Strategic Flood Risk Assessment - South Worcestershire ...

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Sources of Flood Risk:The main source of flood risk to the site is from surface water. With furtherdevelopment and creation of impermeable surfaces, surface water flooding maybecome a problem. The Drakes Lea road, the main access road to the site is at riskof surface water.This site is shown to be partially within one of the County Council’s historic floodhotspots.Primary fluvial risk is to the western edge of the site resulting from overtopping of theRiver Avon and Evesham Marina. The western edge of the site falls within FloodZone 2 with the majority of the site falling in Flood Zone 1. The western edge of thesite falls within the Blue Zone of the Policy Maps. The Drakes Lea road, the mainaccess road to the site is at risk of fluvial flooding.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 TypeFluvial DepositsGreenfield Runoff Rate (l/s/ha) 1 in 2 year 102012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 112
Estimated Attenuation Storage Volume (m 3 ) 1,292 – 1,789SUDS and the development site:SUDS TypePotentialSuitabilityComments1 in 100 year (plus climate change) 39.4Source ControlInfiltrationDetentionFiltrationConveyanceAll forms of source control are likely to be suitableMapping suggests underlying soil is likely to be permeable.However; the high risk of groundwater flooding would makeinfiltration unsuitableMapping suggests that the site slopes are steep and that detentionstorage ‘above ground’ would not be viableMapping suggests that filtrations would be suitable but require a formof liner to prevent ingress of groundwater into the SUDS systemAll forms of conveyance are likely to be suitableFlood Defences:None.This site is located within a flooding hotspot so all efforts should be made tominimise the rate and volume of runoff leaving the site.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 River Avon.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.Proposed for residential uses.Flood Zone 2 should be used as public open space.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 effectsNew 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 current and only access road to the site, Drakes Lea road, is at risk from fluvialflooding and surface. Suitable alternative access arrangements away from thefloodplain will need to be investigated further.Demonstration that development at this location can be made safe.2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 113
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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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Page 70 and 71: Sources of Flood Risk:Primary flood
Page 72 and 73: emergence. Further assessment of gr
Page 76 and 77: Table 7-10: SWDP6/NEWJ (Land North
Page 78 and 79: Estimated Attenuation Storage Volum
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 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 128 and 129: Surface Water Drainage:As an indica
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 138 and 139: Sources of Flood Risk:The main sour
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 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
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Table 7-39: SWDP25/9 (Land at Park
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access roads to the site are at ris
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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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