Strategic Flood Risk Assessment - South Worcestershire ...

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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 ) 40 – 60SUDS and the development site:SUDS TypeSource ControlInfiltrationDetentionFiltrationConveyanceFlood Defences:None.PotentialSuitabilityCommentsAlluvial Deposits1 in 2 year 9.61 in 100 year (plus climate change) 37.1Most source control techniques are likely to be suitable. Permeablepaving is unlikely to be suitable due to high risk of groundwaterfloodingMapping suggests underlying soil is likely to be permeable. Howeverthe high risk of groundwater flooding would make infiltrationunsuitableDetention techniques may be suitable if a non-permeable liner isprovided to prevent the ingress of groundwater. Mapping suggeststhat site slopes may be steep so larger features may not be viableFiltration techniques may be suitable if a non-permeable liner isprovided to prevent the ingress of groundwaterAll conveyance techniques are likely to be suitableThe 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 an unnamed tributary of Pool Brook.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.Development of the site 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.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 120
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.All access roads to the site are at risk from both fluvial flooding and surface water.Suitable alternative access arrangements away from the floodplain will need to beinvestigated further.Demonstration that development at this location can be made safe.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 121
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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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Page 80 and 81: Sources of Flood Risk:Primary flood
Page 82 and 83: Table 7-12: SWDP6/6 (Old Northwick
Page 84 and 85: Soil TypeGreenfield Runoff Rate (l/
Page 86 and 87: Sources of Flood Risk:Surface water
Page 88 and 89: Table 7-14: SWDP6/21 (Former Hallow
Page 90 and 91: SUDS and the development siteSUDS T
Page 94 and 95: Table 7-16: SWDP8/1 (Broomhall Comm
Page 96 and 97: Surface water presents a risk to th
Page 98 and 99: Table 7-17: SWDP8/2 (Temple Laugher
Page 100 and 101: A44 Bromyard road, the A4440 Grove
Page 102 and 103: Table 7-18: SWDP8/3 (Land to the re
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Page 106 and 107: Table 7-19: SWDP9/2 (Land east of S
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Page 110 and 111: Table 7-20: SWDP9/3 (Boxing Club)OS
Page 116 and 117: Table 7-22: SWDP9/7 (Canal Basin Pr
Page 118 and 119: 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 136 and 137: eceiving watercourse to ensure flow
Page 140 and 141: Table 7-29: SWDP18/6 Land rear of t
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
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Surface Water Drainage:As an indica
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8 FRA requirements for developers8.
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Figure 8-1: Rationale for flood res
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Local planning bodies should:Promot
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Temporary BarriersTemporary barrier
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flood risk. Development locations s
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9 Recommended policy for management
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10 Outcomes10.1 Summary of work und
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Appendices2012s5947 S Worcestershir
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AFlood Zone mapping2012s5947 S Worc
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BClimate change mapping2012s5947 S
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CHazard mapping2012s5947 S Worceste
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DSurface water flood risk mapping20
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D.2 200 years2012s5947 S Worcesters
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EFloodplain policy mapping2012s5947
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FSummary of risk to all proposed al
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GProperty and critical infrastructu
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Number of environmental sites at ri
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HConsultation and communication2012
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Offices atAtherstoneDoncasterEdinbu
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