208 and 209: FSummary of risk to all proposed al
Page 210 and 211: GProperty and critical infrastructu
Page 212 and 213: Number of environmental sites at ri
Page 214 and 215: HConsultation and communication2012
Page 216: Offices atAtherstoneDoncasterEdinbu
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