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 River Avon.The western edge of the site falls within the historic flood map (Flood Zone 2). Thewestern end of Boat Lane, the main access road to the site, is risk from fluvialflooding.Surface water presents a risk to the site. Further development and creation ofimpermeable surfaces may result in an increase of surface water flood risk. Themain access road, Boat Lane, is at risk of 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)Fluvial DepositsEstimated Attenuation Storage Volume (m 3 ) 1132.2-1568.41 in 2 year 10.01 in 100 year (plus climate change) 39.42012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 50
SUDS and the development site:SUDS TypeSource ControlInfiltrationDetentionFiltrationPotentialSuitabilityCommentsAll source control techniques are likely to be suitableMapping suggests low permeability at this site, site investigationshould be carried out to assess potential for drainage by infiltrationDetention 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 viableAll filtration techniques are likely to be suitableConveyanceFlood Defences:None.All conveyance techniques are likely to be suitableThis 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.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.The site falls within an area highly susceptible to groundwater emergence (>25-50%). An assessment of suitable surface water mitigation techniques should bemade.The main access road to the site, Boat Lane, is at risk from both fluvial flooding andsurface water. Suitable alternative access arrangements away from the floodplainwill need to be investigated further.Demonstration that development at this location can be made safe2012s5947 S Worcestershire Level 2 SFRA Update FINAL Report v1.0.doc 51
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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
Page 10 and 11: Table 7-16: SWDP8/1 (Broomhall Comm
Page 12 and 13: NRDOrdinary WatercourseOS NGRPFRAPi
Page 14 and 15: identify the level of detail requir
Page 16 and 17: 1.4 Approach1.4.1 General Assessmen
Page 18 and 19: 1.5.3 Severn Trent WaterSevern Tren
Page 20 and 21: 2 The Planning Framework and Flood
Page 22 and 23: Additionally Provision 110 of the A
Page 24 and 25: Risk ManagementAuthority (RMA)Distr
Page 26 and 27: 3 Understanding Flood Risk in South
Page 28 and 29: earth embankment, flood wall and fl
Page 30 and 31: 4 How Flood Risk is Assessed4.1 Def
Page 32 and 33: Zone 1Zone 2Zone 3aZone 3bTable 4-1
Page 34 and 35: etween the proposed level of commit
Page 36 and 37: 5 Mapping and risk based approach5.
Page 38 and 39: The ability to manage flood risk fo
Page 40 and 41: Stage 3 - Applying the Sequential T
Page 42 and 43: 6 Overview of future developmentThe
Page 44 and 45: A proposed 340 dwelling have been a
Page 46 and 47: Figure 6-5: Proposed Pershore Alloc
Page 48 and 49: 6.3 Windfall sitesWindfall is unall
Page 50 and 51: 7 Summary assessment of SWDP develo
Page 52 and 53: SUDS TypeSource ControlsTable 7-2:
Page 54 and 55: 7.4 Summary tables and mapsTable 7-
Page 56 and 57: SUDS and the development site:SUDS
Page 60 and 61: Table 7-5: LP1 (Ivy Lane)OS NGR: SP
Page 64 and 65: Sources of Flood Risk:Primary flood
Page 66 and 67: Table 7-7: 2012SC (Stonebridge Cros
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
Page 104 and 105: impermeable surfaces may result in
Page 106 and 107: 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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Sources of Flood Risk:Primary flood
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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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Table 7-26: SWDP13/9 (Land off Mayf
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Greenfield Runoff Rate (l/s/ha)Esti
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eceiving watercourse to ensure flow
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Table 7-29: SWDP18/6 Land rear of t
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New or re-development should adopt
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Table 7-32: SWDP23/26 (Land between
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Table 7-34: SWDP24/8 (Site behind H
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SUDS and the development site:SUDS
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Table 7-36: SWDP24/11 (Site behind
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overtopping of an unnamed tributary
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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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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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