Strategic Flood Risk Assessment - South Worcestershire ...

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Sources of Flood Risk:Primary flood risk to the site is fluvial, resulting from overtopping of the unnamedtributaries of the Piddle Brook, to the north of the site. This northern edge of the sitefalls within Flood Zone 3b and the Blue Zone of the Policy Maps. The northernB4082 Snodsbury road, the main access road to the site, is at risk from fluvialflooding.Further development and creation of impermeable surfaces may result in anincrease of surface water flood risk. The northern B4082 Snodsbury road, the mainaccess road to the site is at risk from surface water.Surface Water Drainage:As an indication of requirements to manage surface water runoff at the development site anassessment of the soil types, greenfield runoff rate and attenuation storage volume is includedbelow. Storage volumes displayed are calculated with an assumption that 75% of the site will bedeveloped impermeable ground. A 25% increase in rainfall depths has been included torepresent predicted future climate change effects.PLEASE NOTE: This assessment has been carried out using broad-scale datasets and aims toprovide an indication of the likely opportunities and constraints for this development site. Adetailed drainage assessment based on site-specific conditions should be carried out by asuitably qualified professional and submitted with any planning application. The values belowshould not be used for design purposes.Soil TypeGreenfield Runoff Rate (l/s/ha)Estimated Attenuation Storage Volume (m 3 ) 220 – 310Unknown – Less Permeable1 in 2 year 9.21 in 100 year (plus climate change) 35.52012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 162
SUDS and the development site:SUDS TypeSource ControlInfiltrationDetentionFiltrationConveyancePotentialSuitabilityCommentsAll source control techniques are likely to be suitableMapping suggests underlying soil is unlikely to be permeable. A siteinvestigation should be carried out to assess suitability of drainage byinfiltrationMapping suggests that site slopes may be steep, larger ‘aboveground’ features may not be viableAll filtration techniques are likely to be suitableAll conveyance techniques are likely to be suitableFlood Defences:None.The site is not located within a groundwater source protection zone.Residential developments should provide at least two independent SUDS features inseries to provide a suitable level of water quality treatment.Effects of Climate Change:Increased rainfall intensity. Increased water levels in the unnamed tributary of the CarrantBrook.Flood Risk Implications for Development:All development should be located within Flood Zone 1, unless appropriate inaccordance with NPPF Technical Guidance.A detailed site-specific flood risk assessment, including hazard mapping, will berequired for any development in Flood Zone 2, or for sites greater than 1ha in FloodZone 1.Redevelopment of the side is proposed to focus on residential uses.Resilience measures will be required if buildings are situated in the flood risk area.Green infrastructure should be considered within the mitigation measures for surfacewater runoff from potential development.Assessment for runoff should include allowance for climate change effects.New or re-development should adopt exemplar source control SUDS techniques toreduce the risk of frequent low impact flooding due to post-development runoff.Onsite attenuation schemes would need to be tested against the hydrograph of thereceiving watercourse to ensure flows are not exacerbated downstream within thecatchment.The site falls within an area indicated to potentially be susceptible to groundwateremergence. Further assessment of groundwater risk would be required and anassessment of suitable surface water mitigation techniques should be made at thedetailed FRA level.Access needs would need to be outside of the floodplain, onto the southern branchof the B4632 Station Road and \ or the Green Road.Demonstration that development at this location can be made safe.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 163
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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/
Page 120 and 121: Sources of Flood Risk:The main sour
Page 122 and 123: Table 7-24: SWDP13/4 (Former playin
Page 124 and 125: Surface Water Drainage:As an indica
Page 126 and 127: Table 7-25: SWDP13/5 (Former Recrea
Page 130 and 131: Table 7-26: SWDP13/9 (Land off Mayf
Page 132 and 133: Greenfield Runoff Rate (l/s/ha)Esti
Page 134 and 135: Sources of Flood Risk:Primary flood
Page 136 and 137: eceiving watercourse to ensure flow
Page 140 and 141: Table 7-29: SWDP18/6 Land rear of t
Page 142 and 143: Estimated Attenuation Storage Volum
Page 146 and 147: New or re-development should adopt
Page 150 and 151: Table 7-32: SWDP23/26 (Land between
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
Page 174 and 175: access roads to the site are at ris
Page 176 and 177: Table 7-40: SWDP/VPx (Vale Park ext
Page 180 and 181: 8 FRA requirements for developers8.
Page 182 and 183: Figure 8-1: Rationale for flood res
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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